Induction of puberty in West African Dwarf buck-kids with exogenous melatonin

J O Daramola, A A Adeloye, T A Fatoba and A O Soladoye*

Department of Animal Production, University of Ilorin, Nigeria
daramolajames2003@yahoo.com
*Department of Human Physiology, University of Ilorin, Nigeria

Abstract

Sixteen West African Dwarf (WAD) buck-kids age ranging between 2^1/2 and 3months and body weight of 4.82 + 0.87kg were used to evaluate the effect of exogenous melatonin on puberty induction. The buck-kids were treated orally for ten consecutive days with 0, 3, 6, and 9mg melatonin in a completely randomized block design.

Buck-kids administered with melatonin had increase scrotal circumference, testicular measurements, semen volume, mass activity, progressive sperm motility and sperm concentration. The increase in these parameters was highest (P<0.05) at 6mg melatonin administration. Similarly, buck-kids treated with 6mg melatonin had highest (P<0.05) serum testosterone concentration (3.61+0.08mg/ml) compared to 2.35+0.07, 3.16+0.12 and 2.24+018 ng/ml for 0, 3, and 9mg melatonin respectively.

The results of this study showed that melatonin treatment induced the onset of ejaculate in WAD buck-kids at 5months old. Part of the improvement in the testicular measurements and sperm characteristics could be ascribed to increase in the serum testosterone level arising from induced spermatogenesis.

Key words: Buck-kids, melatonin, induction, puberty

Introduction

Puberty is generally defined as the point of sexual development at which the animal becomes capable of reproduction (first ovulation in the female and first spermatozoa in the ejaculate of the male (Bielli et al 2001). The attainment of puberty in buck is primarily influenced by liveweight, breeds, season of birth and exposure to the opposite sex (Ahmad and Noakes 1996). Puberty begins when at least some of the morphological traits (testes size over 6g, appearance of seminiferous tubule, commencement of spermatogenesis are present (Chakraborty et al 1989; Delgadillo and Malpaux 1996; Bielli et al 2001). Age at puberty is highly variable and is dependent on the genetic type of the animals and the management system. However, in different reports, age at sexual maturity is a controversial point in tropical goats. While in African-type goats, mating take place early, sexual maturity being reached soon after the sixth month of age (Webster and Wilson 1989), puberty is ascribed to age 8 to 14 months in local goats in a tropical environment although much higher age at puberty has been described, but they appear to result from poor management conditions (Delgadillo and Malpaux 1996). In contrast, much early age has been described in tropical goats, which reach puberty as early as three months of age (Steele 1996). In all, puberty in male animal is the age at which spermatozoa appear in the seminiferous tubules, epididymis or ejaculate is attained over a wide age range depending on the breed (Bielli et al 2001).

The economic viability of livestock exploration is closely related to animal attaining sexual maturity at a precocious age, which means more offspring could be produced during an animal's life. Attempts have been made to stimulate viable sperm production using inexpensive materials (Trejo et al 2000; Herbert et al 2002). Melatonin, a hormone produced by the pineal gland has been reported to have effect on activity of the testes, semen production, puberty and sexual behaviours (Chemineau et al 1992; Asher et al 1993; Daramola et al 2006). The objective of this study was to determine the efficacy of exogenous melatonin in inducing puberty in WAD buck-kids.
 

Materials and methods

Sixteen West African Dwarf buck-kids, 2¹/₂ to 3 months old and body weight of 4.82 + 0.87kg were housed together and raised under the same management and feeding conditions. The animals were fed with concentrate consisting of Maize (30%), Groundnut cake (10%), Wheat Offals (32%), Palm Kernel Cake (25%), Bone Meal (2%), Salt (0.5%), and Vitamin/mineral Premix (0.5%) and Leucaena lecocephala as basal feed. All animals had access to fresh water ad libitum.

Trial

The animals were randomly divided into 4 treatment groups consisting of 0mg, 3mg, 6mg and 9mg melatonin. Melatonin was administered for ten consecutive days via oral route.

Data collection

The scrotal circumference was measured every week at the widest point of paired testes using the thread (Notter et al 1985) and the thread measured on meter rule.

