Phenotypic effects of subclinical paratuberculosis (Johne’s disease) in dairy cattle

Abstract

The effect of subclinical paratuberculosis (or Johne's disease) risk status on performance, health, and fertility was studied in 58,096 UK Holstein-Friesian cows with 156,837 lactations across lactations 1 to 3. Low-, medium-, and high-risk group categories were allocated to cows determined by a minimum of 4 ELISA milk tests taken at any time during their lactating life. Lactation curves of daily milk, protein, and fat yields and protein and fat percentage, together with log-transformed somatic cell count, were estimated using a random regression model to quantify differences between risk groups. The effect of subclinical paratuberculosis risk groups on fertility, lactation-average somatic cell count, and mastitis were analyzed using linear regression fitting risk group as a fixed effect. Milk yield losses associated with high-risk cows compared with low-risk cows in lactations 1, 2, and 3 for mean daily yield were 0.34, 1.05, and 1.61kg; likewise, accumulated 305-d yields were 103, 316, and 485kg, respectively. The total loss was 904kg over the first 3 lactations. Protein and fat yield losses associated with high-risk cows were significant, but primarily a feature of decreasing milk yield. Similar trends were observed for both test-day and lactation-average somatic cell count measures with higher somatic cell counts from medium- and high-risk cows compared with low-risk cows, and differences were in almost all cases significant. Likewise, mastitis incidence was significantly higher in high-risk cows compared with low-risk cows in lactations 2 and 3. Whereas the few significant differences between risk groups among fertility traits were inconsistent with no clear trend. These results are expected to be conservative, as some animals that were considered negative may become positive after the timeframe of this study, particularly if the animal was tested when relatively young. However, the magnitude of milk yield losses together with higher somatic cell counts and an increase in mastitis incidence should motivate farmers to implement the appropriate control measures to reduce the spread of the disease.

The Effect of Mycobacterium avium subsp. Paratuberculosis Infection on the Productivity of Cows in Two Dairy Herds with a Low Seroprevalence of Paratuberculosis

“…In our study, we observed a statistically significant decrease in the milk yield of seropositive animals in herd B (higher seroprevalence). A similar relationship was observed by Pritchard et al [6] in the UK and by Bates et al [15] in New Zealand. Conversely, in herd A (lower seroprevalence), we observed a significantly higher milk yield in seropositive than in seronegative cows.…”

“…The prevention and control of the epizootic status of the newly introduced animals is the only effective method of preventing MAP infections. The long disease incubation time, the absence of pathognomonic symptoms, and diagnostic methods characterised by variable sensitivity/specificity hinder correct JD diagnosis [4,6]. The disease appears in cattle herds worldwide.…”

Association of paratuberculosis sero-status with milk production and somatic cell counts across 5 lactations, using multilevel mixed models, in dairy cows

“…No fully effective tools or strategies exist to prevent new infections or disease progression. Effects of MAP on animal welfare are relevant and the effect on dairy operations has been linked to impaired udder health, milk production (McAloon et al, 2016;Pritchard et al, 2016;Smith et al, 2016), and reproductive performance (Donat et al, 2014;Mato et al, 2015;Pritchard et al, 2017).…”

Knowledge gaps that hamper prevention and control ofMycobacterium aviumsubspeciesparatuberculosisinfection

“…JD control programmes have been implemented in most developed countries, with objectives based on the national economic situation of the cattle, sheep and goat industry and the herd‐level prevalence of MAP infection (reviewed by Kennedy, ; Geraghty, Graham, Mullowney, & More, ). In general, objectives include the following: (i) prove and protect freedom of disease at the country, regional or farm‐level, for example, in Norway (Whist et al., ), Sweden (Frössling et al., ) and northern and western Australia (Kennedy, ); (ii) protect export of milk or genetics, for example, Canada (McKenna, Vanleeuwen, et al., ); (iii) decrease prevalence of MAP infection and limit farm‐level economic losses, for example, Denmark (Nielsen, Jepsen, & Aagaard, ), the UK (Pritchard, Coffey, Bond, Hutchings, & Wall, ), Ireland (McAloon et al., ) and the USA (Wells, Hartmann, & Anderson, ); (iv) eliminate or reduce MAP load in bulk milk, for example, the Netherlands (Weber & van Schaik, ); and (v) eliminate MAP infection, for example, Norway in goats (Nagel‐Alne et al., ).…”