Distribution of 15N-chlorocholine chloride in eggs of laying hens.

The distribution of Chlorocholine chloride (CCC) in the eggs of laying hens was studied using 15N-CCC. Twelve layers (37 weeks old) were divided into four groups and used in this study consisting of three feeding phases. In phase one (7 days), all the hens received a CCC-free diet [165 g CP/kg dry matter (DM); 11.58 MJ ME/kg DM]. In phase two (11 days), four levels of 15N-CCC: 0, 5, 50 and 250 ppm were added to the respective diets, while in phase three (7 days), CCC-free feed was again offered. Egg samples were taken and the 15N content of egg yolk and albumin were determined. At the end of phase two, there was a significant (p < 0.05) increase in 15N content in egg yolk from hens fed the 50 and 250 ppm CCC diets and in albumin from hens fed the 250 ppm CCC diet. The estimated 15N-CCC residue was 1.71, 6.64, 28.80 ppm in egg yolk and 1.58, 1.08 and 4.50 ppm in albumin from hens fed 5, 50 and 250 ppm CCC, respectively. The CCC residue, from quantitative analysis ranged from 0.21 to 0.93 and 0.93 to 2.43 ppm in yolk of hens fed 50 and 250 ppm CCC, respectively, whereas a range of 0.40-1.46 ppm, was found in the albumin of hens fed 250 ppm. The difference in measured CCC in yolk and albumin and that estimated from 15N-CCC could have been due to breakdown products of 15N-CCC. Seven days after withdrawal of 15N-CCC, the estimated 15N-CCC residue in egg yolk decreased to 0.43, 2.45 and 15.59 ppm, on 5, 50 and 250 ppm CCC dietary treatments, respectively, and to 2.46 ppm in albumin from hens fed 250 ppm CCC. The higher increase in 15N content could have been due to a higher incorporation of 15N-CCC into yolk than albumin during the process of rapid yolk deposition. This experiment showed that consumed CCC is distributed both into yolk and albumin in a dose dependent manner and that CCC is metabolized in laying hens. However, the level of CCC in the diet which could lead to accumulation of detectable CCC levels in eggs as observed in this study, is much higher than the established maximum residual limits in grains.