As for the underlying causes of the observed responses, the frequent
negligence of environmental conditions of dry cows (verified in this
study, too) is likely to play an important role. Even in the absence of bacterial
infections, poor hygiene and the related infectious pressure could
worsen the effects of well-known inflammatory stimuli associated with
physiological regulations, like massive leukocyte infiltration into the
mammary gland and the release of inflammatory cytokines by adipose
tissues and placenta (Trevisi et al., 2012). These are the pre-calving issues
which can predispose cows to disease occurrence after calving.
Thus, seemingly negligible stressors in the dry period of dairy cows
may cause an unfavorable imprinting of the innate immune system
and a poor homeostatic control of the inflammatory response after calving.
In this scenario, the measurements of lysozyme and, less importantly,
IL-6 in the dry period could enable bovine practitioners to identify
cows and herds at risk, on whom proper anti-inflammatory treatments
could be performed to prevent health disorders after calving (Bertoni
et al., 2004).