Browsing by Author "Knight, James W."

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    Capturing the multiple landscapes of excellence: perceptions, enactment, and evaluations of teaching practices in four university undergraduate courses
    Berry, Sandra Eileen (Virginia Tech, 1995-04-05)
    This study was directed at capturing the multiple landscapes of undergraduate teaching excellence as viewed by the major stakeholders in college classrooms, the students and their teachers. These landscapes were described and examined with an eye towards gleaning conceptualizations of teaching excellence that could inform the construction of an integrated landscape. Such an integrated landscape could serve as an ideal starting point for the construction of a comprehensive framework for the evaluation and improvement of undergraduate teaching. Participants included four exemplar teachers, acknowledged for undergraduate teaching excellence and volunteer students from each of their classes: introductory sociology, physics, agricultural economics, and composition methods. A model of teaching excellence was constructed from aggregated student conceptualizations of excellent teachers. The model consists of five major dimensions: (1) content, pedagogical, and general knowledge; (2) concern and approachability; (3) enthusiasm; (4) focus on the development of student thought processes and curiosity; and (5) course organization and classroom management. Two recurring themes underlaying students' perspectives of preferred teacher roles are described: (1) a desire for a personal or professional connection with the teacher, and (2) a desire for a teacher who is sensitive to student progress. A comparison is made between teacher and student valuations of 10 dimensions of teaching effectiveness. Teacher rankings of the items varied somewhat from those of students in their classes. Of particular interest, is the higher ranking of a focus on the development of student thought processes and curiosity by two of the teachers. Generally speaking, students placed high value on teachers’ content knowledge and enthusiasm. To capture teachers’ conceptualizations of excellent teaching in practice, researcher observations of the enacted teaching practices of these exemplars were conducted during three time periods throughout the semester. Each teaching practice is described in case format. Cases also include a presentation of student reactions to and evaluation of each teacher’s enacted practice, with particular attention to the teaching dimensions students focused on as they evaluated their teachers. In an effort to connect the results of this study with the existing literature on college teaching, frameworks of teaching excellence were constructed from student-generated and teacher-generated indicators of 10 dimensions of teaching effectiveness gleaned from the research literature. The enacted teaching practice of each of the exemplar teachers was examined using the class-specific framework. The conclusions of this study suggest that a dialogue between the stakeholders in the college classroom must take place in an effort to develop shared conceptions of teaching excellence. Additionally, a closer examination of students’ entering perceptions is in order to ascertain their notions of the purpose of higher education. A comparison of teacher and student perceptions of the intended purposes of higher education could further inform the development of evaluation systems designed to meet the needs of the major stakeholders of the higher education enterprise.
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    Characterization of seasonal reproduction in Virginia Tech Selection Line, St. Croix, and Suffolk ewes
    Jordan, Katherine Mead (Virginia Tech, 2008-08-04)
    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.
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    Control of endometrial secretion in cattle and production of transgenic swine
    Williams, Barry L. (Virginia Tech, 1991)
    Endometrial tissue was collected from cows to determine effects of day of the estrous cycle, location of the ovulatory structure and progesterone (P₄) on endometrial protein secretion. Day 0 (estrus) endometrial tissue released more protein than tissue collected on d 9, 14 or 18. Protein synthesis was greater on d 0 and 18 than d 9 and 14. Endometrium from the uterine horn contralateral to the ovulatory structure synthesized more protein than endometrium ipsilateral to the ovulatory structure. Seventeen protein bands were identified by electrophoresis. Proximity of the ovulatory structure to the uterine horn affected the presence of four proteins. Quantitative release of seven proteins was influenced by day of the estrous cycle and uterine horn. Day of the estrous cycle and location of the ovulatory structure alter endometrial protein secretion and synthetic activity and have effects on individual proteins. A second project utilized 116 gilts and sows to evaluate estrous synchronization/superovulation schemes. Pronuclear microinjection and zygote culture in excised mouse oviducts also was assessed. Synchronization/superovulation procedures were: 1) sows observed for estrous behavior (NAT), 2) cyclic gilts synchronized with altrenogest (ALT) for 15 to 19 d and superovulated with pregnant mares serum gonadotropin (PMSG) and human chronic gonadotropin (hCG; LALT), 3) gilts between 11 and 16 d of the estrous cycle receiving ALT for 5 to 9 d and superovulated (SALT), and 4) precocious ovulation induced with PMSG and hCG (PRE). Zygotes from PRE donors received microinjection of buffer, DNA or no microinjection. Ova were cultured in modified Krebs Ringer Bicarbonate medium (KRB) or mouse oviduct (MO) explants. SALT and PRE had higher ovulation rates than LALT (24.7 ± 2.9, 24.3 ± 1.8 vs 11.6 ± 2.7; x̄ ±SEM). DNA microinjection resulted in a lower (P<.05) cleavage index (CI) than buffer injection or no microinjection (2.16 ± .10 vs 2.80 ± .13 and 2.93 ± .10). MO improved (P<.01) CI over KRB. MO culture for 72 h was the most beneficial system (P<.05; CI 3.25 ± .12). Cl of 2.66 ± .18, 2.79 ± .14 and 2.40 ± .14 were observed from MO for 48, 96 and 120 h, respectively. Transfer of 505 DNA microinjected zygotes into 17 recipients produced seven litters and 50 piglets of which eight were transgenic. Microinjection of DNA, not merely the mechanical procedure, was detrimental to embryo development and culture for 72 h in MO provided optimal CI.
