Luteal activity of Abadeh ecotype does in summer and winter and the effect of a single dose of kisspeptin-10 injection on luteinizing hormone secretion in the anestrus does

Document Type: Original Article


1 Department of Animal Science, College of Agriculture, Shiraz University, Shiraz, Iran

2 Department of Clinical Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran

3 Transgenic Technology Research Center, Shiraz University of Medical Sciences, Shiraz, Iran

4 Department of Basic Sciences, School of Veterinary Medicine, Shiraz University, Shiraz, Iran

5 Histomorphometry and Stereology Research Center, Shiraz University of Medical Sciences and Department of Anatomical Sciences, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran


The aims of the present study were to evaluate luteal activity in Abadeh ecotype goat during summer and winter and also the effect of a single dose kisspeptin-10 injection on the secretion of luteinizing hormone (LH) in female anestrous goats. In the first study, progesterone (P4) concentration in 10 goats in summer (n = 6) and winter (n = 4) were measured every other day. Moreover, in summer group, a male teaser goat was left in the herd on days of sampling for one hour. Goats with P4 concentration ≥1 ng mL-1, at least two consecutive measurements, were considered with luteal activity. In the second study, the anestrous phase was confirmed by P4 measurement 20 and 10 days before the kisspeptin injection in five female Abadeh ecotype goats (4 to 5 years old). The goats were given a single IV injection of saline (2 mL) as control group and the same goats (1 hr after the last blood sampling) were given kisspeptin (1 μg kg-1) as treatment group. The blood samples were collected at –60, –40, –20 and 0 min (before injection), and 10, 20, 30, 40, 50, 60, 80, 100, 120 and 140 min after the injection and LH concentration were measured. A single IV injection of 1 µg kg-1 of kisspeptin-10 did not stimulate the release of LH in female anestrous goats. In summer, in the presence of teaser goat, luteal activity was seen in all goats. In the absence of male goat in winter, some goats showed luteal activity and others showed anestrus.




Goat farming plays an important role in the agricultural economy of Fars province, Iran. Based on the annual report of the Veterinary Organization of Fars province, about 6.3 million goats exist in Fars province and most of them are kept by nomads.1 In intensive goat production for easier management of gestation, parturition and kids husbandry, does were kept without bucks and in breeding season bucks were introduced to the herd; therefore, determination of the months that reproduction axis become activated is important.2 In general, goat is a short day seasonal breeder ruminant with 21 days estrous cycle and its breeding season starts in early autumn and finished in late winter.3 However, unpublished observations in local herds and slaughterhouses show that Fars native goats have different patterns in breeding season and reproductive performance that reflect their ovarian activity.

Pulsatile secretion of gonadotropin releasing hormone (GnRH) from the hypothalamus regulates the hypo-thalamo-pituitary gonadal (HPG) axis. During breeding season, high level of progesterone (P4) secreted from corpus luteum inhibits GnRH/luteinizing hormone (LH) pulse frequency. Thus, when corpus luteum regressed, GnRH/LH pulse frequencies increase and LH stimulate estradiol secretion. High level of estradiol leads to LH surge and ovulation. On the other hand, during the non-breeding season, ovaries become inactive and P4 secretion maintain at the basal level. Previous researches reported that basal level of P4 in Abadeh, Markhoz and Creole goats is 0.5, 1, and 1 ng mL-1, respectively.4-6 The first aim of study was to investigate luteal activity based on serum P4 concentration in Abadeh ecotype goats during the summer (transitional period from anoestrus to the natural breeding season) and winter (transitional period from the natural breeding season to anoestrus).

