If you're a horse owner, you've probably asked yourself this question as cut grass shoots from beneath the mower deck: Why can't I rake up these lawn clippings and give the horses a treat?

Yours is a familiar question, but what's the best answer?

To answer it properly, you must think about your horse's diet and the decisions you make for him daily as well as the decisions of those whom you trust with his health.

If you do this, the answer to your question will quickly become apparent.

Be Careful of Yew Yews are evergreen trees and shrubs characterized by flat, needlelike leaves. In spring and summer, plants produce fleshy pinkish-red berries. More likely than not, one of your neighbors has spiffed up his yard by including these easy-to-grow ornamental shrubs in his landscaping. In a forest, yews grow tall, commonly 20 to 40 feet, but in the controlled setting of a yard or garden, they are often subjected to severe trimming and end up looking more like a hedge than a tree. Yew is considered one of the most poisonous plants in the world due to the many natural toxins found in it, the most potent of which is taxine. Researchers believe that horses need only ingest a small amount (one half to one pound) of yew to succumb to its toxicity. There is no effective treatment for yew poisoning. Therefore, trimmings from yew plants should never be fed to horses, nor should horses have access to shrubs or trees. For those horse owners that festoon their fencelines and barns with evergreen wreaths, be sure horses do not have access to those crafted from yew leaves, both during the holiday season and after disposal. If you're uncertain if a tree or shrub in your barnyard or pasture is a yew, have an expert identify it. If it proves to be a yew, take whatever measures are necessary to remove it from the premises.

For the sake of consistency

One of the tenets of feeding management is consistency - both in feed type and times of feeding. The horse's digestive system adapts to a certain diet and does amazingly well on whatever limited menu he is offered daily, be it primarily pasture and a vitamin/mineral supplement or a full-fledged ration intended for an intensely worked athlete.

Any abrupt change in the diet can upset the delicacy of the digestive tract, throwing the entire system into chaos and possibly causing colic or founder.

"Feeding lawn clippings will dramatically upset the balance of microbes in the hindgut, potentially leading to colic or laminitis," said Larry Lawrence, Ph.D., a nutritionist with Kentucky Equine Research (KER).

"The amount of highly fermentable carbohydrates in regularly clipped lawns is dangerously high.

Excessive intake results in a high rate of fermentation in the hindgut. Accelerated hindgut fermentation can produce increased amounts of volatile fatty acids, which, as their name implies, are quite acidic," continued Lawrence.

"In addition to volatile fatty acids, a surplus of lactic acid will be produced. Lactic acid is not utilized or absorbed well in the hindgut. This increased concentration of acids brings about a condition called acidosis that lowers the pH of the hindgut.

"The acidic environment created by fermentation of grass clippings in the hindgut causes microbes to die, releasing into the bloodstream endotoxins that can cause laminitis," said Lawrence.

Problems too risky to chance

Another aspect often overlooked by well-meaning horse owners is how lawn clippings will affect individual horses with certain quirks or conditions. When a horse grazes, he must go through the motions of selecting, ripping, and thoroughly chewing grass.

When a pile of lawn clippings is placed in front of him, the horse can consume the cut grass much more quickly than if he were grazing naturally. If your horse has a tendency to bolt his feed (eat it very quickly), he may do the same with lawn clippings.

When insufficiently chewed and gulped too quickly, a bolus of clippings can become lodged in his throat, and a condition called choke may ensue. Choke is serious and usually requires the intervention of a veterinarian for resolution.

Lawn clippings might be thoroughly unsuitable for a horse that suffers from a pulmonary disease such as heaves. Dry clippings can be dusty, triggering a reaction that leads to respiratory distress. Reactions may be severe enough to warrant veterinary attention or a break from regular work.

On the opposite end of the spectrum, damp clippings could provide the perfect environment for mould and bacterial growth. Consumption of mouldy grass could cause colic or diarrhoea.

Not always the same - lawn grasses and pasture grasses

A final factor worth consideration is chemical exposure. As horse owners, we implicitly trust grain farmers, hay growers, and pasture specialists to make informed choices about the growing conditions for their products, especially when it comes to fertilizers, pesticides, and other chemicals that might be necessary to ensure bountiful crops.

Manufacturers of lawn-care products are probably not as concerned with the effects of such chemicals on horses.

Fertilisers and weed-control products intended for lawns might not prove detrimental in small quantities (it's not unusual to see owners hand-grazing their horse in their front yard), but to overload the system with large amounts might indeed be harmful.

The potential problems associated with feeding lawn clippings far outweigh the benefits. Certainly there's nothing wrong with offering your four-legged friend a treat, but it's safest to stick to the usual gustatory delights such as carrots and apples.

Without knowing for sure how a horse will react to lawn clippings, it's best to avoid feeding them altogether.

Walter Clayman felt generous that fateful day in late midsummer. Having just finished up mowing an overgrown lawn, he began the laborious chore of raking the long rows of clumped-up grass.

He picked up bushels of cut grass from the yard, and without a suitable disposal place nearby, he threw the grass over the split-rail fence and into the hungry mouths of his two aged quarter horse geldings.

Needless to say, the horses, already downright plump, were in hog-heaven. Walter thought the idea brilliant - efficient cleanup of the yard as well as overjoyed, well-fed horses.

He had grave second thoughts, however, the next morning when his gray gelding, the one he called Blanco, was profoundly lame. The old gelding could barely walk and his front hooves felt significantly warmer than his hind hooves.

Baffled by the sudden onset of what was sure to be diagnosed as laminitis, Walter called his veterinarian. Quick assessment and action by the veterinarian allowed Blanco to recover from this bout of laminitis without detriment to his leisurely days that would lie in his future.

But what brought this on?

Questioning by the veterinarian eventually revealed the culprit: grass clippings. The two geldings, the veterinarian discovered, were familiar with their barren surroundings, namely a drylot that was necessary to keep the two from becoming obese.

Ample mid-quality hay and a well-formulated vitamin and mineral supplement rounded out the diet.

The grass clippings represented a sudden shift in the geldings' diet.

While the other gelding seemed unfazed by the event, Blanco became seriously ill.

Despite similarities in age and breed, the geldings' metabolic makeup kept one safe while the other's life hung in the balance.