Effects of non-genetic and crossbreeding factors on daily milk yield of Ayrshire x (Sahiwal x Ankole) cows in Mahwa station (Burundi)

The study was carried out at the Mahwa station located in Bututsi natural region in South of Burundi at 1850 m of altitude. The objective of the study was to assess the effects of days in milk, cow's calving age, type of crossbreeding, year and month of lactation, parity on daily milk yield of crossbreds Ayrshire (AY) x Sahiwal (S) x Ankole (A) cows. Milk yields were obtained from 9 cows (S) that have been both milked and suckled during the entire lactation, on 8 cows (M) only milked during the entire lactation and on 150 cows (SM) suckled before and milked after weaning. Data were analyzed using the procedure GLM in SAS for S,M, and SM cows separately. All factors affected significantly daily milk yields (P < 0.001). Least-squares means (LSM) for daily milk yields were highest at the 8th (7.16 +/- 0.07 1), 8th (7.63 +/- 0.35 1), and 7th (7.34 +/- 0.39 1) day in milk for SM, S and M lactations, respectively. The Wood model was able to detect 2 main groups of curve shape: standard for SM and S cows and atypical decreasing for M cows. An important decrease in milk production was observed around the 120th day in SM cows corresponding to the weaning period. Crossbreeding improved milk production and highest yields were observed with 50% to 75% of Ayrshire inheritance (LSM = 5 +/- 0.05 to 5.51 +/- 0.02 1/day). A significant increase was observed from 1977 to 1992 due to the improvement of genetic and management techniques. During this period, LSM raised from 1.26 +/- 0.11 1 to 4.74 +/- 0.03 1 per day for SM cows. Unfortunately, the 1993 civilian war destabilized the managerial techniques and consequently, the milk production decreased in Mahwa station, In all cows, milk production was significantly higher from December to May (LSM - 3.96 +/- 0.03 1/day) during the rainy season than in September (LSM = 3.12 +/- 0.03 1/day) at the end of the dry season. (C) 2006 Elsevier B.V. All rights reserved