VTechWorks Repository :: Browsing by Author "White, John M."

Browsing by Author "White, John M."

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Chromosome identification and analysis in selected lines of laboratory mice
Schmitt, Athanasia Nancy Panos (Virginia Tech, 1976-06-05)
Chromosome preparations from 102 ICR albino mice were examined using a modified trypsin Giemsa staining technique. The mice were from four lines selected for maximum rate of post-weaning gain (28 generations), one line selected for minimum rate of post-weaning gain (25 generations), and two unselected control lines. Mitotic metaphase chromosome preparations were obtained from bone marrow cells of adult male and female mice. Two similar treatments were utilized in obtaining the chromosome preparations. The first treatment consisted of: 50 minute colchicine pretreatment, 30 minute hypotionic pretreatment, four-glacial acetic acid-methnanol fixation periods, 15 second trypsin period and 15 minute Giemsa staining period. The second treatment varied from the first, basically, in the length of hypotonic pretreatment, and length and number of fixation periods. A mean number of 40 telocentric chromosomes with very similar banding patterns was observed in all lines. Relative chromosome lengths for each chromosome were obtained. The lengths for the various lines, control, high and low, were compared by means of a pooled "t" test. Non-significant a₂ levels were obtained for the pairwise comparisons of the lines. Significant a₂ levels were obtained for the effects of the two treatments, trypsin and no trypsin. Karyotypes for each line were made with no chromosomal abnormalities detected in any of the lines. The selection regime followed has produced significant genetic change in several characteristics of these mice. However, these changes have apparently not been accompanied by observable alterations at the chromosomal level.
Clinical Experiences for Agricultural Teacher Education Programs in North Carolina, South Carolina, and Virginia
Dobbins, Thomas Roy (Virginia Tech, 1999-08-20)
The purpose of this study was to build a task list for the clinical experience program, both early field and student teaching, for the agricultural teacher education programs in North Carolina, South Carolina, and Virginia. The objectives were: (1) compile a list of clinical experiences, both early field and student teaching, that currently are provided in the clinical experiences for students of agricultural education in three-selected teacher education programs, and (2) use an expert panel to determine what should be included in early field experiences and student teaching experiences for students enrolled in the agricultural teacher education program. A modified Delphi technique was used to collect data via three questionnaires. Data were analyzed using mean scores and standard deviations of tasks rated on a five point Likert-type scale. Those tasks that the panelists rated with a standard deviation of less than or equal to one were considered to have met consensus. The population for this study consisted of agriculture teachers, secondary school administrators, agricultural education field staff, and agricultural education teacher educators from North Carolina, South Carolina, and Virginia. Thirty-four Delphi panel members were purposively selected from the population. Thirty-one panel members responded to Round I, 33 panel members responded to Round II, and 29 responded to Round III yielding an overall response rate of 92%. This researcher asked the Delphi panel members to rate each task on a five-point Likert type scale, 1 = strongly disagree, 2 = disagree, 3 = not sure, 4 = agree, and 5 = strongly agree. The study used mean scores and standard deviations to analyze the results. Consensus was met if the standard deviation of a task was equal to or less than one. Rounds I, II, and III resulted in 102 tasks for early field and student teaching experiences that met consensus. Based on the findings, the researcher developed a task list for early field experiences and student teaching experiences to be considered for use by the agricultural education programs in the three cooperating states. The task list developed is a very comprehensive list that relates to every aspect of clinical experiences.
