Search PubMed⌕ Search

Biomedical subjects

J W Lloyd

Publications and source records attributed to J W Lloyd.

At least 19 recordsLinked to original sources
PubMed2001

Veterinary practice management education in the Association of American Veterinary Medical Colleges member colleges during 1999.

Most veterinary students enrolled at AAVMC member institutions take at least 1 VPM course prior to graduation. These courses are characterized by widespread involvement of outside lecturers with business expertise, which likely adds to their strength. However, it remains that wide variation in VPM education exists across the AAVMC with regard to the topics addressed, the specific business expertise of faculty and administrative course specifics. As such, the situation provides several key opportunities. Foremost among these is the immediate need for profession-wide discourse on VPM education to define reasonable expectations with regard to the business skills of veterinary graduates. In addition, outcomes assessment would provide information on which of the widely varying approaches to VPM education is most likely to produce successful graduates. The opportunity also exists for development of academic research programs to support VPM education directly by strengthening the related disciplinary knowledge base. Effective leadership for these efforts will be crucial to their success.

Cross-Sectional Studies↗
PubMed2001

Reliability of three bulk-tank antimicrobial residue detection assays used to test individual milk samples from cows with mild clinical mastitis.

OBJECTIVE: To determine the likelihood of false-positive results when testing milk samples from individual cows by use of 3 commercially available assays (Penzyme MilkTest and the SNAP beta-lactam and Delvo-SP assays) labeled for use with commingled milk. SAMPLE POPULATION: Milk samples from 111 cows with mild clinical mastitis. PROCEDURE: Cows were randomly assigned to the control (no antimicrobials) or intramammary treatment group. Posttreatment milk samples were collected at the first milking after the labeled withholding period or an equivalent time for controls, randomly ordered, and tested twice by use of each assay and once by use of high-performance liquid chromatography. Sensitivity, specificity, and positive and negative predictive values were determined for each assay. Concordance of results for the same sample was assessed for each assay by calculating kappa. RESULTS: Sensitivities of the Delvo-SP and SNAP lactam assays were > 90%, whereas the sensitivity of the Penzyme Milk Test was 60%. Positive predictive values (range, 39.29 to 73.68%) were poor for all 3 assays. Concordance of test results was excellent for the SNAP beta-lactam and Delvo-SP assays (kappa = 0.846 and 0.813, respectively) but was less for the Penzyme MilkTest (kappa = 0.545). CONCLUSIONS AND CLINICAL RELEVANCE: Because of the low positive predictive values, these 3 assays may not be useful for detecting violative antimicrobial residues in individual milk samples from cows treated for mild clinical mastitis. However, repeatability of each assay was considered good to excellent.

Animals↗
PubMed2001

Veterinary practice management: teaching needs as viewed by consultants and teachers.

A study was conducted to assess veterinary practice management (VPM) educational and research needs from the perspective of consultants and teachers. An online focus group discussion was designed, involving two separate groups (consultants and teachers). One week was allocated to each group, with five to eight questions posed per day. Pseudonyms were used to provide confidentiality. Teachers were selected by inviting the primary VPM course coordinator at each AAVMC school. Consultants required at least two recommendations and were selected in a stratified, non-random manner to achieve both geographic and disciplinary diversity. Participation was stronger within the consultant group: 98 pages of data were generated by the consultants and 35 pages by teachers. Participants agreed that the sub-optimal economic conditions that characterize the veterinary profession are reflective of relatively low-level management skills. This situation establishes the need to strengthen VPM educational and research programs. Many specific suggestions were provided. It was recommended that a cooperative effort between academia and the private sector be employed. However, participants recognized that successful DVM education programs in VPM will be difficult to achieve and sustain without strong support from college administrators and faculties.

Consultants↗
PubMed2001

The effect of subclinical Mycobacterium paratuberculosis infection on milk production in Michigan dairy cows.

The objective of this study was to determine the effect of subclinical Mycobacterium paratuberculosis infection on mature equivalent milk, protein, and fat production in a sample of Michigan dairy herds with a history of cows positive for M. paratuberculosis diagnosed by fecal culture. A prospective two-group cohort study was conducted. Participating herds were tested, and productivity and reproduction records were monitored for 18 mo. All cows aged 24 mo and greater were tested for M. paratuberculosis infection using the ELISA and radiometric fecal culture (RFC) techniques. Using both tests in parallel, the overall sample apparent prevalence for M. paratuberculosis infection was 41.8%. Adjusting for diagnostic sensitivity and specificity resulted in a calculated sample true prevalence of 59.9%. Subclinical paratuberculosis test-positive status had no statistically significant effect on mature equivalent milk, fat, or protein production. The results of this study concur with the findings of other studies, reporting that the magnitude and direction of the association between subclinical paratuberculosis infection and milk production depends upon the parity of the animal, stage of disease, and the stage in lactation being monitored. Assessment of the impact of subclinical paratuberculosis on milk production must consider the average parity of the sample population. In herds that have an average parity of 2 or less, subclinical paratuberculosis infection may have little impact on milk production.

