INTERACTIVE EFFECTS OF SELECTION FOR LOWER BACKFAT AND DIETARY PYRIDOXINE LEVELS ON REPRODUCTION, AND NUTRIENT METABOLISM DURING THE GESTATION PERIOD IN YORKSHIRE AND HAMPSHIRE SOWS

Two experiments were conducted to determine the interactive effects of selection for lower backfat over six generations, and two dietary sup plemental pyridoxine levels (1.0 vs. 15.0 ppm) on sow reproductive per formance and nutrient metabolism in second-parity Yorkshire and Hampsh ire sows. Feeding increased pyridoxine at 16.0 vs. 2.6 ppm from day of weaning through gestation did not improve (P > 0.05) the sow reproduc tive performance in experiment 1 (N = 32) or 2 (N = 66). In exp. 2, fe eding increased pyridoxine reduced the weaning to estrus interval (4.6 vs. 5.7 d, P = 0. 11). It also increased the average daily apparent r etention of nitrogen during gestation in both experiments 1 (17.2 vs. 7.8 g, P 0.11) and 2 (10.5 vs. 5.0 g, P = 0.10). Sows fed increased py ridoxine had higher (P < 0.01) plasma pyridoxal and pyridoxic acid lev els throughout the gestation period. The overall results indicate that increased dietary pyridoxine tended to have a positive influence on s ow weaning to estrus interval and nitrogen metabolism, and it also ten ded to have a positive influence on litter size only in Yorkshire sele ct line of sows.