Effects of 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester on growth and blood components in growing Holstein steers.

Twenty-four Chinese Holstein growing steers were randomly divided into three groups and fed a diet containing 0 (the control group), 15 (treatment I group, or TG1) or 25 (treatment II group, or TG2) g/day 2-hydroxy-4-(methylthio) butanoic acid isopropyl ester (HMBi). Compared with the control group, the final body weights, total gains and average daily gains in the treatment groups increased (P < 0.01). The concentration of total protein (TP) for TG1 increased (P < 0.01). The levels of albumin in TG1 were higher than those in TG2 and the control group (P < 0.05). The concentration of alanine aminotransferase (ALT) in TG2 increased (P < 0.05), but concentrations of aspartate aminotransferase (AST) in the treatment groups decreased (P < 0.05). HMBi improved the concentrations of selenium in both TG1 (P < 0.05) and TG2 (P < 0.01). The levels of glutathion peroxidase (GSH-Px) in TG2 were higher than those of the control group (P < 0.05). Moreover, HMBi increased the concentrations of growth hormone (GH) in both TG1 (P < 0.05) and TG2 (P < 0.01). These results indicate that the addition of HMBi increases growth performance, serum concentrations of GH and AST; 15 g/day HMBi increases concentrations of total protein and albumin, and 25 g/day HMBi increases concentrations of ALT and GSH-Px.