The Etiology And Pathogenesis Of Crus Hemorrhage In Pekin Ducks

During the Pekin ducks production,the muscle bleeding spot phenomenon in crus(crus hemorrhage)was found,which greatly reduced the Pekin duck carcass quality,leading to huge economic losses to the enterprise.However,the character of crus hemorrhage in Pekin duck and its pathogenesis remained unclear.This study was conducted to explore the epidemiologic characteristic and pathogenesis of crus hemorrhage in Pekin duck,to provide some theoretical basis for the prevention of crus hemorrhage in Pekin ducks.In order to study the epidemiology of crus hemorrhage in Pekin ducks,we monitored the incidence of the disease in a duck farm in Beijing from 2014 to 2017.Meanwhile,777 Pekin ducks were dissected to describe the characteristic.The results showed that the incidence of crus hemorrhage in year 2016 and 2017 were higher than that in year 2014 and 2015(without feeding).The annual incidence rate increased from 0.27%to 2.84%.Forced feeding significantly increased the morbidity of disease(P<0.001).The unilateral morbidity accounted for 72.2%,which was significantly higher than bilateral(P<0.001).However,there was no difference of the morbidity of left and right crus(P>0.05).The anterior part of the gastrocnemius muscle was the main site of the disease(P<0.001),occupying 58.7%.There was no significant difference in the morbidity between the sexes,accounting for almost 50%.The percentage of Pekin ducks with carcass weight more than 2.9 kg was higher than that of lean ducks(P<0.001).Histopathological analysis of the muscle revealed that large blue stains were observed Prussian blue staining,indicating that it belonged to the stale hemorrhage.The bacterial culture results of visceral organs and diseased muscles were negative,suggesting that common bacterial infections were not necessary for the disease.The results also indicated that forced feeding was the main risk factor for the disease.In order to study the pathophysiological parameters of crus hemorrhage in Pekin ducks,300 Pekin ducks were divided into 2 groups,250 in the feeding group and 50 in the control group.After fasting,10 Pekin ducks from forced feeding(diseased)and control groups were collected,respectively.The blood were tested for rheology,fat metabolism,and inflammatory mediators.The results showed that the whole blood viscosity and whole blood reduced viscosity of diseased ducks were significantly higher than that of the control group(P<0.001).Fat metabolism of diseased ducks was changed,among which triglycerides,low-density lipoproteins,very low-density lipoproteins,and oxidation low-density lipoprotein and free fatty acid levels increased significantly(P<0.05);The serum corticosterone,reactive oxygen species,tumor necrosis factor-a(TNF-a)content,and interleukin-1(IL-1)levels in the diseased group were increased as well(P<0.05).The total antioxidant capacity and glutathione peroxidase activity of liver and muscle were decreased.The inflammatory media including IL-1IL-6 and TNF-a were significantly increased(P<0.05).The vascular injury markers involving nitric oxide and endothelin-1 were significantly increased.In conclusion,crus hemorrhage in Pekin ducks caused the increased blood viscosity,fat metabolism changes.Meanwhile the release of inflammatory mediators exacerbating the vascular endothelium inflammatory injury.In order to explore the pathogenesis of crus hemorrhage in Pekin ducks,liver,muscle transcriptomics and serum metabonomics were studied.The results showed that there were 830 differentially expressed genes in the liver,428 genes were up-regulated,and 402 genes were down-regulated.Fatty acid synthesis metabolism were significantly enhanced in the diseased group.The differential genes were mainly enriched in cellular components including nucleosome assembly and DNA-protein assembly.They took charge in metabolic processes,and played a role in molecular function such as redox activity and catalytic activity.And the genes were significantly enriched in 27 metabolic pathways,including proteasome,phosphoglycerol metabolism and pentose phosphate pathway pathways.There were 2893 differentially expressed genes in muscles,2020 up-regulated and 873 down-regulated.The markedly enriched Go classification is mainly in the mitochondria,taking part in the respiratory electron transport chain,and the immune system's positively regulated biological processes,to exert redox,catalysis,and binding molecular functions.Differential genes were significantly enriched in 28 KEGG metabolic pathways,including oxidative phosphorylation pathways,fatty acid metabolism,and Toll-like receptor signaling pathways.The metabolomic analysis revealed that there were 160 differential metabolites in the serum.The main metabolites were phospholipids,and particularly lysophosphatidyl cholines,which could be used as candidate metabolites of crus hemorrhage in Pekin ducks.All differential metabolites were significantly enriched in 13 KEGG metabolic pathways,including sphingolipid metabolism,biosynthesis of unsaturated fatty acids,and glycerophospholipid metabolism.The mobidity of crus hemorrhage in Pekin ducks from 2016 to 2017 were significantly higher than the that of in year 2014 and 2015,which are related to forced feeding.Increased blood viscosity and fat metabolism changes are involed in crus hemorrhage in Pekin ducks.And the increased release of inflammatory mediators exacerbated the body's inflammatory lesions.In addition,The redox activity and the inflammatory response expecially Toll-like receptor signaling pathway and sphingolipid metabolic pathway is related to crus hemorrhage in Pekin ducks.Lysophosphatidylcholine can be used as a candidate metabolite of Beijing duck crus hemorrhage.