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

Abstract

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.