A Preliminary Study On The Effect Of Disequilibrium Feeding On Eggshell Quality Of Laying Hens In The Later Stage Of Laying And Its Mechanism

In the later stage of laying,the production performance of laying hens decreased,the eggshell was fragile and the loss of bone calcium was serious.The purpose of this experiment is to study a new feeding technique based on laying physiology.Without improving the nutritional level of the diet and changing the daily feed intake,increase the retention time of chyme and calcium in the digestive tract at night.In order to achieve the purpose of improving the utilization rate of dietary nutrients,especially calcium,and improving the eggshell quality and production efficiency of laying hens in the later stage of laying.A total of 28870-week-old healthy Hy-Line brown laying hens were random Ly divided into 4groups using a two-factor design.The hens were fed at 8:00 and 14:00 every day.Hens in NCA(Low calcium disequilibrium feeding)group and NCD(Normal calcium disequilibrium feeding)group were fed a conventional Ca level diet with3.5% Ca content.Hens in NCA group were fed half and half of the whole day’s feed twice,and those in NCD group were fed 1/3 and 2/3 of the whole day’s feed twice,respectively.Piglets in LCA(Low calcium)group and LCD(Low calcium disequilibrium feeding)group were fed a low calcium diet containing 3.0% Ca,piglets in LCA group were fed the same way as NCA group,and piglets in LCD group were fed the same way as NCD group.Each group had 6 replicates with 12 chickens per replicate,and the experiment lasted for 8 weeks.The results are as follows: Production performance:(1)Disequilibrium feeding could significantly reduce the average daily feed intake and feed / egg ratio(P < 0.01),and increase the laying rate and average egg weight,but the difference was not significant(P > 0.05).(2)Disequilibrium feeding could significantly increase eggshell thickness,eggshell weight and shell weight ratio(P < 0.05),improve eggshell quality,and significantly increase eggshell fence thickness and total thickness(P < 0.05).The ultrastructure of eggshell was improved.Calcium metabolism:(3)There was significant interaction between dietary calcium level and feeding method on eggshell calcium content(P < 0.05),conventional calcium content or disequilibrium feeding could increase eggshell calcium deposition,(4)There was no significant difference in plasma calcium concentration among all factors(P > 0.05),and maintained a relatively stable state within one day.The serum phosphorus concentration was significantly affected by dietary calcium content and time factors(P < 0.05),and showed significant regular changes within one day.(5)Time factors and feeding methods had extremely significant interaction on tibial bone calcium content(P < 0.01).The bone calcium content in the night disequilibrium feeding group was significantly higher than that in the normal feeding group,indicating that disequilibrium feeding could reduce bone calcium mobilization in the tibia at night.(6)The content of calcium and phosphorus in feces is extremely significantly regulated by time(P<0.01).The calcium content of feces during the day is higher than that at night,and the phosphorus content of feces at night is higher than that during the day;the calcium content of feces is also extremely significantly regulated by the calcium level in the diet(P<0.01),the fecal calcium content of the lowcalcium group was significantly lower than that of the conventional calcium content group(P<0.01),indicating that diets supplemented with 3.5% calcium had more calcium unused;feeding methods have a tendency to affect the fecal calcium content(P=0.075),disequilibrium feeding may have the effect of reducing calcium excretion in feces.Intestinal tract:(7)There was a significant interaction between dietary calcium level and feeding method on the depth of duodenal recess(P < 0.05).The crypt depth in),LCD group was significantly lower than that in LCA group(P <0.05).Disequilibrium feeding with low calcium could improve intestinal morphology and be beneficial to the absorption of nutrients.(8)Disequilibrium feeding significantly increased the thickness of duodenal mucous layer,the expression of tight junction protein Occludin and mucin MUC-2.There was a significant interaction between dietary calcium content and feeding method on the expression of Occuldin and Zo-1 in duodenum.Disequilibrium feeding under conventional calcium content could increase the expression of Occuldin and Zo-1,indicating that this feeding method could reduce intestinal injury,which may lead to the improvement of intestinal permeability.(9)Disequilibrium feeding significantly increased the expression of Ca BP in jejunum and tended to increase the expression of PMCA in duodenum(P = 0.062),indicating that disequilibrium feeding could promote the absorption of calcium in small intestine.(10)Disequilibrium feeding may increase the abundance of Firmicutes,Ruminococcaceae and Lachnospiraceae,decrease the abundance of Bacteroidete and Parabacteroides,improve intestinal permeability,protect intestinal mucosa,and improve the utilization rate of intestinal nutrients.To sum up,the disequilibrium feeding method can improve the intestinal health of laying hens in the later stage of laying,which may be caused by the change of intestinal microflora caused by disequilibrium feeding.Intestinal health promotes the absorption of nutrients such as calcium,slows down the loss of bone calcium and increases the deposition of eggshell calcium,which ultimately plays a role in improving production performance and improving eggshell quality.