Supplemental lysine for sows nursing large litters.

A cooperative experiment involving 501 litters was conducted at four stations to assess the effects of supplemental lysine on lactational performance of sows nursing large litters. Basal diets were formulated to contain .60% lysine from corn or sorghum and soybean meal. Lysine.HCl (78.8% lysine) was substituted for grain to achieve dietary lysine levels of .75 and .90%. First-parity sows nursed a minimum of nine pigs per litter and older sows a minimum of 10 pigs per litter by d 3 of lactation. Overall mean litter size at 21 d of age was 9.7 pigs. Sows remained on treatment for three successive parities unless culled for structural unsoundness or reproductive failure. Dietary lysine did not affect body weight or backfat loss during lactation, sow ADFI, interval from weaning to estrus, or litter size at birth or at 21 d of age. Mean pig weights at birth and at 21 d of age increased quadratically to increasing lysine, with improvements found at all stations from increasing lysine from .60 to .75%. Twenty-one-day pig weights did not increase at the highest lysine level at stations feeding corn, but did improve at the station feeding sorghum, which resulted in a treatment x station interaction (P < .05). The different responses to lysine on different grain sources indicates intake of one or more other amino acid may have limited lactation performance at the highest level of lysine. These data indicate that a 13% CP corn-soybean meal containing .60% lysine is inadequate for sows nursing large litters and that supplemental synthetic lysine beyond .15% additional lysine will not be beneficial due to a deficiency of one or more other amino acids.