INTRODUCTION
Bovine mastitis is a common disease on dairy farms and leads to enormous
economic losses worldwide (Angelopoulou et al., 2018; Sathiyabarathi et
al., 2016). Escherichia coli is one of the most common
mastitis-causing pathogens and often leads to acute mastitis with a
severe inflammatory response that
damages the
blood-milk barrier. The abuse of antimicrobials in food animals has
attracted public attention as concerns relating to antimicrobial
residues and anti-microbial resistance in bacteria have increased
because of the increased use of antimicrobials (Muziasari et al., 2016;
Lhermie et al., 2016). Therefore, there is an urgent need to find new
potential non-antimicrobials for mastitis prevention.
Lactobacillus is a probiotic that plays an important role in the
immunity and health of animals. Their probiotic properties play an
important role in regulating gut microbiota (Igor et al., 2019),
relieving intestinal diseases (Sanders et al., 2019), and enhancing body
immunity (Garcia-Castillo et al., 2019) in addition to other functions
(Li et al., 2017; da Costa et al., 2019). Lactobacillus is known
to protect hosts during intramammary infection in both humans and cows
by oral or intramammary administration (Fernández et al., 2016; Arroyo
et al., 2010; Jiménez et al., 2008), but the underlying mechanism of
this protective effect remains unclear. Intramammary injection of drugs
is the most common and effective way for treating bovine mastitis in
practice, as intramammary injection of some Lactobacillus strains
can effectively alleviate clinical symptoms of bovine mastitis (Ignacio
et al., 2015; Pellegrino et al., 2017; Kitching et al., 2019). Oral
administration of Lactobacillus casei Zhang (LCZ )
isolated from naturally fermented mare’s milk is effective for
alleviating the clinical symptoms of mastitis in mice (Ma et al., 2018).
However, whether intramammary injection of LCZ has a prophylactic effect
on mastitis, as well as its underlying mechanism, remains unclear. Here,
we studied the prophylactic effect of LCZ by intramammary injection onE. coli -induced mastitis.