The aim of the trial was to assess the relationship between cortisol
concentration (in milk - MC and hair - HC) and dairy cows
health. Cows were sampled in 6 Italian Simmental (IS) and 4
Italian Holstein (IH) commercial farms, were clinical healthy
and between 50 and 270 Days In Milk (DIM). Cows were housed
in free stalls with cubicles and milking parlour, had free access
to ad libitum total mixed ration (TMR) based on corn silage and
their management was similar across farms. Formulated was
offered twice a day, after the morning and the afternoon milking.
The day of official milk recording, 100 ml of milk samples werecollected from each cow at the morning milking and hair was
sampled from the tail switch for cortisol analysis. Blood was sampled
before the morning meal. Plasma samples were analyzed for
Zn, total protein (TP), albumin, ceruloplasmin (CuCp), haptoglobin
(Hp) and paraoxonase (PON): all indices related to the
inflammatory response. For statistical analysis, animals were
classified for parity with ordinal value of 1 for first calving, 2 for
second calving and 3 for cows with more than 2 calvings. A Kmean
cluster procedure was used to cluster the animals on the
base of haematic parameters in 3 classes representing different
animal health levels (C1 = better state; C2 = mild state; C3 =
worse state). The effect of animal health class on cortisol concentrations
was assessed with an univariate model including
also the fixed effects of breed, parity, the interaction of class per
breed and the linear relationship with DIM. Cows in C3 showed
higher (P<0.01) values of MC than cows in C2 and C1. No significant
effects were observed for the breed factor both in MC and
HC, whilst a significant effect of parity was evidenced for HC
concentrations, with higher values in cows with higher parity
number (P=0.000). HC was significantly higher in C1 cows, even
though a significant effect of the interaction breed x class was
also found. These data suggest that milk cortisol is related to the
acute phase response to stress and can be used as a biomarker
of short term activation of Hypotalamus Pituitary Adrenal axis
(HPA) and as an indicator of lactating cows health condition.Instead, HC is probably an indicator of long-term stimulation of
HPA in relation to the environment. These results offer a new
perspective for the definition of animal welfare by means of
endocrine biomarkers.
