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Seasonal variation in plasma testosterone, luteinizing hormone concentrations and LH-RH responsiveness in mature, male rusa deer (Cervus rusa timorensis)
Camp. Biochem. Physiol. Vol. 83A, No. 2, pp. 347-351,
Printed
in Great
0300-9629/X6 $3.00 + 0.00 ‘\c 1986 Pergamon Press Ltd
1986
Britain
SEASONAL VARIATION IN PLASMA TESTOSTERONE, LUTEINIZING HORMONE CONCENTRATIONS AND LH-RH RESPONSIVENESS IN MATURE, MALE RUSA DEER (CERF’US RUSA ZXl4OREAWS) SIMONE VAN *University Telephone: Laboratory,
MOURIK,* T. STELMAsrAKt and K. H. OUTCH~
of Melbourne, School of Agriculture and Forestry, Parkville, Victoria 3052, Australia. (03) 345 1844; TDepartment of Agriculture and Rural Affairs, Attwood Veterinary Research Westmeadows, Victoria 3047; fDepartment of Chemical Pathology, Prince Henry Hospital, Melbourne, Victoria 3004, Australia (Received 7 June 1985)
Plasma testosterone and luteinizing hormone (LH) concentrations in immobilized or yarded rusa stags (Cerous rusa rimorensis) were investigated over a two-year period. 2. Testosterone concentrations showed a minor elevation in autumn (May) and reached maximal levels in late winter-early spring (August) coinciding with the rut. 3. Luteinizing hormone in plasma was only detectable from January to May. 4. Maximal responsiveness of the pituitary-gonadal axis to LH-RH stimulation was recorded in August. 5. The combination of FentazK (fentanylcitrate and azaperone) and Rompun’x (xylazine hydrochloride) for immobilizing deer influences hypothalamic function. Abstract-l.
INTRODUCTION The presence of antlers in cervids and mechanism of the process of their seasonal growth have been a subject of a substantial research effort over the years. Because of the social function of antlers (Bubenik, 1Y83) antlers develop in close relationship with the sexual cycle of each particular species. As long as 2000 years ago Aristotle realized that antler development was related to testicular function “If stags be mutilated when, by reason of their age, they have as yet not horns, they never grow horns at all; if they be mutilated when they have horns, the horns remain unchanged in size and the animal does not loose them”. More recently the development of specific radioimmunoassays has resulted in information on the annual concentrations of several hormones for different cervid species. This has provided insight into the antler growth process and reproductive seasonality. Testosterone (T) and luteinizing hormone (LH) concentrations have been reported for white-tailed deer (Odocoileus oirginiunus), red deer (Ceruus eluphus), roe deer (Cupreolus capreolus) and reindeer (Rangijer tarandus) by Bubenik et al. (1977, 1982, 1983), McMillan et al. (1974), Mirarchi et al. (1978). Haigh et al. (1984), Lincoln (1971), Suttie et al. (1984), Barth et al. (1976). Schams and Barth (1982), Sempere et al. (1981, 1982), Short and Mann (1966), Leader-Williams (1979) and Whitehead and McEwan (1973), respectively. These boreal species all show a distinct annual pattern in T and LH concentrations relative to a short, well-defined rutting and antler growth period. In contrast, rusa deer (Cercus rusa timorensis) exhibit an extended rutting period from late winter (July) to the start of summer (October) as well as different
antler growth pattern. The velvet shedding takes several weeks and velvet pieces might still be attached to the antlers when they are cast round December. We have therefore investigated the following aspects in mature, male rusa deer: (1) Annual pattern of testosterone (T) and luteinizing hormone (LH) concentrations; (2) Pituitary responsiveness to luteinizing hormone releasing hormone stimulation (LH-RH) at different times during the year. (3) The effect of cyproterone-acetate on T concentrations and subsequent rutting activities. MATERIALS
AND METHODS
Animals All blood samples were collected from mature, deep kept under farmed conditions in Victoria, (38”42’S, 146”6’E).
