Effect of Chromium Chelavite supplementation on the metabolism of glycogen and lipid in adult Merino sheep

Abstract

This experiment investigated the effect of exercise and chromium supplementation on muscle glycogen and subcutaneous fat metabolism. The design of the experiment was a 2×2 factorial with chromium and regular exercise as the treatments. Forty-three Merino wethers (2 years old) were maintained for 10 weeks on a diet based on barley and lupin grain fed at 2·2 times maintenance. The ration was supplemented with 0 or 1 mg/kg DM of chromium, as Chromium Chelavite amino acid chelate. For regular exercise the animals were worked at approximately 60% maximum whole body oxygen consumption for 2 h, 3 times per week, which increased the estimated weekly energy demand by about 9%.

Chromium increased the activity ofATP citrate lyase, a marker of the glucose-insulin axis, by 30%, but decreased the fat depth GR, the fat depth over the 12th rib, by 20%. There was no effect on the activity of acetyl CoA carboxylase, the major rate-limiting enzyme of lipogenesis. Thus the potential for glucose contribution to fat synthesis increased but the subcutaneous fat depth decreased, indicating that chromium may cause the redistribution of fat within the carcass due to changes in insulin sensitivity. The chromium treatment did not effect growth rate, carcass weight, or muscle glycogen concentration. Chromium supplementation tended to prevent a decline in the concentration of chromium in the kidney, caused by exercise. The level of exercise was only sufficient to cause a glycogen loading response in one of the muscle tissues sampled, the m. semimembranosis. Chromium Chelavite supplementation may be a useful tool for reducing the subcutaneous fat depth of mature ruminants, and may promote the redistribution of fat to other locations within the carcass.