Benefit of multiple trait selection to increase reproductive traits: experimental evidence from golden hamsters.

Fifteen generations of selection were conducted to study responses for litter size at birth (LSB), weight at weaning of standardized litter (LWW), and individual body weight at 8 wk of age (BW8) using golden hamsters as an experimental model for pigs. The experiment involved three lines: selection on an aggregate breeding value of LSB, LWW, and BW8 (line W); selection on an aggregate breeding value of LSB and LWW (line R); and a randomly selected control (line C). Selection in W and R was based on breeding values from a multiple trait animal model. Restricted maximum likelihood with an animal model was used to estimate genetic parameters and genetic trends. Heritability estimates for LSB, LWW, and BW8 were .10, .47, and .52, respectively, and genetic correlations between traits were all positive. The mean estimated breeding value (EBV) for LSB in generation 15 was +2.2 pups in W and R. The mean EBV for LWW in generation 15 was +318 g for W and +174 g for R, and for BW8 means were +64 g and +24 g, respectively. Average inbreeding at generation 16 was 13.4, 19.5, and 8.0% for W, R, and C, respectively. Including BW8 in the selection criterion reduced inbreeding and had a beneficial effect on selection responses in LSB, LWW, and BW8.