Abstract

On two sheep farms with different winter feeding systems, namely pasture only (farm A) or pasture then swedes or swedes/turnips/kale for 6 to 8 weeks prelambing (farm B), 700 ewes/farm were randomly assigned to 2 groups of 350 animals to assess animal performance. About 5 weeks premating, one group was injected with 390 mg iodine (as Flexidine iodised oil) intramuscularly. Iodine supplementation increased and maintained serum and milk I concentrations for at least 210 days (µg/L; farm A, serum 43 v 65; milk 72 v 197. Farm B, serum 29 v 45; milk 26 v 132), but did not affect potential lambing percentage at scanning, perinatal mortality, or lambing percent (farm A, 140 v 150%; farm B, 138 v 130%). On farm A no goitre was observed among the 77 lambs postmortemed, regardless of I treatment of the ewes. On farm B goitre was observed in 85% of the 34 lambs postmortemed from untreated ewes, but not among the 36 lambs from treated ewes. In the following year, the trial was repeated with 50 ewes/group to monitor changes in I status, and the treatment significantly increased serum I over time but had no consistent effect on serum T4 and T3 concentrations. Supplementing ewes premating with long-acting injectable I prevented goitre in newborn lambs from ewes fed swedes or swedes/turnips/kale as a winter supplement.

ND, Grace, SO Knowles, and GR Sinclair

Proceedings of the New Zealand Society of Animal Production, Volume 61, Christchurch, 164-167, 2001