The level of fertility in domestic animals results from a number of interacting factors, some of which have a genetic basis while others are environmental in origin. In most domesticated species much research has been undertaken to discover how these factors operate, but unfortunately thorough investigations of this kind have not so far been carried out for the dromedary. Based on the available literature, an attempt is made here to explain some aspects of the reproductive anatomy, physiology and performance of the dromedary.
Early accounts of the anatomy of the reproductive system of the male camel (Cauvet, 1925; Leese, 1927; Tayeb, 1948) continue to serve as reference works on the subject. In this section the testes, tubular and copulatory organs of the male genital tract are described.
The testes of the camel are located in the perineal region, in a position similar to that of the dog (Leese, 1927) or boar. Each is contained in its own scrotum. Tayeb (1948) observed that the scrotum of the camel is generally covered by the tail but could be seen in the standing position. The scrotum is oval and sparsely covered with hair. A faint median raphe divides the two testicles. The camel testes have been described as being broadly similar to those of the horse, although differences become obvious on careful dissection.
The testes are oval in shape and in an animal of 3 years measure 7–10 cm in length, weighing 80–100 gm each. El-Wishy and Omar (1975) found the average length, breadth and thickness in 6- to 10-year-old camels to be 9.07, 5.08 and 4.43 cm respectively, with an average weight of 91.71 gm. They observed that the right testicle was often slightly smaller than the left one.
The internal structure of camel testes has been studied by Adel-Raouf et al (1975), who calculated the average diameter of the seminiferous tubules to be 210. While the diameter did not significantly differ between the right and left testes, it varied significantly (P< 0.005) according to season, being smallest during the summer (189.40—203.26) and largest in spring (209.68—226.20). Williamson and Payne (1978) also confirm that camel testes increase in size during the breeding season.
Abdel-Raouf et al also discovered a seasonal influence on the number of germinal cells, spermatogonia, spermatids and sperm cells, implying that the non-breeding season of the camel is characterized by reduced spermatogenesis rather than complete aspermatogenesis, as is found in some non-domestic ungulates. In this respect the Arabian camel studied was found to be very similar to the ram. The fluctuation in sperm cell numbers was confirmed in the quantitative studies of Osman and El-Azab (1974). They found that the testes of the camel are not only small for the size of the animal compared with other species, but also contain fewer cells per gram of testicular tissue when compared with the bull, buffalo, ram and boar. Estimated daily spermatozoa production rates in Egyptian and Sudanese camels were 8.1 and 5.6 (x109) cells during the spring, while in the autumn they were 4.2 and 3.2 (x109) cells. These values are much lower than the figure of 13.1 (×109) cells quoted for the bull.
Leese (1927) described camel sperm cells as resembling those of the ram. Khan and Kholi (1973a) studied the physical characteristics of camel spermatozoa and gave the following data: head length, 5.35 (5.08—6.35); head width, 3.42 (3.17—3.81); tail length, 35.62 (34.2—37.5); and overall length of the sperm, 48.37 (46.9—50.8).
The posterior border of the camel testis is convex and free. The anterior surface is flattened, except where the epididymis attaches to the anterior-dorsal point. Here the efferent ducts emerge from the gonadal interior. The tail of the epididymis is very closely apposed to the testicular surface by means of the epididymal ligament. Like most domestic species, except the horse, the camel testis has a well-defined mediastinum, and rudimentary testes have also sometimes been described in a ventral-anterior position in relation to the true testes. The vas deferens of the camel is remarkably twisted for much of its initial course, but becomes fairly straight towards the end portion. This peculiarity results in a thickened spermatic cord, which is relatively long and houses the vas deferens, the pampiniform plexus, spermatic artery, nerves, lymphatics and the internal cremaster muscle. The internal inguinal ring of the camel is very narrow.
Regarding the accessory glands of the male reproductive tract, both Leese (1927) and Tayeb (1948) described the presence of the prostate gland and the absence of seminal vesicles. The prostate gland is a discoid structure made of two lobes joined by one isthmus and located on the dorsal aspect of the pelvic urethra. It averages, 3–7 × 5 cm and is dark yellow in colour. Tayeb also described a dilated end of the vas deferens in an area generally occupied by the ampulla, which is usually described in a similar manner. There is no confirmation as to whether the dilation was in fact the ampulla or not. He also notes the additional presence of the bulbo-urethral (Cowper's) gland. The two units of the gland are located on either side of the terminal portion of the pelvic urethra. They are whitish, almond-shaped organs measuring 2.5 × 1.2 cm.
An interesting aspect of the copulatory organ of the male camel is the shape of its penile sheath. Early accounts of the structure present it as a voluminous, conical organ hanging from the abdomen like a large mammary gland. The point of the penile sheath is directed posteriorly and carries a very narrow orifice about 1.84 cm in diameter (Mobarak et al, 1972). Leese (1927) commented that this posterior orientation of the orifice results in the urine being directed backwards during micturition. Tayeb (1948) confirmed the above observations and added that the sheath has two pockets, one internal and one external. The sheath is dark in colour and, like the scrotum, sparsely covered with short hair. Its muscles are arranged in three groups (anterior, posterior and lateral), and their coordinated contraction and relaxation results in the forward and backward movement of the structure, or the constriction and dilatation of the preputial orifice. The anterior group of muscles is the largest and the lateral one the weakest. All insert into the inner surface of the skin covering the free part of the penis (Mobarak et al, 1972).
