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

by Herbert Lester Gilman

Abnormalities in morphology may be classified into immature types, and deformities or imperfect development of the head and tail. Defective spermatogenesis occurs so frequently that it is not surprising to find spermatozoa in various stages of development cast into the excretory ducts. The various stages passed through in the development, from spermatogonia to adult sperm, are numerous, and it therefore is to be expected that we should see in abnormal semen many different immature forms. No classification of the various types can be made, but a clearer understanding of them can best be obtained by a review of the process of spermatogenesis.

Spermatocytes and spermatids are seen in the more severe types of defective spermatogenesis, and are relatively uncommon, while the more mature forms that result from the transformations of spermatid to adult cell are very often seen. Some of these intermediate types are large oval cells without distinct nuclei and as a rule with poorly developed tails. Cells with no tails or distinct nuclei, those with protoplasmic appendages to the head or tail, and various other types, are occasionally encountered. Most of these are motionless and incapable of producing impregnation. Others are active, but survive a comparatively short time. According to Cary, the production of the immature cells is an effort on the part of the testes to supply an abnormal demand, and their presence indicates that the fertility of the semen is impaired.

The deformities, which may be divided into cephalic and caudal groups, are also the product of defective spermatogenesis, or they represent a degenerative process induced possibly by abnormalities of the fluid environment. It is rather difficult, however, to distinguish between deformities and immature types. The two most common cephalic deformities are what might be called macro and microcephalic forms. In the former, the head is enlarged to a greater or less extent, it is usually defective in staining qualities, and its outline is indistinct, due to degeneration of the covering membrane. This type is seen in Fig. 32. Also the shape of the head is usually abnormal, being either quite rounded, long and narrow, or short and very broad. Cells with protoplasmic appendages, though they are more properly an immature type, occasionally give the head a greater volume. Microcephalic sperms vary from those slightly smaller than normal to those in which the head is represented by a slight knob. In some cells, the head is small and round, in others, short and stubby, while another type is normal in outline but diminutive in size. These forms likewise are, as a rule, deficient in staining qualities, and are undoubtedly degeneration forms, occurring either as the result of faulty development, or degeneration subsequent to their formation. Cary believes they are degeneration types because in the majority of cells the tail is apparently fully formed, and in the normal process of evolution the tail is the last part of the cell to be exhibited. Double headed forms are quite rare, but they nevertheless appear at times. Their significance is difficult to explain. Another very frequent deformity of the head is a marked constriction at the posterior part so that it is the shape of a pear or top as in Fig. 27. In some, the head is otherwise normal in size, while in others it is much elongated, as in Fig. 28, or considerably atrophied. A constriction at the middle of the head, as in Fig. 29, is not uncommon. Both defects are undoubtedly the result of nuclear deficiency, as the nuclear part of the head in these cases is much diminished in size, and stains very deeply or not at all. I have seen spermatozoa, the heads of which were like an inverted cone, with a bulging rounded base. Other heads are even somewhat contorted and bent on themselves, as shown to some extent in Fig. 26.

Under caudal deformities, the most frequent form encountered is a thickening of the connecting piece. This may occur as a uniform thickening, or as a bulging appendage. Rudimentary development of the tail, the presence of two poorly formed tails, and defective development of the connecting piece occur rather infrequently.

All these immature and defective types are, as a rule, motionless, and of course incapable of producing fertilization. Their presence indicates lowered fertility of the semen. Besides these deformities, there are sperms showing a curvature of the tail at an acute angle just posterior to the neck,—the so-called “wry neck.” Their significance is difficult to explain, but they occur frequently in semen fixed and stained by the same routine methods used on samples in which they are absent. They probably are not the result of the methods used in fixing and staining. Some think they are slightly immature types, or that the condition is produced by abnormal contractions of the tail. The majority of sperms, however, especially those from highly fertile bulls, do not show this type at all.

The most common changes in the spermatozoa, are those in which there is a separation of the head from the tail, and degeneration of the head as evidenced by reaction to stains. The separation of the head from the tail always occurs at the neck, and often is associated with degeneration or abnormalities of the head. The separation, in the majority of cases, indicates some lowering of vitality in the elements, although in many instances traumatism produced in making smears or collecting the samples is responsible. Various forms of abnormal staining of the head are very common. The cell membrane, which is normally distinct and sharp, becomes blurred in outline. Normally, the head takes a good differential stain, the anterior part staining lightly, and the posterior part somewhat deeper. The nucleus is distinct in outline and well defined. The lighter “inner body” stands out in well stained specimens. As the result of degeneration, the whole head may take the stain uniformly, either slightly or much deeper than normal, according to the degree of degeneration. The whole problem of staining, however, depends very much upon the methods used, and the care with which they are applied. When a good method is obtained, it should be adhered to, and used uniformly on all specimens. As a rule, however, a certain amount of practice will enable one to differentiate between the sharply outlined, clearly staining normal forms, and those that show abnormal reactions to the stains.

Bacteriology

A complete bacteriological study was made of the genital tracts of fourteen normal young veal calves (six to twelve weeks old), four mature fertile bulls, and sixteen mature bulls, either sterile or impotent to some degree. Together with these, the tracts of eleven aborted fetuses, seven calves dying from calf infections (scours or pneumonia), and sixteen bulls slaughtered at an abattoir were studied bacteriologically. Occasionally, studies were made of individual seminal vesicles or testes, when these parts alone were brought or sent in. The history of the abattoir animals was, of course, quite indefinite or entirely negative. On the killing floor, many tracts could be studied for pathological changes, but in the bacteriological work it was difficult to care for more than two tracts on each visit.

The results of the bacteriological examinations are given in the appended tables, in which the tracts are divided into six groups. The results in Group I. consisting of normal veal calves, indicate that the genital organs of young male calves are, under normal conditions, free from bacteria. Carpenter (9) obtained like results in examining the genital tracts of heifer calves. The cultures made from the seminal vesicles and testes of all these veal calves were, with two exceptions, negative. Both seminal vesicles of one tract and one of another yielded cultures of Staphylococcus albus.

Adult bulls of known fertility were naturally difficult to obtain, only the four animals in Group II being available for examination. Two of these (Nos. 1 and 2) were from the experimental herd kept by the department, and at all times had a good breeding history. The other two were good breeders, but were slaughtered because of poor pedigrees. Bull 1, raised in the department herd, had a severe attack of scours when a few weeks old, while the calfhood history of the other is not known, he having been purchased after reaching sexual maturity. The cultures from the genital organs of the former (Bull 1) were entirely negative, except those from the left epididymis and scrotal sac, which yielded growths of Streptococcus viridans. All the organs of the tract from this animal were normal, except for the fact that numerous strands of connective tissue extended from the serous covering of the tail of both epididymes to the adjacent part of the parietal layer of the tunica. The tract of the other failed to show any organisms. The only evidence of any abnormality was the presence of the same connective tissue strands on the tail of the epididymis, as in the first tract. The other two bulls gave negative cultures from all parts.