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Biomedical subjects

J M Gay

Publications and source records attributed to J M Gay.

At least 19 recordsLinked to original sources
PubMed2003

Effects of biotin supplementation on performance and claw lesions on a commercial dairy farm.

A controlled 14-mo field trial was conducted to evaluate the effect of biotin supplementation on hoof lesions, milk production, and reproductive performance in a commercial dairy herd. One hundred seventy cows were studied and supplemented with either 0 or 20 mg/d of biotin by computer feeder. All were housed in the same free-stall facility with the same environment, base diet, and management. The feet of 99 cows were trimmed three times at 6-mo intervals, and hoof health was evaluated. Milk production and fertility data were captured monthly by the Dairy Herd Improvement Association. At the final hoof trimming, sole hemorrhages were significantly higher in control (50%) vs. biotin-supplemented animals (24%). The incidents of cows affected with double soles, hoof wall grooves, and heel horn erosion did not differ between control and biotin-supplemented animals. Biotin supplementation of trimmed cows resulted in 878 kg more milk than control cows when compared with previous lactation yield (n = 46 biotin supplemented, n = 48 control cows). At the end of the study, for both trimmed and untrimmed animals, biotin supplemented cows (n = 81) produced 481 kg more milk and 25 kg more fat than the controls (n = 81). There was no interaction between biotin supplementation and hoof trimming on milk production. There were variations in the response of fertility to biotin between age groups. First lactation heifers fed supplemental biotin had significantly fewer days from calving to conception and required fewer inseminations per pregnancy than controls of the same parity.

Animal Nutritional Physiological Phenomena↗
PubMed2002

Use of pulsed-field gel electrophoresis for detecting differences in Staphylococcus aureus strain populations between dairy herds with different cattle importation practices.

The hypothesis tested was that dairy herds which import cattle for replacement or expansion have a higher prevalence of Staphylococcus aureus mastitis and a greater number of new Staphylococcus aureus strains enter their herds than closed herds. Fifteen commercial dairy herds were divided into four groups based on cattle importation practices. Composite foremilk samples were collected at 4-monthly intervals for 1 year from all lactating cattle. Additionally, foremilk samples were collected from cattle at parturition and skin swabs were taken from the udder of primiparous heifers. All samples were cultured for Staphylococcus aureus and isolates were strain-typed using pulsed-field gel electrophoresis. Herds that purchased replacement heifers had a higher prevalence of Staphylococcus aureus mastitis than herds that purchased lactating cattle for expansion (P = 0.02). Herds that purchased replacement heifers had more total strains of Staphylococcus aureus (P = 0.01) and more new strains (P = 0.04) enter the herd than closed herds.

Animal Husbandry↗
PubMed2002

Influence of Staphylococcus aureus strain-type on mammary quarter milk somatic cell count and N-acetyl-beta-D-glucosaminidase activity in cattle from eight dairies.

The hypothesis tested was that there are differences in pathogenicity between strains of Staphylococcus aureus that cause bovine mastitis. Mammary quarter milk somatic cell count (SCC) and N-acetyl-beta-D-glucosaminidase (NAGase) activity were used as indicators of the pathogenicity of different strains of S. aureus that infect the bovine udder. Eight commercial dairy herds with a history of S. aureus in bulk tank milk cultures were studied. Initially, composite foremilk samples were collected from all lactating cattle in each herd and cultured for staphylococci. Subsequently, all cows with a coagulase-positive staphylococcal intramammary infection (IMI) at the initial sampling that were still present in the herd of origin had individual mammary quarter foremilk samples collected. Coagulase-positive staphylococcal isolates were confirmed as S. aureus using a commercial biotyping system. Staphylococcus aureus isolates were strain-typed using pulsed-field gel electrophoresis. Mammary quarter milk SCC and N-acetyl-beta-D-glucosaminidase activity were determined for each cow. The difference in mean somatic cell count and mean NAGase activity for mammary quarters infected with the same strain of S. aureus and for uninfected quarters on the same cow was calculated. One-way analysis of variance was used to assess differences between strains within a herd. Overall, no significant differences were found between strains, suggesting that the degree of udder parenchymal injury induced by S. aureus IMI is in general significantly affected by factors other than strain type.

Acetylglucosaminidase↗
PubMed2001

Ivermectin sensitivity in collies is associated with a deletion mutation of the mdr1 gene.