Within this massive casing the penis is hidden in its non-erectile state. It is a firm, cylindrical organ whose diameter generally decreases from the root towards the free end (glans penis). The average diameters of the root, middle and glans penis parts are given as 2.23, 1.64 and 0.42 cm by Mobarak et al (1972). A prescrotal sigmoid flexure is characteristic of the camel penis, dividing the organ into pre-, post- and intra-sigmoid portions. The average lengths of the three were estimated by Tayeb (1948) as 17.5, 17.5 and 25 cm, giving a total length of 60 cm. Leese (1927), and more recently Mobarak et al (1972), give average total lengths of 67.5 cm and 59.6 cm respectively. The penis originates in the region of the ischiatic arch via three cavernous bodies. The three are surrounded by a thick tunica albuginea which has a ventral urethral groove. The urethra proper is ventrally and laterally covered by the corpus cavemosum urethrae and dorsally by the tunica albuginea. Trabeculae from these outer layers penetrate the penile bodies in increasing amounts from the root end towards the glans penis. The caverns and cavities characteristic of the initial portion are therefore progressively replaced by fibrous tissue from the tunica albuginea. The septum between the two dorsal penile bodies tends to become ill defined towards the free end of the penis, which is elliptical caudally and ovoid cranially, where the cavernous nature of the caudal part of the penis is again more prominent. The urethra at this level is surrounded by the urethral body and assumes a left-sided rather than a middle position. At this level too, the urethral body is characterized by large blood vessels. The glans penis of the camel is shaped like a hook (Mobarak et al, 1972), curved along the vertical plane. Its features are a well-defined neck and a urethral process measuring 4–6 × 2 mm. This terminal portion of the penis feels cartilagenous to the touch and on cross-section a complete ring of hyaline cartilage filled with blood vessels may be revealed. On the outside of this ring there are many elastic fibres and caverns.
Muscles of the camel penis include the ischiocavernosi and the retractor penis. The blood supply of the male camel genitalia is similar to that of the bull and its nerve supply is typical of most domestic species. The camel penis is in general of the fibrous type, though some vascular elements are observed at the root and terminal parts. Mobarak et al (1972) classify the camel penis as intermediate between the fibrous and vascular types. The urethral body, however, consists primarily of vascularized tissue.
In this section the ovaries, tubular and copulatory portions of the female genital tract are described. Joshi et al (1978) noted that although the camel is a ruminant the reproductive tract of the female has some affinity with that of the horse.
The ovaries of the Iranian dromedary were found to have an average size of 13 × 29 × 33 mm and an average weight of 10 gm (Chahrasbi et al, 1975). The weight estimate is slightly higher than the range of 3.66 ± 1.49–8.51 ± 2.66 gm given by Shalash (1965), but the size is in agreement with the figures of 3–6 cm for length × 2.5–4 cm for thickness of Abdo et al (1968). The size and weight of the gonads are influenced by the stage of the reproductive cycle, i.e. by ovarian activity.
Shalash (1965) described the gonads as fairly flattened organs with numerous ovisacs, giving them the appearance of a bunch of grapes. The lateral surfaces, however, tend towards convexity. They are reddish in colour and each is enclosed in an ovarian bursa which ends blindly laterally but has a medially located opening where the fimbria are situated. Their suspensory ligament is a cord-like modification of the broad ligament.
Abdo et al (1968) studied both the micro- and macroscopic properties of the camel ovary. They concluded that though the shape, size and weight may differ from those of other species like the cow, ewe, sow and mare, the microscopic properties of both the Graffian follicles and the corpora lutea (CL) show no clear differences.
The Graffian follicles are randomly distributed on the ovarian surface and may sometimes (4.82%) be found even in pregnant animals. Those of the left ovary tend to be slightly larger than those of the right (1.24 as against 1.20 cm) (Shalash, 1965). While Musa and Sineina (1976) also describe follicular activity in pregnant camels, they assert that it decreases with advanced gestation. The endocrinology of pregnancy in the camel warrants further investigation.
Musa and Abusineina (1978a) estimated that follicles generally take about 6 days to grow to maximum size (range 2–14 days) and range from 1.5 to 3 cm in diameter, although sizes of 8–9 cm were also recorded. The grown follicle remains constant for 5–19 days (average 13 days) before regressing over a 7- to 10-day period. The growth of follicles to maturity alternates between the two gonads, but smaller follicles can always be palpated alongside them.
Abdo et al (1968) refer to the presence of CL during the luteal phase of the oestrous cycle of Iranian dromedaries. However, in the more recent study by Musa and Abusineina (1978a) involving 35 cycles over a 15-month period, no luteal phase was demonstrated, ovarian activity being mainly follicular.
The CL is thus normally observed only during pregnancy in the camel. Its shape varies between spherical, elongated and oval, and in early gestation it has a flabby consistency, becoming larger and firmer as pregnancy advances. A neck-like constriction is observed at the point where it attaches to the main ovarian body. The CL of pregnancy is light brown with a greyish central cavity, and variable numbers (one to three) of CL may be found on the same ovary, their size varying from 1.85 to 1.88 cm and their weight from 4.15 to 4.68 gm (Shalash, 1965).
Both Shalash (1965) and Musa and Sineina (1976), who examined 787 and 416 reproductive tracts respectively, agree that there is more (12.98%) ovulation from the left than the right ovary and that pregnancy in the camel is almost exclusively left-sided (99%). Cross pregnancy, where the pregnancy is maintained by a CL on the opposite side, is very common (37.73%). The explanation is probably that early embryonic migration is frequent among dromedaries. That more CL than viable embryos are seen in the camel also suggests a high rate of early embryonic mortality. Both twins and triplets are very rare in the species, an observation born out by the Arab saying that one is more likely to see the moon on earth than the birth of live twins in the camel.
Since most CL in the camel are observed only during pregnancy or in the few cases where the uterine opening is patent, it would appear that some type of stimulation, e.g. copulation, is necessary for ovulation to occur (Shalash, 1965). Musa and Abusineina (1978a) confirm that ovulation among Sudanese dromedaries is non-spontaneous, requiring copulation beforehand. However, even 15 minutes of experimental cervical stimulation by palpation failed to induce ovulation, although leutinization of the Graffian follicle was produced. The camel is thus an induced ovulator like the cat and the rabbit. Copulation apparently triggers the release of the gonadotrophins essential for ovulation to occur, approximately 36 hours later (Williamson and Payne, 1978).
An account of the anatomy and histology of the female dromedary gonads is given by Tayeb (1950a) and this work is recommended for further details.
The oviducts of the camel are small in diameter (1–2 mm), but become larger at the ovarian end where the fimbria are located.
The dromedary has a bicornuate type of uterus. It is a large organ whose weight may vary from 193.7 to 376.4 gm (Shalash, 1965) depending on the phase of the oestrous cycle. Generally it is located in the abdominal cavity, but Musa and Abusineina (1978b) observed that open uteri and those with early pregnancies are sometimes located intrapelvically. However, these observations were based on per rectum examinations of recumbent camels. The uterus is reddish white, shiny and smooth with a short body. Its two horns are closely apposed externally but clearly separated by a median septum internally. Their anterior end is marked by what is almost a T-junction, and generally the left horn is the larger (Joshi et al, 1978). The camel has a diffuse placenta, the mucous membranes of the uterine body and horns being smooth and devoid of cotyledons. Histologically, the pregnant camel has an epithelial-chorial placenta similar to that of the horse (Novoa 1970).
