As obstructions of one kind or another are frequently encountered, it has been found necessary to resort to artificial methods of insemination in those cases where the hindrance can be overcome and a passage forced into the uterine cavity.
For many years it has been the practice with some stud-managers to pass the fingers into the uterus of mares which failed to breed, before putting them to the horse, the object being to open the passage for the entrance of the seminal fluid, and in many instances with the result that pregnancy has followed the service.
In untutored hands this method of clearing the way has sometimes been followed by bad results, but when properly performed it is quite a harmless and simple operation. One more safe and reliable, however, is to resort to artificial insemination. This is effected by means of an instrument (inseminator) designed to collect the semen of the male from the vagina of the female after service, and transfer it directly into the uterus. The practice has been largely adopted by breeders, and with a considerable amount of success. Among the earlier examples of its value in this country, was the yearling filly "Sandflake", the daughter of "Trenton" and "Sandiway", which, at the dispersal sale of the stud of the late Duke of Westminster, was sold by auction to Mr. Sievier for 5500 guineas. This filly was the result of conception following upon artificial insemination.
In America the operation had been practised on a considerable scale for many years, and to a less extent in France, Germany, Russia, India, and other countries, before its adoption in these Islands was at all general.
Mares which have been to service again and again year after year without being impregnated by natural means have at once been rendered fruitful by artificial insemination. Thus valuable animals, relegated to the drudgery of the farm as lost to the race, have been restored to the stud, and converted into valuable assets. The advantage of this mode of propagation is not alone that it overcomes the impediment to insemination in the mare and renders her fruitful, but by reducing the work of the sire his strength and vigour are conserved, and his services become more effectual.
Fig. 535. - Artificial Insemination: Gathering the Semen A, Uterus; B, os uteri; c, vagina; D, inseminator; d', bulb of same; E, rectum; F, bladder; G, the semen.
In the case of old and valuable stallions, artificial insemination may be made to reduce their work by one half, or even more, while at the same time it preserves their productiveness and prolongs their lives and usefulness at the stud.
By the same means, young fashionable stallions may be protected during the period of growth against venereal excess, which in so many instances is allowed to sap the constitution and weaken not only the individual but his offspring.
The overstrain which the rush to fashionable horses inflicts upon them is responsible for much of the premature mortality and impotence from which many of them suffer, and to this is attached an immense annual loss to farmers and breeders.
Artificial insemination requires that the operator be provided with a suitable instrument to gather up and transfer the semen to the uterus of the mare, and that certain precautionary measures against failure be observed. In this latter connection it is necessary: (l) that the temperature of the syringe employed be raised to 100° F., which may be done by placing it in a pail of warm water; (2) that it should be thoroughly clean, (3) that the semen should be injected into the uterus of the mare soon after it leaves the sire. Exposure to the air, to cold, or strong sunlight, weakens the vitality of the spermatozoa, and when unduly prolonged kills them and defeats the operation.
Fig. 536. - Artificial Insemination: Passing the Inseminator into the Uterus A, Uterus; B, os uteri; c, vagina; D, inseminator; d', bulb of inseminator; E, rectum; F, bladder.
The mare to be inseminated must, of course, be "in use", and while in this condition should be served by the horse in the usual way.1 The seminal fluid discharged during the service will be deposited on the floor of the vagina near to the mouth of the uterus.
1 Under favourable conditions successful impregnation has followed when the semen has been transported long distances.
When the horse has left the mare, the warm syringe should be introduced into the passage and carried forward by the left hand to the part indicated in the illustration (fig. 535), while the india-rubber ball is being compressed by the right one.
The point of the instrument should then be directed into the seminal fluid (g, fig. 535), and the pressure removed from the india-rubber ball, and as a result the fluid will stream into the syringe. The syringe having become charged, the nozzle is introduced into the uterus (fig. 536), the ball is squeezed, and the operation is completed.
Where it is intended to inseminate a second or a third mare, a fresh charge of semen should be obtained from the same service in the manner described, and the operation repeated.
A supply of seminal fluid may sometimes be caught in a cup directly from the male as he leaves the mare, or some of the service discharged by the mare may be secured in the same way.