Seasonal changes in plasma leptin concentration related to antler cycle in Iberian red deer stags

The aim of this study is to describe the leptin cycle in male Iberian red deer (Cervus elaphus hispanicus) and relate it to antler and testosterone cycles. An additional aim is to assess the relationship between the plasma leptin concentration during antlers’ growth and their final size. Therefore, blood from 21 Iberian red deer males was sampled monthly to analyse leptin and testosterone. At the same time the deer were weighed and their body condition was assessed. The length of antlers was measured every 2 weeks and, after casting, their final length and perimeters were taken. Leptin showed a seasonal cycle, with a peak in June that decreased as testosterone increased. Low values were observed in autumn, winter and early spring. The relationship observed between leptin and body mass or body condition score was different in spring, when plasma testosterone concentration is low, than in autumn, when testosterone increases. Leptin peak amplitude was positively related to final antler size. In conclusion, the relationship between leptin and body mass and body condition score changes through the year, possibly due to the influence of androgens and photoperiod. There was a positive relationship between plasma concentration of leptin during antler growth and final antler length.     

Age-related changes in the testicular and antler cycles of reindeer, Rangifer tarandus

A total of 111 male reindeer of various ages was shot in all months of the year to study the relationship between the seasonal changes in testicular activity and the antler cycle. From the changes in testis weight, seminiferous tubular tissue area and plasma testosterone values and the occurrence of spermatogenesis, it is concluded that calves attain physiological puberty in their first year, during which they also complete an antler cycle. The amplitude of the cyclical change in testis weight and plasma testosterone values increases with age and can be correlated with the earlier onset of events in the spermatogenic and antler cycles of older animals. The duration of the spermatogenic and testosterone cycles of reindeer is short, and is inversely related to the long period spent without antlers. It is suggested that testosterone strongly influences the antler cycle of reindeer males.     

梅花鹿(Cervus nippon hortulorum)茸角生长发育各阶段血浆睾酮、雌二醇的含量变化

本文用放射免疫测定法对3个不同年龄组的雄性东北梅花鹿茸角生长发育各阶段外周血中的睾酮、雌二醇含量进行了测定。茸期两种激素差异很大,睾酮含量低,雌二醇高,骨化期二者增高很快。对这两种激素含量的变化与茸角发育各阶段的关系进行了讨论。认为只有在二种激素同时增加时,鹿角才能骨化。     

Growth of the first antler in Iberian red deer (<Emphasis Type="Italic">Cervus elaphus hispanicus</Emphasis>)

In this study, we describe the process of pedicle and first antler growth in Iberian red deer (Cervus elaphus hispanicus) and document relationships among body development, maternal milk supply and composition, and maternal weight on the length of first antlers. Antler length of 53 males of Iberian red deer was measured every 2 weeks from birth to 20 months of age. Deer weight, age, and the date of occurrence of the major events during the antler growth cycle were also recorded. The first evidence of pedicle development occurred when the animals were 38.0 ± 0.6 weeks old and weighed 60.7 ± 0.9 kg. Antler cleaning took place at a mean age of 63.8 ± 0.7 weeks and a mean weight of 91.5 ± 1.8 kg. The antler growth period lasted 16.7 ± 0.4 weeks, and the cleaning period lasted 5.1 ± 0.4 weeks. First antler growth followed a sigmoid curve, reaching a final length of 38.3 ± 1.0 cm. Antler length was positively correlated with body weight during the antler growth cycle. Additionally, the final length of the first antler was related to total milk yield, date of antler growth initiation, body weight at 6 months of age, and the antler growth time interval.     

Lactation under induced five-month delay reproduction in Iberian red deer (Cervus elaphus hispanicus)

In Iberian deer, calf birth date affects both milk production and composition, as well as the weight change of hind during lactation and calf growth. This study examines a five-month induced delay in calving (autumn group) in a group of 19 Iberian hinds compared to a group of 13 standard calving hinds (spring group). Fertility in the autumn group was half that of the spring one. From the former, a further two calves out of six died before or soon after birth. Successfully lactating hinds showed a greater concentration in protein, fat and lactose (P < 0.001), but did not differ from spring group in total milk yield, calf gain or weight change of hinds during lactation. However, after correcting for the greater calf or hind body weight at calving of the autumn group, this group showed lower values for these variables than the spring group. Results show that at least in Iberian deer, counter-season reproduction is possible, and that the effects on lactation variables are similar to those of a natural delay in calving.     

