@conference {41278,
	title = {CowTrakker technology for improved heat detection},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {61},
	year = {2001},
	month = {Jan},
	pages = {172-175},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Christchurch},
	abstract = {Devices designed to detect motion (CowTrakker{\texttrademark}, Bou-Matic, USA) were attached to Holstein-Friesian cows of either NZ or overseas origin. Animals of each strain either grazed pasture or were fed a total mixed ration. Milk samples were collected twice weekly and progesterone content analysed to identify ovulation events. Cows had tail paint applied from 2 weeks after calving, and were observed twice daily at milking for oestrous activity. Recording continued until 6 weeks after the planned start of mating (PSM). Cows were artificially inseminated following a progesterone-based synchrony programme at PSM. CowTrakker{\texttrademark} data were analysed using four algorithms (T3/1, T3/3, T10/1 and T10/3), which varied according to the period of the rolling average used (3 or 10 days) and the standard deviations from that average (1 or 3). These measurements were related to behavioural observations and the occurrence of ovulation. There was a significant number of false positive events detected by the CowTrakker with all algorithms (sensitivity: 12.3, 46.9, 62.3 and 81.5\%; specificity: 67.1, 88.4, 95.4 and 99.0\%, for T3/1, T3/3, T10/1 and T10/3, respectively) as compared to behavioural observations alone (sensitivity: 71.6\%; specificity: 99.6\%). The CowTrakker{\texttrademark} was a useful heat detection aid, but must be used in conjunction with careful behavioural observations in order to interpret the high proportion of false positive events that are recorded.},
	issn = {1176-5283},
	author = {Verkerk GA and Claycomb RW and Taufa VK and Copeman P and Napper A and Kolver E}
}
@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}
}
