Use of Stochastic Simulation to Evaluate the Reduction in XXXX Emissions and Improvement in Reproductive Efficiency from Routine Hormonal Interventions in Dairy Herds.

@entity577 @entity291 @entity3009
UNASSIGNED: This study predicts the magnitude and between herd variation in changes of @entity577 emissions and production efficiency associated with interventions to improve reproductive efficiency in dairy @entity291 . Data for 10,000 herds of 200 @entity291 were simulated. Probability of conception was predicted daily from the start of the study (parturition) for each @entity291 up to day 300 of lactation. Four scenarios of differing first insemination management were simulated for each herd using the same theoretical @entity291 : A baseline scenario based on breeding from observed oestrus only, synchronisation of oestrus for pre-set first insemination using 2 methods, and a regime using @entity3009 treatments followed by first insemination to observed oestrus. @entity291 that did not conceive to first insemination were re-inseminated following detection of oestrus. For @entity291 that conceived, gestation length was 280 days with cessation of milking 60 days before calving. Those @entity291 not pregnant after 300 days of lactation were culled and replaced by a heifer. Daily milk yield was calculated for 730 days from the start of the study for each @entity291 . Change in mean reproductive and economic outputs were summarised for each herd following the 3 interventions. For each scenario, @entity577 emissions were determined by daily forage dry matter intake, forage quality, and @entity291 replacement risk. Linear regression was used to summarise relationships. In some circumstances improvement in reproductive efficiency using the programmes investigated was associated with reduced cost and @entity577 emissions compared to reliance on detection of oestrus. Efficiency of oestrus detection and the time to commencement of breeding after calving influenced variability in changes in cost and @entity577 emissions. For an average UK herd this was a saving of at least   50 per @entity291 and a 3.6% reduction in @entity577 emissions per L of milk when timing of first insemination was pre-set.
