Evaluation of the udder health status in subclinical mastitis affected dairy cows through bacteriological culture, somatic cell count and thermographic imaging
Polish Journal of Veterinary Sciences Vol. 18, No. 4 (2015), 799–805
DOI 10.1515/pjvs-2015-0104
Original article
Evaluation of the udder health status
in subclinical mastitis affected dairy cows
through bacteriological culture, somatic cell
count and thermographic imaging
A. Bortolami1,2, E. Fiore1, M. Gianesella1, M. Corrò2, S. Catania2, M. Morgante1
1
Department of Animal Medicine, Production and Health, University of Padua.
Viale dell’Universitá 16, Legnaro, Padova, Italy
2
Istituto Zooprofilattico Sperimentale delle Venezie. Diagnostic in Animal Health.
Viale dell’Universitá 10, Legnaro, Padova, Italy
Abstract
Subclinical mastitis in dairy cows is a big economic loss for farmers. The monitoring of subclinical
mastitis is usually performed through Somatic Cell Count (SCC) in farm but there is the need of new
diagnostic systems able to quickly identify cows affected by subclinical infections of the udder. The
aim of this study was to evaluate the potential application of thermographic imaging compared to
SCC and bacteriological culture for infection detection in cow affected by subclinical mastitis and
possibly to discriminate between different pathogens. In this study we evaluated the udder health
status of 98 Holstein Friesian dairy cows with high SCC in 4 farms. From each cow a sample of milk
was collected from all the functional quarters and submitted to bacteriological culture, SCC and
Mycoplasma spp. culture. A thermographic image was taken from each functional udder quarter and
nipple. Pearson’s correlations and Analysis of Variance were performed in order to evaluate the
different diagnostic techniques. The most frequent pathogen isolated was Staphylococcus aureus
followed by Coagulase Negative Staphylococci (CNS), Streptococcus uberis, Streptococcus agalactiae
and others. The Somatic Cell Score (SCS) was able to discriminate (p<0.05) cows positive for a pathogen from cows negative at the bacteriological culture except for cows with infection caused by CNS.
Infrared thermography was correlated to SCS (p<0.05) but was not able to discriminate between
positive and negative cows. Thermographic imaging seems to be promising in evaluating the inflammation status of cows affected by subclinical mastitis but seems to have a poor diagnostic value.
Key words: dairy cows, subclinical mastitis, bacteriological culture, somatic cell score, thermography
Correspondence to: A. Bortolami, e-mail:
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A. Bortolami et al.
Introduction
Bovine mastitis is a result of inflammation of the
mammary gland. Depending on the severity of the
inflammation, mastitis can be classified as sub-clinical,
clinical or chronic. The degree of inflammation is dependent on the nature of the causative agent and on
age, breed, immunological health and lactation state
of the animal (Viguier et al. 2009). Many bacteria,
mycoplasmas, yeasts and algae may cause mastitis in
dairy cows. Watts et al. (1988) identified 137 different
microorganisms as etiological agent of mastitis but
only a few of them are routinely isolated.
Mastitis pathogens have been divided in „contagious” and „environmental”. In the „contagious”
group Staphylococcus aureus, Streptococcus agalactiae
and Mycoplasma bovis are considered the major
pathogens. The major environmental pathogens are
Enterobacteriacee (as Escherichia coli), Streptococcus
dysgalactiae and Streptococcus uberis (Blowey and Edmondson 2010). Coagulase Negative Staphylococci
(CNS) are common environmental microorganisms
but, in the last years, have been isolated more and
more frequently from clinical milk samples and can be
considered as emerging pathogens (Pyorala and
Taponen 2009). Radostis et al. (2007) defines subclinical mastitis as an infection without visible changes
in milk or the udder.
Subclinical mastitis is a big economic loss for
farmers. Ott and Novak (2001) estimated a milk loss
of 4.6% for Medium Bulk Tank Milk SCC
(BTMSCC) (200,000 to 399,999 cells/ml) and 11.9%
for High BTMSCC (> 400,000 cells/ml) compared to
Low BTMSCC (< 200,000). Moreover, other money
loss comes from the lower financial incentives for high
quality milk and increased costs for veterinary and
drug expenses. For bovine raw milk, European Union
has set a limit for the sale of 400,000 BTMSCC (Reg.
CE 853/2004). In many cases, the productivity of the
cow will be permanently compromised (Halasa et al.
2007). Because of its financial impact, much attention
has to be dedicated to the diagnosis and detection of
subclinical mastitis problems in modern dairy farms.
Diagnostic methods have been developed to detect of
mammary gland inflammation and diagnosis of the
infection and its causative pathogens. The gold standard is considered the bacteriology but has several
limitations in identifying uninfected cows (Madouasse
et al. 2012). Here are some possible reasons for that:
no bacteria will grow when the bacteria have been
terminated, the media used does not allow to grow the
bacteria causing the infection, there are no bacteria in
the milk sample collected although an Intra-Mammary Infection (IMI) is present as in the case of intermittent shedding (Sears et al. 1990). Because of these
limitations, the costs and the time required for the
response bacteriological sampling is not feasible as
a routine test (Pyörälä and Taponen, 2009). Tests for
indicators of inflammation are therefore necessary as
screening tests to identify the quarters with IMI
(Ruegg and Reinemann, 2002).
Currently, assays often used include measurement
of SCCs, enzymatic analysis and CMT (Viguier et al.
2009). The presence of a pathogen in the mammary
gland causes an increase in the number of immune
cells, mostly neutrophils, to fight the infection. Therefore, an elevated cell concentration can be used as an
indicator of infection (Madouasse et al. 2012).
Thermographic imaging has been recently applied
in veterinary medicine and in animal production as
a potential diagnostic and preventive tool, thus avoiding undue stress reactions.
In the bovine species, infrared thermography
(IRT) has been used as a diagnostic tool for disease
detection (Stelletta et al. 2012). In dairy cows, IRT
has the potential to be a rapid, non-invasive, real-time
method of detecting mastitis since a symptom of mastitis is the increase in local temperature from inflammatory reactions (Scott et al. 2000, Colak et al. 2008).
Hovinen et al. (2008) infused E. coli lipopolysaccharides (LPS) into the left forequarter of the udder and
showed that the treated quarter exhibited an increase
in surface temperature of 1 – 1.5oC compared to the
untreated right quarter. In a similar experiment,
Pezeshki et al. (2011) compared several potential biomarkers of mastitis via induction with E. coli. Peak
udder surface temperature was noted to increase
2 – 3oC but this increase was slower than the one in
rectal temperature. In a study that included 62 Brown
Swiss dairy cows, IRT ability to detect mastitis was
compared to Somatic Cell Count (SCC) and Ca (...truncated)
