Inductions are an animal welfare issue and regulations aim to achieve < 2% inductions on a national basis by 2010. There is a need to assess the longer-term impacts of alternative reproduction management strategies on farm economics and their success in solving the problem of poor reproductive performance. Dexcel’s Whole Farm Model was calibrated against observed data from Lincoln University Dairy Farm where 11% of the herd was subjected to inductions in the 2002/03 season, but a zero-induction policy has since been adopted. Results from one-year simulations over five different climate years showed a significant decrease in farm profit ($105/ha, P < 0.05) from the benchmark farm with 11% inductions (following ‘best practice’ guidelines) to a farm where the late-calvers were culled and replaced by bought-in early-calving heifers and where stocking rate was raised moderately (< 10%) to compensate for the higher proportion of heifers in the herd. Multiple-year simulations reflecting carry-over effects showed that a strategy with a 10-week mating period, annual culling of 25% of the herd including all empties and replacement with synchronized heifers mated to start calving one week before planned start of calving can match the farm profitability of the ‘Induction’ strategy if implemented consistently for 5-8 years. Key words: calving spread; modelling; synchrony; mating; replacement.

PC, Beukes, BS Thorrold, ME Wastney, CB Glassey, CR Burke, and AM Van Bysterveldt

Proceedings of the New Zealand Society of Animal Production, Volume 65, Christchurch, 132-136, 2005
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