Autumn-born lambs — Responses to use of anthelmintics and selenium

Abstract

Extract

Madam:—Out of season (autumn/winter) lambing is expanding in northern areas. These lambs need to grow at moderate rates through the late winter feed trough so they can fully utilise the spring flush to reach heavy weights before summer. Autumn-born lambs are likely to face high parasite roundworm challenge pre- and post-weaning. Strongyle faecal egg counts of autumn and spring-born lambs at weaning averaged 2000 and 400 eggs/g respectively (n=30) under an all-sheep, splitseason lambing policy near Kaikohe. ⁽⁷⁾ Roundworm infestation can also reduce selenium concentration in the liver. ⁽²⁾ Although Se level in pasture tends to be higher in autumn/winter than in spring/summer ^(l) this could be offset by lower pasture availability. Better winter growth rates have been recorded in weaned calves from a combination anthelmintic/selenium drench than from either of these alone. ⁽⁵⁾