Formation Of Teeth

Categories: History and Breeds

It is of the utmost importance to be able to judge of the age of a cow.

Few farmers wish to purchase a cow for the dairy after she has passed

her prime, which will ordinarily be at the age of nine or ten years,

varying, of course, according to care, feeding, &c., in the earlier part

of her life.



The common method of forming an estimate of the age of cattle is by an

examination of the horn. At three years ld, as a general rule, the

horns are perfectly smooth; after this, a ring appears near the nob, and

annually afterward a new one is formed, so that, by adding two years to

the first ring, the age is calculated. This is a very uncertain mode of

judging. The rings are distinct only in the cow; and it is well known

that if a heifer goes to bull when she is two years old, or a little

before or after that time, a change takes place in the horn and the

first ring appears; so that a real three-year-old would carry the mark

of a four-year-old.



The rings on the horns of a bull are either not seen until five, or they

cannot be traced at all; while in the ox they do not appear till he is

five years old, and then are often very indistinct. In addition to this,

it is by no means an uncommon practice to file the horns, so as to make

them smooth, and to give the animal the appearance of being much younger

than it really is. This is, therefore, an exceedingly fallacious guide,

and cannot be relied upon by any one with the degree of confidence

desired.



The surest indication of the age in cattle, as in the horse, is given by

the teeth.



The calf, at birth, will usually have two incisor or front teeth--in

some cases just appearing through the gums; in others, fully set,

varying as the cow falls short of, or exceeds, her regular time of

calving. If she overruns several days, the teeth will have set and

attained considerable size, as appears in the cut representing teeth at

birth. During the second week, a tooth will usually be added on each

side, and the mouth will generally appear as in the next cut; and before

the end of the third week, the animal will generally have six incisor

teeth, as denoted in the cut representing teeth at the third week; and

in a week from that time the full number of incisors will have appeared,

as seen in the next cut.



These teeth are temporary, and are often called milk-teeth. Their edge

is very sharp; and as the animal begins to live upon more solid food,

this edge becomes worn, showing the bony part of the tooth beneath, and

indicates with considerable precision the length of time they have been

used. The centre, or oldest teeth show the marks of age first, and often

become somewhat worn before the corner teeth appear. At eight weeks, the

four inner teeth are nearly as sharp as before. They appear worn not so

much on the outer edge or line of the tooth, as inside this line; but,

after this, the edge begins gradually to lose its sharpness, and to

present a more flattened surface; while the next outer teeth wear down

like the four central ones; and at three months this wearing off is very

apparent, till at four months all the incisor teeth appear worn, but the

inner ones the most. Now the teeth begin slowly to diminish in size by

a kind of contraction, as well as wearing down, and the distance apart

becomes more and more apparent.



From the fifth to the eighth month, the inner teeth will usually appear

as in the cut of the teeth at that time; and at ten months, this change

shows more clearly, as represented in the next cut; and the spaces

between them begin to show very plainly, till at a year old they

ordinarily present the appearance of the following cut; and at the age

of fifteen months, that shown in the next, where the corner teeth are

not more than half the original size, and the centre ones still smaller.






The permanent teeth are now rapidly growing, and preparing to take the

place of the milk-teeth, which are gradually absorbed till they

disappear, or are pushed out to give place to the two permanent central

incisors, which at a year and a half will generally present the

appearance indicated in the cut, which shows the internal structure of

the lower jaw at this time, with the cells of the teeth, the two central

ones protruding into the mouth, the next two pushing up, but not quite

grown to the surface, with the third pair just perceptible. These

changes require time; and at two years past the jaw will usually appear

as in the cut, where four of the permanent central incisors are seen.

After this, the other milk-teeth decrease rapidly, but are slow to

disappear; and at three years old, the third pair of permanent teeth are

but formed, as represented in the cut; and at four years the last pair

of incisors will be up, as in the cut of that age; but the outside ones

are not yet fully grown, and the beast can hardly be said to be

full-mouthed till the age of five years. But before this age, or at the

age of four years, the two inner pairs of permanent teeth are beginning

to wear at the edges, as shown in the cut; while at five years old the

whole set becomes somewhat worn down at the top, and on the two centre

ones a darker line appears in the middle, along a line of harder bone,

as appears in the appropriate cut.















Now will come a year or two, and sometimes three, when the teeth do not

so clearly indicate the exact age, and the judgment must be guided by

the extent to which the dark middle lines are worn. This will depend

somewhat upon the exposure and feeding of the animal; but at seven years

these lines extend over all the teeth. At eight years, another change

begins, which cannot be mistaken. A kind of absorption begins with the

two central incisors--slow at first, but perceptible--and these two

teeth become smaller than the rest, while the dark lines are worn into

one in all but the corner teeth, till, at ten years, four of the central

incisors have become smaller in size, with a smaller and fainter mark,

as indicated in the proper cut. At eleven, the six inner teeth are

smaller than the corner ones; and at twelve, all become smaller than

they were, while the dark lines are nearly gone, except in the corner

teeth, and the inner edge is worn to the gum.