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  • Author or Editor: Ian R. Dohoo x
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Objective—To investigate the sensitivity and specificity of results of initial and repeated milk ELISAs (at 6- or 12-month intervals) to detect cows that were shedding Mycobacterium avium subsp paratuberculosis (ie, were infectious) and to evaluate factors influencing the probability that the results of a repeated milk ELISA would be positive for an infectious cow if the results of the initial milk ELISA were negative.

Design—Prospective cohort study.

Animals—3,145 dairy cows from 32 herds.

Procedures—Herds from the 3 Maritime provinces in Canada (Prince Edward Island, New Brunswick, and Nova Scotia), participating in a Dairy Herd Improvement program, and that had undergone a prior Mycobacterium avium subsp paratuberculosis awareness project were selected for the study. Sample collection occurred between April 2009 and March 2011 with milk and fecal samples collected from all lactating cows in study herds every 6 months. Herds completing < 3 herd visits with collection of individual cow fecal or milk samples, within this sampling timeframe, were excluded from analyses. Fecal samples were cultured in liquid medium and a cow was defined as infectious if ≥ 1 sample was culture positive (reference test). A milk ELISA (index test) was completed with a commercial kit, following manufacturer's instructions.

Results—For a 6-month test interval, sensitivities of the milk ELISA to detect infectious cows were 22.0% and 32.6% for initial and combined initial and repeated tests (parallel interpretation), respectively. Specificity of the initial ELISA was 99.6% and was 99.2% for combined tests. For a 12-month test interval, sensitivities of the milk ELISA to detect infectious cows were 25.6% and 45.3% for initial and combined initial and repeated tests (parallel interpretation), respectively. Specificity of the initial ELISA was 99.6% and was 98.9% for combined tests. In infectious cows, magnitude of the initial negative ELISA result was a positive predictor for a positive repeated ELISA result.

Conclusions and Clinical Relevance—Results of a repeated milk ELISA improved detection of Mycobacterium avium subsp paratuberculosis infectious cows, with minimal loss of specificity. A 12-month test interval provided a greater increase in sensitivity, relative to an initial test, than did a 6-month interval. Infectious cows with an initial negative milk ELISA result close to the cutoff for a positive test were more likely to have positive results on a repeated ELISA. Repeated testing improved detection of infectious cows and reduced risk of misclassification compared with a single ELISA result.

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in Journal of the American Veterinary Medical Association


Objective—To determine whether half-udder intramammary infusion of cloxacillin results in transfer of cloxacillin from treated to untreated mammary gland quarters within nonlactating cows, and, if so, at what concentrations, and to determine whether selection of ipsilateral versus diagonal-contralateral quarters for treatment affects cloxacillin transfer among quarters.

Animals—20 Holstein-Friesian cows from a dairy herd.

Procedures—A within-cow half-udder comparison trial was used in which 2 of 4 mammary gland quarters (ipsilaterally or diagonally) received an intramammary infusion of cloxacillin on day 1 of the nonlactating period. Three days later, milk samples were taken from all untreated quarters and high-pressure liquid chromatography was used to detect and quantify milk cloxacillin concentrations.

Results—Cloxacillin was detected in 25% of all untreated mammary gland quarters. Mean cloxacillin concentration in untreated quarters was below minimum inhibitory concentrations for targeted mastitis pathogens. No significant difference in cloxacillin concentrations was found in the ipsilateral or diagonal treatment groups.

Conclusions and Clinical Relevance—Within-cow half-udder comparison trials are valid for antimicrobial trials in nonlactating cows, although transfer of antimicrobials does occur in trace concentrations. Ipsilateral or diagonal-contralateral treatment designs perform similarly. This type of design is economical for researchers, although care must be taken to account for within-cow clustering of mammary gland quarter data.

Full access
in American Journal of Veterinary Research


Objective—To compare the owner-reported prevalence of behavioral characteristics in dogs obtained as puppies from pet stores with that of dogs obtained as puppies from noncommercial breeders.

Design—Cross-sectional study.

Animals—Dogs obtained as puppies from pet stores (n = 413) and breeder-obtained dogs (5,657).

Procedures—Behavioral evaluations were obtained from a large convenience sample of current dog owners with the online version of the Canine Behavioral Assessment and Research Questionnaire, which uses ordinal scales to rate either the intensity or frequency of the dogs’ behavior. Hierarchic linear and logistic regression models were used to analyze the effects of source of acquisition on behavioral outcomes when various confounding and intervening variables were controlled for.

Results—Pet store–derived dogs received significantly less favorable scores than did breeder-obtained dogs on 12 of 14 of the behavioral variables measured; pet store dogs did not score more favorably than breeder dogs in any behavioral category. Compared with dogs obtained as puppies from noncommercial breeders, dogs obtained as puppies from pet stores had significantly greater aggression toward human family members, unfamiliar people, and other dogs; greater fear of other dogs and nonsocial stimuli; and greater separation-related problems and house soiling.

Conclusions and Clinical Relevance—Obtaining dogs from pet stores versus noncommercial breeders represented a significant risk factor for the development of a wide range of undesirable behavioral characteristics. Until the causes of the unfavorable differences detected in this group of dogs can be specifically identified and remedied, the authors cannot recommend that puppies be obtained from pet stores.

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in Journal of the American Veterinary Medical Association


Objective—To determine whether insertion of an internal teat sealer (ITS) at the end of lactation would prevent development of new intramammary infections (IMIs) during the nonlactating period.

Design—Controlled clinical trial.

Animals—939 Holstein-Friesian dairy cows from 16 herds.

Procedures—Results of bacteriologic culture of milk samples collected 14 days prior to the end of lactation were used to assign cows to groups (group 1 = negative results for all quarters; group 2 = positive results for ≥ 1 quarter). Quarters of cows in group 1 were treated with an ITS or a single intramammary dose of cloxacillin; quarters of cows in group 2 were treated with cloxacillin in conjunction with an ITS or with cloxacillin alone. Milk samples were collected at the end of lactation and within 8 days after calving.

Results—Regardless of whether the outcome of interest was new IMIs caused by any pathogens, major pathogens, environmental pathogens, or streptococci other than Streptococcus agalactiae, quarters in group 2 treated with both cloxacillin and an ITS were less likely to develop a new IMI than were quarters treated with cloxacillin alone. For cows in group 1, no significant difference in risk of new IMIs was found between treatments.

Conclusions and Clinical Relevance—Results suggest that for dairy cattle with an IMI late in the lactation period, intramammary administration of cloxacillin at the end of lactation followed by insertion of an ITS enhanced protection against development of new IMIs, compared with use of cloxacillin alone.

Restricted access
in Journal of the American Veterinary Medical Association