Effects of Non-Genetic Factors on Daily Milk Yield of Friesian Cows in Mahwa Station (South Burundi)

Abstract

From 1991 to 2003, 75,650 daily milk records from 111 Friesian cows maintained at Mahwa station in Burundi were used to study the effects of the lactation length, age at calving, year and month of lactation, and parity on daily milk yield (DMY). Data were analyzed by the GLM procedure in SAS. All factors affected DMY significantly (p < 0.001). The overall average was 8.71 L/d. The peak milk yield of 11.48 ± 0.20 L/d occurred at the 15^th day in milk on the lactation curve. The estimated linear (L/month) and quadratic (L/month²) regression coefficients for age at calving (in months) were –0.26 and 0.0052 in first parity, 0.49 and –0.0056 in second parity, and –0.22 and 0.0013 in third parity and above, respectively. Milk production decreased according to the year of lactation with the highest decrease in 1993. The minimum milk production was observed in 1995 with 6.91 ± 0.17 L/d and the maximum in 1991 with 15.55 ± 0.45 L/d. Milk production was significantly higher in February (9.75 ± 0.13 L/d) in the middle of the rainy season than in September (7.60 ± 0.13 L/d) at the end of the dry season. Least-squares means for DMY for first, second, and third lactations and above were 11.47 ± 0.30, 5.23 ± 0.09 and 10.11 ± 0.06 L/d, respectively.