BACKGROUND: Reducing the protein and amino acid content of diet or altering the dietary electrolyte balance were suggested as the effective strategies to prevent the harmful effects of the heat stress in poultry.OBJECTIVES: This study surveyed the effects of various levels of threonine and dietary cation-anion balance on the broiler chickens under the heat stress conditions.METHODS: 700 one-day-old male broilers (Ross 308) were used for 6 weeks under high- temperature conditions. This experiment was conducted using a 2 × 3 + 1 factorial experiment based on a completely randomized design, with 7 treatments (5 replicates per treatment and 20 birds per replicate). Experimental factors included two threonine concentrations (recommended level and 10 % above recommended level) and three dietary electrolyte balances (175, 250, and 325 mEq/kg). The control group considered the treatment with a normal threonine concentration (recommended level) and a dietary electrolyte balance of 250 mEq/kg under optimal temperature conditions.RESULTS: Although there was no interaction between threonine level and electrolyte balance, the electrolyte balance of 175 meq/kg increased the performance index compared to the electrolyte balance of 250 or 325 mEq/kg (P<0.05). The villus height to crypt depth ratio and villus surface area in the jejunum improved with an electrolyte balance of 175 or 250 mEq/kg (P<0.05). A decrease in the dietary electrolyte balance increased in the nitrogen-corrected apparent metabolizable energy (P<0.05). Besides, an increase in the population of lactobacilli and bifidobacteria in the cecum, as well as an increase in protein digestibility, were observed by increasing levels of threonine in the diet (P<0.05).CONCLUSIONS: Based on these results, a high level of threonine or a low electrolyte balance in diet (175 mEq/kg) may improve the performance, metabolizable energy, and intestinal microbial flora of broilers reared under heat stress.

BACKGROUND: Optimal levels of minerals in the diet are crucial for improving performance and immune response against the environmental stresses.OBJECTIVES: This study was conducted to evaluate the effects of water supplementation of chelated trace mineral (CTM) on growth performance, hematology, blood biochemistry, antioxidant status, and antibody response in broilers reared under heat stress condition.METHODS: A total of 240 male Ross 308 broiler chickens were randomly allocated into one of the following five treatments (each consisting of four replicates): (1) positive control (PC; thermoneutral condition), (2) negative control (NC; heat stress condition), (3) low-CTM (NC + low CTM level in tap water), (4) medium-CTM (NC + medium CTM level in tap water),  and (4) high-CTM (NC + high CTM level in tap water). The CTM levels in the tap water for the low-CTM treatment were 0.1, 0.15, 0.3, 0.4, and 0.45 mg/bird/day on days 1-10, 11-20, 21-30, 31-40, and 41-50, respectively. The respective values were 1.0, 1.5, 3.0, 4.0, and 4.5 for the medium-CTM, and 10, 15, 30, 40, and 45 mg/bird/day for the high-CTM water.RESULTS: The average weight gain during the whole experimental period in the medium-CTM treatment was higher compared to that in the negative control treatment, but lower than that in the positive control treatment (P<0.05). The heterophil/lymphocyte ratio and total antibody titers against Newcastle disease in the medium-CTM and high-CTM groups were similar to those of the broilers in the PC group, yet better (P<0.05) those of the NC group. The serum superoxide dismutase activity was also higher (P<0.05) in the high-CTM group compared to that of the NC group.CONCLUSIONS: The results suggested that the water supplementation of CTM at a moderate level (1.0, 1.5, 3.0, 4.0, and 4.5 mg/bird/day during different rearing periods) could be a strategy to ameliorate the detrimental effects of heat stress in broilers.