Animals↗
PubMed2000

Spatial and temporal comparison of selected cancers in dogs and humans, Michigan, USA, 1964-1994.

Our aim was to investigate the geographic and time distributions of some biologically similar neoplasms in dogs and humans living in Michigan, USA, between 1964 and 1994. Our objective was to describe and compare the patterns of cancer in the two species while assessing the strength and dependence of those patterns. In this retrospective, registry-based study, histologically confirmed incident human and canine cancer cases were mapped, and second-order (K function) spatial analysis and one-dimensional nearest neighbor temporal analysis were performed on residence addresses and dates of hospital discharge/diagnosis. Included in the study were all 528 incident cases of canine lymphosarcoma, mammary adenocarcinoma, melanoma and spindle-cell sarcomas diagnosed at a veterinary teaching hospital between 1964 and 1994 having residence addresses in Ingham, Oakland, and Wayne Counties; and a stratified random sample of 913 incident human cases of comparable cancers diagnosed during the same time period from the same counties. Results suggest that processes determining spatial aggregation of cases in dogs and humans were not independent of each other, did not act uniformly over different geographic areas, operated at spatial scales <2000 m regardless of species, and tend to act upon dogs more strongly at shorter distances than on humans. Little evidence of interspecies concurrence of temporal clustering was found.

Adenocarcinoma↗
PubMed2000

The effect of subclinical Mycobacterium paratuberculosis infection on days open in Michigan, USA, dairy cows.

A prospective cohort study design was used to evaluate the impact of subclinical Mycobacterium paratuberculosis infection on days open in a sample of Michigan dairy herds with a history of cows positive for M. paratuberculosis diagnosed by fecal culture. Participating herds were tested and productivity and reproduction records were monitored for 18 months. All cows > or = 24 months old were tested for M. paratuberculosis infection using the ELISA and radiometric fecal-culture (RFC) techniques. Test-negative cows were re-tested at the conclusion of the monitoring period. Multivariable regression models were used. Using both tests in parallel, the overall sample apparent prevalence for M. paratuberculosis infection was 41.8% (223/533 animals tested). Adjusting for diagnostic sensitivity and specificity, this resulted in a calculated sample true prevalence of 59.9%. ELISA-positive cows (on average) had a 28-day increase in days open when compared to ELISA-negative cows (p=0.02). The diagnostic method used to define a case altered the apparent association between paratuberculosis test status and days open. Fecal culture was a less-effective diagnostic tool for use in herds with a high prevalence of infected animals. The increase in days open in the ELISA-positive cows was an indication that perhaps reduced estrus expression or an increased post-partum anestrous period occurred in the subclinically infected ELISA-positive animals. This might have been due to a negative energy balance associated with M. paratuberculosis infection.

Animals↗
PubMed2000

Influence of the Milk and Dairy Beef Quality Assurance Program on dairy farm drug management practices.

OBJECTIVE: To test the hypothesis that dairy farms certified in the Milk and Dairy Beef Quality Assurance Program (QAP) were more likely to use prudent drug management practices than farms that were not certified. DESIGN: Cross-sectional study. SAMPLE POPULATION: 141 Michigan dairy farms of which 74 were not certified in the QAP, 30 were involuntarily certified, and 37 were voluntarily certified. PROCEDURE: Dairy producers completed a self-administered questionnaire that focused on herd health management, drug use, record keeping, personnel management, and descriptive characteristics of their farm during 1993. Separate multivariable logistic regression models were developed to determine the association of QAP certification with each of the management practices. RESULTS: Results suggested that farms adopted specific management practices irrespective of certification. Many farms used visible identification and non-emergency veterinary services and discussed residue prevention with employees. Involuntary certification was associated with maintenance of good written treatment records and performance of on-farm drug residue testing. Voluntary certification was weakly associated with use of refrigerated drug storage. CONCLUSIONS AND CLINICAL RELEVANCE: QAP certification appeared to have been associated with the adoption of only a few prudent drug use practices, although QAP materials and framework were developed to assist veterinarians in the promotion of disease prevention, client communication, and residue prevention practices on farms. Veterinary care would benefit from the development and encouragement of better record keeping on farms.

