Browsing by Author "Whittier, W. Dee"
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- Anaplasmosis in Beef CattleWhittier, W. Dee; Currin, Nancy; Currin, John F. (Virginia Cooperative Extension, 2005-09-01)Anaplasmosis is an infectious disease of cattle caused by several species of the blood parasite Anaplasma. A. marginale is the most common pathogen of cattle.
- Beef cow/calf herd health program and calendarWhittier, W. Dee; Currin, John F. (Virginia Cooperative Extension, 2000)
- Beef Cow/Calf Herd Health Program and CalendarWhittier, W. Dee; Currin, John F. (Virginia Cooperative Extension, 2005-09-01)Losses caused by disease represent a major obstacle to the profitability of many cow/calf beef operations. It is widely agreed that prevention rather than treatment is the most economical approach to keeping disease losses low.
- Calving Emergencies in Beef Cattle: Identification and PreventionWhittier, W. Dee; Currin, Nancy; Currin, John F.; Hall, John B. (Virginia Cooperative Extension, 2005-09-01)Calving difficulty, technically called dystocia, is a major cause of death loss in cow-calf herds. Studies indicate that dystocia is responsible for 33 percent of all calf losses and 15.4 percent of beef cattle breeding losses.
- Control of Internal Parasites in SheepWhittier, W. Dee; Zajac, Anne M.; Umberger, Steven H. (Virginia Cooperative Extension, 2009)Internal parasites are a threat to sheep health and productivity. Increased understanding of the role and actions of internal parasites provides the basis for more effective control programs.
- Control, Treatment, and Elimination of Foot Rot from SheepWhittier, W. Dee; Umberger, Steven H. (Virginia Cooperative Extension, 2009)Ovine foot root is an infectious, contagious disease of sheep that causes severe lameness. Control and elimination of the disease should be the goal of all sheep producers.
- Current strategies in parasite control in Virginia beef cattleCurrin, John F.; Whittier, W. Dee (Virginia Cooperative Extension, 2000)
- Current Strategies in Parasite Control in Virginia Beef CattleWhittier, W. Dee; Currin, John F. (Virginia Cooperative Extension, 2005-09-01)Many advances have been made in the field of livestock parasite control over the past few years. Because parasites decrease production, control of parasites can have a direct economic impact on beef cattle operations.
- Effects of Pasteurella haemolytica on Pulmonary Vascular Adrenergic MechanismsRogers, Ernest Reginald (Virginia Tech, 2003-08-15)Pneumonic pasteurellosis is a significant disease in beef production medicine. The most recent information suggests that this disease is a $700 million dollar per year economic burden in bovine food animal production The medical and pathological characteristics of this disease are well documented. Many pathological findings associated with pneumonic pasteurellosis may be explained by disruption of the pulmonary vascular adrenergic system. However, only a limited amount of research has addressed the adrenergic system and its relationship to the etiology and pathophysiology of this disease. In an attempt to further investigate the contributions of the vascular adrenergic receptor mechanism to the development of pneumonic pasteurellosis a series of six experiments have been completed. It is to be noted, that in 1999 the organism Pasteurella haemolytica was renamed Mannheimia haemolytica. The name change was based on the taxonomic features of the organism from other closely related organisms, in particular Pasteurella multocida.. The differences noted were identified and described by Dr. Mannheim in 1974. The familiarity of the past nomenclature and the lack of familiarity for the new nomenclature suggests that the more commonly recognized name of Pasteurella haemolytica should be used throughout this document. Scientific evidence suggests that the disruption of the normal homeostatic mechanisms of the pulmonary vasculature to beta adrenergic agents may be part of the etiology of pneumonic pasteurellosis. The dynamics and kinetics of the involvement of the beta receptors, following prophylactic vaccination and in the disease state, has yet to be fully investigated with respect to the events associated with pneumonic pasteurellosis. Evaluation of the time frame of the onset and duration of the events associated with the disruption of pulmonary vascular beta adrenergic receptor mechanisms revealed that an escalating level of dysfunction occurs over the first 24-48 hour period after exposure to parenteral Pasteurella haemolytica and lasts for at least 21 days. A component of P.haemolytica organism or contained in the vaccine using the organism is likely associated with the disruption of vascular beta adrenergic mechanism. This factor is, as yet, not specifically identified, however the likely culprit is the lipid A moiety of the endotoxin. Using the well defined and purified Escherichia coli endotoxin, trials were run to examine the effect of endotoxin on the pharmacological response of vascular associated beta adrenergic receptor mechanisms. The effects of Escherichia coli endotoxin, administered parenterally, on beta adrenergic receptor mechanisms were pharmacologically indistinguishable from those effects following parenterally administered Pasteurella haemolytica. The nature of the disruption in the beta adrenergic receptor remains a mystery. The receptor mechanism involves at least