@conference {41838,
	title = {Estimation of lactation persistency in crossbred grazing dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {300-305},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Lactation persistency is commonly referred to as the rate of decline in daily yield after the peak of lactation and can be measured in different ways. The objective of this study was to calculate different measures of persistency for milk traits and estimate the correlations between parameters of the lactation curve in crossbred cattle. Herd test records of milk, fat, protein and lactose from 810 first lactation cows were used to obtain individual lactation curves using a mixed model fitting six knots splines. The model included the fixed effects of contemporary group (year-calving week), sire, age at calving (linear and quadratic) and an average spline and the random effect of cow-spline interaction. All cows were in their first lactation, second cross Friesian x Jersey from a crossbreeding experiment established for quantitative trait loci identification. Persistency was measured in three different ways: P1, slope of the line fitted using linear regression of daily yield on day of lactation from day 60 to day 220; P2, the area under the lactation curve from day 121 to 180 divided by the area under the curve from day 1 to 60; and P3, the 240-day lactation yield divided by peak yield multiplied by 240. Correlations between measurements of persistency ranged from 0.24 to 0.81 and were significantly different to zero (P < 0.001). Correlations between lactation yield and measurements of persistency ranged from -0.43 to +0.33 and were significantly different to zero (P < 0.01). These results indicate that measurements of persistency are not invariant and highlight the need to calculate persistency in a more consistent way. When cows were classified for persistency P2 of fat plus protein, cows of high persistency (top 25\%), compared with cows of low persistency (bottom 25\%), had significantly (P < 0.05) more days in milk, higher total yields of milk and its components, lower peak yields, later day of peak yield and lower rate of decline in daily yield from day 60 to day 220 (P1), but similar 240-day total yield of fat and protein. Farming cows of high persistency may be an alternative to reduce farm investments in peak notes and risks of metabolic problems and reproductive failures.
KEYWORDS: lactation persistency; milk yield. },
	issn = {1176-5283},
	author = {Lopez-Villalobos N and Spelman RJ and Harris BL and Stanley G and Harcourt S}
}
@conference {41850,
	title = {Factors affecting methane production in Friesian x Jersey dairy cattle},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {65},
	year = {2005},
	month = {Jan},
	pages = {352-355},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Methane production was measured in 301, 3-year-old Friesian x Jersey dairy cows, during summer 2004 in stage one of a project to define phenotypes for quantitative trait loci (QTL) mapping and to investigate the relationships between CH4 and milk production. Animals were allocated into four groups and their methane production was measured during four days. Feed intake was estimated by the alkane technique and by prediction equations. Correlations between the alkane technique and prediction equations were all less than 0.37, but correlations amongst the prediction equations were greater than 0.61. Daily CH4 output varied from 210 to 498 g and averaged 332 g. Dry matter intake averaged 19.3 g/kg DM. Milk production and live weight gain were negatively related to CH4 production per kg dry matter intake. Sire was not found to have a significant effect on CH4 output per kg of dry matter; however, only six sires are represented in the trial. The CH4 output recorded in the current study was within the ranges observed in other studies and was repeatable between days. High quality data were generated for the QTL study.
KEYWORDS: methane; herbage intake; alkanes; dairy cows. },
	issn = {1176-5283},
	author = {McNaughton LR and Berry DP and Clark H and PinaresPatino C and Harcourt S and Spelman RJ}
}
@conference {41492,
	title = {Effect of dose of Streptococcus uberis infused into the mammary gland of lactating cows on clinical signs, bacterial count, somatic cell count and milk production},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {143-146},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {This study was to evaluate changes in cow productivity and milk value from feeding a rumen-protected form of CLA  to pasture-fed dairy cows in early lactation. 30 New Zealand Friesian dairy cows were randomly assigned at calving to  either 0g (control) or 120g/d of a commercial rumen protected feed containing CLA from 4 days post-calving for 16 weeks.   Milk yield and composition data was collected weekly. A simulation model was used to calculate yield of dairy products  based on accumulated yields of milk and its components per cow during the experimental period.  Feeding CLA reduced  (P<0.001) fat concentration (3.1\% vs 4.2\%) and increased (P<0.05) milk yield (2688 kg vs 2423 kg), and protein yield (89.9  kg vs 81.2 kg).  The effect of CLA on milk fat concentration was reflected in the yield of dairy products and milk value.  Milk from cows fed CLA had less (P<0.01) excess of fat sold as butter (48.4 vs 69.4 kg butter). The value of milk ($/kg  MS) was higher (P<0.001) from cows fed CLA than from control cows at 2002/03 prices ($3.87 vs $3.66) and when butter  price was low ($3.56 vs $3.24).},
	issn = {1176-5283},
	author = {McDougall S and Parker K and Swift S and Harcourt S and Sutherland G}
}
@conference {41480,
	title = {Friesian Jersey crossbred trial: Generating phenotypes for the discovery of quantitative trait loci},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {64},
	year = {2004},
	month = {Jan},
	pages = {92-95},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Hamilton},
	abstract = {The breeding of improved varieties of agriculturally important species requires constant effort and innovation. The ways we in New Zealand use emerging technologies to maintain our low-cost, low-input, sustainable, pastoral agricultural systems are extremely important. When it comes to developing elite varieties and strains of ryegrass we have been, until very recently, disrupting  much to achieve little: we rely on chance to find the right combinations of traits in our breeding lineages, whether animal germplasm or plants cultivars. The use of Cisgenics{\AE}, where heritable material is moved only within a species by either traditional or modern biotechnological means offers a better way for  ryegrass breeding in line with a key principle of science and economics.},
	issn = {1176-5283},
	author = {Spelman RJ and Hooper JD and Stanley G and Kayis SA and Harcourt S}
}