male rusa Australia
Blood sample collection Blood samples (10 ml) from non-immobilized deer were a heparinized vacutainer following collected into venepuncture as the animal was manually restrained in the yard. Drugs used for immobilization of deer were: Fentaz” (Ethnor Pty Ltd, North Ryde, NSW; fentanylcitrate, 10 mg/ml, azaperone, 80 mg/ml), Rompun ’ (Bayer AC. Leverkusen, West Germany; xylazine hydrochloride) Ketalar% (Parke Davis Pty Ltd, Caringbah, NSW; ketamine
hydrochloride) (Van Mourik and Stelmasiak. 1984a). Samples from immobilized deer were collected into heparinized test tubes following venepuncture during velveting procedures, or after cannulation of the jugular vein (Van Mourik and Stelmasiak, 1984b). Treatments Cyproterone acetate (Schering AG, Berlin, A biweekly dose of 3 ml of solution
many).
347
West Gercontaining
Testosterone and LH in deer with Fentaz” and Rompun” than in those which were immobilized with Rompun” and Ketalar” mixture. LH was only detectable in plasma samples collected in this time of the year. If the drugs suppress hormone concentrations this observation indicates that LH definitely peaks between January-April. Testosterone concentrations in plasma collected in
349
May from immobilized stags were also the highest, compared to the previous months, indicating a peak. The high concentrations of LH druing decreasing day-length are in agreement with results for other deer species mentioned and seasonally breeding mammals such as sheep (Pelletier and Ortavant, 1975). Endocrine and histological studies in white-tailed
6
T -(
;
10
I
(0% B
=
4
B
Sample (a)
4
April.
Sample (b)
May.
- 130
60
I
\
90
0
B
4
(c)
Fig. 2. Plasma
12
Sample
June.
T and LH concentrations
B
4
Sample
(d)
12
August
(means k SD) in stags (N = 5) after administration LH-RH.
of 500 ng
3.50
SIMONEVANMOURIK,T. STELMASIAK and K. M. OUTCH
deer, roe deer, black-tailed deer and red deer indicate that the seasonal rhythm does not have just one peak. Bubenik et al. (1979) showed that two peaks of oestradiol-17b occur in mature white-tailed deer, one in October-November just before the rut and the other in April-May at the beginning of antler growth. Bubenik et al. (1982) also demonstrated two peaks in gonadotrophin activity in white-tailed deer. First an LH peak in July and an FSH peak in September and subsequently a synchronous increase in March, although there was no rise in serum testosterone related to the March rise in gonadotrophin levels. In roe deer an annual biphasic elevation in testosterone concentration has been reported (Gimenez et al., 1975; Barth et al., 1976; Schams and Barth, 1982). West and Nordan (1976) noted that spermatogenic activity in black-tailed deer was at a peak in November and declined sharply through January-March. However, in May spermatogenic activity was observed in nearly all tubules, but had declined again by July. Frankenberger (1953) observed changes in the proportion and absolute number of testicular interstitial cells in red deer shot throughout the year. Peaks occurred before the rut in late August followed by a decline and another peak in January. Despite the occurrence of an elevation of testosterone concentrations in May (autumn), the major rutting period for rusa stags starts at the end of July and extends to October. The May T rise stimulates male sexual behaviour, expressed as “fleshmen” towards hinds with calves at foot (Van Mourik, 1986a, b). This can be considered as “autumn-rutting” in contrast to spring-time rutting behaviour which has been reported in red deer (Fletcher and Short, 1974) and caribou (Whitehead and McEwan, 1973). Occasional births are recorded well out of season, indicating that a rusa stag population is capable of breeding nearly the whole year round. This is in agreement with Bubenik ef al. (1982) who stated that maximal concentrations of T is not required for the process of spermatogenesis and shedding of velvet in white-tailed deer. However, their statement that maximal concentrations of T are essential for the manifestation of behavioural rut cannot be confirmed with our observations on rusa stags. The absence of a detectable annual pattern in basal concentration of LH and T in pretreatment samples in immobilized stags for LH-RH