**Author details**

Tetsuya Kohsaka1 \*, Siqin2 , Itaru Minagawa1 and Hiroshi Sasada3

\*Address all correspondence to: kohsaka.tetsuya@shizuoka.ac.jp

1 Department of Applied Life Sciences, Animal Reproduction and Physiology, Faculty of Agriculture, Shizuoka University, Shizuoka, Japan


## **References**


[4] Ivell R, Kotula‐Balak M, Glynn D, Heng K, Anand‐Ivell R. Relaxin family peptides in the male reproductive system – A critical appraisal. Molecular Human Reproduction. 2011;**17**:71‐84. DOI: 10.1093/molehr/gaq086

retaining the C‐domain with full biological activity. The reason why the INSL3 exists as a B–C–A form is unclear, but the C‐domain does not appear to interfere with receptor binding and activation. Additionally, clarification of native goat INSL3 will facilitate development of a specific immunoassay system for monitoring INSL3 in blood and body fluids. In contrast, from a functional point of view, we provided the evidence for a functional receptor that binds INSL3 in testicular germ cells and in spermatozoa, implying that the intra‐ and extratesticular INSL3 hormone‐receptor system operate in male goats. We also found the potential of this system as a novel parameter for predicting fertility in breeding sires. However, it remains unknown what functions INSL3 actually exerts on testicular germ cells and on spermatozoa in this species. Finally, the findings outlined here will help in the discovery of new target tissues/organs and receptor‐expressing cells, not only in male goats but also in female goats,

This work was supported by a Grant‐in‐Aid for Scientific Research from the Japan Society for the Promotion of Science (grant number 15 K07691 to T. Kohsaka) and by a Special Research

1 Department of Applied Life Sciences, Animal Reproduction and Physiology, Faculty of

3 Animal Reproduction, Kitasato University School of Veterinary Medicine, Towada, Japan

[1] Ivell R, Bathgate RA. Reproductive biology of the relaxin‐like factor (INSL3). Biology of

[2] Ivell R, Heng K, Anand‐Ivell R. Insulin‐like factor 3 and the HPG axis in the male.

[3] Deveson S, Forsyth IA, Arendt J. Retardation of pubertal development by prenatal long days in goat kids born in autumn. Journal of Reproduction and Development.

Reproduction. 2002;**67**:699‐705. DOI: 10.1095/biolreprod.102.005199

Frontiers in Endocrinology. 2014;**5**:6. DOI: 10.3389/fendo.2014.00006

and Hiroshi Sasada3

thereby giving insight into the potential role of INSL3 in those organs.

Fund from Kitasato University School of Veterinary Medicine (to H. Sasada).

, Itaru Minagawa1

2 Inner Mongolia International Mongolian Hospital, Hohhot, China

\*Address all correspondence to: kohsaka.tetsuya@shizuoka.ac.jp

**Acknowledgements**

124 Goat Science

**Author details**

Tetsuya Kohsaka1

**References**

\*, Siqin2

Agriculture, Shizuoka University, Shizuoka, Japan

1992;**95**:629‐637. DOI: 10.1530/jrf.0.0950629


[15] Minagawa I, Sagata D, Pitia AM, Kohriki H, Shibata M, Sasada H, Hasegawa Y, Kohsaka T. Dynamics of insulin‐like factor 3 and its receptor expression in boar testes. Journal of Endocrinology. 2014;**220**:247‐261. DOI: 10.1530/JOE‐13‐0430

[27] Halban PA, Irminger JC. Sorting and processing of secretory proteins. Biochemical

Recent Advances in Research on the Hormone INSL3 in Male Goats

http://dx.doi.org/10.5772/intechopen.70079

127

[28] Kelly RB. Pathways of protein secretion in eukaryotes. Science. 1985;**230**:25‐32. DOI:

[29] Nakayama K. Furin: A mammalian subtilisin/Kex2p‐like endoprotease involved in pro‐ cessing of a wide variety of precursor proteins. Biochemical Journal. 1997;**327**:625‐635.

[30] Kohsaka T, Sasada H, Masaki J. Subcellular localization of the antigenic sites of relaxin in the luteal cells of the pregnant rat using an improved immunocyto‐ chemical technique. Animal Reproduction Science. 1992;**29**:123‐132. http://dx.doi.

[31] Kohsaka T, Sasada H, Masaki J. Subcellular localization of the maturation process of relaxin in rat luteal cells during pregnancy as revealed by immunogold labeling. Animal Reproduction Science. 1993;**34**:159‐166. http://dx.doi.org/10.1016/0378‐4320(93)90074‐2

[32] Kohsaka T, Takahara H, Sasada H, Kawarasaki T, Bamba K, Masaki J, Tagami S. Evidence for immunoreactive relaxin in boar seminal vesicles using combined light and electron microscope immunocytochemistry. Journal of Reproduction and Fertility.

