Estimated uterine capacity in the highly prolific Chinese Meishan (MS) was compared with that in Large W hite (LW) and crossbred pigs using unilateral hysterectomy-ovariotom y (UHO) me _ In UHO females ovulation rate was similar to that found in intact females, being 6-7 eggs higher in the MS than in the LW and the MS also had 6 more viable embryos at 30 days of pregnancy. Crossbred sows were intermediate for ovulation rate and similar to the MS for number of embryos. Uterine capacity was estimated from the number of piglets subsequently born to be 2 piglets higherm MS sows than in LW and 2 piglets more in crossbred animals than in MS. In sows slaughtered at 30 days of pregnancy, MS were found to have smaller within litter variability in embryo size traits, especially in the distance between embryo sites. Crossbred litters were interm ediate between the purebreds in means and variability of embryo traits, but crossbred sows had significantly longer uten than both purebreds. Differences between the genotypes in uterine capacity may contribute to their differences in prolificacy and be particularly important in determining heterosis for litter size in crossbred females.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume 19. Selection and quantitative genetics; growth; reproduction; lactation; fish; fiber; meat., , 226–229, 1994
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