Evidence that maternal conjugated linoleic acid negatively affects lipid uptake in late-stage chick embryos resulting in increased embryonic mortality

An experiment was performed to determine the effect of maternal dietary conjugated linoleic acid (CLA) on growth and composition of surviving chick embryos and residual yolk sacs during the last week of development when lipid utilization becomes prevalent. After 14 d on experimental diets, hatchability of noncooled eggs obtained from CLA-fed hens (0.5% of the diet) was 10%, where 20% of surviving CLA embryos died after d 13 of incubation. Hatchability was 93% for controls and only 4.36% of mortality occurred after d 13 of incubation. Decline in yolk sac weight in control embryos (0.75 g/d) was significantly greater than that from viable CLA embryos (0.51 g/d). Growth rate (2.6 g/d) of surviving embryos from d 13 to 20 was reduced in CLA embryos in comparison to growth rate of controls (3.0 g/d). Relative proportion of lipid in residual yolk sacs in embryos from control-fed hens decreased from 26.72% (d 13) to 15.94% (d 19) during incubation, whereas little change was evident in residual yolk sac from CLA embryos on d 13 (21.52%) to d 19 (20.39%). Fatty acid analysis of residual yolk sac contents suggested that transport of fatty acids from the contents (liquid yolk) to the yolk sac membrane was not impaired in CLA embryos, as shown by a similar pattern in reduction of total fatty acids in residual yolk sac contents between treatment groups. Apart from 18:1n-9 (d 17), there were no consistent differences in the fatty acid content between embryos from hens fed the control diet or the CLA diet at any time point. Maternal CLA led to increased 18:0 and decreased 18:1n-9 in yolk lipid and embryonic tissues compared with controls across time. These findings could possibly suggest that CLA embryos had less capacity to use yolk lipids from the residual yolk sac during the last week of incubation.