عنوان مقاله [English]
Background and objectives: A large part of animal performance is under effect of the dietary nutrient level and the balance of nutrients in the feed consumes a great deal on the yield of the farm animals. Studies on ruminant’s nutrition have shown that diets containing high levels of concentrate can increase the growth rate and increase the production level. Also it has been reported that high energy diets have improved the feed conversion rate. Despite its importance there is no much information about response of Iranian sheep, especially fatty tailed breeds to nutrient requirements estimated by new nutritional systems. Therefore, the aim of this study was to investigate the effect of two dietary treatments with energy level recommended by SNRS (2.25 ME cal/Kg) and 10% higher (2.5 ME cal/Kg) on growth performance and blood parameters of two Iranian breed lambs.
Materials and methods: This study, was conducted in completely randomized blocks design with two treatments (2 level of dietary energy) and two blocks (Zel and Afshari breeds) using 20 lambs with a mean body weight of 20 and 28 kg respectively in a 150 day period, during which time feed intake and the feed residues were weighed at the beginning and the end of each day, and each 14 days, lambs were regularly weighed. In order to investigation of the blood parameters, Blood samples were collected from the venous veins of the lambs 4 times (on days 10, 30, 50 and 70). Finally, the parameters of triglyceride, cholesterol, HDL, and LDL were measured. Statistical analyzes were performed using SAS version 9.2.
Results: Lambs receiving High energy diet showed more weight gain. According to the results, Zel and Afshari breeds in this treatment had 24 and 34 grams, respectively, more weight gain than the low energy treatment, which was statistically significant in Afshari lambs. Also, the feed conversion rates of lams receiving High energy diet were 0.7 and 0.9 units lower respectively. The results of the analysis of blood parameters showed that increase in dietary energy in Afshari lambs, increased blood glucose and triglyceride levels, and the cholesterol, LDL and HDL levels were decreased significantly with decreasing dietary energy level in both breeds.
Conclusion: Based on the results of this study, it can be said that using the energy level higher than the recommendations for Afshari lambs results in improvement of feed conversion rate, which is associated with an increase in the weight gain, hence, can improve the income earned by the farmer.