responsiveness tests, indicates an inhibition of hypothalamic secretion by Fentaz’-RompunH mixture. It might be assumed that the drugs inhibited LH-RH, LH and subsequently testosterone secretion. The inhibitory effect of Fentaz”-Rompun” mixture on hypothalamus provides a convenient model for study of seasonal changes in responsiveness of pituitarytesticular axis to LH-RH. The maximal responsiveness, expressed in testosterone concentrations was recorded in August, coinciding with the rut. No alterations in testosterone concentrations were noticed in May after LH-RH administration, but LH concentrations reached highly elevated levels in contrast to other times of the year. Whitehead and West (1977) determined the metabolic clearance and production rates of testosterone at different times of the year in male caribou and reindeer. They found lower production rates and
higher clearance rates during the non-reproductive season than during mid-rut. In the tammar wallaby (Macropus eugenii) low progesterone concentrations were also associated with low production rates and high metabolic clearance rates (Sernia et al., 1980). The time lapse from injection of immobilizing drugs to collection of first pre-treatment sample was around 40 min. Although testosterone concentrations fluctuate over the year with maximum levels during the rut, the concentration in plasma samples for baseline levels from immobilized stags was consistently below 5 nmol/l. This would indicate a higher metabolic clearance rate during the reproductive season in contrast with the above mentioned species, The antler growth of rusa deer starts in January and shedding of the velvet commences in May. The antlers are mineralized in August and cast in December. Administration of cyproterone acetate (CA) resulted in a rapid drop in testosterone concentrations to undetectable levels. The decrease in testosterone concentration reactivated the growth of the velvet antlers and in addition caused the abolishment of rutting behaviour. The unusual nature of the sexual cycle of rusa deer (long-day breeder) as compared with other cervidae (short-day breeders) further illustrates the differences in sensitivity to photoperiodic stimulation (Van Mourik and Stelmasiak, 1985) and indicates that the endogenous mechanisms regulating the gonadal functions may differ between species, Acknowledgements-The authors thank Willow Ware Australia Pty Ltd for use of animals. Bayer AC for their generous gift of Rompun”, Ethnor Pty Ltd for donation of Fentaz”, Hoechst AG for provision of LH-RH, Schering A.G. for cyproterone acetate and Dr P. Taylor, Mr D. Piggin, Mr M. Vella for assistance in blood sample collection and MS M. Katsis for typing the manuscript. This study was supported by the Reserve Bank of Australia and Commonwealth Special Research Grant.
REFERENCES Barth D., Gimenez T.. Hoffman B. and Karg H. (1976) Testosteronkonzentrationen im peripheren Blut beim Rehbock (Capreolus capreolus). Z. Jagdbviss. 22, I34 148. Bubenik A. B. (1983) The behavioral aspects of antlerogenesis. In Antler Deoelopment in Ceruidae (Edited by Brown R. D.). Caesar Kleberg Wildlife Research Institute, Kingsville, Texas. Bubenik G. A., Bubenik A. B., Brown G. M. and Wilson D. A. (I 977) Sexual stimulation and variations of plasma testosterone in normal, antiandrogen and antiestrogentreated white-tailed deer (Odocoileus virginianus) during the annual cycle. In XIIIth Congress of Game Biologists, Atlanta, Georgia, USA. pp. 377 386. Bubenik G. A., Morris _I. M., Schams D. and Claus A. (1982) Photoperiodicity and circannual levels of LH, FSH and testosterone in normal and castrated male, whitetailed deer. Can. J. PhysioI. Pharmacol. 60, 788-793. Bubenik G. A.. Bubenik A. B.. Schams D. and Leatherland J. F. (1983) Circadian and circannual rhythms of LH. FSH. testosterone (T), prolactin, cortisol. T, and T, in plasma of mature, male white-tailed deer. Camp. Bioc,hem. Ph~~siol.16A, 37.45. Fletcher T. J. and Short R. V. (1974) Restoration of libido in castrated red deer stag (Cer1,u.s c/aphu.\) with estradioll7-beta. Natlrrc (Land.) 248, 616-617. Frankenberger Z. (1954) lnterstitialni bunky jelena (Cerru.v rlaphus L.) (The interstitial cells of the red deer). C’e.rk. MorJol. 2, 3644.
