• Analysis of Johne’s disease ELISA status and associated performance parameters in Irish dairy cows

      Kennedy, Aideen E.; Byrne, Nicky; Garcia, A. B; O'Mahony, James A.; Sayers, Riona; Irish Dairy Levy Research Trust (2016-03-02)
      Background Infection with Mycobacterium avium subspecies paratuberculosis (MAP) has been associated with reductions in milk production in dairy cows and sub optimal fertility. The aim of this study was to highlight the production losses associated with testing MAP ELISA positive in Irish dairy cows. Secondary objectives included investigation of risk factors associated with testing MAP ELISA positive. A survey of management practices on study farms was also conducted, with examination of associations between management practices and herd MAP status. Blood samples were collected from 4188 breeding animals on 22 farms. Samples were ELISA tested using the ID Screen Paratuberculosis Indirect Screening Test. Production parameters examined included milk yield, milk fat, milk protein, somatic cell count, and calving interval. The association between MAP ELISA status and production data was investigated using multi-level mixed models. Logistic regression was used to identify risk factors for testing JD blood ELISA positive at individual cow level and to identify associations between farm management practices and herd MAP status. Results Data were available for 3528 cows. The apparent prevalence recorded was 7.4 %. Mixed model analysis revealed no statistically significant association between testing MAP ELISA positive and dairy cow production parameters. Risk factors associated with testing positive included larger sized herds being over twice more likely to test positive than smaller herds (OR 2.4 P = <0.001). Friesians were less likely to test positive relative to other breeds. A number of study farmers were engaged in management practices that have previously been identified as high risk for MAP transmission e.g., 73.1 % pooled colostrum and 84.6 % of study farmers used the calving area to house sick animals throughout the year. No significant associations however, were identified between farm management practices and herd MAP status. Conclusion No production losses were identified; however an apparent prevalence of 7.4 % was recorded. With the abolition of EU milk quotas herd size in Ireland is expanding, as herds included in this study were larger than the national average, results may be indicative of future JD levels if no JD control programmes are implemented to minimise transmission.
    • Establishing blood gas ranges in healthy bovine neonates differentiated by age, sex, and breed type

      Dillane, Patrick; Krump, Lea; Kennedy, Aideen E.; Sayers, Riona; Sayers, Gearoid (Elsevier, 2018-02-02)
      Calf mortality and morbidity commonly occurs within the first month of life postpartum. Standard health ranges are invaluable aids in diagnostic veterinary medicine to confirm normal or the degree and nature of abnormal parameters in (sub)clinically ill animals. Extensive research has indicated significant differences between the physiologies of neonate and adult cattle, particularly for blood parameters such as pH, base excess, anion gap, and bicarbonate (HCO3−). The objective of this research was to determine the influence of age, sex, and breed type, in addition to environmental factors, on the normal blood gas profiles of neonatal calves, and thus develop a scientifically validated reference range accounting for any significant factors. The study was conducted on healthy neonatal calves (n = 288), and completed over a 2-yr period. Individual calf blood gas analysis was conducted for parameters of pH, base excess, Na+, K+, Ca2+, Cl−, glucose, total hemoglobin, HCO3−, pCO2, anion gap, strong ion difference, and hematocrit levels. Regression procedures examined the combined effect of year, farm, age, breed type, sex, and hours postfeeding on each variable. Significant effects were observed for age, sex, and breed type on several of the blood gas variables. Furthermore, year, farm, and hours postfeeding appeared to have less of an influence on neonatal bovine blood gas profiles. Consequently, specific ranges based on the neonate's age, sex, and breed type will allow for more detailed and accurate diagnosis of health and ill health in neonatal calves.
    • Investigations and implications of associations between mycobacterial purified protein derivative hypersensitivity and MAP-antibody ELISA in Irish dairy cows

      Kennedy, Aideen E.; Byrne, Nicky; O'Mahony, John; Sayers, Riona (Elsevier, 2017-01-21)
      Intradermal testing, involving administration of purified protein derivative (PPD), to elicit a delayed hypersensitivity (DTH) response, is used as a diagnostic tool for bovine tuberculosis (bTB) and to aid in the identification of exposure to Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of Johne's disease (JD). Further research is required to increase the diagnostic value of skin testing for MAP. The aim of this study was to investigate if animals showing DTH reactions to PPD had an associated increase in MAP ELISA response, thereby identifying potential cases of sub-clinical JD. A 139-cow dairy herd was recruited to the study. During the mandatory annual bTB test, skin thickness measurements (mm) were recorded at the site of avian and bovine PPD administration. Cows were categorised based on recording no DTH, DTH at both PPD administration sites and DTH at one PPD site only. Blood samples were collected pre and post bTB testing, and ELISA tested. Generalised estimating equations were performed to identify associations between DTH responses and MAP ELISA results. Significant associations were identified between PPD DTH responses and MAP ELISA readings. Animals with DTH at both avian and bovine PPD sites were most likely to test ELISA positive in the post-PPD period relative to other categories. Further research is required to identify whether skin thickness increases post-PPD and associated increase in ELISA response, identifies animals previously exposed to MAP, or if results are due to cross reactivity.
    • An observational study using blood gas analysis to assess neonatal calf diarrhea and subsequent recovery with a European Commission-compliant oral electrolyte solution

      Sayers, Riona; Kennedy, Aideen E.; Krump, Lea; Sayers, Gearoid; Kennedy, Emer; Epsilion Ltd.; IV20151256 (American Dairy Science Association, 2016-04-06)
      An observational study was conducted on dairy calves (51 healthy, 31 with neonatal diarrhea) during outbreaks of diarrhea on 4 dairy farms. Clinical assessment scores (CAS) were assigned to each healthy and diarrheic calf [from 0 (healthy) to 4 (marked illness)]. Blood gas analysis [pH, base excess (BE), Na+, K+, Ca2+, Cl−, glucose, total hemoglobin, standard HCO3−, strong ion difference (SID), and anion gap (AG)] was completed for each calf. Repeated measurements were taken in healthy animals, and pre- and postintervention measurements were taken for diarrheic calves. The mean CAS of diarrheic calves was 1.7, with 51, 30, 17, and 2% of calves scoring 1, 2, 3, and 4, respectively. The mean value for blood pH, BE, AG, and SID was 7.26, −4.93 mM, 16.3 mM, and 38.59 mM, respectively. Calves were administered an oral rehydration and buffering solution (ORBS; Vitalife for Calves, Epsilion Ltd., Cork, Ireland) and reassessed. The mean CAS decreased to 0.38 (65% of calves scored 0 and 35% scored 1) at 6 to 18 h posttreatment and to 0.03 (98% of calves scored 0 and 2% scored 1) within 24 to 48 h. Significant increases in mean value for pH, BE, HCO3−, Na+, and SID, and significant decreases in AG, K+, Ca2+, and total hemoglobin were recorded posttreatment. The correlation estimates indicated that pH, HCO3−, and BE were strongly correlated with CAS, with values exceeding 0.60 in all cases. Administration of an ORBS with a high SID and bicarbonate buffer demonstrated rapid recovery from a diarrheic episode in dairy calves.