Asynchronous breeding in red brocket deer (Mazama americana): seasonal changes in male reproductive characteristics, seminal parameters, androgen levels, and antler cycle

Dancing to a different tune: changing reproductive seasonality in an introduced chital deer population

Male and female reproductive behaviour is typically synchronised. In species such as those in the family Cervidae, reproductive timing is often cued by photoperiod, although in females, it can be dependent on body condition. When a species is introduced to a novel environment, the environment changes, or responses of the sexes to such cues differ, asynchronous reproductive behaviour between males and females may occur. We investigated the seasonality of reproductive behaviour in introduced chital deer in northern Queensland by examining male antler phase in relation to female conception rates. We then analysed the influence of different variables likely to affect the timing of male and female reproductive physiology. The lowest percentage of chital in hard antler in any 1 month in this study was 35% (Fig. 1), but the average value was closer to 50%, thus there was a seasonal peak in antler phase linked with photoperiod. Females conceived at any time of year, but were strongly influenced by the amount of rainfall 3 months prior to conception. This resulted in varying conception peaks year-to-year that often did not correspond to the male’s peak in hard antler. In this system, a proportion of males and females were physiologically and behaviourally ready to mate at any time of the year. We predict that differences in the timing of the peaks between the males and females will lead to increased reproductive skew (variation in reproductive success among individual males). This pattern may select for different mating strategies or physiological mechanisms to increase reproductive success.Fig. 1

Effect of dietary fiber on fecal androgens levels: An experimental analysis in brown brocket deer (Mazama gouazoubira)

Non-invasive endocrinology is an important tool for animal conservation, but its success depends on many factors (e.g. adequate hormonal extraction, diet, antibody used in the assay). Dietary fiber is one of the main sources that can lead to erroneous interpretation of the endocrine status provided by EIA analysis. This study aimed to evaluate the dietary fiber effect on the fecal androgen metabolites (FAM) detection, on the daily defecation rate and fecal production, as well as to analyze the gastrointestinal passage and retention time of the experimental diets. Eight brown brocket deer (Mazama gouazoubira) males were randomly assigned to two groups and submitted to both isocaloric and isoproteic experimental diets for 10 days, in a crossover system: low fiber percentage feed (LF, 7% fiber) and high fiber percentage feed (HF, 19% fiber). Such groups were alternated in the middle of this period, with an interval of 10 days between them. In addition, there was a five-day adaptation phase at the beginning of each diet. Fecal collection for FAM measurement was performed during 10 days of treatment, whereas,the defecation rate and fecal production were performed every two hours, for 6 days. The mean FAM level in the HF group was 5038.0 ± 1529.1 ng/g, while for LF, 2178.7 ± 824.9 ng/g (p < 0.05). The mean HF fecal production was 182.6 ± 36.2 g DM/day and 117.5 ± 12.6 g DM/day for LF (p < 0.05). There were no differences in terms of mean defecation rate, passage, and retention times between groups. The results suggest that dietary fiber affects the FAM detection, and this should be taken into consideration before conducting experiments using fecal samples as a source of reproductive hormones profiling.

Spermatogenesis in a vulnerable South American cervid, dwarf red brocket (Mazama rufina)

The brocket deer (Genus Mazama) is a highly diverse cervid group distributed from Mexico to Argentina, with a downward population trend. However, literature on the basic reproductive biology of the genus is scarce. This work aimed to study biometric, histological and stereological aspects of the testes of Dwarf Red Brocket (Mazama rufina). Testes from free-ranging adult brockets (n = 3) were retrieved from necropsies. Testes were histologically processed. From histological images, several stereological parameters were estimated, and seminiferous epithelium cycle morphology was described. Testes volumes were between 8.2 and 18.4 ml and weights from 8.3 to 19.4 g. Gonadosomatic index (% paired-testes weight to body weight) went from 0.17 to 0.64. The tubular cross-sectional diameter was 179.8 ± 2.8 µm. Estimated volume densities for parenchyma and interstitium were 78.8% and 21.2% respectively. There were (in millions/ml) 96.0 ± 13.1 germ cells and 37.7 ± 6.0 somatic cells. Specific cell densities were (all expressed in millions/ml) as follows: spermatogonia 13.1 ± 4.2; primary spermatocytes 43.1 ± 5.0; round spermatids 36.8 ± 8.0 (lower density near the caudal pole, p < 0.01); sustentacular (Sertoli) cells 16.8 ± 4.1 and interstitial endocrine (Leydig) cells 17.4 ± 3.4. Sertoli cell index (germ cells per Sertoli cell) was 6.72. Eight stages of the cycle were described, and frequencies estimated, resembling those of goats. M. rufina adult testis anatomy is similar to that of other cervids and domestic ruminants, with an apparently lower spermatogenic efficiency. This work is a first approximation to the physiology of the testis of M. rufina. Basic knowledge of the reproductive physiology of vulnerable species may allow biotechnological approaches for the restitution of animal populations.

Evaluation of potential reproductive seasonality in brown brocket deer (Mazama gouazoubira) bucks

Photoperiod is the main cue that controls seasonal reproduction in deer from temperate regions, like secretion of testosterone by the testis, neck enlargement, and testis development. However, little is known about its effect on the reproduction of tropical deer species. This research aimed to assess the potential seasonality of the brown brocket deer (Mazama gouazoubira) by melatonin treatment. Reproductive parameters such as testicular volume, neck circumference, and semen quality were evaluated from day 0 to 90, and fecal androgen metabolites (FAM) from day -28 to 91. Melatonin treatment was administered from day 0 to 60. In total, seven individuals were used in the study. Four animals were allocated to the treated group (TG) and three to the control group (CG). The neck circumference and some seminal parameters did not show a significant difference between CG and TG and along the experimental period. High FAM levels were observed for the TG on days 7, 14, 21, 35, 84, and 91 (p < 0.05). The mean testicular volume was reduced from day 0 to 30 (p < 0.05) and from day 0 to 90 (p < 0.05), with no increase in the mean testicular volume from day 30 to 60 (p > 0.05). Sperm motility was the highest on day 60 compared with day 0 (p < 0.05). Although not statistically different, membrane integrity and major defects tended to be higher and lower, respectively, in the TG compared with the CG. For these parameters, the incremental change (%) per individual showed that males from the TG tended to have a higher percentage during the melatonin treatment, hence melatonin might affect these seminal characteristics. These findings suggest that exogenous melatonin might enhance FAM levels and sperm motility.