@conference {69469, title = {Asssociation among hormones and metabolites during the transition period and early lactation milk production}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {70}, year = {2010}, month = {Jun}, pages = {51-56}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {The transition period is loosely defined as the period from three weeks pre-calving to three weeks post calving, and is regarded as a very important determinant of a cow{\textquoteright}s lactation performance. Data were collated from three experiments in which blood was sampled repeatedly pre- and post-calving and milk production was recorded post-calving. Data were pooled within treatment and associations between blood hormones and metabolites, and milk production determined using regression analysis. Milk and milk solids (MS) yield were positively associated (P <0.05) with pre-calving plasma leptin and glucose concentrations and milk yield was negatively associated (P <0.05) with pre-calving non-esterified fatty acid (NEFA) and β-hydroxy butyrate concentrations. Milk yield was negatively associated (P <0.05) with plasma growth hormone, aspartate aminotransferase, and glutamate dehydrogenase concentrations in the first days of lactation, and with insulin like growth factor and glucose concentrations during the first five weeks post-calving. In comparison, plasma NEFA and albumin (ALB) concentrations post-calving and the ratio of NEFA to ALB were all positively associated (P <0.05) with milk and MS yield during the first five weeks of lactation. Data are consistent with a positive effect of calving body condition on milk production and an increased milk production with increasing condition score loss post-calving.}, issn = {1176-5283}, author = {Edwards P and Mandok K and Lee JM and Burke CR and Kolver ES and Roche JR} } @conference {60938, title = {The effect of concentrate supplementation on milk production during an extended lactation in grazing dairy cows : Brief Communication}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {69}, year = {2009}, month = {Jun}, pages = {43-45}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Extended lactation systems where cows are milked for longer than 300 days, provide an opportunity for farmers to use the lactation potential of genetically superior cows, reduce calving and mating costs, even-out labour requirements, and/or build herd size by retaining non-pregnant cows. However, depending upon cow genetic strain and nutrition, milk production can be reduced in an extended lactation system relative to a {\textquoteright}normal{\textquoteright} lactation of 260 to 300 days (Kolver et al., 2007; Grainger et al., 2009). Winter-feeding levels are potentially important... Continued}, issn = {1176-5283}, author = {Phyn CVC and Kay JK and Roach CG and Kolver ES} } @conference {42049, title = {Effect of genotype and concentrate supplementation on dairy product mix and the value of milk produced by grazing dairy cows during an extended lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {68}, year = {2008}, month = {Jan}, pages = {79-83}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Brisbane, Australia}, abstract = {Dairy product mix and milk value were investigated in Holstein-Friesian cows of New Zealand or overseas origin that grazed pasture and were supplemented with 0, 3 or 6 kg DM concentrate/cow/day during a 600-day extended lactation. A dairy product supply chain model was used to predict relative changes in dairy product mix and milk value during the "extended period" (300 to 600 days in milk) compared with the "normal period" (0 to 300 days in milk). Cow genotype and level of concentrate supplement affected dairy product yields, with little consistency of effect between "normal" and "extended" periods. Milk produced during the "extended period" resulted in more cheese, butter, butter milk powder, casein, and whey protein concentrate, but less whole milk powder, skim milk powder and whey milk powder compared to the "normal period". The overseas strain and those cows receiving higher levels of concentrates had less of a decline in whole milk powder yields associated with the "extended period". Milk value ($/L), was predicted to be 20.8\% higher during the "extended period" compared with the "normal period". These results indicate that extended lactations may improve the dairy product mix and milk value following processing. }, issn = {1176-5283}, author = {Turner S-A and Phyn CVC and Kolver ES and Aspin PW and Lopez-Villalobos N} } @conference {42055, title = {Effect of genotype and diet on feed conversion efficiency of dairy cows during a 600-day extended lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {68}, year = {2008}, month = {Jan}, pages = {100-104}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Brisbane, Australia}, abstract = {This study investigated the effect of genotype and diet on the gross feed conversion efficiency (FCE) of cows milked for 600-day extended lactations (24-month season) compared with 300-day lactations (12-month season). North American (NA) and New Zealand (NZ) Holstein-Friesians (HF) grazed pasture and were supplemented with either 0, 3 or 6 kg DM concentrate/cow/day. In a normal 12-month season, gross FCE was greater for NZ HF compared with NA HF cows when fed 0 or 3 kg DM concentrate (96 and 104 vs. 90 and 99 kg milksolids (MS)/t dry matter intake (DMI), respectively), but similar when fed 6 kg DM (101 kg MS/t DMI). However, during an extended 24-month season, NZ HF cows had a lower gross FCE than NA HF when fed 6 kg DM concentrate (86 vs. 99 kg MS/t DMI, respectively) and similar FCE when fed 0 or 3 kg DM (85 and 94 vs. 86 and 99 kg MS/t DMI, respectively). Regardless of diet, gross FCE in an extended lactation was 98\% of that obtained in a normal season for NA HF cows, but only 88\% for NZ HF, indicating that NA HF are better suited to converting feed into high MS production in extended lactations. }, issn = {1176-5283}, author = {Phyn CVC and Clark C and Aspin PW and Kolver ES} } @conference {41738, title = {Evaluation of a model that estimates insulin sensitivity in dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {261-265}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Glucose challenge data was used to model parametersdescribing the dynamics of the glucose-insulin system such as glucose effectiveness (SG), acute insulin response to glucose (AIRg) and insulin sensitivity (SI) in dairy cows. The relationship of these parameterswith post-partum anovulatory interval (PPAI) was also determined. Twenty-five HF cows of New Zealand (NZ; n=13) and Overseas (OS; n=12) origin, were fed either pasture (n=12) or a total mixed ration (TMR; n=13) in a 2x2 factorial design. At two weeks postpartum, they were challenged intravenously with 300 mg of glucose/kg live weight. There was no effect of diet on SG(P=0.302), SI(P=0.17) or AIRg(P=0.093) despite TMR cows of both genotypes having higher values. There was no effect of genotype on SG(P=0.234), SI(P=0.742) or AIRg(P=0.385). Correlations of these parameters with PPAI were not statistically significant: SI (r 2=0.087, P=0.310), SG(r 2 = 0.001, P=0.962) and AIRg(r 2 =0.036, P=0.320). Use of this model demonstrated that insulin response parameters were not closely associated with PPAI.}, issn = {1176-5283}, author = {Back PJ and Boston RC and Palliser CC and Kolver ES and Chagas LM} } @conference {41749, title = {Production and physiological indicators to select cows suitable for extended lactations}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {315-319}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Individual cows vary in their ability to maintain milk production for an extended lactation. Identifying production and physiological markers to indicate cows suitable for extended lactations would allow dairy farmers to make early decisions to withhold mating of individual cows or to continue milking specific nonpregnant cows through the winter months. Fifty-six genetically divergent overseas and New Zealand Holstein Friesians were allocated to three pasture-based dietary treatments (0, 3 and 6 kg concentrate DM/cow/d) and mating was withheld to target a 670-d lactation. Within each treatment there was little correlation between animal evaluation index values and milksolids (MS) production during the extended lactation period (>296 days in milk; DIM). There was a positive correlation between MS yield from the initial normal season (<296 DIM) and extended lactation MS production; and a negative correlation between body condition score (BCS) at theoretical dry off date (~296 DIM) and extended lactation MS yield. Plasma hormone and metabolite data from wk 1-10 postpartum demonstrated a positive association between nonesterified fatty acid levels and extended lactation MS production, whereas glucose,insulin, and insulin like growth factor-1 were negatively associated with extended lactation MS production. Overall, data indicate that the animal evaluation index is not a good indicator of animals suitable for extended lactation, however normal season milk production, early lactation plasmahormone and metabolite and late lactation BCS data may be useful to identify animals that will undergo a successful extended lactation.