Variables Affecting Ratio Factors for Estimating 305-Day Production from Part Lactations

Abstract

Complete lactations for 12,561 Holsteins, 2,262 Guernseys, 990 Jerseys, and 459 Brown Swiss recorded in Michigan DHIA-IBM from June 1954 through July 1957 were analyzed to ascertain the relative effects of breed, herd, age, parity, and season of freshening on the relationship of total to part milk production, and then were used to derive ratio factors for extending partial records to 305 days.