Factors Affecting Nutrient Delivery in the Horse

Written by By Kentucky Equine Research Staff

The feedstuffs you offer your horse pass through a long, windy route from mouth to rectum. Along the way, several factors can affect the ability of a horse to absorb nutrients from the diet, not all of which are disease-related.

Processing grains. The phrase “processed food” oftentimes produces a knee-jerk, negative reaction among humans. For horses, though, processing can be advantageous. Many grains and seeds benefit from being processed by increasing the nutritional value for the horse. For example, whole corn can be very difficult to digest. “Enzymes in the digestive system have trouble penetrating the hard, outer shell of a whole corn kernel to access the nutrients inside,” said Catherine Whitehouse, M.S., a nutrition advisor with Kentucky Equine Research (KER). Corn is therefore routinely processed—usually through steam-flaking, cracking, or rolling—to be of greater nutritional value. The sameholds true for barley and whole flax seeds.

Dental health. Horses with poor dentition cannot chew and grind food effectively. Large food particles have less surface area compared to smaller ones, making it harder for digestive enzymes to break down and liberate nutrients. Large, undigested particles pass through the digestive system without being fully broken down, and nutrients are potentially wasted. Proper annual care of teeth by a qualified veterinary professional can help prevent major dental problems and maximize chewing ability.

Mineral imbalance. An unbalanced diet can cause nutrient absorption problems. “Within the digestive tract, different minerals sometimes compete with each other for the same transport molecule for passage out of the digestive tract and into circulation,” said Whitehouse. “Think of many drivers trying to use the same exit ramp to get off of a freeway. Some get through, but others are blocked out.”

A common example of this is calcium and phosphorus, Whitehouse explained. Calcium intake should never be less than phosphorus intake. If excess phosphorus is consumed in the diet from large amounts of wheat bran or unfortified grains, calcium will be blocked from absorption and deficiency may result. For mature horses, calcium and phosphorus ratios range from 1.1:1 to 6:1, with the latter acceptable only as long as sufficient phosphorus is consumed. In growing foals and weanlings, the ratio should only go as high as 3:1. Zinc and copper compete for their own transporter in a similar manner and should be fed in an approximate 4:1 ratio, respectively.

Parasites. All horses carry an internal parasite load, but when parasites are not properly monitored and controlled, the consequences can be severe. Parasite larvae develop into adults inside the horse, stealing nutrients and damaging the intestinal lining in the process. Damaged intestinal tissue may result in a decreased ability to absorb nutrients. Work with a veterinarian to analyze fecal samples for parasite loads, and design a proper parasite control program.

Rate of passage. Vitamins, minerals, protein, and fat are absorbed in the small intestine. The faster feed and forage travels through the small intestine, the less time it has to be digested and absorbed. Large meals tend to flow faster through the stomach and small intestine, compared to smaller, more frequent meals the horse was designed to consume.

Diet content and environment can influence rate of passage. “Forage and high-fat meals move slowly through the stomach and small intestine when compared to high-starch meals,” Whitehouse said. If feed moves too fast, it will not be properly digested and absorbed. Multiple small, balanced, forage-based meals fed throughout the day are ideal.

Horses evolved eating many small, frequent meals. Because modern horses are managed according to human schedules, natural feeding habits are often disturbed. To help manage the ill effects of such dietary changes, a consistent, well-timed schedule of feeding in a comfortable environment is best to ensure maximum opportunity for nutrient absorption. Care of the teeth and management of parasites is also essential for a well-nourished horse.

Article reprinted courtesy of Kentucky Equine Research (KER). Visit equinews.com  for the latest in equine nutrition and management, and subscribe to The Weekly Feed to receive these articles directly (equinews.com/newsletters).