Growth progeny tests on Angus and Hereford sires under grazing conditions using supervised data collection in many herd–years

Abstract

Records from the progeny of 253 Angus sires and 319 Hereford or Poll Hereford sires have been analysed using reference sires to estimate sire effects within breed for weaning and yearling weight at pasture. Each sire effect is an estimate of the expected progeny difference (EDP); or half of the sire's estimated breeding value. Product-moment correlations among sire effects for Angus (Hereford and Poll Hereford in parentheses) were, for weaning weight x yearling weight 0.74 (0.75), and for post-weaning gain x yearling weight 0.80 (0.76). However, these correlations are influenced by the part-whole nature of the data. The regressions of yearling weight EPD on weaning weight EPD were 1.21 ±0.07 kg. kgt (1.15±0.08). In view of the high correlations, these regressions could be used for predicting yearling weight EPD from weaning data. The correlations between weaning weight and post-weaning gain were 0.19 (0.15). The range of EPDs was wide for both weaning weight, 18.4 kg (25.4), and yearling weight, 29.5 kg (31.6). Thus there is considerable scope for genetic selection among bulls for live weight, based on wide sampling of industry data in New Zealand.

Long-term selection for yearling weight or postweaning gain in Angus cattle

“…Independent estimates of response in the Waikeria herd have been obtained by involvement of selected bulls from the Waikeria, Waihora, and Waikite (AS1) herds alongside industry bulls in an Angus sire reference scheme (Morris & Gibson 1981). Waikeria bulls sampled from calf crops in 1979-81 (actual generation number = 5.45) were compared in the sire reference scheme with late generation Waihora and Waikite bulls (Table 8).…”