Differences in Milk and Butterfat Production and Test of Ayrshire Cow Families

Abstract

19 cow families in the Reymann Memorial Ayrshire Herd at the W. Virginia Agric. Expt. Station were analyzed for differences between families in milk production, butterfat production, and butterfat test. The first available lactation record was used for each animal. The analysis of variance showed that differences between families were significant for the 3 production figures studied. Sire differences which include yearly variations were largely responsible for these cow family differences. The avg. genetic relationship between members of the same cow family was 15%. Three methods of family selection were compared with selection on individual performance as a means of obtaining improvement in the milk production of the herd. Individual selection was superior to selecting females on a family basis. Family selection alone did not appear to be as effective as selection based on a combination of individual and family merit.