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Author:
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ISBN:
Category : Bovine leukemia virus
Languages : en
Pages : 2
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Book Description
Author:
Publisher:
ISBN:
Category : Bovine leukemia virus
Languages : en
Pages : 2
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Book Description
Author:
Publisher:
ISBN:
Category : Bovine leukemia virus
Languages : en
Pages : 2
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Book Description
Author: Mario Cleves
Publisher: Stata Press
ISBN: 1597180416
Category : Computers
Languages : en
Pages : 398
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Book Description
"[This book] provides new researchers with the foundation for understanding the various approaches for analyzing time-to-event data. This book serves not only as a tutorial for those wishing to learn survival analysis but as a ... reference for experienced researchers ..."--Book jacket.
Author: Omid A. Nekouei
Publisher:
ISBN:
Category :
Languages : en
Pages :
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The overall goal of the research described in this thesis was to lay a proper foundation for designing and conducting efficient control and eradication programs for infection with bovine leukemia virus (BLV) in the Canadian dairy industry. The objective in Chapter 2 was to identify potentially important risk factors for BLV infection in Canadian dairy herds. Of 272 study herds, from 8 provinces of Canada and tested during 1998-2003, 78% were BLV-positive. Over 15 management determinants for the infection were evaluated. Herds with clinical cases of leukosis during the 12 months prior to sampling, as well as herds which purchased animals with unknown BLV infection status in the last five years, had a significantly increased proportion of BLV-positive cows. Herds from eastern provinces and those not purchasing cows in the last five years were more likely to be free from BLV compared to western provinces and farms purchasing cows in the last five years. The objective in Chapter 3 was to determine the lifetime effects of BLV infection on milk production and longevity of dairy cows in Canada. Overall, 4052 cows from 348 herds were enrolled in a historical cohort study, based on test results from 1998-2003 and lactation and culling records post-testing until 2013. Positive cows to BLV had consistently greater probability of being culled (or dying) than the negative cows (over lifetime lactations 2-7). Only BLV-positive cows with short longevity (2 and 3 lifetime lactations) had a significantly lower lifetime milk production compared with their negative counterparts. As the cows lived longer (> 3 lactations), the difference in milk production between the two cohorts was no longer significant. The objectives of Chapter 4 were: 1) to assess the potential for carryover of antibodies against BLV in milk samples obtained from shared meters; and 2) to determine if adjustment of the diagnostic test cut-off value would improve the test characteristics for meter-collected milk ELISA results. The study included 236 paired milk samples from 8 dairy farms in Prince Edward Island collected in 2013. Two simultaneous milk samples, one hand-collected at the beginning of milking, and the other from the corresponding milk meter, were taken from all lactating cows that were milked at the selected meters. The sequence of cows using each meter was recorded. Carryover of BLV antibodies at shared milk meters was significant. For low-titer cows, the carryover effect was positively associated with the titer of the preceding cows. This could result in generating false-positive results in the BLV antibody-ELISA test on meter-collected samples from dairy herd improvement (DHI) procedures. Based on a new optimal cut-point, a suspicious category on the ELISA titers was defined, and a retest on the samples falling within this range was recommended to reduce the false positive rate. The objectives for Chapter 5 were: 1) to determine the prevalence of BLV infection at the herd level using a bulk-tank milk (BTM) antibody ELISA in the Maritime region of Canada ; and 2) to develop applied statistical models for predicting within-herd prevalence of BLV infection using the BTM antibody levels. To detect BLV infection and the antibody levels, a census was implemented on BTM samples from all dairy farms in the Maritime region in 2013 (3 monthly rounds of sampling on 623 farms). Another round of BTM sampling was coincided with individual cow sampling (all cows that contributed milk to the fourth BTM) in 90 selected herds. Herd-level prevalence of BLV in the Maritime region was 90.8%. In the individual testing, 30.4% of cows were positive. The statistical models developed in this study were able to predict true within-herd prevalence of BLV reasonably well based only on the BTM results. The model including all BTM tests (4 rounds of sampling) as the predictor had the best fit, although the models using 2 and 3 BTM tests provided similar results to 4 repeated tests. The focus for Chapter 6 was to assess the diagnostic performance of a commercially available ELISA for detecting BLV antibodies in BTM samples collected from dairy herds in Eastern Canada in 2013. Of 133 tested herds, 108 herds were found to be truly infected. At the resulting optimal cut-point, sensitivity and specificity of the BTM ELISA were estimated at 0.972 (0.921 - 0.994) and 1 (0.863 - 1), respectively. With the high prevalence of BLV infection across Canada and its detrimental economic impacts, pursuing broad-based control programs is necessary. All of the findings in the present research could contribute to designing and conducting efficient BLV control programs.