A subpopulation of collie dogs is extremely sensitive to neurotoxicity induced by ivermectin. The aim of this study was to determine the mechanistic basis for this phenomenon. The multi-drug-resistance gene (mdr1) encodes a large transmembrane protein, P-glycoprotein (P-gp), that is an integral part of the blood-brain barrier. P-gp functions as a drug-transport pump at the blood-brain barrier, transporting a variety of drugs from the brain back into the blood. Since ivermectin is a substrate for P-gp, we hypothesized that ivermectin-sensitive collies had altered mdr1 expression compared with unaffected collies. We report a deletion mutation of the mdr1 gene that is associated with ivermectin sensitivity. The 4-bp deletion results in a frame shift, generating several stop codons that prematurely terminate P-gp synthesis. Dogs that are homozygous for the deletion mutation display the ivermectin-sensitive phenotype, while those that are homozygous normal or heterozygous do not display increased sensitivity to ivermectin.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2001

Effects of changes in power setting of an ultrasonic aspirator on amount of damage to the cerebral cortex of healthy dogs.

OBJECTIVE: To determine the minimal ultrasonic aspirator pressure necessary to damage the cerebral cortex of healthy dogs. ANIMALS: 9 mixed-breed dogs. PROCEDURE: The study comprised 2 parts. In part A, 6 dogs were euthanatized immediately prior to the experiment. In part B, 3 dogs were anesthetized for recording of physiologic variables. In both parts, craniectomy and durotomy were performed to bilaterally expose the lateral aspect of the cerebral cortex. An ultrasonic aspirator was placed in contact with various areas of the cerebral cortex, and aspirator power was altered (10, 20, 30, and 40%). Duration of contact at each power was 5 and 10 seconds. Subsequently, gross morphologic and histologic damage was assessed in the cortex. RESULTS: Gross observations for all dogs were similar. At 10% power, visible or histologic damage was not evident in the cortex. At 20% power, the cortex was slightly indented from contact with the hand piece; however, cortical disruption was not evident. Cortical disruption was initially detectable at 30% power in some dogs and was consistently evident at 40% power in both sets of dogs. CONCLUSIONS AND CLINICAL RELEVANCE: Ultrasonic aspirator power of < 20% created minimal acute morphologic damage to the cortex. Power settings between 20 and 30% may superficially damage the cerebral cortex in healthy dogs, whereas 40% power consistently damages the cerebral cortex. Knowledge of the degree of damage to cerebral cortex caused by various amounts of power for ultrasonic aspirators will allow surgeons to avoid damaging normal brain tissues during surgery.

Animals↗
PubMed2000

Neospora caninum seroprevalence and associated risk factors in beef cattle in the northwestern United States.

A Neospora caninum seroprevalence and risk factor survey of 2585 cows was conducted in 55 beef cow-calf herds located in five northwestern states of the USA. Blood samples were collected by private veterinary practitioners and management practices were surveyed using a mail questionnaire. Producers were randomly selected from those that employed these veterinarians to perform annual herd pregnancy examinations. Questions were asked about animal management, grazing and feeding, immunization and record keeping practices. Blood was collected from a systematically selected sample of cows in each herd, and age, origin, and pregnancy status were recorded. Blood samples were analyzed for antibodies against N. caninum antigen using a monoclonal antibody-based competitive inhibition (CI) ELISA. Overall seroprevalence was 24% and within herd seroprevalence ranged from 3 to 67% with a median of 19%. Within herd seroprevalence and mean inhibition percentage were different between the five states. Herds that managed their cows on range for summer grazing had lower seroprevalence than those that did not, while increased seroprevalence was associated with higher winter stocking density. Cows less than 3 years of age had higher CI ELISA inhibition percent values than cows greater than 6 years of age. No relationship was noted between serologic status and individual cow origin (purchased or raised), or pregnancy status at the time of sampling.

Animals↗
PubMed2000

Multiresistant Salmonella Typhimurium DT104 infections of humans and domestic animals in the Pacific Northwest of the United States.

