Common Diseases of Farm Animals Part 19

_The treatment_ is directed at the removal of the lameness. Acute inflammation resulting from spavin may be relieved by cold applications and rest. Chronic lameness should be given the same treatment as recommended for bone spavin. The enlargement can be successfully removed in growing colts by the repeated application of mild blisters. It may be necessary to continue the treatment for several months. The removal of the enlargement in adult horses by an operation is recommended. The _greatest caution_ is required in performing this operation.

CAPPED HOCK.--All swellings on the point of the hock are termed "capped hock." The swellings may be due to an injury to the skin and the subcutaneous tissue, or more important structures may be involved, as the subcutaneous bursa, the tendon, or the synovial bursa or sack.

Capped hock is _caused_ by the animal kicking in the stall or in harness, shipping in freight cars and lack of bedding in the stall. Unless the deeper structures are bruised and inflamed the animal shows no lameness.

_The character_ of the enlargement varies. When the injury is superficial, the swelling feels firm, or pits on pressure. Later it may become more firm and feel like a loose, thickened, fibrous cap for the hock. Soft, fluctuating swellings are due to an inflammation of the bursa. Recent injuries feel hot.

_The preventive treatment_ consists in hobbling the hind limbs of a horse that kicks in the stable. This is usually necessary only at night. It may be advisable to pad certain parts of the stall. Horses that are transported in cars should be protected against injuries during transit by the use of proper care and such arrangement of the animals in the car as may expose them to the least injury. Recent injuries should be treated by the application of cold and rest.

After the inflammation has subsided tincture of iodine or blisters may be applied. The treatment of bursal enlargements is surgical. This consists in opening the bursa, destroying the lining membrane of the cavity and treating the part daily until healed. The operation must be performed carefully, as there is danger of infection with irritating organisms. The animal should be given complete rest until the part is healed. Tincture of iodine may be applied to the enlargement that may remain after healing has occurred. This should be continued daily until the skin becomes noticeably irritated. The treatment may be repeated, if necessary, after an interval of two weeks.

[Ill.u.s.tration: FIG. 50.--Curbs.]

CURB.--This term is applied to all swellings on the posterior border of the hock (Fig. 50). Thickenings or enlargements in this region may involve a variety of structures. Thickening of the skin, tendons and sheath may occur. The large ligament that extends from the posterior border of the bone that forms the summit of the hock to the external splint bone, and acts as a stay for the point of the hock, is the structure usually involved in curb.

Faulty conformation is a _predisposing cause_. A narrow base weakens the hock at this point, and the extreme length of the bone that forms its summit gives the powerful muscles attached to it greater leverage than in a well-conformed hock. This results in strain to the ligament at the posterior portion of the region.

_The exciting causes_ are strains resulting from jumping, slipping, rearing, heavy pulling and bruising of the part.

_In examining the hock_ for curb it is necessary to stand to the side and note the profile of the posterior border. Excessive development of the head of the external splint bone should not be mistaken for curb. As viewed from the side, the posterior border of the hock should appear straight.

The curb appears as a swelling on this straight line. It varies in size. A recent curb is usually hot and firm, or may feel soft if enlargement is formed by fluid, hard if formed by bone. Lameness seldom occurs, but if present, resembles spavin lameness.

_The preventive treatment_ consists in selecting for breeding, animals that have strong, straight hocks, and using the necessary care in handling and working horses. It is not uncommon for young horses at the time they are broken to harness to develop a curb. This may be prevented to a large degree by careful handling. At the beginning of the inflammation the application of cold and hand rubbing is indicated. After the inflammation has subsided tincture of iodine or blisters should be applied. Rest is a necessary part of the treatment early in the inflammation. If the lameness does not respond to the above treatment, it should be treated the same as for bone spavin.

QUESTIONS

1. Describe the different fractures of the ileum and give treatment.

2. Describe string-halt lameness and give treatment.

3. What is bone spavin? Describe spavin lameness.

4. Give the causes and treatment of bog spavin.

5. Give the causes and treatment of capped hock.

6. Give the causes and treatment of curb.

PART III.--THE TEETH

CHAPTER XIX

DETERMINING THE AGE OF ANIMALS

[Ill.u.s.tration: FIG. 51.--Head of young horse with bone cut away, and showing position and size of teeth.]

GENERAL DISCUSSION.--The teeth are the pa.s.sive organs of digestion. They are hard organs, implanted in the superior and inferior jaws in the form of a long and narrow arch that is open posteriorly. The free portions of the teeth project into the mouth, and present sharp or roughened table surfaces for the crushing and tearing of food. In solipeds and ruminants the arch is interrupted on each side by the inter-dental s.p.a.ce or bars (Fig. 51). The teeth that form the middle and anterior portion of the arch are termed incisors (Fig. 52). Posterior to the incisors are the canines or tusks, and forming the arms of the arch are the molar teeth. Animals have two sets of teeth, temporary and permanent. The following table gives the number of the different kinds of temporary and permanent teeth.

Temporary Teeth Permanent Teeth Incisors Canines Molars Incisors Canines Molars

Solipeds 12 12 12 4 24 Ox 8 12 8 0 24 Sheep 8 12 8 0 24 Hog 12 12 12 4 24

The tusks or canine teeth are not always present in the female. Ruminants do not have upper incisor teeth. The temporary teeth are erupted either before or within a few days to a few months after birth. The eruption of the permanent teeth and the replacement of the temporary teeth occur at different periods up to the age of four and one-half years (Fig. 53). It is well to keep the following table of dent.i.tion in mind when examining the mouths of animals for the purpose of determining their age.[1]

Horses Cattle Hogs Teeth Temporary Permanent Temporary Permanent Temporary Permanent

Incisors: yrs. mos. yrs. mos. mos.

