Study: Hay Helps Shetland Ponies Adapt to Winter Conditions
Would you leave your Shetland ponies outside all winter? A new scientific study has confirmed what many people have believed for generations—that these hardy ponies do well in outdoor conditions even in the winter. But, they said, they likely benefit from supplemental hay.

Study ponies that didn’t receive supplemental feed during the winter adapted to the food supply available, but blood parameters suggested the beginning of health problems when the available fodder was insufficient, said Lea Brinkmann, PhD, of the University of Göttingen Department of Animal Sciences, in Germany.

In their study, Brinkmann and her fellow researchers followed 10 Shetland pony mares over a full year, from June to June, in Göttingen. During spring, summer, and part of autumn, the ponies lived at pasture. But from November to March, the researchers housed them in paddocks with a shelter. Half the ponies received food equivalent to 100% of their daily nutritional requirements. The other half gradually received less and less food—to mimic the kinds of nutritional changes that would happen in “natural” winter conditions—until they had only 60% of their daily nutritional requirements.

They found that all the ponies gained considerable weight at pasture in spring and summer, reaching higher-than-optimal body condition scores, Brinkmann said. However, the autumn pasture provided fewer nutrients, and the mares began to lose weight and body condition closer to a normal range during that period. Once they entered the paddocks and began the experimental feeding stage, the ponies fed 100% of requirements maintained constant body weight and condition. But those in the 60% group lost 12.8% of their body weight and dropped in body condition score from fat/very fat to moderate/good over the 16-week experimental period.

While that might sound like a good diet program for overweight ponies, it appeared to have a negative effect on their health and welfare, Brinkmann said. “In winter, feed-restricted ponies show the same hair length and locomotor activity as the ponies with adequate food supply, but they had a considerably lower metabolic rate than the fed ponies,” she said. “The body fat is melted in winter, and this results in health impairments.”

For example, the ponies might be at risk of organ damage, Brinkmann said. All the ponies in the restricted group had elevated triglyceride levels, which can cause hyperlipidemia and hyperlipemia. In ponies, those conditions often lead to fat accumulation in tissues such as the liver and kidneys. Their adaption mechanisms were hypometabolism and hypothermia, she said—meaning the body lowered its metabolism and body temperature to save energy—which is unusual for warmblooded (homeothermic) animals. “However, these are exactly the same mechanisms that Przewalski horses use in cold winters with food scarcity,” she added.

The good news is that the ponies fed 100% of their nutritional requirements adapted very well to the colder conditions through strong hair growth and reduced movement to use less energy, Brinkmann said.

“If they are ridden or driven during the winter, though, their energy requirements will increase, and they will need additional food to maintain body condition,” she added.

While “natural” feeding without complements in winter might help overweight ponies get back to a better weight and body condition, it’s not the ideal diet, said Brinkmann. It’s better to prevent the ponies from getting fat in summer and maintain their weight year-round.

The study, “Long-term adaptation capacity of ponies: effect of season and feed restriction on blood and physiological parameters,” was published in Animals.