In late gestation, the amino acid requirements of primiparous sows increase substantially due to growth of the fetal pool and mammary gland development. Dietary Lys (protein) supply in late gestation can influence mammary development by the end of gestation, with an unknown impact on subsequent milk production. To determine the standardized ileal digestible (SID) Lys (protein) intake in late gestation necessary to optimize whole-body nitrogen retention in late gestation, piglet birth weight, and subsequent milk production, primiparous sows were fed 1 of the 7 isoenergetic diets with equally spaced increasing levels of SID Lys, primarily via the addition of soybean meal. Diets ranged from 70% to 160% of estimated SID Lys requirements according to NRC (2012) for late-gestating primiparous sows and were fed between day 90 of gestation and farrowing. After farrowing, all sows received a standard lactation diet. Sow body weight was not impacted by dietary treatment at any point, but increasing SID Lys intake in late gestation increased body weight gain in late gestation and loss in lactation. Both nitrogen retention in late gestation and piglet birth weight increased with increasing SID Lys intake and were maximized at 22.0 g SID Lys/d. Piglet body weight at weaning was not influenced by dietary treatment, but estimated milk yield increased with increasing SID Lys intake in late gestation, and was maximized at 22.7 g SID Lys/d. Therefore, the requirements for SID Lys in late gestation should be increased to 22.7 g SID Lys/d to maximize late-gestation whole-body nitrogen retention, piglet birth weight, and subsequent milk yield.

Read the full article in the Journal of Animal Science.