Relationship between central performance test for growth in Hereford bulls and growth and carcass traits of progeny

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Abstract
Four central performance tests of growth in Hereford bulls from about 10 to 19 months of age on pasture were conducted in New Zealand. From the 100 bulls performance tested 63 were representatively sampled, including bulls with high and low performance test rankings, and progeny tested in dairy herds. Crossbred progeny were purchased from the dairy herds at 3 to 4 months of age, assembled in one location and reared together on pasture for 14 to 15 months prior to slaughter. Regressions of progeny growth and carcass traits on a number of different performance traits for growth of their sires were in almost all cases not statistically significant. The effective heritability, from offspring-sire regression, was 0·07 (s.e. 0·05) for final live weight and 009 (s.e. 0·06) for post weaning gain from about 200 to 550 days of age. It is concluded that central performance tests, as presently conducted in New Zealand, are of limited value for ranking breeding values of bulls for growth. Possible reasons for these results are discussed. It is suggested that pre-test environmental effects and age at the start of the central test are critical factors.