Development of equations to predict dry matter intake of dairy heifers
Quigley, J. D. (Virginia Polytechnic Institute and State University, 1985)
Equations to predict daily dry matter intake (DMI) of individual animals were developed with 118 Holstein heifers fed totally mixed rations (TMR). Animals grouped according to body weight (136, 227, 317 kg) were fed TMR (corn silage, ground hay, high moisture corn, soybean meal) once daily for 28 days. Rations were balanced to mean body weight according to National Research Council (NRC) recommendations for protein, vitamins and minerals, and to 85, 95, 105, and 115% of recommendation for energy. Independent variables were body weight (BWT, kg/day) daily body weight gain (GAIN, kg), environmental temperature (AMBT, °C), ration acid detergent fiber (ADF, percent of dry matter), neutral detergent fiber (NDF, percent of dry matter), net energy for maintenance and gain (NEM, NEG, megacalories), total digestible nutrients (TDN, percent of dry matter), and bulk density (BULK, g/ml as fed). Squared terms, appropriate interaction terms, and metabolic body weight (MBWT, kg^.75) were included in the model. Stepwise regression was utilized to generate two models, simplified and expanded. Simplified model was: DMI (kg/day) = -29.86 + (-.54E-05 * BWT²) + (.157 * MBWT) + (2.090 * GAIN) + (-.118 * GAIN²) + (.730 * TDN) + (-.005 * TDN²) + (-.001 * BWT * GAIN) + (-.019 * TDN * GAIN); n = 4797, r² = .59, s_y.x = 1.18. Expanded model was: DMI (kg/ day) = -1906.91 + (-0.04 * BWT) + (0.37 * MBWT) + (32.36 * ADF) + (2305.51 * NEM) + (-664.06 * NEG) + (-0.08 * AMBT) + (-0.13 * ADFSQ) + (-637.68 * NEMSQ) + (42.31 * NEGSQ) + (-5.35 * BULKSQ) + (0.001 * AMBTSQ) + (-1.56E-04 * BWT * ADF) + (8.873E-05 * BWT * AMBT) + (246.30 * NEM * NEG) + (-21.30 * NEM * ADF) + (7.83 * NEG * ADF) + (0.04 * NEG * AMBT) + (0.01 * GAIN * ADF) + (-0.01 * GAIN * AMBT); n = 4429, r² = .65, s_y.x = 1.09. Predicted intakes by simplified equation agree with those of NRC at TDN recommended by NRC and .7 kg/day. Computerized ration formulation systems were developed using simplified model. Expanded model requires further refinement prior to incorporation into a ration formulation system.
Effect of body condition and ration protein source on performance of high producing cows during early lactation
Seymour, William Matthew (Virginia Tech, 1985-04-05)
Forty-two high producing Holstein cows were paired by body condition and mature equivalent milk production and fed either a high or low energy complete ration ad libitum during the last 16-20 weeks of lactation. Cows fed the high energy ration ate more feed, produced more milk and gained more body condition than cows fed the low energy ration. Cows were fed to maintain condition during the dry period. During weeks 3-15 of the next lactation, half the cows in each condition group (fat or thin) were fed a mixed ration with soybean meal (SBM) as the major protein source. The remaining cows were fed a ration with dried brewers grains (DBG) as the main protein source.
Effect of immunoglobulins on early bovine embryo development in vitro
Sedano, Rodolfo Canseco (Virginia Tech, 1985-11-05)
Bovine morulae (day 6: n=257) were obtained to evaluate the [effect of immunoglobulins (Ig) on early bovine embryo development in vitro. Fifty-four cows superovulations were conducted in 36 cows with follicle stimulating hormone. Embryos were collected by non-surgical procedures and morphologically evaluated and randomly assigned to culture. Embryos were cultured in Ham's F-10 containing 10% (6.4 mg/ml) steer serum (SS), 1% (.64 mg/ml) bovine gamma . globulins (GG), 1% (.64 mg/ml) bovine IgG, 1% (.64 mg/ml) bovine 1gM, 10% SS plus 1% GG, 10% SS plus 1% 1gG, or 10% SS plus 1% 1gM. Embryos were cultured to the hatched blastocyst stage or degeneration and evaluated at 12 h intervals.
The Effect of Poly-L-Lysine Concentration, Molecular Weight, and Encapsulation Temperature on Microencapsulated Bovine Spermatozoa
Fultz, Stanley Wakefield (Virginia Tech, 1984-12-15)
A series of in vitro studies were conducted to evaluate the effect of poly-l-lysine concentration, molecular weight, and encapsulation temperature on the post encapsulation survivability of spermatozoa. Viability of spermatozoa encapsulated at 2012 C using four poly-l-lysine concentrations (.05%, .15%, .25%, and .35%) did not differ over the 8 h incubation period. However, the viability of each of the four treatments was lower than that of the unencapsulated control (p<.05 and p<.01; percentage motility and percentage intact acrosomes, respectively), indicating spermatozoal damage occurred during the encapsulation process. Capsule wall thickness and integrity for the .15%, .25%, and .35% concentrations were greater (p<.Ol) than that of the .05% capsules.