Blood sampling

Blood samples were collected monthly through jugular vein, centrifuged and serum harvested and stored at -20^oC for testosterone assay. Testosterone was determined by EIA method using Testosterone Enzyme Immune Assay test kit, catalog number 20952 from Diagnostic Automation Int. 23961 Craftsman Road, Suite E/F Calabasas, CA91302.

Semen analysis

Semen was collected from the bucks by electroejaculation thrice at 2 weeks interval. The volume of ejaculate collected was read directly from graduated collection tube. Mass activity and mass motility were determined, and sperm concentration was determined using the improved Naubauer haemocytometer (Bearden and Fuquay 1997). Morphological examination of the sperms was carried out and primary abnormalities of the sperm cells located in the head, midpiece and tail were observed under a microscope.

Histology

The bucks were castrated at the end of the study after collecting semen for 3 consecutive times. The paired testes were removed under anesthesia; the weight, length and circumference of the paired testes were recorded.

Statistical analysis

A two-way analysis of variance was applied, and significant differences among means were tested using Duncan's multiple range test (Duncan 1955) and correlation coefficients were determined in a COSTAT programme.
 

Results

The data obtained on spermiograms in this study are presented in Table 1.

At three and four months old none of the buck-kids examined had spermatozoa in the ejaculate, which microscopically varied from an appearance of clear to yellow aqueous or mildy cloudy. At five months, 0%, 50%, 50% and 50% buck-kids showed motile spermatozoa in the ejaculate for 0mg, 3mg, 6mg and 9mg melatonin respectively, with percentage of motility of 0 %, 56%, 58% and 46% respectively. With increase in age, treated buck-kids showed increase in the number of buck-kids that had spermatozoa in the ejaculate except at the higher dose (9mg) that remained constant. At 6 months of age, 0 %, 100%, 100% and 50% had spermatozoa in the ejaculate in 0mg, 3mg, 6mg and 9mg melatonin treated buck-kids respectively.

There were differences in the scrotal circumference and sperm characteristics of the buck-kids in this study. The scrotal circumference, sperm volume, mass activity, mass motility and sperm concentration and doe that could be bred per single ejaculate were higher (P<0.05) in buck-kids treated with melatonin and the values increased progressively with levels of melatonin and age, declining at higher dose (9mg). The testicular parameters of the melatonin treated buck-kids showed significant differences (P<0.05) and followed the same trend. Following treatment with melatonin, serum testosterone rose sharply from the beginning of the study in buck-kids that received 6mg melatonin compared to with other treatment groups (Figure1).

The results showed a marked variation in the levels of melatonin and the primary abnormality of the buck-kids. The values were higher in buck-kids treated with 9mg melatonin.

The Correlation Coefficients (r) between Spermiogramic parameters of West African Dwarf buck-kids treated with different doses of melatonin are presented in Table 2.

The correlations between scrotal circumference and age, scrotal circumference and sperm volume, scrotal circumference and sperm concentration, as well as scrotal circumference and sperm motility were positive (P<0.05). The same trend was observed between age and scrotal circumference, age and sperm motility, age and sperm volume, age and sperm concentration.

Discussion

The treated buck-kids in the present study displayed a good onset of spermatozoa in the ejaculate at 5 months old than untreated buck-kids similar to British breeds of dairy goats which reached good sperm quality at the age of 172 + 4 days (Ahmad and Noakes 1996). Although the buck-kids treated with melatonin observed in this study showed good sperm quality at earlier age than Nubian bucks in which similar sperm motility was reached at nine months (Chakraborty et al 1989) and African-type goats that reach sexual maturity after the sixth month of age (Webster and Wilson 1989); much early age has been described in tropical goats which reach puberty at three months of age (Steele 1996). The breeds of these goats could account for variations in age of puberty (Bielli et al 2001).

