عنوان مقاله [English]
نویسندگان [English]چکیده [English]
Introduction: Use of antibiotic growth promoters (AGP) in broiler diets has been banned in the European Union and in many countries. Therefore, researches have focused on the development of alternative strategies. Various products and natural materials such as probiotics, prebiotics, organic acids, and plant extracts have been tested as effective alternatives to AGPs. L-Carnitine (β-hydroxy-γ-trimethyl amino butyrate) is a water soluble quaternary amine and exists naturally in microorganisms, plants, and animals (Dikel et al., 2010). L-Carnitine is synthesized exclusively in the liver of animals and plays a key role in energy metabolism of cells, mainly by transferring long-chain acyl groups from cytoplasm to mitochondrial matrix for β- oxidation (Dikel et al., 2010). It has been reported that the addition of L-carnitine to broiler breeder diet in early stages of growth improved their performance (Golzar-adabi et al. 2005). Inclusion of L-Carnitine to young animal diet improves use of fatty acids and their energy efficiency; therefore, it improves growth and feed conversion ratio (Zhang et al. 2010).
In the folklore of many cultures, garlic (Allium sativum L.) has been widely used as a therapeutic agent. Garlic has rich organosulfur compounds and metabolites (allicin, diallyl sulfide, and diallyl trisulfide) (Kim et al., 2009). Allicin and its related compounds in garlic inhibit the HMG-CoA reductase enzyme, which plays a key role in the formation of liver cholesterol; then, allicin decreases cholesterol levels (Anthony et al. 2005). Duration of L-Carnitine and garlic supplementation in broiler chicken diet may have different effects on broiler chicken performance. Therefore, the aim of this study was to investigate the duration of supplementation of L-Carnitine and garlic powder on broiler chicken performance, serum biochemistry, carcass parameters, and meat quality.
Materials and methods: In order to consider the effects of L-carnitine and garlic powder on broiler chicken performance, blood metabolites and carcass characteristics, a total of 480 Arian one-day-old broiler chicks were allocated to 2×5 factorial arrangements in a completely randomized design with 5 dietary treatments, 4 replicates, and 12 birds in each replicate. Dietary treatments were 1) basal diet with no additive (BD), 2) BD plus 0.02% flavomycin antibiotic (positive control), 3) diet containing 1.5% garlic powder, 4) BD plus 0.025% L-Carnitine, and 5) diet containing 0.025% L-Carnitine plus 1.5% garlic powder in two periods (short term: first 3 weeks and long term: 6 weeks period). The birds were kept under conventional conditions for vaccination, temperature, ventilation, and lighting based on Arian catalogue recommendations. The birds fed experimental diets from 1 to 42 days of age and standard management practices of commercial broiler production were applied. The broiler diets were formulated based on standardized ileal digestible amino acids and other requirements were obtained from Arian catalogue recommendations. During the experiment, body weight and feed intake were recorded and finally feed conversion ratio and European production efficiency factor were calculated. From 2 birds of each pen, blood samples were collected at the end of experiment, then cholesterol, triglycerides, HDL-cholesterol, and LDL-cholesterol were detected. At 42 d, 2 broiler chickens per replicate were selected and sacrificed. Carcass, spleen, bursa of Fabricius, abdominal fat, thigh, and breast percentages were expressed as their percentages to live body weight. Thigh and breast meat pH and color were measured by pH meter (330i/SET WTW model) and electric colorimeter (1002 model- RGB Lutron), respectively. The lactate concentration of the breast meat was estimated by a spectrophotometer and calculated using the following formula (Zhang et al., 2009):
Lactate concentration = ×22
Results and discussion: Results showed that supplementation length and dietary treatments did not affect broiler chickens body weight, feed intake, feed conversion ratio, meat pH, serum triglyceride, cholesterol, HDL-cholesterol, and LDL-cholesterol, and breast meat lactate concentrations (P>0.05). Dietary treatments and supplementation period significantly influenced breast, bursa, and abdominal fat percentage (p < 0.05). L-Carnitine positively facilitates consumption of short and medium chain fatty acids by the mitochondria (Tan et al. 2008). Therefore, the diet containing L-Carnitine stimulates the oxidation of fatty acids to produce adenosine triphosphate and use of energy. In addition, positive effect of garlic powder on performance of broiler chicks can be attributed to the antioxidant and some growth-promoting effects of this herbal plant (Anthony 2005).
Conclusion It was concluded that application of the dietary supplements (0.025% L-Carnitine plus 1.5% garlic powder) in a short or long period, are not advisable for broiler chicken diets, since they make the rations more expensive.