The effects of a dairy cow body condition scoring system on selected production and metabolic parameters
Wildman, Edward E. (Virginia Polytechnic Institute and State University, 1979)
A dairy cow body condition scoring system was devised by the author as a practical means of determining the body condition, or fitness pertaining to the degree of body fat of dairy cows at any point during the lactation cycle. The factors considered were the thoracic and lumbar regions of the vertebral column (chine, loin and rump), spinous processes (loin), anterior coccygeal vertebrae (tailhead), tuber sacrale (hooks), and tuber ishii (pin bones). All factors in the body condition scoring system must be considered while appraising each cow. Each cow was scored on a 1 to 5 scale with 1 indicating severe undercondition and 5 indicating severe overcondition. During an 18-month period, 28 cows in each of 29 Virginia dairy herds were used for obtaining body condition scores, body weight, frame size measurements and blood samples. Herds were chosen according to rolling herd milk production average and cows were chosen at random from within five Estimated Relative Producing Ability groupings to insure a representative sample of herds across and levels of production in Virginia and of cows within each herd. Herds were sampled at 3-month intervals and complete Dairy Herd Improvement Association records were obtained for each cow in each herd. The relationships of dairy cow body weight, frame size measurements, milk production and related parameters, and blood profiles to the body condition scoring system were determined. Body condition using this method was found to be independent of frame size and only moderately correlated with body weight, the number of intercostal spaces and the ratio of body weight to wither height. Body condition was found to be relatively low during early lactation and to increase through late lactation and remain constant during the dry period. Dairy cows of greatest milk production efficiency did not increase significantly in body condition throughout lactation, had fewer days open, but had less persistency of lactation. Dairy cows that increase significantly in body condition throughout lactation were less efficient milk producers, had a greater number of days open, had relatively high body condition scores in late lactation, but had greater persistency of lactation. Blood parameters, although statistically significant in many cases, were found to be of little or no practical value when compared between body condition, stage of lactation, and dairy merit groupings. The dairy cow body condition scoring system is a practical means of quantitating body condition of dairy cows.
Effects of herd mean and standard deviation on cow indexes for milk , and adjustments of cow indexes for these effects
Lofgren, Donna Lee (Virginia Polytechnic Institute and State University, 1984)
Lactation records of cows born since 1964 were used to compute Cow Indexes (CI) for 581,519 Holsteins and 352,758 Jerseys. CI were used to predict Modified Contemporary Deviations (MCD) of daughters at three levels each of herd mean (µ) and standard deviation (σ), and regressions were compared to expected values. For Holsteins, regressions were greater than expected in herds with average µ or high σ, suggesting that heritability (h²) should be higher for cows in those herds. Heritability estimates agreed with observed regressions for herd σ (h2 of .178, .193, and . 206 as herd σ increased) but not for herd µ (h² of . 222, .163, and .206). For Jerseys, regression results indicated that h² should increase with herd µ, but there was no trend for herd σ. Heritability estimates agreed with the observed regressions for µ (h² of .246, .291, and .331) but not for σ, as h² increased substantially ( .254, .293, and .371) as herd σ increased. Eight adjustments were made for CI: two varied h² to adjust for genetic effects, two adjusted MCD for environmental effects, and four were combinations of these. For Holsteins, regressions of daughter MCD on darn CI were greater than expected for all CI, but regressions of son MCD on darn CI were less than expected. Rankings of CI, based on R² , differed considerably for the three groups examined (all daughters, daughters of elite cows, and sons). For Jerseys, CI of elite darns predicted offspring MCD as expected, but for several CI, regressions for all daughters were less than expected. There were smaller differences in rankings of CI than for Holsteins. Under the assumption that large true breed differences are unlikely, the best CI for both breeds had MCD standardized to a common variance, with h² of .20. This was nearly optimal for Jersey groups, although less than optimal for Holsteins. This CI adjusted for environmental effects of herd a, ignoring differences in genetic variation. It decreased differences among CI for cows in high variance herds, and increased differences in low variance herds.