[33] Marriott D, Gillece‐Castro B, Gorman CM. Prohormone convertase‐1 will process prorelaxin, a member of the insulin family of hormones. Molecular Endocrinology.

[34] Siqin, Nakai M, Hagi T, Kato S, Pitia AM, Kotani M, Odanaka Y, Sugawara Y, Hamano K, Yogo K, Nagura Y, Fujita M, Sasada H, Sato E, Kohsaka T. Partial cDNA sequence of a relaxin‐like factor (RLF) receptor, LGR8 and possible existence of the RLF ligand‐receptor system in goat testes. Animal Science Journal. 2010;**81**:681‐686. DOI:

[35] Kohsaka T, Sagata D, Minagawa I, Kohriki H, Pitia AM, Sugii Y, Morimoto M, Uera N, Shibata M, Sasada H, Hasegawa Y. Expression and localization of RLF/INSL3 recep‐ tor RXFP2 in boar testes. Italian Journal of Anatomy and Embryology. 2013;**118**(1

[36] Pitia AM, Uchiyama K, Sano H, Kinukawa M, Minato Y, Sasada H, Kohsaka T. Functional insulin‐like factor 3 (INSL3) hormone‐receptor system in the testes and spermatozoa of domestic ruminants and its potential as a predictor of sire fertility. Animal Science

[37] Anand‐Ivell R, Relan V, Balvers M, Coiffec‐Dorval I, Fritsch M, Bathgate RA, Ivell R. Expression of the insulin‐like peptide 3 (INSL3) hormone‐receptor (LGR8) system in the testis. Biology of Reproduction. 2006;**74**:945‐953. DOI: 10.1095/biolreprod.105.048165

[38] Ferguson SS. Evolving concepts in G protein‐coupled receptor endocytosis: The role in receptor desensitization and signaling. Pharmacological Reviews. 2001;**53**:1‐24

Journal. 1994;**299**:1‐18. DOI: 10.1042/bj2990001

10.1126/science.2994224

DOI: 10.1042/bj3270625

org/10.1016/0378‐4320(92)90026‐A

1992;**95**:397‐408. DOI: 10.1530/jrf.0.0950397

10.1111/j.1740‐0929.2010.00801.x

1992;**6**:1441‐1450. DOI: 10.1210/mend.6.9.1435788

Suppl):23‐25. DOI: http://dx.doi.org/10.13128/IJAE‐13884

Journal. 2017;**88**:678‐690. DOI: 10.1111/asj.12694


[27] Halban PA, Irminger JC. Sorting and processing of secretory proteins. Biochemical Journal. 1994;**299**:1‐18. DOI: 10.1042/bj2990001

[15] Minagawa I, Sagata D, Pitia AM, Kohriki H, Shibata M, Sasada H, Hasegawa Y, Kohsaka T. Dynamics of insulin‐like factor 3 and its receptor expression in boar testes. Journal of

[16] Pitia AM, Minagawa I, Uera N, Hamano K, Sugawara Y, Nagura Y, Hasegawa Y, Oyamada T, Sasada H, Kohsaka T. Expression of insulin‐like factor 3 hormone‐receptor system in the reproductive organs of male goats. Cell and Tissue Research. 2015;**362**:407‐420. DOI:

[17] Kerr JB, Knell CM. The fate of fetal Leydig cells during the development of the fetal and

[18] McKinnell C, Sharpe RM, Mahood K, Hallmark N, Scott H, Ivell R, Staub C, Jégou B, Haag F, Koch‐Nolte F, Hartung S. Expression of insulin‐like factor 3 protein in the rat testis during fetal and postnatal development and in relation to cryptochidism induced by in utero exposure to di (n‐butyl) phthalate. Endocrinology. 2005;**146**:4536‐4544. DOI:

[19] Foresta C, Bettella A, Vinanzi C, Dabrilli P, Meriggiola MC, Garolla A, Ferlin A. Insulin‐ like factor 3: A novel circulating hormone of testis origin in humans. Journal of Clinical

[20] Sadeghian H, Anand‐Ivell R, Balvers M, Relan V, Ivell R. Constitutive regulation of the Insl3 gene in rat Leydig cells. Molecular and Cellular Endocrinology. 2005;**241**:10‐20.

[21] Büllesbach EE, Schwabe C. A novel Leydig cell cDNA‐derived protein is a relaxin‐like factor. Journal of Biological Chemistry. 1995;**270**:16011‐16015. DOI: 10.1074/jbc.270.27.

