Reproductive characterization of male muntjak, muntiacus muntjak muntjak: study of anatomy, testosterone metabolite profile, and spermatogenesis during antler growth periods

Abstract

Muntjaks (Muntiacus muntjak muntjak) are belonging to Cervidae which distributed in Java Island and Southern part of Sumatera. Muntjaks have been protected by Indonesian Government since 1999. In order to support breeding program of the species and to avoid from extinction, several activities in this study were conducted. Therefore, the objective of this study was to investigate the reproductive capacity of male muntjaks in captivity. Anatomical procedure and histological preparation of reproductive organ (testis, ductus epididymidis, accessory sex glands, and penis) from an adult male muntjak (♂#1) in hard antler period was carried out to collect data of their morphology and histology structure. Immunoreactive testosterone (iT) level of fecal samples was measured by the enzymeimmunoassay method using testosterone assay (Möstl) from two adult male muntjaks with individual code as ♂#2 and ♂#3. Furthermore, core needle biopsy and electroejaculation methods were applied for obtained testicular tissues and semen for study spermatogenesis. The entire samples were collected in hard antler (RK), casting (C), and velvet antler (RV) periods with different sampling frequency. The result showed that in general, the anatomy of reproductive organ in male muntjak was somewhat similar with other small ruminant included Cervids (ram and goat, rusa deer, pampas deer, and reeves muntjak). As dominant male, ♂#2 had sturdier and bigger hard antlers (RK1 and RK2) compare to ♂#3. The duration of antler cycle of ♂#2 was also longer (459 days) than ♂#3 (381 days) in the first antler cycle. Duration of second antler cycle of ♂#3 was longer (20.65%) than in previous cycle (485 days) Based on the hormonal data, iT level of ♂#2 was different among RK, C, and RV periods where iT level during RK 1 period was higher than C (p = 0.003) and RV (p = 0.02). In addition, iT level during RK 2 was also significantly higher than those C (p = 0.009) and RV (p = 0.06). In the first antler cycle, the pattern of T secretion in ♂#3 was slightly different if compared to the ♂#2. ♂#3 showed iT level was significantly lower in RK1 than RK2 (p = 0.0003), RK3 (p= 0.0034), C1 (p = 0.05), and C2 (p = 0.0001). However, the pattern of testosterone secretion was changed when ♂#3 in RK2 at the second of antler cycle coincided with increase of ♂#3’s age and death of ♂#2. Interestingly, iT level still detected during C and RV periods in both of muntjaks and showed a positive correlation with spermatogenesis which was proven by presence of spermatozoa in semen with significant concentration during those periods. The highest sperm concentration, however, was found in RK, and slightly decreased in C and RV. These findings provide that the specific pattern of testosterone metabolite profile that exhibited by ♂#2 and ♂#3 had closed correlation with their age, body size, antler size, and antler cycles length. In conclusion, testosterone that synthesized during an antler cycle plays a central role in continuing reproductive activities in male muntjaks. Therefore, muntjaks could provide reproductive function throughout the year of reproductive aseasonality which is similar to the reeves and formosan muntjaks.