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This dissertation research contained three studies. The first two studies were conducted to investigate the ability of ewes to rebreed while lactating during seasonal anestrus. Breeds studied included the Virginia Tech Out-of-season (OOS) Line, which is a wool line genetically selected to lamb in the fall, and the St. Croix, a hair breed of tropical origin thought to be lowly seasonal. When January-lambing ewes were exposed to rams while lactating in April, significantly more OOS than St. Croix ewes were marked by rams in the first 21 d and total 39 d of ram exposure (58.3 vs. 8.7%, P = 0.0003 and 95.8 vs. 43.5%, P < 0.0001). Percentages of ewes diagnosed pregnant (53.2%) and percentages of ewes lambing (41.3%) were not different between breeds. When March-lambing OOS ewes were exposed to rams while lactating in May, 52.9% of ewes were marked though only 20% of ewes exposed to rams gave birth to viable lambs. Both OOS and St. Croix ewes appear to be well suited to accelerated production systems involving 7 to 8 mo lambing intervals. However, reduction of lambing intervals to 6 to 7 mo appeared to have detrimental effects on fetal survival in OOS ewes. In a third study, alterations in endocrine profiles associated with differing degrees of hypothalamic sensitivity to estradiol-negative feedback and changing daylength in OOS, St. Croix, and Suffolk ewes in the absence of rams were investigated for 1 yr. The results show for the first time that based on progesterone profiles from intact ewes, St. Croix ewes do not have shorter anestrous periods than ewes of wool breeds, as previously thought. Based on luteinizing hormone profiles from ovariectomized ewes treated with estradiol implants, the duration of luteinizing hormone inhibition was shorter in OOS than Suffolk ewes (68 vs. 170.2 d, P = 0.02), but was not different from that found in St. Croix ewes (124.8 d). Specific roles for thyroxine and prolactin in timing the breeding season could not be assigned. This study was the first known use of the ovariectomized, estradiol-implanted ewe model to compare degree of reproductive seasonality in different breeds. / Ph. D.

Many factors influence male fertility, and conventional fertility evaluations are not able to reliably identify sub-fertile animals. The overall goal of this work was to explore the expression of phosphatidylserine (PS) on bovine sperm and investigate what factors may impact it, as previous research demonstrated that phosphatidylserine (PS) plays a role in murine fertilization. Despite conventionally being an apoptotic marker, it is present on viable and fertilization-competent murine sperm, however, less is known of the possible role of PS in bovine fertilization. In experiment 1, viable bovine sperm cells expressing PS were identified and PS levels in fresh and frozen semen were compared. Phosphatidylserine levels in frozen samples were significantly less than in fresh samples. We conclude that the cryopreservation process has an impact on PS expression in sperm by altering the proportion of sperm cells which are capable of fertilization. Experiment 2 examined PS levels in bulls with varying fertility levels based on sire conception rate (SCR). There was no difference in PS levels between high and low fertility bulls. There was a significant difference in PS levels of uncapacitated samples and those capacitated for one hour. These results warrant further investigation into the role of phosphatidylserine in bovine fertilization. / Master of Science / Improving the fertility of cattle is incredibly important to meet ever-growing consumer demands for animal protein. Researchers and producers can utilize a variety of reproductive technologies to improve their herds' reproductive efficiency. Phosphatidylserine (PS) is a glycerophospholipid which makes up a part of all cellular plasma membranes. Typically, it is used as a marker for cell death or apoptosis, however, some cells expose it on their surface temporarily while still viable, including sperm. Phosphatidylserine was found to be exposed on sperm from mice that were still viable and able to fertilize oocytes. Following that, the expression of PS in bovine sperm was investigated. Using bulls as a model, fresh semen was collected and analyzed for the level of PS expression then frozen and reanalyzed. We saw that there was a significant decrease in the level of PS expression in sperm that had been previously frozen, possibly due to damage to their membranes during the freezing process. Frozen semen from beef bulls with either high or low fertility was also analyzed. No difference was observed between bulls with varying levels of fertility. Addressing fertility issues in bulls is a complicated and multi-faceted issue which requires the use of many technologies and fertility markers. Further developing the knowledge of PS exposure in bulls and its relation to fertility and fertilization is worthwhile to attempt to improve the reproductive efficiency of cattle herds.

This dissertation consists of three chapters on development economics. The first two chapters are in the area of international macroeconomics. The third chapter is in an area that is the intersection of macroeconomics and population economics. The first chapter studies currency substitution in an environment where agents' inflation tax evasive demand for foreign money is balanced by the concern for the possibility that the government may impose economy-wide capital controls under which foreign currency transactions are costly. We contrast implications of constant beliefs regarding capital controls with those obtained under endogenous beliefs. With endogenous beliefs, agents expect a greater likelihood of capital controls as economy-wide currency substitution rises. Our results show a persistent demand for foreign money under endogenous beliefs despite efforts by the government to reduce inflation. The second chapter is a theoretical study of currency substitution in an overlapping-generations economy. We focus on the role of beliefs in determining the relative demands for domestic and foreign money. Domestic money suffers from a lack of confidence leading agents to demand foreign money as an alternate store-of-value. We study equilibria in which the level of confidence in domestic money evolves as a function of expected future aggregate domestic money demand: agents increase their demand for domestic money only if aggregate economy-wide real domestic money demand is expected to rise. The third chapter is a study of intertemporal substitution and fertility dynamics. The demographic experience of Iran after the revolution poses an interesting puzzle. A brief increase in period fertility after the 1979 revolution interrupted a trend of decline that had started in the 1950s. The rise in fertility, however, appears to have lasted only a few years: in the late 1980s fertility decline resumed its course at an even faster pace. We present evidence that suggests that the changes in Iranian fertility since the revolution were in part a birth timing phenomenon. The revolution may well have been a transient economic shock which temporarily depressed the relative "price" of children and caused adjustment in fertility patterns which, at least in an ex post sense, is suggestive of intertemporal substitution. / Ph. D.