The camel cervix, like that of the cow, has a number of mucosal folds arranged in three or four rows. The cervical canal is short (3.5 cm), with a diameter of about 5.5 cm, while the external opening is relatively large (3.5 cm). Like the cervix of the zebu cow (Bos indicus), that of the dromedary tends to hypertrophy and protrude some distance into the vagina, resulting in the formation of two blind sacs (one dorsal and one ventral). Anteriorly, the mucosal folds of the cervical canal form a prominent crest which marks the cranial opening of the cervix.
The vagina is an elastic organ of reddish colour measuring 30–35 cm and lined with mucosal folds posterior to the external cervical opening. Both longitudinal and circular folds have been demonstrated, although the latter are the more pronounced. With advanced pregnancy there is a tendency for the uterine weight to stretch out these folds.
Leese (1927) described the canals of Gartner and the glands of Bartholin in the camel. Tayeb (1953) indicated that these canals are located in the vaginal wall. They originate in the region of the external cervical opening. He also gave an account of the blood and nerve supplies of the reproductive tract.
The camel vulva is about 8 cm long. On its ventral floor it has a suburethral diverticulum, on top of which is located the true urethral orifice. The demarcation between the vagina and the vulva is marked by the hymen or its remnants.
Puberty is the age at which an animal first becomes capable of reproduction, while at sexual maturity this capability is increased to the optimum level.
Wiltbank (1974) stressed that the attainment of puberty in cattle is influenced by the age and weight of the animal. A heifer may reach puberty earlier if she is of the right weight. This principle is well understood and applied for many domestic species. Unfortunately the camel has a slow rate of growth (Chatty, 1972) and this genetic handicap, in addition to the general lack of feed supplementation under pastoral management systems, results in advanced ages at puberty for the dromedary.
Williamson and Payne (1978) and Matharu (1966) estimated that the sexual maturity of dromedaries occurs at 3 years. Spencer (1973) observed that the Rendille camel of northern Kenya may reach 6 years before getting her first calf. Allowing for a year's gestation period, this would give an age of 5 years at first conception. Singh (1966) wrote that the age of first sexual desire among male camels in India was 2 years but that full musth was delayed until 8 years, although the animals could be sparingly used for service at 6 years. Leupold (1968a) is of the view that both sexes attain sexual maturity at 3 years. However, Khatami (1970) indicated that both the Iranian female and male camel reach sexual maturity at the age of 5 years.
It is common practice to withhold female camels from breeding until they are 4–6 years old (Williamson and Payne, 1978; Matharu, 1966). This practice doubtless results from the fact that fecundity continues to increase with age, even after sexual maturity, and only starts to decline with senility. Since the gestation period is about a year, age at first calving therefore averages between 5 and 7 years, a much later age than in cows. However, this disadvantage is largely offset by the camel's longer breeding life.
The length of the camel's reproductive life varies, but some females continue to breed until 20 years old. Cossins (1971) reports a camel cow of 30 that had had 15 calves. When well fed and managed some camels live up to 40 years, and in spite of a calving interval approaching 2 years the camel is still capable of producing as many progeny as most pastoral cattle. Spencer (1973) indicates that the Rendille camels of northern Kenya can produce as many calves as the Samburu cattle.
The calving interval in camels is prolonged not only by their limited breeding season but also by the suppression of oestrus for a long time after parturition. Postpartum oestrus is normally delayed for about 1 year, although a few females come back into heat as early as 1 month after parturition (Williamson and Payne, 1978). The level of nutrition is a factor here, since when feed supplies are inadequate, maintenance, growth and lactation take priority over reproductive performance, which becomes a physiological luxury. At any rate camels usually calve only every other year, or at best twice in 2 years. The theoretical maximum annual calving rate is thus 50–80%.
Among male camels, which are often not put to full service until they reach 6–8 years, rutting or musth is generally limited to particular periods of the year, as it is in the female. It is partly influenced by age and level of nutrition. The breeding season, which often coincides with the rains, lasts about 3–5 months on average, but for some animals, especially older ones, the period may extend throughout the year (Williamson and Payne, 1978). The latter authors further observed that there was no specific rutting season for animals on or near the equator (probably within the tropics), where rutting may take place throughout the year.
During the rutting period the usefulness of the male as a work animal is diminished; he loses his appetite, develops occasional diarrhoea and displays abnormal behaviour patterns.
Mimram (1962) has reviewed in detail the occipital glands of female, male and castrated dromedaries. Among rutting males the occipital glands tend to secrete more profusely (Matharu, 1966; Fraser, 1968). Rutting males constantly protrude the mucosa of their buccal cavity, which expands into a balloon-like structure. They become irritable and rarely tolerate rivals. Wind sucking and belching also occur continuously in rutting stallions, which attempt to mate with most females, even those not in oestrus. Their increased activity and lack of appetite often result in a loss of condition at the end of the breeding season.
When many males are herded together, usually only one (the strongest) will "develop the rut". If more than one develop the rut a fight will often build up until the weaker submits and suppresses his sexual desire (Singh, 1966). Fraser (1968) also considered the voluntary suppression of breeding instincts to be related to the male's status in the hierarchy of the herd. Sexual desire can be quelled if rutting males are driven hard at work.
A number of studies have been performed on the haematological characteristics of camels before, during and after the breeding season, but the results so far obtained lack consistency, even as regards the average values of the major blood constituents. However, Khan and Kholi (1978) obtained a statistically significant (P<0.01) drop in blood haemoglobin and an increase in total leucocytes during the breeding season.
There is considerable divergence as to the ideal ratio of males to females during the breeding season. Estimates vary from as low as 1 male per 5–7 females (Watson, 1969), through medium levels of 1:10–30 (Asad, 1970; Gauthier-Pilters, 1959) to as high as 1:50–80 (Williamson and Payne, 1978; Singh, 1963 and 1966; Leupold, 1968a). Major determining factors include the management practices of pastoralists, the condition and stamina of the male, his libido and the fertility level of the females. Demand on the part of herders for service by particular sires as well as the fee which may be charged by the owner of the male could also adjust the ratio upwards. Droandi (1936) and Burgemeister (1975) indicate that a camel stallion can breed three females per day at the peak of the breeding season, although higher levels are possible.
