The Effect of Different Levels of Rapeseed Meal with and without Enzyme on the Performance and the Serum Level of Triiodothyronine (T3), Thyroxine (T4) and Thyroid Stimulating Hormone (TSH) in Broiler Chickens

In order to investigate the effect of different levels of rapeseed meal on performance and content of triiodo-thyronine (T3), thyroxine (T4) and thyroid stimulating hormone (TSH) in broiler chickens’ blood, 640 1-d-old Ross male broiler chickens were studied through a 4 × 2 factorial arrangement including 4 levels of rapeseed meal (RSM) (0, 5, 10 and 15 percent) and two levels of enzyme (0 and 0.05%) with a completely randomized design and 4 replicates. Feed intake weight gain and feed conversion ratio were measured at 8, 21 and 42 days of age. In order to investigate the level of T3, T4 and TSH at the end of each period, three chickens from each treatment group were sampled for blood collection. Results indicated that different levels of RSM and enzyme separately had no significant effect on the feed conversion ratio, weight gain and feed intake (P≥0.05). However, the interaction effect of rapeseed RSM and enzyme significantly improved the feed intake (P≤0.05). Treatments significantly affected the amount of T3 and TSH in blood serum that was decreased, with adding rapeseed and enzyme into the diet, while the level of T4 was not affected significantly. Therefore, according to obtained results, it seems that rapeseed RSM can be used in the diet of broiler chickens up to 15% without decreasing their performance.