[22] Smith KJ, Wade JD, Claasz AA, Otvos Jr L, Temelcos C, Kubota Y, Hutson JM, Tregear GW, Bathgate RA. Chemical synthesis and biological activity of rat INSL3. Journal of

[23] Büllesbach EE, Schwabe C. The primary structure and the disulfide links of the bovine relaxin‐like factor (RLF). Biochemistry. 2002;**41**:274‐281. DOI: 10.1021/bi0117302

[24] Minagawa I, Fukuda M, Ishige H, Kohriki H, Shibata M, Park EY, Kawarasaki T, Kohsaka T. Relaxin‐like factor (RLF)/insulin‐like peptide 3 (INSL3) is secreted from testicular Leydig cells as a monomeric protein comprising three domains B–C–A with full biologi‐ cal activity in boars. Biochemical Journal. 2012;**441**:265‐273. DOI: 10.1042/BJ20111107 [25] Siqin, Minagawa I, Okuno M, Yamada K, Sugawara Y, Nagura Y, Hamano K, Park EY, Sasada H, Kohsaka T. The active form of goat insulin‐like peptide 3 (INSL3) is a single‐ chain structure comprising three domains B–C–A, constitutively expressed and secreted by testicular Leydig cells. Biological Chemistry. 2013;**394**:1181‐1194. DOI: 10.1515/

[26] LeRoith D, Roberts CT. The insulin‐like growth factor system and cancer. Cancer Letters.

Endocrinology and Metabolism. 2004;**89**:5952‐5958. DOI: 10.1210/jc.2004‐0575

Endocrinology. 2014;**220**:247‐261. DOI: 10.1530/JOE‐13‐0430

postnatal rat testis. Development. 1988;**103**:535‐544

Peptide Science. 2001;**7**:495‐501. DOI: 10.1002/psc.344

2003;**195**:127‐137. DOI.org/10.1016/S0304‐3835(03)00159‐9

10.1007/s00441‐015‐2206‐8

126 Goat Science

10.1210/en.2005‐0676

16011

hsz‐2012‐0357

DOI: 10.1016/j.mce.2005.03.017


[39] Muda M, He C, Martini PG, Ferraro T, Layfield S, Taylor D, Chevrier C, Schweickhardt R, Kelton C, Ryan PL, Bathgate RA. Splice variants of the relaxin and INSL3 recep‐ tors reveal unanticipated molecular complexity. Molecular Human Reproduction. 2005;**11**:591‐600. DOI: 10.1093/molehr/gah205

[49] Kaftanovskaya EM, Feng S, Huang Z, Tan Y, Barbara AM, Kaur S, Truong A, Gorlov IP, Agoulnik AI. Suppression of insulin‐like 3 receptor reveals the role of *β*‐catenin and Notch signaling in gubernaculum development. Molecular Endocrinology. 2011;**25**:170‐183.

Recent Advances in Research on the Hormone INSL3 in Male Goats

http://dx.doi.org/10.5772/intechopen.70079

129

[50] Amory JK, Page ST, Anawalt BD, Coviello AD, Matsumoto AM, Bremner WJ. Elevated end‐of‐treatment serum INSL3 is associated with failure to completely suppress sper‐ matogenesis in men receiving male hormonal contraception. Journal of Andrology.

[51] Bay K, Hartung S, Ivell R, Schumacher M, Jürgensen D, Jorgensen N, Holm M, Skakkebaek NE, Andersson AM. Insulin‐like factor 3 serum levels in 135 normal men and 85 men with testicular disorders: Relationship to the luteinizing hormone‐testos‐ terone axis. Journal of Clinical Endocrinology and Metabolism. 2005;**90**:3410‐3418. DOI:

[52] Kumar P, Kumar D, Singh I, Yadav PS. Seminal plasma proteome: promising biomark‐ ers for bull fertility. Agricultural Resource. 2012;**1**:78‐86. DOI: 10.1007/s40003‐011‐0006‐2

[53] Moura AA, Erickson BH. Age‐related changes in peripheral hormone concentrations and their relationships with testis size and number of Sertoli and germ cells in yearling beef bulls. Journal of Reproduction and Fertility. 1997;**111**:183‐190. DOI: 10.1530/jrf.0.1110183

[54] Sasaki Y, Kohsaka T, Kawarasaki T, Sasada H, Ogine T, Bamba K, Takahara H. Immunoreactive relaxin in seminal plasma of fertile boars and its correlation with sperm motility characteristics determined by computer‐assisted digital image analysis. International Journal of Andrology. 2001;**24**:24‐30. DOI: 10.1046/j.1365‐2605.2001.00259.x

[55] Kohsaka T, Hamano K, Sasada H, Watanabe S, Ogine T, Suzuki E, Nishida S, Takahara H, Sato E. Seminal immunoreactive relaxin in domestic animals and its relationship to sperm motility as a possible index for predicting the fertilizing ability of sires. International

[56] Dias JC, Emerick LL, José de Andrade V, Martins JA, Filho VR. Serum testosterone concentrations in Guzerat young bulls and their correlations with reproductive traits.