Seasonal changes in fecal testosterone concentrations and their relationship to the reproductive behavior, antler cycle and grouping patterns in free-ranging male Pampas deer (Ozotoceros bezoarticus bezoarticus)

The purpose of this study was to validate noninvasive endocrine monitoring techniques for Pampas deer and to evaluate seasonal changes in testicular steroidogenic activity and their correlation to reproductive behavior, antler cycle and group size. Thus, fecal samples, behavioral data and observations of antler status were collected at monthly intervals during 1 year from free-ranging Pampas deer stags (three radio-collared individuals and 15 random individuals) living in Emas National Park, Brazil (18 degrees S latitude). Fecal steroids were extracted using 80% methanol and steroid concentrations were quantified by a commercial enzyme immunoassay (EIA). Fecal testosterone concentrations peaked in December-January (summer), March (early autumn) and in August-September (winter-spring), with minimal values from April-July. Reproductive behavior had two peaks, the first in December-January, characterized by predominately anogenital sniffing, flehmen, urine sniffing, chasing and mounting behavior, and the second peak in July-September (behavior primarily related to gland marking). There were significant correlations between fecal testosterone and reproductive behavior (r=0.490), and between fecal testosterone and antler phases (r=0.239). Antler casting and regrowth occurred under low testosterone concentrations, whereas velvet shedding was associated with high concentrations of testosterone. We inferred that Pampas deer stags exhibited a seasonal cycle that modulated sexual behavior and the antler cycle, and we concluded that fecal steroid analysis was a practical and reliable non-invasive method for the evaluation of the endocrine status of free-ranging Pampas deer.     

麋鹿鹿角脱落、群主更替、产仔的年节律及其环境影响因子

本文在2014—2016年三个冬季(12月—翌年2月)收集了北京南海子麋鹿苑半散放麋鹿自然脱落的角,并观察和记录了2015—2017年发情期(5—9月)群主更替和2016—2018年产仔期(3—7月)麋鹿幼仔出生情况,结合2014—2018年年平均气温、季平均气温、月平均气温、年降雨量、雨季开始时间、种群密度等环境因子,对鹿角脱落、群主更替、产仔等繁殖特征的年节律及其环境影响因子进行了研究。结果表明：1)麋鹿鹿角脱落、群主更替、产仔的年节律均存在年际差异。2)鹿角脱落时间为12月开始,1月下旬或2月上旬结束。3)发情期为5月下旬或6月上旬开始,9月上旬结束;2015—2017年发情期时间有延长的趋势。4)产仔期为3月中旬或4月中旬开始,5月下旬或7月下旬结束。5)麋鹿鹿角脱落、群主更替、产仔的年节律存在明显的同步关系,其中鹿角脱落开始时间、鹿角脱落高峰期、鹿角脱落结束时间、第一次发情期开始时间、群主更替高峰期、产仔期开始时间、产仔高峰期、产仔期结束时间与前一年度比较均出现同步提前的现象。6)鹿角脱落年节律存在随着12月平均气温升高而提前的现象;产仔期开始时间和产仔高峰期存在随着前一年9月平均气温的升高而提前的现象。7)鹿角脱落年节律表现出随着年降雨量的增多而提前的现象;第一次发情期开始时间、群主更替高峰期的年节律表现出随着前一年度年降雨量的增多而提前的现象。8)麋鹿鹿角脱落、群主更替、产仔的年节律均不存在随着种群密度升高或降低而提前或延迟的现象。麋鹿繁殖特征的年节律是一个复杂的过程,受气候、营养、种群密度、纬度等环境因子的影响。     

