Comparison of methods for predicting total lactation from part-lactation milk yields

Abstract

Ratio, simple regression and modified rregression methods for estimating total lactation based on part-lactation yields were compared. Seven hundred and forty-seven lactation records from Holstein, 1/2 Holstein-Gir and 3/4 Holstein-Gir cows from Santa Mônica Experimental Farm, RJ, from 1965 to 1974, were used. Within genetic groups, means, standard deviations, regression and correlation were obtained, on an intraperiod-season-parity order basis. Errors of prediction by the modified regression method were larger than those by the other two methods. Projecting total yield by simple linear regression method resulted in the smallest average absolute difference between predicted and total yield.