Injuries, acute indigestion, mouldy, spoiled feeds, chilling resulting from exposure and drinking ice-cold water, nervousness brought on by fright, or excitement and general diseases are the common causes of abortion.
_Infectious abortion_ is most common in cows. Other domestic animals that may be affected are the mare, sow and ewe.
_It is caused_ by a specific germ. The _Bacillus abortus_ of Bang is the cause of abortion in cows, but the specific germ that produces abortion in other species of animals has not been proven. In this country, Keer, Good, Giltner and others have proven that the Bang bacillus of abortion is infectious for other species of animals, and outbreaks of this disease have been said to occur among breeding ewes pastured and fed on infected premises. Its infectiousness for the females of other species has never been proven in natural outbreaks.
The disease-producing germs are present in the body of the foetus, the fetal membranes, the discharge from the maternal passages, the faeces and milk of aborting animals. The male may carry the infection in the sheath, urethra and on the penis. The natural avenues of infection are the maternal passages and digestive tract.
It is very seldom that abortion is carried from one herd to another by means other than through the breeding of animals free from abortion to animals affected by this disease. The purchase of a bull or cow from an infected herd and breeding them to animals that are free from disease, is a common method of spreading the disease. After serving the diseased animal, the male may carry the bacillus of abortion into the maternal passages of the next cow he serves. There are numerous cases on record where the bull was a permanent carrier of the Bacillus abortus and infected nearly every animal served. The distribution of the disease in the herd following the introduction of a cow, sow, or ewe that has aborted before or after being purchased, takes place through contact of the other animals with the virus that may be present on the floor, or in the manure, or by taking the virus into the digestive tract along with the feed and drinking water.
Experimental evidence indicates the latter avenue of infection.
The stallion is the most common source of infectious abortion in mares. An infected stallion may distribute the disease to a large percentage of the mares that he serves. For this reason nearly all of the mares in a certain locality may abort.
In case the infection occurs at the time of service, the abortion usually takes place during the first half of the period of pregnancy. Cows that become pregnant without recovering from the inflammation of the lining membrane of the genital tract, may abort at a very early period. McFadyean and Stockman from the artificially inoculated cases of infectious abortion in cows, showed that the period of incubation averaged 126 days.
_The symptoms of accidental abortion_ are extremely variable. Animals that abort during the early periods of pregnancy may show so little disturbance, that the animal can be treated as if nothing had happened. During the latter half of pregnancy, and especially when the accident is caused by an injury, the symptoms are more serious. Loss of appetite, dulness, restlessness, abdominal pain and haemorrhage are the symptoms commonly noted. If the foetus is dead, it may be necessary to assist the animal in expelling it. In the latter case, death of the mother may occur.
A slight falling of the flanks, swelling of the lips of the vulva and a retention of the fetal membranes, or discharge from the vulva may be the only symptoms noted at the time abortion occurs.
_The symptoms of infectious abortion_ vary in the different periods of pregnancy. At an early period, the foetus may be passed with so little evidence of labor that the animal pays little attention to it. The recurrence of heat may be the first intimation of the abortion. All cases of abortion are followed by more or less discharge from the vulva. This is especially true if the fetal membranes are retained. In such cases, the discharge has a very disagreeable odor. In most cases the foetus is dead.
When born alive, it is weak and puny, and usually dies or is destroyed within a few days. When the attendant fails to give the animal the necessary attention, or is careless in his manipulation of the parts, inflammation of the womb, caused by the decomposition of the retained membranes, or the introduction of irritating germs on the ropes, instruments and hands, may occur. Death commonly follows this complication.
It is very important that the infectious form be diagnosed early in the outbreak. For all practical purposes we are justified in diagnosing infectious abortion, if several animals in the herd abort, especially if it follows the introduction of new animals. Methods of serum diagnosis, the agglutination and complement-fixation tests, are now used in the diagnosis of this disease.
_The preventive treatment_ of the accidental form consists in avoiding conditions that may result in this accident. Pregnant animals should not be exposed to injuries from other animals or from the surroundings. Animals which show a predisposition to abort should not be bred. We should see that all animals receive the necessary exercise and a proper ration.
If the animal indicates by her actions that abortion may take place, we should give her comfortable, quiet quarters. It is very necessary to keep her quiet, and if restless, morphine may be given. A very light diet should be fed and constipation prevented by administering a laxative. The necessary attention should be given in case abortion occurs.
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.
The part of the foetus that presents itself for entrance into the pelvic cavity and its position are of the greatest importance in giving birth to the young. Either end of the foetus, or its middle portion may be presented for entrance. The _anterior_ and _posterior presentations_ may be modified by the position that the foetus assumes. It may be in a position that places the back or vertebrae opposite the upper portion of the inlet, or the floor or sides of the pelvic cavity. These positions may be modified by the position of one or both limbs, or the head and neck being directed forwards instead of backwards. In the _transverse presentations_, the back, or the feet and abdomen of the foetus may present themselves for entrance to the pelvic cavity. These presentations may show three positions each.
