Effects And Mechanism Of Feed Restriction On Laying Performance And Egg Quality Of Laying Hens

This study was conducted to investigate the effects of 15%food restriction on the laying performance,organ index,egg quality,blood index,lipid metabolism,follicle development,caecum microorganism,the shape of the duodenum,digestive enzymes and antioxidant of Lohman layers.The aim is to provide a practical basis for the health of laying hens.Total 432 18-week-old Lohman layers were allocated to two group.Each group have nine repeats,each repeat has 24 laying hens.Including the Ad libitum and the restricted feeding（85%feed intake of the Ad libitum at last week）.The experiment was 34weeks in total,including the restricted feed period for 30 weeks（the hens were 18-47weeks old）,and the 4 weeks free feeding after restricted period（the hens were 48-51 weeks old）.The results showed that:（1）The restricted feeding significantly decreased the laying rate,egg weight,FCR,egg number and the number of qualified egg（P<0.05）.When the hens were free feeding after restricted,the laying rate was increased in the restricted group.（2）The restricted feeding significantly decreased the absolute weight of gizzard and the absolute length of the ileum（P<0.05）,significantly increased the relative weight of the jejunum and the relative length of the jejunum and the cecum（P<0.05）,significantly increased the villus height and crypt depth（P<0.05）,significantly decreased the activity of duodenal trypsin and amylase（P<0.05）.Through the determination of 16S RNA,the abundance and diversity of cecal microflora in the restricted group were significantly higher than that of free feeding group（P<0.05）.The dominant bacteria group of the phylum level was bacteroides and firmicutes.Compared with the Ad libitum group,the content of Rikenellaceae in the family and Rikenellaceae-RC9-gut-group in the general level were increased（P<0.05）.（3）The restricted feeding significantly decreased the body weight,adipose tissue and carcass fat（P<0.05）.The concentration of serum total bile acid（TBA）,uric acid（UA）,total cholesterol（TC）,triglyceride（TG）and very low density lipoprotein cholesterol（VLDL-C）were significantly increased in the serum of laying hens（P<0.05）.Restriction feeding significantly decreased the optical density（P<0.05）of liver oil red O slices and reduced the deposition of fat in the liver.Limited feeding significantly increased the expression of fatty acid synthase（FAS）,Acetyl Co A carboxylase（ACC）,carbohydrate response element binding protein（Ch REBP）and peroxisome proliferator activated receptorγ（PPARγ）gene in the liver（P<0.05）.Limited feeding significantly increased the transport of fat in the liver and the liver.Related expressions of very low density lipoprotein（VLDL）,Microsomal triglyceride transfer protein（MTP）,apolipoprotein B（apo B）and liver type fatty acid binding protein（L-FABP）gene expression（P<0.05）.Limited feeding significantly increased the peroxisome proliferation activated receptorα（PPARα）and lipoprotein lipase（L）associated with fat decomposition in the liver.PL)gene expression（P<0.05）.The expression of Acetyl Co A carboxylase（ACC）,Adiponectin fatty acid-binding protein（A-FABP）,lipoprotein lipase（LPL）and triglyceride hydrolase（ATGL）gene were significantly increased in abdominal fat（P<0.05）.Restriction feeding significantly increased liver superoxide dismutase（SOD）activity（P<0.05）and improved liver health.（4）the concentration of serum estradiol（E2）,testosterone（T）and leptin（Leptin）was significantly reduced（P<0.05）,and the concentration of three iodine thyroid prolysine（T3）and insulin like growth factor-1（IGF-1）was increased（P<0.05）.Limited feeding significantly increased the proliferation cell antigen（PCNA）,peroxisome proliferator activated receptorγ（PPARγ）,bone morphogenetic protein 15（BMP15）,BMP15 receptor1B（BMPR1B）,BMP15 receptor 2（BMPR2）,estrogen receptor（ESR1）,follicle stimulating hormone receptor（FSHR）,and extremely low density lipoprotein cholesterol.The expression of alcohol receptor（VLDLR）gene（P<0.05）promotes follicular development.Restriction feeding significantly decreased superoxide dismutase（SOD）activity（P<0.05）in the ovary.The results suggest that the possible mechanisms for the decrease of laying performance by 15%restricted feed intake were:one was the nutrient intake the decrease even with the increase of the body mobilization that was not enough to the egg laying requirement.The second was the decrease of the serum estradiol（E₂）,testosterone（T）,the lower antioxidant ability of ovary,the increase of gene expression of PCNA,PPARγ,BMP15,BMPR1B,BMPR2,ESR1,FSH and VLDLR in the ovary that improves the differentiation and apoptosis rate of follicle granulosa cells.The feed restricting improved the feed utilization by improving the growth of parts of the intestine,increase the villus height,improve the abundance and diversity of the microflora in cecum with the increase of the Rikenellaceae family and the Rikenellaceae-RC9-gut-group in the general level.Feed restricting decreased the mortality of the laying hens,body weight,fat tissue percentage,fat contents in body and liver,improve the liver antioxidant,then that was beneficial to the decrease of the fatty liver hemorrhage syndrome.It was related to the increase of the gene expression of liver FAS,ACC,Ch REBP,PPARγ,MTP,apo B,L-FABP,PPARα,and LPL.