Date of this Version
These data included the records of 818 purebred gilts and sows of Duroc, Hampshire and Yorkshire breeding mated to produce all purebreds and all possible two-way crosses. A total of 212 gilts were slaughtered 30-day postbreeding (72 purebred matings and 140 crossbred matings) to evaluate ovulation rate, number of live embryos, average embryo length and embryo survival rate. A total of 450 litters (161 purebred and 289 crossbred) were farrowed to evaluate litter size, litter weight and average pig weight at O, 21 and 42 days postfarrowing. Litters were farrowed in the spring and fall of 1971 and 1973 and the summer of 1972. Of the 818 females selected for breeding, 16.4% failed to exhibit estrus or to be pregnant at slaughter or farrowing. Failure rates were similar for sows and gilts with Yorkshires having the most and Hampshires the least. Duroc and Yorkshire females ovulated more eggs and had more embryos 30 days postbreeding than did Hampshire females (P<.05). Yorkshires were the most productive of the straightbreds in terms of litter size and weight. Breed of dam and breed of sire effects were evident for many traits evaluated. Heterosis estimates were not significant for embryo data but were large and significant for litter size and weight at 42 days postfarrowing due to the 7.78% higher survival rate of the crossbred pigs. Duroc and Hampshire dams expressed significant response to crossbreeding regardless of the breed of sire used for crossbred litter production, but Yorkshires did not. However, Yorkshire dams had larger and heavier litters when mated to Duroc boars compared to Yorkshire boars.