The integration of a series of central neuronal inputs that mediate environmental influences as well as sex steroid feedback and other endogenous factors (metabolic signals, stress hormones, and etc.) involve in the reproductive regulation.7,8 Male presentation in anestrous season to females in goats group induced LH secretion9 and increased the multiple-unit activity (MUA)10 within the arcuate nucleus (ARC) thought to represent a GnRH pulse modulator.11 Moreover, the MUA recordings were noted to be in close proximity to kisspeptin neurons.12,13 Kisspeptin, the product of the KiSS-1 gene, encodes a 145-amino acid peptide that is further processed to generate biologically active peptides of various lengths (10–54 amino acids) termed kisspeptins.14 Kisspeptin neurons are found in the hypothalamus, and secretion of kisspeptin strongly stimulates the secretion of gonadotropin through a G protein-coupled receptor known as GPR54.14 The actions of these peptides are thought to involve in stimulating GnRH neuronal activity through GPR54, although the possibility of additional sites of action (e.g. at the pituitary) cannot be ruled out.14 Kisspeptin stimulates LH secretion in a GnRH dependant manner by increasing GnRH secretion into the hypophysial portal blood.15,16 There are several studies in different mammalians species with different doses, routes of administration, sexes and types of kisspeptin peptide for induction of the LH release which can have effects on levels of LH (Table 1).

 In goat, kisspeptin neurons are identified in the ARC during the follicular phase, luteal phase and anestrous stage.17 Kiss-1 expression is markedly up-regulated in the ARC at the onset of the breeding season.3,18 In addition, the number of kisspeptin neurons in goat is higher in the breeding season than non-breeding season.3 An administration of kisspeptin, either centrally or peripherally, was shown to elicit the release of gonado-tropin in ruminants19-23 as well as in rats,24 pigs,25 monkeys26 and humans.27,28 In ruminants, kisspeptin has been examined mainly in sheep,18-21,29,30 with a few studies also conducted in cattle.22,23,31,32 However, there is a hypothesis that suggests kisspeptin may stimulate the release of gonadotropin in anestrous goats. Therefore, the second aim of study was to investigate the effect of a single dose injection of kisspeptin-10 on the release of LH in vivo in female anestrous goats.


Materials and Methods


All experimental protocols were approved by the Committee for Animal Experiments of Shiraz University. Both studies were conducted in the Research Station, College of Agriculture, ShirazUniversity (latitude of 29˚ 44' N and longitude of 52˚ 37' E, 1810 m above sea level). The goats were housed in open shed stalls and fed alfalfa hay, wheat straw and concentrate according to NRC;33 water was available ad libitum. One month before the start of the experiments, anti-parasitic treatment with ivermectin was conducted.

Study 1: Reproductive activity of Abadeh ecotype goat. Ten non-pregnant, non-lactating Abadeh ecotype multiparous female goats, (4 to 5 year-old and mean weight 40 kg) kept without the presence of male goats were used. Experimental periods were from 7 to 29 August 2011 in summer (mean temperature = 27.7 ˚C, day length = 13.1 ± 0.1 hr, n = 6), and in winter from 1 to 17 January 2012 (mean temperature = 7.3 ˚C, day length = 10.4 ± 0.1 hr, n = 4), respectively. In both seasons, blood samples were collected from all goats through the jugular vein to measure P4 thrice weekly. Samples were allowed to clot at room temperature for up to 1 hr, centrifuged for serum harvest (for 10 min at 3000 g) and serum samples were stored at –22 ˚C until assayed. Serum P4 concentration were determined using a validated commercial radio-immunoassay kit (Immunotech kit, Marseille, France). The intra- and inter-assay coefficients of variation (CVs) of the assays were 5.8% and 9.0%, respectively. The sensitivity of the test was 0.05 ng/mL, and the recovery rate of the assay ranged from 85.0% to 110%. Furthermore, to detect estrus during the days of sampling in non-breeding season (summer), an adult male goat (two years-old) with an apron was allowed to enter in female herd at 9:00 AM and 15:00 PM for one hour each time.