Testosterone Gimenez T., Barth D., Hoffmann B. and Karg H. (1975) Blood levels of testosterone in the roe deer (C’apreolus capreolus) in relationship to the season. Acfa endocr. (Kbh.) Suppl. 193, 59. Haigh J. C., Cates W. F., Glover G. J. and Rawlings N. C. (1984) Relationship between seasonal changes in serum testosterone concentrations, scrotal circumference and sperm morphology of male wapiti (Cervus eluphus). J. Reprod. Ferr. 70, 413418. Hertel P., Kramer M. and Neumann F. (1969) Einfluss eines Antiandrogens (Cypoteron-acetat) auf Knochenwachstum und Knochenreifung mannlicher Ratten. Arzneim.-Forsch. 19, 177771790. Jllius A. W., Haynes N. B., Lamming G. E., Howles C. M., Fairall N. and Millar R. P. (1983) Evaluation of LH-RH stimulation of testosterone as an index of reproductive status in rams and its application in wild antelope. J. Reprod. Fert. 68, 1055112. Leader-Williams N. (1979) Age related changes in the testicular and antler cycles of reindeer Rangifer tarandus. J. Reprod. Fert. 57, 117-126. Lincoln G. A. (197 1) The seasonal reproductive changes in the red deer stag (cerw elaphus). J. Zool. (Land.) 163, 1055123. McMillan J. M.. Seal U. S., Keenlyne K. D., Erickson A. W. and Jones J. E. (1974) Annual testosterone rhythm in adult white-tailed deer (Odocoileus virginianus borealis). Endocrinology 94, 1034 1040. Mirarchi R. E., Howland B. E., Scanlon P. F., Kirkpatrick R. L. and Sanford L. M. (1978) Seasonal variation in plasma LH, FSH, prolactin and testosterone concentrations in adult male white-tailed deer. Can. J. 2001. 56, 121-127. Peet M. J. and Lincoln G. A. (1977) Blockade of episodic gonadotrophic secretion by Immobilon in ovariectomized ewes. J. Reprod. Fert. 50, 977100. Pelletier J. and Ortavant R. (1975) Photoperiodic control of LH release in the ram. I. Influence of increasing and decreasing light photoperiods. Acta endow. (Kbh) 78, 435441. Schams D. and Barth D. (1982) Annual profiles of reproductive hormones in peripheral plasma of the male roe deer (Capreolus capreolus). J. Reprod. Fert. 66, 463468. Sempere A. J. and Boissin J. (1981) Relationship between antler development and plasma androgen concentrations in adult roe deer (Capreolus capreolus). J. Reprod. Fert. 62, 49953.
and LH in deer
351
Sempere A. J. and Lacroix A. (1982) Temporal and seasonal relationship between LH, testosterone and antlers in fawn and adult male roe deer (Capreolus capreolus L.), a longitudinal study from birth to four years of age. Acta endocr. 99, 295-301. Sernia C., Hinds L. and Tyndale-Biscoe C. H. (1980) Progesterone metabolism during embryonic diapause in the tammar wallaby, Macropus eugenii. J. Reprod. Fert. 60, 139-147. Short R. V. and Mann T. (1966) The sexual cycle of a seasonally breeding mammal, the roebuck (Capreolus capreolus). J. Reprod. Fert. 12, 3377351. Stelmasiak T. and Galloway D. B. (1977) A priming effect of LH-RH on the pituitary in rams. J. Reprod. Fer/. 51, 491493. Suttie J. M., Lincoln G. A. and Kay R. N. B. (1984) Endocrine control of antler growth in red deer stags. J. Reprod. Ferr. 71, 7-15. Van Mourik S. (1986a) The expression and relevance of dominance in farmed rusa deer (Ceruus rusa rimorensis). Appl. anim. beh. Sci. (in press). Van Mourik S. (1986b) Maternal behaviour and reproductive performance of farmed rusa deer (Cerws rusa timorensis). Appl. anim. beh. Sci. (in press). Van Mourik S. and Stelmasiak T. (1984a) The use of Rompun for immobilizing rusa deer (Cercus rusa timorensis). Vet. Med. Rev. 2, 163-167. Van Mourik S. and Stelmasiak T. (1984b) Adrenal response to ACTH stimulation in rusa deer (Ceruus rusa limorensis). Camp. Biochem. Physiol. 79A, 581-584. Van Mourik S. and Stelmasiak T. (1985) Seasonal variation . in plasma prolactin concentrations in adult male rusa deer (Ceruus rusa rimorensis). Camp. Biochem. Physiol. 82, 323-327. West N. 0. and Nordan H. C. (1976) Hormonal regulation of reproduction and the antler cycle in the male Columbian black-tailed deer (Odocoileus hemionus columbianus) Part I. Seasonal changes in the histology of the reproductive organs, serum testosterone, sperm production, and the antler cycle. Can. J. Zool. 54, 1617.-1636. Whitehead P. E. and McEwan E. H. (1973) Seasonal variation in plasma testosterone concentration of reindeer and caribou. Can. J. 2001. 51, 651658. Whitehead P. E. and West N. 0. (1977) Metabolic clearance and production rates of testosterone at different times of the year in male caribou and reindeer. Can. J. Zool. 55, 1692-1697.
