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South Australia worms, flies and lice update - May 2016

SA WormBoss Worm Control Programs

SA WormBoss Drench Decision Guides


Adelaide: Colin Trengove, Sheep Health Lecturer (UA Roseworthy campus) (trengovet@icloud.com)

Significant rainfall across South Australia in the second week of May has been very welcome after the preceding dry spell, and substantial dry sowing has occured in anticipation of rain. Unfortunately, strong winds blew a lot of topsoil away before the rain fell, which is always a risk with cultivation and dry sowing, not to mention several 1,000 acres laid bare by the Pinery fire in November. Hopefully, the forecasted end to El Niño and the predicted above average late winter rains will change the fortunes of the area in the lead into spring.

Feed is scarce across most of the state with grain feeding the norm for the past 3 months. Close grazing of short green pick and limited amounts of dry feed will have enhanced worm larvae pick up, but is countered by ewes being in surprisingly good condition despite feed shortages. Worm egg count monitoring has been modest over the past month as lambing and preparation for seeding have been the focus of attention. However, there have been few surprises with significant counts occurring in young rams and pregnant ewes. Both these classes of sheep tend to be more susceptible to worms. Lambs and hoggets generally, plus rams in particular, are vulnerable to worm burdens given their lack of immunity either due to limited parasite exposure or immune incompetence. Similarly, ewes become more susceptible to worms in late pregnancy due to their protein intake being directed to the high demands of the growing foetus(es) rather than the immune system. As a consequence, it is always good policy to monitor ewes in the 4–6 weeks prior to lambing to determine the need for a pre-lambing drench. Any opportunity to minimize stress during lambing and lactation is always the objective.

The next consideration is where (which paddock) the lambs will graze post-weaning and a paddock or paddocks should already be in preparation for this purpose. Given the lack of immune protection in weaners, an effective drench at weaning followed by access to a "worm free" environment is essential to give them the best start in life. Adequate high quality feed is required and should be planned for many months in advance. Feed on offer should be dense exceeding 4cm average pasture height with crude protein 15–25% and 70–80% digestability to promote growth rates of 200–300 g/d following weaning.