Abstract

The objective of this study was to develop a genetic evaluation model for farm profitability in a seasonally calving pasture-based dairy herd in Uruguay using crossbred cows. Total lactation yields of milk (MILK), fat (FAT) and protein (PROT) were calculated for each cow-lactation using the test-interval method. Somatic cell score (SCS) was calculated as the average of log2 (somatic cell count) for each cow-lactation. Mating records were used to calculate days from start of mating to conception (SMCO). Cow live weight (LWT) was recorded once per lactation. Cows were scored annually for udder depth (UD), udder support (US), front and rear teat placement (FT and RT). In total there were 4,081 lactations from 2,371 cows recorded from 2015 to 2017. The cows were the progeny of 97 sires. Breeding values (BV) for MILK, FAT, PROT, LWT, SMCO, SCS, UD, US, FT and RT were estimated with a multi-trait repeatability animal model that included the fixed effects of contemporary group (year-lactation number) and deviation from median calving date, and the random effects of animal, cow permanent and residual error. Estimates of BVs for these traits were combined in a selection index to rank cows for farm profitability. The index was calculated as I= –0.074×BVMILK +2.13×BVFAT +7.25×BVPROT –1.48×BVLWT –3.60×BVSMCO –36.84×BVSCS +30.86×BVUD +19.67×BVUS +21.10×BVFT +20.07×BVRT. The index has been used to select the best cows as mothers of future replacements, cull the cows with the lowest selection index value, and for the selection and culling of heifer replacements. Keywords: genetic evaluation; genetic parameters; selection index; Uruguay

D, Laborde, and N Lopez-villalobos

New Zealand Journal of Animal Science and Production, Volume 80, Online, 55-59, 2020