Determination of age of calf is important for effective sale / purchase and cost decisions. It is quite easy to determine age in calves by examining teeth. At birth, a cow calf will have 20 temporary ‘milk’ or deciduous teeth, and as the animal grows these are replaced by permanent teeth. In order to describe numbers and types of teeth a ‘dentition formula’ is used. In case of newborn calves the dentition formula is:
2(Di 0/4, Dc 0/0, Dp 3/3)
How to read dentition formula? For purpose of dentition the mouth is considered as two halves but the formula describes only one half, and hence it is always multiplied by ‘2’. The numbers in numerator and denominator indicates the number of each type of tooth in the upper and lower jaws. ‘D’ indicates deciduous (milk) teeth and the lowercase ‘i, p, and c’ indicate incisors, premolar, and canine tooth types, respectively. The formula given above can be read as: The calf has total 8 incisors, all in the lower jaw, no canine teeth and total 12 premolars (six in each jaw) each jaw.
How to differentiate between deciduous and permanent teeth:
Deciduous incisors are smaller in size than permanent incisors. The crown of deciduous incisors are also narrower, diverges more from the base (at the gum line) of the tooth to the apex as compared to permanent incisors. There is also a difference in the shape and size of teeth and the jaw width. The first permanent tooth in calves erupts at 12 months, hence from 2 weeks to 12 months it is difficult to age an animal by dentition alone; height and weight being more useful criteria.
Teeth Age of eruption
First incisor Di-1 Birth to 2 weeks
Second incisor Di2 Birth to 2 weeks
Third incisor Di3 Birth to 2nweeks
Fourth incisor Di4 Birth to 2 weeks
First cheek teeth Dp1 Birth – 1 week
Second cheek teeth Dp2 Birth – 1 week
Third cheek teeth Dp3 Birth to 1 week