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 supplemental pyridoxine levels (1.0 vs. 15.0 ppm) on sow reproductive performance and nutrient metabolism in second-parity Yorkshire and Hampshire 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 reproductive performance in experiment 1 (N= 32) or 2 (N= 66). In exp. 2, feeding increased pyridoxine reduced the weaning to estrus interval (4.6 vs. 5.7 d, P = 0.11). It also increased the average daily apparent retention 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 pyridoxine had higher (P < 0.01) plasma pyridoxal and pyridoxic acid levels throughout the gestation period. The overall results indicate that increased dietary pyridoxine tended to have a positive influence on sow weaning to estrus interval and nitrogen metabolism, and it also tended to have a positive influence on litter size only in Yorkshire select line of sows.