Biomedical Engineering Reference
In-Depth Information
concentration of CH
4
in dairy buildings has been
reported to be 70 ppm (Jungbluth et al.
2001
) .
The emission of CH
4
per dairy production animal
is 194 g to 390 g/day (Jungbluth et al.
2001
;
Kinsman et al.
1995
; Sneath et al.
1997
) .
Ammonia causes acid deposition and eutrophica-
tion when suspended NH
3
from dairy and other
animal production facilities is deposited on land
and in bodies of water (Anderson et al.
2003
;
Erisman et al.
2003
). The sources of ammonia in
dairy buildings are mainly dairy manure, urine,
bedding materials and animal feed. The transfor-
mation of organic nitrogen to ammonia in dairy
buildings is well documented (Sommer et al.
2006
). The average concentration of NH
3
in dairy
buildings is 10 ppm (Phillips et al.
1998
) , and the
emission of NH
3
per animal is 6.2-31.7 g/day
(Demmers et al.
1998
; Zhang et al.
2005
) .
Hydrogen sulphide is very toxic and has been
reported to contribute to the acidification of the
soil and water in the environment (Sakamotoa
et al.
2006
). Hydrogen sulphide is formed when
manure remains in the dairy building for a period
of over 5 days (CIGR
1994
) . The average con-
centration of hydrogen sulphide in dairy build-
ings is usually around 14 ppb, with a rate of
emission per area between 0.016 and 0.084 g/m
2
/
day (Zhu et al.
2000
) .
naturally and mechanically helps in improving
heat dissipation by means of convection and
evaporation (Bucklin et al.
1988
) . Mechanical
ventilation is very effective in providing air
movement, but it is expensive and should be com-
bined with other methods (Bucklin et al.
1991
) .
Different methods for reducing heat stress in
dairy animals are as follows:
3.1
Provision of Shade
Lowering or preventing heat stress in lactating
animals in summer requires protection from
radiant heat and increase of heat loss from the
body to the environment. Animal shade may
reduce more than 30% of all the heat radiated on
animal and is the single most important contribu-
tion for lowering heat stress (Bond et al.
1967
) .
Animal shade is one of the more easily imple-
mented and economical methods to minimise
heat from solar radiation.
Cows in a shaded versus no shade environ-
ment had lower rectal temperatures (38.9 and
39.4°C) and reduced respiratory rate (54 and 82
breaths/min) and yielded 10% more milk when
shaded (Roman-Ponce et al.
1977
) . Cattle with
no shade had reduced ruminal contractions,
higher rectal temperature and reduced milk yield
compared with shaded cows (Collier et al.
1981
) .
Armstrong (
1994
) reviewed shade and cooling
for cows and discussed the benefits and
deficiencies of various types of shade. The author
suggested differing shade orientations, depend-
ing on whether the application was in a dry or wet
climate. In the humid Southeast, cows should be
allocated 4.2-5.6 m
2
of space beneath the shade
and a north-south orientation to allow for pene-
tration of sunlight beneath the shade for drying
the ground beneath if earthen floors are used.
In hot and humid climate, the cattle and buffalo
prefer to use shade when exposed to high tem-
perature and solar radiation. This is more obvious
at high temperatures and especially in the middle
of the day (Tucker et al.
2008
; Kendall et al.
2006
) . Fisher et al. (
2008
) reported that cows
start using shade when the temperature is above
25°C and the critical temperature when the cows
3
Methods for Alleviation of Heat
Stress
There are several methods available that can help
alleviate animal's heat stress by reducing dry
bulb temperature or the enthalpy in the ambient
air. Increasing air velocity around the animals
may facilitate heat dissipation provided that the
ambient temperature is below body temperature.
Previous research targeted prevention (Silanikove
2000
) of heat stress in lactating cows and the
application of cooling systems for lactating cows,
which minimises decreases in milk production
during summer (Igono et al.
1985
; Her et al.
1988
; Verbeck et al.
1996
; Aggarwal
2004
;
Aggarwal and Singh
2007
) . To reduce heat stress
in hot climate, handling of the animals should be
kept at a minimum. The air movement caused
