Effect of particle size of chromium-methionine supplement on growth performance, carcass traits and meat quality in broiler chicks under physiological stress

This study was conducted to evaluate the effects of particle size of chromium-methionine (Cr-Met) on growth performance, carcass traits and meat quality of broiler chicks under physiological stress conditions. A total of 288 broiler chicks (male) were used in a 2 × 3 factorial arrangment with two stress status (no stress, stress) and three levels of Cr-Met (no Additive, 2000 ppb of Cr-Met, and 2000 ppb of Cr-Met milled) in a completely randomized design with six treatments, four replicates and 12 birds per each pen. Dexamethasone was added to diets (1.5 mg/kg diet) for a week (18-24 d) to induce physiological stress. Feed intake and body weight were measured weekly and feed conversion ratio was calculated. The malondialdehyde content and the water holding capacity of meat were measured at 24 and 46 d of age. Also, breast meat pH was measured at 46 d. Physiological stress decreased feed intake, weight gain, carcass yeild, relative weight of spleen, bursa, heart and liver, but increased FCR and water holding capacity of meat bereast (P<0.05). In stressed birds, both forms of dietary Cr- Met improved FCR and increased the meat pH (P<0.05). There were no differences between the effects of particle size of Cr-Met on the studied parameters. According to the results of this experiment, dietary supplementation of 2000 ppb Cr-Met in different sizes reduced the negative effects of physiological stress and improved the FCR and carcass yield of birds under physiological stress.