An Evaluation of Past Performance of the Two-Year Agricultural Technology Program at Virginia Tech as Perceived by Program Graduates
Kantrovich, Adam Joseph (Virginia Tech, 2000-04-20)
The review of the literature reveals the historical nature of Vocational Education programs and how they relate to the importance of Virginia Tech's two-year post-secondary Agricultural Technology Program. The literature review also provides a historical review of information regarding Virginia Tech's Agricultural Technology program, brief histories of other post-secondary land-grant two-year agricultural programs, vocational education philosophers, and two-year program evaluations. The purpose of this study was to perform an evaluation of past performance of the two-year Agricultural Technology Program at Virginia Tech as perceived by the two-year program graduates. The study focused on two points, a) the graduate's opinions with regards toward the improvement of the program on behalf of the students, and b) the strength and weaknesses of the program in order to determine what the program has accomplished and where it should be headed. Five research questions guided this study: 1. How pleased were the graduates with the education they received through the Agricultural Technology Program? 2. What is the salary range of the graduate's first job after graduation and what is their present salary range? 3. What were the strengths and weaknesses of the program as perceived from the graduates? 4. What are the Agricultural Technology graduates current occupations? 5.What recommendations do the graduates have for the improvement of the Agricultural Technology Program? A survey instrument was used as the research method for the collection of the data. A pilot study was performed to test the survey instrument. Three rounds of survey instruments were sent to increase the possible response rate. A non-respondents study was performed to determine if there was a difference between the respondents and non-respondents of the survey instrument. Frequencies, mean, median, mode, and standard deviation were used in the analysis of the data. The population consists of all of those that graduated from the two-year Agricultural Technology Program at Virginia Polytechnic Institute and State University from the date of the programs first graduation class (1989) to the fall semester of 1998. Because there was such a small number of subjects within the population, to prevent sampling error, and to be able to prevent any deviation of assumptions between the sample and the population the whole population was mailed an evaluation instrument. All three of the mailings yielded a total 215 received survey instruments for a 62% response rate from an N of 343. This left a total of 128 or 37% non-respondents. A reliability test was run in SPSS using the Cronbach Alpha method, also know as Alpha coefficient, the Standard Item Alpha = .7661. The major conclusions of the study were that the Agricultural Technology Program graduates were pleased with the overall education that was received at Virginia Tech, the mean salary for the graduates first job was between $18,000 and $23,999, the mean of the graduates current job is between $24,000 and $29,999, the major strengths to the program were the mandatory internship requirement, the hands-on courses, and the advisors for the program, the weaknesses of the program are issues with the transferability of credit hours to the four-year program, additional computer and technology courses and information are needed, and a lack of available elective course offerings. Just over 78% of the program graduates are employed within the field of agriculture and 16% have gone back to farm ownership or to work on the family farm. Some of the major recommendations that were made by the program graduates were to offer additional courses and options, add more emphasis to computers and technology, additional job placement services, and to allow students to take more four-year courses. Based on the findings recommendations were made about further studies for the addition of courses, faculty, program options, more emphasis of technology in courses, curriculum development, job placement, and credit hour transferability. Specific recommendations were made for an external review to be performed of the Agricultural Technology Program, a formal review of curriculum, additional courses in computers and technology, and further research to be performed with regards to policy change in transferability of credit hours to the four-year program, addition of courses offered as electives, and for students to take courses provided by the four-year program.