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    Development of an algorithm for the detection of coherency in radar signal waveforms
    Alifrangis, Spyridon Mathew (Virginia Tech, 1989-12-15)
    The estimation of the stability of radar emissions is of considerable interest in the evaluation of radar clutter rejection performance and also for the general knowledge of the waveform required for the design of threat simulators. It should be stressed that for the estimation of clutter rejection capability, it is the stability of the entire waveform that is of general importance, although the stability of parameters such as phase, Pulse Repetition Interval (PRI) and amplitude are typically specified because of the ease in instrumenting the measurement. The parametric estimates are indeed the most useful in describing the characteristics of the waveform but not necessarily for evaluating clutter rejection performance. Two broad categories into which radar emissions can be subdivided are coherent and non-coherent RF. A great deal of confusion often surrounds the use of these terms, especially among those who measure radar emissions rather than those who build the radar sets. For the purposes of this paper, coherence will be defined in terms of the square root of the variance of the first pulse-to-pulse phase difference, Ï (Δθ ). For the case where Ï (Δθ) << 1 radian, the signal will be considered coherent. When the phase is uniformly distributed over 2Ï radians, the signal will be considered nonâ coherent. Since it is likely that, for most practical signals, the signal will be well within one of these two categories, ambiguity will be unlikely. If a radar emission is observed to be coherent, it implies that the radar uses this property for Moving Target Indication (MTI) processing. The performance of the MTI will probably, but not necessarily, depend on the pulse-to-pulse phase stability as the most critical parameter for this type of system. Alternatively, if the radar emission is observed to be non-coherent, it implies that if the radar has an MTI processor, it is likely that it is of the stored reference variety. The performance of the MTI will probably, but again not necessarily, depend on the pulse-to-pulse RF stability as the most critical parameter. The common thread between the two types of systems which indicates clutter rejection performance is the repeatability of adjacent pulse waveforms regardless of phase. This is not to imply that phase is not critical; it is important for determining the type of processor. The difference lies in the fact that for the internally coherent system, the phase information of the coherent reference oscillator is not observable as it is for the extremely coherent system. Hence, the only hint that such an emitter has an MTI processor is contained in the repeatability of adjacent pulse waveforms. This paper addresses the general problems of detecting coherence, estimating MTI performance, and estimating the phase stability, frequency stability and PRI stability using sample data derived from a system based on the IBM-PC. Both the analysis and radar waveform generation systems were implemented in software utilizing Microsoft Fortran and Microsoft C compilers.
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    Dietary Supplementation of Omega-3 Fatty Acids Influences the Equine Maternal Uterine Environment and Embryonic Development
    Jacobs, Robert David (Virginia Tech, 2015-08-03)
    Adverse maternal events around the time of conception influence embryonic development. Thus, aberrations in the uterine environment during early pregnancy, such as those resulting from maternal metabolic or nutritional disruption, can alter gene expression in the developing embryo, leading to variations in its developmental trajectory. Dietary supplementation of long-chain omega-3 polyunsaturated fatty acids (LCPUFA), especially Docosahexaenoic acid (DHA) improves metabolic and reproductive health across species. The objective of this study was to evaluate the effects of peri-conceptual LCPUFA supplementation on endometrial gene expression, uterine health and embryonic gene expression in overweight horses. Thirteen non-lactating light horse mares (mean ± SEM age=13.56±0.11 yr; mean ± SEM BCS=7.07±0.21) were supplemented with concentrate (n=6) or an isocaloric diet containing 0.06 g/kg BW algae-derived omega-3 LCPUFA (n=7) beginning 60 d prior to sample collection. Four consecutive ovulatory cycles were monitored, and uterine endometrial samples were obtained 12 d post-ovulation in cycles 1, 3 and 4. Mares were bred and embryos were flushed 12 d post ovulation 2,3 and 4. Endometrial biopsies obtained from supplemented mares contained increased DHA and omega-3 fatty acids as a percent of total fat (P< 0.05). Endometrial biopsy scores were assigned to endometrial tissues and mares receiving the LCPUFA supplementation had improved scores during the first ovulatory period as compared to control animals (P=0.009). Candidate genes essential to inflammation, prostaglandin synthesis and embryonic development were evaluated by quantitative reverse transcriptase polymerase chain reaction. Data were log transformed and analyzed using the GLM procedure in SAS (v9.3). When examining the data independent of breeding and pregnancy status, endometrial obtained samples from LCPUFA supplemented mares contained reduced IL6 (P= 0.04) and TNFa (P=0.03) mRNA abundance and tended to have increased transcript abundance for Uterocalin (P= 0.09), SAA (P= 0.06) and IL10 (P= 0.06). Endometrial samples from mares fed LCPUFA pregnant in cycle 3 contained greater IL10 (P< 0.001), PTGFS (P=0.05), OXTR (P=0.05) and PLA2G3 mRNA (P= 0.009) and had a tendency for increased SAA (P= 0.08), PTGES (P=0.10) and SLCO2A1 (P=0.10) mRNA abundance. Supplemented mares bred but not pregnant at day 12 in cycle 3 had reduced expression of PTGER2 (P=0.001) and PTGS1 (P= <0.001) in endometrial samples. In embryos obtained post ovulatory cycle 3 and 4, relative transcript abundance of GATA4 and GATA6, markers of endoderm differentiation, along with GATA3 and ELF3, markers of trophectoderm differentiation were greater (P< 0.05) in embryos from LCPUFA supplemented mares (n=5), than controls (n=5). These results indicate that algae-derived LCPUFA supplementation during the peri-conceptual period alters the post-ovulatory uterine environment in the horse by modifying expression of genes related to inflammation and regulating prostaglandin synthesis. Additionally, embryos obtained from supplemented mares displayed differential gene expression related to embryonic lineage specification.
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    Differential effect of melengestrol acetate or progesterone-releasing intravaginal devices on follicular development, progesterone and estradiol-17β concentrations and patterns of luteinizing hormone release during the bovine estrous cycle
    Custer, Edward E. (Virginia Tech, 1992-09-05)
    Two studies were conducted to determine if 7-d MGA or PRID treatment initiated on d 17 of the estrous cycle altered: 1) follicular development, 2) estradiol-17β (E2) and progesterone (P4) concentrations, and 3) patterns of release of luteinizing hormone (LH). In both studies, Angus, Angus x Holstein or Holstein cows 2 to 6 yr of age were randomly assigned to receive either MGA (.5 mg⋅hd⁻¹⋅d⁻¹; n = 23) or PRID (n = 26) for 7 d or to serve as untreated controls (n = 14). Real time, B-mode ultrasound, equipped with a 7.5 mHz linear-array transrectal transducer, was used to conduct daily ovarian scans beginning 3 (Study 1) or 9 d (Study 2) after onset of estrus. Jugular venous blood samples (45 ml) were collected coincident with ovarian scans. In study 2, cows were fitted with indwelling jugular catheters 17 (Control, MGA and PRID), 20 and 23 d (MGA and PRID) after onset of estrus and blood samples were collected at 15-min intervals for 6 h for determination of LH. Interestrus interval was extended (P<.05) for 3 to 5 d in MGA-treated cows exhibiting two or three dominant follicles (classified as MGA-2 and MGA-3, respectively) or PRID-treated cows compared to controls exhibiting two or three dominant follicles during the estrous cycle (control-2 and control-3, respectively). Forty-four percent of MGA-treated cows ovulated the dominant follicle present at the beginning of MGA treatment. In both studies, days from detection of the ovulatory follicle until ovulation were greater (P<.01) in MGA-2 and control-2 cows than control-3, MGA-3 and PRID cows. Diameter of the ovulatory follicle was greater (P<.01) 9 d before estrus and growth rate of the ovulatory follicle was less (P<.02) in MGA-2 and control- 2 cows than control-3, MGA-3 and PRID cows. Serum P4 decreased 3 d earlier (P<.02) during the estrous cycle of MGA-2 and control-2 cows than control-3, MGA-3 and PRID cows. Serum E2 was greater (P<.01) 7 d before estrus in MGA-2 cows than all other treatment groups. Changes in mean and baseline LH concentrations and amplitude of LH pulses on d 17, 20 and 23 after onset of estrus did not differ (P>.10) among treatments. Luteinizing hormone pulse frequency was greater (P<.03) on d-20 after onset of estrus in MGA-2 cows than MGA-3 and PRID cows (4.3 ± .6 vs 2.6 ± .3 and 3.2 ± .4, respectively). In addition, LH pulse frequency did not differ (P>.10) 17 or 23 d after onset of estrus among treatments. In conclusion, MGA treatment extended the dominance phase of development of ovulatory follicles, which resulted in the premature increase in serum E2 and frequency of LH release, whereas the dominant follicle present at the beginning of PRID treatment underwent atresia and another preovulatory follicle developed.
