Legume shows anti-parasitic properties in horses in French study

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A field of sainfoin near Lake Issyk Kul in Kyrgyzstan.
A field of sainfoin near Lake Issyk Kul in Kyrgyzstan. Photo: Fabienkhan, CC BY-SA 4.0, via Wikimedia Commons

A legume called sainfoin appears to have some anti-parasitic action against small strongyles in horses, researchers report, although further studies are required to understand the mechanisms involved.

It is becoming increasingly difficult to control equine strongyles with deworming medications, as resistance is common.

Pauline Grimm and her fellow researchers, in a study reported in the journal Animals, set out to investigate the possible anthelmintic effect of sainfoin (Onobrychis viciifolia) in a group of naturally infected Trotteur Français (French Trotter) geldings.

The study team, with animal and nutrition specialists Lab to Field and Biogéosciences, part of the French National Centre for Scientific Research, said using natural products as dietary supplements might be an alternative to the widespread use of synthetic drugs.

Sainfoin contains high levels of condensed tannins and other polyphenols. It has already been shown to reduce nematode burdens and/or egg shedding in sheep, goats and, more recently, cattle.

In most of these studies, sainfoin was fed as hay, but similar effects have been observed when given as pellets, suggesting that processed sainfoin keeps its anti-parasitic properties.

In horses, to the best of the authors’ knowledge, a single study has assessed the deworming effect of pelleted sainfoin, in a laboratory setting and in animals.

Sainfoin in flower. The creature near the top is a deer tick (Ixodes scapularis).
Sainfoin in flower. The creature near the top is a deer tick (Ixodes scapularis). Photo: Michael Apel, CC BY-SA 2.5 via Wikimedia Commons

Laboratory results showed that sainfoin decreased hatching rates and impaired larval development into the infective stage. However, these results were not confirmed in horses, as the number of eggs excreted in the feces of horses who received a control diet was similar to the number excreted by those who received a sainfoin diet over the course of 18 days.

Similarly, there were no differences between diets in worm counts (based on worms expelled in feces after a deworming treatment), juvenile-to-adult strongyle count ratio, or female strongyle fertility.

Further investigations are therefore required to evaluate sainfoin’s anti-parasitic properties and identify the conditions that could potentially lead to sainfoin-associated health improvement in horses.

The study involved 17 stabled horses, none of whom had received conventional deworming treatment for at least four months. The animals were allocated to three groups, with an effort made to ensure each group was similar in terms of their fecal egg counts.

The control group received a diet composed, on a dry-matter basis, of 83% hay and 17% wheat bran.

In the second group, half the wheat bran was replaced with pelletized sainfoin, while in the third group all the wheat bran was replaced with the pelletized legume.

The horses weighed an average of 526kg, varying by plus or minus 34kg.

The provided daily amount of dehydrated sainfoin pellets corresponded to 1.53 grams of dry matter per kilogram of body weight for the group receiving the lesser amount, or 3.06 grams of dry matter per kilogram of body weight for those receiving maximum supplementation.

Infection dynamics were monitored weekly through fecal egg counts for 12 weeks. After four weeks, all horses were treated with fenbendazole.

Larval motility was assessed from specimens taken from the horses’ feces at the start of the experiment, after weeks four, eight and 12.

The researchers found that the horses that consumed the higher rate – 3 grams of dry matter per kilogram of body bodyweight per day of sainfoin (that’s around 1.7kg of sainfoin per day) – excreted fewer parasites eggs in their feces, suggesting that sainfoin either decreases the number of intestinal adult worms or alters their fertility.

However, the study team did not find any effect of the diet on egg excretion after the treatment with fenbendazole.

Both before and after anthelmintic treatment, larvae from horses consuming sainfoin were less motile than those from the control group. This, they said, could be beneficial in reducing pasture contamination.

The results suggest that sainfoin has an anthelmintic activity in naturally infected horses, although this effect appears to be context-dependent, the study team concluded.

“Further studies are needed to understand the mechanisms that lead to a possible reduction in egg excretion and to provide recommendations for practitioners.”

The authors said the high variation in fecal egg counts seen between individual sainfoin-fed horses in the study suggests that the anti-parasitic activity might be affected by intrinsic characteristics of the host, such as their immune response and/or the diversity or composition of their microbiota.

“During the whole study, sainfoin demonstrated an inhibitory effect on the motility of strongyle infective larvae, which suggests that it might carry the ability to disturb strongyle at different stages of the life cycle.”

The study team comprised Grimm, Noémie Laroche and Samy Julliand, with Lab to Field; and Gabriele Sorci, with the French National Centre for Scientific Research. Laroche is also affiliated with the latter institution.

Grimm, P.; Laroche, N.; Julliand, S.; Sorci, G. Inclusion of Sainfoin in the Diet Might Alter Strongyle Infection in Naturally Infected Horses. Animals 2022, 12, 955. https://doi.org/10.3390/ani12080955

The study, published under a Creative Commons License, can be read here.

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