Salmonella Typhimurium definitive type 104 with chromosomally encoded resistance to five or more antimicrobial drugs (R-type ACSSuT+) has been reported increasingly frequently as the cause of human and animal salmonellosis since 1990. Among animal isolates from the northwestern United States (NWUS), R-type ACSSuT+ Typhimurium isolates increased through the early 1990s to comprise 73% of Typhimurium isolates by 1995, but subsequently decreased to comprise only 30% of isolates during 1998. NWUS S. Typhimurium R-type ACSSuT+ were consistently (99%) phage typed as DT104 or the closely related DTu302. S. Typhimurium isolates from cattle with primary salmonellosis, randomly selected from a national repository, from NWUS were more likely to exhibit R-type ACSSuT+ (19/24, 79%) compared to isolates from other quadrants (17/71, 24%; P < 0.01). Human patients infected with R-type ACSSuT+ resided in postal zip code polygons of above average cattle farm density (P < 0.05), while patients infected with other R-types showed no similar tendency. Furthermore, humans infected with R-type ACSSuT+ Typhimurium were more likely to report direct contact with livestock (P < 0.01) than humans infected with other R-types.

Animals↗
PubMed2000

Identification of DT104 and U302 phage types among Salmonella enterica serotype typhimurium isolates by PCR.

A DNA sequence was identified in isolates of Salmonella enterica serotype Typhimurium definitive type 104 (DT104). The PCR amplification of an internal segment of this sequence identified DT104 and the closely related U302 phage type among 146 isolates of S. enterica serotype Typhimurium tested, thus providing a tool for rapid identification of DT104 and related isolates.

Animals↗
PubMed1999

Fecal Escherichia coli O157:H7 shedding patterns of orally inoculated calves.

To assess the duration of fecal shedding upon initial infection, the duration of shedding after subsequent re-infection and the effects of dietary restriction and antibiotic treatment on shedding recrudescence, four, one-week-old calves were orally inoculated on three separate occasions with 5x10(8) cfu of Escherichia coli O157:H7 strain 86-24 Nal-R. Fecal shedding was followed by serial culture three times weekly. Following the first inoculation, the calves shed E. coli O157:H7 in their feces for a mean of 30 days, with a range of 20 to 43 days. Following the second and third inoculations, the calves shed E. coli O157:H7 in their feces for 3-8 days. In each of the three inoculations, feed was withheld from the calves for 24 h after they had become fecal culture negative. Two calves resumed shedding, one for 1 day and the other for 4 days, after food was withheld after the third inoculation, but not in the first two inoculations. In the third inoculation, one calf resumed shedding for one day after treatment with oxytetracycline. No E. coli O157:H7 strain 86-24 Nal-R was found in the calves at necropsy. These calves did not exhibit persistent low-level shedding, and did not appear to be persistently colonized with E. coli O157:H7.

Animals↗
PubMed1998

Sources of intramammary infections from Staphylococcus aureus in dairy heifers at first parturition.

The study objective was to identify probable sources and modes of transmission of 91 Staphylococcus aureus isolates obtained from the colostrum of 76 heifers at parturition. Sources cultured were milk (including colostrum), heifer body sites (teats, muzzle, rectum, vagina, and lacteal secretions), and environmental sites (bedding, insects, housing, water, feedstuffs, humans, nonbovine animals, air, and equipment). Staphylococcus aureus isolates were characterized by 63 phenotypic traits. A similarity coefficient was calculated by herd to identify the S. aureus that most closely resembled the S. aureus obtained from heifer colostrum. Staphylococcus aureus from a heifer's colostrum was compared with all preexisting S. aureus isolates from that heifer's herd. Isolates that were > or = 90% similar were considered to be identical. Because 30 (of the 91) S. aureus isolates from heifer colostrum were collected prior to environmental sampling, only 61 S. aureus isolates from heifer colostrum were available for comparison among all three sources. Possible sources of S. aureus from heifer colostrum at parturition were milk (70%, 43 of 61 isolates), heifer body sites (39%, 24 of 61), environmental sites (28%, 17 of 61), or no identified source (16%, 10 of 61). Three heifers with intramammary infection (IMI) from S. aureus at parturition had the same S. aureus on their teats prior to parturition. Milk was the only source identified for 41% (25 of 61) of isolates from heifer colostrum. Isolates from heifer body sites were the only source identified for 5% (3 of 61) of heifer colostrum isolates. Staphylococcus aureus from the environment was never the sole possible source for S. aureus from heifer colostrum. Data suggest that the major sources of S. aureus IMI in heifers at parturition are milk and heifer body sites. Contact among heifers may be an important mode of transmission of S. aureus leading to IMI in heifers at parturition.

