Introduction The most important effect of using emulsifiers and l-carnitine in the diet is to help the process of digestion and absorption of fats. Improving the efficiency of metabolizable energy consumption and crude protein when emulsifier and l-carnitine supplements used in the diet indicates the positive effect of emulsifiers on the digestion and absorption of fats and other nutrients. Considering the different metabolic activities l-carnitine and emulsifier (lipidol) in broiler chickens, it seems that the use of these compounds together in low-energy diets can significantly improve the performance of broiler chickens. Therefore, the present research investigated the role of lipidol and l-carnitine supplements in reducing the negative effects of low-energy diets on growth performance, carcass characteristics, nutrient digestibility, blood biochemical parameters and meat oxidative stability of broiler chickens.
Materials and Methods The experiment was carried out in a completely randomized design with five treatments in four replicates and 12 chickens in each replicate. Broiler chickens were fed with diets including: 1. control diet 2. Low energy diet (150 kcal/kg less than the control diet) 3. Low energy diet + 100 ppm l-carnitine 4. Low energy diet + 1 g / kg lipidol 5. Low energy diet + 100 ppm l-carnitine + 1 g / kg lipidol for 42 days. Then, the growth performance of chickens, carcass characteristics, blood biochemical indicators (total antioxidant capacity, triglyceride, cholesterol, LDL and HDL concentrations), nutrient digestibility (dry matter, protein, fat and organic matter) in starter and grower periods and meat oxidative stability of broiler chickens were measured and recorded. Finally, the analysis of data was performed using GLM method by SAS software. The means were compared using Tukey's multiple range tests.
Results and Discussion The results showed that there was no difference in feed intake between the birds receiving the control diet and the other diets. Weight gain and feed conversion ratio of birds were significantly improved by control diet than other treatments (P<0.05). However, birds receiving low-energy diets containing lipidol + l-carnitine had the same feed conversion ratio (1.79) as birds receiving the control diet (1.75). Birds fed with low-energy diets containing lipidol and lipidol + l-carnitine had better weight gain and feed conversion ratio than birds fed with low-energy diets containing l-carnitine and without additives (P<0.05). Compared to the control treatment, the birds that were fed with low-energy diets containing lipidol and l-carnitine separately and together had a lower abdominal fat percentage (0.4%) (P<0.05). Also, birds fed with the control diet showed a tendency to increase the heart percentage compared to other experimental treatments (P=0.06). Birds fed with low energy diets containing lipidol and lipidol + l-carnitine had higher dry matter (3.6%), protein (7.8%) and fat (6.6%) digestibility in the starter period and higher digestibility of dry matter (6.9%) in the grower period compared to other treatments (P<0.05). In general, in the starter period, the birds fed with control diet showed lower digestibility of protein (P=0.06) and fat (P<0.05), and in the growth period, the digestibility of dry matter was lower than the birds fed with other diets. Birds that were fed with low energy diets containing lipidol and l-carnitine separately or together had higher total antioxidant capacity compared to birds fed with control diet and low energy diet without additives (P<0.05). Also, birds that were fed with low-energy diets containing l-carnitine and lipidol + l-carnitine had lower blood triglyceride (P=0.05) cholesterol and LDL concentrations compared to birds fed with control diet and low-energy diet without additives (P<0.05). Birds fed with low energy diet containing lipidol + l-carnitine increased blood HDL level compared to birds receiving low energy diet without additives (P<0.05). Birds that were fed with low-energy diets containing lipidol and l-carnitine separately and together had lower concentrations of malondialdehyde in thigh and breast meats on days 3, 6 and 9 after slaughter and kept in a refrigerator (4ﹾC) compared to birds fed with low energy diets without additives and control diet (P<0.01).
Conclusion Finally, the simultaneous utilization of 100 ppm l-carnitine and 1 g / kg lipidol in low-energy diet showed similar growth performance when compared with control diet and led to improved carcass quality, fat, protein and dry matter digestibility, blood lipid parameters and meat shelf life of broiler chickens.