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    Effect of culture conditions, donor source, and injection site on in vitro development of deoxyribonucleic acid microinjected porcine zygotes
    Hajdu, Melissa Anne (Virginia Tech, 1993-05-05)
    A series of experiments were used to evaluate three culture media and two incubation temperatures for their ability to support development of DNA microinjected porcine zygotes. Development in vitro was compared between embryos collected from postpubertal and prepubertal donors and between embryos injected with DNA into the pronucleus and the cytoplasm. Additionally, embryos were analyzed by the polymerase chain reaction (PCR) for the presence of the transgene. One-cell embryos (n=458) were recovered from 36 postpubertal gilts in Experiment 1. Injected and control embryos were cultured in modified media NCSU-23 (mNCSU-23), NCSU-37 (mNCSU-37), and CZB at 37°C and 38.8°C for 7 d. In Experiment 2, one-cell embryos (n=245) were collected from postpubertal (n=15) and prepubertal (n=14) gilts, microinjected with DNA, and cultured in medium mNCSU-23. Superovulated prepubertal gilts (n=22) were flushed in Experiment 3 to yield 343 one-cell embryos which had DNA injected into the cytoplasm or pronucleus. Whole embryos were assessed by PCR. Mean percentages of embryos developing to the expanded or hatched blastocyst stage in mNCSU-23 and mNCSU-37 did not differ from each other (p>.05), but both were greater than the development in CZB (p<.05). Development was greater at 38.8°C (p<.05) than at 37° C. Microinjection of DNA decreased the developmental percentage (p<.05) from that of non-injected controls. Embryos collected from postpubertal gilts had a higher percentage (68.0 ± 3.4) of expanded and hatched blastocysts than embryos from prepubertal donors (29.0 ± 4.6, p<.05). No difference was seen in development between embryos injected in the pronucleus or cytoplasm (p>. 05), but development for both was less than for control embryos (p<.05). Results of PCR analysis indicated that 40% of the embryos developing to the expanded blastocyst stage were positive for the transgene compared to a rate of 60% positive for degenerate embryos. These studies show that DNA microinjected porcine zygotes can be cultured to the expanded blastocyst stage in media mNCSU-23 and mNCSU-37 at 38.8°C. Microinjection of DNA decreases survival of embryos collected from both postpubertal and prepubertal sources, but postpubertal embryos exhibit a higher rate of development. Cytoplasmic injection does not improve embryo viability in vitro above that of pronuclear injection. Finally, whole embryo analysis by PCR is possible, but cross specificity of human Protein C and whey acidic protein (WAP) oligonucleotides for endogenous porcine DNA is strong and creates difficulty in applying PCR analysis to embryos microinjected with WAP-PC transgenes.
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    The Effect of Growth Hormone on Pig Embryo Development in Vitro and an Evaluation of Sperm-Mediated Gene Transfer in the Pig
    Bolling, Laura Clayton (Virginia Tech, 2001-08-20)
    The objective of part one of this study was to determine if the presence of porcine growth hormone (pGH) during oocycte in vitro maturation (IVM) affected subsequent embryo development. Pig cumulus-oocyte complexes (COC) (n=987) were aspirated from slaughterhouse derived ovaries and cultured in BSA-free NCSU 23 medium containing porcine follicular fluid (10% v/v), cysteine (0.1 mg/ml) and hormonal supplements (eCG and hCG, 10 IU/ml each), 10 ng/ml EGF, and with or without pGH (100 ng/ml) for 22 h. The COC were then cultured in the same medium with or without 100 ng/ml pGH, but without hormonal supplements for an additional 22 h. After the completion of maturation culture, cumulus cells were removed and oocytes were co-incubated with frozen-thawed spermatozoa for 8 h. Putative embryos were transferred to NCSU 23 containing 0.4% BSA and cultured for 144 h. Embryo development was assessed on d 6 of culture. The treatment groups were as follows: treatment 1 = control group cultured in IVM medium alone; treatment 2 = 100 ng/ml pGH present of the first 22 h of maturation culture and absent for the second 22 h of maturation culture; treatment 3 = 100 ng/ml pGH absent for the first 22 h of maturation culture, but present for the second 22 h of maturation culture; and treatment 4 = 100 ng/ml pGH present throughout the entire IVM period. Embryos were visually scored for developmental stage at 144 h following fertilization. Each oocyte in the study received a developmental score, based on a scale of 1 = uncleaved, 2 = 2-cell embryo, 3 = 4- to 8-cell embryo, 4 = 9- to 16-cell embryo, 5 = morula, and 6 = blastocyst. The addition of pGH did not affect porcine embryo development as compared to the control (1.57 ± .08, 1.67 ± .08, 1.47 ± .08, and 1.60 ± .08, respectively; P > .10). Replicates within the study differed significantly from each other (P < .01) primarily because the development in replicate 6 was greater than for all others. There was a significant treatment by replicate interaction (P < .05); pGH added during the first 22 h of IVM and pGH added during the second 22 h of IVM in replicate 6 resulted in higher development scores than for controls and continuous pGH addition. However, in replicate 2, continuous pGH resulted in the greatest development. These results suggest that pGH may exert a stimulatory effect on embryo development when present in the IVM media; however, further studies using pGH in IVM culture are necessary. The objectives of the second part of the study were to examine aspects of intracytoplasmic sperm injection (ICSI) using membrane-disrupted spermatozoa, in vitro fertilization (IVF), and sperm-mediated gene transfer in the pig. Porcine oocytes were shipped overnight in maturation media at 39°C in a portable incubator. After 22 h of maturation culture, oocytes were washed in maturation medium without gonadotropins and cultured for an additional 22 h. Cumulus cells were removed and oocytes were divided into four treatment groups: treatment 1 = ICSI using membrane-damaged spermatozoa coincubated with linear green fluorescent protein (GFP) DNA; treatment 2 = ICSI using membrane damaged spermatozoa; treatment 3 = IVF with frozen-thawed spermatozoa coincubated with linear GFP DNA prior to IVF; treatment 4 = IVF with frozen-thawed spermatozoa with no DNA coincubation. Embryos were