Ž .
6–7 years old Novoa, 1970; Arthur et al., 1985 . Inadequate body weight caused by Ž
lack of sufficient food appears to be the cause of delayed puberty in the camel Chatty, .
1972 . Nutrition seems to play a vital role in the various physiological events for the attainment of sexual maturity and in the reproductive process. The faster an animal
Ž .
grows, the earlier it will reach sexual maturity Maynard et al., 1979 . In cattle, puberty Ž
. occurs at a particular liveweight bodyweight or body size rather than a fixed age.
Meanwhile, in sheep, it is complicated by their seasonal breeding pattern in Europe Ž
. McDonald et al., 1988 . Undernutriton delays puberty in both male and female virgin
camels and, if severe, can cause retrogressive changes in the sexual organs after their Ž
. full development Maynard et al., 1979 .
3. Breeding season
Camels are considered seasonal breeders. However, information about the breeding season in the dromedary is rather conflicting. Thus, the breeding season has been
Ž .
reported from March to August in Sudan Musa and Abusineina, 1978a , December to Ž
. Ž
March in Pakistan Yasin and Wahid, 1957 , November to March in India Matharu, .
Ž .
Ž 1966 , April to May in Somalia Mares, 1954 , December to May in Egypt Shalash,
. Ž
. 1965 , December to March in Tunisia Minoia et al., 1992 , and October to April in
Ž .
Saudi Arabia Abdel-Rahim and El-Nazier, 1990; Al-Eknah et al., 1997a,b . Decreasing Ž
daylength appears to be the stimulus to seasonality Merkt et al., 1990; Musa et al., .
Ž 1993 . In camels near the equator, factors such as rainfall Bono et al., 1989; Arthur,
. Ž
. 1992 , nutrition, and management Wilson, 1984 may override the effects of photope-
Ž .
riod and allow breeding to occur throughout the year Arthur et al., 1985 . Therefore, Ž
with a continuous supply of sufficient food, camels can be truly polyoestrus Arthur et .
al., 1982 . The main trigger for Arabian camel sexual receptivity is rainfall and the Ž
. subsequent availability of improved nutrition Cristofori et al., 1986 . Mature male
dromedary camels show also a seasonal sexual activity. The rutting season occurs during Ž
. spring in Egypt Abdel-Raouf and El-Naggar, 1964 , from November to February in
Ž .
India Khan, 1971 and from mid-January to the end of May in the Turkiman dromedary Ž
. Abdunazarov, 1970 . Higher testosterone levels and active poll glands have been found
Ž during the rutting season Yagil and Etzion, 1980; Tingari et al., 1984; Agarwal and
. Khanna, 1990 . Spermatogenesis continues throughout the year in male camels, but at a
Ž .
higher rate during the cooler months of the breeding season Abdel-Raouf et al., 1975 . Hyperprolactinaemia has been proposed to cause reduced libido and fertility during the
nonbreeding seasons of the male camel, due to the suppressive effect of the high Ž
. prolactin levels on secretion of FSH and LH Azouz et al., 1992 . GnRH treatment has
been used to stimulate sexual activity in normal males outside the breeding season Ž
. Moslah et al., 1992 .
4. Ovarian dynamics
Camels are seasonally polyoestrus and induced ovulators. Follicular growth occurs in Ž
. regular waves during the breeding season Musa et al., 1993 . The cycle, compared with
Ž that of ungulates and primates, is incomplete, consisting of prooestrus growing folli-
. Ž
. Ž
cles , oestrus mature follicles , and dioestrus
follicular atresia if mating has not .
occurred . During the breeding season, waves of follicular growth, maturation, and Ž
. atresia occur constantly in both ovaries Musa, 1969; El-Wishy and Hemeida, 1984 .
Ž .
Al-Eknah et al. 1993 recorded four distinct phases of uterine activity during the oestrous cycle of the Saudi camel: the high phase, declining phase, low phase and
increasing phase. These phases correspond to follicular, atretic follicular, nonfollicular Ž
. and growing follicular stages, respectively Nawito et al., 1967 . The mean duration of
Ž .
the oestrous cycle has been reported to be 23.4 days in India Joshi et al., 1978 , 24.2 Ž
. Ž
days in Egypt Nawito et al., 1967 , and 28 days in Sudan Musa and Abusineina, .
1978b . The latter investigators recorded an oestrous duration of 4–6 days and 6 days Ž
. Ž
2–14 days of follicular maturation. The follicles maintain their size for 13 days 5–19 .
Ž .
days and then regress in 8 days 7–10 days . In Saudi Arabia, oestrous-cycle durations Ž
. of 16–30 days and 11–27 days have been observed by Bakkar and Basmaeil 1988 and
Ž .
Al-Eknah et al. 1993 , respectively. Realtime ultrasonography has been used to monitor the ovarian follicular wave
Ž .
pattern in the camel Skidmore et al., 1996 ; the follicular cycle has been divided into a Ž
. Ž
. growth phase 10.5 q 0.5 days , a mature phase 7.6 q 0.8 days and a regression phase
Ž .
11.9 q 0.8 days . Serum oestradiol concentration reaches peak values when the domi- nant follicle measures 1.7 q 0.1 cm in diameter. The optimal time to mate or attempt to
induce ovulation is when the growing follicle measures 0.9–1.9 cm in diameter Ž
. Skidmore et al., 1996 . Ovulation in the camel is induced and occurs after mating
ŽNawito et al., 1967; Novoa, 1970; Musa and Abusineina, 1978b; El-Wishy and .
Hemeida, 1984; Cristofori et al., 1986 . The evidence of induced ovulation is the Ž
. absence of a corpus luteum formation Nawito et al., 1967; Elias et al., 1984 and low
Ž .
serum progesterone concentrations in unmated females Skidmore et al., 1996 . The latter investigators have reported that no spontaneous ovulation occurs in camels, even
in females that are close to, but not mated by, male camels. Ovulation can occur within 48 h following mating or intramuscular injection of luteinizing hormone; the left and
right ovaries function alternatively. In the absence of a male, oestrous may last 2 weeks, whereas if copulation occurs on the fist day of oestrous, receptivity may disappear after
Ž .
3 days Musa and Abusineina, 1978b .
5. Synchronisation of ovarian activity and artificial insemination
