SUPPLEMENTAL LYSINE FOR SOWS NURSING LARGE LITTERS

A cooperative experiment involving 501 litters was conducted at four s tations to assess the effects of supplemental lysine on lactational pe rformance of sows nursing large litters. Basal diets were formulated t o contain .60% lysine from corn or sorghum and soybean meal. Lysine HC l (78.8% lysine) was substituted for grain to achieve dietary lysine l evels 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 l actation. Overall mean litter size at 21 d of age was 9.7 pigs. Sows r emained on treatment for three successive parities unless culled for s tructural unsoundness or reproductive failure. Dietary lysine did not affect body weight or backfat loss during lactation, sow ADFI, interva l from weaning to estrus, or litter size at birth or at 21 d of age. M ean pig weights at birth and at 21 d of age increased quadratically to increasing lysine, with improvements found at all stations from incre asing lysine from .60 to .75%. Twenty-one-day pig weights did not incr ease at the highest lysine level at stations feeding corn, but did imp rove at the station feeding sorghum, which resulted in a treatment x s tation interaction (P <.05). The different responses to lysine on diff erent grain sources indicates intake of one or more other amino acid m ay have limited lactation performance at the highest level of lysine. These data indicate that a 13% CP corn-soybean meal containing .60% ly sine is inadequate for sows nursing large litters and that supplementa l synthetic lysine beyond .15% additional lysine will not be beneficia l due to a deficiency of one or more other amino acids.