In a male animal, puberty, defined as the age at which spermatozoa appear in the seminiferous tubules, epididymis or ejaculates, is attained over a wide age range depending on the breed (Bielli et al 2001). In the present study, it can be said that puberty was accelerated when traits such as testicular size and commencement of spermatogenesis appeared in a more advanced degree in treated bucks as compared to untreated (control) bucks. The delayed puberty observed in the animals in the untreated (control) compared with treated groups could be explained by a slower growth and low heritability characteristic of this breed in the tropical condition (Delgadillo and Malpaux 1996). Although local goats including WAD goat display interesting reproductive characteristics, most of them could reach puberty at an age of 8 months (Delgaldillo and Malpaux 1996), there exists strong influence of the environment, which does not allow these potentials to be fully expressed. The most likely explanation for the delay in the appearance of spermatozoa is that, though the immature adenohypophysis contains gonadotrophins, these are not released from it in sufficient quantity until puberty to bring about maturation of the gonads (Ahmad and Noakes 1996; Bielli et al 2001). Testicular weight and testicular circumference indicate an acceleration of testicular development at puberty in the melatonin treated animals against the non-treated animals. So the acceleration of testicular development was enhanced by the administration of exogenous melatonin. The observation that the sperm characteristics declined in the treatment group that received higher dose of melatonin suggested that a high dose such as 9mg could produce a suppressive effect on the hypothalamus. A negative feedback could have been established that worked for further decrease in testosterone concentration, which in turn reduced the process of spermatogenesis. This observation agrees with report of Daramola et al (2006) that higher dose such as 9mg reduces testosterone concentration and sexual behaviours in WAD goat.

The observed correlations between age of the bucks and parameters such as scrotal circumference, sperm concentration, sperm motility, sperm volume; and correlations between these parameters are similar to the reports on bovine and other caprice species (Ogwuegbu et al 1985; Akingbemi and Aire 1988; Kwari and Ogwuegbu 1992). These positive correlations suggest high viable spermatozoa per unit of testes and agree with Orji and Steinbach (1976), Knight (1977) and Notter et al (1985) that sperm production correlates highly with the testicular size. There appeared to be interaction between scrotal circumference as well as testicular size in relation to the appearance of spermatozoa in the ejaculate. It seemed that not only was there a certain degree of scrotal circumference and testicular size required before sperm could be produced, but also a limit of chronological age below which puberty was not attained irrespective of the treatment applied. The treated WAD buck-kids in this study attained puberty at the age of 5months. The present findings agreed with available reports, which have examined the relationship of testicular measurements with semen characteristics (Courot 1962; Orji and Steinbach 1976; Knight 1977; Notter et al 1985; Sultama and Edey 1985). Even more encouraging in the present study are the favourable phenotypic correlations of semen and sperm characteristics with testicular measurements. These results support the studies of these workers (Courot 1962; Orji and Steinbach 1976; Knight 1977; Notter et al 1985; Sultama and Edey 1985) who suggested the use of scrotal size and testicular measurements to improve sperm production.

Primary abnormalities consequent on treatment have important consequences on quality of the spermatozoa and fertility. The low incidence of primary abnormalities indicates that treatment with 6mg of melatonin in particular could ensure production of mature spermatozoa; acceptable sperm concentration and primary abnormalities. The increase in sperm output without an increased proportion of abnormal spermatozoa showed that the treatment did not have any adverse effects on the ultra structure of the spermatogenetic cells during the process of spermatogenesis except at higher dose (9mg). Although ejaculates from younger rams have been reported to contain a greater number of abnormal cells consisting in the most part of head which indicate incomplete spermatogenic activity and incomplete epididymal maturation (Colas 1983), the results of this study showed that the administration of melatonin induced sperm production in goat buck-kids without deleterious effects on sperm morphology.
 

Conclusions

• The results of this study showed that melatonin treatment induced the onset of sperm production in WAD buck-kids at 5months old.

•  Part of the improvement in testicular measurements and sperm characteristics could be ascribed to increase in the serum testosterone level arising from induced spermatogenesis.
   

References

Ahmad N and Noakes D E 1996 Sexual maturity in British breeds of goat kids. British Veterinary Journal 152 (1) 93-103

Akingbemi B T and Aire T A 1988 Some measurements of the genitalia and sperm reserves in the Ouda ram (Ovisaries). Verinski Aritiv 59 (4) 2033-2080

Asher G W, Fisher M W, Fennesy P F, Suttie J M and Webster J R 1993 Manipulation of reproductive seasonality of Red Deer (Cervuselaphus) and Fallow deer (Damadama) by strategic administration of exogenous melatonin. Animal Reproduction Science 33 (140) 67-287

Bearden H J and Fuquay J W 1997 Semen Evaluation. Applied Animal Reproduction (4^th Edition). Prentice Hall, Upper Saddle River, New Jersey, 07458.Pg 158-169.

