Genetic parameters for body weight, scrotal circumference, and serving capacity in beef cattle

Abstract

Data from a large Hereford bull breeding herd in South Canterbury, New Zealand, were analysed to estimate genetic parameters for liveweights and three reproductive traits. The records comprised yearling weight (YW) in both sexes, 18-month (final) weight (FW) on bulls, scrotal circumference (SC), and serving capacity of bulls recorded in two ways, first as the number of serves in a standard time (serving number, SN), and second as a grade (serving grade, SG). There were 8 years of data available (1982–89 calf crops), comprising 2414 YW records from both sexes (progeny of 63 sires) and 1090 and 923 SC and SN records respectively. Restricted maximum likelihood (REML) procedures were applied to each trait, with a numerator-relationship matrix to incorporate pedigrees of paternal grand-sires. Univariate heritability estimates were 0.17 ± 0.06 (YW), 0.21 ± 0.09 (FW), 0.36 ± 0.13 (SC), 0.15 ± 0.07 (SN), and 0.14 ± 0.07 (SG). Phenotypic and genetic correlations were about 0.5 between liveweights (YW or FW) and SC. Phenotypic correlations were about 0.2 between liveweights and SN or SG, whereas genetic correlations ranged from 0.28 to 0.47. There were no significant genetic correlations between SC and SN or SG. The two measures of serving capacity were genetically equivalent, with a genetic correlation of 0.99 ± 0.03.

Keywords:

• body weight
• scrotal circumference
• serving capacity
• heritability
• beef cattle
• Hereford