عنوان مقاله [English]
Background and objective: 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. Chromium is an essential element for animals and humans It functions as cofactor for insulin and it is assumed to be essential for activation of certain enzymes and stabilization of proteins and nucleic acids Therefore, impaired carbohydrate and protein metabolism, decreased insulin sensitivity in peripheral tissues and thereby decreased weight gain would be expected in Cr-deficient individuals especially under stressful conditions. Chromium improves health by reducing free radicals and also stimulates the immune system and makes the body more resistant to diseases during stress by lowering blood cortisol levels. The aim of this study was to investigate the Effects of chromium-methionine on growth performance, blood parameters and health of Holstein suckling calves under heat stress.
Material and methods: For this experiment, 30 newly-born Holstein calves (average age 1-8 days), average weight 39±1 kg) were used in a completely randomized arrangement with 2 treatments and 15 replications. The experimental treatments were: 1) Basal diet without any additive (control), 2) Basal diet with 0.05mg of chromium-methionine. Daily feed intake were recorded daily and body weight were recorded at birth days, 30, 60 and 65 breeding periods and feed conversion ratio was calculated for each group. The average maximum temperature–humidity index was 91.2 U, indicating severe environmental heat load.
Results: The results showed that the use of chromium methionine supplementation in calves under heat stress had not a significant effect on feed intake, final weight, daily weight gain, feed conversion ratio and skeletal growth during the first, second and entire breeding months. The blood concentration of glutathione peroxidase was affected by chromium methionine supplementation, while the blood concentration of glutathione in calves receiving chromium supplementation was 57.78 versus 47.19 u/g (P <0.04). Respiration rate, breaths/min and heart rate in calves receiving chromium were low, so that numerically the number of breaths and heart rate in chromium-methionine-supplemented calves was 50.50 versus 54.40 per minute and 10 / 98 were in front of 10/50 times. Rectal temperature and fecal score were not affected by chromium intake in calves.
Conclusion: Results of this experiments showed that the use of chromium methionine in suckling calves improved glutathione peroxidase concentration, fecal score and rectal temperature but had no effect on growth performance and skeletal size