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

by Herbert Lester Gilman

Diet: Under this heading we may include not only the effect of deficient food, but also constitutional disorders, as a result of which the organs of generation and those glands guarding their function receive insufficient nourishment. It is a well known fact, and long has been, that animals fail to breed when they are in a run down condition or when they are fed a deficient diet. Cary (35), quoting Hagner, states that the virility of the spermatozoa is often in direct proportion to the general physical condition of the patient.

Reynolds (34) emphasizes the fact that it is an established principle among animal breeders that a high protein diet in both sexes is essential to full fertility. “Oligospermia with deficient vitality of the spermatozoa is not infrequently found from constitutional disorders. It can easily be demonstrated in animals that both low diet and conditions of life that produce a nervous excitable state are attended by oligospermia.” Animals that are closely confined, those that are over-fat (show animals), as well as those fed a deficient ration very frequently fail to breed, but exercise and change of diet soon overcome the impotency.

Dutscher, Hart, Steenbock, and other biological chemists have done extensive work to show the essential importance of vitamines and minerals in the diet. Their results indicate that animals cannot thrive and breed normally when fed a diet composed solely of the products of one plant. There must be variety, and there must be not only a correct nutritive ratio, but the mineral and vitamine content must be present as well. Cows fed on the products of one plant often failed to breed, and if conception occurred, it invariably resulted in a premature birth, or the birth of weak and poorly nourished calves. The work of these authors is fundamental, and brings out many important points. Is it not probable that the deficient diet results in weakened tissues which are easier prey to the invasion of bacteria?

Macomber and Reynolds (39) experimented upon white rats to determine the effect of defective diet as a cause of sterility. They call attention to the confusion caused by the application of the term sterility to most, or all, infertile matings. They believe that failure of reproduction is, in fact, the result of decreased fertility rather than of actual sterility on the part of the two individuals concerned. “There are certainly a large number of infertile matings which are purely functional and due to physiologic alterations or local conditions. Such physiological alterations moreover coexist in the sterilities of pathologic origin and when unrecognized and consequently unremedied, undoubtedly explain a large proportion of the continued infertilities after operation.” Is it possible for a bull to be infertile to the cows in his herd that have been fed a deficient diet, and at the same time to breed well when mated to animals outside this herd? This is rather improbable in practice, but there is always the possibility of its occurrence. In the experimental work, white rats were used: one strain from the Wistar Institute with a fertility of about 65 per cent, and the other from a Dr. Castle’s strain with a fertility of about 90 per cent. The Wistar rats were fed in groups, each group receiving a diet deficient in a certain substance: calcium, protein, or fat soluble vitamine. To this group was added a diet deficient in both calcium and protein (war diet). These diets reduced the fertility of the groups from the original 65 per cent, to 55, 31, and 14 per cent respectively. It delayed the appearance of fertility in young rats raised on these diets, and lowered its degree in the mature animals. Most of these rats, however, though infertile to each other, bred promptly when mated to the Castle rats of known fertility. This demonstrates clearly that relative infertility of given matings does occur. One interesting feature of the work is the fact that in the matings on the single deficiency diets, four deliveries of macerated fetuses occurred and there were two more in eight deliveries from those reared on the war diet. No cases of this kind had previously occurred in this strain, which had been under observation for several years. Does this throw any light upon the cause of macerated fetuses in cattle? Microscopically the testes and ovaries of these infertile rats showed no observable changes, a fact which is of great importance to bear in mind.

Williams, in his book on disease of the genital organs, brings out quite clearly the relation of defective diet, overfeeding, and lack of exercise, to reproductive efficiency.

Novarro (40) observed that pigeons fed on a diet without vitamine B showed degeneration of the seminal epithelium, with hypertrophy and hyperplasia of the interstitial cells of the testis. Another author (Allen) showed that reduction in the quantity of water-soluble vitamine in the diet of rats resulted in total degeneration of all the germ cells, but it did not interfere with growth and development in other respects.

The observations of Williams (41), in a pure bred beef herd in Hawaii, clearly demonstrate the intimate correlation between poor fodder as the result of extreme drought, and the accentuation of, or increased susceptibility to, genital infections, as demonstrated by clinical findings. The genital disorders started soon after the onset of the drought, and immediately took a downward trend with the advent of the rainy season.

Judging by the work quoted, we will observe that deficient diet, though it does not always affect the general health, has a profound effect upon the genital organs of both sexes, associated with disturbances of spermatogenesis in the male. In most debilitated and weakened conditions of the male, spermatogenesis ceases or is markedly defective. We must, undoubtedly, explain this fact upon the ground of deficient nourishment to the reproductive organs or possibly the endocrines. The vitamines have been termed nuclear nourishers, and their absence probably results in nuclear deficiency.

Endocrines: Bell (42) emphasizes the fact that not only the structure but also the function of every part of the body is in close correlation with the rest. “This is essentially true of the ductless glands: the shadow of their influence is over all.” Further he states that when we remember that the individual exists to perpetuate the species, it is not difficult to realize that the metabolic factors concerned in reproduction are the same as those related to the individual metabolism. It follows, therefore, that the ductless glands which regulate the individual metabolism concern equally the reproductive. Brown (43), discussing the same subject brings out the generalization that the sympathetic, since it is the most primitive part of the nervous system, is closely associated with the endocrine system, a still more elemental means of communication in the body. Also since specialized reproductive cells appear before the nervous system, the organs of reproduction remain closely associated with the older chemical reactions now specialized in the endocrine glands. “The endocrine glands, the reproductive organs, and the sympathetic nervous system, therefore, remain as a basic tripod, and it is not likely that a disturbance will occur for long in one limb without affecting the other two.” The former author believes that the gonad keeps the other ductless glands informed of the needs of the genital tract, they in turn influencing the general metabolism. Jump (44) states: “We are therefore justified in believing that there is a correlation of function between these (endocrine) glands and that some cases of sterility are probably due to a derangement of this correlation.” Biedl (45) concludes: “There appears to be an intimate anatomical and physiological interrelationship between the different blood glands which is manifested clinically by the fact that the pathological disturbance of one gland is accompanied by symptoms pointing to the functional derangement of one or more of the others. Knowing, as we do, the many sided interactivity which subsists between the different internal secretory organs, it is readily conceivable that isolated diseases of single organs of this group are very much rarer than, at the first glance, they would appear to be. In the present state of our knowledge, the only course of investigation which is open to us is to start with the known results of the functional derangement of any organ, and, by following these up, to seek the primary link in the pathological chain.”

Most workers seem to agree that a special connection exists between the normal function of the adrenal cortex and the sexual organs. Tumors of the former are usually associated with sex abnormalities, and feeding young animals the gland substance seems to stimulate growth of the testes.