Comparative study of the effects of ethanolic extract of sage (Salvia officinalis) and vitamin C on antioxidant status, blood and biochemical parameters, mortality, and performance in broilers under induced ascites

Introduction: Ascites is one of the most common metabolic syndromes in today's fast-growing broilers and is associated with rapidly growing tissues and characterized by accumulation of lymph fluid in the peritoneal spaces. Effective factors in the occurrence of ascites syndrome include 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 produced in the body by damaging the cell membrane lead 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, free radicals from oxygen derivatives 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. Therefore, it is suggested that the use of antioxidants can prevent ascites and improve performance in broilers. Medicinal plants are among the rich sources of natural antioxidants that do not have the harmful effects of antibiotics and synthetic antioxidants. For this reason, the use of medicinal plant extracts is an important step in animal nutrition to increase the immunity of poultry. The mentioned extracts have strong antioxidant, antibacterial, and digestive properties. Probably, the positive effects of medicinal plants are due to the active compounds found in plant extracts such as menthol, thymol, and carvacrol. This study aimed to investigate the effects of ethanolic extract of sage on the performance, antioxidant status, and blood parameters of broiler chickens under induced ascites.Materials and methods: A total of 450 one-day-old chickens (Ross 308) were reared in the form of a completely randomized design with six treatments and five replications (15 chickens in each replication). Experimental treatments include 1. Positive control group (without inducing ascites and fed with basic diet), 2. Negative control group (inducing ascites and fed with basic diet), 3 and 4. Vitamin C group (inducing ascites with levels of 1000 and 2000 ppm vitamin C), 5 and 6- Sage group (ascites induction with 1000 and 2000 ppm of sage extract). To induce ascites, water containing 1200 mg of sodium (three grams per liter of sodium salt) was provided to the chickens from the 15th day of the experiment. 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, killed and the ascites index was calculated as the ratio of the weight of the right ventricle to the total ventricles. 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. Blood and biochemical parameters such as the number of red and white blood cells, hemoglobin, hematocrit, heterophil and lymphocyte, serum triglyceride, and cholesterol, as well as serum antioxidant parameters including the level of malondialdehyde and the activity of antioxidant enzymes including glutathione peroxidase, superoxide dismutase, and catalase were measured. In addition, liver enzymes present in the serum including alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl transferase (GGT), and alkaline phosphatase (ALP) were also measured.Results and discussion: The results showed that induction of ascites increased the ratio of the right ventricle to total ventricles, mortality due to ascites, feed consumption, feed conversion ratio, and body weight loss (P<0.05). Administering sage extract improved the mentioned traits and vitamin C also reduced the ratio of right ventricle to total ventricles, losses due to ascites (P<0.05). Sage extract and vitamin C moderated the increasing effects of ascites induction on heterophiles, triglyceride, and cholesterol and increased red blood cells, hematocrit, and hemoglobin compared to the negative control treatment (P<0.05). In addition, the induction of ascites decreased the activity of glutathione peroxidase, superoxide dismutase, and catalase enzymes and increased serum malondialdehyde, experimental treatments, especially sage extract, improved the antioxidant status compared to the negative control treatment (P<0.05). Also, the induction of ascites increased the serum levels of aspartate aminotransferase, alanine aminotransferase, gammaglutaryl transferase, and alkaline phosphatase enzymes. The addition of experimental supplements, especially sage, decreased the serum level of the mentioned enzymes (P<0.05).Conclusions: The results of this research showed that the use of sage extract compared to vitamin C has better results on performance, increasing antioxidant power, and reducing stress of broilers with ascites.