Postruminal Lysine and Methionine Infussion in Steers Fed a Urea-Supplemented Diet Adequate in Sulfur

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Abstract
Postruminal usage of methionine by growing steer calves fed ground shelled corn, urea and cottonseed hulls adequate in S was studied by abomasal infusion of graded quantities of methionine with lysine adequate. A 6 .times. 6 Latin square of treatments was replicated where infusions provided lysine and methionine, respectively, in g/day: 0, 0; 24, 0; 24, 4; 24, 8; 24, 12; and 24, 12 plus 140 g sodium caseinate. Treatments were brought to volume in 2 l of water and infused continuously over 24 h. Responses measured were N retention, urea N in plasma and concentrations of free amino acids. Retention of N was increased in steers abomasally infused with lysine or lysine in combination with graded quantities of methionine. Infusion of 4, 8 or 12 g/day of methionine with constant lysine (24 g/day) did not alter N retained from lysine infused alone. Infusion of a lysine-methionine-sodium caseinate positive control raised N retention compared to no caseinate. Plasma lysine was higher in treatments where lysine was infused compared to the negative control. Methionine increased linearly with infusion of incremental quantities. Methionine was not limiting when infused postruminally with adequate lysine to growing steers fed the urea-supplemented diet with S adequate.