Effects of cobalt deficiency on the ovarian function in the East African short-horned goat

24 normocyclic East African short-horned goats were made vitamin B12-deficient through feeding cobalt-deficient Rhodes grass (Chloris gayana) hay. The deficiency was confirmed by controls of the blood level, by the occurrence of anaemia, by increased cortisol levels, and by hypertrophy of the fasciculata and reticulata zones in the adrenal cortex. The oestrogen level increased initially, and then decreased markedly from the 3rd cycle on, and reached levels below those of the control. Ovulations finally ceased. It is suggested that ovarian dysfunctions during vitamin B12 deficiency are caused by changes in the endocrine profile.