ARS | Publication request: The Lysine and Total Sulfur Amino Acid Requirements of Six- to Twelve-kilogram Pigs

Submitted to: Professional Animal Scientist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 1, 2007
Publication Date: October 1, 2007
Citation: Dean, D.W., Southern, L.L., Kerr, B.J., Bidner, T.D. 2007. The Lysine and Total Sulfur Amino Acid Requirements of Six- to Twelve-kilogram Pigs. The Professional Animal Scientist. 23(2007):527-535.

Interpretive Summary: The excretion of nitrogen and volatilization of ammonia are major concerns for the livestock industry, impacting both environmental quality and animal productivity. In order to optimize nitrogen utilization in the pig and not excrete nitrogen into the environment, it is critical to understand limiting amino acid requirements and ratios. The total sulfur amino acids (TSAA), which include methionine and cysteine, have required additional research to understand limitations in diets fed to swine. This research demonstrated that approximately 10.14 mg of true ileal digestible TSAA is required per gram of body weight gain, which equates to a TSAA:lysine ratio that is approximately 0.54. This information is important for scientists at universities, feed companies, and swine production facilities to formulate diets that optimize nitrogen utilization in the pig while minimizing nitrogen excretion into the environment.

Technical Abstract: Three experiments (Exp.) were conducted to determine the Lys and TSAA requirement of 6- to 12-kg pigs. There were five replications of five or six pigs per pen (n = 150, 150, and 168 with initial BW of 6.3, 6.7, and 6.4 kg and final BW of 10.8, 11.7, and 11.2 kg for Exp. 1, 2, and 3, respectively). In Exp. 1, pigs were fed in a 13-d growth assay and treatments were: positive control (PC, 40% corn, 38% soybean meal, 10% whey, 3% fishmeal, and 3% fat; 1.45% true ileal digestible (TID) Lys), and tid Lys levels of 1.1, 1.2, 1.3, 1.4, and 1.5%. The addition of Lys increased gain:feed (G:F; linear, P < 0.05), ADG (linear, P < 0.05; quadratic, P < 0.05), and ADFI (linear, P < 0.05; quadratic, P < 0.10). Growth performance of pigs fed the three highest levels of Lys was not different from those fed the PC diet. Plasma urea N (PUN) decreased linearly (P < 0.001) with the addition of Lys. Break point analysis estimated requirements of 1.43 and 1.41% for ADG and PUN, respectively. In Exp. 2, pigs were fed in a 14-d growth assay and treatments were: PC (similar to that in Exp. 1; 0.88% TID TSAA), and TID TSAA levels of 0.62, 0.68, 0.74, 0.80, and 0.86% with a TID Lys level of 1.35%. There was no response of increasing TSAA from 0.62 to 0.86%. In Exp. 3, pigs were fed in a 13-d growth assay and treatments were: PC (same as Exp. 2) and TID TSAA levels of 0.52, 0.58, 0.64, 0.70, and 0.76% with a TID Lys level of 1.35%. The addition of TSAA increased ADG (linear, P < 0.05; quadratic, P < 0.05) and decreased PUN (linear and quadratic, P < 0.001). However, pigs receiving the basal diet with varying levels of TSAA had lower ADG (P < 0.05) and G:F (P < 0.001) than pigs fed the PC diet. Break point analysis estimated requirements of 0.58 and 0.56% TID TSAA for ADG and PUN, respectively. Data from these experiments suggest the TID Lys requirement is 1.40% or 18.90 mg TID Lys/g gain for 6- to 12-kg pigs, and the TID TSAA requirement is near 10.14 mg TID TSAA/g gain resulting in a TSAA:Lys ratio that is approximately 0.54.