scored for developmental stage at 144 h following fertilization. Each oocyte in the study received a developmental score, based on a scale of 1 = uncleaved, 2 = 2-cell embryo, 3 = 4-cell embryo, 4 = 5- to 8-cell embryo, 5 = 9- to 16-cell embryo, 6 = morula, and 7 = blastocyst. Although no overall difference in development score was observed following the four different treatments, a treatment difference among cleaved oocytes was observed when comparing only the two ICSI treatments (P < .05); development scores were greater in the ICSI treatment in which sperm were not coincubated with linear GFP DNA prior to injection than when the coincubation was performed (3.76 ± .21 vs. 3.13 ± .17, respectively). No differences in development score were observed in the two IVF treatments. The percentage of embryos expressing the GFP transgene on d 6 of culture following fertilization was 7.3% in the ICSI+GFP group and 0% in all other treatment groups. Thus, sperm-mediated gene transfer using ICSI in the pig has been demonstrated, although success rates were low.
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    Effect of P.G. 600 on the timing of ovulation in gilts treated with Regu-mate
    Horsley, Brandon Ryan (Virginia Tech, 2004-09-14)
    We previously reported that ovulation rate, but not pregnancy rate or litter size at d 30 post-mating, was enhanced by gonadotropin treatment (P.G. 600; Intervet America Inc., Millsboro, DE) in gilts fed a progestin (Regu-mate; Intervet America Inc.) compared with gilts receiving progestin alone. We hypothesized that P.G. 600 altered the timing of ovulation, therefore mating gilts 12 and 24 h after first detection of estrus, as is common in the swine industry, may not have been the most appropriate breeding regimen. The objective of this study was to determine the effect of P.G. 600 on the timing of ovulation in gilts treated with Regu-mate. Randomly cycling, crossbred gilts (5.5 m of age, 117 kg BW, and 14.7 mm BF) were fed a diet containing Regu-mate to provide 15 mg/d for 18 d. Twenty-four h after Regu-mate withdrawal, gilts received i.m. P.G. 600 (n = 25) or saline (n = 25). Gilts were checked for estrus at 8 h intervals. After first detection of estrus, trans-rectal ultrasonography was performed at 8 h intervals to determine the time of ovulation. Gilts were killed 9 to 11 d after the onset of estrus to determine ovulation rate. All gilts displayed estrus by 7 d after treatment with P.G. 600 or saline. Compared with saline, P.G. 600 increased (P = 0.07) ovulation rate (14.8 + 1.1 vs. 17.5 + 1.0, respectively). The intervals from injection-to-estrus (98.4 + 2.7 vs. 110.9 + 2.7 h; P < 0.01) and injection-to-ovulation (128.6 + 2.8 vs. 141.9 + 3.2 h; P < 0.01) were decreased in gilts treated with P.G. 600 compared with gilts treated with saline. Estrus duration (54.4 + 2.3 vs. 53.7 + 2.5 h; P = 0.83), estrus-to-ovulation (30.2 + 2.0 vs. 31.7 + 2.2 h; P = 0.62) and time of ovulation as a percentage of duration of estrus (55.8 + 2.7 vs. 57.5 + 3.0%; P = 0.67) were similar for the P.G. 600 and saline-injected gilts, respectively. In summary, P.G. 600 advanced the onset of estrus and ovulation following termination of Regu-mate treatment and increased ovulation rate. However, treatment of gilts with P.G. 600 had no effect on the timing of ovulation relative to the onset of estrus.
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    Effects of Differences in Dietary Protein and Varying the Interval from Collection of Bovine Embryos to Freezing on Embryo Quality and Viability
    Jousan, Frank Dean (Virginia Tech, 2002-06-14)
    High levels of dietary protein may be detrimental to reproductive performance in cattle. The objective of Exp. 1 was to determine the effects of differences in dietary protein on the production and quality of bovine embryos collected from superovulated donors. Angus cows were randomly assigned to receive one of three experimental diets: a daily ration of 5.7 kg poultry litter, 2.0 kg hay, 3.1 kg corn, and 0.5 kg peanut hulls (LITTER; n = 15); a daily ration of 6.2 kg peanut hulls, 2.2 kg soybean meal, 2.0 kg hay, 0.5 kg corn, and 0.4 kg dicalcium phosphate (SBM; n = 15); or a daily ration of 6.2 kg peanut hulls, 2.0 kg hay, and 3.1 kg corn (CON; n = 19). Diets differed in the amount of total, soluble and degradable protein, but were comparable in energy. After 30 d on the diets, all cows were treated to induce superovulation (28.8 mg FSH/cow, Folltropin) and synchronize estrus. After the detection of estrus each cow was inseminated with semen from one of four Holstein bulls. Embryos were collected 7 d after estrus and evaluated for quality (according to the International Embryo Transfer Society (IETS) standards) and stage of development. Prior to treatment to induce superovulation, blood samples were collected 6 h after feeding. Samples were analyzed to assess dietary effects on plasma urea nitrogen (PUN). Mean levels of PUN were higher (P < 0.01) in cows fed the LITTER or SBM diet (16.3 mg/dL, LITTER; 21.8 mg/dL, SBM; 9.7 mg/dL, CON) than in cows fed the CON diet. Additionally, concentration of PUN was higher in cows fed SBM than in those fed LITTER (P < 0.01). An average of 9.2 transferable embryos (Grade 1, 2 and 3) was collected from each cow and there were no significant differences in the number of transferable embryos collected among groups (9.2, LITTER; 9.3, SBM; 9.1, CON). The number of degenerate embryos or unfertilized ova did not differ among dietary groups. High-protein diets elevated PUN, but did not affect the number or quality of embryos collected from superovulated donors. Cryopreservation of bovine embryos is an important aspect of a successful embryo transfer program. The objective of Exp. 2 was to evaluate the post-thaw viability of bovine embryos collected in Exp. 1 in an in vitro culture system after the embryos had been held at room temperature or refrigerated for 2 to 12 h prior to freezing. Upon embryo recovery, each embryo was randomly assigned to be placed in holding media for 2, 6 or 12 h prior to freezing. During this interval, one-half of the embryos were maintained in a refrigerated environment (5 °C), while the remaining half of the embryos were held at room temperature (20.5 to 22 °C) until freezing. Immediately prior to freezing, embryos were removed from the holding media, transferred to a well containing ethylene glycol (10%) in ovum culture media and loaded individually into a 0.25-mL