BACKGROUND: Stocking density is one of the most important problems in the poultry industry, which impair their production and welfare.OBJECTIVES: This experiment was done to evaluate the effect of organic selenium supplementation on the growth performance, blood metabolites, and the meat quality of broiler chickens in different stocking densities.METHODS: 216 one-day-old male broiler chickens (Ross 308) were used in 2×2 factorial arrangements by 2 stocking densities (7 and 15 birds/m2) and 2 levels of selenomethionine (0 and 0.4 mg/kg) in a completely randomized design with 4 treatments and 4 replicates.RESULTS: The feed intake (FI), and body weight gain (BWG) were significantly affected by the stocking density and selenomethionine (SE-MET) supplementation in the overall experiment (P<0.05). FI and BWG decreased and feed conversion ratio decreased in 15 bird’s density, while SE-MET inclusion improved these traits (P<0.05). Increasing stocking density increased the plasma glucose (P<0.05). Blood glutathione peroxidase and lymphocyte levels reduced at 15 bird’s density, while increased by 0.4 mg SE-MET supplementation (P<0.05). Increasing stocking density increased blood heterophil, while SE-MET inclusion decreased it (P<0.05). Meat pH and cooking loss were not affected by stocking density. Dripping loss (DL) increased, and water holding capacity (WHC) decreased at 15 bird’s density, but 0.4 mg SE-MET decreased DL and significantly increased WHC (P<0.05).CONCLUSIONS: It was concluded that increasing stocking density had the negative effects on the growth performance and meat quality of broiler chickens; however, the supplementation of 0.4 mg of SE-MET to diet can improve the growth performance, blood metabolites and meat quality of broiler chickens.

BACKGROUND: Lead (Pb) induced oxidative stress is known to suppress growth performance in broiler chickens. The current study was carried out in an attempt to describe the specific underlying mechanisms of such phenomenon. OBJECTIVES: The objective of this study was to investigate the effect of Pb-induced oxidative stress on performance, antioxidant status and behavioral responses of broiler chicken. METHODS: Eighty day-old broiler chicks were randomly assigned to 2 dietary treatment groups of 4 pen replicates, namely i) basal diet containing no lead supplement (control) and ii) basal diet containing 200 mg Pb/kg of diet. RESULTS: The results showed that addition of lead decreased body weight gain (p<0.01) and feed conversion ratio (p<0.01). Also, consumption of contaminated diet significantly increased MDA and H/L Ratio and significantly decreased SOD and GPx activity (p<0.01). Moreover, addition of 200 mg/kg diet significantly increased sitting pasture and aggression behavior and decreased feeding behavior (p<0.01).               CONCLUSIONS: Our data conclude that Pb-induced oxidative stress adversely suppressed feed conversion ratio and growth performance. The proposed underlying mechanism for such phenomenon is Pb-induced oxidative stress by impaired antioxidant status and feeding behavior decreased the growth performance.

BACKGROUND: Heat stress is very important in poultry production. OBJECTIVES: To evaluate the effect of oral elatoninsupplementation and increasing of dark period on biochemical profile of broiler chickens under Heat Stress (HS). ETHODS: A total of 200 day- old broiler (Arian) chicks were randomly allocated in to 4 groups (dark ,melatonin, negative and ositive controls). Melatonin group  received 40 mg melatonin/kg  diet from 30-40 days of age and chickens of dark group were xposed to  a  special lighting schedule from 10-40 days of age. All groups (except negative control) were daily exposed to HS (39± 1 c) for 6 hours per day from 35-40 days of age. At the end of 6 weeks, body weight was measured. At 30, 35, and 40 days, serum uric acid, glucose, total protein, albumin, globulin, activity of AST  and creatinine were measured.  atawas analyzed by ANOVA and Tukey test in SPSS software. RESULTS: In 30 days, there was no significant difference etween groups. In the day 35, only serum uric acid of melatonin group was significantly increased in comparison with egative control. Also, serum uric acid of melatonin group  increased significantly in 40 days in comparison with other roups, as melatonin plays an important role in the antioxidant defense system and uric acid is an important antioxidant inchickens. Serum glucose of positive control compared to other groups significantly increased in 40 days. Other biochemical parameters were not significant. In this study,the mean body weight of dark group was significantly decreased. The  percentage of mortality rate in negative control, dark, melatonin and positive control  treatments was zero, 4 ,5  and 10% respectively. CONCLUSIONS: These results demonstrate that  dark period and oral melatonin supplementation  candecrease HS.

BACKGROUND: The insoluble fiber content of poultry feeds is often considered as an unfavorable factor which reduces the nutritive value of diet. OBJECTIVES: The effects of barley hulls on performance traits of broiler chickens were evaluated. METHODS: The experiment was carried out using 200 Ross 308 broiler chickens in a completely randomized design with 5 treatments and 4 replicates. The experimental diets  consisted of a control hulls-free diet and four diets containing 0.75 or 1.5 percent barley hulls with particle sizes of less than 1 mm or between 1-2 mm. RESULTS: The dietary type did not affect feed intake of the experimental groups. In the whole the experimental period, the weight gain and feed conversion ratio in the broiler chickens feed, the diet that contained 1.5% barley hulls with 1-2 mm particle size improved compared to the control group (p<0.05). In the jejunum, fiber feeding resulted in an increased goblet cell number as compared to the control group (p<0.05). Unexpectedly, barley hulls feeding reduced the villi height compared to the control group (p<0.05). In jejunum the crypt depth in control birds was more than the treatment fed 1.5% barley hulls with less than 1 mm particle size (p<0.05). The ratio of crypt depth to villus height in control group was more than the birds fed the diet that contained 1.5% barley hulls with less than 1 mm particle size (p< 0.05). In ileum the chickens fed the control diet had more lactobacillus and less Escherichia coli than the majority of the treatment fed barley hulls. CONCLUSIONS: Inclusion of 1.5% barley hulls with particle size of 1-2 mm in diet improved performance traits of broiler chickens. On the other hand, using 1.5% barley hulls as a lignocelluloses source increased lactobacillus growth and reduced Escherichia coli population. This alteration in intestinal micro flora suggests a prebiotic effect for barley hulls in the gastrointestinal tract of broiler chickens.