Biomedical Engineering Reference
In-Depth Information
however, sebum secretion shows an opposite trend
(Hafez et al.
1955
) . The sebum provides effective
protection to the skin while the buffalo is the mud
or water. The skin of buffaloes is also thicker than
that of cattle and protects the sparsely covered skin
from harmful mechanical and chemical agents
dissolved/suspended in water and mud during
swimming and wallowing (Badreldin and Ghany
1954
; Hafez et al.
1955
) . The wallowing behaviour,
as well as shade seeking, is necessary during the
hot season to protect and dissipate body heat.
Grooming or rubbing skin against hard surface is
important behaviour for body care and for remov-
ing irritants form skin surface. Tail swishing is used
to remove flies and other irritants. Body areas
within reach are licked and scratched, while inac-
cessible areas are rubbed on available surfaces or
groomed by other herd members following solici-
tation. The buffalo exhibits oestrous throughout the
year, but fertility may not be equally distributed as
buffalo is more fertile when daylight hours decrease,
which coincides in tropical areas with greater for-
age availability (Zicarelli
1994
) . The length of the
oestrous cycle of buffalo is less than that of cattle,
that is, average 21 days, and considerable varia-
tions in length of the cycle may be observed in indi-
vidual animals. In buffaloes, the typical signs of
oestrus behaviour (i.e. excitability, standing behav-
iour) are less pronounced than in cows (Seren et al.
1992
; Zicarelli et al.
1992
) , whereas the courtship
behaviour of buffalo bulls is similar to that reported
in cattle. Buffalo bulls/teasers are able to detect
pre-oestrus buffalo and remain close to them,
exhibiting the characteristic 'flehmen' behaviour in
response to pheromones in oestrus urine. In buf-
falo, the fraction of cisternal milk is lower than in
cattle (Thomas
2005
). As a result, lactating buffalo
seems to be sensitive to the minor change in
milking routines, which determines a decrease of
milk flow and milk yield (Thomas et al.
2005
;
Saltalamacchia et al.
2007
) .
and active spermatogenesis can be observed by
15 months of age. However, the ejaculate con-
tains viable spermatozoa only after 24-30
months of age (Perera
1999
) , indicating that
male buffalo matures more slowly than male
cattle (Drost
2007
) and has a longer time lag
between onset of spermatogenesis and the
onset or achievement of puberty. Thereafter,
even if capable of breeding throughout the
year, buffalo bulls are known to show seasonal
rise and fall in reproductive functions, which
have been recorded in most breeds in different
countries (Sengupta et al.
1963
; Esposito et al.
1992
; Zicarelli
1997
). Buffalo bulls may reach
sexual maturity at 2-3 years of age. Semen is
produced all year round, but it is highly affected
by heat stress and low-quality feeds and fod-
ders. The buffalo bull is believed to be most
fertile in spring, when the volume of ejaculate
and sperm concentration is highest. Sperm
vitality is also higher in spring than at other
times of the year. The vitality is lowest in sum-
mer, and heat stress has a negative effect on
libido (Gili et al.
1974
) .
A morphometric study of the testis helps to
evaluate the influence of different factors, such
as hormonal fluctuations of the photo-neuroen-
docrine circuit on reproductive efficiency due
to seasonal variation (Yasuo et al.
2006
) . The
morphology and physiological functions of the
male gonad are under influence of the pineal
and pituitary secretions during the year (Goeritz
et al.
2003
; Pant et al.
2003
) . Size and weight
of testis are excellent indicators of sperm-pro-
ducing capacity and spermatogenic functions
(Fields et al.
1979
; Finch
1986
; Yarney et al.
1990
). The highest scrotal circumference has
been observed in the month of October
(Mikelsen et al.
1981
) . The reduction in tes-
ticular measurements (testes weight and length)
by exposure to heat stress is due to degenera-
tion in the germinal epithelium and to a partial
atrophy in the seminiferous tubules (Chou et al.
1974
). This is reflected in the adverse effects
on the average number of testicular cells, espe-
cially the secondary spermatocytes and sper-
matids of types B, C and D, the ratio of Sertoli
cells to other cells and the diameter of the
9.1
Males
In well-nourished, good body condition buf-
falo bull, testicular spermatogenic cell divi-
sions are likely to start by about 1 year of age,
