Thesis (Ph. D.)--Ohio State University, 1969. / Includes bibliographical references (leaves 99-101). Available online via OhioLINK's ETD Center

<p> There have been many changes in the United States sheep industry over the years. Decreasing profitability of wool production has shifted the focus of many producers to strictly meat production. In south Texas, extreme high summer temperatures add an additional challenge in raising wool breeds of sheep. Hair sheep are gaining popularity in lamb-only production systems as they are more adapted to hot climates and eliminate shearing costs. The Dorper is the most popular breed of hair sheep throughout Texas due to superior lamb carcasses. Maximizing reproductive efficiency is critical for increasing the profitability of sheep production. Accelerated lambing systems can produce 3 lamb crops every two years versus 1 lamb crop per year. For this to be accomplished, ewes must be capable of breeding early post-partum and at all times of the year. We determined the reproductive characteristics of Dorper ewes. In the absence of a ram, Dorper ewes were anestrous from March until May. We observed considerable variation of ewes when both entering and ending anestrous. During the initial breeding season, 7-d CIDR^&reg; treated ewes, which conceived 1^st service, had a significantly lower mean day of birthing (3.2 &plusmn; 2.1 d) compared to (10.1 &plusmn; 1.9 d) control ewes, resulting in a shorter lambing duration. During the seasonal anestrous period both CIDR^&reg; treated and control post-partum Dorper ewes were stimulated to ovulate while in the presence of the ram. However, during this time, 9-d CIDR^&reg; treatment significantly shortened both overall ram to lambing interval (152.8 &plusmn; 3.2d vs.165.7 &plusmn; 3.0 d) and first service ram to lambing interval (149.3 &plusmn; 1.3 d vs. 160.7 &plusmn; 1.5 d). Fall-born Dorper ewes with known birth dates had a mean age of puberty of 306.5 &plusmn; 4.9 d. Fall-born yearlings and spring-born ewe lambs were exposed to a ram during the first fall breeding season following their birth. While no difference was found in overall conception rate, fall-born yearlings had a significantly greater first service conception rate (83.3 %) compared to spring-born lambs (28.6 %). The findings of this study illustrate that Dorper ewes have the potential to be utilized in accelerated lambing systems in south Texas. By achieving a high conception rate post-partum simultaneous to the anestrous season, we were able to maintain an 8 mo lambing interval during the first two breeding season. We conclude that the reproductive attributes of the Dorper ewe makes them an excellent choice for sheep producers throughout South Texas.</p>

In Newfoundland the production of ranch mink has been carried on, on a limited scale, for well over twenty years. However, during the last seven years, with the assistance and encouragement of the Newfoundland Government, mink ranching has been co-ordinated and largely centralized near the southern end of Trinity Bay. This region of the Avalon Peninsula was chosen for several reasons, the most important of which was its close proximity to a supply of a large variety of marine products. Trinity Bay is a centre of pothead whale fishing and consequently whale meat and whale liver are normally available as ingredients in mink rations.

In many respects, the significance of the reproductive cycle in the pig differs from that of other domestic animals. Unlike the cow or the eve, the sow owes her value solely to her ability to produce and rear many young. The more young she can produce which are viable to marketable age, the greater her value. The ideal sow is defined as the one which begins to breed as early as is compatible with her future productivity, continues to breed as often as possible for as long a life as possible, and produces large litters of healthy pigs rearing them to good weaning weight without loss. In brief, fertility, fecundity, mothering ability and milk yield must all be high.

By the beginning of the century, it had been conclusively established that the most efficient utilization of any ration depended not only on the proper balance between the heretofore known essential nutrients, viz.: proteins, fats and carbohydrates, but on a consideration of balance with regard to minerals and vitamins. Analyses of the animal body and of eggs reveal the presence of a large number of mineral elements. However only a few of these have to be added to the normal ration either because some are not essential in the performance of the physiological activities of the animal or the ingredients used in the ration contain enough of the ethers in available form. The two most abundant minerals both in the body and the egg of the chicken are calcium and phosphorus. Supplementation of the ration with both of these elements is essential in order to meet the birds’ requirements.

Production of food and continuous supply thereof is perhaps the most critical factor in sustaining the growth, economy and security of a nation. This point is brought into the foreground most strikingly during periods of war, particularly when rationing has to be imposed. During and since the Second World War, pressure on agriculture in general and on animal industry in particular has mounted continuously to produce more and better meat, milk and eggs, and at less cost to the consumer, to keep in step with the rapidly growing population. With the prices of basic livestock feeds and protein supplements remaining high or rising, nutritionists have exerted a tremendous effort to find ways and means to enhance utilization of the basic nutrients - protein, carbohydrate, fat.

The idea of the control of the sex ratio is not a recent one. According to Gordon (1958), men have been attempting to control or predict the sex of their offspring for thousands of years. This subject was discussed in a Chinese Manuscript about 4,400 years ago. An Egyptian papyrus of 2,200 B.C. noted that a pregnant woman with the use of greenish cast was certain to bear a son. Aristotle believed that the placing of the marriage bed in a north-south direction favored the conception of boys. These are examples of the many beliefs that have been reported regarding sex determination, which have since been demonstrated to be false. The scientific history of the subject of sex determination began with the discovery of the genetic mechanism by which sex is determined in mammals. According to genetic theory, the male mammal has a special pair of sex chromosomes made up of one X chromosome and one so-called Y chromosome.

Vitamin A has been studied intensely in its application to the fields of animal and poultry nutrition. Over forty years of investigation have provided extensive data on the chemistry, analysis, deficiency symptoms and nutritional requirements of vitamin A. However, there is still a scarcity of information concerning its mode of action in the body, particularly regarding carotenoid conversion to vitamin A and its absorption, transport, storage and association with disease. As recently as twenty years ago, fish liver oils and alfalfa meals were the major sources for vitamin A supplementation. These natural concentrated sources varied in potency and activity from one batch to another. Some contained impurities which interfered with assays and contributed to the instability of vitamin A activity.

It has long been known that natural or synthetic oxytocin, whether it be endogenous or exogenous, causes a change in the motility pattern of the female genital tract and the let-down of milk in laboratory and farm animals. The important functions in animal reproduction such as sperm transport in the female tract, ovum transportation and phenomena involved in pregnancy and parturition, are believed to be associated and affected by the motility of the female genital tract. It is therefore clear that in order to have a better understanding, hence subsequent control of these factors, a more detailed knowledge of the nature of spontaneous and hormone-induced patterns of genital tract motility is essential.

Megaloblastic anemia is no longer regarded as an uncommon complication of childbearing. A keen interest in this disorder has developed due to reports of increased incidence in the last decade (Giles and Shuttleworth, 1958; Ainley, 1961). Research has shown that most patients with megaloblastic bone marrow changes have either a low serum concentration of vitamin B12 or a low serum folate(1) activity, or both, which appear to be reasonably well correlated with the megaloblastic bone marrow changes (Lowenstein et al., 1962). [...]