Males not reserved for breeding are often castrated. Castrates are more manageable and make better working animals. Cossins (1971) indicated that castration may also be carried out for meat production purposes. The ideal age at which to castrate camels is 4–6 years. Droandi (1936) gives a detailed description of castration methods used by the Arabs. The operation may be carried out in any season, provided the animals are healthy enough to withstand the stress involved.
The animal is first hobbled and turned on its side or back, with all its limbs immobilized. The open castration method involves the use of a razor, a palm branch, two iron cauterizers and a small rope. Healing following open castration usually takes 30–40 days, and there may be extensive swelling or discharge from the wound. A simpler castration method consists of merely twisting the spermatic cord, and in this case healing occurs more rapidly, often requiring only 2 weeks.
After reaching sexual maturity the female dromedary exhibits regular oestrous cycles, which nevertheless seem to be limited to particular periods of the year. However, Nawito et al (1975), cited by Williamson and Payne (1978), imply that the Egyptian dromedary may conceive at any time of the year, although there is still considerable variation in conception between seasons. In India and much of the northern hemisphere the breeding season extends from November to March. It is influenced by the level of nutrition and changes in daylight length, among other factors. Altitude and atmospheric humidity may also play a part (Dahl and Hjort, 1976). The findings of Shalash (1965) clearly illustrate a breeding periodicity of this kind (see Table 2). According to Novoa (1970), Bosaev (1938) indicated that while the domestic Bactrian camels of Russia are polyoestrous throughout the year, the wild Bactrian camels are only seasonally so. Novoa states that sexual activity among Camelidae in general appears to be very variable, and that the factors influencing its nature and duration are still largely unknown.
Table 2. Monthly variation of ovarian activity in the camel.
Month |
Ovaries with: |
Total functioning ovaries | |||
No |
Graffian |
CL of |
Number |
% | |
January |
76 |
30 |
113 |
143 |
8.28 |
February |
38 |
20 |
33 |
53 |
3.07 |
March |
34 |
24 |
99 |
123 |
7.12 |
April |
40 |
48 |
173 |
221 |
12.79 |
May |
50 |
24 |
107 |
131 |
7.58 |
June |
88 |
20 |
51 |
71 |
4.11 |
July |
90 |
18 |
18 |
36 |
2.08 |
August |
22 |
6 |
2 |
8 |
0.47 |
September |
48 |
10 |
23 |
33 |
1.91 |
October |
46 |
4 |
13 |
17 |
0.98 |
November |
39 |
25 |
44 |
69 |
4.00 |
December |
113 |
29 |
116 |
139 |
8.05 |
Once the breeding season has started the female camel will come into heat every 20–25 days (average 23.4 days; Joshi et al, 1978). Longer durations, e.g. 28 days (Musa and Abusineina, 1978a), have also been observed. In cattle, these extended oestrous cycles are often associated with silent or unobserved heat periods and the same may well be true of dromedaries also.
The oestrous period itself generally lasts 4–6 days (Joshi et al, 1978) although a range of 1–7 days is given by Parkes (1969). Both these findings are slightly shorter than the range of 6–8 days given for the Bactrian camel by Williamson and Payne (1978).
In a well organized study Gupta et al (1978) showed that female camels in India usually come into oestrus five times in a breeding season. They remain in oestrus for 4–5 days, but the chances of conception decrease as the period progresses. The results of these authors, based on only a small number of animals, are shown in Table 3. Skillful management could become important here, since if hand mating were used in the early stages of the oestrous period to obtain the best conception rates, overall fertility would be improved.
Table 3. Effect of service at different stages of the oestrus period on conception rates in the camel.
No. of animals in group |
Group of animals and day of oestrus when exposed to the male | |||||||||
1 |
2 |
3 |
4 |
5 | ||||||
8 |
8 |
8 |
8 |
7 | ||||||
No. of animals conceiving during: | ||||||||||
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) |
(a) |
(b) | |
1 st cycle |
4 |
4 |
4 |
4 |
2 |
2 |
3 |
3 |
1 |
1 |
2nd cycle |
1 |
5 |
2 |
6 |
1 |
3 |
2 |
5 |
3 |
4 |
3rd cycle |
3 |
8 |
2 |
8 |
2 |
5 |
– |
5 |
1 |
5 |
4th cycle |
– |
– |
– |
– |
2 |
7 |
3 |
8 |
1 |
6 |
5th cycle |
– |
– |
– |
– |
– |
7 |
– |
– |
1 |
7 |
No. of services per conception |
1.87 |
1.75 |
2.75 |
2.12 |
2.71 | |||||
During the oestrous period the female dromedary shows both anatomical and nervous signs of heat. She is generally restless, seeking the company of the male and tending to bleat continuously. She develops a swollen vulva, often associated with a discharge (Singh, 1963 and 1966). Droandi (1915) observed that oestral camel cows emitted a penetrating, foul smell from the vulva that could be smelt over long distances, but which had an excitative effect on the males. He noted that the vulvar lips contracted and swelled at intervals and that the animals tended to raise their tails and micturate more frequently during oestrus. Females at this time are generally capricious, and when forced to work are excited by weights applied to their flanks.
Joshi et al (1978) have studied the oestrous cycle of the Bikaneri camels of India in detail. They observed that the vagina appeared moist and light pink in colour during pro-oestrus. It became moist and red during oestrus itself, though the moistness decreased as oestrus drew to an end. Similar changes were observed in the vestibular mucosa. Superficial flat cells with eosinophilic cytoplasm and pyknotic nuclei were found to be characteristic of vaginal smears during oestrus, while intermediate cells were predominant in smears from pregnant animals. Vaginal examination showed that the cervix was moist and relaxed during oestrus. On per rectum examination the uterine horns were turgid at the beginning of oestrus, but turgidity was not as marked as in cattle. Numerous Graffian follicles were palpable on both ovaries but no CL could be felt during any part of the oestrous period.
Leese (1927), Fraser (1968) and Burgemeister (1975) described copulation among camels, a process labelled as secretive by Matharu (1966). Fraser (1968) noted that mating behaviour among camels differs from that of other ruminants, and indicated the essential relationship between conformation and mating behaviour.