plastic straw. Straws were then placed in a freezer unit (-6 °C) and seeded to induce ice crystal formation through all columns of the straw. The temperature of the freezer was then decreased 0.6 °C/min to -32 °C, and straws were loaded into canes and plunged into a liquid nitrogen tank (-196 °C). After storage, each straw was exposed to a 5-s air thaw and placed in a water bath at 35 °C for 20 s. Each embryo was then washed to remove excess ethylene glycol prior to in vitro culture. Embryos were individually cultured in Ham's F-10 media supplemented with 4% fetal bovine serum for 72 h. Embryos were evaluated at 24 h intervals throughout the culture period and assigned a stage of development and quality grade score (according to IETS standards). The percentage of embryos that developed to the expanded blastocyst stage and hatched from the zona pellucida was greater for embryos held 2 or 6 h prior to freezing (P < 0.05) than for embryos held for 12 h after collection before being frozen (62.9, 52.0 and 31.1%, respectively). The percentage of embryos that degenerated during in vitro culture was lower for embryos held 2 or 6 h prior to freezing (20.4 and 26.6%; P < 0.05) than for embryos held for 12 h before freezing (50.8%). Furthermore, embryo quality grade was more desirable for embryos held for 2 or 6 h (1.5 and 1.7; P < 0.05) than for those held for 12 h before freezing (2.1). The semen used to inseminate donors and the diet fed to donors for 4 wk prior to embryo collection did not influence the proportion of embryos that hatched or degenerated during the 72 h of in vitro culture. Additionally, holding embryos in a refrigerated environment from the time of collection until freezing did not enhance embryonic development during post-thaw culture. Thus, embryonic viability may be impaired when embryos are held longer than 6 h following embryo recovery before being frozen; however, the storage temperature during the interval from collection to freezing does not influence embryonic development post-thaw.
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    Effects of nursery floor space allowance on growth, physiology, and immunology of replacement gilts
    Callahan, Stuart Russell (Virginia Tech, 2013-10-16)
    In U.S. swine herds, sow removal rates due to death and voluntary and involuntary culling exceed 50% annually. This loss poses an economic problem for producers because the cost of acquiring replacement females is great. Although research has shown that crowding in the nursery has negative impacts on growth, research describing effects of crowding on subsequent reproductive performance and longevity in sows is lacking. This experiment was conducted to determine the impacts of crowding during the nursery phase of production on growth, physiology, and immunology in replacement gilts. Gilts (22.3 ± 3.2 d of age and 5.6 ± 0.6 kg BW) were subjected to floor space allocations of 0.15, 0.19, or 0.27 m2/pig during a 7-wk nursery period. Floor space allocations were achieved by altering the number of pigs per pen (14, 11, and 8 gilts/pen, respectively). As was expected, reduced floor space allowance in the nursery negatively affected growth performance although there was inconclusive physiological and immunological evidence to suggest that pigs were experiencing highly stressful conditions. Although feed intake was not measured, changes in blood counts and blood chemistry for gilts allowed reduced floor space were similar to other studies that reported negative effects of crowding on feed consumption. Further study of the gilts involved in this study will aim to determine if there are any links between the effects of crowding during the nursery and subsequent reproductive performance and longevity in the breeding herd.
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    Effects of prenatal androgen exposure on postnatal growth, estrous cyclicity and behavior in female beef cattle
    McFadden, Michael Patrick (Virginia Tech, 1988-03-15)
    This study assessed the effects of prenatal androgen exposure during three periods, of gestation on the external genitalia, estrous cyclicity, postnatal growth, social dominance and sexual behavior of female beef cattle. Pregnant cows received 17a methyl-testosterone (250 mg/d, sq) on d 40 to 100 (group 1), 70 to 130 (group 2) or 100 to 160 (group 3) of gestation. Control cows (group 0) received no treatment. Group 1 females exhibited completely masculinized external. genitalia. No vulval opening was present and the ano-genital distance (A-g) was similar to that of control male calves. Group 2 females exhibited small vulval openings and enlarged clitoral structures while group 3 females exhibited normally appearing female external genitalia. Anogenital distances for the heifers in groups 2 and 3 were similar to those of the control heifers. Androgen exposure during the three periods of gestation did not affect age at puberty (P<.80), estrous cycle length (P<.63) or postnatal growth (P<.60) of the heifers. At 9, 16 and 21 mo of age, social dominance values (SDV) were determined for each heifer by 3 min random pair contests for a restricted feed source. The animal with the greatest feed source control time was awarded a win. Social dominance value was calculated as 10 times the number of wins divided by the number of competitions for each animal. Group 3 heifers had significantly greater SDV values than group 1 and 2 females (P<.03). SDV did not differ among groups at 16 mo of age (P<.59). Group 1 females had greater SDV than group 2 females at 21 mo of age (P<:.04). At 9, 16 and 21, mo of age, sexual behavior of the heifers was characterized by exposure of the heifers to a teaser female in estrus. Sexual behavior, as indicated by the number of mounts, head placements and interest time, was lower for group 3 females compared to females in groups 1 and 2 at 9 mo of age (P<.04). There were no treatment differences for any sexual behavior variable at 16 or 21 mo of age. These results indicate that there is little potential for increasing postnatal growth or altering the estrous cyclicity of female cattle by exposure of the fetus to testosterone during the periods of gestation selected in this study. External genitalia of females were masculinized by androgen exposure during d-40 to 100 of gestation. Social dominance values were increased and sexual behavior was reduced in females by exposure to androgen during d 100 to 160 of gestation.