The objectives of this study were to determine if fixed-timed artificial insemination (FTAI) at two different times, 0 or 24 h after GnRH administration, in a Presynch-Ovsynch protocol influenced the pregnancy rate (PR) when average and high fertility sires were used. Additionally, a second experiment was conducted to determine the effectiveness of CIDR inserts to allow for resynchronization of estrus in cows that did not conceive or maintain the conceptus at FTAI. Lactating Holstein cows (n = 1,457) from two well-managed dairy herds located in the piedmont region of North Carolina were utilized for 12 mo. First artificial insemination (AI) PR differed for fertility group and was 24.1 and 29.2% for average and high fertility group, respectively. Timing of AI did not influence first AI PR and there was no interaction of fertility group and timing of AI. Cows that received a CIDR insert were detected more frequently in estrus during a 4 d period, d 21 to 24, than control cows, 92.5 and 62.0%, respectively. However, the CIDR insert did not increase the detection of estrus compared to control cows over a normal estrus return interval of 7 d, 18 to 24 d after GnRH administration of a FTAI protocol, 28.8 and 34.2% respectively. In conclusion, the use of high fertility sires is a practical recommendation for improving first AI PR and CIDR inserts allowed more cows to be detected in estrus during a shorter interval, but did not increase the estrus detection rate during a normal estrus return interval. / Master of Science

published_or_final_version / Comparative Asian Studies / Master / Master of Arts

John Bongaarts' proximate determinants model of fertility has accounted for over 90 percent of variation in the total fertility rate (TFR) of primarily developing nations and historical populations. Recently, dramatically low fertility rates across the globe have raised questions regarding whether this model could be applied to exclusively below-replacement nations. This study follows Knodel, Chamratrithirong, and Debavalya's 1987 analysis of fertility decline in Thailand by conducting in-depth case studies of the proximate determinants in two low fertility countries over time: South Korea, where fertility is well below the level of replacement, and the United States, where fertility has hovered around replacement level for many years. Then, the fertility-inhibiting effect of the proximate determinants is assessed by comparing the quantitative index representing each determinant measured in the 1960s/1970s with its measurement in the 2000s. For both years, I consider the fertility level that would prevail in the determinant's presence as well as the level that would exist in its absence. Finally, I use each of the indices to calculate the TFR and assess how the strength of the model varies over time in the two countries. Ultimately, results indicate that the proximate determinants model does not offer a clean picture of the fertility level in either South Korea or the United States; when trends uncovered by the case studies are compared to the results of the quantitative analysis, a number of inconsistencies are revealed. This suggests that certain components in the model may need to be respecified for more effective application in low-fertility contexts. However, that is not to say that it offers no insight into fertility at all or that it is no longer a useful tool. On the contrary, it is shown that the proximate determinants model holds a lot of potential for analysis in low-fertility nations. The implications of these results, as well as the need for improvements in international data collection efforts, are also discussed.

Immigrant women are frequently found to have higher fertility relative to women in the majority population. This is often attributed to their socioeconomic characteristics, cultural preferences and patterns of childbearing, and adaptation to the destination context. However, several limitations in the research to date may mask the associations and processes which shape women’s fertility: 1) frequently used indicators are not sensitive to the way in which fertility is shaped by the migration process 2) key proximate determinants of fertility are often not integrated into analyses and 3) non‐migrant women in sending countries are often excluded as a reference for immigrant women’s childbearing behavior. In order to assess how women’s migratory moves and social context affect fertility, I compare the risk of first birth and patterns of contraceptive use at higher‐order parities for non‐migrant, immigrant and native‐born women. For these analyses, I use data from nationally‐representative surveys of reproductive health and family formation from Mexico, the United States, Turkey and Germany. The results from these analyses demonstrate that both foreign‐born Mexican‐ and Turkish‐origin immigrant women experience first birth earlier than non-migrants, second generation immigrants, and native-born women at destination. However the underlying determinants of earlier birth are different for these two groups. There are also differences for second generation women; US-born Mexicans experience first birth at significantly younger ages than whites, whereas age at first birth is very similar for German-born Turkish women and ethnic Germans. Furthermore, patterns of contraceptive use among immigrant women who have at least one child are notably different than patterns observed for non-migrants. US-born women have similar contraceptive use compared to whites, but Mexican-born women are less likely to use permanent and highly effective methods, even after controlling for fertility intentions. Turkish-origin women in Germany exhibit large differences in contraceptive use relative to non-migrant women, particularly the very low reported use of withdrawal. These findings indicate that fertility determinants vary across origin and destination context. The observed differences between Mexican- and Turkish-origin women suggest that distinct processes of migration, socialization, and access to contraception lead to variation in the fertility outcomes for these two groups. / text

Bibliography: leaves 182-210 / vii, 210 leaves : ill ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--Dept. of Obstetrics and Gynaecology, University of Adelaide, 1985