two second messengers to initiate vascular relaxation. Initial activation of the beta adrenergic receptor with a beta selective drug starts a cascade of events involving adenylylate cyclase and cyclic adenylylate monophosphate (cAMP) and nitric oxide. A disruption in the receptor mechanism, as a result of the parenteral administration of Pasteurella haemolytica, which is "upstream" of adenylyl cyclase, would result in a diminished amount of cAMP when compared to the unvaccinated negative controls. An investigation of cAMP accumulation, at the receptor level was inconclusive. The assessment of some previously used vaccines has demonstrated that there is an, as yet unidentified virulence factor, associated with these vaccines that results in the pharmacological disruption of beta adrenergic receptor mechanisms. Two newer vaccines, Once PMH® and One Shot® have been evaluated and there is evidence to suggest that these currently used vaccines also have the ability to disrupt beta adrenergic receptor mechanisms in rats. The effects of parenteral P. haemolytica on the alpha-2 adrenergic receptor mechanism, is described. The alpha-2 receptor mechanism, unlike the beta receptor mechanism appears to increase the amount of vasoconstriction. The possibility that the alpha-2 adrenergic receptor could also mediate vasorelaxation under certain conditions was investigated. The evidence suggests that in the presence of high alpha-1 mediated vascular tone, the alpha -2 receptor can cause vasorelaxation. Evidence, from other scientists active in this area of investigation, suggests that a vasorelaxation response may be mediated by nitric oxide. Elimination of the nitric oxide mediated relaxation may offer an explanation for the increased vasoconstriction noted with alpha-2 selective drugs after exposure to parenteral P. haemolytica. Finally, the importance of the beta adrenergic receptor to the disease process is addressed by elucidation of one of the mechanisms by which Micotil 300® (tilmicosin phosphate) acts to improve cattle with symptomatic pneumonic pasteurellosis. The rapid improvement of animals on Micotil 300®, with-in 24 hours suggests that there is a mechanism beyond the antimicrobial effect of the drug that mediates the clinical improvement. Evaluation of the effect of Micotil 300® demonstrates a pharmacologically measurable amount of beta adrenergic activity with respect to the bovine pulmonary artery and vein. Based on the conclusions drawn as a result of these experiments, the adrenergic system in general, and the beta adrenergic system in particular are important to the development of pneumonic pasteurellosis in cattle. The beta adrenergic system is affected by endotoxin. Further, these receptors maybe responsible for the mediation of the pathological and clinical signs associated with pneumonic pasteurellosis. In conclusion, these investigations have suggested, that it is likely that a disruption in the homeostatic mechanisms mediated by the beta and alpha-2 adrenergic receptors are intimately involved in the development of post vaccination receptor failure as well as the pathophysiology associated with pneumonic pasteurellosis in cattle.
- Estrus Synchronization for HeifersHall, John B.; Liles, Amanda Gail; Whittier, W. Dee (Virginia Cooperative Extension, 2005-09-01)By using estrus synchronization and artificial insemination, you can increase the number of heifers calving early in the calving season, reduce dystocia, use superior sires, and increase calf weaning weights.
- Feeder and Stocker Health and Management PracticesWhittier, W. Dee; Currin, John F. (Virginia Cooperative Extension, 2005-09-01)Disease represents a major problem in most feeder and stocker settings. Outbreaks of disease can result in as much as a 30% death loss. Treatment costs, feed efficiency losses, and labor necessary for treatment make disease loss substantial in many situations.
- Feeder and stocker health and management practicesCurrin, John F.; Whittier, W. Dee (Virginia Cooperative Extension, 2000)
- The Food Animal Veterinarian, No. 1, Spring 1988(Virginia Cooperative Extension Service, 1988)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.
- The Food Animal Veterinarian, No. 10, Fall 1992(Virginia Cooperative Extension Service, 1992)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.
- The Food Animal Veterinarian, No. 11, Spring 1993(Virginia Cooperative Extension Service, 1993)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.
- The Food Animal Veterinarian, No. 13, Spring 1994(Virginia Cooperative Extension Service, 1994)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.
- The Food Animal Veterinarian, No. 14, Fall 1994(Virginia Cooperative Extension Service, 1994)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.
- The Food Animal Veterinarian, No. 15, Fall 1995(Virginia Cooperative Extension Service, 1995)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.
- The Food Animal Veterinarian, No. 16, Fall 1996(Virginia Cooperative Extension Service, 1996)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.
- The Food Animal Veterinarian, No. 18, Fall 1997(Virginia Cooperative Extension Service, 1997)An extension newsletter directed at the needs and interests of the food animal veterinarian. Provides a synopsis of practical information and research reports, as well as a bulletin board of the Virginia Academy of Food Animal Practice.