How to Age Cattle, Sheep and Goats by Their Teeth

The most common way to estimate the age of a cow, a sheep or a goat with no birth record is to look at the incisor teeth of the lower jaw. The method has been in use for a long time, but what it gives is usually a wider range than people assume. Below, the ages at which the permanent incisors erupt, how far those ages shift with breed, sex and nutrition, how to examine the mouth, what wear does and does not say after a full mouth, and how teeth are treated in sacrifice rules and in European Union and United States regulations are set out with peer-reviewed studies and institutional sources.

1. Why Look at the Teeth?

On a recorded farm the source of age is the ear tag and the register. Dental examination is the method for situations where that record is missing or not trusted: an animal bought at market, a heifer that has changed hands, choosing a sacrificial animal, or deciding which animal to cull. The University of Florida cattle guide sums it up in two sentences: differences exist between herds and between individuals, but when the age is not known, examining the teeth is the best method; in any case of doubt the proof of age rests with the person presenting the animal (Pace and Wakeman, 1983). The United States Department of Agriculture Food Safety and Inspection Service (USDA FSIS) uses the same wording: despite individual differences, when the age of an animal is not known, examination of the teeth is the best and most practical method.

The same sources are equally clear about the limits. Dodt and O'Rourke (1988), who examined 94 steers every three weeks in northern Australia, conclude that the large overlap between the eruption ages of successive pairs shows the limitations of dentition as an indicator of age. What can be read from the teeth is not an age but a range.

2. The Mouth of a Ruminant

Cattle, sheep and goats have no incisors in the upper jaw; in their place is a hard dental pad against which the lower incisors work (Pace and Wakeman, 1983; Johnson, 2015). Eight incisors are visible in the lower jaw. The outermost pair is anatomically an incisiform canine: the dental formula of ruminants is I0/3 C0/1 (WikiVet). In the field this pair is counted as the fourth incisor, which causes no practical problem.

The pairs are named from the centre outwards: central (1st pair), middle (2nd pair), lateral (3rd pair) and corner (4th pair). The English field terms — milk mouth, two-tooth, four-tooth, six-tooth, full mouth — describe how many permanent incisors have erupted.

2.1 Deciduous teeth

A calf may be born with or without teeth; by the end of the first month all eight deciduous incisors have appeared (Pace and Wakeman, 1983). In kids the first pair of milk incisors erupts within the first week after birth and the fourth pair at three to four weeks; the milk teeth stay in the mouth for about the first year (Johnson, 2015). Deciduous incisors are much smaller than the permanent ones (Pace and Wakeman, 1983). That difference in size is the basic criterion for recognising a permanent tooth during examination.

3. Eruption Ages of the Permanent Incisors

In the tables below each source's figures are given in that source's own unit and with its own method. The sources disagree with one another in all three species. These differences are not errors; they reflect the breed studied, the nutrition and the method.

3.1 Cattle

The Australian and Boran studies report eruption in days and weeks; the figures in brackets are those values converted to months (one month taken as 30.4 days on average). In the first pair there is a 7-13 month gap between Florida steers (19-20 months) and zebu (27-32 months). In the fourth pair, more than a year and a half separates the lower limit of the Shorthorn 95% range (38.8 months) from the upper limit of the Brahman cross (57.0 months).

3.2 Sheep

The NMSU guide gives single values and adds that the ages for eruption of permanent teeth can vary by 6 months, with the actual timing shifting with breed, nutrition and environmental factors (Pitassi et al., 2022). The guide is not a measurement study; it appears in the table for comparison.

3.3 Goats

For the corner pair in goats the sources differ by up to a year: Merck reports 2½-3 years and Johnson (2015) 3½-4 years. In the ILCA table the goat ranges start at the same age as the sheep ranges or earlier, and end earlier.

3.4 The ranges used by the VetKriter tool

For each pair the dental age tool takes the earliest observation in the sources above as the lower limit and the latest as the upper limit. The lower limit is rounded down and the upper limit up, so that the range leaves no source's observation outside it:

If k pairs have erupted in an animal, its age is at least the earliest eruption age of the kth pair and at most the latest eruption age of the next pair. For a two-tooth bovine, for example, that range is 19-38 months. The width of the range is the real uncertainty of the method. A narrower range would mean disregarding some of the sources.

