EFFECT OF ZINC ACETATE AND MAGNESIUM SULFATE DIETARY SUPPLEMENTATION ON BROILER THIGH MEAT COLOUR, NUTRIENT COMPOSITION AND LIPID PEROXIDATION VALUES UNDER CONTINUOUS HEAT STRESS CONDITION

Four hundred and fifty one-day-old male broiler chicks (Ross 308) in 9 groups of 50 each (3 Chi 3 factorial experiment) were randomly allocated to investigate the effects of different dietary levels of 0, 30 and 60 mg/kg Zinc (Zn) and 0, 300 and 600 mg/kg magnesium (Mg) on thigh meat colour, nutrient composition and lipid peroxidation value in broiler chickens under heat stress. The birds were kept under a high temperature (32 +/- 1 degrees C) for 24 h/day for the first until the final day. At the end of the experiment (day 42), five birds per treatment were slaughtered. Then two pieces of the right thigh muscle per bird (upper part of the thigh muscle) were immediately collected for assessing the meat quality indices. The results of the present experiment showed that addition of Zn and Mg did not influence the ash, dry matter (DM) and ether extract (EE) contents of thigh meat (P > 0.05), whereas the crude protein (CP) content of the thigh meat was increased when diet was supplemented with Zn (P < 0.05). Addition of Zn and Mg in diet did not change the mean lightness (L) and redness (a) value in the thigh meat (P > 0.05). Thigh yellowness (b) value was increased by inclusion of 30 mg/kg Zn alone or along with 600 mg/kg Mg (P < 0.05). Furthermore, inclusion of 30 mg/kg Zn in diet (at any level of Mg) decreased the thigh thiobarbituric acid reactive substances (P < 0.05).