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    Effects of Scrotal Insulation on Spermatozoal Morphology and Chromatin Stability to Acid Denaturation in the Bovine
    Acevedo, Nicole (Virginia Tech, 2001-04-26)
    The sperm chromatin structure assay (SCSA), as developed by Evenson et al.(1980), utilizes flow cytometry to quantify the susceptibility of sperm chromatin to in situ acid denaturation via the metachromatic properties of acridine orange. SCSA is repeatable and has been used to distinguish between fertile and subfertile males in different species; however, it does not permit morphological evaluation of cells. In the present study, the SCSA was modified for the fluorescence/differential interference contrast (DIC) microscope to examine morphology and chromatin stability on the same cell. Semen from six Holstein bulls was collected twice weekly for six weeks. Semen was cryopreserved after collection. A 48-hr scrotal insulation was applied after the first three collections to exert a mild thermal insult to the testes; this induces specific spermatozoal morphological abnormalities to appear in a predictable chronological order, as determined by Vogler et al. (1993). Using DIC optics, sperm head morphology was classified as normal, slightly misshapen, pyriform, severely misshapen, or tailless. Vacuolization in the head region was scored separately as apical, diadem, or random. SCSA and modified-SCSA for fluorescence microscopy were used to assess chromatin instability in the samples. The SCSA parameter of 'cells outside the main population of alpha t' (%COMP alpha t) and the modified-SCSA parameter of '% cells shifted from green' were positively correlated (r=0.84; P<0.01). Both variables were positively correlated with the appearance of tailless, pyriform, severely misshapen, and randomly vacuolated cells (P< 0.01), but not with the appearance of diadems or apical vacuoles. Also, the fluorescence microscope detected a significant shift from green in normally shaped cells appearing in morphologically abnormal ejaculates (P<0.01). These results demonstrate that scrotal insulation-induced morphological abnormalities in spermatozoa signify a perturbation in chromatin structure, and that the chromatin perturbation extends into normally shaped cells in the same ejaculate.
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    Efficacy of Synthetic Gonadotropin Releasing Hormone Analogs for Control of Ovulation During Estrus Synchronization Protocols
    Cline, Mark A. (Virginia Tech, 2002-01-30)
    Two experiments were conducted to determine efficacy of GnRH analogs, Cystorelin (CYS, gonadorelin diacetate tytrahydrate) and Factrel (FAC, gonadorelin hydrochloride), for use in beef timed AI synchronization. In Experiment one 342 beef cows from 7 herds were assigned CYS or FAC treatment as part of the Ovsynch protocol (GnRH d 0 and 9, Lutalyse d 7). Cattle treated with FAC had greater tendency (P=.09) to be pregnant at d 45. One individual herd demonstrated FAC-treated cows had more pregnancies at day 45. In Experiment two, 18 beef cows received either CYS or FAC as part of the Ovsynch protocol, intensive blood samples, from time -30 to 525 min post GnRH, were collected at each GnRH injection. Ultrasounds were conducted daily over the course of the protocol. A treatment by phase interaction (P=.03) was found for the time to maximum LH concentration, where CYS-treated follicular cows had a shorter interval than did FAC treated follicular or luteal cows. The duration of detectable LH response showed a treatment by phase interaction (P = .02) where follicular and luteal CYS-treated cows had shorter interval than follicular or luteal FAC-treated cows. The variables maximum LH concentration, and area under LH curve did not differ. Cows treated with CYS had more (P=.02) non-dominant follicles. In Experiment three, 16 ewes randomly received either CYS, FAT or Fertagyl (FER; gonadorelin diacetaate tytrahydrate), and FAT's induced LH maximum concentration occurred sooner (P=.02) than CYS. We conclude that either product may be used in beef cows without compromising fertility.
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    Enhancing Boar Reproductive Performance for Purposes of Artificial Insemination
    Kozink, Daniel Michael (Virginia Tech, 2002-12-02)
    The objectives were to: 1) determine if im treatments of Lutalyse expedited the training of sexually inexperienced boars for semen collection and increased spermatozoal output, and 2) determine the effects of dietary L-carnitine supplementation on boar libido, semen quality, sperm production, and maintenance of sperm motility during liquid storage. Experiment 1 utilized lean-type, terminal-line boars (National Pig Development, Roanoke Rapids, NC) (n = 40; 177.4 ± 2.4 d of age and 112.8 ± 2.0 kg body weight) that had not previously experienced natural mating. Boars were individually moved twice weekly for 6 weeks (total of 12 training sessions) to a semen collection room equipped with an artificial sow. Upon entering the semen collection room, boars received in treatments of either deionized water (4 mL, n = 10) or Lutalyse at doses of 5 mg (n = 10), 10 mg (n = 10), or 20 mg (n = 10), and subsequently received a libido score of 1 to 5 (1 = no interest in the artificial sow; 5 = mounting the artificial sow and allowing semen collection). The percentages of boars successfully trained for semen collection during the experimental period were similar (P > 0.05) for controls (20%) and boars receiving 5 mg (30%), 10 mg (20%), or 20 mg (10%) of Lutalyse. Average libido score for boars receiving 10 mg Lutalyse (2.35 ± 0.08) was greater (P < 0.05) than for controls (2.14 ± 0.06). Libido score for the 20 mg treatment group were (1.78 ± 0.06) lower (P < 0.05) compared to the other treatment groups. Characteristics of ejaculates (volume, gel weight, sperm concentration, total spermatozoa) from control boars and boars treated with Lutalyse at doses of 5, 10, or 20 mg were similar (P > 0.05). For Exp. 2, the same group of boars was utilized in two similar trials (Trial 1, 1a, 1b: n = 9 for control and L-carnitine-treated boars; Trial 2, 2a, 2b: n = 10 for control and L-carnitine-treated boars). Boars were fed a fortified, corn and soybean meal-based diet at a rate of 2 kg/d. Boars that were randomly selected for L-carnitine treatment received the same diet mixed with L-carnitine to achieve supplementation of 500 mg/d. For 16 wk, semen was collected weekly via the gloved hand method and was analyzed for gel-free volume, gel weight, sperm concentration, sperm per ejaculate, and characteristics of sperm motility. Time to ejaculation (reaction time), duration of ejaculation, and number of false mounts were also recorded for each collection. Trials 1a and 2a were conducted during weeks 16 and 17 for each respective trial. Boars were collected once on 4 consecutive days, allowed 4 d of rest, and then collected again, to estimate daily spermatozoal production. At the end of 16 wk, a semen sample was also processed and extended in Beltsville Thawing Solution (BTS) to achieve a dilution of 3 x 109 spermatozoa/100 mL-dose for Trials 1b and 2b. The extended semen was stored in plastic bottles at 18°C and motility was evaluated daily for 7 d post collection. L-carnitine supplementation for 16 wk had no effects on semen volume, gel weight, total number of sperm cells per ejaculate, reaction time, or sperm motility (P > 0.1). Boars receiving the L-carnitine-supplemented diet displayed an increase in the number of false mounts before ejaculating and an increase in sperm concentration (P < 0.05) in Trial 2. A treatment by week interaction was detected for sperm concentration in Trial 2 (P < 0.005). Increased sperm concentrations in L-carnitine-treated boars were demonstrated after only one week of feeding the respective diets. Given that the production of a mature sperm cell requires 7 to 8 wk in boars, it is therefore difficult to conclude that differences in sperm concentration were due solely to treatment. Daily spermatozoal production was similar between control boars and boars supplemented with L-carnitine (P > 0.1) for both Trials 1a and 2a. L-carnitine supplementation did not affect percent motility in Trials 1b and 2b or sperm progressive motility in Trial 2b during 7 d storage (P > 0.1). A treatment by day interaction was determined for sperm velocity (P < 0.05) in Trial 2b. L-carnitine supplementation decreased mean sperm velocity significantly after 2 d of storage. Overall, L-carnitine had no beneficial effects on boar libido, semen quality, sperm production, or maintenance of sperm motility during liquid storage. However, Lutalyse increased libido scores, but did not affect the number of boars trained for semen collection or number of spermatozoa ejaculated.
