Cattle farmers should be aware that worm burdens on pasture aretypically higher in the second half of summer than the first,particularly on farms not using a strategic control program in theearly grazing season.
Pfizer vet William Sherrard claims that worm infestations associated with parasitic gastroenteritis (PGE) in UK cattle are typically a mixture of Ostertagia and Cooperia species.
Often the predominant worm found on pasture is likely to be Cooperia. This species inhabits the animal’s small intestine where it burrows into the wall, which can impair digestion and the absorption of nutrients, cause diarrhoea and lead to reduced weight gain or even weight loss.
In a research trial [Coopand Sykes, 1979], live-weight gain was reduced by 13.5 per cent due to Cooperia infestation, even though there were no clinical signs of disease such as scouring
To avoid loss of performance, Mr Sherrard says potency and duration of action against Cooperia are important factors to consider when worming cattle. Among the pour-on treatments available, the longest licensed protection is provided by the active ingredient doramectin.
When treating cattle for worms, Mr Sherrard claims farmers should ensure that:
- All animals receive an adequate dose (Ideally, weigh some animals or use a weigh band. Under-dosing leads to poor performance and selects for anthelmintic resistance);
- Pour-on wormers should be applied along the length of the animals back;
- Dosing and moving to clean pasture (e.g. silage aftermath) is avoided where possible, as this can speed up selection for anthelmintic resistance. Indeed, farmers using a doramectin-based treatment can return animals to dirty pasture for up to four weeks before moving to clean grazing (i.e. not grazed by cattle in the earlier part of the season) without the need to re-treat on moving.