Improving Growth Performance, Biochemical Parameters and Reducing Mortality due to Ascites in Broilers by Propranolol Inclusion

Introduction: Pulmonary hypertension syndrome (ascites) is one of the most common metabolic syndromes in today's fast-growing broilers. It is associated with rapid growth and is characterized by the accumulation of fluid in the abdominal spaces. Effective factors in the occurrence of ascites syndrome included free radicals in the body such as superoxide, hydroxide, and hydrogen peroxide. By reducing the capacity of the body's antioxidant systems, free radicals make the bird susceptible to various diseases. Free radicals are produced in the body by damaging the cell membrane leading to cell death and ultimately tissue damage. Therefore, by increasing cell protection from such injuries, one of the common causes of ascites and heart failure abnormalities can be prevented. In addition, reactive oxygen species (ROS) reduce the half-life of nitric oxide (vasodilating agent), causing a decrease in the ability of vasodilation and providing the basis for the occurrence of ascites. B-blockers (or b-adrenergic antagonists) are a group of drugs widely used in the treatment of cardiovascular diseases, namely arterial hypertension, cardiac arrhythmias, and angina pectoris as well as other types of pathologies such as anxiety or glaucoma. Part of the beneficial cardiovascular effects shown by this group of compounds has already been associated with the antioxidant properties that some of them seem to possess. It demonstrated a concentration-dependent membrane anti-peroxidative activity for propranolol, pindolol, metoprolol, atenolol, and sotalol. Of the five b-blockers examined, propranolol was the most potent agent, and the activities seemed to correlate with the drugs’ hydrophobicity. Further studies indicated that the antioxidant activity of propranolol was independent of its pharmacological activity and was related to its intrinsic chemical properties rather than to its quinidine-like membrane stabilization effect. The antioxidant properties of propranolol were later corroborated using membrane and cellular models. More recently, propranolol’s antioxidant-related cardioprotective effects were studied in rats, showing that the chronic treatment with this b-blocker was found able to protect against ischemia-reperfusion injury. Thus, it is now accepted that propranolol is an important therapeutic tool against oxidative stress by stabilizing membranes, including lysosomes, inducing the activity of antioxidant and other beneficial enzymes, increasing endothelial nitric oxide production, and directly protecting isolated membranes, cardiovascular cells, and tissues against oxidative injury. So far, there have been few studies on the effects of propranolol in broilers. Therefore, the current research was designed to evaluate the propranolol on the growth performance, antioxidant status, and the status of some hematological and biochemical parameters of broiler chickens under induced ascites. Materials and Methods: The experiment was carried out in a completely randomized design with four treatments in four replicates and 10 chickens in each replicate. Experimental treatments included: 1- positive control group (no induce ascites, basal diet), 2- negative control group (inducing ascites and fed with basic diet), 3 and 4- propranolol groups (inducing ascites, supplemented with 50 and 100 ppm propranolol). To induce ascites, water containing 7 g per liter of salt was provided to the chickens from day 15 of age. Growth performance parameters including feed intake, weight gain, and feed conversion ratio were calculated for the total period. On the last day of the experiment (42 d), two birds were randomly selected from each cage and after sampling from the wing vein, they were killed and the ascites index was calculated as the ratio of the weight of the right ventricle to the weight of total ventricles (RV/TV). The mortalities were collected as soon as they were observed and after weighing to correct the feed conversion ratio, were necropsied to investigate the cause of death. Serum antioxidant parameters include the level of malondialdehyde and the activity of antioxidant enzymes including glutathione peroxidase, superoxide dismutase, and catalase were determined. In addition, the serum enzymes including alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) were measured.Results and Discussion: The results showed that induction of ascites increased RV/TV, mortality due to ascites, and feed conversion ratio; while it decreased feed intake, and live weight (P<0.05). Additionally, ascites induction increased the number of white and red blood cells, hematocrit, hemoglobin, heterophile, and decreased lymphocytes (P<0.05). The levels of glutathione peroxidase, superoxide dismutase, and catalase enzymes were decreased in ascites-induced broiler chickens. At the same time, it decreased the level of serum malondialdehyde, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase enzymes (P<0.05). Inclusion of propranolol had no significant effect on growth performance (P>0.05), but it significantly decreased the ratio of right ventricle to total ventricles and ascites related-mortalities (P<0.05). Moreover, inclusion of propranolol reduced the number of white and red blood cells, hematocrit, hemoglobin, heterophile and increased lymphocytes compared to the negative control birds (P<0.05). In addition, propranolol enhanced the levels of glutathione peroxidase, superoxide dismutase and catalase enzymes and reduced the levels of malondialdehyde, aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase in serum (P<0.05). In conclusion, propranolol inclusion at 100 ppm may be used to alleviation the physiological responses of broilers exposed to ascites.Conclusion: In conclusion, propranolol inclusion at 100 ppm may be used to alleviation the physiological responses of broilers exposed to ascites.