Estimation of 305-day yield from total milk yields in Bunaji and Friesian-Bunaji crosses
Lactation data of 207 cows comprising of 91 Bunaji and 116 Friesian-Bunaji crosses milking for over 305 days were analysed on the basis of average daily yield (ADY), actual 305-day yield (A305), total yield (1Y) and lactation length (LL). The objective was to fit a suitable equation that would estimate 305- dny yield from 1Y nnd to develop estimation fact01·s. The linear regression equations for estimating 305-day yield from TY are Y = 1895.229 + 0.804 TY (R2 = 0.971) and Y = 366.176 + 0.775 IT (R2 = 0.827) for Bunaji and Friesian-Bunaji cows respectively. Various combinations of 1Y, ADY and LL were used in multiple regressions to estimate 305-day yield with R2 values of over 90%. Factors for the estimation of 305-day yield from cows lactating for periods between 305 to 350 days were developed from the fitted equations.
Key words: Total milk yield: 305-day yield; Regression equations; Multiplicative factors; Bunaji; Friesian-Bunaji crosses.