Genetic, Environmental and Phenotypic Relationships among Gestation Length, Birth Weight, Growth Traits and Age at First Calving in Beef Cattle

摘要: Data on the Red Angus, Angus and Hereford herds of Pioneer Hi-Bred International, Inc., Des Moines, Iowa, collected from 1968 to 1976, were analyzed for relationships among gestation length, birth weight, prenatal gain (birth weight adjusted length), growth traits age at first calving. A total 5,691 calf records, 1,783 listing included in study. Paternal half-sib analyses least-squares procedures used compute heritability estimates genetic, environmental phenotypic correlations traits. Genetic traits, including gain, high all cases. Heritability length .36 .43, respectively, bull calves .37 .35 heifer calves. between these .25 .22 calves, respectively. Gestation was negatively correlated (genetically) with except weight. This result suggests that faster growing fetuses may trigger parturition earlier than average. Age calving indicating a favorable relationship early reproduction. Analysis several selection indexes combining either yearling or indicated continued response without excessive increase is feasible. Selection moderate would be more effective shorter gestation, suggesting former method both shorten alter curve. Repeatability .20 .22, Maternal effects accounted approximately 10% variation each trait.