نریمان میراعلمی

Antibiotics have been widely used in animal production for decades to promote growth. Although there is a trend toward reducing antibiotics in diets and now in Europe new laws have been passed to ban their use. As a result, economically important diseases such as enteritis necrosis (NE), which is caused by Clostridium perfringens in chickens, have become more prevalent. The alternatives to antibiotic growth promoters could affect gut health and performance by their impact on intestinal microflora. The purpose of this experiment was to compare the efficacy of some feed additives as alternatives to antibiotic for preventing of subclinical necrotic enteritis in broilers.

The study was conducted using 336 one-day-old male broiler chicks in a completely randomized design with 7 treatments, 4 replicates and 12 chicks per replicate. The treatments included: 1) Negative control (NC, corn-soybean meal-based diet without any feed additive); 2) Positive control (PC, diet containing wheat and fish-meal without any feed additive); 3) Antibiotic (PC diet + zinc-bacitracin); 4) Probiotic (PC diet + probiotic); 5) Prebiotic (PC diet + prebiotic); 6) Phytobiotic (PC diet + phytobiotic); and 7) Organic acid (PC diet + organic acids).

The results indicated that addition of antibiotic or its alternatives to the PC diet did not affect average daily feed intake, average daily gain, feed conversion ratio and relative weight of internal organs (p>0.05). Evaluation of cecal bacterial population at d 41 showed that chickens were infected by subclinical necrotic enteritis. The count of Clostridium perfringens was significantly lower in broilers fed either phytobiotic or antibiotic than in broilers recieved either NC or PC treatments. Broilers fed probiotics, prebiotics or organic acid in their diet had lower counts of Clostridium perfringens in cecal contents than those fed PC diet (p<0.05), however the difference was not significant when compared to NC treatment (p>0.05).

According to the sampling results on days 29 and 41, addition of phytobiotic compared to antibiotic, increased the number of lactobacilli while reduced the count of Clostridium perfringens and coliforms. Therefore, phytobiotic can be a suitable alternative for antibiotic to promote gastrointestinal health and prevent subclinical necrotic enteritis in broilers.

A total of 130 Arian broiler chicks were used in this study in order to assess the effects of tryptophan, melatonin and dark regimes on the performance and blood parameters of chickens exposed to heat stress. The chicks were allocated to the experimental units in an unbalanced completely randomized design. The treatments were control group, 40 mg of melatonin per kg of diet from 30-40 days of age and 0.04% of tryptophan per kg of diet from 10-40 days of age and dark period from 10-40 days of age. All treatments were daily exposed to heat stress (39±1C°) for 6 hours from 35-40 days of age. Minimal weight gain was achieved in the third weeks of age and the birds that received tryptophan treatment have highest weight in fourth weeks of weights (P<0.05). The highest level of high density lipo-protein related to tryptophan and melatonin treatments at 40 days (P<0.05). The level of T3 in darkness treatment at 35 days and TBARS level in darkenss and melatonin treatments were decreased (P<0.05). Results of this experiment showed that melatonin supplementation however of its usage after 30 days but had better influence in performance and blood parameters such as increased levels of high density lipoprotein protein and lower of thiobarbituric acid.

Immunoster prebiotic was studied in 0، 2، 4 percent levels with the purpose of survey of weigh and lenght features and variability of blood leukocytes of Kutum fingerling with initial weight of 0. 35±0. 02gr in a period of 8 weeks. The experiment was performed with use of random design in one control group and two experimental treatments with 3 replicates and with 150 fingerlings in each tank. Feeding was varied from 15% to 20% of fish biomass. At the end of experiment، although weight and length average had no significant difference between control and experimental treatments (P > 0. 05)، but positive and significant difference was observed in differential specification of leukocytes (P ≤ 0. 01). Therefore، by increasing Immunoster levels in diet، the lymphocyte percent increased and respectively the monocyte، neutrophil and eosinophil percent decreased significantly. As، the Immunoster 4% level had highest lymphocyte and least monocyte، neutrophil and eosinophil (P ≤ 0. 01). The obtained results were showed that the study levels of Immunoster prebiotic didn''t have considerable effects on growth performance in Kutum fingerlings، while it was able to play a positive and significant influence as an immunostimulant on blood leukocytes and increasing lymphocyte as an important cellular specific immune index.

