Testicular steroidogenesis in the camel (Camelus dromedarius) during the mating and the nonmating seasons

Dromedary camel: A model of heat resistant livestock animal

Camels are highly adapted to harsh environments. The dromedary camel is adapted to a wide range of arid and semi-arid conditions. The aim of the present paper is to review some of the key adaptation characteristics of the dromedary and how they affect reproductive patterns. Special attention is given to the reproductive seasonality and interaction between lactation and reproduction. Adaptive mechanisms are described including some of the recent molecular aspects with respect to heat shock protein expression in camels.

Effect of short artificial lighting and low temperature in housing rooms during non-rutting season on reproductive parameters of male dromedary camels

Ten dromedary mature males were used to study the effects of short artificial lighting and low temperature on the reproductive behavior, testicular size, semen quality and hormone during the non-rutting season and subsequent rutting season. Bulls were allocated into two groups: the first group were subjected to natural daylight and temperature and used as a control. The second group was housed individually in light and temperature controlled rooms in which artificial light (300 lux) was used for 10 h/d, and the temperature was 25.28 ± 0.21 °C. The trial was initiated in mid-June and continued for 10 weeks in the non-rutting season. The reproductive parameters of all animals in the control and room groups were evaluated once every two weeks. The reproductive parameters of all animals in the control and room groups were re-evaluated during the rutting season of the same year. A significant (P < 0.05) increase in the morphometry of the testes, scrotum, libido, and reaction time score, as well as serum melatonin and testosterone levels, was observed in the treatment non-rutting season (TNRS) group compared to in the control non-rutting season (CNRS) group. The testicular volume, reaction time score, serum melatonin, and testosterone were significantly (P < 0.05) higher in the treatment rutting season (TRS) group than in the control non-rutting season (CRS) group. Improvement in the semen parameters were observed in the TNRS and TRS groups compared to in the CRS group. In conclusion, these results demonstrate that short artificial lighting and low temperature can induce rutting out of season and improve the reproductive parameters of dromedary males during the subsequent rutting season.

Evaluation of sexual behavior of housed male camels (Camelus dromedarius) through female parades: correlation with climatic parameters

Camels are seasonal breeders, and their sexual behavior is influenced by environmental conditions, but the relationship between climatic factors and sexual behavior has been poorly described in the available literature. Nowadays, the male camel living habit is shifting towards captivity; thus, this study was carried out to evaluate the sexual behavior of housed male dromedary camel through female's parades and to correlate it with climatic parameters. Four housed sires, reared for semen collection, and one dam were used and the trial lasted 8 weeks, considering the first week as control. Six days per week and during evenings, the female was brought near each males' boxes, while two observers filled a behavioral sampling ethogram and scored the male sexual behavior. After this parade, blood samples were taken from the female to evaluate the estradiol concentration. In addition, the following meteorological parameters were recorded, everyday, at 9:00 a.m. and 19:00 p.m.: pressure, wind, temperature, humidity, and H-index. The correlation between sexual behavioral score and female estradiol concentration and climate parameters was analyzed. All the behavioral parameters showed a significant upward trend; female estradiol concentration varied during the period and picked at week 5. Male sexual behavior was negatively correlated with morning H-index, wind, and temperature, and positively correlated with pressure and evening humidity, whereas it was not correlated with estrogen. In conclusion, female parade was a successful method to evaluate and stimulate the occurrence of housed male dromedary camel sexual activity that resulted to be negatively affected by hot temperature, warm wind, and lack of rain.

Effect of age, pubertal stage and season on testosterone concentration in male dromedary camel

The present study was conducted in the Laboratory of Animal Physiology and Biotechnology, Department of Animal Production, Faculty of Agriculture, Mansoura University, Egypt. The present investigation aimed at studying effects of ages, pubertal stages and seasons of the year on testosterone concentrations in blood plasma and tissue homogenate of the testes. The testes used in the current study were collected from a total of 104 one-humped male camels (Camelus dromedarius). Samples were taken from pre (1-3.5 years) and post (3.5-13 years) pubertal camels. Testes were studied for a two consecutive seasons. The freshly prepared homogenate of the testicular tissue and blood plasma were used for determining the concentrations of testosterone in plasma and testicular extract. The concentrations of testosterone in blood plasma and testicular tissue were significantly increased during the breeding season compared with that of non-breeding season; the concentration of testosterone was higher in testicular tissue than in blood plasma. Testosterone concentrations in plasma and testicular tissue were increased in breeding than in non-breeding season. In addition, the testosterone concentrations were closely related with seasonal changes, stage of puberty and advancing age.