Animals↗
PubMed2000

Use of a non-linear spline regression to model time-varying fluctuations in mammary-secretion element concentrations of periparturient mares in Michigan, USA.

A study was designed to model the fluctuations of nine specific element concentrations in mammary secretions from periparturient mares over time. During the 1992 foaling season, serial samples of mammary secretions were collected from all 18 pregnant Arabian mares at the Michigan State University equine teaching and research center. Non-linear regression techniques were used to model the relationship between element concentration in mammary secretions and days from foaling (which connected two separate sigmoid curves with a spline function); indicator variables were included for mare and mare parity. Element concentrations in mammary secretions varied significantly during the periparturient period in mares. Both time trends and individual variability explained a significant portion of the variation in these element concentrations. Multiparous mares had lower concentrations of K and Zn, but higher concentrations of Na. Substantial serial and spatial correlation were detected in spite of modeling efforts to avoid the problem. As a result, p-values obtained for parameter estimates were likely biased toward zero. Nonetheless, results of this analysis indicate that monitoring changes in mammary-secretion element concentrations might reasonably be used as a predictor of impending parturition in the mare. In addition, these results suggest that element concentrations warrant attention in the development of neonatal milk-replacement therapies. This study demonstrates that non-linear regression can be used successfully to model time-series data in animal-health management. This approach should be considered by investigators facing similar analytical challenges.

Animal Husbandry↗
PubMed2000

Parents' predicted transmitting abilities are not associated with culling prior to second lactation of Michigan, USA dairy cows.

The objective of this study was to test the association between parents' predicted transmitting abilities (PTAs) for milk, fat and protein and subsequent culling of heifers during rearing or first lactation. The data from 1992 to 1996 consisted of the culling outcome of 5619 Michigan Holstein heifers during rearing or first lactation, and the heifers' parents' PTAs from the period in which the heifers were born. Fixed-effect probit models (both dichotomous and ordered) estimated the relationships between culling and parents' PTAs. Herd effect was modeled as a fixed-effect. There was no association between PTAs of milk, fat, and protein for each heifer's parents and subsequent culling of the heifer during rearing or first lactation. Weak evidence for the necessity of modeling the herd effect as fixed was present. The lack of association between parents' PTAs and reason-specific culling (voluntary versus involuntary)--coupled with the counter-intuitive effects of parents' PTAs on the probability of being culled for each of the reasons--raised questions about the utility of classifying culling reasons according to the voluntary nature of the culling decision. We concluded that Michigan producers are not using parents' genetics in heifer-culling decisions.

Animal Husbandry↗
PubMed2000

Evaluating the economic and noneconomic impacts of the veterinary medical profession in Michigan.

This study reaffirms the diversity and breadth of the veterinary profession. As it turns out, some of the furthest-reaching impacts of the veterinary medical profession were largely non-quantifiable. The veterinary medical profession had a substantial direct economic impact in Michigan during 1995. The total economic contribution of the veterinary medical profession to Michigan during 1995 that was attributable to expenditures on salaries, supplies, services, and their multiplier effect was approximately $500 million. In addition, the profession was associated with nearly 8,500 jobs (combined professional and lay positions). The veterinary medical profession was also considered to have an impact on the prosperity of the live-stock, equine, and pet food industries in Michigan, even though the economic contribution in these areas could not be directly quantified. Economic well-being of the individual businesses in these industries is directly related to the health and productivity of the associated animals, and improvements in output or productivity that accompany improved animal health likely carry substantial economic benefits in these sectors. In addition, progressive animal health management provides a crucial method of managing risk in the animal industries. Similarly, although the economic contribution could not be quantified, the veterinary medical profession enhances the safety and quality of human food through research, regulation, and quality assurance programs in livestock production, minimizing the risk of drug residues and microbial contamination. During 1995, approximately 5.3 million Michigan residents benefitted from the physical, psychological, and emotional well-being that accompanies companion animal ownership. By preserving the health and longevity of companion animals, veterinarians sustain and enhance these aspects of the human-animal bond. As Michigan enters a new century, it is likely that the state's veterinary medical profession will continue to make a highly valued societal contribution. Pets, equines, and food animals will continue to have prominent roles in Michigan for the foreseeable future, as will the human-animal bond, food safety, and medical research. Clearly, for economic and noneconomic reasons, it will be in the interest of the people of Michigan to seek opportunities to maintain and enhance the vitality of the state's veterinary medical profession. It was our hope that results of this study would provide university administrators, legislators, MVMA executives, and others with information needed to justify the ongoing provision of public support for the veterinary medical profession. In addition, we expect that the results will supply useful material for public relations and marketing campaigns by the MVMA and the Michigan State University College of Veterinary Medicine and will provide the media with public interest stories to promote the veterinary profession. Although this study considered the economic and noneconomic impacts of the veterinary medical profession only in Michigan, the results can provide an important reference point for educators, policy markers, and legislators in other states. In addition, this study could serve as a methodologic model for veterinary organizations in other states, or at the national level, to emulate.

