|Van Vleck, Lloyd|
Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 1, 1999
Publication Date: N/A
Interpretive Summary: Individual feed intake is difficult to measure when animals are penned in groups. An important question is whether daily gain made under con- ditions necessary for automated measure of individual intake is geneti- cally correlated with gain in typical feedlot conditions. This study at MARC correlated gain of 1,101 rams fed from 11 to 17 weeks of age in Pinpointer Units which measured individual feed intake with gain of 2,021 ram and 3,513 ewe lambs fed under feedlot conditions for 10 weeks beginning at 9 weeks of age. Heritability estimates were similar for the three groups. Genetic correlations among pairs of the three groups were .86, .83, and 1.00. Such large correlations indicate that gain of rams measured in Pinpointer Units would accurately reflect gain of the same genotype in both ram and ewe lambs fed under feedlot conditions.
Technical Abstract: When performance is recorded in automated facilities that measure feed intake of individual lambs penned in a group, a legitimate question is whether that daily gain is genetically correlated with daily gain under feedlot conditions. Lambs were from a composite population (1/2 Columbia, 1/4 Suffolk, and 1/4 Hampshire). Data were daily gains of 1,101 rams (PR) fed in Pinpointer units (11 to 17 wk of age) and 2,021 rams (FR) and 3,513 ewes (FE) fed under feedlot conditions (9- or 10- weeks starting at 9 wk of age). The FR and FE lambs were born from 1983 through 1995 and PR lambs were born from 1986 through 1995. Measurements of daily gain of PR, FR, and FE were considered to be three correlated traits. Unadjusted means were .411, .406, and .326 kg/d, respectively. Random effects in the model were direct and maternal genetic and maternal permanent environmental. Fixed effects were age of dam (1 to 6 yr), type of rearing (1 to 4), and contemporary group. Maternal genetic effects with single-trait analyses were negligible so those effects were eliminated from the three-trait analysis although an effect due to dam was included in the model. Esti- mates of heritability were .22, .14, and .23 for PR, FR, and FE, respecti- vely. Fractions of variance due to dam effects ranged from .02 to .05. Estimates of genetic correlations were .86 for PR with FR, .83 for PR with FE, and 1.00 for FR with FE. Estimated phenotypic variances were similar for PR and FR, but one-third less for FE. Similarity of heritability estimates and estimates of genetic correlations all exceeding .83 suggest that daily gain of rams fed in Pinpointer units will reflect genetic expression for daily gain in ram and ewe lambs fed under feedlot conditions.