We used to regularly feed grass clipping to our horses and cattle (who were on a alfalfa/grass pasture) when we lived in Minnesota and never had any problems. One thing we did do was to do very little fertilizing and not apply any weed control chemicals. Additionally I kept our mower blades somewhat dull and only mowed every 3-4 weeks so the grass pieces were at least 4-5 inches long. If you have very fine clippings I would not recommend feeding them especially to the cattle. Our animals did very well on the clippings even to the point of getting almost too fat.