51 Supplemental Lysine in Finishing Cattle Diets

Smartamine ML (Adisseo), a bioavailable (80%) source of lysine and methionine was used to evaluate effects of increasing lysine supply on performance of beef cattle. Crossbred steers (n=120, initial BW 261 kg) were individually fed a diet of 15% modified distillers grains plus solubles (MDGS), 68% blend of high moisture and dried rolled corn, 12% corn silage, and 5% supplement with Smartamine ML top-dressed daily. Steers were assigned to 8 inclusions of lysine, 0 to 7 g/d in 1 g increments, with 15 steers per treatment. Data were analyzed with MIXED procedure of SAS as a generalized randomized design with animal as experimental unit and treatment as fixed effect. Orthogonal contrasts evaluated linear, quadratic, and cubic responses. Contrast statements compared the control with 1, 2, and 3 g/d treatments. Feeding increasing amounts of bioavailable lysine linearly decreased DMI (P = 0.04), final live BW (P = 0.04), and ADG (P = 0.02) with no effect on G:F (P ≥ 0.27). Numerical differences in DMI and ADG (P ≥ 0.26) led to a trend (P = 0.06) for improved live G:F for the 1 g/d treatment compared with control (0.188 and 0.176, respectively). During the Optaflexx feeding period (d 163-195), DMI linearly decreased (P = 0.01) as lysine increased in the diet with no differences in ADG (P ≥ 0.13) or G:F (P ≥ 0.12), with a trend (P = 0.08) for improved live G:F for 3 g/d compared with control (0.163 and 0.131, respectively). Hot carcass weight tended (P = 0.07) to linearly decrease as Smartamine ML increased in the diet, with no effect on other carcass measures including longissimus muscle area, 12th rib fat, and marbling score (P ≥ 0.18). In finishing beef cattle diets with 15% MDGS, more than 3 g/d of supplemental lysine did not improve performance.