Study: Straw-Hay Mix Helps Ponies Lose Weight Safely
If your pastured ponies turn into butterballs on hay alone in winter, feeding them straw might offer a solution. According to researchers in Scotland, overweight ponies living outdoors in groups can safely lose weight on a 50/50 barley straw-hay ration.

“Our study suggests that straw isn’t dangerous for ponies—at least the ones in our study population—and it can be used to induce weight loss in ponies living in the field year-round while keeping their hunger satisfied,” said Miranda Dosi, DVM (Hons) MRCVS, an equine medical resident at the University of Edinburgh Royal Dick School of Veterinary Studies.

Dosi and her fellow researchers observed 40 mixed-breed ponies over a four-month period (December to March) as they consumed either a normal ration made up entirely of hay or the same ration composed of 50% local U.K. hay and 50% unchopped barley straw. All the ponies in the straw/hay group lost weight (dropping about 5% of their body weight, on average). Eighty percent of the ponies in the hay-only group gained weight—adding an average of about 5% of their body weight.

“Straw is a forage that’s high in fibers while low in proteins and sugars, leading to gradual weight loss,” Dosi said. “It’s not as palatable as hay, but they’ll eat it if they’re hungry.”

In many cases, however, the ponies in the hay/straw group weren’t hungry. “We often found leftover straw, which suggests the ponies felt full,” she said. As for the 100% hay group, the ponies usually cleaned up the full ration, she added.

“In the straw/hay group, we also noted increased feeding times,” Dosi said. “Increased feeding times may help prevent the behavioral changes, such as aggression, which can accompany restrictive diets and are likely indicators of nutritional stress and poor welfare.”

No Colic, No Ranking Issues

Although anecdotal evidence shows that horses and ponies can develop colic from eating straw, Dosi said she saw no signs of intestinal discomfort in her study herds throughout the four months. “But these were all young ponies with good dental health, and they had a mix of hay with straw,” she explained. “It’s not like the stabled horse that finishes his hay overnight and, not having anything else to eat, starts attacking his straw bedding. Those horses might develop colic, but in our trial access to straw and straw quality were more controlled.”

Keeping the hay/straw ponies in groups didn’t seem to affect their access to the limited hay, said Dosi. Higher-ranking ponies didn’t rush to take all the hay from the lower-ranking ones. As such, all the ponies appeared to be able to have 50/50 rations of hay and straw. “We put the hay under the straw, so they had to dig for it, and that might have taken longer,” she said, adding that the ponies were already in established, stable groups with set hierarchies.

Winter Weight Loss for a Healthier Spring

Winter is a good season to try to get equids to lose weight because, thanks to poor grass quality, owners can better control what the animals eat, Dosi explained. They also use more of their body’s energy staying warm, which helps use excess calories stored in fat. And a healthier body condition at the end of the winter gives metabolically challenged ponies a better chance at avoiding laminitis once the rich spring grass becomes available, she said.

None of the 40 study ponies received any additional work or exercise than what they had from their 24/7 pasture turnout, and all were left unblanketed, Dosi said. Owners wishing to help their horses or ponies lose weight, whether on a straw-mix diet or by other weight loss means, should monitor body condition regularly to ensure the animal is coping with the regime. “Don’t just check the girth, but keep an eye on the neck crest, the base of the tail, the rump, and the shoulders as well, as these are good indicators of body condition in ponies,” she said.