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

by Herbert Lester Gilman

Many arguments have been brought forward to show that the prostate produces an internal secretion. It is a well known fact that this organ atrophies after castration, and enlarges as the sex life dwindles. As has been previously stated, Serrlach and Pares reached the conclusion that the gland produces an internal secretion which controls the testicular functions and regulates the process of ejaculation. Also they state that if the prostate is removed, spermatozoa are no longer produced in the testes, and that the secretory activity of the accessory genital gland ceases. The secretion is, at any rate, a stimulus to the internal secretion of the testis.

The thyroid bears a distinct biological relationship to the sexual glands. Removal of the gland results in imperfect development of the gonads, infantilism, and general torpor. Bell (42) believes that the association between the thyroid gland and the genitalia is as intimate as the relation of the pituitary to the genital functions.

Of all the endocrines, perhaps the anterior lobe of the hypophysis is in most intimate correlation with reproduction. Castration results in hypertrophy of this organ, while removal of the anterior lobe usually leads to death. In those cases in which death does not ensue, it results in genital atrophy, stunting, and reduction of sexual activity. In young animals, spermatogenesis ceases entirely even after partial extirpation of the anterior lobe. Biedl (45) states that “in disease of the hypophysis, derangement of sexual activity occurs very early in the course of the disease, shown in women by the cessation of menstruation, and in men by impotence.”

The thymus, as is well known, is quite intimately associated with the development of the genital organs. Its normal disappearance is always associated with the development of sexual maturity in the individual. Hewer (46) conducted experiments to ascertain the effect of thymus feeding on the activity of the reproductive organs in the rat. She concludes in part: “Male rats appear more susceptible to the influence of thymus feeding than female rats. With moderate doses of thymus, sexual maturity in the animals treated is delayed, a phenomenon which is attributed to delayed development of the testis. With large doses of thymus, in the male, the testis is structurally affected: in the young animal in the direction of retardation of development, in the mature animal in the direction of degeneration. This degeneration is confined to the testes. In the degenerating testis, cells of Sertoli appear to be absent: the spermatogonia are present, also dividing, and may lie free in the lumen of the tubule; spermatids, many with abnormal nuclei, are shed into the lumen in large numbers; spermatozoa are practically absent. In the later stages, only a few dividing spermatogonia appear among the debris of the other unrecognizable cells of the tubule. In the epididymis which itself is normal, when the testis is showing degeneration, very few spermatozoa appear, in the later stages none. Many spermatids are present in various stages, and some spermatocytes. Animals in the hyper-thymic condition appear to be sterile.”

The foregoing references will, I hope, serve to bring out the facts that environment and diet, together with the general body metabolism and the endocrines, have a more or less profound effect upon the development, growth, and functioning of the genital system. In the experiments it has been shown that sterility is not necessarily accompanied by any apparent microscopical changes in the gonads, or even at times in the general body health. Nor can we exclude impotency of the male entirely even when the spermatozoa are normal in shape, and motility. Carnett, and others (38), years ago stated: “Indeed, there is abundant clinical proof to the effect that systemic conditions which have no appreciable effect upon the motility or conformation of the spermatozoa materially interfere with reproductive power.” The entire complex genital system is inseparably linked up with the body as a whole, a fact which we must bear in mind at all times.

Impediments to coitus may be due to great difference in the size of the two mated individuals, psychic disturbances, or inability to protrude the penis. Williams (17) mentions several physical impediments, as deformity of the limbs or feet, sore feet, overloading of the rumen, obesity, fear of falling, and paralysis. Coitus may be somewhat delayed, or even not performed as the result of a severe inflammation with sensitiveness of the penis or prepuce. Occasionally tumors of the penis are encountered which may interfere with protrusion of the penis, or its entrance into the vagina. Not infrequently the penis is rendered incapable of protrusion as the result of inflammatory adhesions, tuberculosis of the preputial lymph glands, etc.

Excessive sexual use, within certain limits, probably has not, in itself, any material permanent effect upon the reproductive capacity. The frequency with which bulls used to excess break down sexually, is probably due to the devitalizing effect upon the tissues of the genital organs, this opening the way to bacterial invasion and other destructive influences. Over-use is probably not dangerous, unless continued over long periods, but at the same time it offers greater opportunity for infection to be introduced into the body from intercourse with large numbers of females. Lloyd-Jones and Hays (47) carried on very interesting experiments on the influence of excessive sexual activity of male rabbits on the properties of the semen. Their plan was to mate male rabbits in quick succession, and study the character of the semen on the first service, and every fifth service thereafter. The safe limit was twenty services in three hours. As would be expected, the volume of the semen, after the first few services, became gradually reduced in amount. “In rapidly successive services, the semen becomes less viscous and tends to lose its characteristic milky appearance until at the twentieth service, when the fluid is thin and watery.” It seemed as though there was a well marked reduction in the number of spermatozoa per cubic centimeter in the advanced services. Successive copulations also resulted in a marked decrease in the number of motile spermatozoa, together with a shorter duration of perceptible vitality. The certainty of producing impregnation at the same time became less and less. “This reduction in the per cent of effective matings when the male is sexually overworked is recognized by those engaged in animal breeding as one of the most noticeable and universal concomitants of heavy sexual service.”

