Prediction of performance of progeny from test station boars

Data were obtained from 1,954 Duroc and 2,252 Yorkshire purebred and crossbred progeny sired by 34 Duroc and 32 Yorkshire boars, respectively. Boars were purchased from the North Carolina Swine Evaluation Station during August 1983 to December 1988. Boars were selected to represent high and low indexes at the test station. Progeny were raised and tested under conditions similar to commercial pig production at the Tidewater Research Station. For each breed of boar (Duroc and Yorkshire), breed type (purebred and crossbred), and sex (castrates and gilts) of progeny, regression coefficients of progeny traits on each sire trait were computed. Progeny traits were ADG, days to 104.3 kg BW (DAYS), backfat thickness (BF), and feed conversion ratio (FC). Sire traits were ADG, DAYS, BF, FC, and INDEX. Effects of boar test group and progeny test group were included in the models. Averaged over breed type and sex, a 25-unit (1 SD) increase in sire INDEX resulted in 14.5 g more ADG, 3.2 fewer DAYS, .57 mm more BF, and .017 lower FC in Durocs and 5.6 g more ADG, .01 more DAYS, .81 mm less BF, and .083 lower FC in Yorkshires. The low magnitude and variable signs of some regression coefficients suggested that predictions of progeny performance from performance of individual sires at the North Carolina Swine Evaluation Station were not very reliable. Differences between regressions for purebreds and crossbreds implied small correlations between the two breed types. Differences between Durocs and Yorkshires indicated that genetic parameters might not be the same for the two breeds.