A Good Start Lasts a Lifetime
Parasite control in studs and youngstock is one of the most influential factors in a horse’s early development, yet it remains an area that is frequently overlooked or started far too late.
Improving parasite control within breeding operations would have a greater long term impact on horse health and welfare than almost any other single change within the equine industry.
It is not uncommon for weanlings of seven to nine months of age to be sold with no parasite control history at all. By this stage, a critical window has already been missed. Early life is when parasite burdens can establish themselves and begin to cause lasting damage, even if problems are not immediately obvious
Why parasite control needs improvement
Both research and day to day experience consistently show the same pattern. Young horses are wormy, that is normal, but unmanaged burdens are not. Too many foals arrive from breeders with no past records, no testing, and having had no structured parasite control plan. The result is that owners and vets then spend years trying to manage issues that could have been prevented with earlier, more appropriate intervention.
Why foals and young horses are so vulnerable
Foals are born parasite free, but exposure begins within days of birth. Their immune systems are immature, and they have not yet developed the tolerance that adult horses rely on. Parasites such as ascarids and small redworm take advantage of this vulnerability. When burdens are allowed to build unchecked, damage can begin very early in life.
The consequences of getting it wrong
High parasite burdens in early life can have effects that last for years. Many horses with ongoing parasite issues can trace the problem back to high burdens in their early life. This is particularly evident in rescue horses, where recurrent parasite problems are common throughout life.
Early gut damage can increase long term susceptibility, and every year there are reports of young horses failing to thrive, suffering colic, respiratory damage, and other illnesses. In some cases, infections are fatal and may have been preventable. Getting parasite control wrong at this stage can genuinely prevent a horse from ever reaching its full potential.
What good parasite control looks like on a stud
Effective parasite control starts before the foal is even born. Broodmares should be monitored regularly, grazing should be managed carefully, and fresh pasture used wherever possible.
For foals, proactive treatment during the first six months of life is essential, alongside worm egg counts from four weeks of age. From six months onwards, control should move towards a test based, targeted approach. Testing needs to be more frequent than in adult horses, usually around every eight weeks, because youngstock remain at higher risk until they reach maturity.
Resistance and why it matters on breeding yards
Anthelmintic resistance is a significant challenge on studs. Young horses shed large numbers of eggs, and safely fenced fields often need to be reused, increasing exposure to resistant parasites. Blanket worming without testing accelerates resistance, but doing nothing is just as risky. The solution lies in targeted use of wormers, regular monitoring, and resistance testing when egg counts remain high.
Large strongyle screening should also be included in annual parasite control plans. This parasite may be re emerging, and where it does, the consequences can be severe. Stud environments are exactly the type of setting where it could reappear unnoticed.
Practical challenges and realistic solutions
Managing parasite control in large groups of youngstock is not easy, particularly when horses are out at grass. A practical starting point is to focus on those that are not thriving as expected. If egg counts are high, further investigation is warranted. Resistance testing high shedders is particularly valuable, and even small steps are better than taking no action at all.
Supporting breeders for the long term
Westgate Labs works closely with breeders to develop realistic and effective parasite control programmes. This includes helping to prioritise actions, interpret test results, and adapt protocols as horses grow. The goal is simple, protecting welfare, supporting performance, and preserving the effectiveness of wormers for the future.
Getting parasite control right early truly sets a horse up for life.