Journal of Animal Science, Vol 77, Issue 7 1659-1665, Copyright © 1999 by American Society of Animal Science

JOURNAL ARTICLE

Genetic parameters for growth traits for a composite terminal sire breed of sheep

E. Mousa, L. D. Van Vleck and K. A. Leymaster
Department of Animal Science, University of Nebraska, Lincoln 68583-0908, USA.

Records of 9,055 lambs from a composite population originating from crossing Columbia rams to Hampshire x Suffolk ewes at the U.S. Meat Animal Research Center were used to estimate genetic parameters among growth traits. Traits analyzed were weights at birth (BWT), weaning (7 wk, WWT), 19 mo (W19), and 31 mo (W31) and postweaning ADG from 9 to 18 or 19 wk of age. The ADG was also divided into daily gain of males (DGM) and daily gain of females (DGF). These two traits were analyzed with W19 and with W31 in three-trait analyses. (Co)variance components were estimated with REML for an animal model that included fixed effects of sex, age of dam, type of birth or rearing, and contemporary group. Random effects were direct and maternal genetic of animal and dam with genetic covariance, maternal permanent environmental, and random residual. Estimates of direct heritability were .09, .09, .35, .44, .19, .16, and .23 for BWT, WWT, W19, W31, ADG, DGM, and DGF, respectively. Estimates of maternal permanent environmental variance as a proportion of phenotypic variance were .09, .12, .03, .03, .03, .06, and .02, respectively. Estimates of maternal heritability were .17 and .09 for BWT and WWT and .01 to .03 for other traits. Estimates of genetic correlations were large among W19, W31, and ADG (.69 to .97), small between BWT and W31 or ADG, and moderate for other pairs of traits (.32 to .45). The estimate of genetic correlation between DGM and DGF was .94, and the correlation between maternal permanent environmental effects for these traits was .56. For the three-trait analyses, the genetic correlations of DGM and DGF with W19 were .69 and .82 and with W31 were .67 and .67, respectively. Results show that models for genetic evaluation for BWT and WWT should include maternal genetic effects. Estimates of genetic correlations show that selection for ADG in either sex can be from records of either sex (DGM or DGF) and that selection for daily gain will result in increases in mature weight but that BWT is not correlated with weight at 31 mo.

This article has been cited by other articles:

				R. C. Borg, D. R. Notter, and R. W. Kott Phenotypic and genetic associations between lamb growth traits and adult ewe body weights in western range sheep J Anim Sci, November 1, 2009; 87(11): 3506 - 3514. [Abstract] [Full Text] [PDF]

				K. M Cammack, K. A. Leymaster, T. G. Jenkins, and M. K. Nielsen Estimates of genetic parameters for feed intake, feeding behavior, and daily gain in composite ram lambs J Anim Sci, April 1, 2005; 83(4): 777 - 785. [Abstract] [Full Text] [PDF]

				B. R. Southey, S. L. Rodriguez-Zas, and K. A. Leymaster Competing risks analysis of lamb mortality in a terminal sire composite population J Anim Sci, October 1, 2004; 82(10): 2892 - 2899. [Abstract] [Full Text] [PDF]

				G. D. Snowder and L. D. Van Vleck Estimates of genetic parameters and selection strategies to improve the economic efficiency of postweaning growth in lambs J Anim Sci, November 1, 2003; 81(11): 2704 - 2713. [Abstract] [Full Text] [PDF]

				B. R. Southey, S. L. Rodriguez-Zas, and K. A. Leymaster Discrete time survival analysis of lamb mortality in a terminal sire composite population J Anim Sci, June 1, 2003; 81(6): 1399 - 1405. [Abstract] [Full Text] [PDF]