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This research was aimed at estimating the effect of oral supplementation of Tamoxifen on productive efficiency, carcass characteristics, hormonal profile and gonadal structure of two broiler breeds. One hundred and eighty chicks of each breed of Avian48 and Arbor Acres were divided into three groups: control group; TAM10 group, supplied with 10 mg Tamoxifen/kg of body weight at 3, 5, 7 and 9 days of life; and TAM20 group, supplied at the same intervals with 20 mg Tamoxifen/kg of body weight. Both levels of Tamoxifen improved productive performance at early ages, but Arbor Acres produced better results with TAM20 levels than TAM10, while Avian48 breeds reacted adversely. On the contrary, Tamoxifen supplementation significantly decreased feed intake and feed conversion (after the first two weeks of life) compared to control with a higher level of decrease reported for TAM20 treatments than TAM10 and for Arbor Acres compared to Avian48 breed. Carcass traits were not affected significantly with Tamoxifen supplementation compared to control although Arbor Acres responded better to TAM20 and Avian48 for TAM10. With regard to the effect of Tamoxifen (TAM) on sex hormones, it could be concluded that TAM10 treatments showed a stimulating effect on the level of such hormones as compared with the TAM20 group with the most favourable results being clearly detectable in 42-day-old birds although both concentrations of Tamoxifen did not differ significantly from control. However, treatment of broiler chickens with Tamoxifen in different doses caused a gradual decrease in follicle production rate and eventually led to an increase of the atretic follicles in different stages of atresia. Finally, we can conclude that Tamoxifen supplementation can improve performance and carcass efficiency of broilers without changing the hormonal profile, however much research is required to estimate the best concentration required for each breed.

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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.

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