Printed
in Great
0300-9629/X6 $3.00 + 0.00 ‘\c 1986 Pergamon Press Ltd
1986
Britain
SEASONAL VARIATION IN PLASMA TESTOSTERONE, LUTEINIZING HORMONE CONCENTRATIONS AND LH-RH RESPONSIVENESS IN MATURE, MALE RUSA DEER (CERF’US RUSA ZXl4OREAWS) SIMONE VAN *University Telephone: Laboratory,
MOURIK,* T. STELMAsrAKt and K. H. OUTCH~
of Melbourne, School of Agriculture and Forestry, Parkville, Victoria 3052, Australia. (03) 345 1844; TDepartment of Agriculture and Rural Affairs, Attwood Veterinary Research Westmeadows, Victoria 3047; fDepartment of Chemical Pathology, Prince Henry Hospital, Melbourne, Victoria 3004, Australia (Received 7 June 1985)
Plasma testosterone and luteinizing hormone (LH) concentrations in immobilized or yarded rusa stags (Cerous rusa rimorensis) were investigated over a two-year period. 2. Testosterone concentrations showed a minor elevation in autumn (May) and reached maximal levels in late winter-early spring (August) coinciding with the rut. 3. Luteinizing hormone in plasma was only detectable from January to May. 4. Maximal responsiveness of the pituitary-gonadal axis to LH-RH stimulation was recorded in August. 5. The combination of FentazK (fentanylcitrate and azaperone) and Rompun’x (xylazine hydrochloride) for immobilizing deer influences hypothalamic function. Abstract-l.
INTRODUCTION The presence of antlers in cervids and mechanism of the process of their seasonal growth have been a subject of a substantial research effort over the years. Because of the social function of antlers (Bubenik, 1Y83) antlers develop in close relationship with the sexual cycle of each particular species. As long as 2000 years ago Aristotle realized that antler development was related to testicular function “If stags be mutilated when, by reason of their age, they have as yet not horns, they never grow horns at all; if they be mutilated when they have horns, the horns remain unchanged in size and the animal does not loose them”. More recently the development of specific radioimmunoassays has resulted in information on the annual concentrations of several hormones for different cervid species. This has provided insight into the antler growth process and reproductive seasonality. Testosterone (T) and luteinizing hormone (LH) concentrations have been reported for white-tailed deer (Odocoileus oirginiunus), red deer (Ceruus eluphus), roe deer (Cupreolus capreolus) and reindeer (Rangijer tarandus) by Bubenik et al. (1977, 1982, 1983), McMillan et al. (1974), Mirarchi et al. (1978). Haigh et al. (1984), Lincoln (1971), Suttie et al. (1984), Barth et al. (1976). Schams and Barth (1982), Sempere et al. (1981, 1982), Short and Mann (1966), Leader-Williams (1979) and Whitehead and McEwan (1973), respectively. These boreal species all show a distinct annual pattern in T and LH concentrations relative to a short, well-defined rutting and antler growth period. In contrast, rusa deer (Cercus rusa timorensis) exhibit an extended rutting period from late winter (July) to the start of summer (October) as well as different
antler growth pattern. The velvet shedding takes several weeks and velvet pieces might still be attached to the antlers when they are cast round December. We have therefore investigated the following aspects in mature, male rusa deer: (1) Annual pattern of testosterone (T) and luteinizing hormone (LH) concentrations; (2) Pituitary responsiveness to luteinizing hormone releasing hormone stimulation (LH-RH) at different times during the year. (3) The effect of cyproterone-acetate on T concentrations and subsequent rutting activities. MATERIALS
AND METHODS
Animals All blood samples were collected from mature, deep kept under farmed conditions in Victoria, (38”42’S, 146”6’E).
