Determining the Dietary Standardized Ileal Digestible Lysine Level for Lactating Sows

Abstract As sow productivity has increased due to genetic improvement, lactation nutrient requirements should be re-evaluated to ensure that sow maintenance and litter performance are supported through adequate nutrient intake. The objective of this study was to determine the optimal standardized ileal digestible (SID) lysine requirement for lactation and litter performance, and on subsequent reproductive success. A total of 1,168 multiparous sows (Line 241; DNA Genetics, Columbus, NE) were allotted at entry to the farrowing stall to one of five dietary treatments differing in SID Lys: 0.75, 0.90, 1.05, 1.20, or 1.35% SID Lys. Sows were fed these treatments throughout the lactation period, and sow reproductive, lactation and litter performance were assessed. Data were analyzed using linear and generalized linear models with treatment, parity, and sow body weight as fixed effects. Subsequent conception rates were analyzed using a binomial logistic model. Farrowing room was included as a random effect. During lactation, ADFI was greater in sows fed 0.90% and 1.05% SID Lys compared with 1.35%, with 0.75% and 1.20% intermediate (P = 0.010). Daily lysine intake (g/d) increased as dietary SID Lys increased (48, 59, 68, 77, and 85 g/d, respectively; P 0.001). Total litter wean weight and number of pigs weaned did not differ among treatments (P 0.10). However, average wean pig weight was greater in litters from sows fed 1.05% SID Lys (6.5 kg) compared with 0.75% (6.2 kg), with other treatments intermediate (P = 0.055). Pre-weaning mortality did not differ by treatment (P 0.10). Subsequent reproductive outcomes, including conception rate and wean-to-estrus interval, were also not affected by lactation SID Lys level (P 0.10). In conclusion, increasing dietary SID lysine above 1.05% did not enhance sow feed intake, litter growth, or subsequent reproductive performance. These findings suggest that a dietary SID lysine concentration of approximately 1.05%, corresponding to about 68 g of SID lysine intake per day, is sufficient to meet the lactation and reproductive requirements of modern, high-producing multiparous sows.