Some Production Factors Associated with Weaning Records in Swine

The farrowing and 42-day weaning records for 453 litters (4,744 pigs farrowed and 3,775 pigs weaned) from five lines of breeding were analyzed to study factors influencing litter weaning weight and to determine the interrelationships between litter size, pig weights, litter weights, preweaning death loss and weight gain of dam during lactation. Litter weaning weight was determined to a larger extent by the number of pigs in the litter at weaning than by the weight of the pigs at weaning. The number of pigs farrowed in the litter had a slightly greater influence on the litter size at 42 days than did survival rate, but both were important factors in determining size of litter at weaning. Weight of the pig at 42 days was dependent principally on the pig's gain from birth to weaning and to a very limited degree on the pig's birth weight. Number of pigs in the litter at birth accounted for 67% of the variation in litter birth weight and for 28% of the variation in pig birth weight. Litter size at birth was significantly correlated with survival rate of the pigs to weaning (−.28), litter size at weaning (0.70), litter weaning weight (0.50) and pig weaning weight (−.49). Litters of 11 to 14 pigs farrowed resulted in more pigs weaned per litter than litters of 15 to 16 pigs. Since litter birth weight was largely a function of number of pigs in the litter (r=0.82), an increase in litter birth weight was associated with an increase in preweaning death loss, litter size at weaning and litter weaning weight, but with a decrease in pig weaning weight. However, an increase in pig birth weight was associated with an increase in survival rate (r=0.28) and pig weaning weight (r=0.54), and with smaller litter size at weaning (r=−.32). Weight loss of the dam during lactation was associated with increased litter size and litter weights. The average weight loss of the dam during lactation was 17.3 kg. with no significant difference detected between sows and gilts. Number of pigs weaned per litter was closely associated with litter weaning weight (r=0.79), and individual pig weaning weight decreased as litter size at weaning increased (r=−.51). The heaviest pigs at 42 days of age occurred in litters of three to four pigs for sows and in litters of less than six for gilts.