Brown Besier, DAFWA, Albany (firstname.lastname@example.org)
The unseasonal rains in many parts of WA in early December have implications for sheep worm control, especially for weaners and hoggets. We saw some major worm problems last year when late rains also occurred, and must be careful that we heed the lessons.
There are 2 major concerns:
Wormier pastures mean a greater need to monitor for worms. Summer drenches should be given as usual to lambs and usually to hoggets, but where the green pasture season is longer than normal, worm egg counts should be taken 5 -6 weeks later to check that a significant number of worms was not picked up after the treatment. This always applies where sheep graze perennial pastures – greater pasture availability means an increased worm risk.
Do hoggets need a summer drench?
For some time we have advised that adult sheep should be drenched in autumn, not summer, but lambs and hoggets (ie, the 2 youngest year-groups) should receive a routine summer drench.
However, in some situations hoggets have very low worm burdens in early summer and a drench can’t be justified. This indicates an early development of their worm immunity, but the chances of this vary with sheep management patterns. If the hoggets (last year’s lambs) were born early in the season, before say mid-June, they may have had sufficient worm contact as lambs, to add to their hogget-year worm experience, to develop a good worm immunity by around 18 months of age.
However, hoggets born later in winter, and now closer to 15 - 16 months of age, are less likely to have their full adult worm immunity, and a summer drench will be needed.
A worm egg count will easily tell whether summer drenches are needed in hoggets. There is usually no value in an egg count in lambs (which almost always need drenching), or adults (which usually don’t), although occasionally there are departures from the normal pattern and a drench can be dropped.