College of Agriculture & Natural Resources
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item ASSESSMENT OF MALE GIANT PANDA SEASONAL REPRODUCTION, SEXUAL MATURITY AND COMPARATIVE SPERM CRYOTOLERANCE(2010) Aitken-Palmer, Copper; Ottinger, Mary Ann; Howard, JoGayle; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The giant panda is unique as one of the most studied endangered species. Interestingly, despite this, little is known about basic male reproductive physiology. Behavioral problems have posed challenges for reproductive success in the captive population, while geographical isolation and habitat fragmentation threaten the wild population. Techniques such as sperm cryopreservation can improve genetic management and reproductive success within captive populations. But without comparative freeze-thawing studies, diverse methods used for cryopreservation result in inconsistent post-thaw quality, potentially compromising sperm quality and fertility for artificial insemination. This, compounded by limited knowledge of male reproductive physiology, has challenged conservation goals for the giant panda. Specific objectives of this study include: 1) assess the influence of season on male giant panda reproduction by determining annual changes in testis size, body size, testosterone production, sperm quality and production, and reproductive behaviors throughout the year; 2) characterize the onset of sexual maturity in the male giant panda by documenting the timing of initial sperm production, increasing testicular size and body weight, rising androgen production and initiation of reproductive behaviors; and 3) identify factors influencing giant panda sperm cryopreservation by comparing the effect of freeze-thawing on sperm motility, acrosomal integrity, forward progressive movement and longevity. Results provide evidence that 1) reproductive seasonality in the male giant panda is more protracted than the female, with coordinated increases in testes size, androgen production, sperm density, and sexual behaviors; thereby maintaining reproductive competence to prepare for, and accommodate, a brief unpredictable female estrus; 2) sexual maturity in the male giant panda is first observed with consistent sperm production at 5.5 yr, then accompanied by increasing body weight, fecal androgen concentrations, and culminating with the onset of reproductive behaviors, such as scent marking between 7.5 - 8.5 yr; and 3) the giant panda spermatozoon has the capacity to withstand cold stress applied by multiple means, specifically after freezing and thawing using a unique field friendly dry shipper approach. These data greatly improve our understanding of male giant panda reproductive physiology, specifically seasonal rhythms, the cascade of changes associated with sexual maturation, and insights into improved comparative approaches for sperm cryopreservation.Item Understanding the Reproductive Biology of the Przewalski's Horse (Equus ferus przewalskii)(2010) Collins, Christina Wynne; Keefer, Carol ` L; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The Przewalski's horse (Equus ferus przewalskii) once roamed the Eurasian Steppe but is now considered Critically Endangered with only 1872 individuals remaining in the world, representing progeny from only 14 founder animals (Lee and Boyd, 2008). Genetic diversity needs to be optimal for long term survival of this species. Unfortunately, increasing genetic diversity of the captive population in North America has been hindered by a decrease in fertility. Therefore, the main focus of this research was to characterize reproductive parameters in Przewalski's horse, including estrus cycle in mares and seminal traits in stallions, and determining whether age or inbreeding had an impact on these traits. A secondary focus was to determine whether hormone manipulation of the estrous cycle in mares could be utilized for the long-term goal of using artificial insemination as a breeding management tool for this species. To facilitate these studies, a technique for palpation of Przewalski's mares was developed; the first application of such a procedure in a wild equid. Subsequently, we were able to describe follicular changes in relation to urinary hormone patterns. Fifty percent of the mares had either irregular or acyclic hormonal and follicular patterns. These patterns were directly correlated with inbreeding which is the first time such a correlation has been described in this species. Estrous manipulation was possible using an injectable biorelease form of the progestagen, altrenogest. In stallions, we developed a reliable method of semen collection for Przewalski's stallions and, as a result, describe seminal traits from 98 semen collections from 14 stallions. Based on these collections, we were able to show that sub-fertility in this population could be due to the low percentage of normal spermatozoa. Based on variable analysis, seminal traits total concentration, volume and morphology showed variable changes through the year. Traits also varied on an individual stallion basis. Together, these studies demonstrated that inbreeding is detrimentally affecting the reproductive fitness of this species and that aggressive management is needed for long term sustainability of the captive population.Item The effect of sperm mobility phenotype on fertility persistence in layer and broiler hens(2008) Baczynski, Kathleen; Estevez, Inmaculada; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Domestic fowl (Gallus gallus domesticus) were studied to identify accurate predictors of potential fertility in two lines of broiler breeder males along with fertility persistency in layer and broiler hens. Sixty-four Hy-Line layer and thirty-seven broiler breeder hens were AI with identical amounts of