Etiology, prevention and treatment of nitrite poisoning in beef cattle

With the continuous expansion of the market demand for beef, more and more people begin to raise beef cattle. After the scale reaches a certain extent, it is inevitable to start storing some food for beef cattle to eat. If the storage method is not correct or the feeding method is not correct, it is easy to cause food poisoning in beef cattle, among which nitrite poisoning is the most common. The sudden onset of nitrite poisoning often takes people by surprise and brings a lot of economic losses. Therefore, special attention should be paid to it in daily production. The following is to introduce the cause of nitrite poisoning in beef cattle and what to do after nitrite poisoning occurs in beef cattle.

1. Etiological analysis

The source of nitrite is nitrate, which itself is basically non-toxic, but it is toxic if it is reduced to nitrite. A variety of cereal crops and vegetables in feed contain some nitrates, including various wild vegetables, forage grasses, crop seedlings and straws (especially oat stalks), tubers such as potatoes, radishes and sugar beets, and leafy vegetables such as spinach, rape and cabbage. Nitrate is rich. In addition, for the same plant, the nitrate content will change significantly in different regions and different years, which is mainly determined by the balance between the generation, absorption, decomposition and utilization of nitrate in the plant. Ferocious elements that can promote the production and absorption of nitrate, such as fertile soil and the application of large amounts of nitrogen fertilizer, as long as they can inhibit nitrate utilization and protein assimilation, such as lack of light, lack of trace elements such as iron, copper, manganese, aluminum, and the use of herbicides, will lead to an increase in the level of nitrate in plants. In addition, plants harvested at different stages or treated by different methods will also lead to different levels of nitrate. For example, the nitrate content of crops decreases at heading stage, and also decreases after silage treatment, but there are often high levels of nitrate in silage exudation and water sources adjacent to garbage dumps. Cattle are prone to nitrite poisoning after eating a large amount of nitrate.

Herbage, vegetables and scraps of agricultural and sideline products are stacked for a long time, or simmered over a gentle fire, which will be braised in a pot for a long time after gradually cooked, which will form a suitable temperature conducive to the reproduction of nitrifying bacteria, coupled with sufficient time. Nitrate can be reduced to produce toxic nitrite, and poisoning will occur after feeding. In addition, in the summer with high temperature, especially when it reaches 20: 40 ℃, it is beneficial to the reproduction of nitrifying bacteria, and poisoning is easy to occur at this time. Another reason that is easy to be overlooked is that the gastrointestinal function of the body is dysfunction. eating forage grass and vegetables rich in nitrate can also lead to the proliferation of nitrate reducing bacteria in the gastrointestinal tract and promote the reduction of nitrate to produce nitrite. resulting in nitrite poisoning, also known as enterogenic nitrite poisoning.

2. Clinical manifestations and changes of autopsy

Clinically, the disease can be divided into acute type and chronic type. In the former, methemoglobinopathy occurs mainly after exceeding the standard, and usually occurs in 15min~3h. The main symptom is cyanosis, including skin, mucosa, eyelids, lips, tongue, restlessness, abdominal pain, vomiting, diarrhea and accelerated heart rate. When the symptoms are severe, the body temperature of the diseased cattle is basically normal or slightly decreased, the body ends are cold, the heart rhythm is abnormal, the response is indifferent, convulsions or fall into a coma, and often die due to respiratory failure. The latter diseased cattle will not show obvious clinical symptoms, which is easy to be misdiagnosed, and has an impact on its feed conversion rate and productivity, resulting in greater economic losses.

The autopsy of the dead cow showed that the blood showed soy sauce color and could not be completely coagulated, and soon turned bright red after encountering air, the oral mucosa was grayish red, the tracheal mucosa and gastrointestinal mucosa were bleeding, the myocardium was bleeding, and the liver was swollen. Congestion, emphysema and bleeding occurred in the lungs, and congestion and bleeding also occurred in the kidneys.

Third, diagnostic methods

According to the main clinical symptoms of diseased beef cattle, such as mucosal cyanosis, brown blood, dyspnea, etc., especially the very short and acute course of the disease, as well as the correlation between sudden onset and mass, the type of feed intake and improper feed preparation, we can make a preliminary diagnosis and organize relevant veterinary staff to carry out rescue at the first time. Methylene blue is particularly effective in detoxifying nitrite poisoning. The results of this treatment further verified the accuracy of the preliminary diagnosis.

In order to establish the diagnosis, the denatured hemoglobin test and nitrite simple test were carried out at the disease site of beef cattle. The examination method of denatured hemoglobin is to take a small amount of blood in a small test tube, exposed to air and oscillated, which will turn bright red in a short time and become reduced hemoglobin; if it is still brown after oscillating in the air, that is, denatured hemoglobin. Simple test method for nitrite: take 1 drop of rumen content of beef cattle or liquid juice of residual feed on filter paper, add 1 drop of 10% benzidine solution and 1 drop of 10% acetic acid solution, if there is nitrite, then the filter paper will turn brown, otherwise the color will not change.

IV. Prevention and control measures

1. medication. After nitrate poisoning in beef cattle, make sure they are transferred to a quiet environment and use drugs that raise blood pressure. Methylene blue (methylene blue) is a specific antidote to the disease. Diseased cattle are treated with 20mg/kg according to their body weight, prepared into a solution of 1% concentration, and then injected intravenously. Diseased cattle can also be given 5mg toluidine blue and / IO~100mL25% vitamin C per kilogram of body weight. If the cattle farm has neither methylene blue nor toluidine blue, the diseased cattle can be immediately infused with 2000-3000 mL 0.05% 0.1% potassium permanganate solution, combined with intravenous injection of sodium thiosulfate, large doses of vitamin C and hypertonic glucose. If the sick cow has serious difficulty in breathing, it can be injected intravenously with a mixture of 10% glucose and 3% hydrogen peroxide. When the severe poisoning symptoms of diseased cattle disappear, take appropriate amount of laxatives (such as sunflower oil) or mucosal protective agents (such as wheat bran juice, flaxseed and starch paste).

two。 Strengthen feeding and management. The prevention of the disease is mainly taken, and the fundamental measure is to strengthen feeding management. Establish a perfect feed hygiene system and adopt a simple method to check the amount of nitrite contained in the feed to ensure safety. In daily management, cattle are prohibited from feeding mildew feed; when feeding green feed, the amount of feed should be strictly controlled, and sufficient sugary feed should be supplied, and appropriate amount of iodized salt, vitamin An and vitamin D should be added at the same time; for the remaining green forage after eating, it should be spread out and stored to prevent stacking fermentation. Pastures should strictly use chemical fertilizers to prevent chemical fertilizers from polluting drinking water and feed, and cattle are prohibited from grazing there in the process of fertilization to avoid accidental consumption of chemical fertilizers or contaminated drinking water and feed. Staff should be careful to avoid using nitrate fertilizers, nitrites and medicines as feed salts. For lactating cows and calves, taking an appropriate amount of 1% methylene blue solution before sucking, or adding 30~10mg tetracycline per kilogram of feed, can effectively prevent the disease.

The above are some of the introduction and diagnosis and preventive measures of nitrite poisoning in beef cattle, hoping to provide some reference value for farmers.