A study of some factors influencing fertility and sterility in the bull

by Herbert Lester Gilman

Both the abscess formation and cystic conditions are undoubtedly initiated by an obstructive inflammation of all or part of the excretory duct. This is, however, a protective mechanism, for where the duct is closed the bacteria and exudates are unable to reach the urethra and contaminate the semen.

Prostate and Cowper’s Glands: These glands were more or less neglected in the early part of the work, but later were subjected to the same examination as other parts. Of the thirty-six of each type of gland examined, I failed to find one with any gross changes, but two prostates were found that presented a mild catarrhal inflammation of the mucosa. It is probable that Cowper’s glands, as well, occasionally undergo inflammatory changes.

Semen: The semen, made up as it is of mixed products of the testes and accessory sexual glands, is very often abnormal, as would be expected in view of the frequency with which changes occur in the glands contributing to its formation. The normal semen is remarkably adapted to its function of nourishment and stimulation of the spermatozoa, and their conveyance to the internal female genital organs. The spermatozoa are extremely sensitive to changes in their environment, with the result that any alteration of the physical or biochemical content of the seminal fluid may cause death of the sperms. With this in view, we must remember that disease of any of the contributing organs is a potential danger, and threatens the potency of the animal. Each or all of the glands may add bacteria, acid secretions, or inflammatory exudates. On the other hand, they may not function at all. In each case, however, the semen is altered.

Unfortunately it is impossible with present methods to obtain the fluid absolutely free from vaginal mucus, but with care it may be secured reasonably free from contamination by douching the prepuce of the bull and vagina of the cow before service. This method was used as often as possible in collecting the samples. The usual amount of semen obtained was from six to ten cubic centimeters.

With a hypersecretion of one or all of the glands, the semen becomes quite thin and watery, with a deficiency of solid matter, together with changes in reaction. On the other hand, hypofunction results in a secretion too viscid, which is equally unsuited to the requirements of the spermatozoa. The thin watery semen clots imperfectly or not at all, and clotting is essential in protecting the spermatozoa from the acid secretions of the vagina. Likewise, a medium too viscid is a distinct hindrance to motility. Changes in reaction are very frequently encountered. The sperms are very sensitive to dilute acids, so that with even a slight acidity motility may diminish or entirely cease. Purulent inflammatory exudates are occasionally mixed with the semen, and although the pus cells themselves have not been found to be destructive to the sperms, certain degeneration products in the exudate are very toxic, and inhibit or destroy the motility. So far, I have failed to find red corpuscles present. One very interesting sample of semen was quite thick, of a yellowish green color, and of a distinctly acid reaction. The secretion from the vesicles was later found to be of this same character, and was due to a Ps. pyocyaneus infection. The vesicles were highly inflamed and degenerated. The spermatozoa were in this case markedly decreased in number, and devoid of motility.

The early precipitation of the “Boettcherchen” crystals seems to be intimately connected with sterile semen, or spermatozoa of lowered vitality. Likewise, a decrease in solid matter is often seen in a deficient secretion. In normal semen, the clot disappears after standing a time, and a thick sediment settles out. This sediment is decreased in amount as a rule in abnormal semen.

Spermatozoa: Spermatozoa, the essential germinal elements, are very frequently abnormal, changes in which may be manifested in many ways. We may divide the deviations into changes in structure, and changes in the motility which is so indicative of the intrinsic vitality of the sperm. Reynolds (34) describes two forms of abnormal motion. The first is “rotary swimming,” in which the sperms move forward progressively, and sometimes with fair rapidity, but in a spiral screwlike manner. He states that this type of swimming is very awkward, easy to recognize, and is usually of quite long duration. The other form termed “pendulum swimming,” he states, is less common than the rotary swimming and is usually confined to relatively fewer sperms in a given field. “In this the middle piece and upper tail seem to lose their flexibility and balance to a considerable degree, and the lower tail motion swings the forward part of the spermatozoon to and fro with a pendulum movement. This type of swimming yields very poor progress.”

One factor we must bear in mind in the study of the semen obtained from the vagina, is that the spermatozoa may be highly motile before ejaculation, but the admixture of hostile vaginal mucus may inhibit or destroy the motility. On the other hand, the conditions may be reversed. Cary (35), in one instance, found that the spermatozoa in a sample of semen collected from a condom, appeared to be of very low vitality, while when they were mixed with the vaginal secretions, an exaggerated activity was manifested. May we not have to contend with this factor in some herds in which there is a very distinct acid and toxic vaginal secretion from the products of cervicitis and vaginitis?

In a study of motility, we must consider not only the abnormal types which may be encountered but the percentage of motile cells, and the duration of the movement. In necrospermia all the ejaculated cells are motionless or dead. In other specimens, varying percentages of the cells are without motion, and the others may be possessed of full and lasting motility. On the other hand, the motility in some cases is very active at first, but quickly subsides even under the best of conditions. The appearance in freshly ejaculated semen of numerous sperms that have a tendency to take on the “undulatory tactile” type of motion when they should be in a highly active state, is very indicative of lowered vitality. Many specimens present this very picture, whereas the very active progressive movement should, under proper conditions, survive for a considerable time before it gives way to the second, and slower type. The cells frequently early bunt into epithelial cells or clumps of immotile sperms, then back out and move around sluggishly, only to repeat the same performance till they stop moving entirely. I have seen one specimen in which the sperms all tended to clump. Whether this was the result of some agglutinative substance in the vaginal secretion is problematical. I have seen several specimens of semen in which practically all the sperms were motile when first examined, but the motion did not survive for any great length of time. Even a small percentage of motionless sperms or of those showing lowered vitality is a considerable factor in potency. Although millions of the germinal elements are ejaculated into the vagina, large numbers of them are destroyed or become motionless there, and a small number is left behind in the cervix and uterus; so that even though but a single sperm is required for fertilization, the chances of impregnation are diminished in proportion to the number of dead or defective sperms.

Aspermia: Absence of spermatozoa in the semen is rarely encountered, and is probably due either to total cessation of spermatogenesis, or to an obstruction at some point in the system of excretory ducts. I have seen but one case of this character. The semen of this bull was greatly increased in amount, and of a thin watery consistency. Due to lack of cooperation on the part of the owners, the tract could not be obtained for study. Oligospermia, or a diminution of the number of spermatozoa, is quite common, and is undoubtedly associated with defective spermatogenesis, either as a result of poor mitosis of the seminal epithelium, or degeneration of the elements before maturity. This condition may vary from the finding of only occasional dead sperms in the field, to but a slight decrease in the usual number of normal sperms observed.