Fecal Testosterone Concentrations Research Articles

Characterization of basal seminal traits and semen cryopreservation in Canada lynx (Lynx canadensis)

Little is known about the reproductive biology of the Canada lynx; virtually no data are available describing seminal parameters in this species and sperm cryopreservation studies have not been performed. Our aims were to 1) evaluate effectiveness of two semen collection methods: urethral catheterization (UC) and electroejaculation (EEJ); 2) characterize basal seminal traits throughout the breeding season; 3) compare effectiveness of semen cryopreservation using TEST egg yolk (TEY) or soy lecithin-based (SOY) media; and, 4) evaluate the ability of preserved Canada lynx sperm to fertilize domestic cat in vitro matured oocytes by heterologous in vitro fertilization. Testicular volume averaged 4.5±1.0 cm3. A significant relationship was found between animal body weight and testes volume (P<0.02), as well as for testicular volume and sperm counts per ejaculate (P<0.01). Fecal testosterone concentrations and sperm production were correlated (P<0.01). Electroejaculation was more reliable than UC for sperm collection (8.8 and 1.5 × 106 sperm, respectively; P<0.01). The percentage of sperm with normal morphology was greater in EEJ (29 ± 11 %) than in UC (18 ± 9 %) (P<0.05) samples and primary sperm structural abnormalities were more frequent in UC than EEJ samples (P<0.01). Overall, sperm quality was low in most males throughout the breeding season, but consistent with previous findings in the Lynx genus. Sperm production averaged 10.8 × 106 sperm/ejaculate with 45 % motility; 29 % normal morphology and 69 % acrosome integrity. Motility and acrosome integrity post-thaw declined over time, but were similar between spermatozoa cryopreserved in TEY and SOY media (P > 0.05). Cleavage rates did not differ between TEY (29 ± 17 %) and SOY (27 ± 14 %) and mean numbers of sperm bound to the zona pellucida was similar (20 sperm, TEY vs. 18 sperm, SOY), indicating that both extenders equally preserved the function of Canada lynx sperm for semen banking purposes. Our findings provide zoos and population managers with valuable information about normative reproductive traits in this species, establishing comparative benchmarks for assessing the reproductive potential of specific males recommended for breeding.

Effects of photoperiod on morphology and function in testis and epididymis of Cricetulus barabensis.

Photoperiod regulates the seasonal reproductive rhythms of mammals by influencing the development and function of sexual organs; however, the underlying mechanism remains unclear. We examined the morphology and functioning of the main sex organs of striped dwarf hamsters (Cricetulus barabensis) under different photoperiods (short daylight [SD], moderate daylight [MD], and long daylight [LD]) and further investigated the underlying molecular mechanisms. There was an inverse correlation between blood melatonin levels and photoperiod in the order SD > MD > LD. Decreases in body and tissue weights were observed under SD, whereas testis and epididymis weights between MD and LD were comparable. The diameters of the spermatogenic tubules, thickness of the spermatogenic epithelium, and the number of spermatogonia and Sertoli cells decreased under SD, whereas the serum-luteinizing hormone, follicle-stimulating hormone, and fecal testosterone concentrations decreased under LD. In SD, bax/bcl2 protein expression increased in the testes and decreased in the epididymides, whereas LC3II/LC3I remained unchanged in the testes and increased in the epididymides compared with the MD group. In LD, bax/bcl2 and LC3II/LC3I protein expression levels were unchanged in the testes but were decreased in the epididymides. In SD and LD, adenosine triphosphate synthase and citrate synthase protein expression levels were unchanged in the testes but were decreased in the epididymides. Drp1 and Mff protein expression increased in the testes and decreased in the epididymides. Overall, different regulatory mechanisms in the testis and epididymis led to degeneration under SD and maintenance under LD, preferentially protecting mitochondrial function in the testis by regulating mitochondrial fission.

Puberty, ovarian cycle, pregnancy, and postpartum ovulation in captive Sichuan golden monkeys (Rhinopithecus roxellana) based on changes in urinary and fecal gonadal steroid metabolites

