Abstract
o investigate the effect of thyroid hormones Thyroxine (T4) and Triiodothronine (T3) on bodyweight performance in broiler hens. Methodology: The hens were kept in a controlled environment of 50-60% humidity at 31oC in first two weeks than temperature been decreased to 24oC with 24 hr light cycle per day, and were treated gently. Water and feed were provided ad libitum for the all hens. The body weight of the birds detected at the day 2nd, 4th, 6th and 8th week of the experimental period and blood sample detected at the day 14th,28th,42th and 56th day of the experimental period. The data were analyzed by the analysis of variance technique in completely randomized design, while the differences between means were tested by Duncan New Multiple Range Test as per SAS. Results: It was noted that there is a highly significant effect of age, at the level (P ≤ 0.01) on the characteristics of each of the concentration of the hormone T3 and T4 hormone levels and body weight. This study showed that there is a difference in the average concentration of "T4 & T3" for meat birds of different ages. The correlation coefficient manner, "Pearson" between the different qualities of the birds of the meat where it was noted there is a strong inverse relationship between "T4 & T3". arabic 11 English 77