Hormonal and behavioral changes at puberty in the squirrel monkey

Developmental changes in the reproductive behavior and physiology of 9 male and 15 female juvenile squirrel monkeys were evaluated in a 20-month study. Plasma levels of gonadal steroids remained relatively low for this species until most animals reached puberty between 2.5 and 3 years of age. Longitudinal assessment of plasma progesterone levels indicated that the onset of ovarian cycles tended to be synchronized between females although the 5 heaviest females began to cycle earlier than the rest. The heavier females reached puberty at a time which was appropriate to their birth in the wild, whereas most of the remaining females conceived 6 months later during a second period of reproductive activity that coincided with the laboratory mating season. Pubescent males underwent their first seasonal elevation in plasma testosterone levels during the second period and its onset was synchronized across all males. Thus, even in the absence of adults, pubertal processes in the squirrel monkey were strongly influenced by the seasonal breeding pattern. In addition, behavioral observations revealed that social maturation closely parallels reproductive ability in females, whereas males enter a protracted subadult stage after puberty.     

A study of seasonally delayed puberty in the male hare, Lepus Europaeus.

The brown hare, Lepus europaeus, has a mating season which extends from January to September. Adult males exhibit pronounced seasonal changes in the reproductive tract which are associated with changes in LH secretion. Maximum plasma levels of immunoreactive LH occur between March and June and minimal levels in the autumn non-mating period from September to December; this seasonal cycle in gonadotrophin output is reflected by the appropriate changes in the secretion of testosterone from the testes and in the activity of the accessory sex glands. Juvenile animals reach puberty only during the adult mating season, and the age of puberty thus varies with the date of birth. Males born before May reach puberty and become fertile at 3 months of age, while those born from May to July grow to a mature body size during the autumn non-mating season but puberty is delayed for several months. Since some animals experiencing delayed puberty were found to have elevated plasma levels of LH and testosterone, it is concluded that puberty is not completely suppresed by the environmental effects of the autumn, but that the developmental process is prolonged, resulting in the juveniles being synchronized with the adults in their reproductive activity.     

Short-term variations in plasma LH and testosterone in bull calves from birth to 1 year of age.

LH and testosterone levels in bull calves were studied in the plasma samples collected sequentially at 15-min intervals every month during the first year of life. An episodic pattern of LH release occurred after birth and the frequency and magnitude of the LH peaks increased up to 4 months of age and decreased thereafter. A testicular response was not observed before this age. It is suggested that this episodic LH activity is responsible for the testicular development which then initiates puberty.     

Effects of accelerating growth on the onset of puberty in male mice

Sexual maturation was evaluated in male mice subjected to prenatal and preweaning overnutrition induced by reduction of litter size in embryonic and post-natal life. From birth to adulthood body weight was higher in overfed males than in controls. Plasma and testicular testosterone levels followed a similar pattern in normally fed and overfed males. Adult gonadotrophin levels were attained at 30 (FSH) and 40 (LH) days in controls and as soon as 20 days in overfed males. First fertile matings occurred at the same age in both groups. Overnourished males attained puberty when weighing considerably more than controls (34.7 +/- 0.4 vs. 29.4 +/- 0.3 g). The 30-day-old overfed males, which have attained the critical pubertal body weight of controls, were sexually immature. The data showed that in male mice puberty does not seem to be triggered by the attainment of a critical body weight.     

Endocrine control of antler growth in red deer stags

Observations of body weight, testis size, antler status, plasma testosterone and prolactin were made on 12 red deer stags during their first 2 years of life. Six of the stags were fed to appetite throughout the study (Group A) and 6 were fed a 70% restricted diet during each winter (Group B). In addition 6 of the stags , 3 from each group, were studied in more detail; LH and testosterone were measured either after a single injection of LH-RH or in samples taken at frequent intervals over a period of 8 or 24 h. During the study the stags became sexually mature, developed first their pedicles and then antlers and showed at least one complete cycle of casting and regrowth of the antlers . The stags in Group A developed their testes and pedicles about 2 months earlier than did those in Group B. Pedicle initiation was associated with increasing plasma testosterone levels in response to changes in LH secretion, and antler development occurred when testosterone levels were low or decreasing. Cleaning of the velvet was associated with high levels of plasma testosterone. Antler casting occurred when plasma testosterone concentrations were low or undetectable and prolactin levels were high or increasing. The relationship between LH and testosterone varied during the study; in spring when the testes and antlers were growing, relatively high levels of LH were associated with only small peaks of testosterone, yet in summer, when antler growth was complete and the antlers were clean of velvet, low LH concentrations were associated with large peaks of testosterone.     

