The importance of keeping pregnant or lactating mares and their foals up-to-date with their worming regime has been stressed by a worming expert with animal health company Zoetis.
Foals, with their limited immunity, are at increased risk of worm infection, which can at worst be fatal and at best slow growth and compromise good health.
The heavy stocking of mares and foals on pasture can also increase the threat and spread of infection. This meant that foals needed to be treated more frequently and on a different basis than adult horses.
“For mares, it is important to maintain a meticulous worm control programme throughout pregnancy,” said Zoetis’ veterinary manager, Wendy Talbot.
“As for other adult horses, pasture management and selective dosing, based on faecal egg counts through the grazing season, form the basis of therapy.
“In addition to selective therapy, mares should be treated for encysted small redworm in the late autumn or early winter and given a tapeworm dose every six months.
“It is usual to aim for the last worming treatment in the final month of pregnancy using a product effective against parasites of concern to the newborn foal.”
Mares and foals should always be grazed on clean pasture, separate to other groups of horses to minimise the worm challenge. Foals should be first wormed at around eight weeks old, although some foals may need treating earlier in some circumstances.
A minimum recommended protocol is to aim for four treatments in the first year, with some foals needing additional dosing depending on an assessment of the likely parasitic challenge.
The parasites that affect foals can be different than those affecting adult horses. In general, during the first year of life, the parasite threat shifts from the large roundworm (Parascaris equorum) to the small redworm (Cyathostomes) as the foal gets older.
It was essential to talk to your veterinary surgeon or suitably qualified person to correctly identify the threat to individual foals and the best preventative regime, Talbot said.
Traditional advice has been to worm mares and foals at the same time, with the same product and then with the frequency specified by the wormer used (a routine worming regime). However, many experts are now questioning the rationale for this approach and advising that mares continue to be wormed on a selective basis (only dosing when a need is demonstrated) with a wormer which is likely to be most effective against the parasite of concern.
Talbot concluded: “Although regular worming is now frowned upon in most circumstances, as it is known to increase resistance and thus decrease the efficacy of wormers, foals and youngstock are an exception to the rule.
“In order for the foal to thrive while immunity is developing, it’s important to minimise the threat from parasites by striking the correct balance between worming regularly without predisposing to resistance later on.”