BACKGROUND: There are different kinds of phytase from different sources used in poultry nutrition.OBJECTIVES: The present study aimed to evaluate the effects of addition of 2 sources of 6- phytase to the diet of male broilers in terms of growth performance, Tibia biometric, breacking straight, mineralization, blood biochemical parameters, and carcase yield.METHODS: Herein, we recruited 216 1-d-old male Ross broilers and divided them to three experimental groups and six replications for 42 D. The treatment (T) diets included: T1 (without phytase (control)), T2 (supplemented with 500 FTU/kg diet of Aspergillus niger phytase (fungi phytase)), T3 (supplemented with 500 FTU/kg diet of phytase produced by a genetically modified strain of Aspergillus oryzae by doner Citrobacter braakii gene (genetically modified phytase)).RESULTS: Serum P in the birds supplemented by genetically modified phytase was higher compared with that in the control birds (P<0.05). Additionally, Tibia P in this group was higher than that of birds supplemented by fungi phytase (P<0.05). However, Tibia breaking straight in birds supplemented by genetically modified phytase did not differ significantly with those fed with a diet with fungi phytase. Meanwhile, Tibia breaking straight in birds supplemented by genetically modified phytase was higher than control (P<0.05). Growth performance, Tibia length, diameter, ash, Ca, dry weight, average serum HDL, Triglyserid, Cholesterol, Ca, Alkalin phosphatase, Glucose, Total Protein, and Carcase yeild were not significantly different among any of the treatments.CONCLUSIONS: Supplementation of male broilers diet with genetically modified phytase (500 FTU/kg), without any differences in terms of performance, could increase P of serum, P of Tibia and breacking straight of Tibia compared to supplementation diet with Aspergillus niger phytase.

BACKGROUND: Phosphorous is an essential nutrient for poultry. Receiving too much phosphorous by livestock and excretion of excess phosphorus, can lead to environmental pollution. OBJECTIVES: Determining the ileal and total tract digestibility of phosphorus and calcium in di-calcium phosphates produced in Iran. METHODS: A total of 720 day-old male Ross 308 broilers were randomly divided into 8 treatments with 6 replicates of 15 birds in each. In control treatment phosphoric acid was used as a source of phosphorus. The other dietary treatments included one of the seven domestic samples of di-calcium phosphates (A to G). Chromium oxide was used as a marker in the diets. On day 21, after collecting of feces, all birds were slaughtered via neck dislocation. Then, the last one-third of ileum was removed. The contents of the intestine were collected for each replicate and after drying were sent to the laboratory to determine the chromium oxide, phosphorus, and calcium amounts. Percentage of ileal and total tract digestibility of phosphorus and calcium for each sample were calculated separately. RESULTS: The effect of type of di-calcium phosphate samples in feed on ileal and total tract digestibility of calcium and phosphorus was highly significant (p < /em> < 0.001). Ileal digestibility in control was 69.8 percentage, while the lowest was observed in the E and F samples, and the highest value was related to sample A. Digestibility for phosphorus in control diet was 53.4 percentage throughout gastrointestinal tract. The lowest amounts of total tract digestibility of phosphorus were observed in treatments E and F, respectively, while the highest total tract digestibility was related to treatment A with 47.9 per cent. CONCLUSIONS: It could be concluded that ileal digestibility is more accurate in evaluating phosphorus bioavailability and sample A had the highest biological value, while the lowest was related to the samples E and F.

BACKGROUND: Using commercial antioxidants in the diet of chicken may cause cancer, liver swelling and changes in the activity of enzymes, hence their use is limited. Alternative herbal materials with antioxidant and antimicrobial properties can increase palatability, improve gastrointestinal function, improve the immune system and the performance of birds. OBJECTIVES: The purpose of the experiment was to study the effect of pomegranate peel extract (PPE) to a soybean oil diet on broiler performance and other related parameters. METHODS: This research was conducted as completely randomized design arranged in a 2×2×2 factorial experiment using pomegranate peel extract (PPE), antioxidant Nutriad® (AN) and soybean oil (SO). Three hundred and twenty 11 day-old Ross 308 broiler chicks were assigned to eight treatments of four replicates each (ten chicks per replicate). Data were analyzed using the GLM procedure of the SAS software, and the LSM of groups compared at 5% significance level. RESULTS: Soybean oil increased growing and overall feed conversion ratio (FCR) and harmful gastric micro flora. The overall ADG and feed intake were increased by PPE. Inclusion of PPE in the diet had no effect on FCR. Inclusion of PPE in the diet increased nutrient digestibility, beneficial gastric micro flora, lactobacillus, and the antibody titer in 39-day broilers, whereas AN had no effect on any of the performance parameters and decreased the beneficial gastric micro flora. CONCLUSIONS: The overall results showed that PPE in fat and non-fat containing diets might have the potential to increase the daily gain by enhancing feed intake, nutrient digestibility, beneficial gastric micro flora and immune system of broilers with  no deleterious effect on overall FCR.