Copulation often starts with courtship involving a necking exercise. Khan and Kholi (1973b) indicate that in courtship the male may not only smell the female genitalia but may even bite her in this region, or around the hump. Bleeding due to severe bites is not uncommon.
Often the strong male may simply round up the female and crouch her after exhaustion for service (Hartley, 1979). Usually the male induces the female into a sitting position, and those in oestrus, especially those in season for the first time, will readily assume this position. The male then grasps the female with his forelegs, while most of his weight rests on his buttocks, with all the joints in his back legs flexed. The animals thus face in the same direction. During a single mating session the male may ejaculate three or four times, each service being preceded by fresh penile penetration.
It is common for camelmen to aid the entrance of the male penis into the female genitalia, although males are also believed capable of locating the vulvar opening by themselves by rotating the erect penis on its longitudinal axis. In Somalia, Hartley (1979) noted that hand service by herdsmen well known to the male camel is common. The method is used to select a female for service and she is usually served twice. However, there is a lack of agreement as to whether the male camel is always assisted to effect penetration. Those who accept the argument of assistance use it to justify the lack of wild camels, allegedly caused by an inability to copulate. The Australian feral herd, however, continues to expand in the wild. Another explanation might lie in seasonality, combined with the f act that generally only one male develops the rut during the breeding season. It is possible that the male becomes overworked as the season progresses, resulting in a drop in sexual drive.
Copulation among camels may last for a short time––12–30 minutes, according to Rakhimzhanov (1975), Leese (1927) and Burgemeister (1975)––or for an hour (Droandi, 1915). Leonard (1894) suggested that mating could last the whole day, with breaks for the male to ward off any external disturbances. Other camels often gather around the copulating couple. At the end of the mating act the male tends to gurgle and froth at the mouth, while the female is inclined to bleat excessively.
Using the artificial vagina method, Khan and Kholi (1973b and c) estimated the volume of Bikaneri camel ejaculates to average 3.1 ml (range 1–10 ml). Though subject to individual variations the trait was unaffected by age. Semen appeared white in colour with a thick viscid consistency and had an average pH of 7. 8 (range 7.2–8.8). The mass motility and the percentage of spermatozoa showing progressive motility improved with subsequent ejaculates.
The gestation period of the dromedary is often quoted as about 1 year, with a range of 355–389 days being given by Burgemeister (1975), Williamson and Payne (1978), Leonard (1894) and Leupold (1968a). The breeding season thus occurs at the same time of year as the calving or foaling period. The gestation period of the Bactrian camel is slightly longer, averaging 13.5 months (Dahl and Hjort, 1976).
Various methods have been developed for determining pregnancy and estimating its duration in the camel. Mares (1954) observed that female camels tend to dry off naturally after conception. Field (1979a) reported that lactation ceased 4–8 weeks after pregnancy in female camels of northern Kenya. However, there are also reports of camels continuing to lactate for 12- to 18-month periods. Whether the latter category of animals were empty or pregnant is unclear, but Knoess (1976) referred to a pregnant camel that was still giving a considerable amount of milk. Until it can be established whether or not the camel exhibits lactational anoestrus, the observation cannot be relied upon as an efficient means of pregnancy diagnosis.
Camels are known to reject further breeding after conception, and oestrous cycles are normally discontinued. In cattle, however, 5% of animals tend to come back into oestrus in spite of positive conception, and in camels Shalash (1965) observed Graffian follicles in 4.82% of pregnant uteri. The rejection of breeding cannot therefore be used as a conclusive indicator of pregnancy.
Mares (1954) concluded that the pregnant camel has a characteristic way of lifting her tail when approached by a male or handled by a man, an observation which Singh (1966) considered a reliable sign of pregnancy. Musa and Abusineina (1978b) have nevertheless cast doubt on its accuracy. They observed that female camels "cocked" their tails during anoestrus, oestrus or pregnancy. On the other hand, they reported the successful use of rectal palpation to diagnose pregnancy in the camel. As it does in cows, the method involves palpation of the uterus, its contents and blood supply. The authors found that the presence of one or more well-developed CL was highly suggestive of pregnancy. They also described the position and characteristics of the uterine arteries in six camels throughout the gestation period, comparing their findings with those for the cow.
Other methods for diagnosing pregnancy in the camel include the ballotement of the foetus through the right flank, a method limited to the later stages of gestation. Mammary gland hypertrophy may indicate pregnancy in the camel, but like abdominal enlargement and ballotement this indication becomes reliable only in the last trimester. In primiparous females, however, abdominal enlargement may be observed as early as 6 months, but caution should always be exercised in using this method since other conditions (e.g. ascites and flatus) may also cause abdominal enlargement and thus simulate pregnancy. Recently, Schels and Mostafawi (19791 have reported good results using the ultrasonic method for pregnancy diagnosis in 15 Iranian camels. Twelve out of 15 5- to 11-year-old females were positively diagnosed.
Signs of imminent birth in the camel include a relaxation of the sacrosciatic ligaments resulting in two grooves, one on either side of the tail. The animals become lethargic and develop an oedematous swelling of the vulva. Colostrum can be drawn from the teats, which are engorged during the last days of gestation.
In a study of 17 pregnant camels, Burgemeister (1975) found that the external signs of imminent parturition in the camel were not very pronounced. He noted that the abdominal pains usually associated with the onset of dilation were not very severe in the camel. However, he also observed that 3–5 hours before delivery females tended to show agitated behaviour. They lie down more frequently and their feeding becomes disturbed. Leese (1927) had noted similar behaviour to that observed by Burgemeister, but concluded on the contrary that labour pains are more pronounced in the camel than in the cow or mare, and added that sometimes it may be advisable to tie down timid (and especially primiparous) females.
The onset of abdominal pains was taken to indicate the beginning of the first of the three stages of parturition observed by Burgemeister (1975). The three stages, dilation, delivery and expulsion are reproduced in Figure 4, where the duration of each is shown.
Figure 4. Duration of stages of parturition in 17 camels studied.
Source: Adapted from Burgemeister, 1975.
Parturition generally occurs with the dam in a lying position, although delivery in the standing position is also possible (Gauthier-Pilters, 1959). Most females will deliver unaided, but camelmen are willing to provide extra help when necessary. The anterior longitudinal presentation (forelegs of the foetus being presented first); dorsal position (the back of the foetus being directed towards that of the dam) and extended posture (all the limb joints being fully extended) were the norms encountered in the camels noted by Burgemeister.
