Jean-Philippe Roy

South Dakota State University, Brookings, South Dakota, United States

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Publications (9)12.41 Total impact

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    ABSTRACT: The objectives of this study were to propose benchmarks for the interpretation of herd udder health using monthly individual somatic cell counts (SCC) from dairy herds in Quebec, Canada and to evaluate the association of risk factors with intramammary infection (IMI) dynamics relative to these benchmarks. The mean and percentiles of indices related to udder infection status [e.g., proportion of healthy or chronically infected cows, cows cured and new IMI (NIMI) rate] during lactation and over the dry period were calculated using a threshold of ≥ 200 000 cells/mL at test day. Mean NIMI proportion and proportion of cows cured during lactation were 0.11 and 0.27. Benchmarks of 0.70 and 0.03 for healthy and chronically infected cows over the dry period were proposed. Season and herd mean SCC were risk factors influencing IMI dynamics during lactation and over the dry period.
    The Canadian veterinary journal. La revue vétérinaire canadienne. 08/2014; 55(8):741-8.
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    ABSTRACT: Few studies have investigated the efficacy of extended ceftiofur therapy and none have focused on extended therapy for naturally occurring clinical mastitis. The objective of this study was to compare the efficacy of extended intramammary ceftiofur therapy of 8 d duration with a standard 2-day regimen for the treatment of naturally occurring mild to moderate clinical mastitis in lactating dairy cows. Holstein cows from 22 dairy herds (n = 241) were randomly allocated to the 2 treatment groups. For each case of mastitis, 125 mg of ceftiofur hydrochloride was administered intramammary once a day for 2 or 8 d. Clinical cure, 21 d after the last treatment, was 89% (98/110) in each group. Bacteriological cure 21 d after the last treatment for the 2- and 8-day regimens were 32% (15/47) and 61% (25/41), respectively, for all bacteria (P = 0.007), 64% (9/14) and 82% (9/11), respectively, for streptococci (P = 0.50), and 0% (0/20) and 47% (9/19), respectively, for Staphylococcus aureus (P = 0.0004). There were no statistical differences between groups for new intramammary infections. Overall, ceftiofur extended therapy increased cure when compared to a 2-day regimen for the treatment of naturally occurring mild to moderate clinical mastitis in lactating dairy cows.
    Canadian journal of veterinary research = Revue canadienne de recherche vétérinaire 01/2014; 78(1):31-7. · 1.19 Impact Factor
  • Jean-Philippe Roy, Greg Keefe
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    ABSTRACT: Staphylococcus aureus is the most prevalent pathogen causing intramammary infections (IMI) in dairy cattle worldwide. New treatment regimens have been evaluated to increase cure rates. A systematic review was conducted to answer this question: what is the best antibiotic treatment for S aureus IMI of lactating cows in North America? Direct comparison between studies (n = 6) was difficult since there was no clinical trial comparing all antibiotics and large variations between study protocols and enrolment and outcome definitions were observed. The best therapeutic option currently available in North America is an extended intramammary therapy for 5 to 8 days.
    Veterinary Clinics of North America Food Animal Practice 03/2012; 28(1):39-50, viii. · 2.40 Impact Factor
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    ABSTRACT: To compare results for 3 commercially available microbiological media plates with those for standard bacteriologic testing of bovine milk. Milk samples from postpartum cows and cows with a high somatic cell count (SCC) or clinical mastitis (CM). Sample-ready Staphylococcus culture medium (SRSC) plates were used to detect Staphylococcus aureus in milk samples obtained from postpartum cows and cows with a high SCC or CM. Rapid coliform count (RCC) plates were used to detect coliforms in milk samples obtained from cows with CM. Aerobic count (AC) plates were used to detect streptococci in CM samples. Fresh mastitic milk samples were frozen and then thawed to evaluate the effects of freezing for the SRSC and RCC plates. The effects of dilution (1:10) of samples were determined. Agreement of results between the commercially available plates and standard bacteriologic testing was evaluated. The ability of SRSC plates to detect S aureus in milk samples was highest with diluted samples from postpartum cows and cows with a high SCC or CM. Sensitivity of the RCC plate for detection of coliforms was highest with diluted mastitic milk samples. The AC plates had a poor positive predictive value for detection of streptococci in mastitic milk samples. Freezing increased S aureus detection. Overall, the SRSC and RCC plates were accurate, were easy to use, and yielded results comparable to those of standard bacteriologic testing for the detection of S aureus and coliforms in bovine milk.