}, issn = {1176-5283}, author = {Kay JK and Aspin PW and Phyn CVC and Roche JR and Kolver ES} } @conference {41735, title = {Supplemental fumarate has little effect on the detailed composition of bovine milk during early lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {67}, year = {2007}, month = {Jan}, pages = {242-247}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Wanaka}, abstract = {Future farming practices need to be assessed by the dairy industry for any impacts they may have on the detailed composition and processability of milk. These impacts may change the milk price a farmer receives and the milk processability,product range and product quality. The use of sodium fumarate (an organic acid) to reduce methane production from dairy cows has previously been reported. This experiment investigated the effect of intra-ruminal infusions of sodium fumarate on the detailed composition of milk from dairy cows. Fumarate (5\% of daily dry matter intake) was infused into 8 lactating cows while 8 cows received infusions of water as a control. Milksamples were collected during a covariate period, then again following a 16-day treatment period, of which cows were housed indoors for the last 9 days. Gross composition of milk and other production parameters have been presented previously. Milk yield, fat and protein were not affected but lactose concentrations were significantly higher in the milk of cows receiving the fumarate. In the current study, none of the individual casein proteinsmeasured showed an effect of treatment. Of the whey proteins examined, concentrations of α-lactalbumin (α-La) were higher (1.07 vs. 0.98 mg/mL; sed 0.038; P < 0.05) and bovine serum albumin (BSA) concentrations were lower (214.6 vs. 251.0 mg/L; sed 15.1; P < 0.05) in the milk of cows receiving fumarate. None of the individual fatty acids or minerals examined showed a treatment effect. The addition of sodium fumarate to the diet of dairy cows in early lactation does not have a major influence on the composition of milk, suggesting that the product could be used with minimal impact on milk composition and product quality at this early stage of lactation.}, issn = {1176-5283}, author = {Turner S-A and Aspin PW and Kolver ES} } @conference {41652, title = {Effect of genotype and diet on milksolids production, body condition, and reproduction of cows milked continuously for 600 days}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {245-251}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {Milking cows for two consecutive years, with calving and mating occurring every second year, may exploit the superior lactation persistency of high yielding cows while improving reproductive performance. This study tested the feasibility of extended lactations in pastoral systems using divergent dairy cow genotypes (New Zealand [NZ] or Overseas [OS] Holstein-Friesian [HF]) and levels of nutrition (0, 3, or 6 kg concentrate DM/cow/day). Cows calved on 28 July 2003 and remaining cows were dried off by 6 May 2005. Of the 56 cows enrolled, 93\% were milking at 500 days in milk (DIM) and 18\% were milking at 650 DIM. Dietary treatments did not affect DIM (605 {\textpm} 8.3; Mean {\textpm} SEM), but there was a trend (P=0.09) for OS HF to have longer lactations than NZ HF. Genotype x diet interactions were detected for the total yield of milk and milksolids per cow, and as a percentage of liveweight. Differences between genotypes were greatest at the highest level of supplementation. Compared to NZ HF, OS HF produced 35\% more milk, 24\% more milk fat, 25\% more milk protein, and at drying off had 1.9 units less body condition. Annualised milksolids production from NZ HF was 79\% of a normal season{\textquoteright}s production, compared to OS HF that produced 94\%. Compared to NZ cows, OS cows had a similar 21-day submission rate (85\%), a lower 42-day pregnancy rate (56\% vs. 79\%), and a higher final empty rate (30 vs. 3\%) when mated at 451 days after calving. These results indicate that productive extended lactations up to 650 days are biologically possible on a range of pasture diets, and with appropriate cow genetics and feed management may ameliorate poor reproductive performance in high yielding dairy cows without sacrificing milksolids production. }, issn = {1176-5283}, author = {Kolver ES and Roche JR and Burke CR and Aspin PW} } @conference {41935, title = {Plasma insulin, growth hormone, and IGF-1 concentrations of Holstein - Friesian cows of divergent genotype offered varying levels of concentrate in early lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {403-408}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {This study of insulin and key hormones of the somatotropic axis was made to help explain the milksolids and body condition responses obtained from cows of divergent Holstein-Friesian (HF) genotypes fed differing levels of concentrate. Weekly plasma concentrations of insulin, insulin-like growth factor-1 (IGF-1) and growth hormone (GH) were measured from 57 North American (overseas; OS) and New Zealand (NZ) cows in the first 10 weeks of lactation during the 2002/03 and 2003/04 seasons. Cows of similar breeding worth grazed at a high pasture allowance and were individually fed 0, 3 or 6 kg concentrate DM/cow/day. Compared to NZ HF, OS HF had similar insulin concentrations, lower IGF-1 concentrations, and higher GH concentrations. Feeding 3 or 6 kg concentrate DM/day increased insulin and IGF-1 concentrations to a similar extent, with GH concentrations being reduced at the highest level of supplementation. These results are consistent with the previously reported greater loss of body condition in OS HF, and suggest genotype differences in insulin resistance and rate of recoupling of the somatotropic axis after calving. The reported gain in body condition when concentrates were fed is probably a result of the increased insulin production and a positive effect on liver GH receptor 1A, with the consequent increase in IGF-1 and reduction in GH. Diet only began to affect GH concentrations, and therefore body condition loss, after approximately week 4-6 of lactation. These results have implications for feed management and breeding. }, issn = {1176-5283}, author = {Kolver ES and Roche JR and Aspin PW} } @conference {41650, title = {Prevalence of mastitis for cows of different genotypes milked for two consecutive seasons}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {236-240}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {Extending the calving interval from the traditional 12-month to a 24-month calving interval has been suggested as a practical solution for maximizing lactation yield per calving. Somatic cell count (SCC) and the incidence of mastitis were examined in New Zealand (NZ) and overseas (OS) Holstein-Friesian cows fed on pasture alone or supplemented with 3 or 6 kg DM maize/barley concentrates/cow/day during an extended lactation of up to 21 months. Average cow SCC was three-fold higher (P<0.001) in the extended or second season of the lactation compared with the first season, with NZ cows having a slightly higher SCC (P<0.01) in the second season compared to OS cows (191,000 and 115,000 cells/ml respectively). The SCC elevations occurred regardless of infection status of the udder. Although OS cows tended to have twice as many cases of clinical mastitis (P=0.01) in the first season compared to the NZ cows, affecting 59\% and 27\% of cows respectively, there was no difference in infection status between genotypes in the second season (20\% and 18\% respectively). Results showed that although cows experienced less mastitis during the second spring of the lactation, the average cow SCC was higher during the extended part of the lactation. }, issn = {1176-5283}, author = {Lacy-Hulbert SJ and Summers EL and Williamson JH and Aspin PW and Kolver ES} } @conference {41684, title = {Supplemental fumarate did not influence milksolids or methane production from dairy cows fed high quality pasture}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {409-415}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {This experiment tested the hypothesis that