Effect of dietary conjugated linoleic acid on laying hen performance, egg yolk fatty acid composition and egg quality during refrigerated storage

Sixty-four Lohman LSL white layers, 75 weeks of age, kept in individual cages were assigned randomly to four treatments of 16 hens per group. The hens received one of four diets with 0, 0.5, 1 or 2% CLA for 4 weeks. Eggs were collected daily and stored at 4 degrees C for 1 or 42 days. The performance of hens and fatty acid composition, thiobarbituric acid reactive Substances (TBARS) levels, pH of yolk and albumen, and yolk colour in eggs were measured. Feed intake, feed conversion and egg weight were influenced by the dietary CLA level (P<0.05). The concentration of CLA in the yolk lipids linearly increased as the dietary CLA increased. The addition of CLA to feed significantly (P<0.01) increased the saturated fatty acid (SEA) and polyunsaturated fatty acid (PUFA) and decreased (P<0.01) the MUFA content in the egg yolk. The duration of refrigeration increased the proportion of egg yolk but decreased the albumen content. It also increased egg yolk pH but decreased albumen pH. Yolk colour was influenced by storage time but it was not influenced by the CLA level. TBARS values were significantly influenced by the dietary CLA and storage time (P<0.01).