There is little significant difference between the pelvic measurements of the dromedary and the Bactrian camel. However, while the delivery process on average takes 24 ± 2.34 minutes in the former, it is longer (40 ± 2.63 minutes) in the latter, probably because the Bactrian calf is larger (Moldagahev, 1976). The duration for the dromedary is slightly higher than the average of 19 minutes calculated from the data given by Burgemeister for the Tunisian camel (Figure 4).
Of the 17 animals studied by Burgemeister only 4 migrated from the main herd during calving, despite the opinion of Richard (1976) that one reason why brucellosis was not prevalent among camels was the tendency of females to stray away during calving.
The third stage of parturition (expulsion of the foetal membranes) lasts about 15 minutes but it is also common for the placenta, which is diffuse, to be shed together with the newborn (Singh, 1966). It should be noted that there is an extra foetal membrane in the dromedary (Musa, 1979). This membrane is epidermal in origin and surrounds the entire foetus except at the lips, vulva, prepuce, anus, umbilicus, teat orifices and hooves. All body orifices are therefore open to the foetal (amniotic) fluids, while the rest of the body is separated from them. The same author observed that the average volume of foetal fluids in the dromedary was 9 litres at parturition, the allantoic fluid averaging 80–90% throughout gestation.
Burgemeister indicated that females stand up soon after delivery. It is by standing up that the umbilical cord is severed (Leese, 1927). The camel does not generally lick its young as do the cow and the mare (Fraser, 1968), but it is an excellent mother (Matharu, 1966 and Droandi, 1915).
After delivery camel herders often dry the calf with a sack or straw and shelter it away from cold draughts and wind.
Williamson and Payne (1978) report that some camelmen work their pregnant animals up to the time of delivery, and return them to work soon after. Other camelmen, however, carefully look after their pregnant stock, dividing those about to deliver into a separate group which may sometimes receive extra feed and care. Pregnant camels should be maintained on good pasture during the last 2 months of gestation and for a minimum of 3 weeks after delivery.
In a study carried out at a government camel breeding farm in India, Bhargava et al (1965) reported on the birth weight of Bikaneri camels. The smallest calf weighed 26.3 kg, half the weight of the heaviest calf, which was 52.15 kg. The average birth weight for males was 38.19 kg and for females 37.19 kg, with a pooled average of 37.23 kg. In this study, which involved 134 records over a 3-year period, the sex of the calf, the calving sequences and the month of calving apparently had no statistically significant effect on birth weight. The sex of the calf has, however, often been found significant for other domestic species. Brinks et al (1961) are among the many authors who have shown it to be a significant source of variation in bovine birth weights, irrespective of the age of the dam. Heifer calves weigh 7% less than bull calves. In pigs Johanson and Rendel (1968) indicated that male piglets outweighed females by 50 gm, while in sheep ram lambs outweighed ewe lambs by approximately 5%.
Burgemeister (1975) recorded the birth weight of Tunisian camel calves as 25.81 ± 2.14 kg, lower than the average weights of 37.23 kg given for the Indian dromedary and 30.9 kg recorded by Field (1979a) for Rendille and Gabbra calves in Kenya. Burgemeister further recorded the shoulder height of the calves as 95.4 ± 2.34 cm, taller than the estimate of 75 cm given by Leonard (1894) for the Arabian camel. Such differences reveal the variations in camel calf performance attributable to breed, strain, environment and management.
Heredity is another factor affecting prenatal growth, directly via the genotype of the foetus and indirectly through the genotype of the dam. A positive correlation exists between maternal body size and age and the prenatal growth rate of the foetus. According to Johansson and Rendel (1968) birth weight is influenced by the sum total of factors contributing to the nourishment of the foetus in the uterus. Hansard and Berry (1969) summarized the factors influencing the birth weight of animals and estimated that the largest component of variation (36%) is attributable to the combined genotypes of the dam (20%) and foetus (16%), followed by intra-uterine foetal environment (30%), maternal environment (18%), parity (7%), nutrition (6%), sex (2%) and maternal age (1%). The exact role of these factors in the camel has not been investigated.
The nutritional status of the dam may also have a direct bearing on foetal growth, a factor which would seem to be important in the camel: poor nutritional levels during gestation may lead to increased perinatal mortality. Nevertheless, Musa (1979) studied the development of the camel foetus and its associated growth curve, concluding that there was a striking similarity to the pattern for cattle. The growth curve of the dromedary foetus is shown in Figure 5.
Figure 5. Prenatal growth of the camel foetus.
Source: Adapted from Musa, 1979.
Pre-and postnatal body growth is also affected by a number of hormones. Dickson (1933) indicated that somatotropin and other pituitary hormones are responsible for growth, but that the role and extent of each varies between species and is not yet known for camels. The same author also indicates that although the thyroid gland hormone (thyroxine) is essential for prenatal growth, it only comes into play during the terminal stages of gestation.
Burgemeister (1975) studied the weekly postnatal growth performance of young dromedaries. The results of his observations are given in Figure 6. They show that male calves tend to grow faster than female ones. Field (1979b) observed the growth patterns of camel calves in northern Kenya. Two groups of animals were studied, one under Rendille pastoralist conditions and another under special project conditions whereby the young received at least 75% of their dam's milk. The former group showed average daily gains of 222 gm and 255 gm during the dry and wet seasons, while gains ranged from 378 gm to 655 gm for the latter group. These figures reflect the important influence of dam milk on growth and indicate the negative effects of competition for milk between calf and man under the pastoralist management system. The postnatal calf growth curves given by Field also show a better performance by calves born during the wet season, irrespective of the breed of camel. However, their advantage is not a permanent one, since calves born in the dry season appear to catch up after 9–12 months by means of compensatory growth.
Figure 6. The postnatal growth performance of young dromedaries.
Source: Burgemeister, 1975
Although the lactation period of the female camel may last up to 2 years, the suckling young are generally weaned much earlier, at any time between 3 and 18 months under traditional pastoral systems, the average being 12 months. Camel calves begin to graze when they are only a few weeks old, the change from milk to more solid food occurring gradually and with few effects on growth (Williamson and Payne, 1978). Field , on the other hand, observed in his study that weaning results in a check on camel calf growth, citing one case where the liveweight gain dropped from a preweaning level of 410 g per day to 317 g per day during the 6-month period after weaning.