Author: Vickie J. Ruggiero
Publisher:
ISBN: 9781392118214
Category : Electronic dissertations
Languages : en
Pages : 154
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Book Description
Bovine leukemia virus (BLV) is an oncogenic deltaretrovirus of cattle that is estimated to infect more than 40% of U.S. dairy cows and cost the dairy industry hundreds of millions of dollars per year. BLV inserts a DNA copy (provirus) into the host genome and can cause leukemia and lymphoma in 1-5% of infected animals, while around 30% develop a non-malignant lymphocytosis, often coupled with high proviral load. BLV infection in dairy cows has also been associated with a number of economically important effects, such as decreased milk production, longevity, and immune function. The primary goal of this dissertation was to develop management protocols that can be implemented on U.S. dairy operations. We also aimed to further characterize in vivo immunologic effects of BLV infection, especially at mucosal junctions, hypothesizing that BLV+ cows would have lower concentrations of IgA antibody. To test the effect of BLV infection on total IgA concentrations, we analyzed the milk, saliva, and serum of BLV+ cows with varying lymphocyte count and proviral load profiles for comparison with BLV- herd mates. We found that BLV+ cows exhibited numerically lower concentrations of IgA in both milk and saliva, but not serum, in comparison to BLV- cows. Although the observed decreases were not statistically significant, the biological effects remain unknown. We also observed that the lowest concentrations of IgA were seen in the milk and saliva of BLV+ cows without lymphocytosis or high PVL, and these differences were trending toward significance. Our data, if confirmed, suggests that BLV may be disruptive to the immunology of mucosal junctions. We developed and implemented three field trials to evaluate management protocols for control of BLV in dairy herds. The first trial investigated the frequently suggested management intervention of improved medical hygiene by changing from shared needles and reproductive sleeves to single-use items. In this field trial, BLV- herd mates were assigned to control (re-use) or intervention (single-use) groups and the incidence risk was calculated semi-annually. Although we saw no difference in the risk of new infections in our study, medical hygiene may still play a role in the transmission of BLV as well as other diseases. This study also identified an increase in incidence risk in the summer exposure period. Meanwhile, our second field trial was a novel intervention which used milk ELISA screening to identify BLV+ cows for further characterization of their lymphocyte count (LC) and proviral load (PVL). In this manner, we identified cows thought to be the most infectious to their susceptible herd mates, and worked with herd managers to create a priority removal plan to consider when culling cows or implementing segregation measures. Overall, the three enrolled herds significantly reduced both BLV prevalence and incidence risk over a 2 to 2.5 year period. In this study, no significant associations with season were observed. Our final field trial aimed to demonstrate that milk ELISA testing could be used in herds with low BLV prevalence in order to identify and remove the few remaining BLV+ animals and achieve eradication of the virus. Two herds that were able to remove all BLV+ adult cows were generally successful, though the young stock (first lactation heifers) were a reservoir for reintroduction. In addition, we observed 5 first lactation heifers in one herd which had previously tested negative on serum ELISA but later tested positive on milk ELISA after entering the milking herd. This agrees with reports of latent BLV infections, and provides further evidence that long-term surveillance and further research on the infection dynamics of BLV are needed.
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 83
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Book Description
Bovine leukemia virus (BLV) is an oncogenic retrovirus that causes bovine leukosis (BL), a multicentric cancer of B lymphocytes. The BLV affects B lymphocytes in cattle and sheep. Bovine leukemia, lymphosarcoma, and malignant lymphoma are also names given to BL. BLV is an oncogenic that infects approximately 96% of all dairy herds in the US. Among dairy and beef operations surveyed in mid-1990, 89% and 38%, respectively, had BLV present in their herds. In 75% of the positive US dairy herds, at least 25% of the animals were BLV-positive. However, 10.3% of the animals tested in beef cattle were seropositive. Infection with BLV is endemic in US dairy herds, with at least 50% and usually more than 70% of animals within those herds having antibodies to the virus. Continuous scores and binary milk ELISA results for 13,217 Holstein cows from 114 dairy herds across 16 US states and 642 Jersey cows from eight dairy herds were considered. The objectives of this study were to estimate: 1) the heritability of BL incidence in Holstein and Jersey populations, 2) the genetic merit of sires for leukosis susceptibility in dairy cattle, 3) the genetic correlation of BL incidence with milk yield and SCS, and 4) to determine potential genomic regions and gene pathways that might be associated with BL incidence. In summary, this study presented the first, comprehensive genetic study of BL incidence in commercial dairy herds in the US. Estimates of heritability obtained with the two approaches were approximately 8% for both breeds. Genetic correlations among BL, MY and SCS obtained from the linear model were moderate, and higher than those from the threshold model. Estimated SNP effects obtained from the two models indicated some genomic regions that might be associated with BL incidence, such as in chromosomes 1, 14, 16 and 17. Although many additional studies are still necessary to better understand BLV infection and BL, the results found so far indicate an important genetic component contributing to BL incidence, which could be potentially explored to attenuate the economic losses and public health concerns caused by the BL.
