Biomedical Engineering Reference
In-Depth Information
Control
Experimental
10
45
9
44
8
43
7
42
6
41
5
40
4
39
3
38
2
37
1
0
36
11.5.03
14.5
17.5
20.5
23.5
26.5
29.5
1.6
4.6
7.6
Days of experiment
Fig. 3
Milk yield of buffaloes of control group (kept under showers) and experimental group (kept in a water tank)
during hot-dry season
stress have been reported, and reflection of such
responses has also been noted in productive (and
reproductive) performance traits. Season of cal-
ving affected significantly milk yield in Indian
(Roy Chaudhury and Deskmuykh
1975
) and
Egyptian buffaloes (Mourad
1978
; Mohamed
2000
; Marai et al.
2009
) . The highest milk yield
was recorded during spring and winter (by cal-
ving during the mild period) and the lowest in
summer (by calving during the hot period), in
Egyptian buffaloes (El-Khaschab et al.
1984
) .
Some studies have shown no significant effect of
season of calving on milk yield in Egyptian buf-
faloes (Alim
1967
; Marai and Habeeb
2010
) . The
insignificant difference in total milk yield due to
season of calving may be an evidence for the
availability of adequate managerial conditions all
year round. Decline in milk yield as a direct result
of high environmental temperatures had been
reported by many authors (Thatcher
1974
;
Johnson
1976
; Marai et al.
2009
) . Between 20°C
(18.2 kg) and 35°C (16.7 kg), the reduction in
milk yield was estimated to be 9%. Particularly,
the rise in temperature averages by 1.6, 3.2 and
8.8°C above normal (21°C); results in the
decrease in daily milk yield average by 4.5, 6.8
and 14%, respectively. On the other side, the
decline in the daily temperature by 7°C below
normal resulted in an increase in daily milk yield
by 6.5% in dairy cattle (Petkov
1971
) . At 30°C,
the high- and low-producing animals showed a
mean reduction of 2.0 and 0.65 kg/day, respec-
tively (Vanjonack and Johnson
1975
) . In a study,
two cooling methods, namely, water showers and
wallowing, were compared. Milk yield of Murrah
Buffaloes was found to be significantly higher in
buffaloes which were allowed to wallow during
hot-dry (Fig.
3
) and during hot-humid (Fig.
4
)
seasons as compared to the buffaloes kept under
showers. The results indicated more beneficial
effects of wallowing than water showers during
heat stress (Anjali and Singh 2008).
13.1.2 Milk Constituents
Milk constituents are greatly affected by hyper-
thermia. In lactating Holstein cows transferred
from an air temperature of 18-30°C, milk fat,
solids-not-fat and milk protein percentages
decreased with 39.7, 18.9 and 16.9%, respec-
tively (McDowell et al.
1976
) . Friesian cows
maintained under 38°C showed lower averages
of total solids, fat, protein, ash and lactose yields
than when the same animals were maintained
under thermoneutral environmental temperatures.
The reduction percentages were 28, 27, 7, 22.7
and 30, respectively (Habeeb et al.
1989
) . Similar