Journal of Andrology. 2003;**26**:115‐120. DOI: 10.1046/j.1365‐2605.2003.00409.x

Archives of Veterinary Science. 2014;**19**:24‐31. (In Portuguese)

DOI: 10.1210/me.2010‐0330

10.1210/jc.2004‐2257

2007;**28**:548‐554. DOI: 10.2164/jandrol.106.002345


[49] Kaftanovskaya EM, Feng S, Huang Z, Tan Y, Barbara AM, Kaur S, Truong A, Gorlov IP, Agoulnik AI. Suppression of insulin‐like 3 receptor reveals the role of *β*‐catenin and Notch signaling in gubernaculum development. Molecular Endocrinology. 2011;**25**:170‐183. DOI: 10.1210/me.2010‐0330

[39] Muda M, He C, Martini PG, Ferraro T, Layfield S, Taylor D, Chevrier C, Schweickhardt R, Kelton C, Ryan PL, Bathgate RA. Splice variants of the relaxin and INSL3 recep‐ tors reveal unanticipated molecular complexity. Molecular Human Reproduction.

[40] Scott DJ, Layfield S, Yan Y, Sudo S, Hsueh AJ, Tregear GW, Bathgate RA. Characterization of novel splice variants of LGR7 and LGR8 reveals that receptor signaling is mediated by their unique low density lipoprotein class A modules. Journal of Biological Chemistry.

[41] Filonzi M, Cardoso LC, Pimenta MT, Queiróz DB, Avellar MC, Porto CS, Lazari MF. Relaxin family peptide receptors Rxfp1 and Rxfp2: Mapping of the mRNA and pro‐ tein distribution in the reproductive tract of the male rat. Reproductive Biology and

[42] Feugang JM, Rodriguez‐Munoz JC, Willard ST, Bathgate RA, Ryan PL. Examination of relaxin and its receptors expression in pig gametes and embryos. Reproductive Biology

[43] Feugang JM, Rodríguez‐Muñoz JC, Dillard DS, Crenshaw MA, Willard ST, Ryan PL. Beneficial effects of relaxin on motility characteristics of stored boar spermatozoa. Reproductive Biology and Endocrinology. 2015;**13**:24. DOI: 10.1186/s12958‐015‐0021‐4

[44] Satchell L, Glister C, Bleach EC, Glencross RG, Bicknell AB, Dai Y, Anand‐Ivell R, Ivell R, Knight PG. Ovarian expression of insulin‐like peptide 3 (INSL3) and its receptor (RXFP2) during development of bovine antral follicles and corpora lutea and measure‐ ment of circulating INSL3 levels during synchronized estrous cycles. Endocrinology.

[45] Hanna CB, Yao S, Patta MC, Jensen JT, Wu X. Expression of insulin‐like 3 (INSL3) and dif‐ ferential splicing of its receptor in the ovary of rhesus macaques. Reproductive Biology

[46] Takezawa Y, Yoshida K, Miyado K, Sato M, Nakamura A, Kawano N, Sakakibara K, Kondo T, Harada Y, Ohnami N, Kanai S, Miyado M, Saito H, Takahashi Y, Akutsu H, Umezawa A. *β*‐catenin is a molecular switch that regulates transition of cell‐cell adhe‐

[47] Caballero JN, Gervasi MG, Veiga MF, Dalvit GC, Perez‐Martínez S, Cetica PD, Vazquez‐ Levin MH. Epithelial cadherin is present in bovine oviduct epithelial cells and gametes, and is involved in fertilization‐related events. Theriogenology. 2014;**81**:1189‐11206. DOI:

[48] Marín‐Briggiler CI, Veiga MF, Matos ML, Echeverría MF, Furlong LI, Vazquez‐Levin MH. Expression of epithelial cadherin in the human male reproductive tract and gam‐ etes and evidence of its participation in fertilization. Molecular Human Reproduction.

