Study On Changes Of Production,Physiological Metabolism And Intestinal Health Of Laying Hen During Molting

Forced molting as an important management technology,it can has been used extensively for extending flock production cycle and improve economic efficiency,and has attracted widespread attention in domestic chicken industry in recent years.This study was therefore designed to characterize the dynamic changes of production performance,egg quality,and serum biochemical,immune and antioxidant indicators,observe the mucosal morphology and S-Ig A level and analyze the composition and abundance of intestinal microbial populations by using 16 S rDNA amplicon sequencing of hens during a whole fast-induced molting process,hoping reveal the effects of forced molting on production performance,physiological metabolism and intestinal health of laying hens.Exp.1 Regularity analysis of production performance,serum biochemical and antioxidant indices of laying hens during forced moltingA total of 400 healthy "Jinghong No.1" laying hens(509-day-old,approximately 75% of egg production rate)were selected for fast-induced molting.The experiment was randomly divided into four treatments,which were before molt(T1),during fasting(T2),post molt(T3)and peak production(T4).Each treatment consists of 10 replicates with 10 birds per replicate.The trial period was 60 days.The results showed that:(1)Compared to the first production cycle,the molted hens entered into the second production cycle quickly and the egg production rate increased faster.Compared with T1,the highest laying rate in the postmolt production cycle was 87%.Significant difference in the egg quality was seen among T1,T2,T3 and T4(P<0.05).The shell thickness,shell strength,and yolk color decreased and then increased in the molting procedure(P<0.1)and they were significantly lower in T2 than T1(P<0.05).The egg shape index,albumen height,and Hangh Unit increased and then decreased in the procedure(P<0.1),and they were significantly higher in T3 and T4 than T1(P<0.05).Compared with T1,the egg shape index decreased significantly in T3 and T4(P <0.05).(2)During the molting period,the serum globulin(GLO),triglyceride(TG),and uric acid(UA)of the laying hens showed a trend of decreasing first and then increasing(P<0.1),and the TG and UA in T3 and T4 were significantly higher than T1(P<0.05);while the ratio of albumin to globulins(A/G)showed a trend of increasing and then decreasing(P<0.1),and A/G in T2 was significantly lower than T1(P<0.05).(3)The level of serum total superoxide dismutase(T-SOD)increased and then gradually decreased during the whole molting period(P<0.05).The T-SOD in T3 and T4 was significantly higher than that in T1(P<0.05).For Ig A and Ig G,they showed a fluctuation of decreasing first and then increasing during the molting process(P<0.1),and they were significantly lower in T3 and T4 than those in T1(P<0.05).Exp.2 Regularity analysis of the dynamic changes of intestinal health-related indicators of laying hens during forced moltingThe design of this experiment was the same as that of the first experiment.The results showed that:(1)For laying hens during the whole fast-induced molting,the villous height(VH)and the ratio of villous height to crypt depth(V/C)of duodenum,ileum and jejunum showed a trend of declining and then gradually increasing(P<0.1),and the VH and V/C in T3 were significantly higher than those in T1(P<0.05).(2)The S-Ig A content of the small intestinal mucosa of the hens during molting period changed significantly(P<0.05),and the S-Ig A of T2,T3 and T4 was significantly higher than that of T1(P<0.05).(3)The dominant spoilage bacteria in the cecum samples of laying hens in T1 was significantly different from T1,T3 and T4(P<0.05);the bacteria composition in T1 was significantly different from T1,T3 and T4(P<0.05);compares with pre-molt,the community composition did not change significantly after molting(P>0.05);compared with T1,the relative abundance of Proteobacteria,Actinobacteria and Synergistetes increased significantly(P>0.05),while the Proteobacteria and Actinobacteria in T3 were significantly lower than those in T1(P<0.05).For alpha diversity,the Shannon,Chao1 and ACE index of T2 were significantly lower than those of T1,T3 and T4(P<0.05).Conclusions:(1)Fast-induced molting can stimulate the second-cycle production of laying hens and improve egg quality.Fast-induced molting had a significant effect on serum biochemical indicators of hens.Forced molt can significantly improve the antioxidant ability of molted hens,but weakened the immune function of body.(2)In the process of fast-induced molting,the small intestine morphology and S-Ig A level of laying hens showed significant changes.Forced molting significantly improves nutrient digestion and absorption in laying hens of molted hens.In addition,forced molting significantly affected the microbial richness and diversity,gut micro flora composition,and the dominant intestinal flora in laying hens undergoing starvation.