The effect of tetrathiomolybdate on growth rate and onset of puberty in ewe-lambs

The effects of intravenous tetrathiomolybdate (TM) treatment on growth rate and onset of puberty in ewe-lambs were investigated in March-born Sulfolk × Mule Lambs. One group ( n = 6, mean weight 13.5 ± 0.9 kg) was treated with 25 mg tetrathiomolybdate intravenously twice weekly for 34 weeks; the second group ( n = 6, mean weight 13.5 ± 0.9 kg) served as controls. TM treatment significantly depressed liveweight gains in the treated group compared with the controls (97.8 ± 2.5 g/day versus 114 ± 4.8g/day respectively, P < 0.001). Puberty was attained at a significantly earlier age in the controls compared with the TM-treated lambs (245 ± 4 days versus 268 ± 7 days respectively, P < 0.02). The weights at onset of puberty were similar for both groups. The LH responses of the lambs to exogenous oestradiol injections were not significantly affected by TM treatment although the LH peak heights were lower in the TM-treated groups than in the controls. Mean LH pulse frequency and amplitude were similar in both groups. Tetrathiomolybdate treatment affected copper metabolism by significantly depressing ( P < 0.005) the amount of plasma copper soluble in 10% trichloracetic acid. The results of this study show that intravenous tetrathiomolybdate reduces growth rate in ewe-lambs and delays the onset of puberty, although with little effect on the pattern of LH secretion.