• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 467
  • 125
  • 23
  • 5
  • 1
  • 1
  • Tagged with
  • 1665
  • 1665
  • 312
  • 308
  • 200
  • 163
  • 143
  • 139
  • 125
  • 124
  • 112
  • 109
  • 99
  • 92
  • 88
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
471

Development of an Ovine Genome Map with Emphasis on In Situ Hybridization

Heaton, Melanie R. 01 May 1996 (has links)
Livestock genome maps are used to identify economic trait loci and loci proximal to genes affecting economically important traits. This research contributes to the development of the ovine genome map by establishing techniques to physically map large DNA inserts to ovine chromosomes using fluorescent in situ hybridization. Fluorescent in situ hybridization techniques were established using yeast artificial chromosomes as DNA probes. Probes were as large as 1,000,000 kilobases and hybridized to fixed ovine metaphase chromosomes from a callipyge ewe. Three yeast artificial chromosome probes contained a genetic marker for the ovine callipyge gene. Probes were assigned to ovine chromosome pair 18, which was distinguished by a fluorescent R-band pattern. This method verified the location of the marker, which had previously been assigned to chromosome 18 through linkage analysis. This study also determined whether a chromosomal alteration is the cause of the callipyge phenotype, an economically advantageous trait where muscle mass is increased and fat deposition is decreased. A fibroblast cell line was produced from a six-month-old callipyge ewe. Chromosomes were examined using G and R dynamic banding techniques. The ewe had a normal diploid chromosome number of 54, and the karyotype consisted of 3 pairs of submetacentric chromosomes, 23 pairs of acrocentric autosomes, and 2 large acrocentric X chromosomes. G and R banding did not reveal any chromosomal structural abnormalities at the level of resolution (premetaphase) used in this study.
472

Development and Application of a Reverse Genetics System for Zika Virus

Frank, Jordan C. 01 December 2018 (has links)
Zika virus (ZIKV) has emerged in many regions of the world, with infection outcomes spanning from no apparent illness to crippling nervous system disease. ZIKV and its close relatives, West Nile virus, Japanese encephalitis virus, dengue virus, and yellow fever virus are primarily transmitted by mosquitoes. Three ZIKVs were selected: MR-766 (Uganda, 1947), P6-740 (Malaysia, 1966), and PRVABC-59 (Puerto Rico, 2015), whose place of origin and time of isolation differ substantially. Stable, complementary DNA (cDNA) copies of the three ZIKV RNA genomes were cloned to examine the significance of viral and host genetic variations in directing ZIKV infection outcomes. Using a new toolbox for ZIKV genome engineering and protein analysis, combined with various cell culture and mouse infection model systems, the following were determined: (1) Genome-wide landscape of viral gene products and their related species, with several immuno-reactive gene products identified in the case of all three cloned ZIKVs. (2) Viral replicability in cultured cells, varied significantly depending on the virus strain and host cell type, with one cow cell line being resistant to ZIKV infection. (3) Virus induced neurological disease in mice, differed dramatically depending on the virus dose and strain, mouse age and strain, route of infection, and presence or absence of immune system components. Overall, the findings demonstrate the impact of the viral and host genetic backgrounds on the ability of ZIKV to replicate and cause disease. The ZIKV strain-specific characterizations and molecular instruments described will provide multiple avenues for developing and testing medical countermeasures.
473