Prenatal losses seem to occur more frequently in the camel than in other domestic species. Embryonic mortality, often associated with genetic causes, has been cited as a significant factor. Musa and Sineina (1976) found two or three CL in 13.65% and 1.22% of 491 single births, whereas the twinning rate was only 0.4%. Leonard (1894) wrote that only one calf is produced by the camel and Leese (1927) stated that he had never seen nor heard of twins or triplets being born alive to a camel. These observations, together with the histolological evidence of Shalash (1965), clearly indicate the early occurrence of embryonic mortality, although the latter author found conclusive evidence of mortality in only a few of the camel tracts examined.
The causes of embryonic deaths include various pathological conditions such as metritis and pyometra, as well as genetic abnormalities resulting from inbreeding; hormonal disturbances and so on. Burgemeister (1974) points out that in Tunisia it was customary to service females with a sire from the herder's own colony, thereby increasing the level of inbreeding. One of the detrimental effects of inbreeding is the depression of lowheritable characters such as fertility, reflected in increased abnormal germ cells and the early degeneration of zygotes and embryos. This abnormality is well known in bulls (Mukasa, 1974) and other domestic animals, and there is little reason to doubt its occurrence in camels also.
Prenatal deaths in many species are frequently followed by embryonic resorption and a return to oestrus. However, since the camel has limited annual breeding period, the repeat-breeder camel would be unlikely to come back into season before the following year. The death of larger embryos may be followed by the invasion of supurative bacteria leading to maceration. Alternatively, bacterial invasion may fail to occur, the dead organism being retained in a sterile state as a mummified foetus.
Abortions and stillbirths both occur in the dromedary. Droandi (1936) observed that abortion in camels was by no means rare, and that a major cause was probably that pregnant females are frequently overworked. He noted a practice common among the Arabs, whereby females were even denied rest while in labour, in order to avoid falling behind on long marches. Delivery was speeded up by pulling out the head and legs of the calf, which was then wrapped in a bag and carried with the rest of the baggage. Practices of this kind may well lead to subsequent reproductive problems. Richard (1976), Fazil (1977) and Curasson (1947) attributed abortions in the dromedary to trypanosomiasis. Other causes include febrile conditions such as pneumonia and camel pox, or nervous excitement (Leese, 1927). Pasteurellosis and salmonellosis have also been cited.
Spencer (1973) reported a low growth rate of Rendille herds in northern Kenya and attributed it partly to the high incidence of diseases affecting reproductive performance. Shalash (1965) found indications of infection in nearly half the female genital abnormalities examined. One of the infectious conditions observed by the latter was pyometra, sometimes associated with maceration of the foetus. Bursal and ovarian adhesions are often subsequent complications of this condition. Infections of the genital tract usually follow difficult parturition, retention of foetal membranes or trauma (Roberts, 1971). Paraphimosis and phimosis were described in camels by Leese (1969). They are mainly the result of inflammation of the prepuce. He also described orchitis due to trauma, followed by infection of the wounds on the scrotum.
It is not infrequent for deaths to occur during delivery itself. Losses are caused by difficult calving, sometimes compounded by the unskilled intervention of the herdsman. Leese (1927) indicated that human assistance during delivery is rare under normal conditions, but added that newborn calves can be lost through umbilical haemorrhage, the incidence of which can be reduced by the proper ligation of the cord.
Williamson and Payne (1978) stated that the newborn camel is a very, delicate creature and that losses are high in the first 3 weeks of life, a view also shared by Singh (1966).
Fazil (1977) wrote that a female camel in good condition may produce too much milk for the calf's needs. Overfeeding may result in diarrhoea, indigestion and sometimes death. Colostrum, in spite of its laxative and immunological advantages, is considered dangerous by most camel herders and is commonly fed only, in minimal amounts (Williamson and Payne, 1978). However, when colostrum is withheld to a substantial degree the calf may be deprived of the protection provided by the antibodies it contains, which are essential for body defence and resistance mechanisms during early life. Most calves become unthrifty and many die if deprived in this way. Calf mortality among camels was estimated at 50% by Leonard (1894), 30–50% by Bremaud (1969) and 31–59% by Cossins (1971).
In addition to overfeeding or lack of colostrum other causes of early calf mortality have been observed. In a study of three camel raising clans of the Jijiga area of Ethiopia, Cossins (1971) recorded mortality rates of 31, 49 and 59%. He attributed the latter two high values to the fact that the herds were maintained all the year in tick-, fly- and predator-infested areas. Bremaud (1969) attributed calf mortality in the camel herds of Kenya to poor nutrition, diseases and predators. He noted that owners did not consider the 30–50% calf losses as a serious problem. Field (1979a) surveyed 204 deaths among the camels of northern Kenya and found that 92 (45%) occurred at under 2 years. Major causes included drought (35%), ticks (22%) and camel pox (16%). Leonard (1894) was of the view that the premature weaning of suckling calves and the early age at which the young are made to begin work also contribute to mortality within the first 4 years of life.
Curasson (1947) quoted Droandi, who considered polyarthritis as a common ailment in young camels following infection through the umbilical cord, with symptoms and lesions similar to those observed in the horse. In a study of young camels in Tunisia, Burgemeister (1975) observed that of 26 pathological conditions diagnosed at or soon after birth, the commonest was ‘arthrogryposis' (16.4% of the 73 animals examined), followed by asthenia (12.3%), polyarthritis (2.74%), traumatic arthritis (1.37%), congenital abnormalities of the stomach (1.37%) and fractures (1.37%). Overall, he concluded that 26% of young camels are lost before the age of 6 weeks.
Fertility has been defined as the ability of the male and female to produce viable germ cells, mate and conceive, and subsequently give rise to living young (Ensmiger, 1969). Many factors, including perinatal losses, influence the overall fertility rate of domestic animals, with the result that rates are difficult to define. A significant aid in establishing precise figures is the keeping of proper breeding records, a management practice entirely lacking among camel herders under traditional systems. However, it is generally believed that fertility rates in the camel, especially under traditional systems, are low.