Testosterone profiles and their correlation with sexual libido in male camels

The study was conducted on 4 male Jaisalmeri camels (Camelus dromedarius) on their circulating testosterone (T) profiles and correlation with sexual libido. The average T concentration was low during hot months of April to September, started increasing in the months of October and November, continued to increase steadily in the months of December, January and February followed by decline in the ensuing months. Individual variations in onset and cessation of T surge were observed. Sexual libido as indicated by copulation time (CT) and volume of semen ejaculated (V) was high during January to April months, declined slowly over May month followed by complete cessation in later half of June. Sexual libido was almost negligible during July to November months. The sexual libido was also low during December month. Like circulating T profiles, individual variations were also observed in sexual libido. Data indicated that onset as well as cessation of T surge preceded the onset and cessation of sexual libido in all the animals. A positive correlation was found among circulating T (concentration), CT and V of semen. It is concluded that seasonal changes in circulating testosterone governs sexual libido in male camels.

Effect of season and gonadotropins on the superovulatory response in camel (Camelus dromedarius)

The purpose of the present investigation was to study the extent to which season and the gonadotropin preparation interferes with the superovulatory response in the dromedary. Adult camels were treated for superovulation during the breeding (November to April) and non-breeding season (May to October). Animals were synchronized by daily i.m. injections of progesterone (125 mg/animal/day, Jurox, UK) for 10 to 14 days. Superovulation was induced by 400mg pFSH alone (Follitropin V, Vetrepharm, Canada) administered in eight descending doses at 12h intervals or a combination of PMSG (2000IU, Folligon, Intervet, The Netherlands), injected with last injection of progesterone and 400mg pFSH in eight descending doses. The follicular development was daily assessed by ultrasonography of the ovaries. The donors were classified as per their response to the superovulatory treatment into very good (>10 follicles), good (5-10 follicle), poor (2-4 follicles) or no response (1 or no follicle) on each ovary. Ovulation was induced by injecting 3000 IU hCG (Chorulon, Intervet) at the time of first mating. The donors were mated twice at an interval of 12h when all or most of the follicles reached to a size of about 1.0-1.7 cm. Camels were flushed non-surgically on Day 6 or 7 after the ovulation. The proportion of camels showing very good response during the breeding as well as non-breeding season was higher (P<0.05) when a combination of pFSH and eCG was used compared with pFSH only. There was no difference (P>0.05) in the proportion of donors flushed successfully (embryos recovered) when treated either with a combination of pFSH and eCG or pFSH alone during the breeding and non-breeding season. The rate of recovery of ova/embryos and proportion of transferable embryos was higher (P<0.05) when donors were treated with pFSH+eCG compared with pFSH only during the breeding as well as non-breeding season. The results may indicate that ova/embryo recovery rate of the dromedary is influenced by the gonadotropin preparation but is not appreciably affected by the season.

Infertility in the dromedary bull: a review of causes, relations and implications

Research into infertility in the dromedary bull, as reported during the last two decades, is reviewed with emphasis on causes and effects. Reproductive activity of such animals is naturally limited by a breeding season, though with enough encouragement some may mate with oestrous females out of season but a full fertilization potential can in no way be expected. It is essential that any female presented to a bull is capable of reproducing. The presentation of a subfertile or infertile female due to infection or physiological abnormality will adversely affect the female's ability to conceive and, therefore, the apparent fertility rates of the bull she was put to. The average number of successful services a bull could be expected to perform is two per day. Dromedary bulls with large testes have larger sperm outputs and can cope with more than two females per day providing that they are given adequate periods of rest, 1-2 days every 10 days or so, in conjunction with appropriate nutrition throughout the season. Anabolic steroids or testosterone therapies, which are sometimes used in an attempt to improve male characteristics and bull libido, are not recommended for dromedary bulls in breeding work. Such steroids result in a decrease in testicular size and weight with fewer sperm per gram of testicular tissue being found and the sperm produced also have lower motility rates. Pain associated with the act of mating a she-camel, due to injuries or inflammation in the scrotum, testes, prepuce and sheath, can cause a permanent reduction in bull libido. Camel bulls achieving pregnancy rates more than 60% have had consistently higher spermatozoal concentrations and kinematic variables derived by the computerized cell motion analyzer (CMA) system. As far as physical capabilities are concerned, 3-year-old dromedary bulls, which have reached puberty, have been shown to be perfectly capable of fertilizing a female, but they have a limited sperm production to perform consistently throughout the season in a large herd. By 4.5-5.0 years of age, they are capable of producing adequate numbers of sperm to mate as many as females as an adult bull but fertilizing capacity is not attained until 6 years of age on average. Hyperoestrogenaemia, associated with autoimmune thyroiditis and trypanosomiasis, suppresses the secretion of testicular testosterone and augments the release of testicular histamine, which appears mandatory for quantitative reduction/loss of advanced spermatogenic cells in infertile dromedary bulls.

