Genetic correlations for daily gain between ram and ewe lambs fed in feedlot conditions and ram lambs fed in Pinpointer units

When performance is recorded in automated facilities that measure feed inta ke of individual lambs that are penned in a group, such as Pinpointer units , a legitimate question is the degree to which daily gain is genetically co rrelated with daily gain achieved under feedlot conditions. Lambs were from a composite population (1/2 Columbia, 1/4 Suffolk, and 1/4 Hampshire germp lasm) and of the F-2 or more advanced generations. Data were daily gains of 1,101 rams (PR) fed in Pinpointer units (11 to 17 wk of age) and 2,021 ram s (FR) and 3,513 ewes (FE) fed under feedlot conditions (9- or 10-wk period starting at 9 wk of age). The FR and FE lambs were born from 1983 through 1995, whereas the PR lambs were born from 1.986 through 1995, Measurements of daily gain in PR, FR, and FE lambs were considered to represent three co rrelated traits. Unadjusted means were .411, .406, and .326 kg/d for PR, FR , and FE, respectively. Random effects in the model were animal direct gene tic, 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 w ith single-trait analyses were near zero, so those effects were eliminated from the three-trait analysis although a random uncorrelated effect due to dam was included in the model. Estimates of heritability were .22, .14, and .23 for PR, FR, and FE, respectively, with fractions of variance due to da m effects ranging 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 p henotypic variances were similar for PR and FR, but one-third less for FE. The similarity of heritability estimates and estimates of genetic correlati ons all exceeding .83 suggest that daily gain of rams fed in Pinpointer uni ts will reflect genetic expression for daily gain in both ram and ewe lambs fed under feedlot conditions.