BACKGROUND: Outbreak and spread of bacterial infections resulted in increasing use of antibiotics which subsequently leaded to bacterial resistance to conventional antibiotics. Objectives: To evaluate the effects of organic acids (Selko-pH®), Probiotic (PrimaLac®) and Echinacea purpurea (EP) alcoholic extract on the immune system of the broiler chickens, a completely randomized design experiment was conducted over 120 one-day-old male broiler chicks (Ross 308) with 4 treatment groups that each treatment consisted of 3 replications with 10 birds in each pen. Methods: Groups were designed as follow: group one received organic acid constantly in drinking water (1:1000 v/v) until 14th day and then received 8 hours in a day consecutively (OA); group two received Probiotic (PrimaLac®) water soluble (by 14th day) and mix in the feed (until the end of the rearing period) (PM); group three received EP alcoholic extract in drinking water (1:1000 v/v) like organic acid group and group four were considered as control (received no feed additives). Results: All groups except the control increased the relative weight of the spleen and Bursa of Fabricius as lymphoid tissues; however, this increase was statistically significant only in the case of EP group (p≤0.001). Data of antibodies test against sheep red blood cells and heterophil to lymphocyte ratio also showed that all groups except the treatment of organic acid had significant differences in terms of specific and cellular immune responses (p<0.01). The data of total count of bacteria and also Lactobacilli bacteria in cecal’s content obviously showed that the number of Lactobacilli bacteria significantly increased in PM and OA treatments (p≤0.05). ConclusionS: Feed additives used in these experiments have the ability to improve the immune system.

BACKGROUND: Thyme extract has the antimicrobial and antioxidant components that can be useful for the broilers under heat stress condition. OBJECTIVES: This experiment was conducted to investigate the effects of Thymus vulgaris extract in comparison with some common feed additives on performance, blood biochemical parameters and antibody response in broiler chickens under heat stress conditions. METHODS: This study was conducted using 192 one-day-old male broiler chicks (Ross 308) in a completely randomized design with 8 treatments in 4 replicates and 6 chicks per replicate. Treatments were as follows: 1) basal diet + standard temperature conditions (positive control); 2) basal diet + heat stress conditions (negative control); 3) negative control + 200 mg virginiamycin; 4) negative control + 150 mg Protoxin probiotic, 5) negative control + 250 mg vitamin C, 6) negative control + 250 mg vitamin E, 7) negative control + 250 mg thyme extract, and 8) negative control +500 mg thyme extract per kg diet. RESULTS: Dietary thyme extract at the rate of 500 mg/kg as well as probiotic and vitamin E increased (P<0.05) body weight gain (2202, 2183 and 2199, respectively) and improved feed conversion (1.65, 1.74 and 1.66, respectively) compared with negative control group (body weight gain 1960 g and feed conversion ratio 1.96). Moreover, 500 mg/kg dietary thyme extract, probiotic and vitamin C reduced triglycerides, total cholesterol and low density lipoprotein during heat stress conditions (P<0.05). All dietary supplements groups significantly increased antibody titers against red blood cells as compared with negative control. CONCLUSIONS: In general, the results of the present study suggest that thyme extract at the level of 500 mg/kg of diet can be recommended as an alternative to the common feed additives to improve growth performance and health benefits of the heat-stressed broilers.

