Effects of selenium and iodine supplementation on the growth rate, mohair production, and thyroid status of Angora goat kids

The effect of supplementation with selenium and/or iodine on growth rate, mohair production and plasma concentrations of thyroid hormones in goats was studied. Male Angora goats, 3-4 months old, were treated with 0 or 1 intraruminal Se pellet, or treated intramuscularly with iodized oil at 0, 200 or 400 mg I in a 2 x 3 factorial design. Concentrations of Se and I in the lucerne diet were 0.02 and 0.09 mg/kg DM, respectively. Supplementary Se increased (P<0.05) liveweight gain by 26% during the final month of the study, but mohair growth was not affected by either treatment. Plasma concentration of total thyroxine was increased (P<0.001) by I treatment but decreased (P<0.001) by Se. Plasma total triiodothyronine was reduced (P<0.001) by I treatment but unaffected by Se. Thus Se supplementation improved liveweight gain but I had no effect on growth. Se and I treatment together altered thyroid hormone concentrations, but Se x I interactions were not significant..