Definitions. Goats with serum P4 concentration greater than or equal to 1 ng mL-1 on at least two consecutive blood samplings were considered to have luteal activity.6 Goats did not show standing heat but their serum P4 concentrations were greater than or equal to 1 ng mL-1 were considered to silent heat. The resumption of luteal activity was classified base on serum P4 concentration: A) normal luteal activity if the first P4 rise occurred between 15 to 21 days; B) short luteal phase: more than 1 ng mL-1 serum P4 level for less than 15 days; C) anestrus: less than 1 ng mL-1 serum P4 level during the study.

Study 2: Detection of anestrous goats. Thirteen non-pregnant female Abadeh ecotype goats were selected by ultrasonography and P4 measurement from the goat herd. The experiment was performed in winter, transitional period from the natural breeding season to anoestrus (February to March). The anestrous phase was confirmed by P4 measurement. Twenty and 10 days before the kisspeptin injection, blood samples were taken by jugular venipuncture. The serum was separated by centrifugation (for 10 min at 3000 g) and stored at –22 ˚C until assayed. Serum P4 concentration were measured using the same kit as the first study. Ten (10/13) goats were detected anestrus and five (5/10) female goats (mean ± SD body weight, 34.6 ± 6.3 kg) showing levels of P4 lower than 1.0 ng mL-1 on both samplings, were selected as anestrous goats.34

LH-releasing responses to a single IV injection of kisspeptin. Five goats were given a single IV injection of saline (2 mL) as control group and 1 hr apart from the later sampling of treatment group (1 μg kg-1, supplied by Clarke IJ, Monash University, Melbourne, Australia) as treatment group. The freely moving goats were sampled (2.5 mL blood each) or injected via an indwelling catheter previously inserted into one of the jugular veins. The blood samples were collected at –60, –40, –20, 0 (just before injection), 10, 20, 30, 40, 50, 60, 80, 100, 120 and 140 min after the injection. The goats were firstly sampled 200 min as control group and after 1 hr interval were sampled as treatment group. The serum was separated by centrifugation (for 10 min at 3000 g) and stored at –22 ˚C until assayed. Serum LH concentration were measured in this experiment using validated commercial ELISA kit (goat LH ELISA kit, Cusabio Biotech Co. Ltd., Wuhan, China). The analytical sensitivity of the test was typically less than 0.24 mIU mL-1.

Statistical analysis. All data from the experiments are presented as the mean ± SEM. The statistical significance of differences in serum LH concentration between the saline-treated control and kisspeptin-treated groups was analyzed by independent sample
t-test. The statistical significance of differences in serum LH concentration between consecutive sampling times of each group was determined using paired sample t-test. All data were analyzed using the SPSS (Version 11.5, SPSS Inc., Chicago, USA). Results were considered significant at the p < 0.05 level.




Study 1. Serum P4 profiles showed that during the summer in the first week of sampling, four does had luteal activity and two does were anestrus (Fig. 1). From the third week, luteal activity of two anestrous does started and one of the cyclic animals became anestrus. During the summer only three does showed estrous behavior. During the winter based on P4 level, two does had luteal activity and two does were anestrus (Fig. 2).


Fig. 1. Patterns of serum progesterone concentration in six Abadeh ecotype goats in summer (non-breeding season). Samplings were done an hour after the presence of teaser buck. a) normal luteal activity; b) normal luteal activity and short luteal phase; c) short luteal phase and normal luteal activity; d and e) end of anestrus and beginning of luteal activity and f) end of luteal activity and beginning of anestrus. Stars show the time of heat detection.


 Fig. 2. Patterns of serum progesterone concentration in four Abadeh ecotype goats in winter (breeding season) in the absence of teaser buck during the sampling days. a) Normal luteal activity; b) short luteal phase; c and d) anestrus.


Study 2. Serum LH levels in response to a single IV injection of 1 μg kg-1 of kisspeptin in goats are shown in Figure 3. The level of serum LH concentration in the saline-injected control and kisspeptin treatment group in all sampling times were not significantly different (p > 0.05).


