Dietary fats and vitamin E in diets for laying hens

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 quality of eggs. The feed was based on wheat and corn. A total of 54 laying hens (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 collected during the whole feeding period (8 weeks) beginning after one week of adaption to the experimental diets. They were kept in a temperature controlled room at 4°C up to 6 months.<br>Laying rate, egg weight, daily feed intake and feed efficiency were neither affected by dietary fat source nor by the vitamin E supplementation. The vitamin E concentrations were increased (p<0,001) due to vitamin E addition. Thiobarbituric acid reactive substances (TBARS) were increased (p<0,001) by increased 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) and the monounsaturated fatty acids (MUFA) were decreased (p<0,001) by dietary safflower oil respectively. Saturated fatty acids (SFA) were not influenced by fat source. Dietary vitamin E resulted in a decrease of PUFA (p<0,01) and SFA (p<0,01) in fresh yolk lipids, whereas MUFA did not change. Storage of eggs up to 6 months generally caused a higher content of SFA,MUFA and PUFA compared to fresh egg yolk.