Age is an important part of livestock trading as many markets have age limits. Counting the number of permanent incisor teeth is the most common method of determining approximate age in live cattle. Note: MSA grading uses bone ossification, which is assessed on the carcase in the meat works. Obviously this method cannot be used on live animals. Cattle, like many animals, start life with baby or milk teeth. From about two years of age these teeth are replaced with permanent teeth.
Permanent teeth erupt in pairs starting with the centre pair. However, care must be used as the type of forages consumed and grazing intensity how closely to the ground the cow must eat will affect the amount of apparent tooth wear.
Cows grazing in sandy or rocky pastures may have exaggerated tooth wear and be younger than dentition indicates. Once cows become older than 10 years, years of age are typically replaced with general terms such as short and solid, broke-mouthed, or smooth-mouthed gummer. The terms are defined as follows. Short and solid means there is significant amount of wear to the cow's incisors but they are all still present and solidly attached to the mandible.
Broken-mouthed indicates a cow is missing one of the incisor teeth. The smooth-mouthed description indicates the cow has lost or completely worn down most if not all of her teeth. Worn teeth may still be present but worn down to the gumline, hence the term gummer. In summary, cow dentition can be used to estimate a cow's age, but more importantly it can be used to determine if she is capable of biting and chewing forage efficiently for another year of life on the ranch. If a cow does not have the dentition to efficiently harvest forage, she will have a difficult time maintaining body condition.
Cows that have missing or extremely worn teeth are candidates to leave the breeding herd and be replaced by younger females. The deciduous teeth are lost as the animal ages and they are replaced by the permanent teeth.
The deciduous incisors Di are much smaller than the permanent incisors. The crown that part of the tooth that is covered with enamel of the deciduous incisors are more narrow than the permanent incisors and they diverge more from the base at the gum line of the tooth to the apex when compared to the permanent incisors.
Figure 1 compares the mandibles lower jaws from a young animal with deciduous incisors black arrow to an older animal with permanent incisors white arrow. The difference in tooth size and shape and jaw width and size can be appreciated. Cattle dentition is generally used as an indicator of age when actual birthdates are not available. Eruption times and wear of the teeth are the major factors used to estimate bovine age. The definition of eruption is the emergence, penetration or piercing of the tooth or teeth through the gingiva the gum line.
An animal at 14 months of age would have a full set of deciduous incisors. All four pairs of teeth are temporary and firmly in place. The teeth are short, broad and usually have a bright, ivory color. There is usually space between the Di1 incisors. Other incisors may touch on the inside corner at the top of the tooth Figure 2.
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