 Fig. 3. The serum luteinizing hormone concentration (LH, ng mL-1) in response to intravenous injections of 1 μg kg-1 body weight of kisspeptin (treatment) or saline (control) in anestrous does (Abadeh ecotype goats). Arrow indicates the time of injection. Each value represents the mean ± SEM for five animals.




Breeding season in goats starts from late in summer.3,5,6 In general, summer consider as non-breeding season for animals that have five month gestation period (sheep, goat, and deer).35 Nevertheless, based on present findings during the long days, all of six Abadeh ecotype does had luteal activity and three of them showed standing heat. In summer, two does showed luteal activity after anestrous period. Two possibilities can be raised about this finding. First, these animals entered to the breeding season normally; because it has reported that serum P4 concentration increased in Damascus goats during the august and breeding season starts from this month.36 Second, since we used buck for heat detection, male effect could facilitate ovaries activation because in Cashmere anestrous does, buck could induce ovulation.37 The “c” goat (Fig. 1) did not show standing heat or significant increase of P4 concentration, but pattern of P4 profile in this goat was more similar to “d” and “e” goats before activation of luteal activity. Silent heat in the beginning of breeding season was reported in Abadeh, Markhoz and Nubian  goats.4,5,38 Therefore, it seems that this goat was in transition period from anestrus to breeding season.

Unlike our finding, Emady et al. reported that non-breeding season in native Abadeh goats last from April to August.4 Although, they used buck for heat detection, they did not observe estrous does during the non-breeding season.4 In the present study, estrous does had P4 level less than 0.4 ng mL-1 and shows that corpus luteum is the main source for P4 secretion.39 Different P4 levels that we observed during the luteal phases may be depend on number and activity of corpora lutea as reported before.40 In spite of many goat breeds that have maximum reproductive activity during the autumn and winter,5,6 our finding in Abadeh ecotype goats showed that long-term maintenance does without buck cause anestrus in some animals during the short days.

Therefore, based on our finding, it can be concluded that presence of buck in the herd during the beginning of the breeding season or absence of buck in the herd during the late in breeding season lead to activation or deactivation of ovaries, respectively. Along with shortening of the day light, melatonin secretion increases and stimulates reproductive axis. However, melatonin is only one of the various factors that affect breeding season; according that, we observed anestrous animals during short-days when melatonin level is high. There are probably male effect and pheromone secretion, activate amygdale neurons and these neurons activate reproductive axis. In addition, male effect and melatonin together might stimulate GnRH neurons. The same reasoning could be true for anestrous season. In summer, long day light and absence of male could inhibit estrous cycle. Finally, it should be noted that for estrous behavior different factors such as genetic, temperature and nutrition are important and need more investigation.

This study is the first to examine the effect of kisspeptin on the secretion of LH in female anestrous goats. Our experiments demonstrated that single dose IV injections of 1 μg kg-1 of kisspeptin did not induce a LH-releasing effect during anestrous season in female goats. In contrast with our study, in the luteal phase of female goats, a single injection of kisspeptin-10 (IV, 1, 5 and 10 μg kg-1) stimulated the release of LH.41 Maximum values (1.5 ng mL-1) were observed 20 to 30 min after the injection.41 Moreover in male goats, a single injection of kisspeptin-10 (IV, 5 µg kg-1) significantly stimulated the release of LH.42 Therefore, the minimum dose level of kisspeptin-10 could not increase LH in acyclic goats.

