A total of 133 sows (Line 241; DNA, Columbus, NE) were used to evaluate the effect of increasing soybean meal concentration in lactating sow diets on sow and litter performance. Sows were blocked by body weight and parity on d 112 of gestation and allotted to 1 of 3 treatments of increasing soybean meal (25, 30, or 35% of total diet). Diets were formulated to contain 1.05% SID Lys with L-Lys HCl decreasing as soybean meal increased. All other amino acids and nutrients were formulated to meet nutrient requirement recommendations with L-threonine, DL-methionine, L-tryptophan, and L-valine added to the 25% SBM diet. Diets were fed from d 112 of gestation until weaning (d 20 ± 2). Litters were cross-fostered until 48 h after farrowing to equalize litter size. Sow average daily feed intake from d 0 to 7 was similar across dietary treatments. However, ADFI decreased from d 7 to 14, d 14 to weaning, and overall, (linear, P = 0.017) sow BW loss, and tended to increase (quadratic, P = 0.052) backfat loss from farrowing to weaning. There was no evidence for difference between dietary treatments in litter size, litter weight, nursing litter weight gain at weaning, or wean to estrus interval. Sow serum urea nitrogen concentrations taken on d 14 increased (linear, P = 0.001) as soybean meal concentration increased; however, there was no evidence for difference in serum creatinine. In summary, sow feed intake decreased and sow weight and backfat loss increased with increasing soybean meal concentration with no differences observed for litter performance.
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