Some horse owners may pooh-pooh environmentally friendly feeding practices, but the risk that “road apples” pose to ground- and surface water is real, said an equine researcher from the University of Florida.
“You know that what you feed in the one end will eventually come out in the back end,” Lori Warren said at the Horse Breeders and Owners Conference earlier this year.
Every day, an average-size horse produces 14 kilograms of manure and eight litres of urine and during the course of a year, that waste will contain 44 kilograms of nitrogen, eight kilograms of phosphorus, and 22 kilograms of potassium. And all of those unutilized nutrients come directly from a horse’s diet, said Warren.
“Horses are inefficient at absorbing everything we give them,” she said. “Any excesses that we feed over what his requirements are will end up in the manure.”
So horse owners need to think about the environment when in the feed store, she said.
“If we know what goes in the horse eventually comes out, we know that we can control what we’re putting in the horse in the form of his diet to control what’s coming out.”
Phosphorus is one of the minerals of “key concern” in water quality, especially in its soluble form.
“It’s also a nutrient that the horse needs in his diet every day,” said Warren.
Almost every type of feed has phosphorus in it, but horses are able to absorb less than one-half of the phosphorus they take in. Finding the right balance depends on the horse and looking at its entire feeding regime.
“It’s not too difficult for most mature horses to be able to easily meet their phosphorus requirements just with forage.”
So horse owners should reconsider the amount of high-phosphorus feed, like wheat bran, they use, as well as any mineral supplements that include phosphorus. Feeding high-calcium legumes can also reduce the amount of soluble phosphorus in the manure.
“It’s a really neat way we can counteract some of the phosphorus if we can’t cut back on what we feed,” she said.
Nitrogen also impacts water quality, and the biggest source of nitrogen in a horse’s diet is protein.
“It’s very common for horses to be fed double or even triple the amount of protein that they require,” said Warren.
“Proteins, like minerals, are not 100 per cent digestible, so some of that’s going to come out in the feces.”
In many cases, overfeeding protein is “unavoidable” because of the feed the horse is given, she said. A sedentary horse, for instance, requires 630 grams of protein, and 10 kilograms of timothy hay — which may be enough to meet a horse’s caloric intake — has roughly 1,000 grams of protein.
“Automatically, just with this hay, I’ve overfed protein.”
Reserving alfalfa hay for horses that have higher protein requirements, including growing or active horses, can reduce protein overfeeding in the average horse.
“We can reduce (nutrient) output by really tailoring the diet and getting closer to what the animal actually needs,” said Warren.
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Match feed to horse
Horses that are sedentary or doing light work need less protein and minerals than active ones.
“(Their requirements) are pretty easy to meet with some of the basic ingredients we typically find in equine diets,” she said. “We don’t have to seek out a lot of fortification or supplementation for those guys.”
Brood mares or growing horses, on the other hand, may require supplementation.
“It makes more sense to focus on providing the correct feed for that specific horse than randomly feeding whatever happens to be on sale that week.”
The same applies to hay, she said.
“Horses with high nutritional requirements should get higher-nutritional-quality hay.”
Ultimately, horse owners and their lands stand to benefit from this type of precision feeding, said Warren.
“In the long run, not only will it help the environment, it will also help your pocketbook.”