Dahl and Hjort (1976) have noted that even under improved management the fertility rate of camels is very unlikely to be much higher than 50% in pastoral herds. The authors, however, quote Russian work in which the fertility level of the Bactrian camel was found to be 65% under ranch conditions, although Keikin (1976) reports the calving rate at a large Soviet camel ranch (4,300 head) as averaging only 40%.
Contrasting methods of estimating fertility in camels were used by Bremaud (1969) and Wilson (1978). The former used direct interviews with the pastoralists, while the latter employed aerial surveys of the various age groups to determine fertility indices. Bremaud, whose results are partly reproduced in Table 4, estimated the fertility rate of Grabbra and Somali camel herds in Kenya as 34% and 52.25% and quoted Watson's (1969) figure of 41%. The results indicate that 80% of animals had a calving interval of at least 2 years, that 73 9o did not rebreed within 12 months of calving and that 74% of young are weaned at 12 or more months of age. However, the data base was very limited, and in the absence of proper breeding records results based on interviews with nomads should in any case be accepted with reservation. Bremaud himself confesses a bias in his own results, since calf mortalities remained unaccounted for, and also nomads probably tended to report only on their best-performing females. His figures for fertility rates should therefore probably be scaled down. Wilson (1978) gave the calving rate of Darfur camels in southern Sudan as 70%, which seems a very high estimate under pastoral conditions.
Table 4. Fertility characteristics of camels of northern Kenya.
Characteristic |
Number (and %) of animals |
Calving interval (months) | |
12 |
1 (3.8) |
14 |
1 (3.8) |
15 |
1 (3.8) |
16 |
1 (3.8) |
24 |
14 (53.8) |
30 |
1 (3.8) |
36 |
1 (26.9) |
Time between calving and rebreeding (months) | |
1–3 |
1 (3.8) |
3 |
2 (7.7) |
6 |
2 (7.7) |
7–11 |
19 (73.0) |
Age of calf at weaning (months) | |
3 |
1 (3.7) |
6–11 |
6 (22.2) |
12 |
17 (63.0) |
24 |
3 (11.11 |
As the previous sections have indicated, the factors contributing to low fertility in the camel are many and complex. They may briefly be summarized as follows:
Puberty occurs late in the camel, and animals may be 3–5 years or more at sexual maturity. Inadequate weight, resulting from a low plane of nutrition, may well be a cause of delay. Females are commonly withheld from breeding until 4–6 years old. Gestation accounts for a further year, with the result that calving frequently occurs for the first time at 5–7 years, considerably later than in cows. This factor is partially offset by the camel's longer breeding life.
Full male musth may in some cases occur only at 8 years, and animals are often not put to full service before 6–8 years. In addition it is reported that only one male in the herd develops the rut, while the others suppress their sexual desire. This situation, together with a loss of appetite and increased activity noted in males during the breeding season, may lead to a loss of condition and subsequent drop in libido. Difficulties in male penetration may also play a part.
Although animals near the equator are reported to breed all the year round, the breeding season elsewhere generally appears limited (November to March in the northern hemisphere). Length of the breeding season is probably affected by nutrition levels and daylight length, and possibly by other factors such as altitude and air humidity. Since gestation usually lasts a year, the breeding season tends to occur at the same time as calving, limiting the number of females able to conceive. When prenatal deaths occur, rebreeding is usually delayed until the following year.
Camels calve once every other year, or at best twice in 2 years. The result is a low annual calving rate of 50–80%. The calving interval is prolonged by (i) the lengthy gestation period, (ii) the limited breeding season and (iii) late postpartum oestrus (frequently 1 year after parturition).
Low feed availability, especially in times of drought, may affect overall fertility in a variety of ways, ranging from delayed sexual maturity and a curtailed breeding season to threatened calf viability. When feed is scarce, growth and lactation take priority over reproduction, which becomes a physiological luxury. Under pastoral systems, competition for milk between calf and man becomes an additional factor. Again, colostrum is commonly withheld from calves, depriving them of essential antibodies, while early weaning may check calf growth, increasing susceptibility to disease. Conversely, overfeeding may also be a problem in times of plenty, leading to diarrhoea, indigestion and in some cases death.
Management practices, as well as disease, emerge clearly as a crucial factor in the high calf mortality rate of 30–60%, and doubtless also affect embryonic and foetal losses as well as other aspects of fertility. Better and more widespread knowledge of the most favourable time during the oestrous period at which to practise hand mating (the first 1–2 days) might improve conception rates. In some herds inbreeding results in genetic abnormalities, especially the decline of low-heritable characters, of which fertility is one. Again, animals with reproductive abnormalities such as cryptorchidism, intersexuality and gonadal hypoplasis are not culled as they would be under more sophisticated production systems. There is little knowledge of appropriate breeding ratios, and the herding of males together probably has a negative effect on libido. Sexual desire may also be quelled if rutting males are driven hard at work. In some cases pregnant females are worked up until delivery, and occasionally they may not even be allowed to rest while in labour, leading to an increased risk of abortions and stillbirths, and subsequent reproductive problems. At parturition itself, the unskilled intervention of the herdsman can again lead to calf losses. The newborn are delicate and losses in the first 3 weeks of life may be high, especially when nutritional and disease problems arise. Premature weaning and the early age at which camels are expected to begin work lead to high mortality within the first 4 years of life.
Disease is a major influence on calf losses. Trypanosomiasis, leading to abortions and general debility, is an important contributory factor. Pasteurellosis and salmonellosis are also cited as causes of abortions, while camel pox particularly affects the young once the immunity obtained from colostrum has worn off after the first few months of life. Infections such as pyometra, phimosis and paraphimosis, orchitis and filiarasis directly affect the reproductive tract, as also do abnormalities such as cysts, and all of these may occur with some frequency. There is a high rate of early embryonic mortality, and twins or triplets occur only with the utmost rarity. Endocrine factors, including insufficient gonadotropins to enhance follicular development and subsequent ovulation, may also contribute to infertility. Again, cystic ovarian degeneration is often associated with hormonal disturbances. Finally, ticks, flies and predators, as well as other infectious diseases, such as anthrax, may play a major role in carrying off the young.
To sum up, low fertility is clearly one of the major constraints to camel production. It is a problem that must be overcome if herd offtake is to be increased with a view to marketing good quality camel meat. At present, what little meat reaches the market is often of low quality, since herdsmen are unwilling to trade off young animals.
