Once collected, the semen has to be evaluated and the following parameters should be noted: volume (usually between 2 - 10 ml), color (creamy white), concentration (usual range between 200 - 300 × 10⁶/ml) [9] , and motility. One of the main problems with camel semen is its high viscosity which makes handling and estimation of the spermatozoa parameters difficult. This viscosity is usually attributed to the presence of mucopolysaccharides from secretions of the bulbourethral gland or the prostate, but the degree of viscosity depends on the individual male and on the quantity of the gel fraction in the ejaculate. According to some authors the semen will partially liquefy if stored at 25˚C - 37˚C for 10 - 20 minutes [10] [11] but other studies show it can take up to 8 hours [5] . Enzymatic methods using trypsin, collagenase and chymotrypsin as well as mechanical methods using centrifugation, density gradient centrifugation, vortexing and gentle pipetting have been investigated to try and reduce viscosity, and gentle pipetting was the most successful as it did least damage to the spermatozoa [1] .

Semen preservation and insemination of dromedary camel have been studies by several authors [7] [9] [12] , but majority the studies reported low post-thaw motilities and few, if any, pregnancies with AI of chilled or frozen semen [13] . This could be because of the difficulties involved in collecting semen from male camels and that the ejaculates are of low volume, low sperm concentration and are highly viscous. Several extenders have been used for dilution of freshly collected camel semen [14] such as skimmed milk-glucose extender [15] , Dimitropolous 11, [16] , Laiciphos [17] , Androhep [18] , glucose―EDTA [19] , sodium-citrate-egg yolk [20] , lactose-egg yolk [9] , and Green buffer-egg yolk [3] . Most of these extenders contain an energy source (glucose or fructose), a protein for cold shock protection (lipoprotein from egg yolk or casein from milk), a buffering system and antibiotics. Once collected the semen is diluted with warmed (30˚C - 35˚C) extender added slowly to the semen in a ratio of 1:1 - 3:1 (extender: semen) depending on the concentration of the ejaculate. It is better to let the semen liquefy before insemination to aid better mixing of the semen with the extender and to allow more accurate assessments of concentration and motility.

Sperm motility was better in Laiciphos (60%) and Androhep (68%) compared with Glucose―EDTA (42%) nevertheless no pregnancy results were reported [14] , however pregnancy rates of 50% was achieved with an extender containing 11% lactose and 20% egg yolk [9] . In a subsequent study the best pregnancy rates were achieved with Laciphos + 20% egg yolk (53%), although two subsequently aborted, and Green Buffer + 20% egg yolk (47%) compared with other extenders such as skimmed milk extender [3] . More recently, further studies have compared the extender INRA-96 (I.M.V.) with Green Buffer. Results showed that motility was higher after dilution in Green Buffer (67%) compared with INRA-96 (59%) whereas, pregnancy rates were unaffected by diluent, Green Buffer (34%) and INRA-96 (34%) [21] .

The follicle is responsive to ovulate during its dominant phase; in natural mating, the intravenous injection of 20 mg of Buserelin, or of 3000 IU of human chorionic gonadotropin (hCG) are equally efficacious in inducing ovulation but the crucial factor for ensuring the occurrence of ovulation is the diameter of the dominant [22] . Ovulation rates of 85% are achieved if it measures between 10 and 19 mm in diameter, but ovulation rates dramatically drop to 12.5% if the follicle measures between 20 - 29 mm. Follicles with diameter > 30 mm cannot ovulate as well as follicles during the regression phase [22] .

Although follicles of only 10 mm in diameter acquire the ability to ovulate, the functionality of the developed Corpus luteum (CL) is impaired; consequently it is not advisable to induce ovulation in follicles less than 12 mm [4] [22] . It is suggested to induce ovulation and to perform timed mating or artificial insemination when the dominant follicle measures between 13 and 18 mm [12] . Ovulation occurs 24 - 36 hours after the stimuli [23] ; 31 hours in average, according to [24] . The Corpus Luteum (CL) starts developing 3 - 4 days after the inducing stimulus and reaches its maximum size by days 8 - 9 [23] . In absence of pregnancy the corpus luteum starts regressing 9 - 10 days post-mating [22] [25] . Progesterone concentrations remain low for 3 days then increase to maximum values by day 8 - 9 and decrease to basal concentrations by day 11 - 12 [22] [23] .

