Dietary fats and vitamin E in diets for laying hens: Effects on laying performance, storage stability and fatty acid composition of eggs

A study was conducted to determine the effects of dietary safflower oil and /or tallow with or without vitamin E supplementation (0, 100 or 200 mg/kg) in a feed for laying hens, on laying performance and traits of internal qua lity of eggs. The feed was based on wheat and corn. A total of 54 laying he ns (Warren Isabrown) were assigned at an age of 25 weeks to nine treatment groups (6 birds per treatment in 3 cages of 2 hens each). Eggs were collect ed during the whole feeding per zeta iod beginning after one week of adapti on to the experimental diets. They were kept in a temperature controlled ro om at 4 degrees C up to 6 months. Laying rate, egg weight, daily feed intake and feed efficiency were neither affected by dietary fat source nor by the vitamin E supplementation. Yolk dry matter was reduced by storage. Supplemental vitamin E (p < 0.001) and d ietary safflower oil (p < 0.05) reduced the crude fat content of fresh egg yolk. The vitamin E concentrations were increased (p < 0.001) due to vitami n E addition. Thiobarbituric acid reactive substances (TBARS) were increase d (p < 0.001) by elevated vitamin E concentration in egg yolk, whereas the oxidative stability was slightly increased after storage. The proportion of polyunsaturated fatty acids (PUFA) of egg yolk was increased (p < 0.001) a nd the monounsaturated fatty acids (MUFA) were decreased (p < 0.001) by die tary safflower oil respectively, mainly as a result of an increase of C18:2 omega-6 and C20:4 omega-6 replacing C16:1 omega-7 and C18:1 omega-9. The a ddition of tallow to the diets resulted in an increase (p < 0.001) of C18:4 omega-3 and C22:6 omega-3 compared to safflower oil diets. Saturated fatty acids (SFA) and total lipids were not influenced by fat source. Dietary vi tamin E resulted in a decrease of PUFA (p < 0.01), SFA (p < 0.05) and total lipids (p < 0.05) in fresh yolk lipids, whereas MUFA did not change. Stora ge of eggs up to 6 months generally caused a higher content of SFA, MUFA, P UFA and total lipids compared to fresh egg yolk.