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ARS Home » Plains Area » Clay Center, Nebraska » U.S. Meat Animal Research Center » Genetics and Animal Breeding » Research » Publications at this Location » Publication #143273
Title: MODELS WITH NUCLEAR, CYTOPLASMIC, AND ENVIRONMENTAL EFFECTS FOR PRODUCTION TRAITS OF COLUMBIA SHEEP

Author
item Hanford, Kathryn
item Snowder, Gary
item Van Vleck, Lloyd

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/23/2003
Publication Date: 8/1/2003
Citation: Hanford, K.J., Snowder, G.D., Van Vleck, L.D. 2003. Models with nuclear, cytoplasmic, and environmental effects for production traits of Columbia sheep. Journal of Animal Science. 81:1926-1932.

Interpretive Summary: The importance of effects of genetic material in the cytoplasm which is passed directly from mother to progeny has received little study for traits of sheep. Records of a long-term project at the US Sheep Experiment Station near Dubois, Idaho, allowed tracing cytoplasmic origins back to 1950. Records for representative traits (birth weight, n = 24,741; weaning weight, n = 23,903; fleece weight, n = 29,024; and number born per litter, n = 29,688)for Columbia lambs and ewes were available (1950-1998). Basic animal models comparable to those used for national sheep genetic evaluations were expanded to include cytoplasmic line effects and nuclear genotype (sire) by cytoplasmic line effects. For the four traits, cytoplasmic effects and sire by cytoplasmic effects accounted for little or no variation. With those effects added to the model, estimates of the basic genetic parameters (direct and maternal heritability) were unchanged. For birth weight, dam by year, dam by number born, and sire by dam effects accounted for 0.08, 0.04, and 0.04 of total variation. Inclusion of these effects in models would improve accuracies of national genetic evaluations. For fleece weight, sire by dam and dam by year effects accounted for 0.02 and 0.06 of phenotypic variance which was partitioned mostly from the animal permanent environmental variance so that addition of these effects to the model is unlikely to affect genetic evaluations.

Technical Abstract: Statistical models (17) were compared for birth weight of 24,741 Columbia lambs recorded at USSES (1950-1998). Goal was to estimate fractions of variance due to cytoplasmic line (c) and sire by cytoplasmic line interaction (sc). Basic model included direct genetic (fractional variance, (a), maternal genetic (m, with correlation r), and maternal permanent environmental (pm) effects. Model with sc was significantly better than basic model with and without c; but with other random effects added, sc became zero. Significant variance was associated with random dam by year (dy), sire by dam (sd) and dam by number born (dn) interaction effects. Estimates with all effects in model were: (a, 0.26; m, 0.24; r, -0.05; pm, 0.02; c, 0.00; dn, 0.04; dy, 0.08; sd, 0.04; sc, 0.00). Estimates for a, m, and r were the same for all models. Estimate of pm changed when other effects were added. Largest estimates for non-genetic effects were: pm, 0.06; c, 0.00; dy, 0.14; sd, 0.13; and sc 0.04. Estimates were similar whether or not Westell groups (n = 84) were in model. For 120-d weight, estimates of variances of effects added to basic model were all near zero (a, 0.14; m, 0.09; r, 0.23; pm, 0.04). For fleece weight and number born, animal permanent environmental effects were added to the model (pa) and r was dropped. For these traits, effects not in basic model had small variances. Non-zero estimates with full model were for FW: (a, 0.52; m, 0.01; pa, 0.06; sd, 0.02 and sc, 0.06) and for NB (a, 0.08; pa, 0.02; and sc, 0.01). Cytoplasmic effects were not important. Unusual random effects in the model did not change estimates for basic parameters. Although some effects were significant, especially for BW, effects on genetic evaluations are likely to be small.