high or low mobility sperm from FG males. Morphological measurements were taken to determine relationships of these with semen volume, concentration, and mobility. We hypothesized that 1) semen quality would decline as males aged, 2) morphology would be positively correlated with semen quality, and 3) females AI with high mobility sperm would have a longer duration of fertility. Results revealed a significant age*line interaction for semen volume (p=0.0307), sperm concentration (p=0.0003), and sperm mobility (p=0.0405). Morphological measurements were correlated with different semen parameters in both lines. Fertility was positively correlated with semen quality. Sperm mobility influenced fertility in layer hens but not in broiler breeders.Item Effects of Aging and Moderate Calorie Restriction on the Reproductive Axis of the Male Rhesus Macaque (Macaca mulatta)(2007-04-25) Sitzmann, Brandon Dale; Ottinger, Mary Ann; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Calorie restriction (CR) has been established as the only non-genetic method of altering longevity and attenuating biological changes associated with aging. This nutritional paradigm has been effective in nematodes, flies, rodents, dogs and possibly non-human primates. Its long history notwithstanding, little is known regarding the exact mechanism(s) of CR action or its potential impact on the hypothalamic-pituitary-gonadal (HPG) axis. The objectives of this project were to: 1) analyze neuroendocrine changes to the HPG axis that occur with aging and 2) evaluate the effects of moderate CR on reproductive function in male rhesus macaques. Pituitary gene expression profiling, semi-quantitative RT-PCR (sqRT-PCR) and immunohistochemistry showed circadian clock mechanism components present in three age categories of macaques, demonstrated age differences in expression for Per2, indicated differential expression of Per2 and Bmal1 at opposing time points and revealed daily rhythmic expression of REV-ERBα protein. These data indicate the ability of the macaque pituitary to express core-clock genes, their protein products, and to do so in a 24-hour rhythm. Young Adult CON and CR pituitary gene expression profiles detected potential differential expression in <150 probesets. A decline in>TSHR and CGA was detected in CR macaques as measured by sqRT-PCR. Other genes investigated showed no diet-induced changes. Young Adult CON and CR testicular gene expression profiles detected potential differential expression in <300 probesets although mRNA expression was not altered based on sqRT-PCR and real-time RT-PCR. Age-related>and/or diet-induced changes in HSD17β3, INSL3, CSNK1E and CGA were observed in a separate experiment with CGA in Old Adult CR subjects returning to youthful levels. Semen samples were collected from Young Adult CON and CR macaques. Normal spermiogram measures, ZP-binding, AR assay and SCSA® were conducted and indicated no differences between CON and CR-treated animals. Both groups exhibited similar daily testosterone profiles with no differences in mean or maximum levels; however, daily minimum testosterone levels were lower in CON animals. It appears that moderate CR had limited impact on neuroendocrine or reproductive function in male rhesus macaques based on our selected endpoints. Thus, advantageous CR health benefits can be achieved without obvious negative consequences to the HPG axis.Item Effects of Moderate Calorie Restriction on Ovarian Function and Decline in Rhesus Monkeys(2006-04-27) Wu, Julie Mei-Fen; Ottinger, Mary Ann; Animal Sciences; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Calorie restriction (CR) has long been heralded as the only proven nutritional intervention for life extension. Recent data demonstrated that moderate CR also extended reproductive lifespan in female rats. The objectives of this project were to: 1) analyze general hormonal changes that occur with aging and menopause and 2) evaluate the effects (whether beneficial or detrimental) of moderate (30%) CR on ovarian function and decline in rhesus monkeys (Macaca mulatta). Hormone analyses demonstrated elevated FSH and reduced INHB in Old monkeys, prior to menstrual cycle irregularity and alterations in E2 or P4. Our data are the first demonstration of this hormonal event occurring in monkeys. Furthermore, moderate CR did not impair normal ovarian function or aging. Evaluation of three clinically available tests: day 3 FSH, the Clomiphene Citrate Challenge Test (CCCT) and the Exogenous FSH Ovarian Reserve Test (EFORT), demonstrated that CCCT is efficacious in monkeys, especially with the use of E2 and INHB. As such, CCCT is the most cost effective and best predictor of ovarian response. Responses were similar between CON and CR. Oocytes from old short-term CON and CR monkeys were collected and fertilized with spermatozoa collected from normal males. Interestingly, CR appears to prolong ovarian responsiveness to exogenous gonadotropins and improve embryonic development in vitro in old female rhesus monkeys. Microarray analysis of gene expression was conducted in luteinizing granulosa cells. A subset of responsive genes were identified that will require validation by via real time polymerase chain reaction (RT-PCR). These data will provide insight into potential mechanisms of direct action of CR on the ovary. Therefore, the results of this study have provided evidence for the utility of the rhesus monkey as a model for human menopause. Additionally, moderate CR did not impair normal reproductive function or decline. We also confirmed the efficacy of the CCCT in rhesus monkeys and recommend its use as a diagnostic tool. Finally, CR improved ovarian response to exogenous gonadotropins and has beneficial effects on oocyte quality and subsequent embryo development.