Effects of Genotype, Parity, Season and Their Interactions on Milk Yield in Crossbred Dairy Cows

Abstract

The study was conducted to investigate the effects of genotype, parity, season and their interactions on milk yield of the crossbred dairy cows in a dairy farm at Hathazari upazila, Chattogram district, Bangladesh for a period of three years from January 2016 to December, 2019. Cows holding at least individual records of milk yield for subsequent three lactations were selected for the study purpose. Retrospective data representing milk yield of 15 multiparous Holstein-Friesian×Local zebu (Bos indicus) or Sahiwal crossbred dairy cows from the 1st to the 3rd parities were collected from the record sheet of the dairy farm. Results indicated that the genotype, parity, season and their interactions had substantial impacts (p<0.001) on milk yield in the crossbred dairy cows. The herd level highest least squared mean milk yield (N=16,425) was 12.2±0.147 kg/d (CI=11.9-12.4; p≤0.001). Overall, Sahiwal×Friesian1 crossbreds provided highest milk yield (11.9±0.038 kg/day; p<0.001). Maximum average daily milk yield was recorded in the 2nd parity (11.55±0.038 kg/d; CI=11.42-11.69; p<0.001) and minimum in the the 1st parity (10.65±0.038 kg/d; CI=10.53-10.78; p<0.001). Highest milk yield (11.93±0.038 kg/d; CI=11.8-12.0; p<0.001) was recorded in the spring (February-April) followed by the winter (November-January), the summer (March-May) and the fall (September-November) seasons. It was concluded that the milk production was affected by genotypic variability, seasonal changes, parity of the milking cow and their interactions. Changing patterns of milk yield in different seasons and parities could provide scientific evidence for improving feeding strategies to optimize herd level milk yield in the crossbred dairy cows at commercial dairy farms under tropical perspectives.