Juvenile-to-Adult Antler Development in White-Tailed Deer in South Texas

Abstract: Past studies using penned deer provide conflicting results on the age when reliable predictions about antler growth potential in white-tailed deer (Odocoileus virginianus) can be made. We captured wild whitetail males via aerial net gun on 12 ranches in 5 counties in south Texas, USA, from 1999 to 2007 to determine if a reliable juvenile-to-adult relationship in antler development existed. We individually marked and released captured animals at the trap site after we took antler and body measurements. We recaptured marked animals as possible in subsequent years or until we obtained final measurements after legal harvest. Amount of growth in the first set of antlers in whitetail males was a poor predictor of antler growth at maturity. By 4.5 years of age there were no differences (P > 0.05) in antler measurements regardless of the amount of development of the first set of antlers at 1.5 years. We concluded culling of yearling males based on number of antler points would have little positive effect on overall antler quality in future years.     

Inhibin B,follicle stimulating hormone,luteinizing hormone and testosterone during childhood and puberty in males: changes in serum concentrations in relation to age and stage of puberty

Inhibin B is a gonadal dimeric polypeptide hormone that regulates synthesis and secretion of follicle stimulating hormone (FSH) in a negative feedback loop. The aim of the present study was to determine changes in serum inhibin B, gonadotropins and testosterone concentrations during childhood and puberty in males. We studied the relationship between circulating inhibin B, gonadotropins and testosterone in serum of healthy boys during the first two years of life and then in pubertal development. Using a recently developed two-side enzyme-linked immunosorbent assay (ELISA), inhibin B levels were measured in the serum of 78 healthy boys divided into eleven age groups from birth to the end of pubertal development. In addition, serum levels of gonadotropins and testosterone were measured. Serum inhibin B, gonadotropins and testosterone increased during the first months of postnatal life. A peak in serum inhibin B and gonadotropins concentrations was observed around 3-4 months of age. There was a significant positive correlation between serum inhibin B and gonadotropins and testosterone levels during the first 2 years of life. After this early increase, serum inhibin B, gonadotropins and testosterone levels decreased significantly and remained low until puberty followed by an increase beginning with the onset of puberty. Serum levels of inhibin B reached a peak at stage G3 of puberty. Around midpuberty, inhibin B lost its positive correlation with luteinizing hormone (LH) and testosterone from early puberty, and developed a strong negative correlation with FSH, which persisted into adulthood. We conclude that inhibin B plays a key role in the regulation of the hypothalamic-pituitary-gonadal hormonal axis during male childhood and pubertal development. Inhibin B is a direct marker of the presence and function of Sertoli cells and appears to reflect testicular function in boys.     

Effect of antiandrogen cyproterone acetate on the development of the antler cycle in Southern pudu (Pudu puda)

The antler cycle of pudu is similar to other cervids, but unlike most boreal deer, male Southern pudu (Pudu puda) exhibits two seasonal peaks of LH and testosterone. In that respect, pudu is similar to roe deer. Whereas the antler cycle in some deer species, such as roe deer or white-tailed deer, is very sensitive to variation of testosterone, in other cervids, such as fallow deer or reindeer, a blockade of androgens with cyproterone acetate (CA) has little or no effect on the timing of the antler casting. In order to test the sensitivity of pudu antlers to variations of androgens, CA (administered 2x weekly at 50 mg/buck) was injected intramuscularly for 3 weeks in 5 adult male pudu, starting February 19 (late summer). Four other males of similar age served as controls. The experiment was performed at the University of Concepcion, Chile, latitude 36.6 degreeS. Blood samples were taken once a week between January 19 and April 3. In CA-treated bucks, the antlers were cast approximately 3 weeks after the initiation of CA treatment and a new antler growth began almost immediately. The antlers reached about 5 cm in length, before ceasing to grow at the end of April, when they became mineralized and were subsequently polished. CA had no effect on the already declining levels of LH. Plasma levels of testosterone in controls increased from February 15, whereas in CA-treated bucks remained depresses until March 21. It is concluded that similarly to white-tailed deer, the antler cycle of Southern pudu is very sensitive to manipulation of androgen levels.     

