Interactions of sires with feeding and management factors in Illinois Holstein cows

Components of phenotypic variation in milk yield from interactions between sires and several feeding and management factors were estimated. Milk yield data were first lactation records. Feeding and management data from Illinois Holstein Dairy Herd Improvement herds were obtained by questionnaires. Sire-herd interaction component was 10% of phenotypic variance in milk yield. Components of variance from interaction between sires and three feeding and management factors, namely, source of roughage for milking herd during summer, amount of grain fed to heifers between 12 and 18 mo age, and amount of grain fed to heifers during 2 mo before calving were negative. Interaction between sires and ideal weight for breeding heifers accounted for 3% of phenotypic variation in milk yield.