Effects of dietary vitamin C supplementation on growth performance, carcass characteristics, gastrointestinal organs, liver enzymes, abdominal fats, immune response and cecum microflora of broiler chickens

Description of the subject. Increasing the concentrations of blood glucose lead to decreased appetite and decreased concentration of stimulant in the hunger center of the bird's hypothalamus and consequently decreased feed intake. High intakes of vitamin C may alter blood glucose concentration, although the evdienec is contradictory.
Objectives. The aim of this study was to evaluate the effects of three different levels of vitamin C (0, 200 and 400 mg/kg DM) on performance, carcass and digestive organ characteristics, blood plasma components, liver enzymes, immune system, and cecal microbial flora of broilers.
Method. The study had a completely randomized design with 3 treatments and 4 replicates of 10 chickens per pen. The study lasted 42 days and started with 120 one-day-old male chickens of commercial Ross 308 strain. Tmt measn were compared using Duncan's multiple-range test.
Results. Chicks fed a diet containing 200 mg/kg vitamin C had the highest feed intake and weight gain as well as the best feed conversion ratio, the lowest cost per kilogram of live body and the best European production factor. The effect of vitamin C was significant on live body weight, featherless weight, full abdomen carcass weight, empty abdomen carcass weight, relative crop weight and relative breast weight (p < 0.05) and the highest increase was related to the level of 200 mg/kg vitamin C. On the other hand, the use of different levels of vitamin C on blood parameters and liver enzymes of broilers was not significant (P≥0.05). In addition, the percentage of neutrophils and lymphocytes was significant (p < 0.05) and the highest percentage of neutrophils was also for using the level of 200 mg/kg vitamin C. Comparing the mean results of antibody titers against SRBC did not show a significant difference (P≥0.05), except for 35 days of age, which was significant (P <0.05). Numerically, the highest antibody titer was related to the level of 200 mg/kg vitamin C. So, based on the results of the present study, the use of 200 mg/kg vitamin C to supplement the diet of Ross 308 strain broiler chickens is recommended.
Conclusions. Although vitamin C was not very effective on blood parameters, it improved the immune system and reduced the fat content of the ventricular area, thereby improving the quality of carcass meat. Therefore, according to the results of this experiment, it is recommended to use 200 mg/kg vitamin C in diet as an antioxidant compound and a cheap promoter of growth.
Keywords: Chick, ascorbic acid, immunity, performance, plasma.

1. Introduction
In the poultry industry, efficiency of food utilization is critical and much effort has been made to to reduce production costs by improving this efficiency. In addition, in the evolution of the poultry industry, with regard to the efficiency of production and economic efficiency, today the greatest emphasis is on the quality of meat (Grashorn, 2007; Hulan et al., 1988; Miller et al., 1969). On the other hand, broilers are always prone to storing large amounts of fat in the body because of their genetic characteristics. In fact, the liver of broilers produces large amounts of triglycerides and lipoproteins entering them into the blood (Griffin et al., 1991). In addition, fatty acids may be altered in liver cells and, in the form of triglycerides, enter very low-density lipoproteins (VLDL) and transfer to other tissues via the bloodstream (Post-Beittenmiller, 1996).
The concentration of blood glucose in poultry determines feed consumption. Increasing the concentrations of blood glucose lead to decreased appetite and decreased concentration of stimulant in the hunger center of the hypothalamus and consequently, decreased feed intake (Shurlock & Forbes, 1981; Ferket & Gernat, 2006). High intakes of vitamin C may alter blood glucose concentration, although the evdienec is contradictory, with Branch (1999) stating‌ that high intakes can lead to increased blood glucose and Abdel-Wahab et al. (2002) reported that taking vitamin C lowers blood glucose. Vitamin C may also alter lipid metabolism thereby inproving product quality. Supplementing vitamin C can reduce serum cholesterol and blood lipoprotein concentrations and prevent cholesterol deposition in liver tissue (Abdel-Wahab, 2002; Nicolle et al., 2004). Vitamin C may also have further benefits in poultry suffering environmenta stress. Under these conditions, Vitamin C inhibits the activity of 21-hydroxylase and 11–β hydroxylase (key enzymes in the biochemical pathways of corticosteroids) (Brake, 1989). Thus vitamin C can prevent the negative effects of stress on immune system and performance of poultry are then prevented by (Pardue & Thaxton, 1986). However, further research under farm conditions is required to better establish the benefits of vitamin C. The aim of this study was to investigate of the effect of vitamin C on growth performance, carcass characteristics and digestive organs, blood plasma components, liver enzymes, carcass fat, immune system, and microbial flora of the cecum of broilers.

2. Materials and Methods
The study was conducted at a broiler farm in Masal, Iran. The experiment was performed with 120 one-day-old male chickens of the commercial Ross 308 strain with an average weight of 45±2g. The study had a completely randomized design with 3 treatments and 4 replicates of 10 chickens per pen for 42 days. The three treatments were no additional vitamin C (VC0 mg/kg), 200 mg/kg DM additional vitamin C (VC200 mg/kg DM) and 400 mg/kg DM additional vitam=min C (VC400 mg/kg). All three groups were fed the same basal diet containing the minimum recommended nutrients from the Ross 308 feed guide (Manual, 2012) (Table 1). The chickens were raised in 1 × 1 m cages on a bed of cellulose roll and fed their experimental diets for 42 days. Each cage contained a cylindrical feeding container and a manual chicken drinker. The temperature in the pens was 33 ºC for the first week, gradually dropped to 23 ºC by day 18 and was constant thereafter. Room humidity was set to 65 to 70% throughout the study period and included hicks were given 23 hours of light exposure and one hour of darkness, Food anwater were available ad-libitum throughout the stduy. All birds were vaccinated against infectious bronchitis (10 days old), Newcastle disease (4, 21 and 35 days old) and infectious Bursal disease (12 days old). All the vaccines were obtained from the Razi Vaccine and Serum Institute (Karaj, Iran).