J. Anim Sci.
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J. Anim Sci. 1978. 47:124-130.
© 1978 American Society of Animal Science
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Weaning Weight Correction Factors from Angus Field Data1

J. H. Anderson2 and R. L. Wilham3

Iowa State University, Ames 50011

Abstract

A mixed model study was carried out on 499,894 weaning weight records collected by the American Angus Association to evaluate the influence of creep management, sex and age of dam and to derive correction factors for these environmental influences that equalize the means and the variance of the weights. Regional differences were also evaluated.

Regions were statistically (P<.05) different. The magnitude of region differences was small and the large number of observations contributed to significance. Data from each region were pooled for an overall analysis. The results indicated that creep management, sex, age of dam, interactions of management by sex, management by age of dam and sex by age of dam were statistically significant (P<.005). The age of dam constant estimates indicated that weaning weight increases as cows mature and declines after some peak periods between 6 and 9 years of age. The sex estimates indicated that bull calves were 20 kg heavier and steer calves were 13 kg heavier than heifer calves, and the management estimates indicated that creep fed calves were 12 kg heavier than noncreep fed calves. The sex by age of dam interaction indicated that separate correction factors for age of dam should be used for each sex. An additive adjustment for age of dam within sex and a multiplicative adjustment for sex is recommended.

Footnotes

1 Journal Paper No. J-8901 of the Iowa Agriculture and Home Economics Experiment Station, Ames. Project No. 2000.

2 Department of Animal Science, North Carolina State University, Raleigh 27607.

3 Department of Animal Science, Iowa State University.






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