How Good is a Horse's Sense of Smell?

Bronzz reaches for a bite of apple that he likes

How good is a horse’s sense of smell? Excellent! Bronzz can distinguish among different varieties of apples. Every night my husband cuts an apple and shares it among the 3 horses. Bronzz likes red delicious, gala, and fuji apples; he will not touch cortlands or empires. It took us quite a while to figure out why he happily ate apples some evenings, but other times he sniffed the apple chunks carefully, then rejected them, glaring at us as if we were trying to pull a fast one on him. Since my husband made the connection with the variety of apple, we have observed his preferences to be very consistent. However, someone has raised an intriguing question: Could Bronzz be reacting the the scent of pesticides or preservatives on the apples, some varieties perhaps requiring more than others?

This apple did not pass his sniff test

While horses’ sense of smell is not quite as good as dogs, it’s good enough to make them valuable in Search and Rescue. This keen sense of smell means horses get information from all sort of things, including manure. It also means we can never say for sure that a horse spooked at “nothing”. We never know what he might have smelled!

Getting information from poop left by visiting horse

Horses get information from sniffing feces, including the sex, social status, and identity of the horse who produced it. The longest time tends to be spent sniffing the feces of individuals who have been aggressive toward them in the past. Bronzz and I spend most of our trail riding time in the state forest adjacent to our farm, which he probably considers his territory. He likes to stop and sniff nearly every pile of manure along the way, showing more interest than the mares usually do. Stallions mark territory with manure, and keep careful track of other stallions’ markings. It is not unusual for geldings to show such stallion-like behaviors, especially when pastured with mares. Since this information is important to Bronzz, I let him sniff all he wants unless we have guests riding with us, in which case he knows we do not stop.

References:
Equine Sense of Smell by Karen Briggs Dec 11, 2013
https://thehorse.com/13971/equine-sense-of-smell/
The Nose Knows: How Horses Can Help With Search and Rescue by Tik Maynard | Oct 22, 2020
https://thehorse.com/193597/the-nose-knows-how-horses-can-help-with-search-and-rescue/
Olfactory recognition of individual competitors by means of faeces in horse (Equus caballus) by Konstanze Krüger
Animal Cognition March 2011
https://www.researchgate.net/publication/49659137_Olfactory_recognition_of_individual_competitors_by_means_of_faeces_in_horse_Equus_caballus