Effect of unsaturated fatty acid sources in diets containing different energy and protein levels on growth performance and blood metabolites in fattening lambs

The aim of this study was to determine effects of dietary high-linoleate seed (soybean) and high-oleate seed (canola) on blood metabolites and growth parameters of lambs fed diets containing different levels of energy and protein. Thirty male Afshari lambs were used to evaluate the effects of two dietary energy and protein levels (2.3 Mcal/kg metabolisable energy (ME), 14% crude protein (CP) and 2.7 Mcal/kg ME, 16.4% CP) and different levels of each oil seed (no seed, 5% soybean, 10% soybean, 5% canola, 10% canola) on blood metabolites and growth parameters. Lambs were randomly allotted to 10 dietary treatments as a 2×5 factorial arrangement. Diets were fed ad libitum for 84 days, after 14 days of adaptation. Feed intake was recorded daily and weight gain and blood metabolites were determined once each 14 and 28 days, respectively. The results showed that increasing dietary contents of CP and ME increased feed intake, growth rate, protein efficiency ratio and improved feed conversion ratio. Using 5% soybean seed in the high energy and protein diet resulted in a higher feed intake, gain and final weight (P<0.05). Serum glucose, cholesterol and low density lipoproteins were not altered, but serum high density lipoprotein was higher and albumin, triglycerides and very low density lipoprotein were lower in the lambs fed with oilseeds rich in unsaturated fatty acids (P<0.05). Finally, it was seen that supplementation of 5% soybean seed in high density diet had a positive effect on performance of growing lambs.