Bielli A, Katz H, Pedrana G, Gastel M T, Morana A, Castrillejo A, Lundeheim N, Forsberg M and Rodriguez-Martinez H 2001 Nutritional management during fetal and postnatal life, and the influence on testicular stereology and sertoli cell numbers in corriedale ram lambs. Small Ruminant Research 40: 63-71

Chakraborty P K, Stuart L D and Brown J L 1989 Puberty in the male Nubian goat: serum concentrations of LH, FSH and testosterone from birth through puberty and semen characteristics at sexual maturity. Animal Reproduction Science 2:91-101

Chemineau P, Malpaux B, Delgadillo J A, Guérin Y, Ravault J P, Thimoniier J and Pelletier J 1992 Control of sheep and goat reproduction: use of light and melatonin. Animal Reproduction Science 30:157-184

Colas G 1983 Factors affecting the quality of ram semen. In: Haresign W (Editor). Sheep Production. Butterworths, London, pp 453-465

Courot M 1962 Action des hormones gonadotropes sur le testicule de l'agneau impubère, réponse particulière de la lignée sertolienne. Annales de Biologie Animale, Biochimie et Biophysique2: 157-162

Daramola J O, Adeloye A A and Soladoye A O 2006 Effect of exogenous melatonin on sexual behaviours in West African Dwarf goat. Livestock Research for Rural Development. Volume18. http://www.cipav.org.co/lrrd/lrrd18/9/dara18133.htm

Delgadillo J A and Malpaux B 1996 Reproduction of goats in the Tropics and sub-tropics. Proceedings of the VI International Conference on Goat. Volume 2. 6-11, May 1996, Beijing, China

Duncan D B 1955 Multiple Ranges and Muliple F-tests. Biometrics, 11: 1-42

Herbert U, Ezeobi A N and Iloeje M U 2002 Induction of spermatogenesis in rabbits using the fertility drugs Clomiphere citrate (CLOMID^R). Proceedings of the 27^th Annual Conference, Nigerian Society for Animal Production (ASAP), March17-21, 2002. Federal University of Technology, Akure, Nigeria. Pp. 25-27

Knight T W 1977 Methods of the indirect estimate of testes weight and sperm numbers in Marino and Romney rams. New Zealand Journal of Agricultural Research 20: 291-296

Kwari H D and Ogwuegbu S O 1992 Morphometric studies of the reproductive organs, gonadal and extragonadal sperm reserves of the Kuri bull and white Borno buck of the Sahelian zone of North-eastern part of Nigeria. Tropical Veterinary, 10:83-87.

Notter D R, Lucas J R, Mcclaughertly F S and Copenhaver J S 1985 Breed group differences in testicular growth patterns in spring-born lambs. Journal of Animal Science 60: 622-631

Ogwuegbu S O, Oke B O, Akusu M O and Aire T A 1985 Gonadal and extragonadal sperm reserves of the Maradi (Red Sokoto) goat. Bulletin of Animal Health and Production in Africa 33: 141.

Orji  B I and Steinbach J 1976 Postnatal development of testis and epididymis in the Nigerian Dwarf sheep. Proceedings of the 8^th International congress on Animal Production and Artificial Insemination Volume 3, Krakow. pp. 73-76

Steele M 1996 Goat. The Tropical Agriculturalist series. CTA publication, Macmillan Education Ltd, London. 40-43

Sultama I K and Edey T N 1985 Reproductive development during winter and spring of merino ram lambs growth at three different rates. Australian Journal Agriculture Research 36: 461-467.

Trejo G A, Ponce L C and Vidal G M A 2000 Effects of melatonin and GnRH treatments on semen quality in young male goats. 7^th International Conference on goats. France 15-21 May 2000. pp. 444 - 445

Webster C C and Wilson P N 1989 Agriculture in the tropics 2^nd edition. Tropical Agriculture Series, Longman Scientific and Technical, England.190-195

Received 3 December 2006; Accepted 10 July 2007; Published 5 September 2007

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