Multiple Herd Evaluation of the Effects of Maternal Lineage on Yield Traits of Holstein Cattle

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Abstract
Effects of maternal lineage on yield traits were examined by using animal models. Data were 6054 multiparous records of 2264 cows from six herds in North Carolina and the breeding herd of Iowa State University. Separate analyses were performed by using first lactation records from 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 of fat and protein; and milk energy concentration and yield. Cattle were assigned to maternal lineages on the basis of the earliest female ancestor recorded. Fixed effects in the models were herd-year-season, parity, and maternal lineage; random effects were animal, permanent environment, and residual. All additive genetic relationships were considered. For all analyses, maternal lineage was associated with significant differences in fat percentage and milk energy concentration. Differences between maternal lineages for yield traits were not significant. Variance components were also obtained with REML using the same data and models, but with lineage as a random effect. Based on records pooled from Iowa and North Carolina, maternal lineage accounted for 2.7% of the variance in fat percentage. Otherwise, < 1.2% of the variance of any trait was associated with maternal lineage.

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