Selection in Hereford Cattle. I. Selection Intensity, Generation Interval and Indexes in Retrospect

Nwakalor, L. N.; Brinks, J. S.; Gv, Richardson

doi:10.2527/jas1986.624927x

Cited by 3 publications

(4 citation statements)

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“…As demonstrated earlier (Nwakalor et al, 1986) most of the selection pressure for increased weights and gains was on the sires. Therefore, sire contribution to progress in the postweaning traits of females has to be taken into account.…”

Section: Resultsmentioning

confidence: 63%

“…The data were the same as those used in the first paper of this series (Nwakalor et al, 1986) to study the intensity of selection; 14 inbred lines and 14 corresponding (by line of inbred sire) linecross groups of Hereford cattle at San Juan Basin Research Center, Hesperus, Colorado. The birth and weaning traits studied were birth weight (BW), heart girth circumference (HGC) at birth, weaning weight (WW), weaning 937 J. Anim.…”

Section: Methodsmentioning

confidence: 99%

“…Postweaning traits of females included gain from weaning to 12 mo, 12-mo weight (12W), gain from 12 to 18 too, 18-mo weight (18W) and mature cow weights in spring (SPW), summer (SUW) and fall (FAW). Adjustments of data were as given previously (Nwakalor et al, 1986).…”

Section: Methodsmentioning

confidence: 99%

“…In the first paper of this series (Nwakalor et al, 1986), the selection applied and the generation intervals were studied in inbred and linecross populations of a Hereford cattle herd. The purpose of this paper is to evaluate the expected genetic progress, as well as the genetic response actually realized, in the same herd.…”

Section: Introductionmentioning

confidence: 99%

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Selection in Hereford Cattle. II. Expected and Realized Response

Nwakalor

Brinks

Gv³

1986

Journal of Animal Science

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Data from 14 inbred lines and 14 linecross groups of Hereford cattle at the San Juan Basin Research Center, Hesperus, were used to evaluate expected and realized response in birth and weaning traits and postweaning traits in males and females over a 28-yr period. There were large differences in the means and variances of the performance traits among the inbreds and linecrosses, with the inbreds showing inbreeding depression and greater variability among lines, while the linecrosses manifested within-breed heterosis. Except for gain from weaning to 12 mo, in females, genetic progress was expected in all traits studied, mainly due to sire selection. Regressions of annual trait means on years indicated positive phenotypic trends in the inbreds for heart girth circumference at birth, adjusted weaning weight (adjusted for inbreeding), weaning score, final weight, feed consumption and the yearling weights and gains in females. Changes were negative for other traits. In the linecross group phenotypic trends were positive in all traits except heart girth circumference, weaning age, initial test weight and feed efficiency. Estimated genetic progress per generation due to within-line selection was negative in most of the traits in the inbreds but was considerably positive for the linecrosses for most of the traits. As expected, between-line selection yielded greater genetic improvement in the inbred than in the linecross population. The different patterns of response in the two populations are attributed to high rates and levels of inbreeding. Although variable, the actual progress was below prediction in most of the traits studied.

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Section: Resultsmentioning

confidence: 63%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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