Effects of recycled soy oil sources and vitamin E and C supplementation on serum parameters, yolk lipid profile and egg oxidative stability in laying hens

The objective of this study was to assess the effects of soy oil sources، dietary vitamin E and vitamin C supplementation on serum and yolk total cholesterol (TC) and triglyceride (TG) and contents and egg oxidative stability in laying hens. A total of 300 Hy-line variety W-36 laying hen with 44-wk of age were used. Twelve corn-soybean meal-based diets containing; 3. 5% refined soybean oil (SBO)، recycled soybean oil (RSO)، or acidulated soybean oil soapstocks (ASO) each containing two levels of vitamin E (0 and 250 mg/ kg diet)، or two levels of vitamin C (0 and 250 mg/ kg diet) were used in a completely randomized design trial with a 3×2×2 factorial arrangement. The yolk oxidative stability was determined on 3 groups of fresh eggs after refrigeration at 5°C for 1، 15، and 30 days. The results showed that serum concentrations of TC and TG، and yolk TC content were not affected by dietary oil sources (P>0. 05). Dietary inclusion of RSO and ASO، however، increased (P<0. 05) egg TG content. Although dietary supplementation of vitamin E had no marked effect on serum and egg lipid profile، supplemental vitamin C decreased (P<0. 05) egg TG. No interaction of dietary fat sources and vitamin supplementation was observed on serum TC and TG or egg TC. However، there was a positive interaction between vitamin E and vitamin C for yolk TG content، so that the presence of both vitamins had more reducing effect on yolk TG. On the other hand، 30 days egg storage decreased (P<0. 05) yolk oxidative stability and dietary vitamin E supplementation improved stability index. These results confirm the fact that egg triglyceride is more prone to dietary manipulation compared to egg cholesterol.