The effect of increased standardized ileal digestible lysine through increased soybean meal during late gestation on sow lactation performance

A total of 87 sows (Line 241, DNA) and their offspring were used to evaluate the effects of increasing standardized ileal digestible (SID) Lys in late gestation diets on lactating sow and litter performance. Sows were blocked by parity and body weight (BW) on day 90 of gestation and allotted to one of three treatments with 29 replications per treatment. Diets included increasing dietary SID Lys (0.60, 0.80, or 1.00%) accomplished by increasing soybean meal (14, 21, or 29% of the diet). Sows were allowed 2.04 kg/d of their treatment diet from day 90 of gestation until farrowing for average SID Lys intakes of 11.9, 15.8, or 19.9 g/d. After farrowing, sows had ad libitum access to a common lactation diet containing 1.10% SID Lys. Urine samples were collected on day 90 and 110 of gestation to determine urinary creatinine levels. Litters were cross-fostered within dietary treatment by 48 h after farrowing to equalize litter size. Parity group was included in the statistical model as a fixed effect with classifications of primiparous (n = 35) or multiparous (n = 52) sows. Weight gain from day 90 to 110 of gestation increased (linear, <i>P</i> < 0.001) as SID Lys increased. Change in urinary creatinine level from day 90 to 110 of gestation tended to decrease (linear, <i>P</i> = 0.063) as SID Lys increased suggesting that muscle catabolism decreased with increasing SID Lys. There were no differences in starting litter size or piglet birth weight with increasing SID Lys in late gestation. Piglet average daily gain (ADG) from day 2 to 10 of lactation increased (linear, <i>P </i>= 0.017) as SID Lys increased. From day 2 until weaning, litters from sows fed 15.8 g/d of SID Lys in gestation had the greatest (quadratic, <i>P</i> = 0.044) litter weight gain. Pre-weaning mortality from birth until day 2 of lactation was greatest for sows fed 15.8 g/d of SID Lys (quadratic, <i>P</i> = 0.025). There was a parity group × gestation diet interaction (<i>P</i> = 0.049) for pre-weaning mortality from day 2 to weaning where mortality increased as SID Lys increased in primiparous sows but decreased in multiparous sows. However, the differences in mortality did not influence the number of pigs weaned per treatment. In conclusion, increased SID Lys through increased soybean meal linearly increased late gestation sow BW gain and piglet ADG during early lactation. Litters from sows fed 15.8 g/d of SID Lys had the greatest litter ADG during late lactation and overall.