In ovariectomized ewes, injection of ovine kisspeptin (IV, 3mg) increased serum LH concentration.20 This dose was about 10-times more than the doses used in the present study. In addition, in anestrous season, administration of human kisspeptin 112-121 (ICV, 0.2 μg per min for 4 hr) in ovariectomized estradiol treated sheep increased serum LH concentration.19 Apart from the injection site, resulting in faster drug reaching the hypothalamus in that study, longer duration of administration compared with the present study could stimulate LH secretion in anestrous phase. On the other hand, in estradiol-treated ovariectomized ewes during the anestrous season, injections (IV, 6 nmol) of doses as low as human C- terminal decapeptide Kiss-1 elevated plasma LH in anestrous season.21 Furthermore, infusion of kisspeptin (IV, 12.4 nmol per hr, for either 30 or 48 hr) caused ovulation in more than 80% of kisspeptin-treated ewes, whereas less than 20% of control ewes ovulated.21 During the breeding season and in P4-synchronized cyclical ewes, constant infusion of murine C-terminal kisspeptin decapeptide-10 (IV, 0.48 μmol per hr over 8 hr) was administered 30 hr after withdrawal of a P4 priming period, and surge responses in LH occurred within 2 hr.21

Murine C-terminal kisspeptin decapeptide was equi-potent to human C-terminal kisspeptin decapeptide in terms of the release of LH.21 Infusion of kisspeptin-10 (IV, 15.2 nmol per hr) induced a well-synchronized LH surge (around 22 hr after the start of the kisspeptin infusion) in seasonally acyclic ewes.42 Therefore, in anestrous animals, site of injections, pretreatment with estradiol or increase of kisspeptin doses or duration of administration could increase the chance of LH release in anestrous animal.

Consistent with our findings, subcutaneous injection of the 0.1, 0.3, 1 and 50 nmol kisspeptin-10 and kisspeptin-14, did not increased plasma LH at 60 min post-injection in adult male rat.44 Moreover, a single bolus of human metastin 45-54 (IV, 10 μg) during the last 3 hr of the continuous 4 days administration of human metastin 45 to 54 in agonadal juvenile male monkeys on day 4 did not robust LH release.45

In summary, our study presented the first effort to evaluate the influence of kisspeptin on the secretion of LH, in female anestrous goats. The results clearly showed that single dose IV injection of 1 µg kg-1 of kisspeptin-10 did not stimulate the release of LH during the anestrous animal in female Abadeh ecotype goats.




This research was financially supported by the Vice-Chancellor for Research, Shiraz University, Shiraz, Iran. The authors would like to acknowledge Iain J. Clarke, Monash University, Melbourne, Australia for providing kisspeptin-10 peptide.



