Maternal dietary conjugated linoleic acid is not directly toxic for the developing chick embryo, but causes embryo mortality by altering fatty acid composition of the egg yolk in the chicken

BACKGROUND: Conjugated linoleic acid (CLA) was shown to cause embryo mortality when added into chicken diets. The objective of this study was to determine if CLA accumulation in yolk was directly responsible for embryo mortality. MATERIAL AND METHODS: Forty-two 30-week-old hens were assigned to seven groups and fed a diet containing 5 g kg(-1) canola oil (Group A), 5 g kg(-1) CLA (Group B), 5 g kg(-1) CLA plus 20 g kg(-1) canola oil (Group C), 5 g kg(-1) CLA plus 30 g kg(-1) canola oil (Group D), 5 g kg(-1) CLA plus 40 g kg(-1) canola oil (Group E), 10 g kg(-1) CLA plus 40 g kg(-1) canola oil (Group F) or 20 9 kg(-1) CLA plus 40 g kg(-1) canola oil (Group G) for 22 days. Collected eggs were held at 15 degrees C for 24 h, and then incubated. For fatty acid analysis, three eggs were collected on the 22(nd) day of the study. RESULTS: After the sixth day, embryonic mortality was 100% in eggs from Group B versus 2,30,21, 4, 0, and 9% in groups A, C, D, E, F and G, respectively. The ratio of SFA/UFA of yolks from groups A, B, C, D, E, F and G was 0.64, 1.53, 1.07, 1.06, 1.08, 1.05 and 1.13, respectively. Relative levels (%) of CLA in the eggs from the groups A, B, C, D, E, F and G were 0.12, 2.29, 1.68, 1.80, 1.76, 3.04, and 5.25%, respectively. CONCLUSION: This study showed that CLA was not directly toxic for developing embryo, but caused mortality in the fertile eggs by increasing the ratio of SFA to UFA in egg yolk. (C) 2009 Society of Chemical Industry