Animals↗
PubMed1996

Commingled grazing as a risk factor for trichomonosis in beef herds.

OBJECTIVE: To evaluate commingled grazing on public lands as a risk factor for Tritrichomonas foetus infection in beef herd bulls. DESIGN: Case-control study. SAMPLE POPULATION: Based on 1994 data from the mandatory Idaho bull testing program, all 65 infected herds (case herds), 78 randomly selected test-negative herds that tested < 10 nonvirgin bulls, and 81 randomly selected test-negative herds that tested > or = 10 nonvirgin bulls (control herds). PROCEDURE: Managers of government-owned grazing lands in Idaho identified producers who had grazing permits for an allotment under their jurisdiction in 1993 and for that allotment recorded the number of animals the producer was permitted to graze on the allotment, the number of herds with grazing permits, the total number of animals permitted, and the dates on which grazing began and ended. The number of bulls tested, number of times tested, and test results were collated from the testing database. RESULTS: The relative sensitivity of bacterial culture of preputial smegma was 81%. The attributable fraction of T foetus infection associated with commingled grazing was 33%, and the odds ratio of infection was 9.0 for herds commingled with > or = 14 other herds. The total number of animals permitted on an allotment, the use of public lands, and type of public lands used were not significantly associated with infection status. CLINICAL IMPLICATIONS: These results suggest that to control the spread of trichomonosis, the number of herds commingling on a grazing allotment should be minimized and commingled herds should be managed collectively.

Animal Husbandry↗
PubMed1996

Veterinary involvement in management practices of beef cow-calf producers.

Management practices of 53 beef cow-calf producers were surveyed by use of a mail questionnaire. Producers were randomly selected from those who employ veterinarians to perform herd pregnancy examinations. Questions were asked about animal management, grazing and feeding, vaccination, and record-keeping practices. Median herd size was 250 breeding cows, and 2,329 of 2,491 (93%) randomly sampled cows in these herds were pregnant. Less than half of producers associated with these herds reported adoption of many beneficial practices related to bull management, infectious disease management, nutrition, and individual-animal record keeping, suggesting that a considerable number of producers are missing opportunities to optimize production and, thus, economic return. Use of individual-animal production records, which would enable more objective decision making on the basis of production and economic data, was not widespread. These findings suggested that veterinarians serving beef ranches have opportunities to provide additional services incorporating these management practices.

Animal Husbandry↗
PubMed1996

Environmental reservoirs for Serratia marcescens intramammary infections in dairy cows.

Via special media, Serratia marcescens isolates were found in 3 bedding pack samples and in 2 milking parlor floor samples, and in milk samples from 19 cows during an episode of mastitis in a dairy cow herd. Chromosomal digest patterns of isolated S marcescens were indistinguishable for 18 of the milk samples and all bedding pack samples. Our findings provide strong evidence that the bedding pack was the reservoir of S marcescens associated with the outbreak of intramammary infections. Additionally, our ability to match digest patterns of isolates in the bedding pack and milk confirms the theory that S marcescens is an environmental pathogen capable of causing mastitis.

Animals↗
PubMed1996

Serological diagnosis of bovine neosporosis by Neospora caninum monoclonal antibody-based competitive inhibition enzyme-linked immunosorbent assay.

