A large scale retrospective study was undertaken in2005 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.
Proceedings of the New Zealand Society of Animal Production, Volume 66, Napier, 329-333, 2006
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