Use of selenium in problem cattle herds.

A 150-cow beef herd had problems with diarrhea in all neonatal calves, with 50% mortality. Necropsy revealed changes consistent with colibacillosis. Vaccination of cows in late pregnancy with E coli and BVD vaccines reduced morbidity but did not eliminate the problem. Assays revealed low serum Se levels. Limited supplementation of Se in premix at 90 mg/lb premix, with 17 lb premix/ton feed, resolved the problem. A 70-cow dairy herd had long-term problems with increased numbers of cystic ovaries and retained placentas, and low conception rates. Serum Se levels were low; results of various other diagnostic tests were inconclusive. Dietary supplementation of Se greatly improved reproductive efficiency. Gross and microscopic lesions may not be inconclusive for a diagnosis of Se deficiency. Dietary supplementation of Se is recommended over injection.