Effects of dietary conjugated linoleic acid isomers and vitamin E on fatty acid composition and cholesterol content of hen egg yolks.

摘要

The objective of this study was to develop functional eggs, by feeding hens with conjugated linoleic acid (CLA) isomers (0.0 vs 1.5%) and alpha -tocopherol (0 vs 120 mg/kg of diet) as an antioxidant. Thirty-six 25-week-old laying hens were randomly distributed into four groups of 9 hens and maintained in individual laying cages throughout 12 weeks of experiment. They were assigned to the four commercial layer diets (2770 kcal ME/kg; 16.7% CP): 0.0% CLA, 0.0% CLA+120 mg vit. E/kg of diet, 1.5% CLA and 1.5% CLA+120 mg vit. E/kg of diet. The laying performance, fatty acid composition (relative %) and cholesterol content of egg yolk lipids were determined. No apparent effects of dietary CLA on laying performance were observed. The rate of laying and egg production per hen were increased (P<0.01) by vitamin E. When compared to the 0.0% CLA diets, vitamin E added to the 1.5% CLA diets was more effective in increasing the rate of laying (P<0.01). Feeding the 1.5% CLA diets resulted in substantial deposition of CLA isomers (6.7%) in egg yolk lipids. Compared to the 0.0% CLA diets, the 1.5% CLA diets increased SFA (31.7 vs 51.9%; P<0.01), decreased MUFA (45.4 vs 27.3%; P<0.01) and less apparently PUFA content (21.7 vs 19.6%; P<0.01). Vitamin E had no effect on SFA, it decreased MUFA and slightly increased PUFA (P<0.01). When fed to hens in the 0.0% CLA diets, it decreased MUFA (wk 4, 8 and 12; P<0.01) and increased PUFA (wk 4; P<0.01) whereas in the 1.5% CLA diets, it decreased SFA (wk 4; P<0.05) and increased MUFA (wk 4 and 8; P<0.05). Egg cholesterol (mg per egg), was reduced (P<0.01) by both dietary supplements and the effect of vitamin E was more pronounced in the 0.0% CLA diets (P<0.01). In conclusion, vitamin E may exert alleviating effects on fatty acid composition of CLA-enriched eggs. However, the extent of these effects is negligible. Therefore, the composition of CLA-enriched eggs must be improved to consider them functional food products.