Type, Body Size and Breeding Efficiency of Ayrshire Cow Families

Abstract

19 Ayrshire cow families were used to determine genetic relationship using analysis of variance to test the significant differences between families, within families, between sires, and between families within sires for type, body size, breeding efficiency and length of service period. The significant difference between families for type and height at withers could be partially attributed to environment and to sires that were used on these cow families. Except for wither height the sire variance was somewhat larger than that attributed to family influence. The error variance explained more than half the total variation in all characteristics. There was a low relationship between members of the same cow family and may account for the drying amount of variance attributed to family differences. It appears that under present breeding practices the genetic variance between families is too small for family selection of type, body size, and breeding efficiency to be very effective.