Sex and season influence gonadal steroid biosynthetic pathways, end-product production and steroid conjugation in blotched blue-tongued lizards (Tiliqua nigrolutea)

We examined differences in gonadal steroid production and biosynthetic pathway activity with changing reproductive condition and between sexes in the scincid lizard, Tiliqua nigrolutea. We observed clear seasonal and sexual variation in the production of androgens and steroid conjugates, but detected no 17beta-estradiol or 5alpha-dihydrotestosterone produced by the gonads. An alternative steroid, more polar than estradiol, was detected: an investigation of this steroid is reported separately [Gen. Comp. Endocrinol. 129 (2002) 114]. There were seasonal and sex-related differences in steroid biosynthetic pathway activity. The Delta5 pathway metabolite, dehydroepiandrosterone, was detected only in males, and only from incubations using regressed testicular tissue. There was also a seasonal difference between the sexes in rates of progesterone accumulation, although the absence of corresponding elevated plasma concentrations suggests that the role of progesterone switches from a directly acting hormone to a precursor for others during the reproductive cycle in females. These results suggest that within the traditional view that vertebrate biosynthetic pathway activity and end-products are phylogenetically conserved, there is likely to be considerably species- and/or genus-specific variation.

On the intrinsic innervation of the epididymis of the camel (Camelus dromedarius)

The innervation of the camel epididymis was studied in 26 apparently healthy, sexually mature animals aged between 4 and 12 years. The material was collected during the different seasons of the year. Generally, five samples were taken from each epididymis. To demonstrate the general innervation pattern, immunohistochemical reactions to protein gene product-9.5, neurofilaments and neuron-specific enolase were used, in addition to acetylcholinesterase histochemistry. The nerve supply of the epididymis comes from two sources: (1) The majority of fibers come from the N. spermaticus inferior and accompany the deferent duct. (2) Another contribution stems from the N. spermaticus superior and enters the head region of the epididymis. From the exterior, the nerves penetrate the capsule of the organ to reach the interductular connective tissue. The terminal ramifications are observed directly within the wall of the duct and the wall of the epididymal arteries. The veins of the camel epididymis are not innervated. In the wall of the ductus epididymidis, the nerve fibers form plexuses at the subepithelial level and in the muscular coat. The amount of nerve fibers increases from the head to the tail, paralleling an increase in the intrinsic musculature. The intramural and interductular innervation of epididymal body and tail shows clear seasonal variations: More fibers and stronger reactions are observed during the winter season; the lowest density and the weakest reactions occur during the summer season. All epididymal nerves of the camel are unmyelinated. The majority of the intramural fibers and all in the arterial wall represent postjunctional sympathetic axons, but in the intramural plexuses of the duct a considerable number of cholinergic fibers are also present. Neuropeptide Y is the most frequent peptidergic transmitter and generally co-localized with dopamine-beta-hydroxylase in the sympathetic axons. Vasoactive intestinal polypeptide has a distribution similar to that of the cholinergic fibers. Calcitonin gene-related peptide-positive axons occur in moderate numbers, but never in the arterial innervation. Together with the relatively rare substance P-containing fibers, the calcitonin gene-related peptide-positive axons seem to represent the only sensory nerves in the camel epididymis.

Immunohistochemical investigations of the autonomous nerve distribution in the testis of the camel (Camelus dromedarius)

The distribution of autonomous nerves in the testis of the camel was studied by immunohistochemical methods. A total of 26 testes was collected during the different seasons of the year. As pan-neuronal markers, antibodies to protein gene product 9.5 and to neurofilaments are superior to antibodies against neuron-specific enolase and acetylcholinesterase histochemistry for the description of the nerves in the camel testis. Testicular nerves reach the camel testis by three access-routes as (1) funicular contribution, (2) mesorchial contribution and (3) as caudal contribution. The main target for testicular nerves is the arterial vascular tree of the organ, whereas all veins of testis and pampiniform plexus are devoid of any innervation in the camel. In the wall of the arteries, the nerves form a plexus at the media-adventitia border. The density of the arterial plexuses increases along the vascular tree: smaller septal and mediastinal arteries are better innervated than albugineal arteries and the latter better than the A. testicularis. The nerves in the septula testis, in the mediastinum and between the Leydig cells show clear seasonal changes, being particularly abundant in autumn and particularly scarce in spring. The nerves that reach the camel testis are unmyelinated and represent in the vast majority postjunctional sympathetic neurons. Cholinergic fibers are absent in the camel testis. Neuropeptide Y is the dominating peptidergic transmitter in the testicular nerves and colocalized with noradrenaline in the same axons. Vasoactive intestinal polypeptide-containing fibers reach the camel testis exclusively as parts of the caudal nervous contribution via the ligamentous bridge between testis and epididymal tail and are restricted to the caudal pole of the testis. Calcitonin gene-related peptide-positive axons are not frequent in the camel testis; nevertheless, they seem to be the most important sensory pathway of this organ.