The head may be opposite the upper walls of the inlet, the foetus assuming a dog-sitting position, or it may lie on either side.
In order to overcome the friction between the foetus and the wall of the maternal passages, these parts are lubricated by the fluids that escape from the "water bags." If birth is prolonged and the passages become dry, birth is retarded. The hair offers some resistance in a posterior presentation. Young mares that become hysterical have abnormal labor pains that seem to hold the foetus in the womb instead of expelling it.
CARE OF THE MOTHER AND YOUNG.--Although birth is generally easy in the different domestic animals, it may be difficult and complicated, and it is of the greatest economic importance that special attention be given the mother at this time. It is very necessary for her to be free if confined in a stall. If running in a pasture or lot, the necessary shelter from storms, cold or extreme heat should be provided. Other farm animals, such as hogs, horses and cattle, should not be allowed to run in the same lot or pasture.
When parturition commences, the mother should be kept under close observation. If the labor is difficult and prolonged, we may then examine the parts and determine the cause of the abnormal birth. Unnecessary meddling is not advisable. Before attempting this examination, the hands should be cleaned and disinfected, and the finger nails shortened if necessary. The different conditions to be determined are the nature of the labor pains, the condition of the maternal passages, and the position and presentation of the foetus. In the smaller animals this examination may be difficult. In prolonged labor the parts may be found dry and the labor pains violent and irregular, or weak. The foetus may be jammed tightly into the pelvic inlet, it may be well forward in the womb, the head and fore or hind limbs may be directed backwards, or one or more of these parts may be directed forward in such a position as to prevent the entrance of the foetus into the pelvic inlet. Sometimes the foetus is in a transverse position. The parts that present themselves at the pelvic inlet should be carefully examined and their position determined. The necessary assistance should then be given. Any delay in assisting in the birth may result in the death of the young or mother, or both. On the other hand, unintelligent meddling may aggravate the case and render treatment difficult or impossible. There is no line of veterinary work that requires the attention of a skilled veterinarian more than assisting an irregular or abnormal birth.
The attendant must guard against infecting the parts with irritating germs, or irritating and injuring them in any way. The hands, instruments, and cords must be freed from germs by washing with a disinfectant, or sterilization with heat. The quarters must be clean in order to prevent contamination of the instruments and clothing of the attendant by filth.
Extreme force is injurious. For illustration, we may take a case of difficult birth caused by an unusually large foetus. Both presentation and position are normal, the forefeet and head having entered the pelvic cavity, but the shoulders and chest are jammed tightly in the inlet, and the progress of the foetus along the maternal passages is retarded. By using sufficient force, we may succeed in delivering the young, but by pulling on one limb until the shoulder has entered the pelvis, and repeating this with the opposite limb we are able to deliver the young without exposing the mother to injury. It may be necessary to change an abnormal presentation, or position, to a normal presentation, or as nearly normal as possible. This should be done before any attempt is made to remove the foetus.
Following birth the mother should not be unnecessarily disturbed. The quarters should be clean, well bedded and ventilated, but free from draughts. If the parturition has been normal, a small quantity of easily digested feed may be fed. If weak and feverish, feed should be withheld for at least twelve hours. The mare should be rested for a few weeks. The young needs no special attention if it is strong and vigorous, but if weak, it may be necessary to support it while nursing, or milk the mother and feed it by hand. If the mother is nervous and irritable, it may be necessary to remove the young temporarily to a place where she can hear and see it, until a time when she can be induced to care for it. The principal attention required for young pigs is protection against being crushed by the mother. The cutting off and ligation of the umbilical cord at a point a few inches from the abdomen, and applying tincture of iodine or any reliable disinfectant is very advisable in the colt and calf.
RETENTION OF THE FETAL MEMBRANES.--The foetus is enveloped by several layers of membranes. The _external envelope, the chorion_, is exactly adapted to the uterus. The _innermost envelope, the amnion_, encloses the foetus. Covering the external face of the amnion and lining the inner face of the chorion is a double membrane, _the allantois_. The envelopes mentioned are not the only protection that the foetus has against injury.
It is enveloped in fluids as well. Immediately surrounding it is the _liquor amnii_, and within allantois is the _allantoic fluid._
[Illustration: FIG. 19.--Placenta of cow.]
_The placenta_ is a highly vascular structure spread out or scattered over the surface of the chorion and the mucous membrane of the uterus, that attaches the foetus and its envelopes to the womb (Fig. 19). It is by means of this vascular apparatus that the foetus is furnished with nourishment.