male rusa Australia
Blood sample collection Blood samples (10 ml) from non-immobilized deer were a heparinized vacutainer following collected into venepuncture as the animal was manually restrained in the yard. Drugs used for immobilization of deer were: Fentaz” (Ethnor Pty Ltd, North Ryde, NSW; fentanylcitrate, 10 mg/ml, azaperone, 80 mg/ml), Rompun ’ (Bayer AC. Leverkusen, West Germany; xylazine hydrochloride) Ketalar% (Parke Davis Pty Ltd, Caringbah, NSW; ketamine
hydrochloride) (Van Mourik and Stelmasiak. 1984a). Samples from immobilized deer were collected into heparinized test tubes following venepuncture during velveting procedures, or after cannulation of the jugular vein (Van Mourik and Stelmasiak, 1984b). Treatments Cyproterone acetate (Schering AG, Berlin, A biweekly dose of 3 ml of solution
many).
347
West Gercontaining
Testosterone and LH in deer with Fentaz” and Rompun” than in those which were immobilized with Rompun” and Ketalar” mixture. LH was only detectable in plasma samples collected in this time of the year. If the drugs suppress hormone concentrations this observation indicates that LH definitely peaks between January-April. Testosterone concentrations in plasma collected in
349
May from immobilized stags were also the highest, compared to the previous months, indicating a peak. The high concentrations of LH druing decreasing day-length are in agreement with results for other deer species mentioned and seasonally breeding mammals such as sheep (Pelletier and Ortavant, 1975). Endocrine and histological studies in white-tailed
6
T -(
;
10
I
(0% B
=
4
B
Sample (a)
4
April.
Sample (b)
May.
- 130
60
I
\
90
0
B
4
(c)
Fig. 2. Plasma
12
Sample
June.
T and LH concentrations
B
4
Sample
(d)
12
August
(means k SD) in stags (N = 5) after administration LH-RH.
of 500 ng
3.50
SIMONEVANMOURIK,T. STELMASIAK and K. M. OUTCH
deer, roe deer, black-tailed deer and red deer indicate that the seasonal rhythm does not have just one peak. Bubenik et al. (1979) showed that two peaks of oestradiol-17b occur in mature white-tailed deer, one in October-November just before the rut and the other in April-May at the beginning of antler growth. Bubenik et al. (1982) also demonstrated two peaks in gonadotrophin activity in white-tailed deer. First an LH peak in July and an FSH peak in September and subsequently a synchronous increase in March, although there was no rise in serum testosterone related to the March rise in gonadotrophin levels. In roe deer an annual biphasic elevation in testosterone concentration has been reported (Gimenez et al., 1975; Barth et al., 1976; Schams and Barth, 1982). West and Nordan (1976) noted that spermatogenic activity in black-tailed deer was at a peak in November and declined sharply through January-March. However, in May spermatogenic activity was observed in nearly all tubules, but had declined again by July. Frankenberger (1953) observed changes in the proportion and absolute number of testicular interstitial cells in red deer shot throughout the year. Peaks occurred before the rut in late August followed by a decline and another peak in January. Despite the occurrence of an elevation of testosterone concentrations in May (autumn), the major rutting period for rusa stags starts at the end of July and extends to October. The May T rise stimulates male sexual behaviour, expressed as “fleshmen” towards hinds with calves at foot (Van Mourik, 1986a, b). This can be considered as “autumn-rutting” in contrast to spring-time rutting behaviour which has been reported in red deer (Fletcher and Short, 1974) and caribou (Whitehead and McEwan, 1973). Occasional births are recorded well out of season, indicating that a rusa stag population is capable of breeding nearly the whole year round. This is in agreement with Bubenik ef al. (1982) who stated that maximal concentrations of T is not required for the process of spermatogenesis and shedding of velvet in white-tailed deer. However, their statement that maximal concentrations of T are essential for the manifestation of behavioural rut cannot be confirmed with our observations on rusa stags. The absence of a detectable annual pattern in basal concentration of LH and T in pretreatment samples in immobilized stags for LH-RH responsiveness tests, indicates