Investigation Between High-fat Diet And The Incidence Of Cage Layer Fatigue And The Analysis Of Its Mechanisms

Feed is an important part of the breeding industry.According to the needs of different production practices,farmers usually choose diets with different formulas or make their own feed.The addition of oil in feed is beneficial to improving the efficiency of livestock and poultry breeding.Laying hens are fed a high-fat diet could promote the early start of laying and increase the weight of eggs.Recent studies have found that high-fat diet may be one of the potential causes of cage layer fatigue,especially in caged laying hens fed with a high-fat diet at the peak of egg production.The occurrence of this disease makes the production performance of the laying hen unable to function properly or even completely,which has a serious impact on the economic benefits of the laying hen culture industry.The hens with severe disease duration will suffer from fracture or even dead.In order to evaluate the correlation between high-fat diet and the incidence of cage layer fatigue,questionnaires and field surveys were used to calculate the feed use of hens in the chicken farms and the number of suspected laying hens.Made statistics on the number of cases of cage layer fatigue from 2013.1.1 to 2018.12.31 of a veterinary hospital,the size of the chicken farm in the corresponding case,the feed composition of the plant,the age of the diseased hens,and the onset season analysis.In order to clarify the pathogenesis of cage layer fatigue caused by high-fat diet,a model of high-fat diet-induced cage layer fatigue was established.88 21-week-old Roman white hens were divided into two groups.The control group was fed a normal full-price diet,and the high-fat group was fed a full-price diet mixed with 3% Jiu San brand soybean oil.Both groups of hens were fed a total mixed rations(TMR)feeding method with a test period of 17 weeks.At the 5th week(26 weeks old),9 weeks(30 weeks old),13 weeks(34 weeks old),17 weeks(38 weeks old),10 eggs were randomly selected from each group for the detection of eggshell quality.10 hens were randomly selected from each group for cardiac blood sampling,and the jugular vein was sacrificed and dissected.Serum samples were collected for serum blood bone metabolism indicators(Ca,P,OCN,OPG,ALP,TRACP,PTH,E2 and PROG),detection of lipid metabolism markers(TG and TC)and detection of LC-MS metabolomics;collection of bone tissue samples for bone mineral density,bone biomechanical properties(stiffness,flexural modulus,flexural rigidity and maximum load),bone morphometry(bone length,bone index),bone trace element content detection(Ca,K,Na,Mg,Fe,Zn,Sr,Al,Ba,Cr,Cu,Mn,and Se)and bone sections Preparation.In order to clarify the pathogenesis of cage layer fatigue caused by high-fat diet from the perspective of bone metabolism and lipid metabolism.The test results are as follows:(1)The high-energy diets of 63 feeds accounted for 50.79%,and the number of suspected cases had a positive relationship with the use of high-energy diets;Of the 89 cases confirmed to have cage layer fatigue,13 have been fed by high-energy level feed,accounting for 30.34% of the total.(2)Compared with the control group,the high-fat group had a decrease in production performance,which was mainly due to decrease feed intake,decrease egg production rate,and increase egg breakage rate,but had no significant effect on eggshell quality.(3)The bone mineral density and bone biomechanical properties of the high-fat group were significantly lower than those of the control group(p < 0.05),the bone microstructure was impaired,and osteoporosis such as trabecular bone thinning,loosening,and enlarged bone marrow cavity occurred.Changes,ALP,OCN,OPG,TRAP and PTH levels were significantly higher than the control group and Ca content was significantly decreased(p < 0.05),indicating that high-fat diets promote bone anabolism and bone breakdown,absorption and metabolism.And its promotion effect on bone resorption of bones is more intense,that is,high-fat diet promotes osteoclast absorption rate over bone synthesis rate by regulating bone metabolism,and induces cage chicken laying fatigue syndrome;(4)Compared with the control group,the high-fat group showed a significant increase in TG and TC levels(p < 0.05),indicating that the high-fat diet affected the level of lipid metabolism,the fat accumulation of the laying hens,and the decline in constitution,and thus the susceptible caged laying hens Fatigue syndrome(5)Based on LC-MS metabolomics test,the serum samples of the high-fat group and the control group were analyzed.The screening analysis showed that the metabolites were significantly different and the abdominal muscles obtained five significantly activated signal pathways.Above all,there are two pathways including tryptophan metabolism and aldosterone synthesis and secretion closely related with bone metabolism and lipid metabolism.It is indicated that high-fat diets mainly participate in bone metabolism and lipid metabolism by disrupting these two signaling pathways.And then induced cage chicken laying fatigue syndrome.To sum up,this study found that cage-laying hens were more prone to cage layer fatigue when using high-energy diets.Animal experiments showed that high-fat diet could promote bone resorption by down-regulating the blood Ca concentration and improving the PTH level,and at the same time,up-regulating the OPG level to promote bone synthesis,which was manifested as significantly increased serum OCN and ALP levels.Finally,because the bone resorption rate was higher than the bone synthesis rate,a large amount of bone loss caused by cage layer fatigue.By upregulating the levels of TC and TG content,high-fat diet causes disorder of lipid metabolism in the body,which leads to fat accumulation.On the one hand,osteogenic related proteins in the body are inhibited;on the other hand,the declining constitution of laying hens due to obesity makes them much more susceptible to cage layer fatigue.Two signaling pathways was closely related to lipid metabolism and bone metabolism,which were obtained by metabolomics analysis of significantly different metabolites.It was confirmed that high-fat diet may induce fatigue syndrome in caged layers by regulating lipid metabolism and bone metabolism in layers.This study provides a basis for further elucidation of the potential pathogenesis of cage layer fatigue,and lays a foundation for the establishment of early warning and prevention system for cage layer fatigue induced by high-fat diet.