Genetic and phenotypic relationships among fifteen measures of reproduction in dairy cattle
Meland, Ole Mervin (Virginia Polytechnic Institute and State University, 1984)
Reproductive data from 30 research herds were on 31,132 breeding periods of 11,347 dairy cows. Cows were sired by 1,101 sires and had 66,184 services to 1,320 service sires. Several measures of reproductive pe.rformance were calculated. These included conception rate, number of services, service period length, days open, age at first breeding, calving interval, days between services, and return to estrus lag. First, second and third service period were each analyzed separately, while fourth and later service periods were pooled. Heritability was estimated using the sire component of variance and the estimate of the total variance derived from MIVQUEO and maximum likelihood analyses. The data set was restricted to daughters of sires used in multiple herds. Heritability estimates were less than .07 for all traits in the heifer service period except age at first breeding (.2 by maximum likelihood and .13 by MIVQUEO). Similarly, with the exception of conception rate, none of the measures of reproduction had heritabilities greater than .05 for all three remaining service period groups. Conception rate measured as a trait of the male (service sire) ranged from .08 to .135 for second and third service periods. Conception rate as female trait (sire) had heritabilities ranging from .09 to .249 for second and third service periods. Low heritability estimates obtained in this and other studies suggest that large progeny or service sire groups will be necessary to identify the small genetic differences between bulls. Many genetic and phenotypic correlations were forced positive due to a part-whole relationship or due to the fact they were simply different bounds for the same measure. A few correlations were in the range from .50 to .90, but many were not significantly different from zero due to large approximate standard errors. Repeatabilities based upon pairwise comparisons were in the range from 0 to .13. Repeatabilities for the reproductive performance of virgin heifers with first parity ranged from .01 to .06 and were generally smaller than later parities. Repeatabilities based upon repeated measures on the same cow ranged from 0 to .12. Predicted Differences for female (sire) and male (service sire) reproduction were calculated by Best Linear Unbiased Prediction. This analysis included 207 bulls which were in the data both as sire and service sire. Correlations between proofs for male and female reproduction ranged from -.13 to .13. These results suggest limited genetic relationships between male and female fertility.
History of the Virginia FFA Association
Bryant, Bradley Wayne (Virginia Tech, 2001-03-22)
Part of this research focused on the predecessors of the FFA by outlining the history and purposes of agricultural organizations formed since the late 1700s. The past two centuries of American agricultural history is rich with efforts to educate and improve agricultural practices through organized groups of farmers and other rural leaders. Early in the development of agricultural societies, experimentation and successful practices were shared with others in the local organization and works were often published in journals or newspapers for educational and informational purposes. Regular meetings and fellowship were also a major focus of the early groups. The national organizations that formed later such as the Grange, included the fraternal, social, and educational aspects while maintaining a focus on the economics of farming. The boys’ and girls’ club movement provided opportunities for youth to meet, learn, and participate in agricultural competitions. The center of activities for youth organizations quickly shifted from community groups to agricultural education programs in the public schools. Clubs that formed within agricultural education programs in Virginia soon united to create the Future Farmers of Virginia. The FFV and FFA that followed initiated the use of certain symbols, colors, and ritual ceremonies that can be traced directly to the agricultural societies. This research identified many agricultural societies and youth clubs that had a profound influence on the development of the National FFA Organization. The major purpose of this study was to describe the establishment of the Future Farmers of American and to document the accomplishments of Virginia FFA members at the state and national levels. The objectives of the study were: To describe the historical events and circumstances that led to the establishment of the Future Farmers of Virginia and the Future Farmers of America, To document Virginia FFA history by recording achievements of members and chapters at the state level, To document the achievements of Virginia FFA members and chapters at the national level, and To provide a history of the Virginia FFA Association from 1925 to the present. The Virginia FFA Association is rich with historical information that ranges from the formation of the Future Farmers of Virginia in 1925, the forming of a national organization in 1928, and 75 years of accomplishments by Virginia FFA members.
An investigation into hormonal regulation of ovine mammary gland growth during pregnancy
Smith, James Joseph (Virginia Tech, 1985-05-05)
Prepartum, multiparous ewes were randomly assigned to experimental groups and sacrificed at 50(n=5), SO(n=4),115(n=5), and 140(n=4) days of gestation. Serum harvested the week prior to slaughter was assayed for progesterone (PG), prolactin (PRL) and growth hormone (GH) concentrations. Mammary tissue obtained at slaughter was assayed for receptor concentrations of progesterone (PGr), prolactin (PRLr) and insulin (Ir). Quantitative biochemical, histological and autoradiographical analyses were used to measure mammary gland growth and indicated no significant glandular growth occurs prior to 8O days of gestation. However, a major phase of parenchymal growth occurred between 8O and 115 days which coincided with significant increases in PG, PGr and PRLr concentrations. Parenchymal growth continued further into late pregnancy. GH and Ir concentrations did not change significantly during pregnancy and were not strongly correlated to growth measurements. These results suggest that mammary gland growth is receptor-mediated and direct or indirect regulation of PGr and PRLr is primarily responsible for the observed growth phenomenon.
