RESUMO
A total of five hundred forty 19-wk-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 6,800 mg/kg of corn-soybean meal-based diets on productive performance and egg quality. Phase 1 was from 19 to 58 wk, and phase 2 was from 59 to 68 wk. During the whole experimental period, dietary choline had no significant effects on feed intake, egg weight, and 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, BW decreased both linearly (P < 0.01) and quadratically (P < 0.05) as choline increased from 0 to 6,800 mg/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 850 mg of choline/kg significantly (P < 0.01) improved yolk color during phase 1. This study indicates that a dietary choline level of no more than 700 mg/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 wk of age.