4. What Shifts the Age at Eruption

4.1 Breed and genotype

On the same pasture and under the same management, Shorthorn steers cut each of the four pairs at a younger age than Brahman × British crossbreds (P<0.01; Dodt and O'Rourke, 1988). The same study calculates that a Brahman cross steer with one pair erupted could be as young as 679 days or as old as 1141 days, which at the growth rate measured means a live weight difference of up to 215 kg. The authors also report that earlier work found Shorthorns to cut their teeth earlier than Herefords and than some zebu crosses.

4.2 Sex

In Boran cattle, females erupted all four pairs significantly later than steers (P<0.01), while no difference was found between bulls and steers (Carles and Lampkin, 1977). Dodt and O'Rourke (1988) also report an earlier Polled Hereford study in which the first two pairs erupted one and three months later in females than in males, and note that data from steers may not apply directly to females. A large part of the cattle measurements in the source tables comes from male animals.

4.3 Nutrition and live weight

In Angora goats whose pre-natal and post-natal nutrition was experimentally controlled, the time to visible eruption and to full development of the first permanent incisor declined by 5.9 and 5.4 days per kilogram of live weight respectively. The lightest animals reached the same stage of development 3 months later than the heaviest (McGregor and Butler, 2011). In the same study, date of birth, birth weight, doe age, growth rate and the level of nutrition in pregnancy or after birth had no detectable effect. In cattle the picture differs: in Shorthorn steers birth weight was negatively correlated with age at eruption, while live weight gain from birth to the start of the study was not correlated (Dodt and O'Rourke, 1988). The Florida guide likewise attributes differences between herds to nutritional background, inheritance and geographical location (Pace and Wakeman, 1983).

4.4 Heritability and individual consistency

In Boran cattle, heritability estimates for age at eruption ranged from 0.11 to 0.91, while environmental variation between and within years accounted for only a small proportion of the total variation (Carles and Lampkin, 1977). Whether an animal is an early or a late erupter is consistent from pair to pair: the correlation between the age at eruption of the first pair and that of subsequent pairs is 0.42-0.65 (Dodt and O'Rourke, 1988). In practice this means that an animal which cuts its first pair early will also look younger than its contemporaries at the following pairs.

5. Irregularity Within One Flock in One Year

Cocquyt et al. (2005) inspected the incisors of 176 sheep from six breeds every two to three months for a year. During that year:

• in 22 sheep no permanent incisor erupted at all;
• in 14 sheep two pairs erupted within the same year;
• in 18 sheep eruption was asymmetric;
• in 5 sheep one incisor was rotated, and in one of those it was combined with dental deviation.

The rule of thumb passed around in the field — "one pair a year" — is therefore an average tendency; it carries no certainty for an individual animal. The same study also yields a practical finding: the gingival redness and swelling accompanying the eruption of a permanent tooth disappeared within two months. If the gum is still red and swollen, the tooth erupted recently.

6. How to Examine the Mouth

1. Restrain the animal safely and wear gloves.
2. Pull the lower lip down to see the lower incisors. Do not look for incisors in the upper jaw; there is a dental pad there.
3. Count from the centre outwards. Large, broad, cream-coloured teeth are permanent; small white teeth are deciduous.
4. Count a pair as erupted as soon as at least one of its teeth has broken through the gum.

The definition in the last step was not chosen at random. Dodt and O'Rourke (1988) counted a pair as erupted when the first tooth had broken through the gum; the FSIS 30-month rule looks at whether "at least one" of the second pair has erupted (cited through the Cornell Small Farms Program); and the European Union regulation speaks of a permanent incisor "erupted through the gum". Since the ranges were measured with that definition, the examination has to use it too.

7. After a Full Mouth: Wear

Once all four pairs have erupted the eruption information is exhausted and only wear remains. Merck notes that, although breed-related, eruption dates are more reliable for the estimation of age than clinical signs of wear. The reason is that macroscopic age-related dental features are scarce or absent in ruminants and that the rate of wear is largely influenced by nutrition (Wright, 2026).

