Effect of adding organic chromium and L-carnitine to feedlot lamb's diet on performance, glucose metabolism and some blood parameters

Chromium (Cr) plays an important role in ruminant’s metabolism. Situations such as accelerating growth, stress and low bioavailability of Cr in feedstuffs, result in depletion of chromium stores of body, therefore, metabolic disorders and growth retardation occurs. In addition, L-carnitine (LC), a compound of lysine and methionine, is involved in many metabolic processes. It affects energy production and performance by influencing lipid metabolism. Using Cr and LC together, a positive interaction has been reported on lipids and carbohydrates metabolism in some species. Therefore, the aim of this study was to evaluate the effect of organic chromium in form of chromium methionine (Cr-Met) and L-carnitine as a dietary supplement for feedlot lambs on growth performance, glucose metabolism and some blood parameters.
Material and This experiment was performed for 60 days with twentyfour 3-4 month-old male lambs in a completely randomized design (CRD) with four treatments of six lambs each. The treatments were included: 1- control (basal diet) 2- treatment of chromium (Cr) (500 µg Cr per lamb per day) 3- treatment of L-carnitine (LC) (500 mg L-carnitine per lamb per day) 4- treatment of chromium and L-carnitine (Cr × LC) (500 µg Cr and 500 mg of LC per lamb per day). Supplements were added to the basal diet as topdress. At the end of experiment, feed intake, average daily gain (ADG) and feed conversion ratio (FCR) were calculated. In order to evaluate blood metabolites and rumen liquid parameters, blood and rumen liquid samples were taken at the end of experiment. Four lambs randomly were selected from each groups for intravenous glucose tolerance test (IVGTT). For this purpose, 0.5 ml/Kg BW dextrose (50%) was infused and blood samples were taken at 5, 10, 20, 30, 40, 60, 80, 100 and 120 min after glucose infusion, Then glucose clearance rate (CR), half-life (t1/2) and area under curve (AUC) was calculated.
Feed intake, ADG and FCR and also rumen volatile fatty acids and ammonium was not different between treatments (P>0.05). Interactions of chromium and L-carnitine for performance parameters and also rumen volatile fatty acids and ammonium were not significant (P>0.05). High density lipoproteins (HDL) in treatments two and four was significantly higher in compared to treatments three and one (P0.05). Activity of alanine aminotransferase (ALT) was lower in treatments three and four than treatments one and two (P0.05). Area under curve was lower in treatment three in compared to treatment one and four (P0.05).
Results of this experiments showed that, adding chromium and Lcarnitine to feedlot lambs diet (the concentrations used in this study) did not impact fattening performance, but resulted in an increase in HDL and improvement of glucose metabolism.