Abstract
Twenty sows and their litters were observed at regular intervals over the 1st week post partum to determine piglet-teat relationships. At 7 days of age, three piglets were exchanged between five pairs of litters, the other 10 litters remaining intact as controls. Observations of sucking were continued for another week. All piglets were weighed at 3, 7 and 14 days of age. Cross-fostering disrupted the teat sucking relationships of the whole litter compared with those of control litters, but the probability of sucking at the same teat in the 2nd week as in the 1st was less in fostered piglets than in their non-fostered littermates. The weight gain of fostered piglets during the 2nd week was reduced to 79% of that in their non-fostered littermates. Both disruption of sucking and reduction in weight gain were greater in those piglets that had to compete, on their foster mother, for the teat they preferred during the 1st week than for those whose teat was free.