Environmental factors affecting morning and evening milk yields in Nili-Ravi buffaloes

Selection of bulls in the recently started progeny testing programs of buffalo requires milk recording on their daughters. As most of the buffaloes under field condition are raised by small farmers, twice a day recording at monthly interval throughout the lactation is very difficult. Attempts are thus being made to reduce the recording duration as well as the frequency of recording. Present study is an attempt to see the effect of environmental factors on the diurnal variation in milk yield. Complete lactations (N=1106) from buffaloes recorded both for morning and evening at a weekly interval from an institutional herd were utilized. The effect of environmental factors like parity, year, season and month of lactation on monthly morning, evening and daily milk yield (three traits) was studied. Two analysis were run using a fixed effect model. In the first analysis, each month of recording was considered as a separate trait for morning, evening, and daily milk yield (11 x 3 analysis). Fixed effects were parity, year, season and year by season interaction. In the second analysis, a monthly total for any stage of lactation was considered as a single trait (3 analyses). Fixed effects, in addition to first analysis, were month of lactation and its interaction with season. Buffaloes produced 6 percent more milk in the morning (1356 kg) as compared to the evening (1191 kg) milking. Lactation milk yield averaged 2.546 kg and was highly correlated both with morning (0.987) and evening (0.985) milk yields. When analyses were run on the 11 monthly totals each for the three traits, season and year-season effects were found significant for the first five months of lactations while milk yield during the later half of the lactation was not affected by season and its interaction with year. Although, results were not consistent for the later half, they were generally non-significant. In the second analysis, all the main effects (year, season, parity and month of calving) had significant effect on the three traits. The two two-way interactions (year by season and month by season) also had a significant effect. Parity and season of calving should be considered in modelling the curve for developing correction factors if lactations are to be projected from partial records of morning or evening milk yields