The purpose of this study was to evaluate the reproductive status and clarify the reproductive physiology of captive Sichuan golden monkeys. The concentrations of urinary estradiol-3-glucuronide (E2G) and pregnanediol-glucuronide (PdG) or fecal estradiol-17β (E2) and PdG in two females, and fecal testosterone concentrations in a male, were measured continuously using enzyme immunoassays. On the basis of these hormone profiles, the follicular phase, luteal phase, and ovarian cycle were calculated to be 14.7 ± 4.8, 10.4 ± 2.8, and 25.1 ± 3.3 days, respectively. The first ovulation (puberty) in a female monkey was observed at 5.1 years old, and the first pregnancy was diagnosed at 6.4 years old. For the first 2 months of pregnancy (204 days), fecal E2 and PdG maintained constant high values and then increased until parturition. These profiles were similar to urinary E2G and PdG changes. During the last trimester of a twin pregnancy, fecal PdG was up to approximately three times higher compared with a single pregnancy. Therefore, fecal PdG levels in late pregnancy may be effective for the detection of a twin pregnancy. The first postpartum ovulation occurred 66 (fetal death and artificial rearing), 143 (fetal death), and 189 (natural suckling) days after parturition. The anovulation period of the natural suckling case was longer than the others. Conception and postpartum ovulation were detected between September and January. Fecal testosterone levels of the male were correlated with the fecal E2 level of the nonpregnancy period in exhibited together female. Our results reported that urinary (E2G and PdG) and fecal (E2 and PdG) hormone measurement is effective for monitoring the reproductive status, thereby expanding knowledge of the reproductive endocrinology of this endangered species.

Disrupting effect of androgens in postnatal female domestic cats

To test the hypothesis that in domestic cats, postnatal androgens induce sterility, the aims of this study were to describe the reproductive effects and the clinical safety of a postnatal administration of a long term release androgen in this species. Thirteen newborn littermate female kittens were randomly assigned to one of the following treatment groups within the first 24h of birth: testosterone enanthate 12.5mg sc (TE; n=8) or Placebo (PL; n=5). The animals were subsequently assessed for fecal sexual hormones until puberty was attained and subsequently when matings occurred. After 21 days, ovulation and gestation were diagnosed. All queens were subsequently ovario-hysterectomized. Fecal testosterone concentrations differed between the treatment groups throughout the study period (P<0.05) being greater during the first 2 postnatal weeks in those of the TE group (P<0.01). Fecal estradiol was not affected by treatment (P>0.1). While all the females were receptive during the pubertal estrus (P>0.1), two TE (2/8) compared with all (5/5) females of the PL group had ovulations (P<0.05). Only one (1/2) compared with three (3/5) of the queens of the TE and PL groups, respectively became pregnant. All kittens of the TE group had transient clitoral enlargement. Anovulatory TE-treated cats had no corpus luteum, and a significant diminution of the endometrial glands as well as of the height of the uterine epithelium. It is concluded that, in domestic cats, a single postnatal supra-physiological dose of testosterone caused a large proportion of queens to be anovulatory and there were also histological endometrial abnormalities that also occurred with this treatment that were accompanied by mild and transient side effects.

TESTOSTERONE AND CORTISOL LEVEL IN FECAL JAVA DEER (Cervus russa timorensis Mul. &amp; Schl 1844) MALE IN CAPTIVITY BUNDER GUNUNG KIDUL YOGYAKARTA

&lt;p&gt;Common reasons for monitoring hormone concentrations in domestic or wild animals, include breeding management, pregnancy diagnosis, stress assessment, and to diagnosed of endocrine illness. The research goal was to develop non invasive analytical techniques of hormone in Java deer (Cervus russa timorensis Mul. &amp;amp; Schl 1844). The non-invasive methods involve the collection of feces, urine, or even saliva in order to measure the metabolites hormones of interest. Samples obtained from either method are most often analyzed with radioimmunoassay (RIA) or enzyme immunoassay (EIA) technology. Both collection and assay methods have advantages and disadvantages. Choice of method depends on the tractability of the species or individual animal in question and the type of question that the data is expected to answer. We are researching basic questions regarding reproductive endocrinology of male Cervus russa timorensis Mul. &amp;amp; Schl 1844. Understanding C timorensis reproductive physiology will help us better address reproductive challenges in both captive and free-ranging populations. Fecal testosterone and cortisol concentrations were measured in captive male C timorensis. As much as five adult male deer were separated into separate cages. Fecal samples were collected in the morning and evening for 30 days. Sample processed through lyophilization stage, pulverization, solvent extraction with methanol and centrifugation to obtain the supernatant for EIA analysis. EIA test results indicated that content of both testosterone and cortisol could be detected, although the levels were still low. This data show that there is a metabolite in-activism in the fecal. With these results through fecal hormone measurement method (non-invasive) it is possible to be developed for observation and research on the reproductive status of the deer.&lt;/p&gt;&lt;p&gt;&lt;br /&gt;&lt;strong&gt;Keywords&lt;/strong&gt;: Non-invasive, Testosterone, Cortisol, Java deer.&lt;/p&gt;