Animals↗
PubMed1999

Spatial and temporal distribution of selected canine cancers in Michigan, USA, 1964-1994.

Although rates are commonly used to compare regional disease occurrence, rate-independent methods might also be useful in circumstances where geographic occurrence of a disease is known, but calculation of disease rates is not feasible. This is frequently the case for diseases in companion animals, where accurate enumeration of populations-at-risk is often arduous. This study had two objectives: to demonstrate a rate-independent method for investigating disease aggregation in companion animals; and, to assess the spatial and temporal clustering of canine cases of four cancers that are biologically similar in dogs and humans. Geographic information systems and point-pattern analysis were used to assess the spatial and temporal clustering of incident cases of four types of canine cancer in three counties in Michigan between 1964 and 1994, and to generate hypotheses concerning disease aggregation. Significant (P < or = 0.01) spatial clustering was found that varied by county and cancer type. No definitive temporal patterns could be deduced from a temporal analysis of the cases of canine cancer in this study. These results demonstrate distance-based methods for assessing clustering of disease, and suggest that processes determining the aggregation of canine cancer cases do not act in a spatially uniform manner.

Animals↗
PubMed1999

Herd-level economic analysis of the impact of paratuberculosis on dairy herds.

OBJECTIVE: To perform a herd-level analysis of economic losses associated with paratuberculosis in dairy herds. DESIGN: Cross-sectional study. SAMPLE POPULATION: A multistage stratified random sample of 121 dairy herds in Michigan. PROCEDURE: A 2-part questionnaire was used to gather data on management practices, herd productivity, labor use, and expenditures. Blood samples were collected from a random sample of cows > or = 2 years old in each herd and tested for antibodies to Mycobacterium paratuberculosis. A herd was considered negative for paratuberculosis if results for all cows tested were negative. Multivariable linear regression was used to evaluate the data. RESULTS: A 10% increase in proportion of cows positive for paratuberculosis was associated with a 33.4 kg (73.5 lb) decrease in mean weight of culled cows. Mortality rate among herds positive for paratuberculosis was 3% higher than rate among herds negative for paratuberculosis. Herds positive for paratuberculosis did not have a significantly higher annual number of hours of labor per cow than did herds negative for paratuberculosis. CLINICAL IMPLICATIONS: For a herd of average size and cull rate, the reduction in mean weight of culled cows attributable to paratuberculosis represented a loss of approximately $1,150 annually for each 10% increase in herd prevalence of paratuberculosis. The increased mortality rate attributable to paratuberculosis represented a loss of between $1,607 and $4,400 on the basis of lost slaughter value and cost of replacement heifers.

Animals↗
PubMed1999

Recombinant bovine somatotropin: association with reproductive performance in dairy cows.

A clinical trial was performed to determine the effect of bST on reproductive performance in dairy cows on 4 Michigan dairy farms when bST was used according to labeled directions. Holstein cows (n = 555) at 4 Michigan dairy farms were randomly assigned to receive bovine somatotropin (bST) or to serve as untreated controls. Bovine somatotropin (500 mg, s.c.) was administered every 14 d beginning at 63 to 69 d of lactation and continuing until approximately 21 d prior to the end of lactation or until the producer removed the animal from the herd. A total of 229 (42.57%) animals consisting of 112 (48.91%) controls and 117 (51.09%) bST-treated cows were not diagnosed pregnant and were considered as having reproductive failure by 150 d of lactation and 92 (17.10%) of the animals consisting of 45 (48.91%) controls and 47 (51.09%) bST-treated cows had reproductive failure at the end of their lactation. No significant difference in the incidence of reproductive failure existed between the study treatment groups during either time frame. Cows with cystic ovarian disease had more instances of reproductive failure at 150 d of lactation than cows without this disease. Cows with dystocia, twin births, metritis, displaced abomasum and cystic ovarian disease had more instances of reproductive failure by the end of lactation than cows without these diseases. The bST-treated cows developed more nonspecific off feed conditions during the study lactation and had more twin births at the calving following bST administration compared to control cows. No differences were found between the study treatment groups in calculations of reproductive parameters. Logistic regression analysis found no significant effect of bST on reproductive failure; the odds ratios for the bST treatment effect on reproductive failure at 150 d of lactation and reproductive failure at the end of lactation were 0.95 (95% CI 0.67 to 1.36) and 0.95 (95% CI 0.59 to 1.54), respectively. Overall, bST was not found to have a significant impact on reproductive performance in the herds studied.