The Effect of DDT Residue on the Composition and Digestibility of Alfalfa Hay

Myint, Than 01 May 1948 (has links)
DDT (2,2 bis (p-chlorophenyl) 1,1,1,-trichloroethane) was first synthesized in 1874 by Seidler in Switzerland, however, its effectiveness as an insecticide was not known until about 1942. The active principle was first known as G.H.B. (Gesarol-Neccid Base): but in 1943 DDT was suggested as an abbreviation for Dichlore Diphenyl Trichloroethane (Kaaegie, 1946). In fact DDT, as a powerful insecticide is one of the developments made during World War II. The importance of DDT in the control of the common insect enemies of mankind, such as mosquitoes, flies, moths, and many agricultural insect pests is realized more day by day. Many studies have been conducted to determine the uses, toxisity and residual effectiveness of DDT. However, the nutritive value of DDT dusted feedstuffs has not been investigated heretofore. During recent years, in the west, alfalfa seed and hay production has declined as a result of injuries caused by certain species of insects such as lygus bage and alfalfa weevil. DDT has been used successfully to control these insect pests. Because of this fact there is a need for more information on the chemical composition, digestibility and metabolisable energy content of DDT treated alfalfa hay.
474

An Extension Teaching Demonstration Using Broiler Chicks as a Model

Ishaya, Joseph B. 01 May 1983 (has links)
This test demonstration was intended to develop a modern management program to improve broiler production in Nigeria through extension teaching methodology. The management programs included animal health, nutrition, and general care. Some of the factors that limit broiler production in Nigeria are associated with the management strategy presently adopted by Nigerian subsistence farmers. This report considers the effect of different protein sources on broiler nutrition and the techniques necessary to get the farmers to practice the result of up-to-date research findings. The extension teaching demonstration reported here is based on 60 day-old chicks. Chicks were randomly assigned to two pens, Pen A and Pen B at the Utah State University poultry farm. Pen A had 40 chicks and Pen B had 20 chicks. Chicks in Pen A received Diet #1 (corn-cottonseed meal). Chicks were weighed weekly starting on July 2, 1983 which was the third week of the demonstration. The difference between the weekly weight gain was obvious. Birds fed corn-soybean diet were superior to those fed corn-cottonseed meal diet. The birds in Pen A were marketable at eight weeks whereas those in Pen B were not marketable at the same chronological age. A field day was conducted at the poultry farm to report the results of the demonstration.
475

Tapirs and Rhinoceroses in Captivity: An Examination of the North American Captive Populations and their Husbandry

Nordstrom, Lisa A. 01 May 2006 (has links)
A..11 species of Tapiridae and Rhinocerotidae are threatened or endangered in the wild. Captive populations have been established for most of these species, but successful management has proved challenging. Effective ex situ conservation strategies, however, rely on the ability of zoological institutions to maintain and breed these endangered species. In this study, I examined the captive environment to identify the factors associated with reproduction, mortality, and health of rhinos and tapirs. Zoological institutions in the North American region that currently housed rhinos and/or tapirs were surveyed in 2003. Attaining an approximately 90% response rate, I compiled information on the following variables to describe the captive environment: number of enclosures, enclosure type, enclosure area, number of animals, public viewing, percent of walls surrounding the enclosure, enclosure substrate, topography, vegetation, mud wallows, pools, shelters, percent shade, climate, diet, feeding regime, time spent by keepers, and vaccinations. Information regarding the incidence of health problems also was obtained through the survey. Studbook data was used to obtain life history and demographic information. Three species of tapirs [Baird's (Tapirus bairdii), South American (T. terrestris), and Malay (T. indicus)] and three species of rhinos [black (Diceros bicornis), white (Ceratotherium simum), and Indian (Rhinoceros unicornis)] were included in this study. Due to the small captive population sizes, genetic and demographic Allee effects were detected. While tapirs responded similarly to their captive environment, each rhino species responded differently. Both exhibit area and completely were associated with the responses of captive tapirs and rhinos. Climate also was an influential factor for both groups of species. Other key factors included density, diet, keeper time, percent of public perimeter, and vaccinations. Complex interactions among the variables were found, including a nonlinear relationship between mean exhibit size and reproduction for black rhinos. The results of this study can be used to improve the captive management of tapirs and rhinos. By identifying the patterns associated with successful reproduction, reduced mortality, and fewer health problems, we can move towards establishing self-sustaining populations for these species. This goal is critical for the continued husbandry and conservation of these species.
476

