This study sought to investigate the short-term effects of bovine growth hormone (GH) and β-adrenergic agonist (βA), on lamb liver and muscle, particularly protein and energy metabolism. Wether lambs (120 d old) were all fed a high protein/energy diet ad libitum, with the GH group (n = 10) receiving a single subcutaneous injection of bovine GH (Posilac, Monsanto, 3.75mg/kg BW) on d 1; the βA group (n = 10) receiving βA (cimaterol) at 10mg/kg in the feed, whereas the control group (C, n = 11) only had ad libitum feed. After 6 d sheep were slaughtered blood was collected, plasma immediately prepared, and subsequently analyzed using Metabolon’s biochemical platform technology. Samples of Longissimus dorsi (LD) and Supraspinatus (SS) muscles were snap frozen in liquid nitrogen and stored at −80°C until analysis, the remaining carcass was incinerated. From extracted total RNA first strand cDNA was generated using random primers. Gene expression was determined by quantitative RT-PCR analysis relative to total cDNA, as measured using oligreen. Protein expression was determined by Western blot. Treatment groups were compared by one-way ANOVA (Genstat) and post hoc Dunnett’s test. Although there were no significant effects of βA and GH in body weight of lambs (P = 0.122), βA, but not GH, significantly increased the weights of both SS (P < 0.01) and ST (P < 0.05). In the blood, GH significantly increased the concentration of more fatty acids than βA (P < 0.05), both GH and βA significantly decreased certain plasma amino acids (P < 0.05). Treatment with βA, but not GH, increased mRNA expression of genes involved in glycolysis (P < 0.05) and the serine synthesis pathway (P < 0.05) in both SS and ST, but decreased expression of genes in the TCA cycle (P < 0.05). Effects on the serine pathway were confirmed as protein levels for PHGDH were significantly increased with βA (P < 0.001). It appears that GH and βA have differential effects on metabolism that lead to differential effects on muscle mass over this short time frame. Treatment with GH has wider effects on whole body metabolism, while βA appears to have more specific effect on both muscle metabolism and its growth.