Line characterization and evaluation of genetic parameters of serum cholesterol levels, activity, feed intake, growth and body moisture in selected and unselected lines of laboratory mice
Dunnington, E. Ann (Virginia Tech, 1975-05-05)
Feed intake, growth, efficiency, and serum cholesterol levels (SCL) were recorded for 102 male mice, and voluntary physical activity and SCL were recorded for 113 male mice from lines selected for 22 generations for maximum 21- to 42-day gain (H), minimum 21- to 42-day gain (L), and a random-bred control (C). Heritability (h²), phenotypic and genetic correlations of SCL, activity, growth, and body moisture content were estimated for 466 sire-son pairs of mice from an unselected line. Blood samples were obtained by sinus orbital bleeding at 35 and 70 days of age in the line characterization study and at 62 days of age in the genetic parameters study and were analyzed for SCL by gas chromatography. Voluntary physical activity was recorded as revolutions of an exercise wheel every sixth day from 21 to 70 days of age in the line characterization study and at 28, 49, and 70 days of age in the genetic parameters study. Feed intake (of an 11% fat, 9% fat, and 4-1/2% fat diet) was recorded for several days each week and extrapolated to obtain weekly intake data. A least-squares analysis of variance from a model including lines, diets, and line x diet interactions indicated highly significant differences in the main effects but few significant interactions. Total SCL, growth, and efficiency were higher, and intake lower in mice on the higher fat diet. SCL (mg/100 ml) at 10 weeks of age was 220.3, 178.1, and 180.4 for animals fed an 11% fat diet and 143.3, 124.1, and 132.2 for animals fed a 4.5% fat diet. Activity scores (revolutions) for the H, C, and L lines were 79234, 107987, and 124409. Activity generally increased in all lines from 21 to 56 days of age, then declined slightly. Heritability estimates of SCL and body moisture 2 content were .31 ± .07 and .20 ± .11, and h² estimates for activity ranged from .27 ± .14 to .54 ± .12. Negative genetic correlations occurred between body moisture content and SCL and between body moisture content and weight gains.
The nature of serum agglutination of bovine spermatozoa: a proposed mode of action and its metabolic effects
Chandler, John Edward (Virginia Tech, 1976-11-01)
Introduction: Numerous past reports have mentioned or have been totally concerned with the significance of spermatozoan agglutination following treatment with blood sera, female genital fluids and other biological and synthetic media. Since semen is a colloid (undissolved particles suspended in a suitable medium such as gas, liquid, solid), spermatozoan agglutination should be at least partially definable by physical chemical measurements and should thereby be predicted and controlled...
Selection for serum cholesterol, voluntary physical activity, 56- day body weight and feed intake in albino mice
Dunnington, E. Ann (Virginia Tech, 1978-01-15)
A short-term selection experiment was conducted with ICR albino mice produced by the reciprocal crossing of two lines of unselected animals which had been random-bred for 28 generations. Lines were developed by selecting for maximum and minimum serum cholesterol (SC) (lines CH and CL), voluntary physical activity (lines AH and AL), 56-day body weight (lines WH and WL) and feed intake (lines IH and IL). An unselected, random-bred control line was maintained with each pair of divergent selected lines (CC, AC, NC and IC, respectively). In the lines selected for SC, physical activity and 56-day body weight, selection was based on individual performance. Twenty-five paired matings plus five extra paired matings were used to perpetuate the lines each generation for five generations. The feed intake lines were perpetuated by within-sex, full-sib family selection with 30 paired matings per generation for five generations.
Validation of the probability of the adoption of change model: an exploratory analysis
Jackman, William Jay (Virginia Tech, 1991-11-05)
The Probability of the Adoption of Change (PAC) model (Creamer & Creamer, 1986a, 1986b, 1988, 1989, 1990; Creamer, Creamer, & Ford, 1991) is a planned change model consisting of nine constructs postulated to influence the success of planned change projects. The constructs in the model include circumstances, value compatibility, idea comprehensibility, practicality, superintendency, championship, advantage probability, strategies, and opposition. The PAC model was tested in the context of curriculum revitalization in undergraduate agriculture and life sciences programs. Faculty and administrators from colleges and departments of agriculture and life sciences throughout the United States responded to survey items written to measure the relationship of the PAC model constructs with the success of curriculum revita1ization projects with which they, the respondents, had been involved. Participants also responded to items written to assess their perceptions of the success of the projects.

Browsing by Author "White, John M."

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