Effects of Grazing Intensity by Sheep on the Production of Atiplex nummularia and Sheep Live Weight in Jordan

Tadros, Kamal I. 01 May 1987 (has links)
Rangelands in Jordan are deteriorated due to a combination of harsh environmental conditions and human misuse. Jordan is importing increasingly large quantities of meat and animal products to meet the demand from its growing population. Sheep are supplementaQ ly fed during the dry season and large quantities of grain supplements are imported every year. Significant success has been attained in the establishment of Atriplex nummularia lindl. (ATNU) in Jordan. There is, however, a general lack of adequate research to determine if ATNU is effectively utilized by local sheep, to what extent it is utilized and to what extent it tolerates grazing. The objectives of this research were to determine the effects of grazing ATNU at two intensities (moderate and heavy) on subsequent production of ATNU browse, and on sheep live weight. Results of this research showed that HNU shrubs are grazing tolerant, they are stimulated by grazing to produce more forage than the non-grazed shrubs. When heavily grazed in the fall, they showed greater compensatory growth than moderately grazed shrubs, but the moderately grazed shrubs gave sustained production better than those heavily grazed in both good and bad years. Sheep grazing ATNU shrubs with native forage (grasses and forbs) in the fall gained more weight at the moderately grazed treatments. The amount of sheep-live-weight gain was positively affected by the amount of food intake per sheep metabolic body weight and inversely affected by the percentage of ATNU browse in the diet. ATNU although less preferred by sheep than grasses and forbs, could probably be used up to 40% of the diet and still maintain sheep live weight. ATNU is a good source of forage especially during the dry season, it provides (with native grasses and forbs) a high-quality forage and may considerably reduce the amount of costly supplements imported to Jordan.
477

Endocrine Interrelationships During Early Postpartum In St. Croix Sheep

Anderson, Richard Michael 01 May 1990 (has links)
The relationships of estradiol-17-beta, progesterone, and LH in the early postpartum St. Croix ewe were monitored during the breeding season in 1988. A second group of non-postpartum, ovariectomized St. Croix ewes were used to determine non-ovarian levels of progesterone for comparison. Results of this study indicate that: 1. The short duration rise in progesterone exhibited by some ewes is indicative of an ovulation. 2. Ewes that do exhibit a short luteal phase prior to the first "normal" luteal phase have a longer period from parturition to the first "normal" luteal phase. 3. Serum levels of LH increase beginning 3 days postpartum. 4. There is a strong relationship between the concentration of estradiol and the exhibition of behavioral estrus in the postpartum ewe. 5. There appears to be a definite but somewhat irregular pulsatile release pattern of estradiol from the follicle of the postpartum ewe. The ability of the endocrine system of the St. Croix to return to functional levels of production and release during the first 15 days postpartum is likely related to their relatively short postpartum intervals and subsequent pregnancies.
478