In another paper, these same authors studied the effect of sexual excess upon the character of the offspring. In part, they conclude: “By no means thus far used has any inferiority of progeny from the heavy sexual service been discovered. They are fully equal if not superior to progeny from very light service of male.”

Infection is without doubt the greatest single factor capable of producing functional and anatomic changes resulting in varying degrees of impotency and sterility. The changes produced range from the addition of the toxic products of bacterial growth to the seminal fluid, to the complete destruction of the parenchymatous tissue of one or more of the contributing sexual glands. Anatomic changes are by no means essential to the production of lowered fertility. As has been previously stated, the work on veal calves indicates that the genital organs of young bulls are normally free from bacteria. Likewise in normal adult animals, the bacterial content of the genital organs is as a rule low or negative. It is possible that a certain flora is normal for the tract at sexual maturity, as in several other organs of the body, but under the strain of sexual excess, defective diet, or other weakening influences, these organisms may become pathogenic. Streptococci and staphylococci have at times been found in apparently normal parts of the body, and at other times they are found associated with severe pathological lesions in the genital tract. The degree of pathogenicity is of course difficult to determine, except as we find the bacteria associated with abnormal conditions. Carpenter (9), however, injected streptococci into the genital tracts of female calves and produced lesions resembling very closely those from which the organisms had been isolated in adult sterile animals. Personally, I am inclined to believe that the genital organs normally are free from bacteria, or if any are there they are better able to multiply under the strain of devitalization of the tissues. Bacterial invasion, however, does take place quite frequently, but the paths of entrance of the organisms are somewhat problematical. Hematogenous origin is always possible, though it is rather difficult to definitely implicate this mode of entrance. The urethra is perhaps the easiest and most common path for the entrance of bacteria, though even here it is not possible to make definite assertions. Contiguous spread of infection from neighboring structures is very probable in some cases, particularly in pelvic peritonitis. The bacteriological results hardly bear out the theory of Williams that the organisms lie dormant in the genitalia of the animals until the advent of sexual maturity, at which time they acquire pathogenic powers. On the other hand, his clinical observations seem to indicate that this may be possible. Calves suffering from “calf infections” frequently do harbor organisms in their genital organs, but whether or not they persist there till sexual maturity is a matter of conjecture. The most logical theory seems to be that animals from herds in which genital infections are very severe, or those that have had severe attacks of scours or pneumonia, are more susceptible to those infections, due to the early lowering of their vitality. One bull in the department herd certainly had a severe ordeal as a calf, but as a mature bull he was highly fertile. Moderate sexual use and proper sexual hygiene probably had much to do with this. In the bull, infection of some part of the genitals, during some period of life, is very constant, however, whether or not it is productive of observable changes in his breeding efficiency. The finding of the fine connective tissue strands and tufts on the serous surface of the tail of the epididymis of practically all bulls examined, both sterile and fertile, indicates past or present infection of the scrotal sac. The vesicles and tail of the epididymis are, as stated previously, the most commonly invaded tissues of the tract. The testes are less frequently involved.

While it is difficult to obtain irreproachable proof that the bull is a disseminator of genital infections, the findings of clinicians quite clearly indicate that this is true, and laboratory methods tend to support this assumption. Williams believes that not only may the bull infect the female with organisms which interfere with the given conception, but that he often implants there organisms which interfere with future pregnancies, and even with the life of the individual in some cases. The high abortion and sterility rate following the use of certain sires, and the appearance of characteristic infections after service to certain bulls, clearly indicate that in all probability the bull does eliminate with his semen those organisms which produce lesions in his genital organs, and are capable of infecting the female. W. L. Williams (48) cites the case of a pure bred herd in which breeding had progressed satisfactorily until heifers had grown to breeding age and a second bull was obtained. “Some cows of the old herd were also assigned to the young bull which had not previously been in service. The cows bred to the old herd bull continued to breed normally. The cows and heifer’s bred to the new bull conceived with difficulty or not at all. Those which conceived mostly aborted, and those which calved had metritis and retained fetal membranes. The two first cows in which pregnancy terminated died of metritis.” I have frequently had semen samples sent in from bulls that were not only failing to get cows with calf, but following each service the females showed a severe vaginitis. W. W. Williams worked in a herd in which service to certain bulls was in each case followed by a severe vaginitis and cervicitis, only to be followed later by a characteristic salpingitis.