  1. Fars Veterinary General Office. Statistics of animal populations 2013. Available at: fa/statistical/1/. Accessed Nov 2, 2014.
  2. Khaldari M. Principles of sheep and goat husbandry. 2nd ed. Tehran, Iran: Jahad-Daneshgahi Publication 2005: 505.
  3. Chemineau P, Malpaux B, Delgadillo JA, et al. Control of sheep and goat reproduction: Use of light and melatonin. Anim Reprod Sci 1992; 30(1):157-184.
  4. Emady M, Ahmadi N, Kafi M, et al. Preliminary studies on reproductive activities of local Abadeh does, Fars province, southern Iran. Iran J Vet Res 2006; 7(3): 17-22.
  5. Farshad A, Akhondzadeh S, Zamiri MJ, et al. The estrous cycle of the Markhoz goat in Iran. Asian-Aust J Anim Sci 2008; 21(10): 1411-1415.
  6. Rivera GM, Alanis GA, Chaves MA, et al. Seasonality of estrus and ovulation in Creole goats of Argentina. Small Rumin Res 2003; 48(2): 109-117.
  7. Clarke IJ. Control of GnRH secretion: One step back. Front Neuroendocrinol 2011; 32(3): 367-375.
  8. Crown A, Clifton DK, Steiner RA. Neuropeptide signaling in the integration of metabolism and reproduction. Neuroendocrinology 2007; 86(3): 175-182.
  9. Delgadillo JA, Vielma J, Hernandez H, et al. Male goat vocalizations stimulate the estrous behavior and LH secretion in anestrous goats that have been previously exposed to bucks. Horm Behav 2012; 62(4): 525-530.
  10. Murata K, Wakabayashi Y, Sakamoto K, et al. Effects of brief exposure of male pheromone on multiple-unit activity at close proximity to kisspeptin neurons in the goat arcuate nucleus. J Reprod Dev 2011; 57(2): 197-202.
  11. Okamura H, Murata K, Sakamoto K, et al. Male effect pheromone tickles the gonadotrophin-releasing hormone pulse generator. J Neuroendocrinol 2010; 22(7): 825-832.
  12. Ohkura S, Takase K, Matsuyama S, et al. Gonado-trophin-releasing hormone pulse generator activity in the hypothalamus of the goat. J Neuroendocrinol 2009; 21(10): 813-821.
  13. Wakabayashi Y, Nakada T, Murata K, et al. Neurokinin B and dynorphin A in kisspeptin neurons of the arcuate nucleus participate in generation of periodic oscillation of neural activity driving pulsatile gonadotropin-releasing hormone secretion in the goat. J Neurosci 2010; 30(8): 3124-3132.
  14. Caraty A, Franceschini I. Basic aspects of the control of GnRH and LH secretions by kisspeptin: Potential applications for better control of fertility in females. Reprod Domest Anim 2008; 43(S2): 172-178.
  15. Gottsch ML, Cunningham MJ, Smith JT, et al. A role for kisspeptins in the regulation of gonadotropin secretion in the mouse. Endocrinology 2004; 145(9): 4073-4077.
  16. Smith JT, Li Q, Yap KS, et al. Kisspeptin is essential for the full preovulatory LH surge and stimulates GnRH release from the isolated ovine median eminence. Endocrinology 2011; 152(3): 1001-1012.
  17. Jafarzadeh Shirazi MR, Zamiri MJ, Salehi MS, et al. Differential expressions of RF amide-related peptide, a mammalian gonadotropin-inhibitory hormone ortholog, and kisspeptin in the hypothalamus of Abadeh ecotype does during breeding and anestrous seasons. J Neuroendocrinol 2014; 26(3): 186-194.
  18. Smith JT, Li Q, Pereira A, et al. Kisspeptin neurons in the ovine arcuate nucleus and preoptic area are involved in the preovulatory luteinizing hormone surge. Endocrinology 2009; 150(12): 5530-5538.
  19. Messager S, Chatzidaki EE, Ma D, et al. Kisspeptin directly stimulates gonadotropin-releasing hormone release via G protein-coupled receptor 54. Proc Natl Acad Sci 2005; 102(5): 1761-1766.
  20. Arreguin-Arevalo JA, Lents CA, Farmerie TA, et al. KiSS-1 peptide induces release of LH by a direct effect on the hypothalamus of ovariectomized ewes. Anim Reprod Sci 2007; 101(3):265-275.
  21. Caraty A, Smith JT, Lomet D, et al. Kisspeptin synchronizes preovulatory surges in cyclical ewes and causes ovulation in seasonally acyclic ewes. Endocrinology 2007; 148(11): 5258-5267.
