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.

Eight ponies were allotted to 2 groups of 4. Group-1 ponies (1-4) were given 0.2 g of indole/kg of body weight orally and group-2 ponies (5 to 8) were given 0.1 g of indole/kg. Various physical, hematologic, and physiologic measurements were obtained after administration of indole. Intravascular hemolysis and hemoglobinuria were detected in both groups within 24 hours of dosing. Hemolysis was reflected by decreases in PCV, hemoglobin concentration, and RBC count, and an increase in indirect bilirubin. Erythrocyte fragility appeared to increase in both groups at 8 hours after dosing and peaked at 16 hours after dosing. At 72 hours after dosing, the RBC fragility value was less than predose measurements. Heinz body formation was noticed in group-2 ponies, but not in group 1. Plasma indole concentrations increased in both groups from the nondetectable predose concentrations. Group-1 values were 203% of group-2 values. In group 2, plasma indole was nondetectable by 12 hours, whereas low concentrations could still be measured in the group-1 ponies at 24 hours. Ponies in group 1 died or were euthanatized between 24 and 72 hours after dosing, whereas group-2 ponies were euthanatized between 48 and 120 hours. At necropsy, all body fat, mucous membranes, and elastic tissue were stained yellow. Hemoglobinuric nephrosis was the most prominent microscopic lesion. Results of this study indicated that indole, a metabolite of the amino acid tryptophan, causes acute intravascular hemolysis in ponies.