methane emissions from dairy cows would be reduced, and milk production increased, when sodium fumarate was added to a diet of fresh pasture at a rate of 5\% of dry matter (DM) intake. Sixteen ruminally fistulated dairy cows (100 {\textpm} 20.7 days in milk; 548 {\textpm} 47.8 kg liveweight; mean {\textpm} SD) received either a control (water) or fumarate treatment (10.3 {\textpm} 1.18 L/cow/day of solution providing 931 {\textpm} 126 g sodium fumarate/cow/day) over a 7-day adjustment period while grazing ryegrass pasture, followed by an 8-day experimental period fed pasture in metabolism stalls. During the experimental period cows on both treatments consumed 18.8 {\textpm} 1.83 kg DM/day, produced 1.81 {\textpm} 0.25 kg milksolids/day, and emitted 350 {\textpm} 44.9 g methane/day (5.9 {\textpm} 0.71\% of gross energy). Total tract DM digestibility was high (78.8 {\textpm} 0.84\%), and ruminal pH was 6.10 {\textpm} 0.15. Fumarate supplementation did not change ruminal fermentation, in vivo digestibility, methane emissions, milk production or composition, or selected plasma metabolites. The opportunity for reducing methane emissions from dairy cows by supplementing with fumarate or breeding high fumarate grasses may be limited for diets of high quality pasture. The limited reports of in vivo response to supplemental fumarate suggest that mitigation opportunities may be greater for pasture diets of low digestibility. }, issn = {1176-5283}, author = {Kolver ES and Aspin PW} } @conference {41937, title = {Supplementation with concentrates either pre- or post-partum does not affect milk production when diets are iso-energetic}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {66}, year = {2006}, month = {Jan}, pages = {416-422}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Napier}, abstract = {Dairy cow glucose requirements increase dramatically during the weeks preceding calving, suggesting that supplements that increase glucose supply (rapidly fermentable carbohydrates) would reduce precalving mobilisation of body tissue and improve subsequent milk production. Sixty-eight multiparous dairy cows were randomly allocated to one of two diets for 36 {\textpm} 8.7 days precalving. All cows were fed pasture and pasture-silage precalving, with one group also receiving 3kg DM of a barley-maize concentrate. Precalving diets were iso-energetic (114 MJ/cow/day). At calving, cows within each precalving feeding treatments were randomly allocated to two dietary treatments for 35 days in a 2x2 factorial arrangement. Postcalving, all cows received pasture and pasture silage with one group also receiving 5.0 kg DM of a barley-maize concentrate. Postcalving diets were also iso-energetic (179 MJ/cow/day). Milk yield and composition, and liveweight (LW) and body condition score (BCS) were assessed weekly for five weeks. Blood was sampled on day -21, -14, -7, 0, 1, 2, 3, 4, 7, 14, 21, 28 and 35 relative to calving, and plasma samples were analysed for indicators of energy status. Average milksolids yield (1.9 kg/cow/d) during the five weeks postcalving was not affected by either pre- or postcalving concentrate supplementation, although protein to fat ratio was higher in supplemented cows. Similarly, concentrate supplementation pre- or postcalving did not affect either LW or BCS change before or after calving. Cows receiving concentrates precalving had higher (P<0.001) plasma non-esterified fatty acid (NEFA) concentrations, but otherwise were not different to those receiving an equivalent energy intake from pasture and pasture silage. Postcalving concentrate supplementation increased (P<0.01) plasma glucose and NEFA and decreased (P<0.001) plasma B-OH butyrate. Results suggests little effect on milk production by replacing energy from structural carbohydrates in high quality pasture with energy from non-structural carbohydrate during the transition period. }, issn = {1176-5283}, author = {Roche JR and Lee JM and Aspin PW and Sheahan AJ and Burke CR and Kolver ES and Sugar B and Napper AR} } @conference {41569, title = {The drinking behaviour of dairy cows in late lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {209-214}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The drinking behaviour of grazing cows was investigated in two studies with the purpose of determining the suitability of using water intake as a motivator for voluntary movement of cows within a pasture-based automatic milking system (AMS). In the first study 100 mixed-age Jersey cows in late lactation were observed for 48 h. Cows drank on average 2.4 times/24 h (range: 1-6) and usually alone or with one or two other animals. Although every cow drank at least twice during the 48 h, 31\% of cows recorded an interval between drinks > 24 h. Less than 1\% of drinking occurred between 2000 h and 0700 h. The second study compared the drinking behaviour of Overseas (OS) and New Zealand (NZ) Holstein Friesian cows that were either grazing pasture (GRASS) or fed a Total Mixed Ration (TMR). TMR cows drank more often (5.2 times/24 h) than GRASS cows (3.5 times/24 h, P < 0.001). Feed type altered the distribution of drinking with 76.8 \% of TMR cows drinking between 2000 h and 0700 h compared with only 24.5\% for GRASS. Water intake was also higher for TMR (73.0 L/cow/day) compared with GRASS (53.7 L/cow/day) animals. The studies showed that the individual nature of drinking behaviour would be aligned with the AMS objectives of distributed rather than batch milking. However, the small number of cows drinking during darkness when grazing indicates that water intake would need to be used in combination with other motivators to ensure a continuous flow of cows to the dairy. KEYWORDS: drinking behaviour; grazing; dairy cows; automatic milking. }, issn = {1176-5283}, author = {Jago JG and Roche JR and Kolver ES and Woolford MW} } @conference {41570, title = {Effects of feeding level for four weeks precalving on milk production is small and dependent on level of feeding in early lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {215-220}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The aim was to quantify the relationship between pre- and postcalving level of feeding and their effect on milk production. Sixty-eight multiparous dairy cows were randomly allocated to two levels of pasture feeding (Low and High; 4.8 and 11.9 kg DM/day) for 29 {\textpm} 7.7 days precalving. At calving, cows were randomly allocated (within precalving levels) to two levels of pasture feeding (Low and High; 8.6 and 13.5 kg DM/day) for 35 days postcalving. Daily milk yields were recorded and fat, protein and lactose concentrations determined on 2 days each week for 5 weeks postcalving, and once weekly for an additional 10 weeks post treatment. Body condition score (BCS) at calving was 4.2 and 4.7 for precalving Low and High treatment groups, respectively. Precalving restriction reduced milk fat production by 8.4\% during the first five weeks postcalving, but these differences were not evident subsequently. Postcalving feed restriction reduced yields of milk, fat and protein by 25, 21 and 28\%, respectively, during the first five weeks postcalving. Decreased (P < 0.05) yields of milk, fat and protein (12, 10 and 9\%, respectively) were also evident for ten weeks after the feed restriction finished. There was a trend towards a treatment interaction (P = 0.13) in milksolids (MS) production during the first five weeks of lactation between pre- and postcalving level of feeding. High- High cows produced 7.1 kg more MS than Low-High cows, but there was no effect of precalving level of feeding in cows that were restricted postcalving. Results confirm that level of feeding postcalving influences the milk production effect of precalving feeding. Nevertheless the effect of precalving energy intake on postcalving milk production is small. KEYWORDS: transition cow; pasture; dry matter intake. }, issn = {1176-5283}, author = {Roche JR and Kolver ES and Lee JM and Aspin PW and Burke CR and Taylor P and Napper AR} } @conference {41535, title = {Influence of dairy cow genotype on milksolids, body condition and reproduction response to concentrate supplementation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {65}, year = {2005}, month = {Jan}, pages = {46-52}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Responses to supplementary feeding overseas (OS) and New Zealand (NZ) Holstein-Friesian (HF) cows were investigated over two years using 57 cows receiving a high pasture allowance and 0, 3 or 6 kg concentrate DM/cow/day. Cows of similar Breeding Worth ($BW) grazed as a single herd and were individually fed a grain-based supplement. Important production genotype x diet interactions of