@conference {41887,
	title = {Bovine viral diarrhoea virus in dairy cattle in New Zealand - studies on its prevalence, biologic and economic impact},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {162-167},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {The majority (>90\%) of dairy cattle will conceive following insemination or natural service, but only about 55\% of cattle calve to any single mating. The majority of losses occur before the time of pregnancy recognition and such cattle are generally detected in oestrus and rebred. However, losses do occur after the period of pregnancy recognition resulting in prolonged duration of open periods and increased probability of culling for infertility. Reasons for loss include genetic abnormalities, infectious agents such as Neospora caninum, bovine viral diarrhoea virus (BVDV), and plant toxicities. The incidence, causes and economic impact of pregnancy loss are poorly defined in New Zealand. In a survey of bulk tank milk, 93\% of 141 dairy herds had >10\% of cows with BVDV antibody. In another study, 602 herds with a high vs. low bulk tank milk (BTM) BVDV antibody concentration were associated with 1.7\% higher annual abortion rates, 2.9d longer calving to conception intervals, 0.04 more services/conception, and 1kg/d reduced solid corrected milk production. Losses due to BVDV were assessed as $90/cow/year in affected herds. It is concluded that pregnancy loss imposes significant economic costs on the New Zealand dairy industry and that BVDV is likely to be major contributing causative agent. Further research is required to evaluate the effects of BVDV on reproduction in dairy herds, the risk factors for the disease and the cost:benefit of control or eradication strategies. },
	issn = {1176-5283},
	author = {Compton CWR and McDougall S and Heuer C}
}
@conference {41925,
	title = {Management and reproductive performance in herds that differed in their induction policies},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {355-359},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {A large scale retrospective study was undertaken in 2005 on the impact of the policies for induction of early calving (either undertaken during study period, stopped in previous 2 seasons, or continuing to induce) and other factors on herd reproductive performance. Data was gathered from whole-herd pregnancy testing data and farm visit records, and electronic records from the LIC database. Data analysed included records from 3 consecutive seasons from 82 herds, and included 34,729 cows, 72,593 calvings, 237,884 individual herd test records and summary pregnancy test results for each herd for 3 seasons. Factors that significantly influenced herd reproductive performance were herd induction policy, season, herd predominant breed, 4 week submission rate, average milk protein percent at herd test within 60 days following the start of the breeding programme, and length of breeding programme (all P< 0.01). Induction usage was found to be declining over time, implemented at a later stage of the calving programme and unlikely to meet Code of Practice requirements, and under-reported to the LIC database. This large-scale epidemiologic study provides important information for herd owners, their advisors, and other scientists on herd reproductive performance. },
	issn = {1176-5283},
	author = {Compton CWR and McDougall S}
}
@conference {41672,
	title = {To induce or not to induce? Insights into important influences on dairy farmer decision making over induced calving},
	booktitle = {Proceedings of the New Zealand Society of Animal Production},
	volume = {66},
	year = {2006},
	month = {Jan},
	pages = {350-354},
	publisher = {New Zealand Society of Animal Production},
	organization = {New Zealand Society of Animal Production},
	address = {Napier},
	abstract = {Between 1998 and 2004 a sire progeny test was run atthe Poukawa Research Farm in Hawke{\textquoteright}s Bay. Four ewe genotypes were used (Romney, East Friesian x Romney, Finn x Romney and Poll Dorset x Romney) with up to 900 ewes mated each year. Datawas collected on 4614 lambs born to 74 rams (an average of 62 progeny per ram). Rams used represented 13 different terminal sire and dual purpose breeds. Ewes were mated using AI or single-sire mated in the paddock for one cycle. Lambs were tagged and weighed within 24 hours of birth. At 12 weeks ofage, lambs were weighed and scanned for eye muscle dimensions from which eye muscle area was estimated. Data were analysed using a REML animal model taking account of repeat matings among parents, genetic relationships among animals and incorporating adjustments for fixed effects associated with year, ewe genotype and litter size. At a mean lambing percentage of 165\%, the mean birth weight across all sires was 4.91 kg and ranged between 4.21 and 5.46 kg for individual sires. The mean 12 week liveweightwas 29.8 kg and ranged from 26.5 to 33.1 kg for progeny from individual rams. There was a wide range in GR fat depth (mean 8.9 mm, sire range 6.9 to 12.3 mm) when corrected to a constant carcass weight of 18.3 kg. The top rams for liveweight were not necessarily top for other characteristics. Significant numbers of lambs are sold store at weaning on a liveweight basis and this makes it possible to place a value on pre-weaning growth. At $2/kgliveweight, the average lamb sired by the top ram for growth would be worth $66.20 and the progeny from the bottom ranked sire would be worth $53 - a difference of $13.20 per lamb. Assuming these rams had an active lifespan of 4 years and mated 80 ewes rearing 125\% per year, each ram would leave 400 progeny. At $13.20 per lamb the difference in value between the top and bottom ranked rams would be $5280. These results show the differences between rams and highlight the importance of using breeding values in the ram selection process.},
	issn = {1176-5283},
	author = {Blackett P and Compton CWR and Glassey C}
}
