Feeding the starved horse

When Dr. Jennie Ivey was doing graduate work at West Virginia University in 2008, she saw many emaciated horses and became interested in what happens in horses’ bodies during reduced nutrient intake. Today, Ivey, associate professor of animal science at the University Tennessee, helps teach horse owners and rescues about refeeding starved horses.

For those feeding starved horses, it’s critical to have a good relationship with a veterinarian who can assess horses’ health status and teeth and assist with diet formulation. However, not all horses can recover; for some, euthanasia might be more humane.

Ivey described three classifications for starved horses: Classification one is a horse with a body condition score (BCS) of 3 or less and without other health problems. The lower BCS is due to nutrient deprivation. Classification two is the horse that’s had nothing to eat for five or more days. In most cases, refeeding carefully is appropriate to make sure body systems don’t overcompensate and swing in a dangerous direction. Classification three is a horse that’s lost 15% or more of its body weight in the last 60 days, typically without a reason or intentional purpose.

With short-term nutrient deficiency – decreased nutrient intake for less than 72 hours – the horse’s blood glucose drops, which increases the hormone glucagon and decreases insulin.

“The body is making its own sugar to help brain function and other body systems,” said Ivey. “Glycogen, the storage form of glucose, is broken down and moved to tissue that needs sugars. At minimum, the horse’s energy requirements increase for a short time during this acute starvation phase.”

With nutrient deprivation over 72 hours, fat and muscle tissue break down to provide nutrients to the body. The liver begins to make ketones, a byproduct of the body converting fats to sugars.

“There’s slowing of the horse’s energy metabolism in long-term starvation,” explained Ivey. “The system slows down so the body can conserve nutrients.”

There are changes in blood electrolyte concentrations such as sodium, potassium, chloride, magnesium and phosphorus, all of which are important for body functions.

In long-term starvation, BCS and muscle mass are lost, resulting in overall weight loss, and gut integrity becomes compromised. The body can’t fight infection and there’s an increased risk for parasite issues. Nutrient-deprived horses are often lethargic.

BCS is an overall assessment of the horse’s nutrient status through fat deposition. It plays a role in recovering starved horses. When the body mobilizes fat storage and BCS decreases, the chance of recovery drops.

“Horses with a BCS of 1 or 1.5 had a 58% chance of surviving,” said Ivey, referencing a study. “By the time the horse is a 1, other tissue stores such as lean muscle mass are activated to meet survival needs, making recovery difficult. But when the BCS is 2, there’s a 95% chance of survival.”

For BCS, it’s important to look at the entire animal. Check specific areas where fat is deposited: in the neck crest, across the withers, behind the shoulder, across the ribs, at the loin and at the tailhead. Many rescues assess the musculature of the neck, topline or hindquarters, but this results in an inaccurate BCS.

Knowing the horse’s body weight is critical to accurately calculate its daily nutrient requirements. A 600-lb. horse with a BCS of 2, with severe muscle atrophy and eating poor hay, will experience further nutritional deficiency. While a scale is ideal for determining body weight, a weight tape can work. (Weight tape calculations were developed for fleshy horses, so they are more accurate for horses with higher BCS.)

Feed history will likely change the amount and type of feed that can be initially offered. With an unknown feed history, start from scratch. Consider forage type, whether the horse ate it all or left a lot, whether concentrate products were offered, frequency of feeding and whether the horse was on medication or supplements. Ivey emphasized the importance of weighing feed vs. giving a “scoop” or a “flake.”

If a horse is introduced rapidly to a high sugar or starch feed, including forage or concentrate, there’s a rapid rise in glucose and insulin concentrations. The body attempts to quickly move a lot of glucose into the tissue.

“A lot floods into the tissue, which lowers the concentration of potassium, phosphorus, magnesium and vitamin B1 in the bloodstream,” said Ivey. “That changes how the cells across the whole body bring in and move liquid, which changes extracellular fluid. As circulating electrolytes change and fluid moves, there are changes in how heart and lung cells work.

“In addition, there’s also compensation where extracellular fluid isn’t enough and additional fluid is produced, which causes the animal to swell. This rapid shifting can cause the heart to fail and death within three to five days.”

After assessing the horse’s BCS, obtaining a forage analysis and consulting a vet, reintroduce feeds slowly. Use caution with nutrient- dense feeds, provide small, frequent feedings and maintain high fiber. Horses being rehabbed should be housed alone and out of sight to prevent well-meaning people from dumping feed over the fence.

Forage is a critical aspect of refeeding, and Ivey urges horse owners to obtain a forage analysis to ensure quality hay is offered. Although an accurate forage analysis can only be obtained from a forage lab, some visual indicators such as thick stems and seedheads indicate overmature forage. Some low-quality hays may contain weed seeds that cause mouth ulcers. Painful mouth ulcers and poor teeth result in a horse that doesn’t eat.

If a horse can’t chew due to oral issues, even the most perfect forage won’t help. Soaked hay cubes or hay pellets may be an option. Complete feeds are designed to be fed alone without forage and can be used to safely refeed horses or to help stabilize them early in the refeeding process.

“A safe rate of gain is one-half pound to one pound per day,” said Ivey. “That can take a long time with a thin horse. The horse needs to gain about 35 to 45 pounds for every change of 1 in BCS. For most thin horses, it can take 90 to 130 days to regain body condition.”

by Sally Colby