a scaling nature were detected. Across all supplementation levels, OS cows gave a greater (P < 0.05) linear production response than NZ cows (74 vs 37 g MS/kg concentrate DM; 1.22 vs 0.67 kg milk/kg concentrate DM consumed, respectively), but gave a similar response in live weight and condition score gain during lactation per kg of concentrate DM consumed. However, because OS HF appeared to have a larger relative feed deficit than NZ HF when fed ad libitum on pasture, OS HF maintained a lower body condition score throughout lactation and produced less milksolids (as a \% of live weight). Current supplementary feeding decision rules which recommend reducing supplementary feed use when abundant pasture is available remain appropriate for high $BW NZ HF cows. However, reasonable responses to high-energy supplements will continue to be obtained from high $BW OS HF cows, even when pasture supply appears adequate to meet cow requirements. Use of indicators of relative feed deficit such as milksolids as a \% of live weight and body condition score, may be a better guide to predicting the production response to supplementation, rather than decision rules based on genotype. KEYWORDS: Holstein-Friesian; genotype; supplements. }, issn = {1176-5283}, author = {Kolver ES and Roche JR and Burke CR and Aspin PW} } @conference {41510, title = {Effect of precalving feeding level on the milk production of grazing dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {227-231}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Fifty-two multiparous dairy cows were allocated to four treatments with an apparent daily intake of 5.8, 8.9, 10.0 or 11.2 kg dry matter (DM)/cow/day of pasture for 27{\textpm}9.6 days precalving. This equated to 1.3, 2.0. 2.3 and 2.6\% of liveweight (not including the conceptus weight; LW). Following calving, all cows were fed generously on pasture. Daily milk yields were recorded postcalving and fat, protein and lactose concentrations determined on 2 days each week for 5 weeks. Blood was sampled 17 days precalving, on the day of calving and on days 1, 2, 3, 4, 7, 14, 28 and 35 postcalving. Precalving plasma concentrations of insulin-like growth factor-1 (IGF-1) increased (P<0.05) quadratically with increasing pasture intake. Concentrations of growth hormone declined (P<0.05) linearly and concentrations of non- esterified fatty acids declined (P<0.001) quadratically with increasing DM intake. Plasma concentrations of these metabolites postcalving showed no effect of precalving feeding. Level of feeding precalving did not affect milk yield or the yield of fat, protein or lactose in milk, but postcalving DM intake was negatively (P<0.1) related to precalving DMI. These results indicate that 0.93 MJ metabolisable energy/kg LW0.75 was required in the final three weeks of gestation to maintain cow energy balance. }, issn = {1176-5283}, author = {Roche JR and Kay JK and Kolver ES and Aspin PW and Lee J and Sugar B and Napper AR} } @conference {41495, title = {Fumarate reduces methane production from pasture fermented in continuous culture}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {64}, year = {2004}, month = {Jan}, pages = {155-159}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {This experiment tested the hypothesis that addition of an organic acid (fumarate) would increase the energy captured from a pasture diet during ruminal fermentation. Pasture was fermented with 0, 10, 20, or 30 mM of fumarate constantly infused into four dual-flow continuous culture fermenters. Digestion characteristics responded linearly (P<0.05) as fumarate increased from 0 to 30 mM. Increasing fumarate from 0 to 30 mM reduced (P=0.057) methane production by 38\%, and reduced the ratio of acetate:propionate (2.4 v.s. 1.5). Concentrations of propionate and total volatile fatty acids increased by 74\% and 19\%, respectively. These results were consistent with fumarate acting as an electron-accepting intermediary in the succinate-propionate pathway. The addition of fumarate increased energy capture from a pasture diet by improving the supply of glucogenic compounds and reducing losses to methane emissions. }, issn = {1176-5283}, author = {Kolver ES and Aspin PW and Jarvis GN and Elborough KM and Roche JR} } @conference {41420, title = {Diet and genotype affect feeding behaviour of Holstein-Friesian dairy cows during late lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {63}, year = {2003}, month = {Jan}, pages = {124-127}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Queenstown}, abstract = {Ingestive behaviour of New Zealand (NZ) and overseas (OS) Holstein-Friesian (HF) dairy cows grazing pasture only or fed a total mixed ration (TMR) was observed in late lactation. Data from visual observations every 10 minutes over a 48-h period were used to evaluate differences in time spent feeding, ruminating, standing and lying. OS HF and cows fed TMR had greater dry matter intakes (DMI) than their respective comparisons. Cows grazing pasture spent more time feeding, less time ruminating, less time standing and the same time lying, compared to cows fed TMR. OS HF spent less time feeding, the same time ruminating, the same time standing, and more time lying compared to NZ HF. When expressed in terms of DMI, OS HF took less time to consume a kg of DM, and spent less time ruminating each kg of DM compared to NZ HF, irrespective of diet. A genotype x diet interaction was observed for time spent standing, with NZ HF spending more time standing when fed TMR, but standing for a similar time as OS HF when grazing. These results suggest feeding and grazing behaviour differences between HF cows of differing genotype, but similar breeding worth. }, issn = {1176-5283}, author = {Thorne PL and Jago JG and Kolver ES and Roche JR} } @conference {41412, title = {Diet and genotype affect milk lactoferrin concentrations in late lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {63}, year = {2003}, month = {Jan}, pages = {87-90}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Queenstown}, abstract = {Although lactoferrin (Lf) is a valued milk protein, little information is available on factors that affect its concentration in milk. Milk samples were collected during late lactation to determine if diet or cow genotype affected the concentration and yield of Lf in bovine milk. Holstein-Friesian (HF) cows (n=52) of either overseas (OS) or New Zealand (NZ) ancestry were fed either an all-pasture diet or a total mixed ration (TMR). Milk samples were collected from each cow during an AM milking in early March and late April. NZHF had a higher (P<0.05) Lf concentration than OSHF even though they produced less (P<0.05) milk. Genotype did not affect Lf yield, somatic cell count or the proportion of bacteriologically negative quarters. The Lf concentration in the milk of cows fed TMR was higher (P<0.05) than cows grazing pasture in April but not in March. Cows fed TMR also produced more (P<0.05) milk and a greater (P<0.001) yield of Lf than cows grazing pasture. Diet did not affect SCC, however only cows fed TMR had any bacteriologically positive quarters. A positive within-cow correlation (P<0.001) was found between Lf and SCC. The effect of diet on the concentration of Lf in milk requires further investigation. The genotype results suggest that NZHF have higher concentrations of Lf in milk than OSHF. Naturally high concentrations allow improved extraction efficiencies of Lf during processing. }, issn = {1176-5283}, author = {Turner S-A and Williamson JH and Thomson NA and Roche JR and Kolver ES} } @conference {41399, title = {Metabolic responses to glucose challenge in New Zealand and overseas Holstein-Friesian dairy cows}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {63}, year = {2003}, month = {Jan}, pages = {31-34}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Queenstown}, abstract = {North American and Dutch Holstein-Friesian (HF) cattle have undergone genetic selection for increased milk production, however, at the same time, reproductive efficiency has decreased. Overseas HF also have greater propensity to mobilise body reserves during early lactation than New Zealand HF cows. It is possible that reproductive differences are a consequence of metabolic and endocrine differences between the strains. This trial was designed to investigate effects of genotype and diet on endocrine response to a challenge of intravenous glucose in HF cows. Twenty-five HF cows of New Zealand (NZ; n=13) and Overseas (OS; n=12) origin, were fed either pasture (Grass; n=12) or a total mixed ration (TMR; n=13) in a 2x2 factorial design. At two weeks postpartum, they were challenged with 300mg of glucose/kg live weight. Data were analysed for