2005;**11**:591‐600. DOI: 10.1093/molehr/gah205

128 Goat Science

2006;**281**:34942‐34954. DOI: 10.1074/jbc.M602728200

Endocrinology. 2007;**5**:29. DOI: 10.1186/1477‐7827‐9‐10

2013;**154**:1897‐1906. DOI: 10.1210/en.2012‐2232

10.1016/j.theriogenology.2014.01.028

2008;**14**:561‐571. DOI: 10.1093/molehr/gan053

and Endocrinology. 2011;**9**:10. DOI: 10.1186/1477‐7827‐9‐10

and Endocrinology. 2010;**8**:150. DOI: 10.1186/1477‐7827‐8‐150

sion to fusion. Scientific Reports. 2011;**1**:68. DOI: 10.1038/srep00068


**Chapter 7**

Provisional chapter

**Estrus Synchronization and Artificial Insemination in**

DOI: 10.5772/intechopen.74236

Goats are small ruminants found worldwide. They provide humans with meat, milk and skin. In many rural communities, goats serve as a store of economic value and are used in cultural celebration. The world population in rapidly growing and is predicted to reach 9.6 billion by 2050. Human population explosion will exert immense pressure on the availability of food resources. Goats provide an excellent source of food to feed the world growing population. In order to increase goat population, advanced reproductive biotechnologies must be employed. These methods include and it not limited to estrus synchronization artificial insemination. Estrus synchronization is achieved by manipulation of the estrous cycle using exogenous hormones such as progestagens, gonadotrophins, and prostaglandins. Artificial insemination can be described as all the processes involved in semen collection from a male, evaluation, processing, and eventual deposition in the vaginal of a suitable female to cause conception. Adequate knowledge about male and female reproductive anatomy and physiology is critical to the application and success

Keywords: estrus synchronization, artificial insemination, goats, progestagens,

Food is one of the basic necessities of life besides clothing and shelter. Animals provide a rich source of nutrients for humans. With the increasing world population and limited natural resources, many strategies to improve the reproductive capacity of domestic livestock is progressively being explored to cater for the needs of humans. Goats are hardy small ruminants that have the potential to provide meat, milk and hides [1]. Food products from goats are

> © 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited.

© 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use,

distribution, and reproduction in any medium, provided the original work is properly cited.

Estrus Synchronization and Artificial Insemination in

**Goats**

Goats

Bobwealth Oakina Omontese

Bobwealth Oakina Omontese

http://dx.doi.org/10.5772/intechopen.74236

Abstract

prostaglandin, semen

1. Introduction

Additional information is available at the end of the chapter

of reproductive biotechnology in goat reproduction.

Additional information is available at the end of the chapter

#### **Estrus Synchronization and Artificial Insemination in Goats** Estrus Synchronization and Artificial Insemination in Goats

DOI: 10.5772/intechopen.74236

Bobwealth Oakina Omontese Bobwealth Oakina Omontese

Additional information is available at the end of the chapter Additional information is available at the end of the chapter

http://dx.doi.org/10.5772/intechopen.74236

#### Abstract

Goats are small ruminants found worldwide. They provide humans with meat, milk and skin. In many rural communities, goats serve as a store of economic value and are used in cultural celebration. The world population in rapidly growing and is predicted to reach 9.6 billion by 2050. Human population explosion will exert immense pressure on the availability of food resources. Goats provide an excellent source of food to feed the world growing population. In order to increase goat population, advanced reproductive biotechnologies must be employed. These methods include and it not limited to estrus synchronization artificial insemination. Estrus synchronization is achieved by manipulation of the estrous cycle using exogenous hormones such as progestagens, gonadotrophins, and prostaglandins. Artificial insemination can be described as all the processes involved in semen collection from a male, evaluation, processing, and eventual deposition in the vaginal of a suitable female to cause conception. Adequate knowledge about male and female reproductive anatomy and physiology is critical to the application and success of reproductive biotechnology in goat reproduction.

Keywords: estrus synchronization, artificial insemination, goats, progestagens, prostaglandin, semen

#### 1. Introduction

Food is one of the basic necessities of life besides clothing and shelter. Animals provide a rich source of nutrients for humans. With the increasing world population and limited natural resources, many strategies to improve the reproductive capacity of domestic livestock is progressively being explored to cater for the needs of humans. Goats are hardy small ruminants that have the potential to provide meat, milk and hides [1]. Food products from goats are

© 2016 The Author(s). Licensee InTech. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and eproduction in any medium, provided the original work is properly cited. © 2018 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

a delicacy in many parts of the world. However, goats have been somewhat neglected by the research community compared with other livestock species such as cattle, poultry and sheep. Goats are hardy, have high tolerance to heat stress and can survive harsh conditions. Also, goats contribute on the preservation of the ecosystems and can be used as an ecological tool for controlling the noxious weeds, reducing the incidences of wildfire, improving the rangelands and wild life habitat [2]. In many parts of the world, goats serve as a store of wealth and are used in many cultural activities. Interestingly, the male goat is seen as a symbol of fertility. Indeed, the importance of goats in the teeming efforts to ensure regional protein sufficiency and world food security cannot be overemphasized.

manipulation [5, 6]. Estrus synchronization protocols utilize several different hormones in sequence to control CL function, stimulate follicular development and regulate ovulation.

