The effect of repeated episodes of bacteria-specific clinical mastitis on mortality and culling in Holstein dairy cows

Abstract

The objective of this study was to estimate the effect of a first and repeated cases of bacteria-specific clinical mastitis (CM) on the risk of mortality and culling in Holstein dairy cows. The pathogens studied were Streptococcus spp., Staphylococcus aureus, Staphylococcus spp., Escherichia coli, Klebsiella spp., Trueperella pyogenes, others, and no growth on aerobic culture. A total of 50,166 lactations were analyzed from 5 large, high-milk-producing dairy herds in New York State from 2003/2004 to 2011. Generalized linear mixed models with a Poisson error distribution were used to study the effects of parity, month of lactation, CM, calving diseases, pregnancy status, current season, and economic values on the risk of mortality and culling. Among first-lactation cows, the presence of a first CM case generally exposed cows to a greater risk of mortality in the current month (compared with the absence of a first case). This was especially acute with a first case of Klebsiella spp., where cows were 4.5 times more at risk [95% confidence interval (CI): 2.7-7.6] of mortality, and with a first case of E. coli were 3.3 times more at risk (95% CI: 2.5-4.5). In first-parity cows, the risk of culling generally increased with a case of bacteria-specific CM. This was observed among cows with a first case of T. pyogenes [relative risk=10.4 (95% CI: 8.4-12.8)], a first case of Klebsiella spp. [relative risk=6.7 (95% CI: 5.5-8.1)], a first case of Staph. aureus [relative risk=4.8 (95% CI: 2.7-8.4)], a first case of E. coli [relative risk=3.1 (95% CI: 2.7-3.6)], and a third case of Klebsiella spp. [relative risk=5.0 (95% CI: 3.1-8.0)]. In general, the presence of a first or second/third case resulted in cows in parity ≥2 with a greater risk of mortality. This was greatest for cows with a first case of Klebsiella spp. [relative risk=3.7 (95% CI: 3.3-4.3)], followed by a second/third case of Klebsiella spp. [relative risk=3.2 (95% CI: 2.5-4.0)], a first case of E. coli [relative risk=3.0 (95% CI: 2.7-3.3)], and a first case of other CM [relative risk=1.8 (95% CI: 1.6-2.0)]. Among cows of parity ≥2, the risk of culling was greater for cows as they progressed through lactations [i.e., cows in parity 4+ were 2.1 (95% CI: 2.0-2.2) times more likely to be culled compared with cows in lactation 2 (the baseline)]. The risk of culling dependent on the cow's characteristics can be easily calculated from the parameter estimates in the provided tables.

Progression to multi-scale models and the application to food system intervention strategies

“…The economic model developed for clinical mastitis (Bar et al, 2008b;Cha et al, 2011Cha et al, , 2013 allows us to use it as a tool which can be expanded to other production-limiting diseases as we have done (Gröhn et al, 2003;Cha et al, 2010). With this tool we can assess the value of diagnostic information (above mentioned generic vs. Gram± vs. bacteria specific mastitis) and determine the value of intervention strategies (e.g., Bar et al, 2008c).…”

“…These herds are relatively large well-managed dairy farms using freestall housing, total mixed ration feeding and parlor milking. Using these data we have generated parameter estimates for our dynamic program model at 3 levels (generic (i.e., pathogen-unidentified), Gram±, and bacteria specific): risk of mastitis (Bar, 2007;Schukken et al, 2010), mortality (Gröhn et al, 2005;Bar et al, 2008a;Hertl et al, 2011;Cha et al, 2013), conception (Wilson et al, 2008;Hertl et al, 2010Hertl et al, , 2014a, milk loss Bar et al, 2007;Schukken et al, 2009;Hertl et al, 2014b), and associated costs (treatment, culture, and discarded milk).…”

Factors affecting the incidence and outcome of <i>Trueperella pyogenes</i> mastitis in cows

“…Summer mastitis occurs in heifers and dry cows and is characterized by malodorous, purulent milk and detection of anaerobic bacteria [3, 7, 8, 17, 19, 21]. In recent large-scale surveys, T. pyogenes has been identified as one of the main pathogenic bacteria causing mastitis in lactating cows [2, 4, 5]. Reported symptoms include high somatic cell count [16], notable reduction in milk yield [5], high rate of mammary gland dysfunction [18] and tendency toward culling [2, 6].…”

Dairy production: maintaining the focus on mastitis prevention

“…A death on-farm leads to maximum loss (and further costs for carcase disposal) but when slaughtered for meat production significant revenue can be obtained (dairy cull cows averaged over £1.15/kg in the UK in 2013 [DairyCo 2013b]). Reports of premature culling due to mastitis are likely to include a proportion that die on-farm and will therefore probably indicate increased depreciation costs for affected herds (Cha and others 2013). …”

“…The most common pathogens isolated are from the coagulase-negative staphylococci (CNS) group, although major pathogens, including Staphylococcus aureus , are also commonly isolated (De Vliegher and others 2012). While infection with major pathogens can be expected to result in significant reductions in future milk yield (Nickerson 2009, Cha and others 2013), CNS infection has recently been shown to be correlated with increased production (Piepers and others 2010). This is not yet fully understood but recent evidence suggests it is not as simple as providing the animal with protection from infection by major pathogens or that there is increased susceptibility (to CNS infection) in animals with higher genetic potential for milk production (Piepers and others 2013).…”