effects of genotype and diet. Following glucose challenge, the NZ TMR cows had higher plasma insulin concentrations than the NZ Grass, resulting in a significant interaction between diet and genotype in the area under the response curve; but the OS groups had similar patterns. Mean plasma leptin concentration was higher in NZ TMR than in NZ Grass, OS TMR or OS Grass. Plasma concentrations of glucose and IGF-I were not affected by genotype or feed regime. These results demonstrated metabolic differences between the strains and also diets. A better understanding of the genetic and nutritional basis of hormonal regulation of nutrient partitioning will be important to develop nutritional strategies to meet the requirements of lactating cows with different genotypes, and to find ways to improve reproductive efficiency. }, issn = {1176-5283}, author = {Chagas LM and Clark BA and Rhodes FM and Blache D and Kolver ES and Verkerk GA} } @conference {41415, title = {Ranking maize hybrids for silage quality and milk production in pasture-based dairying}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {63}, year = {2003}, month = {Jan}, pages = {101-106}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Queenstown}, abstract = {A large database (n=1611) of maize hybrid nutritive characteristics was developed by sampling 42 maize hybrids from three replicate plots at 100 Pioneer Research sites during 2000, 2001, and 2002. Compared to changes from year to year, differences in nutritive quality across hybrids of different maturity were small. Differences in maize hybrid quality accounted for $34 extra milk income per tonne of maize silage DM, whereas the differences in hybrid yield had a much larger impact on milk income ($8672/ha maize grown). Maize hybrids were ranked similarly for milk production potential, although the rankings were much closer, and sometimes equal for hybrids when fed in a New Zealand pasture system compared to a US total-mixed-ration system. Being able to select maize silage hybrids in New Zealand based on the extra milk they are likely to produce will be of benefit to dairy farmers, especially as inclusion rates of maize silage increase.}, issn = {1176-5283}, author = {Kolver ES and Densley R and Miller D and Williams I and Sapienza DA} } @conference {41359, title = {Concentrations of conjugated linoleic acid in milk from cows grazing pasture of fed a total mixed ration for an entire lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {240-241}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {

Conjugated linoleic acid (CLA) is a collective term for the range of conjugated isomers of linoleic acid (C182). These fatty acids occur naturally in milkfat and have proven anticarcinogenic properties in laboratory rodents (Ip et al., 1999). Additionally, the various isomers have other reputed benefits for human health such as enhanced bone mineralisation, antidiabetic effects, reduced atherosclerosis and immune system modulation (Whigham et al., 2000). Such potential benefits for human health have focussed international research on enhancing concentrations of CLA in milk and dairy products. Overseas data show that one way to increase the concentrations of CLA in milk is to change the diet of cows from a typical total mixed ration (TMR) to pasture (Kelly et al., 1998; White et al., 2001). This points to a potential competitive advantage for the New Zealand dairy industry, in which pasture is already almost the sole source of feed. Despite this there are no data confirming the beneficial effects of pasture for enhancing CLA under New Zealand grazing conditions. The experiment described here used an existing experiment to compare the concentrations of CLA in milk from cows fed TMR or grazing pasture for an entire lactation under New Zealand conditions.

}, issn = {1176-5283}, author = {Audlist MJ and Kay JK and Thomson NA and Napper AR and Kolver ES} } @conference {41360, title = {Effect of a Total Mixed Ration diet on the concentration of amino acid-derived volatiles in milk}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {242-245}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {

The flavour chemistry of milk from Holstein-Friesian cows of two genotypes fed total mixed rations (TMR) or pasture has been compared over three years. Mean concentrations of selected milk aroma compounds, namely skatole, indole, dimethylsulphide, toluene, and of total p-cresol (determined after hydrolysis of conjugates) were significantly lower (10\% to 39\% of pasture treatment, P \< 0.01) in the milk from the TMR-fed cows. Mean milk non-protein nitrogen (NPN) and dietary crude protein content (CP) were lower (93\% and 67\% of pasture treatment respectively) for the TMR diet. These results are consistent with an origin for these aroma compounds in the degradation of dietary protein amino acids in the rumen. However, concentrations of total m-cresol, which is not thought to derive from dietary protein, were also lower in the milk from TMR-fed cows (19\% of pasture treatment). In addition, for the pasture treatment, the patterns of variation of concentrations of skatole, indole and p-cresol and NPN in milk and of dietary CP differed considerably between different periods within a dairy season. These findings indicate that factors additional to CP supply are important in the metabolism of these flavour compounds.

}, issn = {1176-5283}, author = {Lane GA and Fraser K and Kolver ES and Rowan DD and Allen JM and Mills OE and Abraham AS and Olney SD} } @conference {41306, title = {Incidence of mastitis among cows of different genogtypes in differing nutritional environments}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {24-29}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {Over three seasons (1998, 1999 and 2000) groups of Holstein-Friesian cows of New Zealand (NZ) or overseas (OS) origin were monitored for mastitis when managed in two contrasting systems. Cows were fed either on pasture or total mixed ration (TMR) with cows on TMR confined to small loafing paddocks or a concrete feedpad. All quarters were sampled for bacteriology at calving, at dry off, in mid and late lactation and when clinical mastitis was detected. Individual cow somatic cell counts (SCC) were determined weekly throughout lactation. In 1998, there was no difference in incidence of clinical mastitis but in later seasons, cows on TMR experienced significantly more clinical, and sub-clinical mastitis, than cows on pasture, probably reflecting differences in bacterial challenge within the environment. Genotype differences were less evident compared to dietary effects. Compared to NZ cows, OS cows experienced more sub-clinical infections in 1998 and more clinical infections in 1999 whilst in 2000, genotype effects were confounded by diet. Seasonal SCC was higher for OS cows in 1999 and 2000, reflecting differences in incidence of sub-clinical mastitis among treatment groups. Despite the strong influence of environment on mastitis incidence, genotype differences were detectable between NZ and OS cows. }, issn = {1176-5283}, author = {Lacy-Hulbert SJ and Kolver ES and Williamson JH and Napper AR} } @conference {41362, title = {Pasture versus total mixed ration during the periparturient period}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {252-256}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {

The effect of diet and genotype on metabolic indicators of energy status in the periparturient cow were investigated. Fifty-six dairy cows of two different genotypes (Overseas Holstein-Friesian (OSHF) and New Zealand Holstein-Friesian (NZHF)) were randomly allocated to two dietary regimens. Half of each genotype group received a pasture/pasture silage diet pre-calving and a pasture diet post-calving, while the other half received a total mixed ration (TMR) pre- and post-calving. Compared with NZHF, OSHF had higher concentrations of plasma non-esterified fatty acids (NEFA; P\<0.05) and glutamic acid dehydrogenase (GDH; P=0.09), an indicator of liver fat infiltration, 30 d post-calving. Genotype did not affect the concentration of either b-hydroxybutyrate (BHBA) or glucose in plasma. Cows grazing pasture pre-calving had greater (P\<0.05) BHBA concentrations, but plasma NEFA concentration and liveweight loss during the first 30 days of lactation were not different. In summary, a pre-calving TMR did not appear to improve the metabolic energy status of the cow pre-calving. These results suggest that provided sufficient nutrients are supplied in the diet, the homeorhetic mechanisms within the cow allow adaption to very different diets. This implies that an all-forage diet pre-calving is sufficient for dairy cows fed forage post-calving.