Estrus Synchronization and Artificial Insemination in Goats

http://dx.doi.org/10.5772/intechopen.74236

133

An easy-to-apply method of estrus synchronization in goats is by the use of prostaglandins to cause luteolysis so as to induce the subsequent follicular phase of the estrous cycle. In small ruminants, prostaglandin F2<sup>α</sup> is the primary luteolytic agent [7]. Since consumers demand food produced by "clean, green and ethical" methods [8], prostaglandins are a good alternative to progestagens. This is because prostaglandins are rapidly metabolized in the lungs and therefore, do not accumulate in tissues [9]. Prostaglandins are mainly administered intramuscularly and subcutaneously, although the intravulvo-submucosa route has been investigated with varying success. Several synthetic analogues have been used to induce rapid regression of the corpus luteum. Although natural PGF2α, causes normal luteolysis through gradual degenerative changes, synthetic analogues of PGF2<sup>α</sup> usually have a more rapid and dramatic effect on progesterone synthesis in the lutein cells [10]. Dinoprost thromethamine marketed as Lutalyse® and Carboprost® are frequently used natural prostaglandins, while cloprostenol sodium, marketed as Fenprostenol®, Estrumate® and estroPlan®, is a synthetic prostaglandin (Figure 1) [11, 12]. Factors reported to affect estrus response and subsequent fertility following administration of prostaglandin or its analogues include the dose level of the prostaglandin [13], the interval between administration of the prostaglandin [14], the responsiveness of the corpus luteum to the prostaglandin/stage of the oestrus cycle [15], season and the inclusion of gonadotrophins as co-treatment [16]. Several gonadotrophins such as follicle-stimulating hormone (FSH), pregnant mare serum gonadotrophin (PMSG) and gonadotrophin-releasing hormone (GnRH) have been included in the prostaglandin protocols, resulting in improved estrus response rates. Prostaglandins should be administered from day 3 of the oestrus cycle, when

Prostaglandins have the major advantage of being administered by intramuscular injection besides the reduction in hormonal residues, since it is rapidly and almost completely metabolized in the lungs [18]. Following prostaglandin administration, compromised follicular function has been reported leading to variability in the timing of ovulation [19]. It is essential that two injections of prostaglandin F2<sup>α</sup> is administered 9–11 days apart. By so doing, almost all the animals would be in the mid luteal phase of the oestrus cycle and would better respond to the second treatment [20]. Double treatment with cloprostenol sodium administered i.m., 11 days apart, resulted in higher oestrus response (92.8% versus 75%) than single treatment in Red

Another method of estrus synchronization is by the use of natural progesterone impregnated in sponges, implants or silicon elastomers, or the use of its synthetic analogues such as norgestomet, fluorogestone acetate (FGA), methyacetoxy progesterone (MAP) and medroxyprogesterone acetate (MPA) [22]. The progesterone or progestagen treatment is popularly delivered though an intravaginal sponge, intramuscular or subcutaneous routes. Natural progesterone is

3.1. Prostaglandins and their synthetic analogues

the corpus luteum of the goat is responsive to PGF2<sup>α</sup> [17].

3.2. Progesterone and its synthetic analogues

Sokoto does [21].

Efforts to multiply goats by the application of reproductive biotechnology is on the increase especially in developed countries. In fact, goat milk is a huge industry in North America and some parts of Asia. In Africa, goat meat is considered premium meat and is associated with higher prices. Goats are important in development because of their ability to convert forages and crops and household residues into meat, fiber, skins and milk [3]. Of the different biotechnology techniques viz. multiple ovulation, in vitro fertilization, embryo transfer, etc., estrus synchronization and artificial insemination (AI) are the most powerful biotechnology tools that have hasted genetic progress and enhanced fertility in goats and farm animals [4]. Adequate understanding of these tools cannot be overemphasized and must be carefully implemented in order to ensure breeding success. Reproduction is critical to success of any livestock enterprise, including goat rearing. The objective of this mini review is to describe the use of estrus synchronization and artificial insemination techniques to enhance reproductive performance of goats.

## 2. Materials and methods

To achieve our stated objective, a narrative review was carried out in February 2016. The database searched was PubMed and Google search. Search terms were "estrus synchronization in goats" and "artificial insemination in goats." A total of 301 articles were retrieved from the search out of which 146 were duplicates. These studies were carried out using different breeds of goats treated with varying hormones and protocols. Results of estrus synchronization studies carried out by the author in tropical environments were also included in the final write-up.

### 3. Estrus synchronization in goats

Estrus synchronization enables concentrated breeding that ensures uniform kid crop and proper management of pregnant does. Exogenous hormones are used to modify the physiological chain of events involved in the sexual cycle, while the non-hormonal methods of OS involve the use of light control or exposure to a male. In the doe, the window of opportunity is generally greater during the luteal phase, which is of longer duration and more responsive to manipulation [5, 6]. Estrus synchronization protocols utilize several different hormones in sequence to control CL function, stimulate follicular development and regulate ovulation.

