CLA on Egg Yolks
September 9/Agriculture Week -- According to a U.S. study, "Three experiments were performed to determine the effect of conjugated linoleic acid (CLA) on embryonic development in the absence of vitelline membrane disruption. In experiment 1, when eggs from control and CLA (0.5%)-fed hens were stored at 21 or 15 degrees C for 48 hours, mineral movement between the yolk and albumen was not observed (with the exception of Mg and Na)."
"Also, it was found that CLA-induced changes in yolk fatty acid content (e.g., increased saturated fatty acids and CLA) had begun to change after five days of feeding hens CLA, and no differences were detected in fatty acid composition after 14 days.
"In experiment 2, the hatchability of eggs incubated directly after oviposition or stored 24 hours at 21 or 15 degrees C was determined from hens fed control or 0.5% CLA diets. Regardless of storage conditions, CLA reduced hatchability. These data showed that CLA elicits negative effects on hatchability independent of vitelline membrane disruption or egg storage condition.
"In experiment 3, eggs were collected from hens fed 0 or 1% CLA daily for three weeks, stored at 21 degrees C for 24 hours, and incubated. Not only did CLA decrease hatchability, the data showed as the days of CLA feeding increased, the days of survival during incubation decreased. Average days of embryonic survival during incubation for the CLA group diminished to 18.0, 13.4, and 6.3 days for week 1, 2, and 3 of CLA feeding, respectively, and control remained at 20.6, 20.8, and 19.8 for the three weeks. These studies suggested that without the disruption of the vitelline membrane, hatchability and embryonic days of survival were significantly reduced by maternal CLA feeding in comparison to control-fed hens," wrote V.A. Leone and colleagues, University of Wisconsin.
The researchers concluded, "Evidence that embryos die earlier the longer the hens are fed CLA, even though no additional changes in the fatty acid content of eggs were found, suggested that factors other than storage and egg yolk fatty acid composition played a role in CLA-induced embryonic mortality."
Leone and colleagues published their study in Poultry Science ("Evidence for Conjugated Linoleic Acid-induced Embryonic Mortality That is Independent of Egg Storage Conditions and Changes in Egg Relative Fatty Acids." Poultry Science, 2009;88(9):1858-1868).
For more information, contact M.E. Cook, University of Wisconsin, Dept. of Animal Science, Madison, WI 53706.
From the September 14, 2009, Prepared Foods E-dition