Thirty mid-lactation Friesian cows, 178 day post-partum were randomly
assigned to three equal groups (N= 10 per group). All animals were
blocked for age (6 year old), stage of milk yield and average body
weight. The experiment was carried out during the months of July and
August, 2007 in which the first group of the experimented- animal was
left in loose box without shade and expressed to heat stress while the
second group was left in shaded box (white galvanized metal roof, 4
meters above the ground and covered about 70% of the yard area).
However the later group left in a box supported with shade plus fans
(fans were installed regularly at height of 2.4 meters above the ground
and spaced 1.5 meters along the manger shed). Our study revealed that
provision of shade had no significant effect on temperature-humidity
index (THI) while providing shade and fans had significantly lowered
THI. At the same time the shade and fans had a significant effect on
daily milk production but shade alone had no significant effect on milk
yield. Milk yield was slightly increased with shade (insignificant) and
tended to be greater for shaded and cooled cows (significant) as compare
to non shaded animals. Also, this study indicated that, forage intake was
significantly lower for the experimented cows that housed without shade
than for those housed with shade and fans. Providing dairy cows with
access to shade or to shade and fans during summer season was effective
in reducing mean rectal temperature and respiratory rate. Moreover, this
study revealed some statistically significant differences in certain
behavioral patterns of cows that housed without shade under the
prevalent hot weather and those housed either under shade only or under
shade and fans (p < 0.01). Moreover, leucocytic series of the
experimented cows was not significantly affected by any of the studied
housing conditions however cortisol and glucose levels were
significantly higher (p < 0.01) in the serum of the experimented cows that
housed without shade than in those housed either with shade only or
with shade and fans.