By Mark Andrews

A French study has confirmed that mixed grazing with cattle helps control strongyle worms in horses.

Grazing horses with cattle is often suggested as a useful pasture management tool, to help control strongyle parasites. However, there has been little research to assess the benefit.

With a few exceptions of minor significance, gastrointestinal parasites of horses and cattle are host specific. Thus, infective stages of horse worms ingested by cattle will not develop to adults (and vice versa).

Not only do horses and cattle play host to different species of gastrointestinal parasites, they also have different grazing habits. Horses tend to graze close to the ground and avoid areas that have been previously contaminated with feces – producing “lawns” and “roughs.” Cattle, on the other hand, cannot graze so closely to the ground, but will graze areas avoided by horses. 

The study, by Forteau, Dumont and colleagues looked at the management and worm control on horse breeding farms in two regions of France - some of which employed mixed grazing of horses with cattle. 

Forty-four farms were enrolled in the study. These included saddlehorse production farms in Normandy (generally specialised sport horse enterprises, on productive grassland) and northern Massif Central (leisure horses raised on less productive grassland). Some were specialised horse units; others were mixed cattle and horse farms.

Using surveys and face-to-face interviews, the researchers recorded details such as stocking rate; proportion of pasture used for grazing only or for cutting and grazing; and the extent of integration of anthelmintic (medications for parsitic worm) control and pasture management.

Among the findings were:

• Many farms were still relying on fenbendazole despite the well-recognised problems of anthelmintic resistance. 
• Mixed grazing of horses with cattle was uncommon. Only eight out of twenty-three mixed horse and cattle breeders knew that grazing them on the same pasture could be used as part of their strongyle control strategy.
• In young horses last treated with moxidectin (anthelmintic), those grazed with cattle had 50 percent fewer strongyle eggs excreted in their feces than those grazed in equine-only pastures.

They conclude that mixed grazing of horses with cattle “opens a promising alternative for controlling horse parasitic infection that remains largely unknown by horse breeders.”

For more details, see:

Horses grazing with cattle have reduced strongyle egg count due to the dilution effect and increased reliance on macrocyclic lactones in mixed farms. Forteau L, Dumont B, Sallé G, Bigot G, Fleurance G. Animal. 2019 Nov 4:1-7.

Related: How to Make Rotational Grazing Work for Your Horse Farm

Printed with permission of Mark Andrews, Equine Science Update.

Photo: Canstock/Primoz