MULTIPLE HERD EVALUATION OF THE EFFECTS OF MATERNAL LINEAGE ON YIELD TRAITS OF HOLSTEIN CATTLE

Effects of maternal lineage on yield traits were examined by using ani mal models. Data were 6054 multiparous records of 2264 cows from six h erds in North Carolina and the breeding herd of Iowa State University. Separate analyses were performed by using first lactation records fro m North Carolina, all records from North Carolina, and pooled records from North Carolina and Iowa. Traits were mature equivalent yields of milk, fat, and protein; percentages bf fat and protein; and milk energ y concentration and yield. Cattle were assigned to maternal lineages o n the basis of the earliest female ancestor recorded. Fixed effects in the models were herd-year-season, parity, and maternal lineage; rando m effects were animal, permanent environment, and residual. All additi ve genetic relationships were considered. For all analyses, maternal l ineage was associated with significant differences in fat percentage a nd milk energy concentration. Differences between maternal lineages fo r yield traits were not significant. Variance components were also obt ained with REML using the same data and models, but with lineage as a random effect. Based on records pooled from Iowa and North Carolina, m aternal lineage accounted for 2.7% of the variance in fat percentage. Otherwise, <1.2% of the variance of any trait was associated with mate rnal lineage.