Characterization of the Reproductive Cycle in Female Bharals (Pseudois Nayaur) Based on the Changes in Serum Progesterone Concentrations and Parturition Season
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FULL PAPER Theriogenology Characterization of the Reproductive Cycle in Female Bharals (Pseudois nayaur) Based on the Changes in Serum Progesterone Concentrations and Parturition Season Satoshi KUSUDA1), Hirotada NAGAMI2), Kayoko UEDA3), Tomoya NISHIKAKU4), Daisuke NAKAGAWA4) Toyoharu TAKIDA4), Daisuke KURITA4), Koji UEMICHI4), Masaki FUKAI4), Hiroshi KUBOTA4), Kaoru UEDA4), Tomoko OOE4), Kazuo OKUDA4), Hiroshi KUSUNOKI5) and Osamu DOI3)* 1)Laboratory of Animal Reproduction, United Graduate School of Agricultural Science, 2)Laboratory of Animal Reproduction, Graduate School of Agriculture, 3)Laboratory of Animal Reproduction, Faculty of Applied Biological Sciences, Gifu University, Yanagido, Gifu 501– 1193, 4)Himeji Central Park, Kodani-aza-okura, Toyotomi-cho, Himeji, Hyogo 679–2121 and 5)Laboratory of Faunal Diversity, Faculty of Agriculture, Kobe University, Rokkodai-cho, Nada-ku, Kobe, Hyogo 657–8501, Japan (Received 17 October 2005/Accepted 19 April 2006) ABSTRACT. The purpose of present study was to determine annual changes in serum progesterone (P4) concentrations and to clarify basic reproductive characteristics, such as breeding season, estrous cycle, and puberty in female bharals (Pseudois nayaur). Blood was col- lected from 9 female bharals once or twice weekly for approximately one year. Serum P4 concentrations were determined by radioim- munoassay. Serum P4 concentrations showed remarkable and cyclic changes between November/December (winter) and May/June (late spring). The mean estrous cycle was 24.9 ± 0.5 days. Chasing insistently to other females and discharge of mucus from the vulva were observed around the time when the serum P4 concentrations began to increase. The chasing behavior and discharge of mucus were con- sidered to be external indicators of estrus in female bharals. Serum P4 concentrations of a pregnant female had non-cyclic changes, and the values remained high. In this study, all 37 deliveries were between April and September, and about 70% of these were concentrated in May and June. The conception month determined on the day of birth was between October and April for all animals, and the most common month was in December (54%). This month corresponded to an early stage of the period when the serum P4 concentrations changed cyclically. These results indicate that many female bharals become pregnant at the beginning of the breeding seasons and, if they do not become pregnant, the estrous cycle, about 25 days in length, is repeated. KEY WORDS: bharal, breeding season, estrous cycle, progesterone, sexual maturation. J. Vet. Med. Sci. 68(8): 847–851, 2006 Bharal (Blue sheep: Pseudois nayaur) belong to the fam- changes in the serum progesterone (P4) concentrations of the ily Bovidae (Subfamily Caprinae), and inhabit an undulat- females. However, the endocrinological data of genus ing montane zone from the Himalayan region to Inner Pseudois has not been reported, and thus its reproductive Mongolia [6, 10]. In structure and habit, the bharal is inter- physiology has yet to be clarified. mediate between genuses Ovis and Capra, but is morpho- In Japan, bharals are currently kept at only 4 zoo facili- logically closely related to genus Capra [10]. Genus ties, Gunma Safari Park, Gunma, Kanazawa Zoological Pseudois includes two species, bharal (P. nayaur) and dwarf Gardens of Yokohama, Kanagawa, Kyoto Municipal Zoo, bharal (P. schaeferi) [6]. Wild populations of both species Kyoto, and Himeji Central Park, Hyogo. There are increas- have decreased because of decreasing habitats and the intro- ing fears about a possible decrease in genetic variability by duction of livestock, etc. Particularly, P. schaeferi and a inbreeding due to the limited number of facilities in which part of the regional populations of P. nayaur are in a critical bharals are kept. Therefore, semen collection and artificial situation because of excessive hunting for meat that insemination has been planned for animals in captivity with occurred before hunting was legally banned in 1989 and the aim of appropriate genetic and reproductive manage- because of poaching after the ban. According to the 2004 ment. IUCN Red List of Threatened Species [4], P. nayaur is clas- The purpose of the present study was to determine the sified as low risk (near threatened) and P. schaeferi is clas- annual changes in serum P4 concentrations and the parturi- sified as endangered, so it has become more important to tion season in captivity, and thus clarify basic reproductive conserve wild and captive populations. characteristics of the breeding season, estrous cycle, and It is known that the bharal is a seasonal breeding animal. puberty in female bharals. The birth season is in May-July in their natural