GENETIC SELECTION DIFFERENTIALS IN ARGENTINE HOLSTEIN DAIRY CATTLE

Genetic selection in dairy cattle has resulted in consistent improvement of productivity worldwide. In contrast, milk production in Argentina has remained fairly stable over the last 20 yrs. The objective of this study was to determine realized genetic selection differentials (SD) in the Argentine Holstein population using the four-path model (sires of bulls, SB; sires of cows, SC; dams of bulls, DB; and dams of cows, DC). Records of 814,886 cows and 12,094 bulls born between 1980-2016 were provided by the Argentine Holstein Breeders Association. The data analyzed consisted of genetic evaluations (HTP; February 2019) for milk yield (MY), fat yield (FY), protein yield (PY), daughter pregnancy rate (DPR),feet and legs (FL), stature (S), rump (R), mammary system (MS) and final score (FS). Estimated SD were averaged by birth year of offspring. Clear declines were observed in SD in yield traits (MY, FY and PY) for SB and SC paths, while the DB and DC paths showed no clear trends. However, it is important to recognize that SD of yield traits for the three more influential paths were all positive for much of analyzed period. SD of most type traits did not show a clear trend except for DC, which was mostly below zero in the period studied. DPR was the only trait with increasing trends in SD for SB, SC and DB, however the SD were mainly negative for these three paths from 1990 to 2015. Results suggest a deficient use of animals with high genetic merit in the local population and this could be one of the factors contributing to the lack of progress noticed in the local dairy industry.