Effects of concentrate level and chromium-methionine supplementation on the performance, nutrient digestibility, rumen fermentation, blood metabolites, and meat quality of Tan lambs

Objective: This study was conducted to evaluate the effects of concentrate level and chromium-methionine (Cr-Met) supplementation on the growth performance, carcass characteristics, meat quality, and fatty acid composition of Tan lambs. Methods: Sixty male Tan lambs (21 +/- 1.23 kg body weight) fed a finishing diet (concentrateto-forage ratio: 35:65 [LC group] or 55:45 [HC group]) with daily Cr-Met supplementation (0, 0.75, or 1.50 g) were used in a completely randomized design with a 2x3 factorial arrangement of treatments. Results: Lambs from the HC group had higher average daily gain, dry matter (DM) digestibility, dressing percentages, leg proportions, intramuscular fat (IMF) contents, and saturated fatty acid levels, but lower feed conversion ratios, globulin (GLB) and total protein (TP) concentrations, shear force, and monounsaturated fatty acid (MUFA) levels (all p<0.05). Cr-Met supplementation increased the DM digestibility, GLB and TP concentrations, rack and loin percentages, and cooking loss, but decreased the IMF contents and leg proportions (all p<0.05). Cr-Met supplementation at 0.75 g/d increased the conjugated linoleic acid (CLA) content in both the HC and LC groups (p<0.01). Significant interactions between the concentrate level and Cr-Met dosage were observed for MUFA (p<0.01) and polyunsaturated fatty acid (PUFA) (p<0.01) levels. Meat from the lambs fed an unsupplemented LC diet presented the highest PUFA and MUFA levels (p<0.01). However, the MUFA and PUFA levels decreased significantly with increasing Cr-Met supplementation levels in the LC group (p<0.01), whereas the opposite trend was seen in the HC group. Conclusion: The HC diet improved the growth performance of Tan lambs, increased their profitability by increasing leg and rack joint proportions, and improved meat quality by promoting an IMF content that was more visibly acceptable to consumers. Cr-Met supplementation at 0.75 g/d in a HC diet was the best choice and may be economically beneficial.