}, issn = {1176-5283}, author = {Roche JR and Kolver ES and Napper AR} } @conference {41361, title = {Total mixed rations versus pasture diets: Evidence for a genotype x diet on the concentration of amino acid-derived volatiles in milk}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {62}, year = {2002}, month = {Jan}, pages = {246-251}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Palmerston North}, abstract = {

The performance of overseas (OS) and New Zealand (NZ) Holstein Friesian (HF) dairy cows were compared on an all-pasture diet (Grass) or a total mixed ration (TMR). Dietary treatments had been imposed for two years prior to the 2000/2001 season for which these results are reported. The four treatments were NZ Grass (n=14); OS Grass (n=13); NZ TMR (n=14); and OS TMR (n=14). Genotype x diet interactions were observed for annual milk yield, milksolids yield, efficiency of milksolids production, liveweight gain during lactation, and the proportion of cows not in calf. Measurement of individual cow intake using alkane markers during early, mid, and late lactation identified when these genotype x diet interactions occurred. When fed TMR, OS HF performed better than NZ HF, but on grass NZ HF performed better than OS HF. This has implications for the selection of sires for the national herd, and for the use of different dairy cow genotypes in different dairying systems.

}, issn = {1176-5283}, author = {Kolver ES and Roche JR and de Veth MJ and Thorne PL and Napper AR} } @conference {41277, title = {Diet and genotype affect plasma calcium, magnesium and phosphorus concentrations in the periparturient cow}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {168-171}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {The literature is inconsistent with regard to the effect of diet in the periparturient period on the health and production of dairy cows, and there is little or no data on the effect of genotype. Fifty-six dairy cows of two different genotypes (Overseas Holstein-Friesian (OSHF) and New Zealand Holstein-Friesian (NZHF)) were randomly allocated to two dietary regimens. Half of each genotype group received a pasture/pasture silage diet pre-calving and a pasture diet post-calving, while the other half received a total mixed ration pre- and post-calving. Cows receiving the total mixed ration pre-calving had a lower (P<0.05) plasma calcium concentration on the day of calving and the day following calving. Conversely, cows of both genotypes offered pasture had lower (P<0.01) plasma magnesium and phosphorus concentrations pre- and post-calving compared with cows fed a total mixed ration. OSHF cows had lower plasma calcium (P<0.05) and magnesium (P<0.001) concentrations post-calving. Plasma phosphorus concentrations were unaffected by genotype. Herds with a high proportion of OSHF genetics are at an increased risk of parturient hypocalcaemia and hypomagnesaemia. Recommended daily allowances for these minerals may need to be increased to allow for this predisposition.}, issn = {1176-5283}, author = {Roche JR and Kolver ES and de Veth MJ and Napper A} } @conference {41243, title = {Lipolytic response of New Zealand and overseas Holstein-Friesian dairy cows challenged with epinephrine}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {48-51}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Sixteen New Zealand Holstein-Friesians (NZ HF) and 15 overseas HF (OS HF) grazing pasture or fed a total mixed ration (TMR) were subjected to an epinephrine challenge during early lactation. A genotype x diet interaction trend (P=0.10) was observed; when grazing, OS HF displayed the greatest glycerol response, with the reverse occurring on TMR. No genotype or diet differences were observed for the glycerol or non-esterified fatty acid response. Dairy cows of both genotypes fed TMR produced a glucose response 31\% greater than both genotypes grazing pasture. These preliminary results suggest that genotype x diet-induced differences in the rate of lipolysis may occur in Holstein-Friesians during early lactation. These differences may be a function of small differences in energy balance. Feeding TMR was associated with a greater glucogenic response to epinephrine, which probably resulted from greater hepatic reserves of glycogen or simply a greater energy demand by the mammary gland. }, issn = {1176-5283}, author = {Kolver ES and Roche JR and de Veth MJ and Mackle TR} } @conference {41295, title = {Modelling the impact of nutrition and genotype on lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {237-238}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Dairy cows grazed on pasture experience variation in their nutritional status during lactation, as both pasture quality and availability vary seasonally. This has both immediate and long-term consequences on cow performance. Acute effects of nutrition are related to availability of nutrients for milk secretion, and are manifested in day-to-day variation in milk yields. Of further importance are the chronic effects of nutrition, which act on the development of the mammary gland, impacting on the persistency of lactation. Typically, cows in a New Zealand, pasture-grazing environment exhibit a decline in milk yield of around 10\% per month, after peak lactation, whereas cows fed a concentrate diet in Northern Hemisphere systems show declines of less than 4\%. Post-peak declines in milk yield are associated with a proportional and permanent decline in the number of secretory cells in the udder, and this decline is modulated by nutrition (Davis et al., 2000). Quantifying the milk-yield response of a cow to different nutritional regimes is useful from a breeding and selection point of view, but on its own does not give insight into which pathways are likely to be affected by nutrition, nor does it explain the origin of differences in responses between cows. To this end, mechanistic mathematical models that reflect the underlying biology of the udder are particularly useful. }, issn = {1176-5283}, author = {Davis SR and Vetharaniam I and Upsdell M and Kolver ES and Pleasants AB} } @conference {41244, title = {Monitoring adrenal activity in dairy cows under various feeding regimens using faecal glucocorticoid metabolites}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {52-55}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Adrenal activity in cattle can be measured by changes in plasma glucocorticoid concentrations. Cows treated with synthetic adrenocorticotrophic hormone (ACTH) to stimulate the adrenal cortex exhibited elevated plasma cortisol concentrations for 4-5h. Concentrations of faecal glucocorticoid metabolites (FGM) peaked between 8-9.5h after ACTH treatment, 2.5 fold higher than basal (P<0.05) and remained elevated for 13h (range, 11.1-16.1h). Faecal glucocorticoid concentrations were monitored in two strains of Holstein Friesian (HF) dairy cows farmed in New Zealand under two systems: NZ pastoral and North American concentrate-based. The overseas (OS) and New Zealand (NZ) HF were fed a pasture-based diet (Grass) or a total mixed ration (TMR) throughout lactation. Faecal samples were collected on four occasions during lactation. Faecal glucocorticoid concentrations of the cows fed Grass were consistently higher (P<0.05) than cows fed TMR. There was also a significant genotype effect; FGM concentrations of the NZ HF cows were higher than OS HF cows (P<0.05). In a separate study, no obvious trends were evident in FGM in NZ HF grazing pasture at three stocking rates (2.2, 3.2, 4.3 cows per hectare). Measuring FGM can be used to monitor acute adrenal activity in cows, but is more difficult to interpret as a measure of chronic stress. }, issn = {1176-5283}, author = {Morrow CJ and Kolver ES and MacDonald KA and Verkerk GA and Matthews LR} } @conference {41297, title = {Prediction of ruminal pH of dairy cows fed pasture}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {61}, year = {2001}, month = {Jan}, pages = {241-243}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Christchurch}, abstract = {Rumen pH as low as 5.6 has been reported in cows fed highly digestible pasture, however, incidences of sub-acute acidosis have not been well documented and there are no easy or reliable means for farmers to measure ruminal pH. This study collated animal and dietary parameters (81 treatment means), from 20 studies of lactating dairy cows fed pasture, to evaluate the relationship between ruminal pH and animal parameters, and identify suitable predictors of ruminal pH. Mean ruminal pH (5.6-6.7) was negatively correlated (P<0.05) with total volatile fatty