The Department of Lands and Survey (LS) introduced an objective-based, open nucleus Angus breeding program in 1976 to produce bulls for its commercial properties. Previously, commercial sires were purchased from numerous industry sources (IND). To demonstrate the usefulness of objective selection and to determine performance differences between the two sire sources, 600 mature Angus cows and heifer replacements were randomly mated to either LS or IND bulls beginning in 1976. Replacement female offspring from these matings were then randomly mated to either LS or IND bulls to produce second generation offspring (GEN2). Herd size was maintained and matings continued through 1986. Growth performance of all GEN2 animals was recorded through weaning. After weaning, only female performance was recorded. Least-squares methodology was used to determine differences between the two genetic sources (IND or LS). Traits measured were weaning weight (WW); cow ratio, calf weaning weight per 100 kg of cow weight (CR); yearling weight (YW); and 18 month weight (18M). The statistical model for all traits included year of birth (YOB), sire source of calf (CSS) and dam (DSS), sex (where applicable), age of dam (AOD), age at weighing, and the interactions of YOB and CSS, YOB and DSS, AOD and CSS, AOD and DSS, and CSS and DSS. Calf`s sire source was significant (P<.01) for WW and CR, and approached significance for YW (P<.1) but was not significant for 18M (P>.1). Dam`s sire source was not significant for any trait (P>.1) nor was the interaction of CSS and DSS (P>.1). The WW of progeny with LS maternal grandsires and LS sires was 4.6±1.8 kg greater than progeny with IND sires and IND maternal grandsires. Differences in weights taken subsequently were smaller. Although not statistically important, in a production scenario where all male progeny were sold at weaning, benefits of the introduction of an objective-based, breeding scheme were evident.
Proceedings of the New Zealand Society of Animal Production, Volume 57, , 12-14, 1997
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