Genetic Variation and Covariation for Ewe Reproduction, Lamb Growth, and Lamb Scrotal Circumference in a Fall-Lambing Sheep Flock

S. A. Al-Shorepy, D. R. Notter

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    73 Citations (Scopus)

    Abstract

    Genetic parameters for female reproduction, lamb growth, and lamb scrotal circumference in a composite population of 50% Dorset, 25% Rambouillet and 25% Finnsheep breeding selected for ability to lamb in fall were estimated by REML using various animal models. Traits considered were spring fertility, litter size, weight at weaning (WWT), 90 d (WT90), and 120 d (WT120), and scrotal circumference at weaning (WSC), 90 d (SC90), and 120 d (SC120). Fertility was defined as 1 or 0 for ewes that lambed or failed to lamb, respectively, in fall and averaged .59 for adults (3 yr and older), .45 for second-lambing ewes, .18 for 19-mo-old ewes, and .11 for 12-mo-old ewes. Heritability estimates for fertility varied among models from .07 to .11. Heritability of fall litter size was .10. For body weights, estimates of additive direct, additive maternal, permanent environmental maternal, and litter effects as proportions of phenotypic variance were .04, .10, .05, and .11, respectively, for WWT, .09, .05, .14, and .01 for WT90, and .18, .0, .13, and .06 for WT120. Heritability estimates for WSC, SC90, and SC120 were .15, .25, and .02, respectively. Estimates of genetic correlations among body weights ranged from .77 to unity. Estimates of genetic correlations of fertility with fall litter size, WT90, and SC90 were .56, -.31, and .29, respectively. Genetic correlations of fall litter size with WT90 and SC90 were .33 and .36, respectively. Estimated genetic correlations revealed no major genetic antagonisms with ability to lamb in fall.

    Original languageEnglish
    Pages (from-to)1490-1498
    Number of pages9
    JournalJournal of Animal Science
    Volume74
    Issue number7
    DOIs
    Publication statusPublished - Jul 1996

    Keywords

    • Genetic Parameters
    • Growth
    • Reproduction
    • Selection
    • Sheep

    ASJC Scopus subject areas

    • Food Science
    • Animal Science and Zoology
    • Genetics

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