Effect of hot season on blood parameters, fecal fermentative parameters, and occurrence of Clostridium tyrobutyricum spores in feces of lactating dairy cows

High temperature influences rumen and gut health,
passage rate, and diet digestibility, with effects on fermentative
processes. The main aim of the study was
to investigate the effect of hot season on hindgut fermentation,
the occurrence of Clostridium tyrobutyricum
spores in bovine feces, and on their relationship with
metabolic conditions in dairy cows producing milk used
for Grana Padano cheese. The study was carried out on
7 dairy farms located in the Po Valley (Italy), involving
1,950 Italian Friesian dairy cows. The study was carried
out from November 2013 till the end of July 2014.
Temperature and relative humidity were recorded daily
by weather stations. Constant management conditions
were maintained during the experimental period. Feed
and diet characteristics, metabolic conditions, and fecal
characteristics were recorded in winter (from late
November 2013 to the end of January 2014), spring
(from April to May 2014), and summer (July 2014)
season. In each season, blood samples were collected
from 14 multiparous lactating dairy cows per herd to
measure biochemical indices related to energy, protein,
and mineral metabolism, as well as markers of inflammation
and some enzyme activities. Fecal samples were
also collected and measurements of moisture, pH and
volatile fatty acids (VFA) were performed. The DNA
extracted and purified from fecal samples was used to
detect Clostridium tyrobutyricum spores in a quantitative
real-time PCR assay. The daily mean temperaturehumidity
index was 40.7 ± 4.6 (range 25 to 55), 61.2
± 3.7 (range 39 to 77), and 70.8 ± 3.2 (range 54 to 83)
in winter, spring, and summer, respectively. Total VFA
concentration in feces progressively decreased from
winter to summer. The seasonal changes of acetate
and propionate followed the same trend of total VFA;
conversely, butyrate did not show any difference between
seasons, and its molar proportion was greater in
summer compared with winter. A greater occurrence of
Cl. tyrobutyricum spores in summer compared with the
other seasons was observed. The plasma concentrations
of glucose, urea, albumin, Ca, Mg, Cl, Zn, and alkaline
phosphatase activity were lower in summer compared
with winter, whereas the opposite occurred for bilirubin
and Na. Our results show that summer season, through
direct and indirect effect of heat stress, affected fecal
fermentative parameters and hindgut buffering capacity,
and was responsible for the increasing occurrence of
Cl. tyrobutyricum spores in feces.