#### 3.1. Prostaglandins and their synthetic analogues

a delicacy in many parts of the world. However, goats have been somewhat neglected by the research community compared with other livestock species such as cattle, poultry and sheep. Goats are hardy, have high tolerance to heat stress and can survive harsh conditions. Also, goats contribute on the preservation of the ecosystems and can be used as an ecological tool for controlling the noxious weeds, reducing the incidences of wildfire, improving the rangelands and wild life habitat [2]. In many parts of the world, goats serve as a store of wealth and are used in many cultural activities. Interestingly, the male goat is seen as a symbol of fertility. Indeed, the importance of goats in the teeming efforts to ensure regional protein sufficiency

Efforts to multiply goats by the application of reproductive biotechnology is on the increase especially in developed countries. In fact, goat milk is a huge industry in North America and some parts of Asia. In Africa, goat meat is considered premium meat and is associated with higher prices. Goats are important in development because of their ability to convert forages and crops and household residues into meat, fiber, skins and milk [3]. Of the different biotechnology techniques viz. multiple ovulation, in vitro fertilization, embryo transfer, etc., estrus synchronization and artificial insemination (AI) are the most powerful biotechnology tools that have hasted genetic progress and enhanced fertility in goats and farm animals [4]. Adequate understanding of these tools cannot be overemphasized and must be carefully implemented in order to ensure breeding success. Reproduction is critical to success of any livestock enterprise, including goat rearing. The objective of this mini review is to describe the use of estrus synchronization and artificial insemination techniques to enhance reproductive

To achieve our stated objective, a narrative review was carried out in February 2016. The database searched was PubMed and Google search. Search terms were "estrus synchronization in goats" and "artificial insemination in goats." A total of 301 articles were retrieved from the search out of which 146 were duplicates. These studies were carried out using different breeds of goats treated with varying hormones and protocols. Results of estrus synchronization studies carried out by the author in tropical environments were also included in the final

Estrus synchronization enables concentrated breeding that ensures uniform kid crop and proper management of pregnant does. Exogenous hormones are used to modify the physiological chain of events involved in the sexual cycle, while the non-hormonal methods of OS involve the use of light control or exposure to a male. In the doe, the window of opportunity is generally greater during the luteal phase, which is of longer duration and more responsive to

and world food security cannot be overemphasized.

performance of goats.

132 Goat Science

write-up.

2. Materials and methods

3. Estrus synchronization in goats

An easy-to-apply method of estrus synchronization in goats is by the use of prostaglandins to cause luteolysis so as to induce the subsequent follicular phase of the estrous cycle. In small ruminants, prostaglandin F2<sup>α</sup> is the primary luteolytic agent [7]. Since consumers demand food produced by "clean, green and ethical" methods [8], prostaglandins are a good alternative to progestagens. This is because prostaglandins are rapidly metabolized in the lungs and therefore, do not accumulate in tissues [9]. Prostaglandins are mainly administered intramuscularly and subcutaneously, although the intravulvo-submucosa route has been investigated with varying success. Several synthetic analogues have been used to induce rapid regression of the corpus luteum. Although natural PGF2α, causes normal luteolysis through gradual degenerative changes, synthetic analogues of PGF2<sup>α</sup> usually have a more rapid and dramatic effect on progesterone synthesis in the lutein cells [10]. Dinoprost thromethamine marketed as Lutalyse® and Carboprost® are frequently used natural prostaglandins, while cloprostenol sodium, marketed as Fenprostenol®, Estrumate® and estroPlan®, is a synthetic prostaglandin (Figure 1) [11, 12]. Factors reported to affect estrus response and subsequent fertility following administration of prostaglandin or its analogues include the dose level of the prostaglandin [13], the interval between administration of the prostaglandin [14], the responsiveness of the corpus luteum to the prostaglandin/stage of the oestrus cycle [15], season and the inclusion of gonadotrophins as co-treatment [16]. Several gonadotrophins such as follicle-stimulating hormone (FSH), pregnant mare serum gonadotrophin (PMSG) and gonadotrophin-releasing hormone (GnRH) have been included in the prostaglandin protocols, resulting in improved estrus response rates. Prostaglandins should be administered from day 3 of the oestrus cycle, when the corpus luteum of the goat is responsive to PGF2<sup>α</sup> [17].

Prostaglandins have the major advantage of being administered by intramuscular injection besides the reduction in hormonal residues, since it is rapidly and almost completely metabolized in the lungs [18]. Following prostaglandin administration, compromised follicular function has been reported leading to variability in the timing of ovulation [19]. It is essential that two injections of prostaglandin F2<sup>α</sup> is administered 9–11 days apart. By so doing, almost all the animals would be in the mid luteal phase of the oestrus cycle and would better respond to the second treatment [20]. Double treatment with cloprostenol sodium administered i.m., 11 days apart, resulted in higher oestrus response (92.8% versus 75%) than single treatment in Red Sokoto does [21].

