The effects of halothane susceptibility on some economically important traits in pigs 1. Litter productivity

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Abstract
The effects of susceptibility to halothane anaesthesia on litter productivity were investigated by comparing susceptible and normal females in two sets of data. The first comprised 206 litters from the first five generations of Pietrain/Hampshire synthetic lines selected for and against halothane susceptibility. Susceptible and normal females were mated to boars of their own type. The second data set consisted of 93 litters from the same susceptible and normal females mated to normal boars. Compared with normal contemporaries, litter sizes of susceptible females were reduced by 1·16 (s.e. 0·40) piglets at birth, and 1-76 (s.e. 0·41) at weaning (ca. 1 weeks). Maximum likelihood estimates of the proportions of piglet deaths from birth to weaning as a trait of susceptiblev.normal dams were 0·32v.014 (P < 0·001). There were no significant differences in piglet weights or perinatal mortality, and no apparent influence of piglet genotype on any trait. The lower litter size of susceptible females at weaning appeared to result from reductions in both numbers born and survival to weaning. The study bears out previous reports of a reduction in litter productivity due to the halothane gene. However, the present differences could have arisen largely from random genetic differentiation between lines, or linkage disequilibrium in the synthetic foundation population.