اثرات مكمل اسيد اسكوربيك و تراكم مواد مغذي جيره روي عملكرد جوجه هاي گوشتي نر در معرض تنش گرمايي

Effects of dietary supplemental ascorbic acid and nutrient density of diet on the performance of male broilers exposed to heat stress

The effect of dietary supplemental ascorbic acid (AA) and nutrient density on the male broilersʹ response exposed to heat stress, a diurnally cyclic temperature (24-38-24 °C), was investigated in this study. A 3 <6 factorial arrangement in a completely randomized block design was used. Factors involved in the experiment were three levels of dietary supplemental ascorbic acid (0, 200 and 400 ppm) and six kinds of diet with different nutrient density (I-very low energy-medium protein diet, 2-low energy-medium protein diet, 3-medium energy-medium protein diet without fat, 4-medium energy-medium protein diet with fat, 5-medium energy-high protein diet, and 6-high energy-high protein diet). Each treatment was tested with three replicate cages of 9 birds. Experimental period was from 2 to 8 weeks of age. The effects of ascorbic acid and diets on body weight gains (BWCi), feed conversion (FC), feed intake (Fl) and carcass quality (including: relative weights ofʹ carcass, visceral, abdominal tat pad and gall bladder and liver) were investigated. The results could not indicate any significant differences in BWG, FC and Fl between different levels of AA. However, there were significant differences between the diets (P<0.05). The highest and the lowest E3WG were related to High Energy- High protein and Very Low Energy-Medium protein diets, respectively. The effect of various levels of AA on the carcass quality was significant only for abdominal fat pad percentage (p<0.05). Abdominal fat pad percentage showed a decreasing trend with increasing the levels of AA in the diets. The diets had significant effects on most carcass quality traits (P<0.05). As a consequence, the results of this study indicated that some increase in nutrient density of the diet can lead to a reduction in the adverse effects of heat stress on the performance of male broilers exposed to hest stress. The improvement in BWG achieved by the chicks fed Medium Energy-Medium Protein with Fat diet, compared to those fed Medium Energy-Medium Protein without Fat diet, confirms the findings of other workers in relation to the beneficial effects of dietary fat on the performance of broilers exposed to heat stress.