Domestic horses have evolved from creatures that could eat fruit, woody plants and a number of other coarse forages to survive. In doing so, their body structures have changed to suit their environment where humans provide the majority of their diets. And for a horse to perform its best, owners must understand physiology as well as what they’re feeding to these animals.
Dr. Jenna Moline, DVM, associate veterinarian, Hagyard Equine Medical Institute, said in a webinar hosted by Ward Labs Dec. 14 that horses’ teeth evolved through the years, and modern equids have teeth that need routine care.
“What happens is horses have continuous erupting teeth,” she said. “As time goes on, this will lead up to a couple more problems. Which is why things like floating your horse are so important.”
Over time, the teeth keep pushing up and if they’re not worn off, points will form, causing pain in the horse’s mouth. Typically they add a couple millimeters a year.
Domestication of the horse has also changed the way people feed them. Four to five thousand years ago, people started domesticating horses, and Moline said at first they were used for war and beasts of burden. These animals got some supplementation of feed, but not what their modern counterparts do.
“They were getting grass,” Moline said. “But there’s a lot of research and study to show that they were getting supplemented—a lot of corn and barley and things like that.”
Equine nutrition has evolved during the last 150 to 200 years, and Moline said it’s impressive what’s been learned during that time. In her research she found notation of the first equine supplement in 1834. She couldn’t find what it was for, but by 1906 there was the first notations of vitamins being considered in animal diets.
“In 1907, we saw the first introduction of probiotics into human nutrition field,” she said. “By 1929, we have seen our first equine vitamin and mineral supplements.”
As you might imagine, Moline said, with all the advancements learned in one species quickly transferred to the rest.
“In the 1970s, we had gone through all these advances in ruminant nutrition and human nutrition and the 1970s, we saw a huge boom in equine,” she said.
The first extruded product for equines came in the 1970s. By 1989, the first equine “balancer” feed came along.
“Then we saw another big boom in equine nutrition in the 90s,” she said. “You can go into your tack store right now and see the walls of all the different nutrition supplements.”
There’s many options when it comes to nutritional supplements for a specific ailment—hoof, joint, skin, etc. But, it’s important to understand the gastrointestinal physiology behind it in order to know what you’re feeding. Horses rely on their cecum, hindgut and large colon for a lot of their digestion, while ruminants rely on other parts.
“The big difference here is that if a horse has a high fiber product, which hays and straws are definitely high fiber, it’s not until the hind gut that those products start to get degraded and absorbed,” she said. “But what is great about the horse is that they can absorb quite a bit of that and volatile fatty acid from that fiber degradation in their hindgut.”
Moline said about 95% of volatile fatty acid absorption happens in the hindgut, while starches are absorbed in the stomach and small intestine. Any leftover nutrients get a second chance for absorption in the hindgut.
“So horses get two really good chances at digestion,” she said.
There’s still a lot of research regarding digestion in the equine and where it happens and doesn’t. It’s not able to be quantified.
“The other important thing to note is that protein utilization—40% to 70% of our nitrogen, the digestion occurs in the hindgut,” she said. “So overall the horse does a phenomenal job with that hindgut fermentation.”
Moline detailed a 2015 survey titled “A survey of perceptions and practices of horse owners undertaking a massive open online course in equine nutrition.” The group sent out 19,000 surveys globally. It was one of the largest surveys on equine nutrition done to date. Although they only received a 34% response rate, or 6,000 surveys, Moline said it’s relevant to those in charge of feeding decisions.
“We’re able to see some pretty good comparisons from it,” she said. “Interestingly enough out of this, the 6,000 people that did respond, the majority of them were female. And that really is reflective of the horse population.”
Also more than 50% of the respondents had graduate degrees or higher. They also were a group with quite a variable degree of horse experience—from one to 25 years.
Of those who took the survey, Moline found it interesting that 87% of those people fed concentrates or grain supplements to their horses, and 29% of that actually weighed what they were feeding their horses.
“It’s really important that we measure them properly,” she said.
In the survey, 70% of the respondents said their horses had some access to pasture. And for those with limited experience with horses, Moline said the horses were getting what they needed as far as fiber goes.
“Amazingly, all of these horse owners were feeding the appropriate amount of fiber,” she said. “It’s important for horses to have at least that fiber in their diet, which is coming from hays, pastures, grazing that way.”
