Choline at no more than 700mg per kg is sufficient to maintain egg production, with only minimal effects on egg quality between 19 and 68 weeks of age when the hens were fed a corn-soybean meal-based diet.

Those are the conclusions drawn by Q.H. Zhai of the Chinese Academy of Agricultural Sciences, Beijing and co-authors after a study into the long-term effects of choline on productive performance and egg quality of brown-egg laying hens.

In a paper in Poultry Science, they report that a total of 540 19-week-old HyLine Brown hens were used to study the long-term effects of increasing choline with 0 (control), 425, 850, 1,700, 3,400 and 6,800mg per kg of corn-soybean meal-based diets on productive performance and egg quality.

Phase 1 was from 19 to 58 weeks, and phase 2 was from 59 to 68 weeks.

During the whole experimental period, dietary choline had no significant effects on feed intake, egg weight or egg mass (P>0.05).

During phase 1, egg production decreased linearly (P<0.05) and feed conversion ratio (FCR) tended to increase linearly (P=0.057) with increasing choline level in the diet. Moreover, bodyweight decreased both linearly (P<0.01) and quadratically (P<0.05) as choline increased from 0 to 6,800mg per kg.

No significant treatment effects were found for shell thickness and shell strength of eggs (P>0.05). However, albumen height and Haugh units increased linearly (P<0.01 and P<0.05, respectively) as choline increased during phase 2.

Compared with the control group, diets supplemented with 425 or 850mg of choline per kg significantly (P<0.01) improved yolk colour during phase 1.

Zhai and co-authors concluded that a dietary choline level of no more than 700mg per kg is sufficient to maintain egg production. The effect of choline on egg quality was minimal when hens were fed a corn-soybean meal-based diet from 19 to 68 weeks of age.

Reference

^{Zhai Q.H., X.F. Dong, J.M. Tong, Y.M. Guo and Y.E. Bao. 2013. Long-term effects of choline on productive performance and egg quality of brown-egg laying hens. Poult. Sci. 92(7):1824-1829. doi: 10.3382/ps.2012-02854}