Investigation And Studying The Pathogenesis Of Blackened Large Intestines In Slaughtered Pigs

Copper is one of the indispensable trace elements in the body.Copper ions participate in many important metabolic pathways and are important components of many enzymes.The biological function of enzymes regulates the life activities of many links,such as cell respiration,uptake of related metal ions,neurotransmitter conduction,anti-stress,anti-oxidation and so on.Copper and iron,zinc,manganese,iodine and selenium belong to trace elements that must be added to pig feed.In order to promote pig growth or appearance health and the black stool about "Health Appearance".The problem of excessive addition of trace elements such as copper,iron and zinc to pig feed is common,and the phenomenon of excessive addition of dozens of times or even hundreds of times occurs frequently.Since the large-scale pig farming,the problem of blackened large intestines in slaughtered pigs has always been the focus of attention.In recent years,this problem has become more serious.The proportion of blackened large intestines in slaughtered pigs has been increasing.The serious pig population can reach up to 40%.People have speculated that the above problems are related to the excessive addition of trace elements in high-copper and high-iron feed.Considering food safety and animal health welfare,a series of investigations and laboratory tests were carried out on black large intestines in slaughtered pigs about the incidence,causes,pathological changes,occurrence mechanism and the harm to animal organisms.First,we Detection the content of 12 kinds of metal ions in Cu,Zn,Mn,Al,Cr,Fe,Co,Ni,As,Se,Cd and Pb in 17 black intestines and 2 white intestines.The test results show that there is a serious excess of copper ions in the blacken large intestines,and there is a certain problem of excessive iron ions.According to this clue,we randomLy selected 22 kinds of full-price pig feed on the market and detected the contents of seven metal ions,Fe,Cu,Zn,As,Cd,Pb and Cr.It is found that most of the detected feeds have problems with excessive Cu?Fe and Zn.We went to the pig slaughter to conduct a site survey of the black large intestine problem.The survey results showed that the detection rate of pigs' blackened large intestines were higher from May to October,and the average detection rate was about 20% in this season;The proportion of pigs' large intestines from small-scale pig farms or retail investorstends to be higher,Some pigs' blackened large intestines rate can also up to 95%.However,the detection rate from large-scale pig farms is relatively low,generally no more than 5%.In order to understand the pathological characteristics of the black large intestine,The paraffin sections of pigs' blackened large intestines tissue were stained with HE,copper salt and Prussian blue.Microscopic observation showed that a large number of brown macrophages were aggregated in the lamina propria of intestinal mucosa stained by HE,and see the brown powdery scattered.Intestinal mucosal epithelial cells showed some degeneration and necrosis,and there was no obvious inflammatory reaction in lamina propria;The brown macrophages and powders object were stained with copper salt showed dark-green positive reaction,while Prussian blue stained slightly blue.In order to understand the pathological characteristics of the black large intestine,The paraffin sections of pig blackened large intestines tissue were stained with HE,copper salt and Prussian blue.Microscopic observation showed that a large number of brown macrophages were aggregated in the lamina propria of intestinal mucosa stained by HE,and see the brown powdery scattered.Intestinal mucosal epithelial cells showed some degeneration and necrosis,and there was no obvious inflammatory reaction in lamina propria;The brown macrophages and powders object were stained with copper salt showed dark-green positive reaction,while Prussian blue stained slightly blue.In order to verify whether excessive copper addition in feed will lead blackened large intestines in pigs,According to the results of the investigation of excessive copper ions in the pig feed,different Cu content feeds were set.we chose 100 BALB/c mice instead of pigs to carry out animal experiments.The experimental results showed that the blackened large intestines of mice in the high copper feed group had different degrees of blackening.Cecum is the most prominent,and the colour of the small intestine also changed with the prolongation of feeding time.The black large intestines tissue of the mice was subjected to conventional paraffin sectioning,HE staining,copper salt staining,and Prussian blue staining.Microscopic observation revealed similar lesions in the black large intestines of pigs and the intestinal mucosal epithelial cells were apoptotic.Copper ions are mainly enriched in the black large intestines and liver tissue,then cause a certain degree of tissue damage reaction even lead to acute death of animals.The results of this experiment also confirmed that high-copper feed within a certain range has a certain promoting effect on animal growth,but it has caused serious damage to the animal's physical and mental health and animal welfare.This study preliminary answered the long-term confusion of the occurrence and property of slaughtering pigs' blackened large intestines,also provided a theoretical basis for the safetycontrol of meat food and the protection of animal welfare in China.