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This Article Full Text Full Text (PDF) All Versions of this Article: jas.2008-1622v1 87/11/3506    most recent Alert me when this article is cited Alert me if a correction is posted Services Related articles in J. Anim Sci. Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Borg, R. C. Articles by Kott, R. W. PubMed PubMed Citation Articles by Borg, R. C. Articles by Kott, R. W.

Phenotypic and genetic associations between lamb growth traits and adult ewe body weights in western range sheep

R. C. Borg^*,1, D. R. Notter^*,2 and R. W. Kott

^* Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State University, Blacksburg 24061; and Department of Animal and Range Sciences, Montana State University, Bozeman 59717

² Corresponding author: drnotter{at}vt.edu

Data from the Montana State University Targhee flock were used to estimate genetic and environmental relationships between lamb BW and adult ewe BW, condition score, and prolificacy. The flock was managed under commercial western range conditions typical of the area. Data included records from 12,154 lambs born to 2,930 dams and 200 rams between 1960 and 2005. Lamb traits included BW at birth and approximately 45 d, 120 d (weaning), 12 mo, and 18 mo of age and fleece characteristics at 12 mo of age. Adult traits included ewe litter size; BW and BCS at weaning, in late gestation, and in early lactation; and adult fleece measurements. Multiplicative factors were used to adjust (pre)weaning lamb BW for effects of age of dam, type of birth and rearing, and lamb sex and to adjust adult litter sizes for effects of ewe age. An animal model was used to estimate genetic relationships. Models for lamb traits included fixed effects of year of birth and, for postweaning data, lamb sex and random additive genetic effects and, for (pre)weaning BW, additive genetic maternal and permanent environmental maternal effects. Models for adult traits included fixed effects of year of birth, year of record, and, when appropriate, numbers of lambs born or born and reared and random additive genetic and animal permanent environmental effects. Heritability estimates for lamb birth weight, 45-d BW, weaning weight, yearling weight, 18-mo BW, fleece weight, staple length, and spinning count were 0.19, 0.07, 0.12, 0.32, 0.38, 0.32, 0.31, and 0.25, respectively. Maternal heritabilities for lamb birth, 45-d, and weaning weights were 0.15, 0.09, and 0.08, respectively. Heritability estimates for adult traits were 0.12 for litter size, averaged 0.43 for BW and 0.13 for body condition, and were 0.44, 0.37, and 0.25 for adult fleece weight, staple length, and spinning count, respectively. Correlations between genetic effects on adult BW and direct and maternal genetic effects on lamb BW ranged from 0.21 to 0.96 (P < 0.05) and 0.29 to 0.53 (P < 0.05), respectively, with residual correlations ranging from 0.05 to 0.95. Correlations of lamb traits with adult body condition and number of lambs born were generally not different from zero; genetic and residual correlations ranged from –0.52 to 0.69 and –0.39 to 0.31, respectively.

Key Words: body condition • genetic parameter • growth • sheep • size

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Genetic analysis of ewe stayability and its association with lamb growth and adult production

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J. Anim Sci. 2009 87: 3515-3524. [Abstract] [Full Text]