Abstract
Numerous researchers hypothesized that testosterone had a "double-edged sword" effect, encouraging the development of secondary sexual features which are thought to be a healthy signal, while also suppressing immunological function. The relationship between external appearance of birds and its immune performance was little approached. The relationship between sex hormones, immune response and productive performance of males and females broiler were evaluated in this work. One day old chicks were sexed and chicks of each sex were randomly distributed into three experimental treatments, 1. TAM20 treatment chicks were supplied with estrogenic antagonist tamoxifen citrate at a dose of 20mg/kg body weight through oral administration; 2. Androgen treatment chicks were injected intramuscularly with synthetic veterinary androgen (Boldenone Undecylenate 50mg) at a dose of 1cm/ 10kg body weight and 3. The control treatment. Tamoxifen and androgen supplementation had no significant effects on final body weight, weight gain, or feed conversion ratio (at 45 days), although the androgen treatment had the significantly highest feed intake and the TAM20 treatment had the lowest. Moreover, differences between males and females for final body weight, weight gain, feed intake and feed conversion ratio were not significant. Androgen injection increased breast percentage significantly compared to TAM20 treatment and numerically compared to control treatment. Also, Androgen supplementation increased significantly comb percentage; however TAM20 decreased it significantly compared to control. Concerning the effects of both treatments on level of sex hormones, androgen showed favorable effects on both testosterone and estrogen when compared to Tamoxifen 20 treatment. On the other hand, administration of TAM 20 improves phagocytic activity as compared to androgen administration. Phagocytic index, productive performance, and carcass traits did not substantially associated with either testosterone and or estrogen blood levels.

Key words: Synthetic androgen, Tamoxifen, Estrogen, Testosterone, Phagocytic index, Performance