Intratesticular morphometric, cellular and endocrine changes around the pubertal period in dromedary camels

We obtained the paired testes from 66 clinically healthy camels during two consecutive breeding seasons. Testicular tissues were examined for peripubertal changes in histological structure as well as spermatogenic and steroidogenic activities. Cellular sizes (length microm x width microm) increased linearly (P< 0.05) throughout the first three years of the animal's life for Leydig cells and between two and a half and five years of age for Sertoli cells. A clear increase in the percentage of tubules demonstrating primary and secondary spermatocytes occurred between less than one and five years and a cohort of elongated spermatids was produced in 3.5 +/- 0.2% tubules in males of two and a half years old; the appearance of spermatozoa in 3.1 +/- 0.3% tubules was evident six months later. The basal values for intratesticular and plasma concentrations of oestradiol-17 beta and testosterone respectively, were measured in all animals up to one and a half years for oestradiol-17 beta and three years for testosterone. Thereafter, both steroids increased markedly (P< 0.01) peaking to 269.5 +/-27.1 pg/g and 83.4 +/- 8.3 pg/mL at three years for oestradiol-17 beta and to 164.7 +/- 16.8 ng/g and 6.8 +/- 0.7 ng/mL at five years for testosterone. The results suggested that a steroid hormonal shift around four and a half to five years of age could demarcate the beginning of pubertal period which culminates with the production of the first ejaculum containing higher concentrations of spermatozoa by dromedary camels of six years old.

The in vitro biosynthesis of epitestosterone and testosterone from C19 steroid precursors in the testis of the lizard Tiliqua rugosa

The metabolism of androgens in the testis of the lizard Tiliqua rugosa has been studied in vitro by incubating cellular homogenates with radiolabeled C19-steroid substrates. The identification 17 beta-oxidoreductase and 3 beta-hydroxysteroid dehydrogenase/isomerase activities. Aromatase, 5 alpha-reductase, and 17 alpha/beta-epimerase activities were not detected. The 17 alpha-oxidoreductase activity was temperature dependent (maximal at 32 degrees), while the 17 beta-oxidoreductase activity was temperature independent. Time yield and dual-label studies indicated that testosterone biosynthesis mainly involves the 4-ene pathway (via androstenedione), whereas the formation of epitestosterone uses both the 4-ene and 5-ene (via 5-androstene-3 beta, 17 alpha-diol) pathways. The function of alternative pathways in androgen biosynthesis is discussed, as is the role of temperature in the intratesticular regulation of androgen production.

Estradiol concentration in the serum of the one-humped camel (Camelus dromedarius) during the various reproductive stages

During the estrous cycle of the camel the concentration of estradiol (E2) varies between 9 and 110 pg/ml. In early estrus, the peak level of E2 (74.7 +/- 6.61 pg/ml, n = 11) is maintained for 2.9 +/- 1.83 days. The length of an estrous cycle is 17.2 days. In the 10th month of pregnancy the level of E2 rises abruptly to 338.3 +/- 162.42 pg/ml and continues to rise until the 12th month, peaking at 606 +/- 120.27 pg/ml. The hormone concentration then drops until the day of parturition (mean 113.4 +/- 26.51 pg/ml). The level of E2 during the nonbreeding season (May-November) is low (6-48 pg/ml).

Leydig cell differentiation during the reproductive cycle of the seasonal breeder Camelus dromedarius: an ultrastructural analysis

Spermatogenesis and Leydig cell development in the dromedary were analyzed at the ultrastructural level and correlated with fluctuations of testosterone synthesis during the mating and nonmating seasons. It was found that (1) spermatogenesis and diameter of the seminiferous tubules are dissociated from seasonal fluctuations of testosterone synthesis as they remain similar throughout the year; (2) the volume of the interstitial tissue and the rate of testosterone synthesis are correlated since both increase during the mating season and both diminish during the nonmating season; (3) during the mating season, reduction of the tubular smooth endoplasmic reticulum (SER) and proliferation of condensed SER correspond to the relatively high rate of testosterone synthesis by the 4-ene pathway; (4) during the mating season there is a drastic reduction of the SER and proliferation of myelin figures within the Leydig cells which disrupt at the end of their differentiation. During the nonmating season, testosterone synthesis is probably impaired only at the final stage of differentiation of the Leydig cell.