  22. Kadokawa H, Matsui M, Hayashi K, et al. Peripheral administration of kisspeptin-10 increases plasma concentration of GH as well as LH in prepubertal Holstein heifers. J Endocrinol 2008; 196(2): 331-334.
  23. Whitlock BK, Daniel JA, Wilborn RR, et al. Interaction of estrogen and progesterone on kisspeptin-10-stimulated luteinizing hormone and growth hormone in ovariectomized cows. Neuroendocrinology 2008; 88(3): 212-215.
  24. Tovar S, Vazquez MJ, Navarro VM, et al. Effects of single or repeated intravenous administration of kisspeptin upon dynamic LH secretion in conscious male rats. Endocrinology 2006; 147(6): 2696-2704.
  25. Lents CA, Heidorn NL, Barb CR, et al. Central and peripheral administration of kisspeptin activates gonadotropin but not somatotropin secretion in prepubertal gilts. Reproduction 2008; 135(6): 879-887.
  26. Shahab M, Mastronardi C, Seminara SB, et al. Increased hypothalamic GPR54 signaling: A potential mechanism for initiation of puberty in primates. Proc Natl Acad Sci 2005; 102(6): 2129-2134.
  27. Dhillo WS, Chaudhri OB, Patterson M, et al. Kisspeptin-54 stimulates the hypothalamic-pituitary gonadal axis in human males. J Clin Endocrinol Metab 2005; 90(12): 6609-6615.
  28. Dhillo WS, Chaudhri OB, Thompson EL, et al. Kisspeptin-54 stimulates gonadotropin release most potently during the preovulatory phase of the menstrual cycle in women. J Clin Endocrinol Metab 2007; 92(10): 3958-3966.
  29. Pompolo S, Pereira A, Estrada KM, et al. Colocalization of kisspeptin and gonadotropin-releasing hormone in the ovine brain. Endocrinology 2006; 147(2): 804-810.
  30. Estrada KM, Clay CM, Pompolo S, et al. Elevated KiSS-1 expression in the arcuate nucleus prior to the cyclic preovulatory gonadotrophin-releasing hormone/ lutenising hormone surge in the ewe suggests a stimulatory role for kisspeptin in oestrogen-positive feedback. J Neuroendocrinol 2006; 18(10): 806-809.
  31. Suzuki S, Kadokawa H, Hashizume T. Direct kisspeptin-10 stimulation on luteinizing hormone secretion from bovine and porcine anterior pituitary cells. Anim Reprod Sci 2008; 103(3): 360-365.
  32. Kadokawa H, Suzuki S, Hashizume T. Kisspeptin-10 stimulates the secretion of growth hormone and prolactin directly from cultured bovine anterior pituitary cells. Anim Reprod Sci 2008; 105(3): 404-408.
  33. National Research Council. Nutrient Requirements of Goats: Angora, Dairy, and Meat Goats in Temperate and Tropical Countries. National Academy Press 1981; 10-17.
  34. Veliz FG, Poindron P, Malpaux B, et al. Positive correlation between the body weight of anestrous goats and their response to the male effect with sexually active bucks. Reprod Nutr Dev 2006; 46(6): 657-662.
  35. Malpaux B. Seasonal regulation of reproduction in mammals. In: Neill JD (Eds). Knobil and Neill`s physiology of reproduction. 3rd ed. St. Louis, USA: Elsevier Academic Press 2006; 2231-2281.
  36. Zarkawi M, Al-Masri MR. Use of radioimmunoassay to measure progesterone levels during different reproductive stages in female Damascus goats. Trop Anim Health Prod 2002; 34(6): 535-539.
  37. Walkden-Brown SW, Restall BJ. The male effect in the Australian Cashmere goat. 1. Ovarian and behavioural response of seasonally anovulatory does following the introduction of bucks. Anim Reprod Sci 1993; 32(1): 41-53.
  38. Thompson FN, Abrams E, Miller DM. Reproductive traits in Nubian dairy goats. Anim Reprod Sci 1983; 6(1): 59-65.
  39. Bauernfeind M, Holtz W. Progesterone and estrogen levels in serum of cycling goats measured by enzyme immunoassay. Small Ruminant Res 1991; 6(1): 95-102.
  40. Chemineau P, Gauthier D, Poirier JC, et al. Plasma levels of LH, FSH, prolactin, oestradiol-17β and progesterone during natural and induced oestrus in the dairy goat. Theriogenology 1982; 17(3): 313-323.
