The Evaluation of paternal half-sib heritabilities and genetic, environmental and phenotypic correlation estimates for randomly selected Hereford cattle

Growth and carcass data collected over 10 years at the USDA-ARS, Fort Keogh Livestock and Range Research Laboratory in Miles City, Montana from a Hereford herd selected at random were analyzed with the paternal half-sib intraclass correlation procedure.The objective was to compare the genetic parameter estimates from this random selection study with estimates from selection studies in the literature.All males were maintained intact and only males were included in the data set.Calves were born in the spring and raised under eastern Montana range conditions.Weaning took place in mid-October, and after an adjustment period calves were started on a 168-d feed trial.Bulls were slaughtered between 14 and 17 months of age.Fixed effects included in the mixed model were calf year of birth, age of dam, and calf age as a covariate.Random effects were sire, replication, and residual.Sires were selected at random and all cow culling was done at random.The data were subdivided into three subgroups.The first group included all male progeny that had recorded birth weights.The second group included bulls with complete records for the growth traits.The third group included progeny with complete carcass and growth records.The heritability estimate for birth weight from 736 progeny from 86 sires was .18±.10.The second group included 616 bull progeny from 85 sires and heritability estimates were as follows: weaning weight, .17±.11; daily gain from birth to weaning, .20±.12; final test weight, .42±.14; and daily gain on test, .47±.14.The third group included 401 records from 75 sires and heritability estimates were as follows: carcass weight, .38±.18; ribeye area, .51±.19; marbling, .31±.17; slaughter weight, .42±.18; ribeye area/unit of carcass weight, .23±.16; and dressing percentage, .25±.17.Genetic, environmental, and phenotypic correlations were also estimated.Genetic correlations were higher in magnitude compared to the literature estimates for comparisons among the growth traits.Genetic correlations comparing lean meat yielding traits to fat composition traits were lower in magnitude with slight positive relationships.Phenotypic and environmental correlations were in good agreement with the literature reviewed, Thus, estimates of genetic parameters from this nonselected herd were in general agreement with estimates in the literature from selected herds.