• Cattle: according to the Florida guide all incisors are in wear at 4½ years. Wear becomes distinct on the central pair at 5, the middle pair at 6, the lateral pair at 7 and the corners at 8 years, and the teeth gradually take on a triangular shape. Beyond 8 years it is very difficult to determine age from the teeth (Pace and Wakeman, 1983). That timetable comes from well-fed Florida cattle. In the northern Australian data there are animals whose corner pair had not erupted by 4½ years (Dodt and O'Rourke, 1988).
• Sheep: as the animal ages the loss of incisor length can become a problem that leads to poor performance. On sandy pastures the teeth wear faster and structural loss occurs more readily. The mouth of the 7-year-old ewe in the NMSU guide shows normal wear and spread (Pitassi et al., 2022).
• Goats: it is difficult to age a goat over four years; the amount of wear depends on diet and environment. As they age the teeth spread, look more elongated and sometimes break or fall out (Johnson, 2015).

Wear and tooth loss therefore say more about the state of the animal than about its age. The problem the NMSU guide emphasises is the drop in performance of a ewe whose incisors have shortened or been lost (Pitassi et al., 2022).

8. Teeth in Sacrifice, European Union and United States Rules

8.1 Minimum age for a sacrificial animal

According to the fatwa of the High Board of Religious Affairs (Din İşleri Yüksek Kurulu, 2017), following the lunar year, a camel must have completed 5, cattle and buffalo 2, and sheep and goats 1 year of age. A sheep that has completed 6 months may be sacrificed if it is as well developed as a one-year-old; camels, cattle and goats may not be sacrificed before the stated age even if they are well fattened. The fatwa contains no criterion based on teeth or on the number of teeth.

A lunar year is about 354 days. On that basis 2 years is about 23.3 months and 1 year about 11.6 months. Compared with the dental ranges:

• Cattle: for a four-tooth bovine (second pair erupted) the earliest value in the sources is about 25 months (the lower limit of the Shorthorn 95% range); the whole range lies above the threshold. The range of a two-tooth bovine (19-38 months) crosses the threshold and cannot be separated by teeth.
• Sheep and goats: the range of a two-tooth animal starts at 12 months and lies above the threshold. In a milk-mouth sheep or goat the range crosses the threshold.

This comparison is not a ruling, only the position of the estimated range relative to the threshold. Where the range crosses it, the decision has to rest on the ear tag, the record and the seller's statement.

8.2 European Union

In the European Union regulation on transmissible spongiform encephalopathies (Regulation 999/2001, Annex V), the skull including the brain and eyes, and the spinal cord of sheep and goats count as specified risk material in animals aged over 12 months or which have a permanent incisor erupted through the gum. In the definitions of the regulation, "ovine and caprine animals over 18 months of age" means animals whose age is confirmed by the registers or which have more than two permanent incisors erupted through the gum. In both provisions the teeth stand in for a record of age.

8.3 United States

FSIS considers cattle in which at least one of the second pair of permanent incisors has erupted to be 30 months of age or older, and describes this deliberately as a conservative approach (cited through the Cornell Small Farms Program). The eruption data show why it is conservative: in Shorthorn steers the 95% range for the second pair starts at 25.4 months (Dodt and O'Rourke, 1988).

9. Short Rules the Sources Do Not Support

10. A Data Gap for Local Breeds

No peer-reviewed study measuring the eruption ages of the permanent incisors in Turkish local breeds — Akkaraman, Morkaraman, Awassi, Hair goat, Anatolian Brown, Native Black and others — was found in this review. The common finding of the sources above is that breed and feeding conditions can shift the age at eruption by months. Given that local breeds are mostly kept under range conditions, it is plausible that eruption in these breeds sits closer to the late end of the ranges in the tables. That, however, is an unverified inference; it requires measured data. Keeping birth dates and dental examinations together in recorded flocks is a simple study design that could close this gap.

11. Conclusion

• What the teeth give is not an age but a range. Within the eruption window that range can exceed a year in cattle.
• The width of the range comes from breed, sex and nutrition. Eruption is clearly later in zebu, crossbred and range-kept cattle.
• A pair counts as erupted once at least one of its teeth has broken through the gum. The ranges were measured with that definition.
• After a full mouth, wear is a weak indicator of age but a strong one of condition and performance.
• The source of an exact age is the ear tag and the record. Dental examination is the best aid available when that record is missing.

12. References