Abortion, Veterinary↗
PubMed1999

A comparison of profitability and economic efficiencies between management-intensive grazing and conventionally managed dairies in Michigan.

A retrospective cohort study was designed to determine differences in profitability, asset efficiency, operating efficiency, and labor efficiency between Michigan dairy farms implementing management-intensive grazing (MIG) and conventionally managed dairy farms. Financial information and labor use data for the calendar year 1994 were collected with surveys and personal interviews from 35 MIG dairies and 18 conventionally managed dairies. Because the geographic distribution of MIG and conventionally managed farms in this study did not include Michigan's "dairy belt," extrapolation of these results to an average Michigan or Midwest dairy should be made with care. Within the areas represented, however, multivariate linear regression indicated that MIG dairies had more economic profit than conventionally managed dairies. They captured this profit by being more efficient in asset use, operating practices, and labor use. These results suggest that MIG could provide a sustainable alternate management tool for portions of Michigan's dairy industry.

Analysis of Variance↗
PubMed1999

Evaluation of certification in the Milk and Dairy Beef Quality Assurance Program and associated factors on the risk of having violative antibiotic residues in milk from dairy farms in Michigan.

OBJECTIVE: To determine whether certification in a Milk and Dairy Beef Quality Assurance Program (MDBQAP) was associated with a reduced risk of having antibiotic residues in milk and to define specific management factors that may have predisposed dairy farms to having violative antibiotic residues in milk. SAMPLE POPULATION: 124 dairy farms in Michigan that had > 1 violative residue in milk during 1993 and 248 randomly selected control farms in Michigan that did not have violative residues in milk during 1993. PROCEDURE: A pretested structured questionnaire was mailed to case and control farms. A conditional multivariate logistic regression model was developed to determine risk factors associated with having a violative antibiotic residue in milk. RESULTS: Certification in the MDBQAP did not significantly reduce the risk of having a violative antibiotic residue. Annual treatment of > 10% of a herd for metritis was associated with a reduced risk of having a violative residue. Evidence suggested that a routine request for a milk processor to perform residue testing was associated with a decreased risk of having had a violative antibiotic residue, but routine on-farm residue testing was associated with an increased risk of having had a residue. CONCLUSIONS AND CLINICAL RELEVANCE: MDBQAP certification was associated, although not significantly, with a reduced risk of having violative antibiotic residues in milk. Risk factors significantly associated with violative antibiotic residues are addressed by various critical control points in the MDBQAP and may be indicators for strengths and weaknesses of MDBQAP.

Animals↗
PubMed1998

Association of sex of fetus, sire, month of conception, or year of foaling with duration of gestation in standardbred mares.

OBJECTIVE: To determine whether sex of fetus, sire, month of conception, or year of foaling was associated with duration of gestation in mares. DESIGN: Epidemiologic retrospective cohort study. ANIMALS: 500 foalings for 296 Standardbred mares. PROCEDURE: Data for reproductive events from 1986 to 1992 were analyzed. Analyses were conducted to determine whether duration of gestation was associated with sex of fetus, sire, month of conception, or year of foaling. RESULTS: Mean duration of gestation was 343.3 days and was significantly greater for colt fetuses (344.4 days) than for filly fetuses (342.2 days). Sire was associated with duration of gestation; gestation after mating with certain sires was consistently less than 340 days in duration, whereas duration after mating with other sires was consistently more than 350 days. Duration of gestation was associated with month of conception, decreasing by about 2.5 d/mo for mares conceiving later during the breeding season. CLINICAL IMPLICATIONS: Duration of gestation is affected by mating to specific sires and by month of conception. Stallions associated with exceptionally prolonged gestations might be used to breed mares early in the breeding season, whereas stallions associated with shorter gestations might be desirable for mares bred later in the breeding season. Preparations for impending parturition should be more effective and efficient with improved information on expected date of parturition.

Animals↗