acid concentration, milk yield, microbial N flow from the rumen, milk protein yield, milk fat yield, total non-structural carbohydrate content and acid detergent fibre content of the diet. No single dietary parameter, or group of parameters, was able to adequately predict ruminal pH. The increase in microbial nitrogen flow, milk, and milk fat production as ruminal pH decreased below 6.2 suggested that the performance of cows fed high quality pasture was not limited when mean ruminal pH decreased to 5.8. This implies that dairy cows fed pasture can tolerate a lower ruminal pH before sub-acute acidosis occurs than when forage-concentrate diets are fed. }, issn = {1176-5283}, author = {de Veth MJ and Kolver ES} } @conference {41212, title = {A comparison New Zealand and overseas Holstein Friesian heifers}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {265-269}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The performance of overseas (OS) and New Zealand (NZ) Holstein Friesian (HF) dairy heifers was compared when fed an all-pasture diet (Grass) or a total mixed ration (TMR) throughout lactation. The four treatments were NZ Grass (n=14); OS Grass (n=9); NZ TMR (n=15); and OS TMR (n=10). Compared with NZ HF, OS HF had a higher live weight and produced more milk, but milksolids yield, efficiency of milksolids production, and persistency of lactation were not different. Compared with HF fed Grass, HF fed TMR produced more milk and milksolids, were more efficient, had a greater persistency of lactation, and ended lactation with a greater body weight. The OS HF genotype was unable to maintain acceptable body condition and live weight on an all-grass diet. This raises serious questions regarding the sustainability and suitability of these genetics for seasonal all-pasture dairying systems. }, issn = {1176-5283}, author = {Kolver ES and Napper AR and Copeman PJA and Muller LD} } @conference {41213, title = {Comparison of selected reproductive characteristics in Overseas and New Zealand Holstein-Friesian cows grazing pasture or fed a total mixed ration}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {270-274}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {Lactating overseas and NZ-derived Holstein-Friesian cows were fed either pasture or total mixed ration (NZGrass, n=14; NZ TMR, n=14; OSGrass, n=12; OS TMR, n=13). For cows ovulating before breeding began, mean postpartum anoestrous intervals (PPAI) were 39{\textpm}6, 29{\textpm}4, 27{\textpm}6 and 23{\textpm}2 d, respectively. Of 13 cows with PPAI 43d, four were NZGrass (P<0.02). Of seven with PPAI >43d, four were NZGrass (P<0.05). Growth of the first dominant follicle and corpus luteum through time, and day of emergence of the second follicle wave, measured by transrectal ultrasonography, did not differ between treatment groups. Feeding system affected mean plasma progesterone concentration at emergence of the second follicle wave and number of subordinate follicles recorded during the first follicle wave (4.5 {\textpm} 0.4 and 6.1 {\textpm} 0.5 ng/ml, P<0.02; 6.2 {\textpm} 0.6 and 4.1 {\textpm} 0.7 follicles/d, P<0.05; for grass and TMR, respectively). In summary, both genotype and feed system affected length of PPAI, while feed system influenced aspects of peripheral hormone profiles. }, issn = {1176-5283}, author = {Verkerk GA and Morgan S and Kolver ES} } @conference {41214, title = {Effects of diet on udder function and regression in Holstein-Friesian Cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {275-276}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The rate of decline in milk yield after peak lactation is about 10\% per month, for cows in New Zealand grazing pasture diets, and less than 4\% per month in concentrate-fed animals in northern hemisphere environments. Much of the decline in milk yield after peak lactation is associated with a similar proportional loss of secretory cells from the udder and, once lost, these cells cannot be replaced until the dry period before the next lactation. Thus, we have found (unpublished data) that from peak lactation (October) to late-lactation in New Zealand, there was a loss of over 50\% of mammary DNA. Such a loss was also reflected in changes in udder volume (Davis et al., 1985) and also in changes in milk storage capacity in the udder (Davis et al., 1987). Differences in lactational persistency between concentrate and pasture-fed animals suggest that nutrition exerts a long-term effect on milk production through maintenance of mammary secretory cell structures, as well as function. In the present experiment, our hypothesis was that cows fed concentrate diets would maintain milk production better than cows fed pasture over the summer months and that this would be reflected in the functional udder capacity (FUC). FUC is a measure of mammary cell numbers and is highly correlated with milk production (Davis et al., 1987). Further work attempted to correlate changes in FUC with concentrations of blood hormones sensitive to diet. }, issn = {1176-5283}, author = {Davis SR and Farr VC and Auldist MJ and Kolver ES} } @conference {41147, title = {Formulating total mixed rations from forages - defining the digestion kinetics of contrasting species}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {9-14}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The work described here is the first step in formulating forage-based TMR rations for dairy cows, based on digestion kinetics derived from in vitro and in sacco incubations. Kinetic information has been obtained from 23 contrasting fresh and conserved forages species, including temperate and tropical grass species, legumes (including Lotus spp. containing condensed tannins), herbs, silages, lucerne hay and maize grain. All forages were minced to a particle size similar to chewed material. Estimates of DM solubility (\% DM) and fractional dry matter degradation rates (h-1) determined by in sacco incubations include: white clover (39\%, 0.195), perennial ryegrass (45\%, 0.114), tall fescue (46.8\%, 0.051), paspalum (27\%, 0.068), sulla (51.4\%, 0.121), chicory (41.8\%, 0.260), pasture silage (41\%, 0.083), maize silage (28\%, 0.042). In vitro incubations resulted in five-fold differences between forages in net ammonia release, 2-3 fold differences in volatile fatty acid yield and a three-fold difference in acetate:propionate ratio. The data will be used in simulation models to identify optimal forage mixtures for meeting the nutritional needs of high-producing dairy cows. }, issn = {1176-5283}, author = {Burke JL and Waghorn GC and Brookes IM and Attwood GT and Kolver ES} } @conference {41201, title = {Urinary cortisol: An indicator of stress in dairy cattle}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {60}, year = {2000}, month = {Jan}, pages = {218-221}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, address = {Hamilton}, abstract = {The measurement of immunoreactive urinary corticosteroids was validated as a method of monitoring adrenocortical activity in lactating dairy cows. The physiological relevance of the technique was validated by demonstrating that (i) injection of ACTH led to a significant increase in plasma and urinary corticosteroid concentrations, and (ii) the translocation of cows from pasture to a barn facility resulted in a 1.1- to 2.5-fold increase in urinary cortisol concentrations. Plasma cortisol concentrations exhibited a 15- to 33-fold increase above basal concentrations 30 mins after ACTH administration (2.98{\textpm}0.35 vs 63.7{\textpm}3.9 ng/ml plasma; mean{\textpm}SEM; P<0.01). Monitoring urinary corticosteroid concentrations is a valid tool for studying and evaluating adrenal activity and acute stress in cattle. }, issn = {1176-5283}, author = {Morrow CJ and Kolver ES and Verkerk GA and Matthews LR} } @conference {41114, title = {Amino acid supply to the small intestine of dairy cows fed pasture}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {180-183}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Two experiments measured the quantity and quality of amino acids available for absorption by four dairy cows fed pasture. Experiment 1 compared a diet of ryegrass/white clover pasture offered ad libitum or at 75\% of ad libitum intake during October. Experiment 2, conducted in December, compared an all-ryegrass diet with a diet comprising 100\% ryegrass, or 50\% ryegrass and 50\% white clover. Treatments were assigned according to a 2x2 crossover design. Restricted feeding (Experiment 1) significantly reduced the total supply of amino acids to the small intestine by 23\% (246 vs. 190g amino acid