  41. Hashizume T, Saito H, Sawada T, et al. Characteristics of stimulation of gonadotropin secretion by kisspeptin-10 in female goats. Anim Reprod Sci 2010; 118(1): 37-41.
  42. Saito H, Sawada T, Yaegashi T, et al. Kisspeptin-10 stimulates the release of luteinizing hormone and testosterone in pre- and post-pubertal male goats. Anim Sci J 2012; 83(6): 487-492.
  43. Sébert ME, Lomet D, Ben Saïd S, et al. Insights into the mechanism by which kisspeptin stimulates a preovulatory LH surge and ovulation in seasonally acyclic ewes: Potential role of estradiol. Domest Anim Endocrinol 2010; 38(4): 289-298.
  44. Thompson EL, Murphy KG, Patterson M, et al. Chronic subcutaneous administration of kisspeptin-54 causes testicular degeneration in adult male rats. Am J Physiol-Endocrinol Metab 2006; 291(5): 1074-1082.
  45. Seminara SB, DiPietro MJ, Ramaswamy S, et al. Continuous human metastin 45-54 infusion desensitizes G protein-coupled receptor 54-induced gonadotropin-releasing hormone release monitored indirectly in the juvenile male Rhesus monkey (Macaca mulatta): A finding with therapeutic implications. Endocrinology 2006; 147(5): 2122-2126.
  46. George JT, Veldhuis JD, Roseweir AK, et al. Kisspeptin-10 is a potent stimulator of LH and increases pulse frequency in men. J Clin Endocrinol Metab 2011; 96(8): 1228-1236.
  47. Jayasena CN, Nijher GMK, Chaudhri OB, et al. Subcutaneous injection of kisspeptin-54 acutely stimulates gonadotropin secretion in women with hypothalamic amenorrhea, but chronic administration causes tachyphylaxis. J Clin Endocrinol Metab 2009; 94(11): 4315-4323.
  48. Navarro VM, Castellano JM, Fernández-Fernández R, et al. Developmental and hormonally regulated messenger ribonucleic acid expression of KiSS-1 and its putative receptor, GPR54, in rat hypothalamus and potent luteinizing hormone-releasing activity of KiSS-1 peptide. Endocrinology 2004; 145(10): 4565-4574.
  49. Thompson EL, Patterson M, Murphy KG, et al. Central and peripheral administration of kisspeptin-10 stimulates the hypothalamic-pituitary-gonadal axis. J Neuroendocrinol 2004; 16(10): 850-858.
  50. Patterson M, Murphy KG, Thompson EL, et al. Administration of kisspeptin-54 into discrete regions of the hypothalamus potently increases plasma luteinising hormone and testosterone in male adult rats. J Neuroendocrinol 2006; 18(5): 349-354.
  51. Pheng V, Uenoyama Y, Homma T, et al. Potencies of centrally-or peripherally-injected full-length kisspeptin or its C-terminal decapeptide on LH release in intact male rats. J Reprod Dev 2009; 55(4): 378-382.
  52. Matsui H, Takatsu Y, Kumano S, et al. Peripheral administration of metastin induces marked gonado-tropin release and ovulation in the rat. Biochem Biophys Res Commun 2004; 320(2): 383-388.
  53. Roa J, Vigo E, Castellano JM, et al. Hypothalamic expression of KiSS-1 system and gonadotropin-releasing effects of kisspeptin in different reproductive states of the female Rat. Endocrinology 2006; 147(6): 2864-2878.
  54. Ramaswamy S, Seminara SB, Pohl CR, at al. Effect of continuous intravenous administration of human metastin 45-54 on the neuroendocrine activity of the hypothalamic-pituitary-testicular axis in the adult male rhesus monkey (Macaca mulatta). Endocrinology 2007; 148(7): 3364-3370.
  55. Briant C, Schneider J, Guillaume D, et al. Kisspeptin induces ovulation in cycling Welsh pony mares. Anim Reprod Sci 2006; 94(1): 217-219.
  56. Ezzat Ahmed A, Saito H, Sawada T, et al. Characteristics of the stimulatory effect of kisspeptin-10 on the secretion of luteinizing hormone, follicle-stimulating hormone and growth hormone in prepubertal male and female cattle. J Reprod Dev 2009; 55(6): 650-654.