Abstract
The objective of this study was to characterize the growth response to total sulfur amino acids (TSAA) and lysine simultaneously to estimate the true-ileal-digestible (TID) TSAA-to-lysine ratio in early finishing pigs. One hundred and twenty-six pigs were used in a 27-d growth study. Pigs (73 to 134 lb) were blocked by sex and weight and were allotted to one of nine dietary treatments with five TID lysine (0.79, 0.87, 0.94, 1.02 and 1.10%) and five TID TSAA (0.53, 0.57, 0.61, 0.66 and 0.70%) concentrations. The highest lysine (1.10%) and TSAA (0.70%) concentrations were combined to form one treatment used in both the lysine and TSAA titrations. In diets evaluating increasing TID lysine, methionine & cysteine ratios were 64 to 66% of lysine; and in diets evaluating increasing TSAA, diets were formulated to 1.10% TID lysine. Increasing TID lysine increased ADG (linear, P<0.01) and improved F/G (quadratic, P<0.10) from d 0 to 14 and from d 0 to 27. No differences (P>0.05) were observed in ADFI. Increasing TSAA had no effect (P<0.05) on ADG or F/G, but pigs fed the diet containing 0.70% TSAA had numerically greater ADG than did pigs fed lower rates. As TSAA concentration increased to 0.61%, feed efficiency numerically improved (P = 0.16). Using a TID lysine requirement of 1.02% and TID TSAA requirement of 0.61% suggests a TSAA-to-lysine ratio of 60%. The surface response analysis suggests a similar TSAA-tolysine ratio of 59% for overall F/G.; Swine Day, 2004, Kansas State University, Manhattan, KS, 2004
Highlights
Previous research at Kansas State University has demonstrated that titrating the requirement for lysine and an amino acid of interest allows for the accurate determination of the optimum ratio of amino acid to lysine
In diets evaluating increasing TID lysine, methionine & cysteine ratios were 64 to 66% of lysine; and in diets evaluating increasing total sulfur amino acids (TSAA), diets were formulated to 1.10% TID lysine
As TSAA concentration increased to 0.61%, feed efficiency numerically improved (P = 0.16)
Summary
Previous research at Kansas State University has demonstrated that titrating the requirement for lysine and an amino acid of interest allows for the accurate determination of the optimum ratio of amino acid to lysine. With the increasing cost competitiveness of synthetic amino acids, there has been interest of supplementing swine diets with synthetic methionine and other amino acids. Research at the University of Missouri has shown that the optimum TID ratio of TSAA to lysine ranges from 58 to 62% to maximize ADG for gilts weighing 100 to 150 lb. Our objective was to determine the ADG and efficiency response to TSAA and lysine to estimate the TID TSAA-to-lysine ratio for barrows and gilts weighing 73 to 134 lb
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