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Economics of transition cow management of dairy herds
It is common to observe large among-herd variation in culling risk within 60 DIM. The objective was to assess the effect of two culling risks within 60 DIM (6% vs 12%) on the economic outcomes of dairy herds with the same reproductive performance using an individual cow-based model. For the simulation, two culling risks (6% vs 12%) and two cow sale prices ($1.85 vs $1.37 per kg) were compared using the same reproductive program and performance. Cows were enrolled in an Ovsynch (OVS) preceded by Presynch with 2 injections of PGF 14 d apart, and OVS for resynchronization of open cows at 32 d after AI. Also, cows undergo estrous detection (ED) and AI after first AI, and cows diagnosed open 32 d after AI are resynchronized using OVS. Cows were not inseminated after 365 DIM and open cows were culled after 450 DIM. Culled cows were immediately replaced with primiparous cows. Herd was maintained at 1,000 cows. Mortality was set at 6% and abortion at 11.3%. The dry period and VWP was 60 d. Conception rate to first service was set to 32% (decreased by 2.5% for every subsequent service), and ED was set to 60%. Accuracy of ED and compliance with each injection were set at 95%. Net daily value was calculated by subtracting the costs associated with replacement heifers ($1,600/heifer), feeding costs ($0.25/kg of lactating cow diet; $0.15/kg of dry cow diet), breeding costs ($0.15/cow/d for ED; $2.65/dose PGF; $2.4/dose GnRH; $0.25/injection administration), and other costs ($2.5/d) from the daily income with milk sales ($0.44/kg milk), cow sales ($1.85 or $1.37/kg live weight), and calf sales ($240/calf). Simulation was performed until steady-state was reached (4000 d), then average daily values for the subsequent 1000 d was used to calculate profit ($/yr). According to the model (same herd size, synchronization program, reproductive performance, and feeding costs), the annual profit was $55480 higher for herds with 6% compared to 12% culling risk within 60 DIM. When the cow sale price was $1.37/kg and replacement costs remain the same, the annual profit was $80,300 higher for herds with 6% compared to 12% culling risk within 60 DIM. Early removal of lactating cows from the milking herd affects the bottom line of dairy operations.
Keywords: Culling Risk, Economics, Dairy Herds