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

Abstract

The aim of this work was to investigate associations between individual cow Mycobacterium avium ssp. paratuberculosis (MAP) seropositivity, 305-d corrected milk production, and somatic cell count during 5 lactations lifespan in Portuguese dairy herds using multilevel mixed models. We used MAP serum ELISA (Idexx MAP Ac, Idexx Laboratories Inc., Westbrook, ME) results (n = 23,960) from all the 20,221 adult cows present in 329 farms and corresponding 47,586 lactation records from the National Dairy Improvement Association. Cows and farms were classified as positive or negative. Multilevel mixed models were used to investigate the association of cow MAP status with variation in milk production and somatic cell count. Cow MAP status, farm status, and lactation number were considered as independent variables. A quadratic function of lactation number was used to mimic the effect of lactation order on milk production. The models considered 3 levels: measurement occasion (level 1) within cow (level 2) and cow within farm (level 3). Four final models were produced, including all herds and cows, to address the effect of farm status (models 1 and 2) or the effect of cow status (models 3 and 4) on the outcome variables. Our results show that MAP status affects milk production. Losses are detectable from third lactation onward. During the first 5 lactations, positive cows accumulated an average loss of 1,284.8 kg of milk when compared with the negative cows. We also observed that somatic cell counts were higher in positive cows and a positive interaction occurs between cow status and lactation number, suggesting a positive association between MAP infection and increased somatic cell counts. Our results are in line with previous studies, suggesting a possible positive relation between cow milk production and susceptibility to MAP infection.

The Impact of Paratuberculosis on Milk Production, Fertility, and Culling in Large Commercial Hungarian Dairy Herds

“…In the same study, mastitis was more likely in high-risk cows compared to their medium-or low-risk herdmates. In a large Portuguese study, MAP serum ELISA positive cows had elevated SCC levels, and the difference between test positive and negative cows increased in higher parities (27). Other studies found no difference in SCC between test positive and negative cows, using fecal culture (14) or serum ELISA (19).…”

“…Tiwari et al (26) detected an association between MAP and lower milk yield only from the fourth lactation onwards. Martins et al (27) proposed that serum MAP ELISA positive cows had 0.4-0.6 kg/day higher milk yield in the first lactation, suggesting that increased milk production capacity may be related to susceptibility to MAP infection. In the same study, milk losses amounted to 0.2, 0.8, 1.5, and 2.1 kg/day from the second to fifth lactation, respectively, leading to an accumulated loss of nearly 1,300 kg in the first five lactations in ELISA positive cows, on average.…”

Cows with paratuberculosis (Johne's disease) alter their lying behavior around peak lactation

“…Numerous studies have reported a reduction in milk production as a result of JD McAloon et al, 2015). A study by Martins et al (2018) investigating milk production across 5 lactations, found that MAP status affected milk yield, with an average loss of 1,284.8 kg of milk from JD positive (at least 1 positive ELISA test result) compared to JD negative cows (all test results were negative). However, JD positive cows had, on average, higher milk production during their first lactation than JD negative cows and it was from the third lactation onwards that the losses were detectable (Martins et al, 2018), although the authors did not report whether the JD positive cows were showing any clinical signs of the disease.…”

“…Although Ott et al (1999) estimates the cost of JD to the US dairy industry as $200 to $250 million annually, calculating economic losses associated with JD is difficult. Infected animals may have an increased risk of other diseases, such as mastitis (Pritchard et al, 2017;Rossi et al, 2017) and milk production is reduced (Martins et al, 2018), so many infected animals may be culled prior to the clinical stages of JD and therefore misclassified (Caldow et al, 2001).…”

Standardizing output-based surveillance to control non-regulated diseases of cattle in the EU (SOUND-control, COST action-CA17110)

“…are left to be controlled by each Member State (MS) [7]. However, these diseases can also cause economic losses, which are usually hidden at first glance, as they often have subclinical or chronic courses [4]. They also reduce the welfare of affected animals [3].…”