How to diagnose and treat selenium deficiency in dairy cows? Farmers need to master these methods

1 Symptoms

The affected animals show depression, decreased appetite, emaciation, curled coat, standing apart from the herd in a daze, unsteady standing, tendency to lie down, movement disorders, muscle tremors, numbness of the limbs, arched lower back, and a sharp drop in milk production. In severe cases, appetite is completely lost, milk production stops, the animal cannot rise, breathing becomes shallow or panting, and finally opisthotonos, convulsions, and death from heart failure occur. The course of disease is about 2 to 3 days.

2 Necropsy changes

Three animals were necropsied. All carcasses were emaciated with curled coats. The muscles were pale reddish-brown, and in severe cases yellowish-white, especially the muscles on the inner side of the upper parts of the forelimbs and hindlimbs, the longissimus dorsi muscle, and the muscles below the hip joint. White streaks or spots were seen on the cut surface. The muscles were dry. The myocardium near the epicardium had grayish-white streaks parallel to the muscle fibers. The liver was slightly swollen with a smooth surface. The spleen was grayish-white with sharp edges. The renal capsule was easily peeled off, and the three layers were clearly demarcated. The lungs were swollen, and foamy fluid flowed out from the trachea and bronchi. The rumen was filled with gas and contained a small amount of thin contents. The intestines were empty, and the intestinal mucosa showed mild congestion.

3 Histopathological examination

Skeletal muscle: Muscle fibers were arranged irregularly, the spaces between muscle fibers were markedly widened and filled with connective tissue, most muscle fibers had lost their transverse and longitudinal striations, muscle fibers were fragmented, and sarcoplasm was dissolved. Most muscle cell nuclei were lightly stained, disintegrated, or had disappeared.

Cardiac muscle: Most myocardial fibers were fragmented, striations had disappeared, sarcoplasm was dissolved, most nuclei were disintegrated or had disappeared, the spaces between muscle fibers were widened, and connective tissue had proliferated.

Liver: Hepatocytes showed degenerative changes, and large numbers of red blood cells were seen in the sinusoidal spaces.

Kidney: Renal tubular epithelial cells showed degenerative changes.

Spleen: The capsule was thickened, trabeculae were increased, and the white pulp was enlarged.

Lung: Congestion and edema.

Small blood vessels: Observation of small blood vessels in the hepatic portal area, the splenic trabecular arteries, and small blood vessels in the heart and lungs all showed edema of the vascular intima, with partial dissolution and disappearance of the sarcoplasm of the smooth muscle in the media.

Based on the clinical and necropsy changes, a preliminary diagnosis of selenium deficiency was made.

4 Treatment

Selenium supplementation measures were taken promptly. A 0.1% sodium selenite vitamin E injection was administered at 10 mL per animal by a single intramuscular injection, treating the whole herd. For severe cases, cardiac stimulants and fluid replacement were given in combination, and another intramuscular injection was given one week later. After taking the above measures, the condition of the sick animals improved, and the prognosis was good.