Body measurements as selection criteria for growth in South African hereford cattle
Abstract. Birth weight (BW), weaning weight (WW), yearling weight (YW) and seven body measurements (cannon bone length at birth (CB); hip height at weaning (HHW); hip height at yearling (HHY); body length at weaning (BLW); body length at yearling (BLY); scrotum circumference at weaning (SCW) and scrotum circumference at yearling (SCY), measured in a Hereford stud (1497 animals) over a period of 19 years, were used in estimating genetic (co)variances, heritabilities and correlations. Nine different multitrait animal model evaluations were carried out whereby (co)variance components were estimated using the REML VCE 3.0 package. Estimates from different evaluations were pooled, weighing each estimate by the inverse of the sampling variance to calculate weighted mean variance ratios among the different traits. Generally, structural traits tended to have lower heritability estimates (CB = 0.24; HHW = 0.28; HHY = 0.33; BLW = 0.22; BLY= 0.14 ) when compared with literature values , while estimates for production traits compared well with estimates reported for the South African National Evaluation. Weights and linear body measurements were positively correlated (0.4−0.9). Negative correlations were found for scrotum, circumference at weaning and yearling with BW and CB respectively. SCW and BW: −0.54; SCY and BW: −0.65; SCW and CB: −0.66; SCY and CB: −.58. It is concluded that CB could serve as an early indicator of mature size and weights at different ages.