#### 3.2. Progesterone and its synthetic analogues

Another method of estrus synchronization is by the use of natural progesterone impregnated in sponges, implants or silicon elastomers, or the use of its synthetic analogues such as norgestomet, fluorogestone acetate (FGA), methyacetoxy progesterone (MAP) and medroxyprogesterone acetate (MPA) [22]. The progesterone or progestagen treatment is popularly delivered though an intravaginal sponge, intramuscular or subcutaneous routes. Natural progesterone is

silicone elastomer molded over a nylon core and impregnated with natural progesterone (330 mg). CIDRs are preferable than sponges because they are easy to use, do not cause as much discomfort as sponges and do not adhere to the vaginal wall during use. The addition of gonadotrophins to progestagen protocols ensure a tighter synchrony and/or induces a superovulatory response in treated does [8]. The use of gonadotrophins increases the cost of oestrus synchronization and is reported to reduce fertility of does in the long-term. Besides, repeated administration of eCG is reported to produce antibodies against eCG (anti-eCG), thereby causing reduced ovarian stimula-

Estrus Synchronization and Artificial Insemination in Goats

http://dx.doi.org/10.5772/intechopen.74236

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Artificial insemination (AI) is defined as the process by which sperm are collected from the male, processed, stored and artificially introduced into the reproductive tract of a female for the purpose of conception. It is essentially the most important techniques for genetic improvement of farm animals. Although AI is most widely used for breeding dairy cattle, it is an indispensable tool for genetic improvement in small ruminants and poultry. AI has an interesting history; from the Arabian chieftain who introduced a wand of cotton into a mare's reproductive tract to collect semen in 1322 A.D., to Anthony van Leeuwenhook who first observed human spermatozoa under magnification, to Spallanzani who is described as the inventor of AI for successfully conducting AI in dogs and the Russian scientist Ivanoff who pioneered AI research in birds, horses, cattle and sheep, and was the first to successfully artificially inseminate cattle. Artificial insemination is and continues to be an essential reproductive technique for genetic purposes including creation and diffusion of genetic progress

AI has several advantages of which the greatest is the ability to maximize superior sires for genetic improvement. AI prevents spread or exposure of sires to infectious genital diseases. In addition, bull evaluation that accompanies AI enables early detection of infertile bulls, eliminated handling of stubborn bulls and allows use of bulls unable to mount due to foot injuries. Importantly AI also helps ensure that accurate breeding records can be kept. As with many scientific techniques, the disadvantages of AI include increased cost associated with labor and facilities. In addition, AI only allows utilization of a few sires, which reduces genetic base. Also, there is potential for rapid spread of undesirable traits, if bucks from which semen is sourced are not carefully evaluated, hence, if the buck had a genetic defect this will be widely spread in the population. Therefore optimum care and critical evaluation of semen from bucks

For AI to be successful, quality semen must be used. The quality of semen is determined by proper collection, extension and storage. Several methods of obtaining semen have been

tion after subsequent treatments [23].

4. Artificial insemination in goats

and conservation of genetic resources.

4.1. Advantages and disadvantages of AI

to be used for artificial insemination is of paramount importance.

4.2. Collection, extension and storage of semen

Figure 1. Some hormones used for estrus synchronization in goats. Hormones are mostly administered via the intramuscular, intravaginal, oral or intradermal route (picture by B.O. Omontese).

mainly marketed as Sil-Oestrus® implant and Eazi-Breed® controlled internal drug release devices™ (CIDR) (Figure 1). Synthetic analogues are marketed as Chronogest® (Intervet, Angers, France) and Veramix sponges® (Pharmacia & Upjohn, Orangevillle, Canada). Traditionally, intravaginal sponges are inserted over periods of 9–21 days and in most cases, eCG or PGF2<sup>α</sup> is administered 2 days before at the end of pessaries removal. Factors that affect the success of an OS programme when progestagens are applied include species, breed, co-treatment, management, stage of the oestrus cycle, duration of treatment and mating system.

The use of long-term progestagen treatments has been shown to result in lowered fertility rates in goats [22]. On the other hand, decreased periods of progestagen treatment may minimize vaginal discharge and infection, and increase fertility. Currently, short-term intravaginal progestagen treatment is advocated. Following withdrawal, does usually show overt oestrus within 48 h. More recently, an alternative means of supplying continuous, exogenous progesterone has been the CIDR's, developed for sheep and goats in New Zealand. It is made from medical

silicone elastomer molded over a nylon core and impregnated with natural progesterone (330 mg). CIDRs are preferable than sponges because they are easy to use, do not cause as much discomfort as sponges and do not adhere to the vaginal wall during use. The addition of gonadotrophins to progestagen protocols ensure a tighter synchrony and/or induces a superovulatory response in treated does [8]. The use of gonadotrophins increases the cost of oestrus synchronization and is reported to reduce fertility of does in the long-term. Besides, repeated administration of eCG is reported to produce antibodies against eCG (anti-eCG), thereby causing reduced ovarian stimulation after subsequent treatments [23].
