چكيده لاتين :
Introduction: The use of antimicrobial growth promoters (AGP) in animal nutrition has been beneficial for the improvement of growth performance and prevention of diseases (Barton, 2000; Snel et al., 2002). Due to its antimicrobial properties, garlic has been tested as an alternative growth promoter in broiler chickens (Freitas et al., 2001; Demir et al., 2003 and Lewis et al., 2003). Freitas et al. (2001) showed that body weight gain and feed conversion ratio in broiler chickens, that received a diet supplemented with commercial garlic product at concentration up to 45 Kg/ton were not affected by garlic supplementation. However, Lewis et al. (2003) and Demir et al. (2003) reported a trend in improved body weight gain and feed conversion ratio in broiler chickens fed low concentration of commercial garlic product. Garlic (Allium sativum) is widely used as either a flavoring agent for food or as a medicinal agent for the treatment of a variety of diseases (Essman, 1984; Konjufca et al., 1997; Sallam et al., 2004). According to Lawson and Wang (2001), the increased benefits associated with garlic consumption can be attributed to the thiosulfinates, the single most abundant class of organosulfur compounds. Allicin, typically accounting for 70% of the total thiosulfinates (approximately 0.4% by fresh mass), is produced when fresh and raw garlic is chopped or crushed, rupturing the intercellular compartments that keep alliin and alliinase physically separated from each other
(Lawson, 1998; Rybak et al., 2004). On the other hand ration fatty acid level may influence on effectiveness of medicinal plants and their extracts on broiler chickens performance. Aim of this experiment was to explore effect of garlic powder on broiler chicken performance and immunity fed diet with different levels of crude fat. Material and methods: This study aimed to investigate the effect of garlic powder and flavomycin antibiotic on performance and fat digestibility of broiler chickens fed diets with different levels of crud fat (CF). Three hundred one-day-old male broiler chicks (Ross 308) were assigned to 1 of 6 dietary treatments in a completely randomized block design with a 3x2 factorial arrangements. Each treatment consisted of 5 replicates with 10 chicks each. Dietary treatments were 1) basal diet (BD) (3% CF), 2) high fat diet (HFD) (5% CF), 3) BD plus 1.5% garlic powder, 4) HFD plus 1.5% garlic powder, 5) BD plus flavomycin (200 g/kg) and 6) HFD plus flavomycin (200 g/kg). At the end of the experiment feed intake (FI) and body weight (BW) were recorded then feed conversion ratio (FCR) was calculated. Broiler chickens carcass traits (carcass, breast, thigh and abdominal fat percentage) and white blood cell count (heterophil, lymphocyte and heterophil to lymphocyte ratio) were determined. In order to investigate humoral immunity of broilers, sheep red blood cells (SRBC) were used as T-dependent antigen to quantify the antibody response. Two birds from each replicate were injected intramuscularly with SRBC (2.5% suspension in PBS, 1 ml/bird) at 23 d of age, followed by a booster injection at 8 days after the first injection. Blood samples were collected at 7 days after the first and second injection. At the d 42, blood samples collected from one broiler of each replicate then serum glucose, cholesterol, total protein, LDL-cholesterol and HDLcholesterol were measured.
Results and discussion: Feed intake, feed conversion ratio, fat digestibility, blood metabolites, blood cells count and carcass traits of broiler chickens were not influenced by dietary treatments (P<0.05) while those received BD plus flavomycin or HFD plus garlic powder exhibited greater body weight compared to control group (P >0.05). HFD increased broilers first IgM and total antibody contents against SRBC as compared to control birds (P <0.05). In comparison to control group, broilers fed garlic powder containing diet had higher first and second IgM, total antibody and second IgG contents against SRBC (P >0.05). Similarly, some studies focused on growth, conversion and meat quality of different types of animals indicate positive effects. Cullen et al. (2005) examined the effect of garlic supplement in the amount of 1% in pig feed and recorded an increase in growth, conversion and meat quality in comparison to the control group. Horton et al. (1991); Freits et al. (2001) and Bampidis et al. (2005), had similar results in their study of broilers, but they also concluded that lower concentrations, ranging between 1 and 2%, were actually more effective. In contrast to our results some studies, however, suggested that commercial garlic oil, garlic powder, and commercially available garlic extract may not be hypocholesterolemic (Berthold et al., 1998; Isaacsohn et al., 1998; McCrindle et al., 1998). Although the reason for this is unknown, it likely relates to preparation methods, the stability of chemical components, and the duration of the study (Amagase et al., 2001). Many studies indicated that allicin was the potentially active component of garlic; however, it was observed that allicin was unstable and poorly absorbed from the digestive tract (Lawson et al., 1992). Conclusion: These results suggested that dietary fat percentage significantly decreased broiler chickens feed intake whereas garlic powder improved broiler immune response and it maybe use as an alternative to flavomycin.
