Thyroid hormones and metabolic rate during induction of Vitamin B12 deficiency in goats

Vitamin B₁₂ deficiency was induced in 15 small East African goats by feeding cobalt deficient ^{Chloris guyana} hay (containing 0.02 mg of Co/kg dry matter) over a 25week experimental period. Cobalt was supplemented as an oral drench to supply 0.3 g of Co/goat/week to 15 treated goats. At intervals of 3–4 weeks, serum concentrations of Vitamin B₁₂ total thyroxine (TT₄), free tetra-iodothyronine (FT₄) and free tri-iodothyronine (FT₃) were determined by radioimmunoassay, while the rate of resting metabolism was determined by measuring the goats' rate of oxygen consumption.

Serum Vitamin B₁₂ concentration was significantly higher (p<0.01) in cobalt-treated (289.6 ± 40.76 pg/ml) than in control (142.8 ± 28.27 pg/ml) goats. The mean serum TT₄ concentration was signifieantly (p<0.01) higher in control (59.0 ± 1.70 nmol/l) than in cobalt-treated (51.6 ± 2.45 nmol/l) goats. However, the levels of FT₄, FT₃ and the rate of resting metabolism were unaffected by the goats' cobalt status. Furthermore, the goats did not lose weight or become anaemic.