Submitted to: Journal of Dairy Science
Publication Type: Abstract only
Publication Acceptance Date: 3/23/2004
Publication Date: 7/25/2004
Citation: Yook, E., Pearson, R.E., VanRaden, P.M. 2004. Estimation of the economic impact of a unit change in PTA for daughter pregnancy rate [abstract]. Journal of Dairy Science. 87(Suppl. 1):413. Interpretive Summary:
Technical Abstract: The economic impact of a unit change in PTA of daughter pregnancy rate (DPR) on lifetime profit estimates of a bull's daughters was estimated from DHI records for 71,094 cows to determine an economic weight for the PTAdpr in economic indexes. A cow's relative net income (RNI) was calculated using all production initiated prior to her tenth birthday with milk-fat-protein pricing. The basic RNI function consisted of [total milk, fat, and protein income - feed cost for production] (YI) + [net value of calves + net salvage value] (NYI) - rearing cost (RC) - [(daily cost for labor, maintenance feed, supplies, and fixed expenses) x days in herd] (DC). The basic RNI was augmented (ARNI) by adding the products of sire PTA for various traits and the net income for those traits proposed in the Net Merit calculation but not included in the basic RNI function; specifically, SCS(M), type composites (T), and DPR and daughter calving ease (PRCE). Regression analyses including herd and birth year in the model were used to estimate the simple and partial regressions of ARNI or partitioned ARNI on PTAdpr. Partial regression included all PTAs in Net Merit, except sire calving ease. Each 1% change in PTAdpr increased RNI $23.64 through increasing YI by $90.44 , NYI by $9.15, M by $5.26, T by $2.34, PRCE by $4.51, and DC by $89.04 and decreasing RC $0.98. Thus, ignoring other PTA left a substantial positive impact of PTAdpr. Correspondingly, changing PTAdpr by 1% barely broke even when other PTA were held constant because the loss in YI was greater than the savings in daily cost.