Browsing by Author "Timsit, Édouard"

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    Advances in Detection and Diagnosis of Bovine Respiratory Disease in Feedlot Cattle
    (2015-09-29) Mang, Afra-Verena Freya; Timsit, Édouard
    Bovine Respiratory Disease (BRD) is one of the most significant health problems in the feedlot industry. The overall objective of this project was to improve BRD detection and diagnosis in commercial feedlots using technology. The first study aimed to: (i) describe changes in body temperature, physical activity, drinking and feeding behaviours associated with BRD; (ii) compare the diagnostic accuracy of these changes for the detection of cattle with BRD: and, (iii) define the diagnostic accuracy of several combinations of physiological and behavioural parameters for the detection of BRD. By equipping 561 feedlot steers with multiple health-monitoring systems, we showed that cattle with BRD displayed a significant increase in rumen temperature, decrease in number of steps taken per day, and decrease in frequency and duration of feedbunk visits compared to healthy pen-mates. These changes were detected up to 7 days prior to clinical illness detected by pen checkers. The comparison of the diagnostic accuracy for BRD detection of these changes revealed that the most accurate were an increased rumen temperature, a decreased number of steps taken per day, and a decreased number of feedbunk visits per day. The combination in series (i.e., “and” rule) of an increased rumen temperature and a decreased number of feedbunk visits per day increased the specificity (Sp) of BRD detection up to 100% without decreasing the sensitivity (Se = 84%). The second study aimed to: (i) determine the level of agreement between a Computer Aided Lung Auscultation (CALA) system and lung auscultation by an experienced veterinarian; and, (ii) evaluate the diagnostic accuracy of CALA to diagnose BRD in feedlot cattle. Of the 561 steers, 35 were identified with visual BRD signs and 35 were selected as healthy controls. Comparison of veterinary auscultation and CALA revealed a substantial agreement (kappa = 0.77). Using latent class analysis, CALA had a relatively high Se (Se = 92.9%; 95% credible interval [CI] = 0.71-0.99) and Sp (89.6%; 95% CI = 0.64-0.99) for diagnosing BRD compared to pen checking. In conclusion, the use of health monitoring and CALA systems can improve BRD detection and diagnosis in feedlot cattle, respectively.
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    Effects of transportation to and commingling at an auction market on the bacterial communities of the respiratory tract of beef cattle
    (2018-07-12) Stroebel, Christina Maria; Timsit, Édouard; Alexander, Trevor W.; De Buck, Jeroen M.; Janzen, Eugene D.
    Commingling at auction markets is considered a major predisposing factor for bacterial bronchopneumonia (BP) in beef cattle. However, the effects of commingling on the respiratory tract bacterial communities is largely unknown. Therefore, the objective of the thesis was to study the effects of transportation to and commingling at an auction market on the nasopharyngeal and tracheal bacterial communities of recently weaned calves using culture-dependent and independent methods. Two groups of 30 Angus-cross heifers were studied from weaning at the ranches of origin to 28 d after arrival at a feedlot. For each group, half the heifers were either transported directly to a feedlot after weaning (RANC) or transported to and commingled at an auction market for 24 hrs before being placed in a feedlot (AUCT). Heifers from both groups received vaccines against major respiratory viruses and a parenteral injection of a long acting macrolide (tildipirosin) at on-arrival processing (d2). Deep nasal swabs (DNS) and trans-tracheal aspirates (TTA) were collected at weaning (d0) and at on-arrival processing at the feedlot (d2). Deep nasal swab sampling only was then repeated 7 days (d9) and 28 days (d30) after arrival. Bacterial culture and 16S rRNA sequencing did not reveal difference in the nasopharyngeal and tracheal bacterial communities between RANC and AUCT at any sampling days. However, both time after arrival and feedlot where calves were placed affected diversity and composition of the nasopharyngeal bacterial communities. In both groups, there was a reduction in bacterial diversity and a large increase in Mycoplasma after feedlot placement, especially seven days after on-arrival processing. Furthermore, we observed the horizontal transmission of a multi-resistant strain of Pasteurella multocida among calves at d9 and d30 in one of the two groups of heifers. Based on these findings, we concluded that transportation to and commingling at an auction market for 24 hrs did not significantly influence the composition and diversity of the nasopharyngeal and tracheal bacterial communities of recently weaned calves.