Grazing cattle with horses helps control strongyles, study finds

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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, gastro-intestinal 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 gastro-intestinal parasites, they also have different grazing habits. Horses tend to graze close to the ground and avoid areas that have been previously contaminated with faeces – 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, published in Animal, the International Journal of Animal Biosciences, 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- reared on less productive grassland). Some were specialised horse units; others were mixed cattle and horse farms.

Using surveys and interviews, the researchers recorded details such as stocking rate; the proportion of pasture used for grazing only or for cutting and grazing; and the extent of integration of anthelmintic 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 8 out of 23 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, those grazed with cattle had 50% fewer strongyle eggs excreted in their faeces than those grazed in equine-only pastures.

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

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. doi:10.1017/S1751731119002738

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