Monday, 21 September 2015
Parasites needn’t be a sting in the tail
Think those hard winter frosts killed the parasites in your pastures? That there will now be fewer worms in stock? Unfortunately, the short answer is no.
Frosts will kill off some larvae and stop worm eggs developing, but it does not mean that animals are now magically free from the threat of parasitic worms. Understanding what is going on at grass level can help ensure stock health is not compromised by worms as spring approaches.
Suitable climatic conditions can allow infective larvae (L3) to survive for 12 months or longer in the pasture environment. At steady temperatures between 5 and 10°C, infective larvae are inactive and worm egg development is greatly reduced.
The high levels of infective larvae on autumn pastures will gradually decline during winter months, potentially reducing the threat to animal health, but these residual levels can still pose a real risk. A few days of warm weather as spring approaches can result in a rapid build-up of parasites on the pasture again.
Every herd and flock is different and farmers should carefully assess the need to drench stock on their own farms. This assessment is best done by monitoring changes in body weight and condition score, feed levels, evidence of scouring, sheep to cattle ratios, grazing management and faecal egg count scores.
For example, a farmer who does not typically drench ewes pre-lambing may find this year that feed levels and ewe condition scores are both below where they usually are. Worms pose a bigger threat under these conditions, leading to reduced lamb birthweights, milk production and lamb and ewe survival. With careful consideration, drenching ewes pre-lambing this year may well be justified.
Combination drenches are regarded as the best way to treat parasites in stock and slow the development of drench resistance. Ravensdown faecal egg count reduction tests, carried out over a number of years, show that cost-effective double combinations such as Combo™ Low Dose continue to work well eliminating parasite burdens in sheep and cattle.
Combo™ Low Dose drench is used to control roundworms in sheep and cattle, including Ostertagia and strains that are resistant to either the benzimidazole (white drenches) or levamisole (clear drenches), lungworm, tapeworm and adult liver fluke.
Used in the prescribed way, Combo™ Low Dose is generally safer to use in young stock compared to the some of the macrocyclic lactone products, commonly known as MLs (the family of drenches that include Abamectin and Moxidectin), making it an ideal drench to use in young dairy calves weaning in spring.