BACKGROUND: Heat stress reduces the poultry performance through physiologic changes. OBJECTIVES: This experiment was conducted to evaluate the effects of different levels of tryptophane on performance, carcass characteristics and some blood parameters of broiler chickens under heat stress condition. METHODS: Two hundred and fifty one-day-old broiler chicks (Ross 308) were used in a completely randomized design with four treatments and five replicates (pen), 10 birds in each replicate. The chickens of experimental treatments were fed basal diet (control group) and the diets plus the different levels of 100, 120 and 130 and 140% of the Ross strain tryptophane requirements. The experimental diets were used during the finisher period (day 25 to 42 of age) and under heat stress (32±1 ºC as cyclic from 9.00 AM to 5.00 PM). RESULTS: The results showed that the weight gain was  increased linearly by increasing the tryptophane level to 110% of Ross requirements but increasing the tryptophane level to 120, 130 and 140% caused the deteriorated weight gain (p<0.05). The feed conversion ratio was linearly decreased during the finisher and whole the period by supplementation of tryptophane to 110 and 120% but the higher tryptophane levels (130 and 140%) increased the feed conversion ratio during these two periods (p<0.05). Increasing the tryptophane level to 130% of Ross requirements caused a linear increase in the amount of lactate dehydrogenase, alanine amino transferase and alkaline phosphatase (p<0.05). Dietary supplementation of tryptophane had no effect on the blood urea, protein, creatinine, albumin, glucose and cholesterol at day 42 of age but triglyceride (p>0.05). Increasing the tryptophane level to 140% caused the lower blood triglyceride content (p<0.05). CONLUSIONS: Totally, the results of recent experiment show that consumption of 110 and 120% tryptophane of Ross requirements is the best level for performance improvements in broiler chickens under heat stress.

BACGROUNDS: Heat stress causes the lower performance in broiler chickens. OBJECTIVE: This research was conducted to investigate the effect of betaine supplementation in broiler chickens under heat stress condition. METHODS: Two hundred one-day-old male broiler chicks (Ross 308) were used in a completely randomized design with 4 treatments and 5 replicates per treatment and 10 birds per each replicate. The experimental treatments were the heat stressed birds fed the different levels of 0.0 (without any dietary supplement), 0.05, 0.1 and 0.2% betaine. The experimental diets were added to the diets during the finisher period (day 25 to 42 of age) and under heat stress condition (32±1º C from 9.00 AM to 5.00 PM). RESULTS: The results showed that feed consumption was not affected by betaine supplementation. Consumption of 0.2% betaine resulted in a higher weight gain during the whole period as compared to 0.05 betaine and control diet (P<0.05). The consumption of all betaine levels caused the decreased feed conversion ratio during the finisher period (P<0.05) and 0.2% betaine resulted in lowest feed conversion ratio between the experimental treatments. Dietary betaine supplementation had no effect on internal organ weights of heart, liver, abdominal fat, spleen and bursa at day 42 of age (P>0.05). Furthermore, consumption of different betaine levels had no effects on blood indices, the amounts of blood enzymes and antioxidant status at day 42 of age (P>0.05). CONCLUSIONS: Totally, the consumption of 0.2% betaine improves the performance without any effects on blood indices and internal organs under heat stress condition.

BACKGROUND: The application of medicinal herbs with high anti-oxidant properties could reduce the detrimental effects of oxidative stress and free radicals under heat stress and improve the performance of broilers. OBJECTIVES: The effects of rosemary powder and extract on growth performance, carcass characteristics and blood parameters of broilers were evaluated under heat stress. METHODS: For studying the effect of experimental treatments including control, different levels of rosemary powder (5, 10 and 15 g/kg), rosemary extract (3.5,7 and 10.5 g/kg) and Vit-Asp (1 g/L) on growth performance (feed intake, body weight and feed conversion ratio), carcass characteristics and blood parameters (cholesterol, triglyceride, hematocrit, glucose and heterophil to lymphocyte ratio), 160 one-day old chicks (Ross male-308) were used applying a randomized complete block design with 8 treatments, 4 replicates and 5 chicks per replicate during a 42-day period. Heat stress schedule was 32±2ºC as cyclic from 10.00 AM to 6.00 PM. RESULTS: Rosemary had significant effects on feed intake and final live weight of chicks (p<0.05) but not on feed conversion ratio (p>0.05). Significant effects from rosemary on glucose and heterophil to lymphocyte ratio were found (p<0.05). The effects of rosemary on carcass characteristics, cholesterol, triglyceride and hematocrit were not significant (p>0.05). CONCLUSIONS: In general, inclusion of rosemary in broilers diet under heat stress improved the performance because of anti-oxidant effects.Keyword: Rosemary, performance, blood parameters, heat stress, broilers