Antler length of yearling red deer is determined by population density, weather and early life-history

In red deer, yearling antler length is a largely nutrition-mediated phenotypic character, and is therefore sometimes used as an indirect estimate of range quality and population condition. However, the parameters affecting yearling antler length have been little studied. We analyse the contributions of density, weather and maternal effects on yearling antler length of 581 individual stags born 1970-1996 on the Isle of Rum (Scotland). We show that antler length is a good measure of yearling condition: the probability of overwinter survival in yearlings that developed antlers was 3 times higher than for yearlings that did not develop antlers, and yearling antler length was correlated with the number of antler points the following year. Between years, variation in yearling antler length was best explained by variation in red deer density and June temperature at 12 months of age. Both of these variables were negatively correlated with antler length, and most likely this effect is due to changes in nutrient availability. Population density affects biomass availability for the individual, while low temperatures in early summer prolong the availability of high forage quality. At the individual level, antler length increased with birth weight and decreased with birth date, reflecting the persistent and pervasive influence of conditions in early life.     

Concentrations of insulin-like growth factor-I in adult male white-tailed deer (Odocoileus virginianus): associations with serum testosterone, morphometrics and age during and after the breeding season

Our understanding of insulin-like growth factor-I (IGF-I) in cervids has been limited mostly to its effects on antler development in red deer (Cervus elaphus), roe deer (Capreolus capreolus), fallow deer (Dama dama), and pudu (Pudu puda). Although IGF-I has been found to play a critical role in reproductive function of other mammals, its role in reproduction of deer is unknown. The objectives of the present study were to determine if serum levels of IGF-I change during the breeding season, assess whether age influences serum IGF-I, compare levels of IGF-I measured during and following the breeding season, and determine if IGF-I is associated with body and antler characteristics in free-ranging adult, male white-tailed deer (Odocoileus virginianus). We collected serum and morphometric data from hunter-harvested and captured white-tailed deer to investigate these objectives. Mean level of serum IGF-I during the breeding season was 63.6 ng/ml and was greatest in deer between 2.5 and 5.5 years old (57.4-79.9 ng/ml). Levels of serum IGF-I decreased by approximately 40% as the breeding season progressed, but levels were less in deer following the breeding season (34.6 ng/ml). Both body and antler size were associated positively with IGF-I when controlling for age. Serum testosterone was also associated positively with IGF-I. Levels of serum testosterone during the breeding season generally increased with age from 4.82 (1.5 years old) to 18.79 ng/dl (5.5 years old), but decreased thereafter. These data suggest that IGF-I may be an important hormone in breeding, male white-tailed deer.     

Influence of season on sexual development in heifers: age at puberty as related to growth and serum concentrations of gonadotropins, prolactin, thyroxine and progesterone

An experiment was done to test the hypothesis that seasonal changes in environment during the first and second 6 months of life influence age at puberty in heifers. Twenty-eight Angus X Holstein heifers, born in March (M) or September (S), were reared under natural conditions until 6 months of age. From 6 to 12 months of age, heifers were reared in environmental chambers programmed to simulate seasonal changes in temperature and photoperiod characteristic of spring, summer and early autumn (Sp-F chamber) or autumn, winter and early spring (F-Sp chamber). S were younger (P less than 0.06) at puberty than M, and Sp-F were younger (P less than 0.08) than F-Sp for both M and S. Mean ages at puberty were 295 for S, Sp-F; 319 for S, F-Sp; 321 for M, Sp-F and 346 days for M, F-Sp. Average daily gain (ADG) between 6 and 9 months of age [1.03 kg/day (S) vs. 0.91 kg/day (M)] and mean concentrations of serum luteinizing hormone (LH) between 6 and 7 months of age [3.45 ng/ml (S) vs. 0.47 ng/ml (M)] were greater (P less than 0.01) for S than M, suggesting an association between these traits and date of birth effects on age at puberty. Differences in these traits did not seem to be involved in the chamber effect on age at puberty, since ADG from 6-9 months of age was greater (P less than 0.05) for F-Sp heifers and chamber did not generally affect LH concentrations. Serum concentrations of follicle-stimulating hormone (FSH) were not significantly influenced by month of birth or chamber, but concentrations tended to decrease with age. Serum concentrations of thyroxine (T4) were higher in M than S at 6 months of age (7.8 micrograms/dl vs. 6.3 micrograms/dl) but not at other times, and chamber did not have a significant affect. Prolactin (Prl) concentrations paralleled patterns of temperature and day length and did not appear to be related to age. Although cattle are not seasonal breeders, these results demonstrate that season of birth and season of attainment of puberty influence age at puberty in heifers. Season may have influenced age at puberty by affecting serum concentrations of LH or Prl, or growth rate.     