    American Journal of Veterinary Research 12/2011; 72(12):1622-30. · 1.35 Impact Factor
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    ABSTRACT: Questionnaires are frequently used instruments to collect data in epidemiological studies. In countries where more than one language is spoken, the development of a questionnaire in more than one language is needed. The objective of this study was to develop and test the repeatability and validity of English and French versions of a personal interview-format questionnaire designed to capture udder health related management practices used on dairy farms. A standardized protocol was used to develop and translate the research instrument. Equivalence of the English and French questionnaires was assessed using a cross-over study design with 24 bilingual dairy producers completing both versions on three different occasions in a randomly assigned sequence. Repeatability of the questionnaire was evaluated using the test-retest method with the same questions being asked on two different occasions to 88 dairy producers participating in the National Cohort of Dairy Farms of the Canadian Bovine Mastitis Research Network. Validity of the questions related to milking procedures and general housing was assessed using on-farm observations as a gold standard. Measures of agreement were calculated using kappa, quadratic-weighted Kappa and concordance correlation coefficients for categorical, ordinal and continuous variables, respectively. Sensitivity and specificity estimates were computed for the validity analysis. The overall equivalence of the English and French versions of the questionnaire was adequate; agreement measures when administered twice in the same language were not significantly higher than when administered in each language. Similarly, questionnaire overall repeatability was good. When accounting for prevalence bias, Kappa and CCC estimates ranged from 0.40 to 0.92 for 27 of the 29 items evaluated in the questionnaire, with 18 items yielding agreement estimates greater than 0.60. Finally, milking procedures and general housing questions validity was excellent with mean sensitivity and specificity of 86% and 92%, respectively. Although the overall evaluation of the instrument was satisfactory, specific doubtful items were identified. This illustrates the need to address questionnaire reliability as even rigorously designed and pre-tested questions can have poor repeatability or validity. Our results indicate that the developed English and French questionnaires can be used simultaneously to accurately measure the udder health related management practices used on Canadian dairy farms. This questionnaire is adaptable for use in other developed dairy industry populations. The questionnaire is freely available online at www.mastitisnetwork.org under the "Publications/others" section.
    Preventive Veterinary Medicine 03/2010; 95(1-2):74-85. · 2.39 Impact Factor
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    ABSTRACT: This study determined the efficacy of a 5-day extended therapy with cephapirin sodium in dairy cows chronically infected with Staphylococcus aureus. Chronically infected cows selected from 14 dairy herds in the St-Hyacinthe region, Québec were randomly allocated to a group of 31 cows treated for 5 consecutive days with 200 mg of cephapirin per quarter BID or a group of 30 untreated control cows. Bacteriological cure was determined by 3 negative bacterial cultures at 10, 24, and 31 days after treatment. The cow cure rates were 25.8% (8/31) in the treated cows and 3.3% (1/30) in the control group (P = 0.013). The quarter cure rates at first sampling post-treatment were 77.6% (38/49) and 18% (9/50) in the treated and the control groups, respectively (P < 0.0001). A 5-day extended therapy with cephapirin is effective in treating cows chronically infected with S. aureus.
