Have you ever had a horse refuse to eat a certain feed, treat, or supplement? If so, he might not like the way it smells.

While plenty of studies exist on horses’ flavor preferences, little consideration has been given to horses’ preferences for smell. For example, researchers have shown that anise increases the palatability of equine feed products but have not tested its olfactory impact. So in a recent study, Erin Perry, MS, PhD, associate professor at Southern Illinois University Carbondale, and her fellow researchers looked at the impact of anise as an olfactory stimulant on feed preference and feeding behavior. She presented their findings at the Equine Science Society’s 2021 virtual symposium.

The researchers compared the olfactory effect of anise oil or corn oil (as a control) on study horses’ preference to consume oats. Horses had access to two feeding bunks. Each bunk contained feeding pans with preweighed amounts of crimped oats. The pans were placed atop gauze squares that contained either corn oil or anise oil. These gauze squares emitted odor into the feed bunk.

The researchers tracked how long it took horses to finish (consume at least 75% of the feed in one bunk) the oats. They also monitored preference and interest in the different treatments. The team described preference as a higher number of sniffing episodes or greater consumption. In particular, they looked at which feed bunk horses sniffed and consumed, first action, aversive behaviors, and excessive salivation (saliva coating the outer lips or dripping from the corners of the mouth while chewing). Extreme head extension, retracted lips, gaping mouth, full tongue protrusion, backward rotation of the ears, and feed rejection were examples of aversive behaviors.

The researchers found that the horses in the trial sniffed the anise first and consumed the anise first significantly more frequently than the controls. They also finished the oats with the anise aroma before the corn-oil-scented oats and ate a significantly greater quantity of anise-scented oats. Perry said one observation of interest was that the horses were significantly more likely to sniff the diets upon receiving them rather than consume them immediately without sniffing first.

The researchers concluded that a highly significant relationship exists between olfactory stimuli and feeding preference in horses. While more work is needed to determine thresholds and sensitivities to novel aromas, knowing that aroma can have a significant effect on feed acceptance has implications for feed and supplement manufacturers as well as owners dealing with picky eaters. It might also be of importance to veterinarians when working with horses that have conditions leading to inappetence.

If you’re interested in viewing presentations from the 2021 Equine Science Society Virtual Symposium, you can register for the Symposium until Aug. 2, 2021, and recordings are available for viewing until Sept. 3, 2021.