habitat [6]. In wild species of the related genuses Ovis and Capra, such MATERIALS AND METHODS as mouflon (O. gmelini musimon) [9] and Spanish ibex (C. pyrenaica hispanica) [8], there are some reports concerning Animals and blood collection: Nine female bharals reared the breeding season, estrous cycle, and puberty based on in Himeji Central Park were studied (Table 1). They were usually kept in an approximately 14,000 m2 outdoor area of *CORRESPONDENCE TO: DOI, O., Laboratory of Animal Reproduc- tion, Faculty of Applied Biological Sciences, Gifu University, the safari style park with another 11 bharals, 21 Barbary Yanagido, Gifu 501–1193, Japan. sheep (Ammotragus lervia), 15 mouflons, 83 blackbucks 848 S. KUSUDA ET AL. Table 1. Age and body weight of the female bharals 62.2%; pregnenolone, 6.26%; 11-deoxycorticosterone, included in this study 3.88%; 17α-hydroxyprogesterone, 2.25%; 11α-hydrox- yprogesterone, 1.23%; 20α-hydroxyprogesterone, 0.51%; Individual Name Agea) Body testosterone, 0.18%; 11-deoxycortisol, 0.14%; androstene- number weight (kg)b) dione, 0.12%; 5α-dihydrotestosterone, 0.12%; corticoster- No. 1 Wurong 14.1 26.4 one, 0.07%; 17α-hydroxypregnenolone, 0.05%; No. 2 Sirong 11.2 30.5 dehydroepiandrostendione, 0.04%; and cortisol, cortisone, No. 3 Puer 5.2 30.6 No. 4 Kei 3.1 37.8 aldosterone, estrone, estradiol-17β, estriol, and androster- No. 5 Yanlong 2.1 30.0 one, 0.01%. The sensitivity of the assay was 30 pg/ml. The No. 6 Mouf 2.1 24.4 intra- and inter-assay coefficients of variation were 4.5 and No. 7 Celong 2.0 27.3 11.6%, respectively. No. 8 Ryoku 1.3 24.4 Investigation of parturition history: To investigate the No. 9 Sheets 1.3 21.5 birth season, all birth dates of the bharals at Himeji Central a) At start of the experiments. b) In January 2004. Park for 12 years within the period of 1992–2004 were totaled for each month. The day of pregnancy or age at pregnancy was determined by counting backwards 160 days (Antilope cervicapra), 2 Sika deers (Cervus nippon), 2 from the birth date of each individual [6], 160 days was the Himalayan gorals (Nemorhaedus goral), and 9 addax mean gestation period. Moreover, sexual maturity was (Addax nasomaculatus) throughout the year. During this determined based on the age at first conception. study period, which lasted from July 2003 to July 2004, the nine female bharals were kept in an outdoor paddock that RESULTS was approximately 210 m2 in size. From March 18 to July 15, 2004, 2 females (Nos. 1 and 4) were kept with three Seasonal changes in serum progesterone: The serum P4 males in an outdoor paddock that was approximately 45m2 concentrations showed remarkable changes in November, in size. The bharals were fed a daily diet of approximately December, or early January in 8 of the females, all except 500 g/head/day of alfalfa and timothy hay and approxi- female No. 7. Remarkable changes in serum P4 concentra- mately 500 g/head/day of pellet ZC (Oriental Yeast). Drink- tions continued until April, May, or June in 8 of the females, ing water was available ad libitum. all except one pregnant female No. 4 (Fig. 1). In only one Blood sampling was conducted once or twice weekly for female No. 7, the changes in serum P4 concentrations started approximately 1 year. The bharals were restrained by 2 zoo earlier than the other females, in late August. The serum P4 keepers clutching both the horns and the hind legs, respec- concentrations in the 9 females, showed repeated cyclic tively, and blood was collected from the jugular vein under changes during these periods. The length of the estrous non-anesthesia conditions. Immediately after blood sam- cycle was calculated as the number of days from the first P4 pling, the blood was put into an evacuated blood collection rise to the next P4 rise in the following cycle. The mean (± tube containing a serum-separating medium (Venoject II, SEM) length of the estrous cycle was 24.9 ± 0.5 days (n=64 Terumo). The tube was left for approximately 30 min at cycles). The shortest estrous cycle was 21 days and the room temperature, and then the serum was separated from longest was 35 days. Estrous cycles of 21–28 days made up the whole blood by centrifugation at 3,000 rpm for 10 min. 89.8% of all cycles. The number of estrous cycles during The serum samples were kept at –20°C until assay. the one breeding season varied between 4–12 cycles (Fig. Radioimmunoassay: Steroids in the serum was extracted 1). Serum P4 concentrations during July-November did not twice with diethyl ether. Radioimmunoassay for P4 was car- change and remained at basal levels in 7 of the females, all ried out using a modified version of a previous method [2]. except female No. 7 and female No. 4, which was pregnant. Briefly, a 100 µl aliquot of the assay sample, 50 µl of Chasing insistently to other females and discharge of [1,2,6,7,16,17-3H]-labeled radioligand (10,000 dpm/50 µl, mucus from the vulva were observed for females Nos.