Date of this Version
The data included records on 440 purebred sows and gilts of Duroc, Hampshire and Yorkshire breeding mated in all combinations to produce purebred and two-breed cross litters. A total of 119 purebred gilts (39 with purebred litters and 80 with crossbred litters) were slaughtered 30-days postbreeding and their reproductive tracts evaluated for number of corpora lutea and early embryo development. Farrowing records included 89 purebred and 161 two-breed cross litters produced at the Ft. Reno Experiment Station during the spring and fall of 1971 and the summer of 1972. Reproductive failures (females not exhibiting estrus or open at slaughter or open at farrowing) amounted to 13.4% of the total number of females selected to be mated. There was little difference between the percentage of failures for sows or gilts; however, Yorkshires had a failure rate of 23.4% compared to 8.5% for Durocs and Hampshires. Duroc and Yorkshire gilts each averaged 13.8 corpora lutea, which was 1.7 more (P<.01) than that for Hampshire gilts. Gilts with crossbred litters averaged 6.3% more embryos at 30-days postbreeding, 8.7% more pigs at farrowing and 17.9% more pigs at weaning than dams with purebred litters. Although the differences were not significant, the Duroc and Hampshire gilts with crossbred litters tended to have more normal embryos than did Duroc and Hampshire gilts with purebred litters; however, there was little difference in number of embryos between purebred and crossbred litters from Yorkshire gilts. Using a boar of another breed on Duroc dams increased litter glze by 1.44 ± .59 pigs at farrowing and by 1.54 ± .49 pigs at 42 days. Crossbreeding increased the litter size for Hampshire dams by 0.61 ± .61 pigs at farrowing and 1.33 ± .52 pigs at 42 days. Yorkshire dams with crossbred litters had 0.37 ± .66 more pigs per litter at farrowing and 0.30 ± .55 more pigs per litter at 42 days than Yorkshires with purebred litters. The survival rate for crossbred pigs compared to purebred pigs was 7.6% higher for Duroc dams and 17.9% higher for Hampshire dams; however, there was no difference in the survival rate of purebreds and crossbreds from Yorkshire dams. There was little evidence for differences in embryo length or average pig weight per litter between purebreds and crossbreds from any breed of dam. Yorkshire dams had larger litters at each age and the survival rate of pigs from Yorkshire dams was approximately 12% higher than the survival rate of pigs from Duroc and Hampshire dams.