Transfer of dietary conjugated linoleic acid to egg yolks of chickens

There is interest in increasing the conjugated linoleic acid (CLA) content of foods because of purported benefits of CLA for human health. Two experiments were conducted to determine the influence of dietary CLA concentration on CLA content of eggs. In Experiment 1, diets containing 0, 0.5, 2.5, or 5.0% CLA were fed to 26-wk-old White Leghorn hens (Hy-Line W-77) for 29 d. No CLA was detected in the yolk lipids of hens fed the control diet. Concentration of CLA in the yolk lipids linearly increased as dietary CLA increased. The maximum concentrations of CLA in the yolk lipids of hens fed 0.5, 2.5, or 5.0% CLA occurred 11 d after the start of the experiment and were 0.82, 5.82, and 11.20% of the total fatty acids, respectively. Concurrent decreases were observed in concentrations of C-18:1, C-18:2, C-18:3, C-20:4, and C-22:6. Rate of egg production, body weight gain, and feed intake were not affected by dietary CLA. Average weights of eggs and yolks were decreased for hens fed 5.0% CLA compared with other dietary treatments. In Experiment 2, 62-wk-old hens were fed diets containing 0 or 5.0% CLA. Maximum CLA concentration in the yolk lipids of hens fed 5.0% CLA was less (7.43%) than that observed in Experiment 1. Feeding 5.0% CLA decreased feed intake but did not affect rate of egg production, weight of eggs, albumens, or yolks, or body weight gain through 36 d. Results of these experiments show that eggs produced by hens fed 5.0% CLA will contain 310 to 365 mg of CLA per egg. Such eggs could provide a substantial amount of CLA source in human foods.