Effects of dynamic feeding low and high methionine diets on egg quality traits in laying hens

This study was conducted to investigate effects of dynamic feeding low and high methionine (MET) diets on performance, egg quality traits, and serum metabolites in laying hens. A total of 180 laying hens (Brown Hy-line, 41 wk old) were allocated into 3 equal groups with 6 replicates each. The average egg production (EP) of each group was around 87% during one-week statistics before the formal experiment (P = 0.989). The control group (CON) received the control diet (contained 0.30% MET) at both 07:30 h and 15:30 hours. The low-high group (LH) received a low MET diet (containing 0.27% MET) at 07:30 h and high MET diet (containing 0.33% MET) at 15:30 hours. The high-low group (HL) received a high MET diet at 07:30 h and low MET diet at 15:30 hours. After 10 wk, blood samples were collected at 4-hour intervals in a daily cycle initially starting at 07:30 h before feeding. Results showed that the MET intake of a d was not influenced by the treatments (P > 0.05), respectively. The EP of the LH and HL group increased by 2.28 and 2.45% when compared with the CON group (P > 0.05). The hens in the LH group had a lower albumen ratio and thicker eggshell thickness than both CON and HL groups. Egg yolk ratio of the LH group was higher than the HL group (P < 0.05). The serum total cholesterol (TC), total triglyceride (TG), total protein (TP), and calcium (Ca) of the LH group was significantly lower at 07:30 h than the CON and HL groups, and the serum TG of the HL group was lower at 07:30 h than the CON group (P < 0.05). Meanwhile, the LH group also had the lowest value of serum TP at 23:30 h and 03:30 h (P < 0.05). These results demonstrated that dynamic feeding low and high MET diets might alter the circadian variation of serum TC, TG, TP, and Ca, which is consistent with the change of component ratio of egg albumen and yolk and eggshell thickness.