Influence of supplemental chromium on concentrations of liver triglyceride, blood metabolites and rumen VFA profile in steers fed a moderately high fat diet

This study evaluated the effects of supplemental Cr on liver triglycerides and blood metabolites in Holstein steers fed a moderately high fat (approxi mately 5.6% of dry matter) diet. Fourteen Holstein steers were blocked by B W and randomly assigned to a basal diet (control) or control diet supplemen ted with 0.8 mg/kg of Cr as chromium picolinate. Supplemental Cr had no eff ect on dry matter intake, average daily gain, serum glucose, insulin, chole sterol, and molar proportions of ruminal volatile fatty acids (VFA). Steers fed the diet supplemented with chromium picolinate had smaller concentrati ons of serum triglycerides at wk 3, plasma beta -hydroxybutyrate concentrat ions at wk 6, and liver triglycerides at wk 9. An in vitro mixed ruminal mi croorganism fermentation study was conducted to examine the effect of Cr on in vitro VFA production. Ruminal fluid from animals fed fescue hay and 1.1 kg of concentrate twice daily was added into a mixture containing 5 g of c oncentrate diet formulated to contain one of five concentrations of Cr (0, 0.2, 0.4, 0.8, or 1.6 mg/kg of Cr). The culture was incubated for 12 or 24 h. The molar proportion of propionate decreased, whereas butyrate and isobu tyrate increased linearly with increasing Cr content at 12 h of incubation. Molar proportion of valerate alone increased linearly with increasing Cr c ontent at 24 h of incubation. A second in vitro study evaluated the supplem entation of Cr at concentrations of 0, 0.8, 1.6, 3.2, 6.4, 12.8, or 25.6 mg /kg. Molar proportions of acetate, propionate, and isovalerate, and total V FA production responded quadratically with increasing Cr content at 24 h. R esults suggest that supplemental Cr may alter systemic lipid metabolism. In vitro fermentation altered VFA production with graded concentration of Cr and was not toxic to ruminal microorganisms at concentrations up to 25.6 mg /kg.