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
Application of artificial insemination in the camel requires a reliable method for synchronisation of oestrus in groups of females. Such a method is also essential in
embryo transfer programmes. Extensive research and development have been achieved in oestrous synchronisation and controlled breeding in cattle; however, little research has
been found in the camel side. Camels as induced ovulators offer great prospects of natural synchronisation of oestrous, since with copulation follicular regression occurs in
Ž .
3 days Yagil and Etzion, 1984; Yagil and van Creveld, 1990; Musa et al., 1993 . The synchronisation of oestrous has solved problems of oestrous detection and has made
Ž .
artificial insemination more convenient Helmy, 1991; Minoia et al., 1992 . The
Ž .
progesterone-releasing intravaginal device PRID has been used to synchronise ovula- Ž
tion in a significant proportion of female camels Cooper et al., 1990, 1992; Skidmore et .
al., 1992 . The devices are withdrawn after 7 days, to mimic the camel’s luteal phase. Ž
. According to Cooper et al. 1992 , the PRID alone was not a satisfactory method for
controlling ovarian function. Progestin injections have been successfully used to syn- Ž
. chronise oestrous in the dromedary Mckinnon and Tinson, 1992 . Equine chorionic
Ž .
gonadotrophin eCG , in doses ranging from 1000 to 8000 IU, has been used to induce oestrous in both the nonbreeding and breeding seasons. However, the number of
Ž pregnancies achieved has been found to be very low Yagil and Etzion, 1984; Elias et
. al., 1985; Rai et al., 1990 .
Efficient methods to induce and synchronise ovulation in the camel are now required as the interest grows in the potential application of artificial insemination and embryo
Ž .
transfer Cooper et al., 1992 . In the camel, ovulation could be induced by mating with Ž
. an intact or vasectomised male Marie and Anouassi, 1987 . However, manual stimula-
tion of the cervix, as well as the intrauterine injection of whole semen, seminal plasma, water, or prostaglandin, have not been found to stimulate the release of sufficient LH
Ž from the pituitary to cause ovulation Musa and Abusineina, 1978a; Sheldrick et al.,
. 1992 . Mechanical stimulation of the cervix, which triggers ovulation in species such as
Ž the cat and rabbit has not been useful to induce ovulation in the camel Musa and
. Abusineina, 1978b; Musa et al., 1990; Elias et al., 1984 . Therefore, the ovulatory
response in the camel could be the result of a combination of stimuli, including a chemical factor in the seminal plasma, neurohormonal responses to the mechanical
Ž stimuli of coitus and the male effect Marie and Anouassi, 1987; Anouassi et al., 1992;
. Moslah et al., 1992; Skidmore et al., 1996 .
Ovulation in the camel has been induced by a single treatment with GnRH or hCG ŽMarie and Anouassi, 1987; Anouassi et al., 1992; Mckinnon and Tinson, 1992;
. Sheldrick et al., 1992; Skidmore et al., 1996 . The latter investigators have postulated
that ovulation rates reached 85 in natural mating, 81 with 20 mg GnRH analogue, and 67 with 3000 IU hCG when the dominant follicle measured 0.9–1.9 cm in
diameter. A marked reduction in the effectiveness of natural mating and these hormones to induce ovulation has been observed when the diameter of the dominant follicle
Ž .
exceeded 2.0 cm in diameter Skidmore et al., 1996 . Ž
. Artificial insemination AI is a tool for improving genetic traits, such as milk, meat,
and wool production and racing ability. This is performed by using superior male genomes on population basis. Camel semen deposited into the female’s uterus may
Ž .
induce ovulation without the need for coitus Chen et al., 1985; Musa et al., 1990 . This makes AI an attractive tool for genetic improvement, using selected males and insemi-
Ž nating groups of females in which follicular development has been synchronised Musa
. et al., 1993 . Semen can be collected from males either by using an artificial vagina
Ž .
AV during mating or by electro-ejaculation. A bull AV and a standard bovine
Ž ejaculator have been used to collect semen from the male camels Abdel-Raouf and
El-Naggar, 1976; Tingari et al., 1986; Dafalla et al., 1988; Sieme et al., 1990; Anouassi .
et al., 1992; Musa et al., 1993 . Camel semen is thick and gelatinous immediately after Ž
collection. Liquefaction time varies from 4.5–9.6 min Abdel-Raouf and El-Naggar, .
1976 . Semen used in an AI programme should have a sperm concentration greater than
325 = 10
6
rml and percentages of motile sperm, dead sperm, and abnormal sperm Ž
higher than 50.5, lower than 18.0, and lower than 27.7, respectively Tingari et al., .
1986; Ismail, 1988; Merkt et al., 1990; Musa et al., 1992, 1993 . Billah and Skidmore Ž
. 1992 reported a considerable variation in the semen characteristics of the dromedary
camel. Semen quality has been found to be correlated with the general health and the Ž
. nutritional status of the males Musa et al., 1993 .
For liquid preservation of camel semen, various extenders that showed good results Ž
. Ž
. include laiciphose Cassou, 1959 , Androlepe Waberski et al., 1989 , sodium citrate
Ž .
Ž .
egg yolk extender Kupper, 1954 , and the Dimitropolouse extender Rasbech, 1984 . Extenders containing egg yolk and lactose appeared more suitable to preserving camel
Ž .
semen in the liquid state Sieme et al., 1990; Anouassi et al., 1992; Musa et al., 1992 . Diluted fresh semen has been preserved in plastic tubes and stored at 48C for a
Ž .
maximum of 36 h Musa et al., 1993 . Deep freezing of camel semen has been
Ž .
performed. Sieme et al. 1990 compared different freezing methods with recommended Ž
. modifications of the technique developed by Westendorf et al. 1975 . A major difficulty
Ž .
with camel AI is ensuring that the inseminated females ovulate Chaudhary, 1995 . Ž
. According to Anouassi et al. 1992 ovulation rates and pregnancy were significantly
higher in inseminated camels that had been mated by a vasectomised male. However, this is not a practical method because of the risk of the transmission of venereal and
other diseases. Therefore, following AI, ovulation has been induced with either 3000 IU
Ž .
hCG or 20 mg of the GnRH analogue, Buserelin Mckinnon and Tinson, 1992 .
6. Superovulation and embryo transfer
