effects of supplementation time of l-carnitine and garlic powder on performance and carcass characteristics of broiler chickens

introduction carnitine has several roles in lipid oxidation, immunomodulation function and enhancing antibody responses. l-carnitine has been found to exhibit immunomodulatory effects. it enhances serum primary antibody response to sheep red blood cells (srbc) and subsequent humoral immunity using 100 mg l-carnitine/ kg diet compared with control group in leghorn chickens (deng et al., 2006). it was reported that only the immediate effects of dietary carnitine on immunocompetence is known while comparing long and short-term effects on early life on the immune system of broiler chickens is unknown. the organic allyl sulfur components in garlic (mainly allicin) were implicated to mediate its biological activity. the biological activities of these compounds may be related to their sh modification and antioxidant properties (prasad et al., 1996). age treatment prevented the reduction of the antibody production response in thymectomized mice and improved the thymectomy-induced deterioration of learning behaviors in passive avoidance performance and in a spatial memory task (zhang et al., 1998). materials and methods four hundred arian one-day-old broiler chicks were used. this experiment was conducted in order to consider the effects of l-carnitine and garlic powder on broiler chicken performance, blood metabolites and carcass characteristics in a 2×5 factorial arrangement in randomized complete design with 5 dietary treatments, 4 replicates and 12 birds in each and two periods: short (first 3 weeks) and long time (total production period). dietary treatments were 1) basal diet (bd: no supplementation), 2) ration having 0.02% flavomycin (positive control), 3) ration having 1.5% garlic powder, 4) ration having 0.025% l-carnitine and 5) ration having 0.025% l-carnitine plus 1.5% garlic powder. the birds were kept under conventional conditions for vaccination, temperature, ventilation, and lighting based on ross catalogue recommendations. standard management practices of commercial broiler production were applied. they were fed experimental diets from 15 to 42 d of age. the broiler diets were formulated based on standardized ileal digestible amino acids and other requirements were obtained from ross catalogue recommendations. humoral immunity of broilers against sheep red blood cells (srbc) were detected by intramuscularly injection of srbc (2.5% suspension in pbs, 1 ml/bird) to two birds from each replicate at 8 and 23 days of age in the first and second experiment respectively, followed by a booster injection at 6 days after the first injection. blood samples were collected at 6 days after the first and second injection and total ig, igg and igm were detected (cheema et al., 2000). the toe web swelling reaction to pha-p was measured in 2 broilers from each pen (marked with a black color) at days 12 and 26 of first and second experiment respectively. one-fifth milliliter of a pha-p solution (1 mg/ml in pbs) was injected subcutaneously into 2 sites on the left toe web of the broilers. as a sham control, 0.2 ml of pbs was injected into 2 sites on the right toe web. the thickness of each injection site was measured using a pressure-sensitive micrometer before injection and at 4, 12, 24, and 48 h after injection (wang et al., 2000). at the age of 42d, 5 broilers from each treatment with average body weight of each treatment were selected and blood samples were collected and white blood cell concentration like heterophile, lymphocyte percentage and heterophil to lymphocyte ratio were calculated. results and discussion results showed that supplementation time and dietary treatments did not have significant effects on humoral immunity against srbc and cell mediated immunity response against pha injection (p > 0.05). supplementation time and addition of l-carnitine and garlic powder decreased heterophil and heterophil to lymphocyte ratio and increased lymphocyte percentage (p < 0.05). garlic and garlic derived compounds were shown to alter the rate of metabolism of testosterone through regulation of the cytochrome p450 enzymes and garlic seems to inhibit the enzyme cytochrome p450 (pinto and rivlin, 2001), hence high level of steroids can cause thymus reduction. garlic consumption may exert regulatory effects on th1/th2 cytokine production and promote a th2 type or humoral immune response in rat spleen lymphocytes. conclusion it was concluded that application of the dietary supplements (0.025% l-carnitine plus 1.5% garlic powder) at the levels like this experiment did not improved humoral and sell mediated immunity whereas they increased immunity of broiler chickens and defensing mechanism.