Eighty percent supplement their horses—and the biggest things supplemented were salt, fats, oils or nutraceuticals. About a quarter of respondents looked to their veterinarian for nutrition advice and the rest relied on the recommendation of trainers or other horsemen for advice.
“What was interesting is that 50% of them said that they trusted their veterinarians for advice, but only 24% were actually going to the veterinarian,” she said. “I’ll be the first to admit as a veterinarian we definitely don’t know everything. And just the same way that you know the farriers they don’t know everything. The dentist doesn’t know everything.”
Moline said it’s a good thing to remember with any of these experts, the more educated you are about what you’re giving your horse, the better.
“It’s going to help you make a better decision about what you’re feeding,” she said.
More nutrition considerations
Another piece of the feeding puzzle is horses need to be weighed. Many horse owners only weigh if it’s a medical necessity—in order to give the proper dose of medicines.
“There’s a lot of reason to be weighing your horse before there’s a problem,” she said. “We should be weighing our horses more often.”
Ideally we would all have a scale, and weigh the horses to get a true pound or kilogram weight, but that’s not always possible. Horse owners can do a couple of different things to get a fairly decent estimate of what the horse’s body condition score and weight are.
“Really we should be doing this every two to four weeks, to monitor all horses health,” she said. “If your horse’s starting to have any problems, if they’re losing weight, we’re on the other side of it.”
If an owner is checking the horse once a month, they’re going to catch any problems quicker if its much longer of an interval than a month.
The most accurate weight measurement is a scale, but if that’s not available, there are a couple other methods. However, the weight tape that estimates weight by using a heart girth measurement is not very accurate.
“That is extremely inaccurate,” Moline said. “What I would encourage you to do is look at how you can take their heart girth, and their body length, and there are online calculators that you put those measurements into that will tell you what your horses estimated weight is.”
Another method Moline suggests is the Henneke Body Condition System.
“This is what, as veterinarians, we look to determine body conditions for horses, and it goes on a scale of one to nine,” she said.
There’s a number of great examples online for the Henneke system, and Moline encourages horse owners to look it up to determine what the horse’s true body condition is.
“Interestingly enough in that survey they found that horse owners and trainers routinely underestimate weight,” she said. “That’s just something we know we’re a little bit biased to underestimating our horses weight, rather than over estimating it.”
Experience doesn’t make someone more accurate either, she said.
“Just because somebody might have 20 years of experience on you, doesn’t necessarily mean that they’re better at estimating your horses weight,” Moline said.
True measurement of feedstuffs is so important when feeding horses. Many people use a “scoop” of feed as a measurement, when that scoop could be an 8- or 16-ounce coffee can or a specific feed scoop.
“But however they say it, what they’re really measuring is a volume and not a weight,” she said. “The same goes with hay. You know we all feed flakes of hay, well your flake of hay might look radically different my flake of hay.”
Each bale of hay is variable in weight and the number of flakes. One person might consider a flake of hay a certain thing, while the other might be the opposite.
“What I would encourage again for everyone is to look at getting a scale so you can actually weigh your feed,” she said.
There are a number of scales available, but Moline suggests finding one that works in your situation and budget.
When it comes to resources for equine nutrition, Moline suggests checking out the National Resource Council’s Nutrition Requirements for Horses.
“That has a lot of information in it, and it’s got some great overviews of all the different fundamental nutrients, as well as what the horses requirements are,” she said. “If you are trying to figure out how much dry matter your horse needs, and based on the amount of work it’s doing; how many calories if you’re worried about the calcium amounts.”
There are charts that help determine needs based on age and workload. Although these charts in NRC give a lot of nutritional values, they are averages in the tables, Moline warned.
“The average of bermuda coastal grass in this book might vary very much from what you find,” she said. “It is really important to be getting your own analysis done of the hay you are feeding as well as doing that anytime that you’re changing the source or the you’re just making sure that you’re staying up with knowing what is in what you are feeding.”
When talking about different nutrient values, be cognizant of water especially during the changing seasons.
“Water is extremely crucial for preventing things like colic, and so you want to make sure your horse always has access to adequate supply of water,” she said.
If you’re concerned about the water, get it tested. Moline said Ward Labs has forage testing and water testing available on its website at www.wardlab.com.