The fetal and maternal placentas are made up of vascular villi and depressions that are separated only by the thin walls of capillaries, and a layer of epithelial cells. This permits a change of material between the fetal and maternal circulation. The arrangement of the placenta differs in the different species. In the mare and sow, the villi are diffused. In ruminants, the villi are grouped at certain points. These vascular masses are termed cotyledons. The maternal cotyledons or "buttons" form appendages or thickened points that become greatly enlarged in the pregnant animal.
Toward the end of the pregnant period, the attachments between the fetal and maternal placentulae undergo a fatty degeneration and finally separate.
This results in contractions of the muscular wall of the uterus, and the expulsion of the foetus and its envelopes. In the mare, it is not uncommon for the colt to be born with the covering intact. This does not occur in the cow. Usually the envelopes are not expelled until a short time after birth in all animals, and it is not uncommon for them to be retained. This complication is most commonly met with in the cow.
In the mare the _retention of the fetal envelopes_ or "afterbirth" is commonly due to the muscles of the womb not contracting properly following birth. Abortion, especially the infectious form, is commonly complicated by a retention of the fetal membranes. Any condition that may produce an inflammation of the lining membrane of the womb may result in retention of the "after-birth." Injuries to the uterus resulting from the animal slipping, fighting and becoming crowded are, no doubt, common causes of failure to "clean" in cows.
_The symptoms_ are so marked that a mistaken diagnosis is seldom made. A portion of the membranes is usually seen hanging from the vulva, and the tail and hind parts may be more or less soiled. The latter symptom is especially prominent if the membranes have been retained for several days, and decomposition has begun. In such case, the discharge from the vulva is dark in color, contains small pieces of the decomposed membrane and has a very disagreeable odor. In the mare, acute inflammation of the womb may result if the removal of the "after-birth" is neglected. Loss of appetite, abnormal body temperature, weakness and diarrhoea may follow. Such cases usually terminate in death. Retention of the fetal membranes is a very common cause of leucorrhoea.
_The treatment_ consists in removing the fetal envelopes before there is any opportunity for them to undergo decomposition. In the mare, this should be practised within a few hours after birth has occurred, and in other animals, from one to forty-eight hours. In warm stables and during the warm weather, treatment should not be postponed later than twenty-four hours.
The only successful method of treatment is to introduce the hand and arm into the uterus, and break down the attachments with the fingers. In the larger animals, the use of the arm must not be interfered with by clothing.
Every possible precaution should be taken to prevent infection of the genital organs with irritating germs. It is advisable in most cases to flush out the womb with a one per cent water solution of liquor cresolis compound after the removal of the fetal envelopes.
LEUCORRHOEA.--This is a chronic inflammation of the mucous membrane lining the genital tract, that is associated with more or less of a discharge from the vulva. It is common in animals that abort, or retain the "after-birth."
The discharge may be white, sticky, albuminous, and without odor, or it may be chocolate colored and foul smelling. The tail and hind parts are usually soiled with it. In chronic inflammation of the womb the discharge is intermittent. In mild cases the health of the animal is in no way impaired.
Sterility is common. Loss of appetite and unthriftiness occur in severe cases.
_Treatment_.--Mild cases readily yield to treatment. This consists in irrigating the maternal passages with a one-half per cent warm water solution of liquor cresolis compound. This treatment should be repeated daily and continued for as long a time as necessary.
MAMMITIS.--Inflammation of the mammary gland or udder is more common in the cow than in any of the other domestic animals. In all animals it is most frequently met with during the first few weeks after birth.
_A predisposing cause_ in the development of mammitis is a high development of the mammary glands. The following _direct causes_ may be mentioned: incomplete milking, or milking at irregular intervals; injury to the udder by stepping on the teat; blows from the horns and pressure caused by lying on a rough, uneven surface; chilling of the udder by draughts and lying on frozen ground; and infection of the glandular tissue by _irritating germs_.
The latter cause produces the most serious, and, sometimes, a very extensive inflammation. This form of inflammation may spread from one cow to another, causing the milk to be unfit for food, and bringing about the loss of one or more quarters of the udder.
_The symptoms_ occurring in the different forms of mammitis differ. The inflammation may involve one or more of the glands, and may affect either the glandular or the connective tissue. In some cases the gland may appear congested for a few days before the inflammatory changes occur. The part becomes hot, swollen, tender and reddened. It may feel doughy or hard. If the connective tissue is involved (interstitial form), there is apt to be a high body temperature, the udder may be much larger than normal, is tender and pits on pressure. Loss of appetite usually accompanies this form of mammitis. Very little or no milk is secreted. Sometimes, the milk is greatly changed in appearance, is foul smelling and contains pus. In congestion of the udder and rupture of the capillary vessels, the milk may contain blood.
Mild inflammation of the udder responds readily to treatment. The interstitial form may terminate in abscesses and gangrene. The replacement of the glandular tissue by fibrous tissue in one or more quarters is not uncommon. Death seldom occurs.