Effect of reproductive rest on the subsequent breeding in Iberian red deer hinds (Cervus elaphus hispanicus)

The objective of this study was to examine the effects of reproductive rest during the preceding year on subsequent breeding in captive Iberian hinds. To achieve this, influences were assessed on hind weight at mating, precalving and postcalving weight, hind body condition at mating, hind weight gain during gestation, hind weight loss at calving, total milk yield and calf birth weight during the following breeding season. Sex ratio was examined according to hind age class (sub-adults or adults), precise age, body condition and weight at mating, and reproductive rest. One hundred and twenty seven gestations and their subsequent lactations were analyzed in pluriparous Iberian red deer (Cervus elaphus hispanicus) kept in captivity for two years. Sixty four of these gestations (50.4%) took place after no gestation during the preceding year.Hinds that did not gestate the preceding year were heavier at mating and after calving, gained less weight during gestation, and their body condition at mating was better than those hinds that had gestated. Also, calves from hinds that had reproductive rest the preceding year were heavier at birth than the others. Nevertheless, the probability of bearing a male was greater with increasing age, but not with reproductive rest or any other variable. Total milk yield was positively affected by hind postcalving weight and hind age at mating, but not by reproductive rest.In conclusion, reproductive effort during the preceding breeding influenced the subsequent gestation, having an effect on the following variables: hind weight and body condition at mating, hind weight gain during gestation, postcalving weight, and calf birth weight.     

Cell proliferation and hormonal changes during postnatal development of the testis in the pig

Histometrical evaluation of the testis was performed in 36 Piau pigs from birth to 16 mo of age to investigate Sertoli cell, Leydig cell, and germ cell proliferation. In addition, blood samples were taken in seven animals from 1 wk of age to adulthood to measure plasma levels of FSH and testosterone. Sertoli cell proliferation in pigs shows two distinct phases. The first occurs between birth and 1 mo of age, when the number of Sertoli cells per testis increases approximately sixfold. The second occurs between 3 and 4 mo of age, or just before puberty, which occurs between 4 to 5 mo of age, when Sertoli cells almost double their numbers per testis. The periods of Sertoli cell proliferation were concomitant with high FSH plasma levels and prominent elongation in the length of seminiferous cord/tubule per testis. Leydig cell volume increased markedly from birth to 1 mo of age and just before puberty. In general, during the first 5 mo after birth, Leydig cell volume growth showed a similar pattern as that observed for testosterone plasma levels. Also, the proliferation of Leydig cells per testis before puberty showed a pattern similar to that observed for Sertoli cells. However, Leydig cell number per testis increased up to 16 mo of age. Substantial changes in Leydig cell size were also observed after the pubertal period. From birth to 4 mo of age, germ cells proliferated continuously, increasing their number approximately two- to fourfold at each monthly interval. A dramatic increase in germ cells per cross-section of seminiferous tubule was observed from 4 to 5 mo of age; their number per tubule cross-section stabilized after 8 mo. To our knowledge, this is the first longitudinal study reporting the pattern of Sertoli cell, germ cell, and Leydig cell proliferative activity in pigs from birth to adulthood and the first study to correlate these events with plasma levels of FSH and testosterone.