|VAN ZYL, C|
|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: 3/1/1998
Publication Date: N/A
Technical Abstract: The objective of this study was to estimate correlations for Columbia, Polypay, Rambouillet and Targee breeds between the composite trait, litter weight weaned (4,609; 6,469; 5,101; 5,708 records), and fertility (1,941; 3,261; 2,268; 2,402), growth (7,750; 9,524; 9,530; 9,321) and wool (11,673; 34,746; 18,443; 15,014) traits. Data were from the U.S. Sheep Experiment Station. Fertility was recorded as litter size at birth. Growt traits included birth weight, and average daily gain from birth to weaning. Wool traits included greasy fleece weight, fleece grade and staple length. The bivariate analyses, using derivative-free restricted maximum likelihood with animal models, included a covariance between additive genetic effects of the two traits plus appropriate additional covariances. Growth traits included an additional maternal genetic effect with covariances between direct and maternal genetic effects. The ranges in estimates of direct genetic correlations were as follows between litter weight weaned and: litter size at birth, -.30 to .43; birth weight, -.03 to .44; average daily gain, .21 to .67; fleece weight, -.20 to .27; fleece grade, -.07 to .19; and staple length, -.11 to .04. These estimates suggest a moderate posi- tive genetic correlation between direct genetic effects for litter weight weaned and litter size at birth, a small to moderate positive genetic correlation between direct genetic effects for litter weight weaned and growth traits, and a near zero genetic correlation between direct genetic effects for litter weight weaned and wool traits. These estimates of genetic parameters between litter weight weaned, and fertility, growth and wool traits can be used with appropriate economic values to construct multiple-trait selection indexes for dual-purpose sheep.