Have you ever heard the saying, “never look a gift horse in the mouth?” How about, “he's getting a little long in the tooth?” The aforementioned sayings are a direct result of our ability to estimate the age of a horse simply by looking at his or her teeth. In fact, a good many of our language's common expressions originated due to the rich history between the human and the horse. Short, simple statements concerning horses and the widespread understanding of how the statement related to everyday events and culture of the time have made a lasting impression on the English language.
Your horse's front teeth are called incisors. There are a total of 12 incisors, six on each of the upper and lower jaw. Horses use their incisors for grasping and cutting grass. Like humans, a horse will lose their “baby” or deciduous incisors and erupt permanent incisors in their place. Because incisors erupt, grow and wear predictably in healthy horses, they can be used to estimate a horse's age. However, if a horse has been malnourished, has improper tooth alignment (e.g., parrot mouth), or is a cribber, evaluation of incisor growth and wear will be less accurate in determining his or her age.
Use care when checking your horse's teeth. Gently pull your horse's lip up to look at the front teeth, ensuring that your fingers are clear of your horse's teeth. The following description of how your horse's incisors erupt and wear over time is a general guideline for estimating your horse's age:
The central deciduous incisors are the first to be shed and replace by permanent incisors at about 2 to 3 years of age.
At 3 to 4 years of age, the middle incisors are shed and replaced with permanent incisors.The corner deciduous incisors are lost and replaced with permanent incisors between 4 ? and 5 years of age.
At 6 years of age, the cups of the lower central incisors are worn flat.
At 7 years of age, the cups of the lower central and middle incisors will be worn flat.
At 8 years of age, the cups of all lower incisors will be worn flat.
At 9 years of age, the cups of all lower incisors and the upper central incisors will be worn flat.
At 10 years of age, the cups of all lower incisors and the upper central and middle incisors will be worn flat. Additionally, at 10 years of age, the central enamel ring is oval, the next-to-last incisor on each side is rounded, and Galvayne's groove (vertical groove in the outer surface of the tooth) appears on the outermost upper incisors.Between 10-12 years, the incisors angle of occlusion begins to change. As the horse continues to age, the angle will continue to change and the length of the incisors will increase.
At 15 years of age, the dental stars are round, dark, and distinct; Galvayne's groove is halfway down the outermost upper incisors.
At 20 years of age, the next-to-last incisor on each side is triangular when viewed from the top of the teeth. Galvayne's groove extends the entire length of the lip side of the incisors.
At 25 years of age, Galvayne's groove disappears from the upper half of the tooth.
So remember, “never look a gift horse in the mouth” because it is rude to scrutinize a gift and you wouldn't want to offend the gift-giver. Likewise, one should not refer to another as a “little long in the tooth” because it is not polite to speak of someone's advancing age. Finally, always remember that free advice is worth the price of admission, so if you don't want to believe me, find a way to get it straight from the horse's mouth.