Growth of Targhee and Targhee Crossbred Lambs on Utah Rangelands

George, Holly Ann 01 May 1983 (has links)
Growth data were collected on 1848 Targhee and Targhee crossbred lambs from the Utah Agricultural Experiment Station flock at Cedar City for 1981 and 1982. The study objectives were to establish growth curves for seven lamb genotypes and examine within genotype growth differences among four grazing treatments (sheep alone, sheep and cattle mixed, both continuous and rotation). Body weights were measured at birth, and at mean ages of 56, 120, and 154 (weaning) days of age. Linear, quadratic, and cubic regressions of weight on age were used to establish growth curves. Among genotype comparisons of entire growth curves were impossible as non-linear components were significant. (p<.05). Thus, weights per weigh period and average daily gain between weigh periods were examined to determine differences. Rearing type, birth type, genotype, and pasture treatment were 50.9%, 22.7%, 12.4%, and 6.1%, respectively, of the total variance accounted for by the effects on weaning weights examined. Overall growth patterns were the same for all genotypes with the most rapid gains occurring between 56 and 120 days of age (combined mean .66 pounds). Suffolk-sired lambs from Suffolk-Targhee and Targhee-Finn-Targhee ewes were faster gaining (p<.05) than straight-bred Targhee lambs as well as those from Suffolk sires bred to finn-Targhee, Targhee-Suffokl-Targhee ewes. The second most rapid gains (combined mean .56 pounds) occurred between birth and 56 days. All crossbred lambs had higher average daily gains than Targhee lambs (p%lt;.05). The slowest rate of gain (mean .16 pounds) occurred int he 34 days prior to weaning. Not all differences in body weight among pastures can be attributed to grazing treatments as three genotypes exhibited a significant (p<.05) effect of pasture assignment on weight prior to treatment implementation. Despite initial weight imbalances, genotypes responded similarly to pasture treatments. Sheep rotation pastures had the lightest (p<.05) lambs for most genotypes exhibiting differences in grazing treatments at 120 days and in all genotypes at weaning. The fastest gains and heaviest lambs were in mixed species pastures. In sheep alone pastures, lamb performance was better in continuously grazed pastures than in the rotation pastures.
479

Assessment of Microchimerism Following Somatic Cell Nuclear Transfer and Natural Pregnancies in Goats (<i>Capra aegagrus hircus</i>)

Gash, Kirsten Karen 01 August 2018 (has links)
Somatic cell nuclear transfer (SCNT) is a powerful tool for production of transgenic animals for various biomedical and agricultural applications. For instance, our group is using SCNT to produce transgenic goats to study the role of cardiac fibrosis in initiation and progression of atrial fibrillation. There is a possibility of cell transfer from a transgenic fetus to its non-transgenic surrogate mother, known as fetal microchimerism; from a transgenic mother to non-transgenic fetus, maternal microchimerism and from a transgenic twin to non-transgenic twin in utero. Initially, we have assessed the presence of fetal microchimerism in tissue samples from non-transgenic surrogates that delivered transgenic SCNT generated offspring. Then, the SCNT derived transgenic goats were naturally bred and non-transgenic offspring were used for the assessment of maternal microchimerism. Additionally, fetal-fetal microchimerism was evaluated using the tissue samples from non-transgenic twins of transgenic offspring. We investigated DNA from kidney, liver, lung, lymph node and spleen for the presence of neomycin resistant gene (Neo), which all transgenic SCNT generated females and their transgenic offspring tested positive for. We found no detectable maternal or fetal-fetal microchimerism, but fetal microchimerism was detected in lymph node of one of the surrogate dams that carried a SCNT pregnancy. The results of the study have direct implications on the use and disposal of non-transgenic surrogates and non-transgenic offspring.
480

Wool Scouring Tests in Utah

Esplin, Alma C. 01 May 1941 (has links)
Wool as it is shorn from the sheep, is known as grease wool. The first tep in the manufacturing of wool is scouring, or removal of all grease and foreign matter. Within any given grade, as determined by length of staple and fineness of fiber, the yield of clean wool is the primary factor in determining the value of the original grease wool. The price of scoured or clean wool is multiplied by the percentage yield of clean wool to determine the value of the grease wool. Wool is graded and sorted before being scoured by the manufacturer. Large quantities are prepared for the scouring vate and the identity of the grower's clip is lost. Hence, the grower is entirely dependent upon the buyer's estimate of shrinkage or yield of clean wool, unless he obtains a representative sample of his clip and has it scoured to determine the yield. The object of the work reported in this thesis was to obtain information on the variability in yields of clean wool in Utah herds, and to add to work already done on methods of sampling and dtermining yields. Three methods have been used: (1) Whole fleece samples, (2) composite samples, and (3) side samples from individual sheep. Literature concerning each of these methods and other pertinent material is reviewed, and results obtained in Utah are presented.

Page generated in 0.0982 seconds