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Genetic and Phenotypic Parameter Estimates for Growth and Wool Traits in Hampshire Sheep¹

University of Nebraska³, Lincoln 68583

Abstract

Birth weight (BW) data on 1,536 lambs and 70day weaning weight (WW) on 1,328 lambs born in 1969 to 1976, and 6-month weight (6MW) on 1,061 lambs and 12-month weight (12MW) on 859 lambs born in 1969 to 1975 were studied. Data were adjusted for age of lamb and to a 4-year-old dam, single born and reared, ram lamb basis. Average weights and standard deviations in kilograms were: (BW) 5.80 and .76; (WW) 22.87 and 4.44; (6MW) 44.36 and 7.40; and (12MW) 66.45 and 8.97. Paternal half-sib correlations from a variance-covariance analysis using the nested model year-line, sires within year-line and progeny within sires were used in estimating heritabilities and genetic correlations. Estimated heritability was.21 ±.08, –.09±.06, .28 ±.10 and. 11 ±.11 for BW, WW, 6MW and 12MW, respectively. Heritability estimates of other traits measured at weaning time were: face score (.44±.10), fleece length (.47 + .11), fleece grade (.06+ .07), uniform fleece grade (.15 + .08) and body conformation score (.06 + .07). Genetic and phenotypic correlations estimated from the paternal half-sib analyses were: 0 and .25 (BW–WW), –.34 and .22 (BW–6MW), .04 and .23 (BW–12MW), 0 and .61 (WW–6MW), 0 and .50 (WW–12MW), and .46 and .77 (6MW–12MW). Phenotypic correlations between the weight traits and the wool and conformation traits ranged from –.06 to .44.

Regressions of offspring on sire, dam and mid-parent, pooled across line-year of birth classes, were also used to estimate heritabilities and genetic correlations of the weight traits. Estimates of heritability by trait were: (BW) . 10 ± .07, .24 ± .08, .17±.06; (WW) –.06±.07, .50±.12, .12±.07; (6MW) .19±.11, .34±.09, .33±.08; and (12MW) .44±.12, .88±.17, .64±.12, from offspring-sire, offspring-dam, and offspring-midparent regressions, respectively. Estimates of genetic correlations averaged across four methods using offspring-parent regressions were: .06 (BW-WW),–.11 (BW–6MW), .13(BW–12MW), .83 (WW–6MW), .72 (WW–12MW) and .76 (6MW–12MW).

¹ Published as Paper No. 5399, Journal Series, Nebraska Agricultural Experiment Station, Lincoln 68583.

² Present Address: Animal Science Department, Oklahoma State University, Stillwater 74074.

³ Department of Animal Science.