تاثیر ال-گلوتامین بر عملکرد رشد، فراسنجه‌های خونی، کیفیت لاشه و پاسخ ایمنی جوجه‌های گوشتی

Introduction: Glutamine constitutes approximately 30-35% of the total nitrogen derived from amino acids present in the blood. The role of glutamine as a 'nitrogen shuttle' helps to ensure the body against the poisonous impacts of high circulating levels of ammonia. Glutamine moreover has vital and special metabolic capacities as a vehicle for the exchange between tissues of carbon, as a fuel for rapidly dividing cells, and as a precursor for numerous naturally active molecules. Glutamine is a great example of how amino acids are used for various purposes in our body's metabolism and immune system. Glutamine, a conditionally essential amino acid, appears to be a key nutrient for the gut, since it could be a conspicuous source of vitality for enterocytes. Glutamine has been appeared to initiate improved intestinal secretory immunoglobulin A level which is vital for mucosal defense. Investigate has shown that the use of amino acid supplements in broiler diets improves performance and carcass characteristics. Glutamine is one of the most abundant amino acids in the blood plasma that plays a critical part in muscle structure, body tissue and body weight gain. Researchers found that 10 g/kg L-Gln addition to the diet increased weight gain and serum immunoglobulin A and G concentrations of broiler chickens. Therefore, an experiment was performed for 42 days of production to establish the effect of L-Gln on broiler growth performance, carcass quality and some blood parameters in broiler chickens.
Materials and methods: This study was conducted to investigate the effect of L-glutamine (Gln) on growth performance, carcass quality and some metabolites related to lipid metabolism in broiler chickens. The experiment was conducted using 300 one day old male Ross 308 broiler chickens in a completely randomized design with five treatments and five replicates from the age of 1 to 42 days. The experimental treatments included were: the addition of zero, 0.25, 0.5, 0.75 and 1% levels of L-glutamine in corn-soybean meal-based diets supplemented with dietary fat. During the experimental period, average daily feed intake (DFI), body weight gain (BWG), feed conversion ratio (FCR) were measured. At the end of the experiment, two birds were selected from each replicate and slaughtered after weighing, and the weight of the internal organs (weight of thigh, breast, heart, liver, gizzard, fat pad, pancreas, bursa, spleen and thymus) was measured. Blood samples were collected from two birds per replicate in order to determine the number of white blood cells (WBC), heterophil to lymphocyte ratio (H/L), two blood samples were taken from each experimental treatment from the jugular vein in tubes without anticoagulant and then centrifuged (2000×g for 10 min) to obtain serum. Serum cholesterol (total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL)), triglycerides were determined colorimetrically on the 42nd day of rearing.
Results and discussion: Average daily feed intake (Table 2) shows that it was significant in the grower period for L-Gln supplemented group. Feed consumption was not affected by different levels of L-Gln except during the grower period. The effect of using different levels of L-Gln on body weight in the starter period was significant for the addition of 1% L-Gln, but in the growth period the values of 0.5 and 0.75 were significant (p<0.05). The results of the average feed conversion ratio for different treatments (Table 2) show that there were no significant differences between the experimental treatments (p>0.05). The relative weights of breast, thigh, wing and back were not affected by L-Gln supplementation (p>0.05). The effect of the experimental treatments on the relative weight of the lymphoid organs (Table 4) did not led any significant difference (p>0.05). Table 5 shows the effect of different levels of L-Gln supplementation on some blood parameters of broiler chickens at 42 days of age. Different L-Gln levels had a significant influence on the measured serum parameters (p<0.05). Different L-Gln levels affect cholesterol, triglyceride, VLDL, HDL and LDL levels (p<0.05). Dietary L-Gln significantly reduced the amount of total cholesterol, LDL, VLDL and triglycerides compared to the control group (p<0.05). The level of HDL in serum was significantly increased by 0.5% L-Gln (p<0.05). Addition of glutamine to the diets had no significant effect on white blood cells, heterophils, monocytes and eosinophils counts (p<0.05). The ratio of heterophil to lymphocyte in the chickens that consumed glutamine was significantly lower than the control group (p<0.05). L-glutamine has been reported to increase the activity of the intestinal enzyme Na-K ATPase, thereby indirectly increasing the absorption capacity of nutrients such as glucose and amino acids in the intestine. Researchers reported that L-Gln increases the performance and the feed intake of chickens by improving intestinal function and increasing digestibility. Expanding the villi of the small intestine can increase digestion and feed intake by increasing nutrient absorption and thus improving chicken performance. Consumption of 5 g/kg of L-Gln improved weight gain in broilers. The results obtained by Priya et al. (2010) showed that 0.5% L-Gln in the diet significantly increased the body weight of broiler chickens. Yi et al. (2001b) reported improved weight gain in turkey fed a diet containing 1% L-Gln during the first week and they noticed that dietary L-Gln had no significant effect on FCR. Adding 1% L-Gln to the diet improved growth performance and stimulate intestinal development. Soltan (2009) found that levels of 0.5, 1, 1.5 and 2% L-Gln had no effect on feed conversion ratio. In another experiment (Meng et al., 2009), administration of 0.01 and 0.05 g/kg L-Gln improved the weight of chicks. Soltan (2009) showed an improvement in body weight gain by 1% Gln. Improving the morphology of the digestive system is one of the possible mechanisms of the positive effect of L-Gln on improving weight. Administration of 1% L-Gln in chickens increased villus length and crypt depth at 21 days of age (Khempaka et al., 2011). Since Gln stimulates anabolic conditions in the body and increases the amount of protein synthesis, therefore, along with muscle growth, it can increase the final body weight (Grimble, 2001). Mussini et al., (2012), reported that FCR and BWG were numerically but not significantly improved by the L-Gln addition. Mussini et al. (2012) indicated that addition of Gln had no significant effect on dressing percentage and wing yield. Salmanzadeh et al. (2020) noticed that only spleen was affected by 1% and L-Gln had not any significant effect on bursa and thymus. In the current study, the level of 0.5% of L-Gln decreased serum cholesterol, triglyceride, VLDL and LDL and also significantly increased the level of HDL compared to the control groups. Avian health is directly related to the immune system, and birds with adequate immune systems grow better. The majority of essential amino acids are recognized as critical resources for cytokine production and immune function.