What to Do About Iron Supplement Allergy in Piglets? A Detailed Guide to Prevention and Treatment
A Detailed Explanation of Iron Supplement Allergic Reactions in Piglets, and How to Prevent and Treat Them
1. Reasons for iron supplementation in newborn piglets
After a piglet is born, the amount of iron stored in its body is about 50 mg. The amount of iron needed for normal growth of a piglet is at least 7 mg per day, while breast milk can provide about 1 mg of iron per day, which is not enough to meet the normal growth needs of the piglet. As the age in days increases, the iron content in breast milk continuously decreases, while the piglet's need for iron increases. For the pig to grow healthily and quickly, we must promptly, quickly, and effectively supplement it with enough high-quality iron after birth. ⟦6 2. Toxicology of iron allergic reactions
2. Toxicology of iron hypersensitivity reactions
Since iron is a trace element essential to pigs and the required amount is relatively large, its toxicity is relatively low. After iron is absorbed by pigs, it is distributed throughout the body, mainly in the blood, liver, and spleen, followed by the kidneys, heart, skeletal muscle, and brain. The iron content in the pig's liver is very high. However, the pig's ability to excrete iron is very limited. Loss through bile and the shedding of mucosal epithelial cells is the main route of endogenous iron loss, and very little iron is excreted in feces and urine. Therefore, excessive iron supplementation can easily cause iron allergy in piglets. According to the principles of biochemical toxicology, iron entering the body is often absorbed in the form of Fe2+, and after being oxidized to Fe3+ it is transported. When the concentration of Fe3+ in the blood exceeds the binding capacity of transferrin, Fe3+ precipitates as Fe(OH)3. Because the massive precipitation of Fe(OH)3 releases excess H+, metabolic acid allergy occurs. After Fe3+ complexes accumulate in the liver, they can inhibit the activity of glucose-6-phosphatase and succinate dehydrogenase, reduce liver function and cause liver cell damage, followed by hepatic steatosis, liver cell necrosis, and even portal cirrhosis leading to death.
3. Symptoms and pathological changes of iron allergic reactions in piglets
3.1 Symptoms
The clinical features of acute iron allergy in piglets are mainly diarrhea, vomiting, lethargy, and difficulty breathing. Within 24-48 h, shock occurs with a drop in blood pressure and convulsions. In acute iron allergy, the blood CO2 combining power decreases, platelets decrease, the total white blood cell count increases, SGPT (alanine aminotransferase) and SGOT (aspartate aminotransferase) activity increase, and serum iron concentration increases. The main clinical symptoms of chronic iron allergy are increased serum iron and serum ferritin levels. There is a large amount of iron deposition in the liver, spleen, pancreas, and skin, and heart failure. After piglets are injected with iron dextran and develop allergy, the clinical manifestations occur and the piglets soon die.
3.2 Pathological changes
The main pathological change of iron supplement allergy is the deposition of hemosiderin in hepatocytes and macrophages. Wang Baoqin et al. [2] believe that in chronic iron allergy, the histopathological changes in the liver are relatively typical, mainly characterized by mild to moderate focal hepatitis and iron deposition granulomas accompanied by high iron overload. Almost the entire hepatic lobule has iron deposition and strongly positive Perl's staining, accompanied by obvious inflammatory lesions; the iron deposition bodies are numerous and large, often accumulating in clumps or sheets, mainly concentrated in the hepatocytes from the portal area to around the central vein. There are large amounts of hemosiderin granules in the Kupffer cells in the hepatic sinusoids and in the spleen, and there are also large amounts of hemosiderin granules in the macrophages in the alveolar septa of the lungs and in the myocardial interstitial cells. Hemosiderin granules are widely distributed in the hepatic lobules, Kupffer cells, macrophages, bile duct epithelial cells, and connective tissue.
4. Causes of iron supplement allergy in piglets
4.1 The molecular weight of iron dextran is too large
At present, the main component of most intramuscular iron supplements on the market is iron dextran. If the production process of iron dextran is unscientific, bruising and lumps may appear at the injection site of piglets after injection of the iron supplement. This is a typical symptom of poor absorption of the iron supplement by piglets. Generally, the molecular weight of iron dextran for injection is 10000u-12000u, while an excellent iron supplement can reach 5000u-7500u. The smaller the molecular weight, the better the absorption by piglet muscle and the less likely allergic reactions are to occur.
4.2 Too many impurities in iron dextran
Iron dextran is a complex formed by the complexation of ferric hydroxide with dextran. It is a brown to brown-black crystalline powder, easily soluble in hot water, and forms a dark brown colloidal solution. At present, in the chemical synthesis process for producing iron dextran, substances such as ferric chloride, sodium hydroxide, and ethanol participate in the reaction, and these substances are highly irritating to piglets. If the content of these impurities in iron dextran is too high, allergic reactions will be induced in piglets after injection. In addition, high molecular weight dextran, protein, and excessive heavy metals can also easily cause allergy in piglets.
4.3 The iron content of the iron supplement is too high
The combination of ß1-globulin with iron in the blood is rapidly saturated, and iron excretion is limited, so excess iron becomes an unbound toxic substance. Wang Xuemei's research suggests that when the body continuously takes in too much iron and exceeds the storage capacity of ferritin, iron accumulates in hepatocytes in the form of hemosiderin, causing hepatocyte damage. Excess iron can cause severe damage to the immune system, liver, lungs, kidneys, and other organs of piglets, reducing the body's immune function.
4.4 Piglets lack vitamin E
Piglets born to sows deficient in vitamin E are extremely sensitive to iron-containing drugs. Iron supplementation can aggravate the level of oxidative stress and lipid metabolism disorder in pigs, while vitamin E can alleviate the oxidative stress and lipid metabolism disorder induced by iron supplementation in pigs. Eighteen hours after acute iron allergy, although most of the iron is taken up by the reticuloendothelial system, obvious accumulation of iron can also be seen in testicular tissue. As the iron content in testicular tissue increases, the content of the lipid peroxidation product TBARS (2-thiobarbituric acid-reactive substances) in the tissue increases, while the content of antioxidant vitamin E in the tissue decreases accordingly. Vitamin E supplementation has no effect on iron accumulation in testicular tissue, but it can significantly reduce the content of the lipid peroxidation product TBARS in testicular tissue.
4.5 Genetic factors
Allergic piglets are related to the genetics of the sow and the breeding boar. The innate genetic factors of the sow can cause allergic reactions to iron preparations in piglets. With the genetic improvement of pig breeds, the incidence of this disease is on the rise. Allergic cases are more common in two-way and three-way crossbred pigs and supporting-line lean-type pigs, accounting for 80% of affected pigs, while the incidence in local breeds is relatively low.
5、TreatmentMethods
Pig farms generally use epinephrine (1 mg per vial), injecting 1 vial intramuscularly per piglet, and recovery occurs after about 2 hours. For piglets with severe reactions, symptomatictreatmentcan be carried out, with intramuscular injection of 10% sodium thiosulfate 400 mg/kg, vitamin C 100 mg, and vitamin B1 100 mg. It is reported that this therapy has a relatively obvious effect.