Centrals At birth 2 6 At birth 1 8 At birth, 12 or 3-4 weeks First 4-6 wks. 3 6 At birth 2 9 8-12 wks. 18 laterals Second 5-12 days 3 6 laterals Corners 6-9 mos. 4 6 12-18 days 4 6 At birth 9 Molars: First At birth 2 6 At birth 2 6 7 weeks 5 Second At birth 2 6 At birth 1 6 8-28 days 14 Third At birth 3 6 At birth 3 8-28 days 13 Fourth 10-12 1 6 13 Fifth 2 2 5 Sixth 4-5 2 6 9 Seventh 18 Canines or 4-5 9 tusks

IN DETERMINING THE AGE of the different domestic animals by the development and appearance of the teeth, most of the attention is given to the lower incisor teeth. Up to the fifth year, the age of the horse or ox can be easily determined by the eruption and replacement of the incisors.

At _one year_ of age the colt has a fully developed set of temporary incisors. The ruminant's incisors at this age all show wear.

_The two-year-old colt_ shows a well-worn set of incisor teeth, and the ruminant at this age has replaced the nippers or centrals.

_The third_, _fourth_ and _fifth years_ are indicated by the replacement of the temporary nippers, dividers and corners in the horse, and the first and second dividers and corner teeth in ruminants.

[Ill.u.s.tration: FIG. 52.--Longitudinal section of incisor tooth: cup; cement; enamel; ivory; and pulp cavity.]

In the horse the permanent nippers are full grown and in wear at _three years_ of age; the permanent dividers are full grown and in wear at _four years_ of age; and the permanent corners are full grown and in wear at _five years_ of age. The table surfaces of the incisor teeth of a five-year-old horse show different degrees of wear. At this period in the animal's age, the nippers have been in wear two years, the dividers one year, and the corners are beginning to show wear. In ruminants, all of the chisel-shaped table surfaces of the incisors show considerable wear when the animal is five years old.

After the animal has a full set of permanent teeth, we judge the age by the degree of wear or the appearance of the table surfaces of the incisors, their shape, the angle with which they meet and the general appearance of the head.

[Ill.u.s.tration: FIG. 53.--Cross-section of head of young horse showing replacement of molar tooth.]

There are several different factors that may cause the wear on the teeth, and the appearance of their table surfaces to vary in the different individuals. The two factors that are of the most importance are the quality of the teeth and the character of feed. Soft teeth wear more quickly than hard teeth, and the teeth of horses that feed over closely cropped and sandy pastures wear rapidly because of the dirt and grit present on the short gra.s.s. This variation in the wear is of little importance to the person who must judge the age of a horse that he expects to purchase by the condition of the teeth. In reality, a horse is just as old as the wear on the teeth and his general appearance indicate. In order to stand severe work the animal must be able to masticate the feed, and prepare it for digestion in the stomach and intestines. The degree of wear on the molar teeth may be indicated by the wear on the incisors. The general condition of the horse and his ability to stand hard work depend very largely on the condition of the table surfaces of the molars.

It is very difficult to judge the age of horses that have deformed mouths or that are in the habit of crib-biting, because of the irregularity in the wear of the incisors.

When examining the teeth for the purpose of determining the horse's age, the shape of the incisors, the angle with which they meet and the appearance of their table surfaces should be observed. The teeth of young horses show more or less yellowish cement. At about seven years of age the anterior faces of the teeth are usually white, later a yellowish color. The teeth of middle-aged horses may be long, and in aged animals, narrow and short. The incisors meet at a more acute angle in old than young horses.

_The free portion of the incisor_ tooth is flattened from before to behind.

At the level of the gums its two diameters are about the same, but the portion of the tooth imbedded in the jaw bone is flattened from side to side. As the tooth becomes worn off, the length of the free portion is maintained by a pushing out of the tooth, and a corresponding shortening of the portion that is fixed or imbedded in the jaw.

_The table surface of the unworn incisor_ tooth is covered with enamel, and in the middle portion the enamel forms a deep cup. After the tooth has become worn the margin of the table portion is then limited by a ring of enamel. This is termed the encircling enamel ring. The central portion of the table shows a second ring, the central enamel ring, that limits the cup margin (Fig. 54).

[Ill.u.s.tration: FIG. 54.--Transverse section of incisor tooth: peripheral cement; peripheral enamel; ivory; central enamel; and central cement.]

_As the table surface_ represents a cross section of the tooth, its appearance and shape will then depend on the portion of the tooth that it represents. From year to year, there is a gradual shortening in the lateral diameter, and an apparent increase in the diameter from before to behind.

These changes in shape are from a long, narrow table surface to an oval, from oval to circular and from circular to triangular (Fig. 55). As the original free portion of the tooth wears off, the cup becomes shallow and smaller until the remnant is represented by a mere dot of enamel that finally disappears from the posterior portion of the table. After the cup has moved from the central portion of the crown and occupies a more posterior position, the dental star, which represents a cross section of the pulp cavity, puts in its appearance. It first takes the form of a brown or dark streak, and later a circular dark spot which gradually increases in size with the wear on the tooth and the age of the animal.