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    Equine Trophectoderm Cells and Their Role in Fetal-Maternal Recognition
    Bonometti, Susana (Virginia Tech, 2019-01-18)
    Establishment and maintenance of a successful pregnancy requires signaling from the embryo to the mare, a process known as maternal recognition. Six days after fertilization, the trophectoderm (TE), a placenta precursor is formed. Signals emanating from the TE to the uterine environment are critical to maternal recognition of pregnancy. The identity of factors necessary for this process remain unknown. A novel equine induced trophoblast cell line (iTr) that closely mimics the genotype and phenotype of native equine TE was created. Transcriptome analysis of iTr revealed increased expression of growth factor (GF) receptors for Epidermal GF (EGF), Hepatocyte GF (HGF), Fibroblast GF-2 (FGF-2) and Insulin GF (IGF-1), suggesting these GF may be important targets during TE development in the early embryo. We hypothesized that treatment of iTr cells with these GF would induce changes in cell proliferation and expression of genes likely involved in maternal recognition. The objectives of this experiment were to evaluate the effect of these GFs on iTr mitotic response and regulation of genes involved in steroidogenesis. Equine iTr cells (n = 3) were cultured with 10 ng/mL EGF, HGF, FGF-2 or IGF-1 for 24 hr, with 5-ethynyl-2'-deoxyuridine (EdU) supplementation during the final 2 hr. Subsequently, cells were fixed and EdU positive and total nuclei were enumerated. A parallel plate of iTr cells was treated in a similar manner and lysed for total RNA isolation. Quantitative PCR using gene-specific primers for CYP11A1, PTGS2, PTGES2, and PTGES3 was performed. Data were analyzed by ANOVA with Tukey's post hoc adjustment using the GLM procedure of SAS. Treatment with EGF, FGF-2, HGF, and IGF-1 increased (P < 0.05) iTr proliferation from control levels of 25.33 ± 1.03% to 38.58 ± 1.61%, 45.50 ± 2.94%, and 38.23 ± 2.01% respectively. The 2-ΔΔCT method was used to calculate the fold change (FC) using GAPDH as the reference gene for normalization. Expression of CYP11A2, PTGES2, and PTGES3 was not affected by GF, as measured by qPCR. By contrast, PTGS2 transcript abundance increased (P < 0.05) following FGF-2 (FC = 3.327 ± 0.8291) and HGF (FC = 11.88 ± 4.572) treatment. These results indicate that FGF-2 and HGF may simultaneously induce proliferation and prostaglandin production by TE cells. The combined results of these experiments will improve our understanding of TE morphogenesis and its response to uterine-derived growth factors.
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    Estradiol-17beta-Oxytocin Induced Cervical Dilation in Sheep: Application to Transcervical Embryo
    Wulster, Meghan Carole (Virginia Tech, 1997-07-10)
    Experiments were initiated to determine whether exogenous estradiol-17beta (E2) and oxytocin (OT) can be used to dilate the cervix and improve transcervical embryo transfer (ET) procedures for sheep. However, there was concern that the E2-OT treatment may alter luteal function and that embryo quality would decrease as the superovulatory response to FSH increased. In Exp. 1, 32 ewes were assigned to a 2 x 2 factorial array of treatments. On d 7, ewes received an i.v. injection of either 100 micrograms of E2 in 5 mL of 1:1 ethanol:saline or 5 mL of 1:1 ethanol:saline; 12 h later, ewes received i.v. injection of either 400 USP units of OT or saline. Jugular blood was collected on d 7, 8, 9, 10, 12, 14, 16, and 18. Progesterone concentrations were unaffected by the treatments. Experiment 2 was conducted to determine the dose of pFSH needed to induce approximately six corpora lutea (CL). Ten-day Norgestomet implants inserted between d 8-12 of the estrous cycle were used to synchronize estrus in Hampshire and Hampshire x Dorset ewes (n = 23). Ewes received a total of either 0, 18, 27, or 36 mg of pFSH, which was injected i.m. at -24, -12, 0, 12, 24, and 36 h relative to implant removal. The dose at each respective time was 19.4, 19.4, 16.7, 16.7, 13.9, and 13.9% of the total. Ewes received 400 IU of PMSG i.m. at -24 h. The CL were counted laparoscopically on d 6 (d 0 = estrus). Number of CL increased linearly (P &lt; .01) with dose of pFSH; there were 1.8, 3.6, 6.3, and 11.2 CL/ewe, respectively. Experiment 3 was conducted to determine the effect of the E2-OT treatment, mode of transfer or the interaction of E2-OT treatment x mode of transfer on embryo survival and development. Experiment 3 was conducted over two breeding seasons and across two trials. In the first trial ewes were assigned to one of three randomized treatments. Procedural limitations that were later overcome prevented a true 2 x 2 factorial design; therefore, transcervical transfer without hormonal treatment was excluded in the first trial. In the second trial, ewes were assigned to a 2 x 2 factorial array of treatments. On d 6 of pregnancy, embryos rating a fair or better were transferred into recipients either transcervically or laparoscopically. Recipients were administered either an E2 (d 6) - OT (d 7) treatment or an ethanol:saline-saline treatment following the same protocol as in Exp. 1. Embryos were recovered on d 12 in Trial 1 and d 14 in Trial 2. Embryos were evaluated morphologically for development and ranked on a scale of one to four; one represented no development and four represented development to the morphological stages associated with the day of collection. The treatments did not affect the percentage of embryos recovered after transfer or the percentage of embryos that showed some developed. However, there was an effect of mode of transfer on mean rank of embryo development; embryos transferred laporscopically developed further than embryos transferred transcervically (P &lt; .01). This may have been an artifact of a technician effect between trials. There was an effect of E2-OT treatment on transcervical transfer (P &lt; .01), indicating that it may be detrimental to transfer embryos transcervically without dilating the cervix. In conclusion, the E2-OT treatment did not affect luteal function, and the E2-OT treatment can be used to dilate the cervix and enhance success of transcervical transfer of embryos. A 400 IU priming dose of PMSG and a total dose of 27 mg of pFSH can be used to induce the target number of six CL.
