|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science Supplement
Publication Type: Abstract Only
Publication Acceptance Date: March 1, 1999
Publication Date: N/A
Technical Abstract: When lamb performance is recorded in facilities that measure individual feed intake, such as Pinpointer units, a legitimate question is the degree to which daily gain is genetically correlated with daily gain with typical group-feeding. Lambs were from a composite population (1/2 Columbia, 1/4 Suffolk, and 1/4 Hampshire) of F2 or greater generations. Data were daily gains of 1,101 rams (PR) fed in Pinpointer units (11 to 17 wk of age) and 2,021 rams (TR) and 3,513 ewes (TE) fed typically (9- or 10- week period starting at 9 wk of age). The TR and TE lambs were born from 1983 through 1995, with PR lambs born from 1986 through 1995. Measurements of PR, TR, and the model were direct and maternal genetic, and maternal permanent environmental. Fixed effects were associated with age of dam (1 to 6 yr), type of rearing (1 to 4), and contemporary group (test date). Variances due to maternal genetic effects with single trait analyses were near zero so that factor was eliminated from three-trait analyses although an effect due to dam was included in the model. Estimates of heritability were .22, .14, and .23 for PR, TR, and TE with fractions of variance due to dam effects ranging from .02 to .05. Estimates of genetic correlations were .86 for PR with TR, .83 for PR with TE, and 1.00 for TR with TE. Estimated phenotypic variances were similar for PR and TR but one-third less for TE. Unadjusted means were .411, .406, and .326 kg/d for PR, TR, and TE. Similarity of heritability estimates and estimates of genetic correlations exceeding .83 suggest that average daily gain of rams fed in Pinpointer units can be used to predict genetic value for average daily gain in both ram and ewe lambs fed under typical conditions.