Author: Keith Woodford
Publisher: Chelsea Green Publishing
ISBN: 1603582118
Category : Medical
Languages : en
Pages : 258
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Book Description
This groundbreaking work is the first internationally published book to examine the link between a protein in the milk we drink and a range of serious illnesses, including heart disease, Type 1 diabetes, autism, and schizophrenia. These health problems are linked to a tiny protein fragment that is formed when we digest A1 beta-casein, a milk protein produced by many cows in the United States and northern European countries. Milk that contains A1 beta-casein is commonly known as A1 milk; milk that does not is called A2. All milk was once A2, until a genetic mutation occurred some thousands of years ago in some European cattle. A2 milk remains high in herds in much of Asia, Africa, and parts of Southern Europe. A1 milk is common in the United States, New Zealand, Australia, and Europe. In Devil in the Milk, Keith Woodford brings together the evidence published in more than 100 scientific papers. He examines the population studies that look at the link between consumption of A1 milk and the incidence of heart disease and Type 1 diabetes; he explains the science that underpins the A1/A2 hypothesis; and he examines the research undertaken with animals and humans. The evidence is compelling: We should be switching to A2 milk. A2 milk from selected cows is now marketed in parts of the U.S., and it is possible to convert a herd of cows producing A1 milk to cows producing A2 milk. This is an amazing story, one that is not just about the health issues surrounding A1 milk, but also about how scientific evidence can be molded and withheld by vested interests, and how consumer choices are influenced by the interests of corporate business.
Author: Eunyoung Lee
Publisher:
ISBN:
Category :
Languages : en
Pages : 288
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Book Description
Author: Thomas J. Divers
Publisher: Elsevier Health Sciences
ISBN: 1437710832
Category : Medical
Languages : en
Pages : 700
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Book Description
REBHUN'S DISEASES OF DAIRY CATTLE, 2nd Edition is your all-in-one guide to bovine disease management. With thorough, up-to-date coverage of differential diagnosis methods, surgical and therapeutic treatment options, and prevention strategies, it provides vital information for battling bovine diseases in both dairy and non-dairy cattle. The book is organized by body system for quick, convenient reference, and this new edition meets the growing need for management of both diseases of individual cows and problems affecting whole herds. - Individual case presentations provide a valuable tool for differential diagnosis. - Practical overviews for procedures such as blood transfusion, abdominal paracentesis, and ECG give you reliable support for some of the most common procedures in bovine care. - Body systems organization makes diagnosis easier and more effective by isolating system-specific diseases and conditions. - Full-color design and over 200 new photographs depict disease processes in realistic clarity and ensure the most accurate diagnosis and treatment. - Emphasis on herd health addresses the dairy industry's increased concern over population medicine. - Expanded coverage of lameness highlights key problem areas in bovine feet. - Revised drug usage recommendations and legal considerations present the most current information in these critical areas to help you prevent dangerous or costly errors. - Additional public health/safety considerations identify diseases that pose a substantial public threat and detail special measures for related care of dairy cattle. - New, innovative DVD features real-time videos of neurologic case studies, ultrasound and endoscopy procedures, and imaging techniques that familiarize you with the latest technological equipment and protocols. - Features coverage of the latest treatment innovations including antibiotic residue testing, care of individual metabolic disease, troubleshooting, and much more.
Author: Robert S. Youngquist
Publisher: Elsevier Health Sciences
ISBN: 1437713408
Category : Medical
Languages : en
Pages : 1088
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Book Description
An essential resource for both students and practitioners, this comprehensive text provides practical, up-to-date information about normal reproduction and reproductive disorders in horses, cattle, small ruminants, swine, llamas, and other livestock. Featuring contributions from experts in the field, each section is devoted to a different large animal species and begins with a review of the clinically relevant aspects of the reproductive anatomy and physiology of both males and females. Key topics include the evaluation of breeding soundness, pregnancy diagnosis, diagnosis and treatment of infertility, abortion, obstetrics, surgery of the reproductive tract, care of neonates, and the latest reproductive technology. Includes coverage of all large animal species. All sections provide a review of clinically pertinent reproductive physiology and anatomy of males and females of each species. Complete coverage of the most current reproductive technology, including embryo transfer, estrous synchronization, and artificial insemination. A new section on alternative farming that addresses reproduction in bison, elk, and deer. New to the equine section: stallion management, infertility, and breeding soundness evaluation. New to the bovine section: estrous cycle synchronization, reproductive biotechnology, ultrasonographic determination of fetal gender, heifer development, and diagnosis of abortion. New to the porcine section: artificial insemination, boar/stud management, diseases of postpartum period, and infectious disease control. New to the llama section: infectious disease and nutrition.
