Fetal growth and mammary development are the driving forces behind the nutrient requirements of sows beyond day 85 of gestation. Thus, nutrient requirements increase mainly in late gestation. Increasing standardized ileal digestible (SID) lysine (protein) supply by 40% (26 vs 19 g SID lysine per day) via the addition of soybean meal in late-gestating gilt diets, improved the amount of mammary development that occurred by the end of gestation.

Using a top-dress approach, simply providing 230 g per day (1.5 cups) of soybean meal per gilt in addition to the standard ration after gestation day 90 will better meet the estimated SID lysine requirements, without over-supplying energy and running the risk of over-conditioning the gilts prior to farrowing.

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