Effects of Breed, Calving Season and Parity on Milk Yield, Body Weight and Efficiency of Dairy Cows under Subtropical Conditions

摘要

Records of 354 Holstein Friesian (HF) and Brown Swiss (BS) cows born from 1986 to 2006 at Las Margaritas research station, under subtropical conditions of Mexico, were analyzed to estimate milk yield per lactation (MYL, n = 1229), milk yield per day (MYD, n = 1227), milk yield per calving interval (MYCI, n = 929), lactation length (LL, n = 1229), calving weight (CW, n = 1164) and efficiency of milk production (EMP, n = 890). The cows were daughters of 144 sires and 232 dams. Models included breed of cow (2 classes: HF and BS), calving year (22 classes: 1989-2010), calving season (3 classes: cold, from November to February; dry, from March to June; and rainy, from July to October), lactation number (4 classes: 1, 2, 3 and ≥4), linear (except for CW) and quadratic (except for MYD and CW) effect of lactation length and linear effect of calving weight (except for LL). The random effect, other than the error term, was sire of the cow nested within breed of cow. Holstein Friesian cows yielded 261, 0.8 and 0.7 kg more milk per lactation, per day and per calving interval, respectively, than BS cows. In addition, HF cows were more efficient (p0.05). Cows that calved in the cold season had greater (p<0.05) MYD, MYCI and EMP than cows that calved in the dry and rainy seasons. Lactation length was similar among cold, dry and rainy seasons.