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    Exogenous γ-Glutamyl Cycle Compound Supplementation to In Vitro Maturation Medium and the Effects on Subsequent In Vitro Fertilization and Culture Parameters of Porcine Oocytes and Their Impact on Embryo Viability
    Whitaker, Brian Daniel (Virginia Tech, 2002-06-26)
    High concentrations of intracellular glutathione enhance the in vitro production of porcine embryos. Six experiments were conducted to study the effects of varying concentrations of different supplements to the in vitro maturation (IVM) medium on in vitro fertilization (IVF) and in vitro culture (IVC), and evaluate subsequent embryo viability. In Exp. 1, 2, 3, and 4, porcine oocytes were matured in either 3.3 mM cysteine, 150 μM cysteamine, 3.3 mM cysteine and 150 μM cystemaine; 1.0 mM glycine, 2.5 mM glycine, 5.0 mM glycine; 1.0 mM L-glutamate, 2.5 mM L-glutamate, 5.0 mM L-glutamate; and 3.3 mM L-α-aminobutyrate, 25 μM β-mercaptoethanol, 3.3 mM cysteine and 25 μM β-mercaptoethanol, or 3.3 mM L-α-aminobutyrate and 25 μM β-mercaptoethanol. After IVM (44 h), concentrations of intracellular glutathione (GSH) were determined using a colorimetric assay based on absorbency. The supplements that elicited significantly (P < 0.05) the greatest increase in GSH concentrations were 3.3 mM cysteine, 1.0 mM L-glutamate, 3.3 mM L-α-aminobutyrate, and 3.3 mM L-α-aminobutyrate with 25 25 μM β-mercaptoethanol. In Exp. 5, oocytes matured with 3.3 mM L-α-aminobutyrate and 25 μM β-mercaptoethanol had a significantly less (P < 0.05) occurrence of polyspermy and greater occurrence of MPN formation during IVF compared to the other treatment groups and a significantly greater percentage (P < 0.05) of embryos reaching the 2 cell developmental stage by 48 h post-IVF and blastocyst stage of development by 144 h post-IVF compared to the other treatment groups. In Exp. 6, treatment had no effect on the time of cell death. The times at which embryo mortality was significantly the greatest (P < 0.05) were located within the middle of IVC. The approximate time of the onset of cell death occurred between 24 to 42 h post-IVF with the greatest occurrence around 36 h. These results suggest that supplementing 3.3 mM L-α-aminobutyrate and 25 μM β-mercaptoethanol into the IVM medium 1) increases intracellular GSH concentrations by the end of IVM, 2) decreases the occurrence of polyspermy during IVF, 3) increases the MPN formation during IVF, and 3) increases embryo development parameters during IVC. Supplementation to the maturation media does not have an effect on cell death during embryo development. The onset of cell death appears to occur between 24 to 42 h post-IVF with the greatest occurrence around 36 h post-IVF. In order to increase the success of in vitro derived porcine embryos and offspring, the basic fundamentals of the system need to be fully understood.
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    Growth Performance, Carcass Traits, and Reproductive Characteristics in Boars Fed Diets Supplemented With an Organic Source of Selenium
    Speight, Susan Michelle (Virginia Tech, 2010-08-11)
    The objectives of this study were to assess growth and reproductive performance of boars fed a diet supplemented with organic selenium (Se). Crossbred boars received one of three treatments: I. basal diet with no supplemental Se, II. basal diet supplemented with 0.3 ppm organic Se (Sel-Plex), and, III. basal diet supplemented with 0.3 ppm sodium selenite. Nursery (n = 13 pens/treatment) boar performance was not affected (P > 0.1) by diet and only grow-finish (n = 11 pens/treatment) G:F was greater (P < 0.06) for Sel-Plex (0.378) compared with selenite (0.368) or control (0.363) boars. At 15-mo of age semen was collected from boars (n = 10/treatment) over 5-d. Semen quality declined over time, but the negative impact day had on sperm motility was less pronounced with Sel-Plex boars. Effects of treatment x day were detected for progressively motile (P = 0.02) and rapidly moving (P = 0.03) spermatozoa, sperm path velocity (VAP; P = 0.05), and average velocity (VSL; P = 0.05). At 17-mo of age, semen was collected from boars (n = 10/treatment), extended and stored over 10-d. Although semen quality decreased over time, sperm from Sel-Plex boars resisted the negative effects of day on sperm motility and pH. Effects of treatment x day were detected for percent motile spermatozoa (P < 0.01), static spermatozoa (P < 0.01), VAP (P = 0.06), amplitude of head displacement (ALH; P = 0.02), straightness (P = 0.01), and pH (P < 0.01). At 23-mo of age, semen was collected (day 0) from boars (n = 6/treatment), extended, stored and evaluated at d 1 and 8 using in vitro fertilization. Dietary Se treatment failed to affect (P < 0.05) in vitro fertilizing rates of boars. In summary, dietary supplementation with Sel-Plex enhanced G:F in grow/finish boars. Dietary Sel-Plex supplementation may decrease the effects that stressors, such as intensive semen collection or semen storage, have on boar sperm characteristics such as sperm motility. The mechanisms for these responses remain to be elucidated.