The short luteal lifespan entails that the camel conceptus must send an antiluteolytic signal to the endometrium by day 7 or 8 to maintain CL [3] . In case of maternal recognition of pregnancy the CL continues to grow until day 35 [26] . A marked increase of PGF2α have been observed 8 - 10 days post mating in female camels when the maternal recognition of pregnancy did not occur; the PGF2α increase corresponds with the progesterone decline, indicating that luteolysis is mediated by the PGF2α action. Both PGF2α and progesterone concentrations return to basal levels by day 12 after mating. The PGF2α involvement in the luteolysis of dromedary camel was demonstrated by the suppressive effect of meclofenamic acid (a prostaglandin synthetase inhibitor), the latter could be used to prevents luteolysis and synchronize recipients for Embryo transfer procedures [27] .

Pregnancy rates of 50% have been achieved after diluting semen with an extender containing 11% lactose and 20% egg yolk [28] . Similar pregnancy rates were achieved with Laciphos and 20% egg yolk (53% pregnancy rate), and Green Buffer and 20% egg yolk (47% pregnancy rate). Recent studies have proved that it is possible to obtain 72% pregnancy rates by using 1.5 - 3.5 ml of semen (150 × 10⁶ spermatozoa/ml) extended with green buffer and 20% egg yolk but providing that the Green Buffer extender have not been previously frozen, as the freezing process is deleterious for the preservation properties of this extender [30] . Pregnancy rates could be possibly improved through the use of a higher concentration of sperms (300 × 10⁶ spermatozoa/ml). The semen (either fresh or chilled) should be deposited into the uterus at least 24 hours after induction of ovulation [13] .

Pregnancy rates (PR) of 17.6% have been obtained by depositing 150 × 10⁶ motile sperms chilled in the INRA 96 extender. No pregnancies were obtained by using same sperm concentration but diluted with Green Buffer extender. Such results have been improved to 10.5% by using 300 × 10⁶ motile sperms and to 25% with 600 × 10⁶ [21] . Results of semen freezing protocol and pregnancy rates by using frozen semen are not satisfactory in the dromedary camel species. Green/Clear buffers, 20% egg yolk and 6% glycerol is the best combination for freezing dromedary camel semen, but although 50% of spermatozoa were motile after cooling, this percentage was reduced to 35% immediately post-thaw, and to 0% 3 hour post thaws [28] . However, tris-lactose containing a final concentration of 3% glycerol recorded the highest post-thaw motility (45.8%) with the highest survival rate (73.3%) but did not report pregnancy rates using such freezing-thawing protocol [31] .

Fibroscopic evaluation of the camel’s cervix before and after mating has shown that semen is deposited partly intra-uterine and partly intra-cervical [5] . Therefore in AI, semen is generally inseminated directly into the uterus using a bovine insemination catheter passed through the camel’s cervix. Pregnancy rates of 50% have been achieved after insemination of 300 × 10⁶ live spermatozoa [7] or as few as 100 × 10⁶ [9] directly into the uterine body. However, when it is deposited just into the body of the uterus there can be a considerable loss of spermatozoa, due to backflow of semen through the relatively short cervix. A further study was therefore carried out to investigate whether better results could be achieved if the semen was deposited at the tip of the horn, rather than the body of the uterus [12] . The advantage of deep uterine insemination is that the semen is deposited nearer the uterine junction and therefore should reduce the number of spermatozoa needed for successful fertilization [32] .

In the study by [12] a total of 40, 80 or 150 × 10⁶ motile spermatozoa were deposited either just through the cervix into the uterine body or at the tip of the uterine horn ipsilateral with the ovary containing the dominant follicle. The results indicate that although a pregnancy rate of 53% or 43% could be achieved after insemination of 150 × 10⁶ motile spermatozoa into the body of the uterus or at the tip of the horn respectively, a pregnancy rate of 40% could also be achieved when a reduced number of only 80 × 10⁶ spermatozoa were deposited at the tip of the uterine horn [12] . However, as only one camel inseminated with 40 × 10⁶ spermatozoa at the tip of the horn conceived it would suggest that perhaps 80 × 10⁶ is the minimum number of sperm needed to establish a pregnancy by deep intrauterine insemination [12] .