nitrogen/d). Compared to an all-ryegrass diet, a ryegrass diet which contained 50\% white clover (Experiment 2) significantly increased the total supply of amino acids by 10\% (284 vs. 259g amino acid nitrogen/d). For all four pasture diets, arginine, methionine, and histidine were identified, in that order, as being most limiting, supplying 67, 71, and 77\%, respectively, of the absorbable amino acid requirement. The supply of absorbable lysine from all four pasture diets was found to meet requirements of dairy cows in early to mid lactation. }, issn = {1176-5283}, author = {Kolver ES and Carruthers VR and Neil PG and de Veth MJ and Jansen EBL and Phipps DE} } @conference {41075, title = {Pasture digestion in response to changes in ruminal pH}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {59}, year = {1999}, month = {Jan}, pages = {66-69}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Four continuous culture fermenters were used to determine the ruminal pH required for the optimal digestion of pasture. Spring pasture was fermented at four controlled levels of ruminal pH (5.4, 5.8, 6.2 and 6.6) according to a 4x4 Latin square design. Decreasing pH from 6.6 to 5.4 reduced dry matter digestion by 14\%, neutral detergent fibre digestion by 11\%, total non-structural carbohydrate digestion by 5\% and microbial nitrogen flow by 18\%. A quadratic relationship was observed between ruminal pH and the true ruminal digestibility of dry matter (R{\texttwosuperior}=0.94, SE=2.06) and microbial nitrogen flow (R{\texttwosuperior}=0.66, SE=0.05). The ruminal digestibility of pasture dry matter was optimised at pH 6.35, and synthesis of microbial protein was optimised at pH 6.13. This experiment indicated that digestion was largely insensitive to pH across a broad range of pH (5.8 to 6.6), but that a large reduction in digestion occurred when mean pH was less than 5.8. }, issn = {1176-5283}, author = {de Veth MJ and Kolver ES} } @conference {41001, title = {Balancing pasture and maize silage diets for dairy cows using urea, soybean meal or fishmeal}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {102-105}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Four treatment groups of 10 Holstein-Friesian cows were established at the DRC No. 2 dairy in the spring, summer and autumn of 1996/97 to test the efficacy of providing urea, soybean meal or fishmeal supplement to overcome the protein deficiency that occurs when cows are supplemented with large amounts of maize silage. Pasture allowance was manipulated to achieve an average pasture dry matter (DM) intake of 6.6kg/cow/day for each group. Treatment groups were supplemented with 75 MJ ME/cow/day as either 7.0kg DM of maize silage, 7.0kg DM of maize silage plus 90g of urea, 5.2kg DM of maize silage plus 1.4kg DM of soybean meal, or 5.8kg DM of maize silage plus 1.0kg DM of fish meal. The addition of urea as a source of non-protein nitrogen had no effect on milk, milkfat or milk protein production. Soybean meal increased milk protein production by 0.06kg/cow/day in both summer and autumn (P<0.01). Fishmeal increased milkfat production by 0.07 (P<0.01) and 0.08kg/cow/day (P<0.05) in summer and autumn and increased milk protein by 0.06 (P<0.01), 0.10 (P<0.01) and 0.08kg/cow/day (P<0.001) in spring, summer and autumn, respectively.}, issn = {1176-5283}, author = {MacDonald KA and Penno JW and Kolver ES and Carter WAC and Lancaster JAS} } @conference {41002, title = {Ruminal utilisation of pasture nitrogen in response to increased level of dietary starch inclusion}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {58}, year = {1998}, month = {Jan}, pages = {106-109}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Four diets based on high quality pasture were formulated using additions of starch to contain 12.8, 19.6, 26.3, or 33\% total nonstructural carbohydrate and were evaluated using four continuous culture fermenters during four 10 day periods. The true ruminal digestibility of organic matter was not changed by diet but the digestibility of neutral detergent fibre and crude protein linearly decreased, and the digestibility of total nonstructural carbohydrate linearly increased, as the level of starch inclusion increased. Production of NH3 N was reduced linearly from 35.2 to 14.2 mg/dl (P<0.001) and the flow of non-NH3 N as a proportion of total N flow increased linearly from 66\% to 83\% (P<0.001) as inclusion of starch increased. The quantity of microbial N and non-NH3 N flowing from continuous culture was unchanged. The experiment indicated that if the amount of organic matter digested is not appreciably increased by the inclusion of nonstructural carbohydrate then the linear increase in ruminal utilisation of pasture N arises more from a reduced pasture N intake than an improvement in microbial protein synthesis.}, issn = {1176-5283}, author = {Kolver ES and Muller LD and Varga GA} } @conference {40828, title = {Evaluation of the Cornell Net Carbohydrate and Protein System for dairy cows fed pasture-based diets}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {56}, year = {1996}, month = {Jan}, pages = {251-254}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {This study evaluated the Cornell Net Carbohydrate and Protein System (CNCPS) for dairy cattle consuming pasture-based diets. Data was obtained from four grazing, and four indoor pasture feeding experiments (23 dietary treatments) with dairy cattle in New Zealand and the United States. ME requirements for maintenance were adjusted to account for grazing activity. The model gave a reasonably good prediction of changes in condition score (R2=0.79, slope not significantly different from 1), energy balance (R2=0.76, slope not significantly different from 1), blood urea nitrogen (BUN) (R2=0.91, underprediction bias of 0.4\%), microbial nitrogen flow (R2=0.83, slope not significantly different from 1), and milk production. The model underpredicted DM intake (R2=0.80, 11\% bias), and overpredicted ruminal pH (R2=0.47, 1.8\% bias). These results indicate that the CNCPS can be used to make realistic predictions of ruminal fermentation and performance of dairy cows offered good quality pasture.}, issn = {1176-5283}, author = {Kolver ES and Barry MC and Penno JW and Muller LD} } @conference {40460, title = {Short term changes in selected metabolites in pasture fed dairy cows during peak lactation}, booktitle = {Proceedings of the New Zealand Society of Animal Production}, volume = {53}, year = {1993}, month = {Jan}, pages = {77-82}, publisher = {New Zealand Society of Animal Production}, organization = {New Zealand Society of Animal Production}, abstract = {Computer-based decision support systems could provide an effective mechanism to facilitate technology transfer to farmers, and also improve the quality of their management decisions. The developers of computer systems, therefore, need to be cognisant of the constraints faced by farmers and the management methods that they use. To assist with the development of an expert system for the drying off decision a mail survey of 250 seasonal supply dairy farmers in five regions of New Zealand was undertaken during the 1992 winter to obtain information on management practices and decision aids used on farms. A response rate of 70\% was achieved. Most (69\%) farmers dried off some cows before drying off the main herd on the basis of age and condition. Final drying off date was most often based on pasture availability, cow conditions and/or the availability of supplements (85\%). Mean pasture cover targets at drying off ranged from 1606 kg DM/ha in Northland to 2129 kg DM/ha in South Taranaki. Most farmers expected pasture cover to increase between drying off and calving. Only 22\% of the farmers formally prepared a feed budget. A condition score target at drying off was given by 56\% of the respondents (of which only 40\% used a 1-10 scale). Computers were owned by 19\% of the surveyed farmers. Inexperience with computers (60\%), the cost of hardware (40\%), lack of time to learn how to use computers (34\%), no interest in computers (27\%) and the belief that computers could not help management (27\%) were cited as reasons for not owning a computer. The survey results indicate that computer-based decision support systems should be targeted initially at consultants who could provide a "bureau" type service to individual farmers. The present low level of formal feed budgeting limits the utility of decision-support systems that require objective farm data for developing grazing management recommendations.}, issn = {1176-5283}, author = {Kolver ES and Macmillan KL} }