Common Diseases of Farm Animals

by Robert Alexander Craig

The enforcement of preventive or quarantine measures is very important in the control of infectious abortion. This is especially true of breeding herds and dairy cows. Breeders do not recognize the importance of keeping their herds clean or free from disease. It is a well-known fact among stockmen that abortion and other infectious diseases have been frequently introduced into the herd through the purchase of one or more breeding animals. Because of the prevalence of infectious abortion among cows, it is advisable to subject newly purchased breeding animals, or a cow that has been bred outside of the herd, to a short quarantine period before allowing them to mix with the herd. The breeding of cows from neighboring herds to the herd bull is not a safe practice. In communities where there are outbreaks of this disease, animals that abort, or show indications of aborting, should be quarantined for a period of from two to three months. The separation from the herd should be so complete as to eliminate any danger of carrying the disease to the healthy animals on the clothing and farm tools. If this method of control were practised at the very beginning of the outbreaks, the disease could be checked in the large majority of herds.

The foetus and membranes should be destroyed by burning. In case the animal does not pass the fetal membranes, they should be completely removed. In the cow, it is advisable to wait twenty-four hours before doing this. The animal's stall should be thoroughly cleaned and disinfected. It is very advisable to give the entire stable a thorough disinfecting. For this purpose a three or four per cent water solution of liquor cresolis compound may be used. It is advisable to apply it with a spray pump. The floor and feed troughs should be sprinkled daily with the disinfectant. All manure should be removed to a place where the animals can not come in contact with it. It is not advisable to confine the cows to a small yard. The more range they have the easier it is to control the disease.

Individual treatment is very necessary. In infectious abortion the mucous lining of the womb and the passages leading to it become inflamed. This should be treated by irrigating the parts with a warm water solution of a disinfectant that is non-irritating. This treatment should be repeated daily for a period of from two to four weeks. We must be very careful not to irritate the parts. A one-half per cent water solution of liquor cresolis compound may be used.

Animals that abort should not be bred until they have completely recovered. Small animals that have no special value as breeding animals should be marketed. Cows and mares should not be bred for a period of at least three months.

Infected males should not be used for service. The male should receive the necessary attention in the way of irrigating the sheath before and after each service.

PHYSIOLOGY OF PARTURITION.—Parturition or birth, when occurring in the mare, is designated as foaling; in the cow, calving; in the sheep, lambing; and in the sow, farrowing. A normal or natural birth occurs when no complications are present and the mother needs no assistance. When the act is complicated and prolonged, it is termed abnormal birth. The length of time required for different individuals of the same species to give birth to their young varies widely. It may require but a few minutes, or be prolonged for a day or more. The cause of this variation in the length of time required for different animals to bring forth their young, can be better understood if we study the anatomy of the parts and their functions.

Throughout the pregnant period the expulsion of the foetus is being prepared for. As the foetus develops there is a corresponding development of the muscular wall of the womb. The last period of pregnancy is characterized by the relaxation of the muscles and ligaments that form the pelvic walls, and a relaxation and dilation of the maternal passages. In addition, degenerative changes occur in the structures that attach the foetus to the womb, the normal structures being gradually destroyed by a fatty degeneration. This results in a separation between the fetal and maternal placenta. The contents of the womb begin to affect the organ in the same manner as a foreign body, irritating the nerve endings and producing contractions of the muscles. These contractions of the muscles help greatly in breaking down the attachments until finally the labor pains begin in earnest, and the foetus is gradually forced out of the womb, through the dilated os and into the vagina and vulva.

A normal birth is possible, only when the expelling power of the womb is able to overcome the resistance offered by the foetus and its membranes, the pelvic walls and the vagina and vulva.

[Illustration: FIG. 18.—Photograph of model of uterus of cow containing a foetus: foetus; umbilical cord; placenta; horn containing foetus; and opposite horn. Note the difference in the development of the two horns.]

The relative size of the foetus to the inlet of the pelvic cavity and its position are the most important factors for the veterinarian and stockman to consider (Fig. 18). On leaving the womb, the foetus passes into the vagina and vulva. This portion of the maternal passages is situated in the pelvic cavity which continues the abdominal cavity posteriorly. The pelvic walls are formed by bones and ligaments that are covered by heavy muscles. As previously mentioned, the ligaments and muscles relax toward the end of pregnancy in order to prepare the way for the passage of the foetus. Before entering the pelvis it is necessary for the foetus to be forced through the inlet to this cavity. This is the most difficult part of the birth, as the bones that form the framework of the pelvis completely enclose the entrance to it. It is only in the young mother that the pelvic bones give way slightly to the pressure on them by the foetus. It can be readily understood, that when the young is large in proportion to the diameter of the pelvic inlet, it is difficult for it to pass through. This occurs when mothers belonging to a small breed, are impregnated by a sire belonging to a large breed of animals. It may also occur if the mother is fed too fattening a ration and not permitted sufficient exercise.