One hundred eighty broiler chicks (Ross 308) from 1 to 42 days of age were used in this experiment in order to investigate the effect of dietary inulin and chicory root (Cichorium intybus L.) supplementation on the growth performance and intestinal microflora. Six dietary treatments with 3 replicates each (10 bird per replicate) were allocated to the chicks in a completely random design. The dietary treatments were: 1, 2) two control groups with 2 and 4% of filler (rice hulls as filler); 3, 4) two levels of dried chicory root (2 and 4% of the diets); 5) an antibiotic group (0.1% of virginiamycin) and 6) an inulin group (1% of the diet). Based on the results of this study, the highest and lowest weight gain were belong to inulin group and control group with 2% filler, respectively (P<0.05). Control group with 4% filler and antibiotic group had the highest and lowest amounts of feed intakes, respectively (P<0.05). Inulin and antibiotic supplemented groups had the lowest feed conversion ratio which was statistically significant compared to the other groups (P<0.05). The highest feed conversion ratio was related to the control group with 4% filler. On day 42, the relative weights of carcass and carcass components were not affected by the dietary treatments (P<0.05). At this age, the highest and lowest numbers of E. coli were related to the control group with 4% filler and 4% chicory group, respectively (P<0.05). There was no significant difference (p>0.05) between antibiotic and 2% chicory groups in the numbers of lactobacillus but the differences with the other groups were significant (P<0.05). The lowest numbers of lactobacillus was related to the control group with 4% filler.

The objective of this study was to investigate the effect of different levels of benzoic acid on performance and carcass characteristics of broiler chickens. To this purpose 120 one-day-old Ross 308 chickens were examined with a completely randomized design with 4 treatments, 3 replications and 10 sub sampling that were reared for 42 days. Dietary treatments included of the 0, 0.25, 0.5 and 1 percent levels of benzoic acid. Properties were measured included weight gain, feed intake and feed conversion rate. Dietary supplementation of benzoic acid significantly decreased feed intake of chickens (P<0.05) and the highest feed intake observed in control group. There was no significant difference between BA0.25 and BA0.5 groups in terms of body weight gain (P>0.05). Supplementing 1% benzoic acid in the diet resulted in significant decrease in body weight gain (P<0.05). Use of 0.25 and 0.5percent benzoic acid in the broilers diet in contest of control group significantly decrease FCR (P<0.05). Also inclusion of benzoic acid in the diet resulted in significant decrease breast to carcass weight ratio in 0.5percent treatment (P<0.05) but thigh to carcass weight ratio significantly increased in the treatment of 0.5 percent of benzoic acid than control group. Regarding to present results, suggested that use of 0.5 percent dietary supplementation of benzoic acid in broiler chickens is possible without negative effects on performance and carcass characteristics.

Current experiment was conducted to investigate the effect of propylene glycol supplement (PG) and calcium salt long chain fatty acids (Ca-LCFA) on milk production and blood metabolites of dairy cows. A change over design with 2×2 factorial arrangement including 2 levels of PG (0 and 450 gram/day) and 2 levels of Ca-LCFA (0 and 2.5%) were applied. Treats were recorded on 8 Holstein dairy cows in 4 different periods. The results showed that there was no significant interaction between PG and Ca-LCFA on recorded treats. The concentration of blood glucose increased significantly after using PG in the diet (P<0.05). The blood betahydroxy butirate (BHBA) content decreased significantly after using PG in the diet. Using PG had no significant effect on blood concentration of triglyceride, urea nitrogen (BUN) and cholesterol. In addition PG supplement had no effect on dry matter intake, milk yield, protein, lactose and fat percentage of milk, milk dry matter content and milk solid not fat (SNF). Using Ca-LCFA had no significant effect on blood concentration of BUN, glucose, triglyceride and BHBA, but the blood cholesterol content were significantly increased when Ca-LCFA was used. Ca-LCFA has also no effect on milk yield, protein, lactose and fat percentage of milk, milk dry matter content and milk solid not fat (SNF). In addition Ca-LCFA reduced dry matter intake.