Improving Digestibility Trials in Horses

In assessing the digestibility of equine diets, titanium has proven to be worth its weight in gold.

“Digestibility measures how well a feed’s nutrients are absorbed by the horse and therefore available for maintenance of the body, as well as other demands like growth, reproduction, and exercise,” explained Kathleen Crandell, Ph.D., a Kentucky Equine Research nutritionist.

“There are options for ways to measure digestibility,” she continued. “Total fecal collections involve isolating an animal for several days (usually between three and seven) while feeding the test diet and collecting all of the feces and urine produced. Samples are then analyzed to calculate the disappearance of the nutrient being investigated.”

“Specialized equipment can be used to reduce the burden of nonstop collection but can be expensive. In addition to being time-consuming and labor intensive, total fecal collections are not practical when trying to measure digestibility of some diets, like pasture,” Crandell described.

To ease the time and labor constraints of fecal collections, markers were developed. Markers are indigestible substances that can be recovered from feces when fed at the same time as the test diet. By calculating a ratio of the amount of an indigestible substance, called a marker, added to the feed and recovered in the feces, an estimation of digestibility can be determined.

While chromium-based markers have been used for this purpose, a search for better dietary markers has been ongoing. Studies showed that titanium oxide can be used as a digestibility marker. To date, titanium-based markers have only been studied in monogastric animals such as dogs and pigs, which share remarkably similar digestion traits to humans. They have not, however, been studied in hindgut-fermenting species like horses.

In a recent trial*, titanium oxide was identified as the preferred marker for digestibility trials in horses.

Specifically, the recovery of titanium in the feces of ponies fed chopped alfalfa hay supplemented with titanium oxide administered once or twice daily was close to 100%. With the high rate of recovery, estimates on digestion will be more accurate.

“Information regarding the absorption of nutrients is also important for economic reasons. Feeds are expensive and if a specific diet has poor digestibility then the nutrients are not being absorbed, the horse does not benefit, and valuable nutrients are being excreted, potentially harming the environment,” Crandell added.

For a better understanding of feed labels, digestibility, and information on diet optimization, consult a Kentucky Equine Research nutrition advisor today!

*Schaafstra, F.J.W.C., D.A. van Doorn, J.T. Schonewille, et al. 2018. Evaluation of titanium dioxide and chromic oxide as digestibility markers in ponies fed alfalfa hay in relation to marker dosing frequency. Animal. 3:1-7.