Neospora caninum, a protozoan parasite closely related to Toxoplasma gondii, causes abortion and congenital infection in cattle. To investigate specific methods of antemortem diagnosis, the antibody responses of infected cows were evaluated by immunoblot assay and competitive inhibition enzyme-linked immunosorbent assay (CI-ELISA) by using a monoclonal antibody (MAb), MAb 4A4-2, against N. caninum tachyzoites. MAb 4A4-2 bound diffusely to the exterior surface of N. caninum tachyzoites and recognized a single 65-kDa band in immunoblots. MAb 4A4-2 was unreactive to antigens of two closely related apicomplexan protozoa, Toxoplasma gondii and Sarcocystis cruzi. Binding of MAb 4A4-2 was inhibited by mild periodate treatment of N. caninum antigen, demonstrating the carbohydrate nature of the epitope. Immunoblot analysis of N. caninum tachyzoite antigens with sera from cows with confirmed Neospora-induced abortion revealed at minimum 14 major antigens ranging from 11 to 175 kDa. Although the recognized antigens varied from cow to cow, antigens of 116, 65, and 25 kDa were detected in all cows with abortion confirmed to be caused by N. caninum. The binding of MAb 4A4-2 to N. caninum tachyzoite antigen was consistently inhibited by sera from Neospora-infected cows in a CI-ELISA format and was not inhibited by sera from Neospora antibody-negative cows. Furthermore, sera from cattle experimentally infected with T. gondii, S. cruzi, Sarcocystis hominis, or Sarcocystis hirsuta, which had cross-reactive antibodies recognizing multiple N. caninum antigens by immunoblot assay, did not inhibit binding of MAb 4A4-2 in the CI-ELISA. Thus, MAb 4A4-2 binds a carbohydrate epitope on a single N. caninum tachyzoite surface antigen that is recognized consistently and specifically by Neospora-infected cattle.

Abortion, Veterinary↗
PubMed1996

Serologic responses of cattle and other animals infected with Neospora caninum.

OBJECTIVE: To examine cross-reactivity among Neospora caninum and closely-related apicomplexans. DESIGN: Sera from animals were examined for antibody production to N caninum and cross-reactivity to Toxoplasma gondii. ANIMALS: Cattle were experimentally infected with 3 tissue cyst-forming protozoan parasites N caninum, T gondii, and Sarcocystis sp, and calves were monospecifically inoculated with the intestinal coccidia, Eimeria bovis and Cryptosporidium parvum. Similar studies were done in laboratory rabbits inoculated with N caninum, T gondii, Hammondia hammondi, and Sarcocystis sp. Additionally, sera were obtained from ewes, lambs, goats, sows, cats, rats, and mice inoculated with N caninum tachyzoites. PROCEDURE: The indirect fluorescent antibody (IFA) and ELISA antibody tests (cattle only) were used to examine reactivity to N caninum; the modified direct agglutination, Sabin-Feldman dye, and IFA tests were used to evaluate reactivity to T gondii. RESULTS: Serologic cross-reactivity among N caninum, T gondii, and Sarcocystis sp was none or minimal by the IFA test. There was some reactivity to N caninum by the use of ELISA in cattle inoculated with Sarcocystis sp. CONCLUSIONS: The IFA test for N caninum was specific for the diagnosis of neosporosis in animals.

Animals↗
PubMed1996

Prevalence of coagulase-positive staphylococci, other than Staphylococcus aureus, in bovine mastitis.

OBJECTIVE: To determine prevalence and relevance of coagulase-positive Staphylococcus hyicus and S intermedius intramammary infections (IMI) in dairy cows and determine the ability of the 4-hour tube coagulase (TC) test to differentiate the coagulase-positive staphylococci (CPS). DESIGN: Prevalence of CPS was determined for primiparous cows (point prevalence and prevalence at first parturition) and multiparous cows (point prevalence) of 2 herd groups: < 6% CPS IMI prevalence = low prevalence (LP); > 10% CPS IMI prevalence = high prevalence (HP). SAMPLE POPULATION: For prevalence, cows of 22 dairy herds. For TC, 1,038 CPS strains isolated from cow milk. PROCEDURE: Speciation of CPS from aseptically collected composite milk samples was performed. Coagulase-positive isolates from 4 cow groups were tested for their ability to coagulate rabbit plasma by 4 hours: LP and HP primiparous cows at parturition, and LP and HP cows any time after first parturition. RESULTS: Of 487 CPS in the prevalence study, 82.1% were S aureus, 17.7% were coagulase-positive S hyicus, and 0.2% were S intermedius. Of all CPS IMI in LP herds, 34% were coagulase-positive S hyicus; of all CPS IMI in HP herds, 9% were coagulase-positive S hyicus. Coagulase-positive S hyicus appeared to persist to the end of lactation in 4 cows (mean linear somatic cell count = 3.7). The TC test was > or = 97% sensitive, < or = 33% specific, and had a predictive value positive range of 60 to 97% for S aureus isolates. CONCLUSION: Coagulase-positive S hyicus appears capable of inducing chronic, low-grade IMI. Staphylococcus intermedius does not appear to be an important mastitis pathogen. The TC test is not valid to use as the sole method to differentiate CPS species.

Animals↗