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

History

References to, and investigations relating to, the part played by the bull in the process of reproduction in the herd, and in the spread of genital infections, have been limited largely to those phenomena caused by Bact. abortum. Bang (1) originally called attention to the possibility of the male transmitting the organism discovered by him, but he reached no definite conclusion on the subject. James Law (2) writing on contagious abortion in cows, early suspected this possibility when stating under “casual infections,” that—“In a case which came under the observation of the writer recently, a family cow, kept in a barn where no abortion had previously occurred, was taken for service to a bull in a herd where abortion was prevailing, and though she was only present at the latter place for a few minutes, she aborted in the sixth month.” Jansen, as quoted by Sand, reports the case of a cow from an aborting herd having been taken into a herd that had been previously quite free from the disease. Soon after her arrival she aborted, and later cow after cow of the original herd aborted. The owner kept the matter a secret, and sent his cow to a neighbor’s bull for service, with the result that for two years abortion prevailed among cows served by this bull. McFadyean and Stockman (3) later, in experimental work, attempted but failed to infect cows by using a soiled bull for service. Hadley and Lothe (4) state: “A large number of stockmen hold that the bull is an important factor in the transmission of contagious abortion in herds. A smaller number believe that the bull merely acts as a passive carrier of the abortion disease and is not actively concerned in the transmission.” In a subsequent bulletin, Hadley (5) remarks: “The abortion organisms may enter the body ... during sexual intercourse.” In an experiment carried on by the same author and co-workers, abortion-free virgin heifers were mated to abortion-infected bulls, infection being evidenced by positive reactions to the complement fixation and agglutination tests. His results indicate, he believes, “that the bull is not so important a factor in transmitting abortion as many believe.” The conclusions are: “Bulls may become infected with abortion bacilli. Bulls that reacted to the blood tests were incapable of disseminating the abortion disease to the abortion-free heifers with which they were mated. Bulls appear to possess a sexual or individual immunity to abortion infection that renders them less susceptible than cows and induces a milder form of the disease. The resistance appears to be due to certain anatomic and physiologic differences in their sexual organs which make them less favorable places for the growth of the abortion germs than those of the opposite sex.”

Buck, Creech, and Ladson (6) applied the agglutination test to 325 mature bulls, of which 288 were negative and 37 positive. Bacillus abortus was isolated from five animals, of which three showed marked lesions, two in the seminal vesicles, and one in the left testicle. They conclude: “_B. abortus_ may involve organs of the generative apparatus of bulls, producing chronic inflammatory changes. Of the generative organs, the seminal vesicles appear to furnish the most favorable site for the lodgement and propagation of abortion infection.”

Schroeder and Cotton (7) cite the case of a bull which reacted to the abortion test and, on post mortem, Bact. abortum was isolated from an abscess of one epididymis. They state: “Our attempts to produce a similar case of infection artificially failed, and, in agreement with the difficulties many investigators have had to obtain incriminating evidence against bulls, we have thus far failed to infect bulls in any way that justifies the assumption that they are important factors in the dissemination of abortion disease.” Further, they conclude: “Regarding the dissemination of abortion disease by bulls, we may say, however, that it would be foolhardy in the dim light of our present knowledge to take liberties with reacting bulls, or bulls from infected herds, or promiscuously used bulls.”

Cotton (8) failed to demonstrate the presence of abortion bacilli in the genital organs of the bull used to serve aborting cows, or in the testicles of two bull calves, one of which had been fed and the other injected with the cultures of the abortion bacillus. He concludes that the bull does not harbor the organisms in the testicles. Carpenter (9) injected both streptococci and Bact. abortum into the scrotal sacs of young calves, and intravenously in others. In no case was he able to recover the organisms from any part of the genital canal, except for a streptococcus in one instance. Rettger and White (10) were unable to obtain evidence of the presence of Bact. abortum in three bulls slaughtered after repeated reactions to the complement fixation and agglutination tests. The three bulls had been under observation for three years, with no conclusive evidence to indicate that they were a source of danger to the herds in which they were a part. They believe that the bull transmits the infection as a passive carrier.

Attempts at artificial inoculation by natural channels have failed, with the possible exception of McFadyean, Sheather, and Minett (11) who were able to infect the bull by the prepuce in two cases and by the mouth in one case. The results, however, are by no means conclusive. They conclude, nevertheless, that cattle of any age of either sex may be infected by natural channels with the bacillus of epizootic abortion.

Schroeder (12) carried out investigations to ascertain the frequency with which bulls react to abortion tests, and the frequency with which lesions chargeable to abortion bacilli occur in the reproductive organs of reacting bulls. Studies were also pursued which he states conclusively prove that bulls with infected reproductive organs may expel abortion bacilli with the seminal fluid. In the first two mentioned investigations 325 bulls from a Washington abattoir were tested, and slaughtered upon reaction. “Approximately ten per cent of the bulls reacted, and approximately ten per cent of the reacting bulls showed lesions of the reproductive organs from which abortion bacilli were isolated.” The value of these studies, he emphasizes, lies not in “that they give us a measure of the proportion of bulls that react positively to abortion tests or the proportion of reacting bulls that are carriers of abortion bacilli,” but in “the fact that they show that abortion bacillus disease of the bull’s reproductive organs is not a wholly unique affection which practically may be ignored, but an important condition that must be taken into account in our efforts to combat infectious abortion, since it has been proved to be associated with contamination of the seminal fluid.” In discussing the method by which infected bulls transmit the organisms to cattle, he believes that leakage of semen from the penis, or vaginas of cattle after service, contaminates the food which subsequently gains entrance to their digestive tracts. As the result of a series of experiments, he states: “... the results fail to justify in the least degree the assumption that cows are infected with abortion bacilli via their vaginas or uteruses at the time of copulation, or that the bull, through copulation, is an agent in the spread of abortion disease.”

The work so far alluded to, has been limited to infection with, and the transmission of, Bact. abortum and the lesions associated with such infection. The last mentioned author, however, states: “A search for other specific causes of abortions among cattle has not been neglected, and bureau investigators could relate at great length stories similar to those which investigators have told about microorganisms isolated from the products of abortions and the uteruses of cows that have aborted. Bacilli of various kinds, different types of micrococci, and spirilla or vibrio have been found repeatedly; but when their pathogenicity has been tested in accordance with widely recognized and accepted and required bacteriological standards, not one shred of evidence has been obtained to prove them true etiological factors of bovine abortions. What role such microorganisms may have as causes of the sequellae of infectious abortions, and of other, possibly, independent, abnormal processes in the reproductive organs, is far from clear and merits careful study.” Hadley (5) mentions the fact that: “Unquestionably the male often becomes infected with the germs that produce the various secondary diseases in the female, which are properly classed under the more inclusive term ‘abortion disease.’” Also, speaking of the rarity with which the bull acquires abortion infection, he alludes to the fact that he may act as a “mechanical carrier of various disease germs from an infected to a healthy cow.” Carpenter (9) working on the female genital tract, comes to the conclusion that, in all probability, the genital organs are normally free from bacteria. Barney (13) quoting Huet finds that bacteria may be present in the seminal vesicles of healthy animals (horses, cattle, pigs, and laboratory animals). This, he states, corresponds with the well recognized findings in other parts of the genito-urinary tract, not only in animals, but in man. He (Huet) has further found that in animals dying of acute septicemia, the specific organism (anthrax, pneumococcus) is to be found in the vesicular secretions. Furthermore it was definitely shown that an infection could be transmitted to the female during the act of copulation.