    The Canadian veterinary journal. La revue veterinaire canadienne 12/2009; 50(12):1257-62. · 0.77 Impact Factor
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    ABSTRACT: The objective of this study was to evaluate the California Mastitis Test (CMT) and a portable electrical conductivity meter for diagnosing precalving intramammary infection (IMI) in Holstein heifers. A total of 428 dairy heifers from 23 dairy herds were enrolled between 6 and 12 days before the expected calving date from June 2002 to June 2003. Mammary secretions were tested by both diagnostic methods and by bacterial culture for evidence of IMI. California Mastitis Test was considered negative if the score was negative, trace or 1 and was considered positive otherwise. Two cut-off points were evaluated for milk electrical conductivity (>5 and >6.5 mS/cm). From this study, an overall proportion of 69% of heifers had precalving IMI and the overall heifer prevalence of major pathogen IMI was 16.8%. At the quarter level, sensitivity and specificity of CMT (68.9% and 68.4%, respectively) and milk conductivity >5 mS/cm (41.0% and 65.2%, respectively) or >6.5 mS/cm (25.2% and 83.3%, respectively) to identify all IMI were low. However, the heifer level sensitivity and specificity of CMT for major pathogens were 91.0% (81.5-96.6) and 27.5% (22.8-32.6), respectively. Using a cut-off point of 5 mS/cm, the heifer level sensitivity and specificity for major pathogens was 68.7% (56.2-79.4) and 44.1% (38.7-49.6), respectively. A conductivity cut-off value of 6.5 mS/cm decreased the sensitivity and increased the specificity to 53.7% (41.1-66.0) and 59.5% (54.0-64.8), respectively. California Mastitis Test and milk electrical conductivity are not good predictors of major pathogen IMI in heifers during the last 2 weeks before calving. However, the negative predictive values at quarter or heifer level were high and the heifer false negative rate was 6-14% using CMT or conductivity, respectively. Therefore, these measures could be useful for screening out heifers or quarters that are unlikely to have a major pathogen IMI.
    Veterinary Microbiology 09/2008; 134(1-2):136-42. · 3.13 Impact Factor
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    ABSTRACT: A clinical trial was conducted to determine whether prepartum intramammary pirlimycin reduces the proportion of nulliparous heifers with intramammary infection (IMI) during early lactation and improves milk production. Quarter milk samples were collected from 428 heifers, systematically allocated to treatment and control groups, 6 to 12 d before the expected calving date and 2 to 8 d after calving. At the prepartum visit, heifers in the treatment group (n = 219) received an infusion of pirlimycin hydrochloride in all 4 quarters; the control heifers (n = 209) received no infusions. Intramammary infection was detected in 69% of the heifers and 33% of the quarters before calving. After calving, the proportion of treated heifers with IMI was significantly lower than the proportion of control heifers (31% versus 45%). Staphylococcus aureus was isolated from 10% of the heifers and 3% of the quarters before calving. After calving, the proportion of IMIs due to S. aureus was significantly lower in the treated heifers than in the control heifers (5.6% versus 10%). Antibiotic treatment increased the percentage of cures and prevented new IMIs caused by gram-positive bacteria after calving. The incidence of new IMIs caused by gram-negative bacteria and yeast was higher among treated heifers than among control heifers. There was no overall effect of treatment on milk production, but there was a significant interaction effect of treatment and the interval between treatment and calving. An increase of 302 kg of milk was observed when antibiotic treatment was applied more than 1 wk before calving. Treatment did not affect the milk somatic cell count on the 1st 3 test days after calving.
    Canadian journal of veterinary research = Revue canadienne de recherche vétérinaire 11/2007; 71(4):283-91. · 1.19 Impact Factor
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    Emile Bouchard, Jean-Philippe Roy, Denis Du Tremblay

Publication Stats

12 Citations
12.41 Total Impact Points

Institutions

  • 2014
    • South Dakota State University
      Brookings, South Dakota, United States
  • 2008–2012
    • Université du Québec à Montréal
      • Department of Law
      Montréal, Quebec, Canada
  • 2007
    • Université de Montréal
      • Department of Clinical Sciences
      Montréal, Quebec, Canada