1. Determining Age of Animals

2. Introduction
The only accurate method of determining the age of an animal is to know its birth date.
In the absence of birth information, use other criteria.
The examination of the animal’s teeth is the most widely employed method to determine age.
Remember Mr. McMillan? What did he talk about?

3. Introduction
The eruption date is the time that a tooth normally breaks the gum line.
It is more reliable than tooth wear for determining age.

4. Introduction Tooth wear is subject to considerable variation.
Aging an animal using only this criterion is often difficult.
That is why many people say that this animal has the teeth of an animal that is ___ years old, rather than saying that the animal is ____ years old.

5. Introduction Domestic animals develop two sets of teeth.
Deciduous teeth
Permanent teeth

6. Introduction
Deciduous teeth, also known as baby teeth, are typically smaller and whiter than permanent teeth.
Because young animals have much smaller jaws, there are always fewer deciduous teeth than there are permanent teeth.

7. Introduction
Age estimates of horses and ruminants are based on the appearance of the lower incisors and canine teeth.
While the eruption dates of cheek teeth (premolars and molars) are more accurate, they are seldom used.
The upper permanent first premolars of horses are either absent or are small rudimentary teeth, called wolf teeth, which erupt at 5 to 6 months of age.

8. Aging Horses
The incisor teeth of horses differ from those of other domestic animals since they continually erupt (to a certain age) to prevent a deficit in length.

9. Diagram of the horse head and teeth

10. Aging Horses
The following presents important dates for aging horses. Keep in mind that these are average ages and that variations occur in many instances.
1 week old
Deciduous central incisors erupt
1 month old
Deciduous intermediate incisors erupt
8 months old
Deciduous corner incisors erupt

11. Aging Horses 2 ½ years 3 ½ years 4 ½ years 4-5 years 6 years 7 years
Permanent central incisors erupt
3 ½ years
Permanent intermediate incisors erupt
4 ½ years
Permanent corner incisors erupt
4-5 years
Permanent canines erupt (males only)
6 years
“cup” gone from central incisors
7 years
“cup” gone from intermediate incisors
8 years
“cup” gone from corner incisors

12. Aging Horses
Beyond eight years, age determination largely becomes a matter of speculation.
To determine the animal’s age, use several features, such as the shape of the occlusal surface or the angle between the upper and lower incisors.
The shapes of the occlusal surfaces begin oval, then change to round, triangular, and biangular, as the animal ages.
The angle between the upper and lower incisors when viewed from the side becomes more acute as the horse ages.

13. Teeth at age 3 ½ and age 20

14. Aging Cattle
To determine age in cattle, the lower incisors must be examined because they do not have upper incisors.
Several key dates aid in the estimation of an animal’s age.

15. Diagram of Cattle Teeth

16. Aging Cattle Less than – 1 year 1 ½ - 2 years 2 – 2 ½ years
First permanent incisors erupt
2 – 2 ½ years
Second permanent incisors erupt

17. Aging Cattle 3 years 3 ½ - 4 years 5 years
Third permanent incisors erupt
3 ½ - 4 years
Last permanent incisors erupt
5 years
All permanent incisors show wear

18. Aging Sheep and Goats
The lower incisors are also used in age estimations of sheep and goats.
Because they develop teeth at about the same age, sheep and goats have similar eruption dates.

19. Aging Sheep and Goats Less than 1 year 1 – 1 ½ years 1 ½ - 2 years
First permanent incisors erupt
1 ½ - 2 years
Second permanent incisors erupt

20. Sheep and Goat Teeth 2 ½ - 3 years 3 – 4 years
Third permanent incisors erupt
3 – 4 years
Last permanent incisors erupt

21. Aging Dogs and Cats
The permanent teeth of dogs and cats have all erupted by the time the animal is approximately six months of age.
While the wear of teeth is somewhat accurate in large breeds of dogs, it is often misleading, and in smaller dog breeds and cats, it is seldom used.
The best way to determine a dog’s or cat’s age is to know its birth date.

22. Canine Teeth

23. Aging Dogs Deciduous Teeth (Puppy Teeth) Permanent Teeth (Adult Teeth)
Incisors: 3 – 4 weeks
Canines: 3 weeks
Premolars: 4 – 12 weeks
Molars: None
Permanent Teeth (Adult Teeth)
Incisors: 3 – 5 months
Canines: 4 – 6 months
Premolars: 4 – 6 months
Molars: 5 – 7 months

24. Aging Cats 2 – 4 weeks 3 – 4 weeks 4 – 6 weeks 8 weeks 3 ½ - 4 months
Deciduous incisors coming in
3 – 4 weeks
Deciduous canines coming in
4 – 6 weeks
Deciduous premolars coming in on lower jaw
8 weeks
All deciduous teeth are in
3 ½ - 4 months
Permanent incisors coming in
4 – 5 months
Permanent canines, premolars, and molars coming in
5 – 7 months
All permanent teeth in

25. Review What is the difference between deciduous and permanent teeth?
Why is tooth wear not a reliable factor when trying to determine age?
What is the only accurate way to determine the age of an animal?