an inhibition of hypothalamic secretion by Fentaz’-RompunH mixture. It might be assumed that the drugs inhibited LH-RH, LH and subsequently testosterone secretion. The inhibitory effect of Fentaz”-Rompun” mixture on hypothalamus provides a convenient model for study of seasonal changes in responsiveness of pituitarytesticular axis to LH-RH. The maximal responsiveness, expressed in testosterone concentrations was recorded in August, coinciding with the rut. No alterations in testosterone concentrations were noticed in May after LH-RH administration, but LH concentrations reached highly elevated levels in contrast to other times of the year. Whitehead and West (1977) determined the metabolic clearance and production rates of testosterone at different times of the year in male caribou and reindeer. They found lower production rates and
higher clearance rates during the non-reproductive season than during mid-rut. In the tammar wallaby (Macropus eugenii) low progesterone concentrations were also associated with low production rates and high metabolic clearance rates (Sernia et al., 1980). The time lapse from injection of immobilizing drugs to collection of first pre-treatment sample was around 40 min. Although testosterone concentrations fluctuate over the year with maximum levels during the rut, the concentration in plasma samples for baseline levels from immobilized stags was consistently below 5 nmol/l. This would indicate a higher metabolic clearance rate during the reproductive season in contrast with the above mentioned species, The antler growth of rusa deer starts in January and shedding of the velvet commences in May. The antlers are mineralized in August and cast in December. Administration of cyproterone acetate (CA) resulted in a rapid drop in testosterone concentrations to undetectable levels. The decrease in testosterone concentration reactivated the growth of the velvet antlers and in addition caused the abolishment of rutting behaviour. The unusual nature of the sexual cycle of rusa deer (long-day breeder) as compared with other cervidae (short-day breeders) further illustrates the differences in sensitivity to photoperiodic stimulation (Van Mourik and Stelmasiak, 1985) and indicates that the endogenous mechanisms regulating the gonadal functions may differ between species, Acknowledgements-The authors thank Willow Ware Australia Pty Ltd for use of animals. Bayer AC for their generous gift of Rompun”, Ethnor Pty Ltd for donation of Fentaz”, Hoechst AG for provision of LH-RH, Schering A.G. for cyproterone acetate and Dr P. Taylor, Mr D. Piggin, Mr M. Vella for assistance in blood sample collection and MS M. Katsis for typing the manuscript. This study was supported by the Reserve Bank of Australia and Commonwealth Special Research Grant.
REFERENCES Barth D., Gimenez T.. Hoffman B. and Karg H. (1976) Testosteronkonzentrationen im peripheren Blut beim Rehbock (Capreolus capreolus). Z. Jagdbviss. 22, I34 148. Bubenik A. B. (1983) The behavioral aspects of antlerogenesis. In Antler Deoelopment in Ceruidae (Edited by Brown R. D.). Caesar Kleberg Wildlife Research Institute, Kingsville, Texas. Bubenik G. A., Bubenik A. B., Brown G. M. and Wilson D. A. (I 977) Sexual stimulation and variations of plasma testosterone in normal, antiandrogen and antiestrogentreated white-tailed deer (Odocoileus virginianus) during the annual cycle. In XIIIth Congress of Game Biologists, Atlanta, Georgia, USA. pp. 377 386. Bubenik G. A., Morris _I. M., Schams D. and Claus A. (1982) Photoperiodicity and circannual levels of LH, FSH and testosterone in normal and castrated male, whitetailed deer. Can. J. PhysioI. Pharmacol. 60, 788-793. Bubenik G. A.. Bubenik A. B.. Schams D. and Leatherland J. F. (1983) Circadian and circannual rhythms of LH. FSH. testosterone (T), prolactin, cortisol. T, and T, in plasma of mature, male white-tailed deer. Camp. Bioc,hem. Ph~~siol.16A, 37.45. Fletcher T. J. and Short R. V. (1974) Restoration of libido in castrated red deer stag (Cer1,u.s c/aphu.\) with estradioll7-beta. Natlrrc (Land.) 248, 616-617. Frankenberger Z. (1954) lnterstitialni bunky jelena (Cerru.v rlaphus L.) (The interstitial cells of the red deer). C’e.rk. MorJol. 2, 3644.
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