BACKGROUND: Although numerous reports support the beneficial effects of supplementing chromium (Cr) on broiler performance under normal and stress conditions, the optimal level has not been determined yet. OBJECTIVES: This study was conducted to investigate the effects of different levels of supplemental Cr on performance, cortisol, and thyroid hormones of broiler under normal and stress conditions. METHODS: A total of four hundred forty-eight broilers were used. Broilers allocated into 2×4 factorial experiment included: stress (normal and stress) and 4 levels of supplemental chromium (0, 1000, 2000, 3000 ppb) since day 18. A completely randomized design with 8 treatments and 4 replicates (14 birds per replicate) was used. Dexamethasone used as a stressor for one week (stress period, STP) then experiment continued to day 46 (recovery period, RCP). RESULTS: Feeding 1000 and 2000 ppb Cr improved feed conversion ratio (FCR) and increased T4 compared to 0 and 3000 ppb Cr in stressed broilers in STP (P<0.05). Feed intake (FI), body weight (BW) and T3 concentration were higher in broilers fed with 1000 ppb Cr in the diet and reared without stress in STP (P< 0.05). Despite the negative effect of stress on performance in RCP, dexamethasone-stressed broilers had better FCR. Feeding stressed birds with 1000 ppb Cr increased blood cortisol whereas it reduced cortisol in the normal-reared birds. CONCLUSIONS: The Dietary supplementation of 1000 and 2000 ppb Cr reduced deleterious effects of physiological stress. Moreover, 1000 ppb Cr improved FI and BW of broilers under normal condition at first week. Feeding high level of chromium under normal and stress conditions did not improve the performance.

BACKGROUND: Salmonella Enteritidis in poultry is one of the main causes of illness that can be controlled effectively by some plant compounds, antibiotics and probiotics. OBJECTIVES: This study compares the effect of rosemary, thyme, propolis, antibiotic and probiotic on the immune system and blood parameters of broilers challenged with Salmonella Enteritidis.  Methods: Four hundred and twenty 1-day- old male broiler chicks Cobb strain were divided into seven groups: including rosemary ethanol extract, ethanol extract of propolis, ethanol extract of thyme, and probiotics, virginiamycin (10%) and positive and negative controls, and were reared for 6 weeks. At the end of experiment chickens were sampled and slaughtered. RESULTS: The results showed that plant extracts with probiotics can improve the immune system, reduce serum lipids, reduce harmful bacteria such as Salmonella and E.coli and increase the beneficial bacteria such as lactic acid bacteria. CONCLUSIONS: This study showed that the herbal extracts and probiotics can be used as an alternative to antibiotics in broiler diets.

BACKGROUND: On account of the importance of iodine in the synthesis of thyroid hormones, different levels of dietary iodine can affect the occurrence of ascites syndrome in broilers.OBJECTIVES: The current research aimed to investigate the effects of different sources and levels of iodine on performance, carcass traits, ascites mortality, thyroid hormones, and serum biochemical parameters of broiler chickens under cold stress condition.METHODS: This experiment was performed using 375 one-day-old male broiler chickens in a completely randomized design with five treatments, five replications, and 15 birds per replication. To induce ascites, the room temperature was reduced to 15 °C from 14 days and this temperature was maintained until the end of the period. The experimental treatments included: control treatment (basal diet with iodine at the recommended level, 1.25 ppm), basal diet + potassium iodide (KI) with iodine levels (6.25 and 3.75 ppm), and basal diet + calcium iodate [Ca(IO3)2. H2O] with iodine levels (6.25 and 3.75 ppm).RESULTS: The effect of the treatments on the performance indices was not significant throughout the experiment. The lowest percentage of ascites mortality, heart weight, and triiodothyronine (T3) were observed in the treatment (6.25 ppm), which was significantly different from the control treatment (P<0.05). The lowest ratio of right ventricle to total ventricles (RV/TV) was related to potassium iodide treatment (6.25 ppm), which indicated tendency (P<0.10). Chickens receiving higher levels of iodine (6.25 ppm) had higher thyroxine than those receiving lower levels (3.75 ppm) (P<0.05) and showed a lower ratio of triiodothyronine to thyroxine compared to those (P<0.05).CONCLUSIONS: The results of this experiment implied that the use of higher levels of dietary iodine (6.25 ppm), especially as potassium iodide, reduces broiler’s ascites mortality under cold stress conditions.