Excreta-mediated olfactory communication in Konik stallions: A preliminary study

Abstract The aim of this preliminary study was to assess whether adult stallions differentiate their olfactory and marking behavior toward the excreta of potential rivals depending on their age, libido, hormonal status, and the season of the year. Five Konik stallions were individually exposed to own and each others' feces in a round pen during 8 observation sessions from February to November. The youngest stallion's feces were sniffed for a significantly longer period and were defecated or urinated on significantly more often, in addition to receiving more flehmen reactions. The stallion with the highest libido sniffed feces significantly longer. Alien feces were sniffed significantly longer than an individual's own feces, except for the youngest stallion. Overmarking of existing feces with urine was significantly less frequent than through defecation and was observed only outside of the reproductive season. Defecations on feces were most frequent after the peak of the reproductive season. A stallion's libido rank correlated perfectly with the number of defecations performed on alien feces (r s = 1.000). Sniffing of feces occurred for a longer time before the peak of the reproductive season, and flehmen was performed primarily on spots around feces and significantly more often in the peak of the reproductive season (May). Fecal testosterone and androstenedione concentrations were significantly higher in April and May but did not differ significantly between stallions. Testosterone concentrations were positively correlated with duration of performed sniffing feces and negatively correlated with the duration the individual's feces were sniffed. It was for the first time shown which individual social information could be mediated by defecation and sniffing feces in adult stallions.

Permanent contact with females increases testosterone and improves fresh semen traits in pampas deer (Ozotoceros bezoarticus) males

Socio-sexual signals can stimulate neuroendocrinal control of reproduction. The aim of this work was to test the hypothesis that permanent and close contact with females stimulates testosterone production and enhances fresh seminal characteristics of pampas deer males. Five adult males (group CF) were established in a paddock in five breeding groups each comprising one stag and between five and ten hinds. Six adult males (group IS) were held in another paddock without any direct contact with females. Fecal testosterone concentrations were determined for each male, weekly, from October to May. Semen was collected by electro-ejaculation and evaluated before and after the addition of diluents [November: Fructose-Tris-Glycine with 20% egg yolk (FTG); April: Andromed]. Males in contact with females from mid-December to February exhibited significantly (P=0.04) greater concentrations of testosterone than those without. In November, CF males ejaculated semen of significantly (P=0.03) higher quality, with a significantly (P=0.02) greater proportion of progressive motile spermatozoa than IS males. After dilution with FTG, semen from the CF males had greater quality (P=0.04), a greater percentage of motile spermatozoa (P=0.04), spermatozoa with progressive motility (P=0.01), and spermatozoa with intact acrosomes (P=0.03). Semen from CF males also had lower fractions of spermatozoa with damaged acrosomes (P=0.04). In April, there were no significant differences in semen properties between the two groups. After the addition of extender, semen from CF males had a greater percentage of spermatozoa with damaged acrosomes (P=0.04). It is concluded that contact with females stimulates reproductive patterns of male pampas deer, resulting in better fresh semen characteristics before rutting and higher testosterone concentrations during the rut.

Sexual maturation in the sumatran rhinoceros (Dicerorhinus sumatrensis)

To help save the Sumatran rhino from extinction, the captive breeding program must capitalize on each rhino's reproductive lifespan. Doing so requires knowing when calves are sexually mature. The goal of this study was to monitor physiological changes associated with sexual maturation in two captive born calves (one male and one female) to determine the approximate age of maturity for both sexes of this species. Fecal testosterone metabolites were monitored in the male calf from 6 months to 7 years of age, and fecal pregnane metabolites were measured in the female calf from 6 months to 5.5 years of age. In addition, rectal ultrasonography was employed to monitor changes in ovarian activity from 2 to 5.5 years of age. The male calf's fecal testosterone concentrations reached levels comparable to those detected in samples from adult males when he was 6-6.5 years of age. The first pre-ovulatory sized follicle was observed on the ovaries of the female calf when she was 4.75 years old, but fecal pregnane metabolite concentrations only reached maximum mean concentrations and variability when she was 5-5.5 years of age. Results from this study indicate that male and female Sumatran rhino calves are sexually mature at 6-6.5 and 5-5.5 years of age, respectively.

Factors Influencing Annual Fecal Testosterone Metabolite Profiles in Captive Male Polar Bears (Ursus maritimus)

The objectives of this study were to assess the effects of season, breeding activity, age and latitude on fecal testosterone metabolite concentrations in captive, adult male polar bears (Ursus maritimus). Fourteen polar bears from 13 North American zoos were monitored for 12-36 months, producing 25-year-long testosterone profiles. Results indicated that testosterone was significantly higher during the breeding season (early January through the end of May) compared with the non-breeding season with the highest concentrations excreted from early January through late March. Variations in excretion patterns were observed among individuals and also between years within an individual, with testosterone peaks closely associated with breeding activity. Results indicate that fecal testosterone concentrations are influenced by season, breeding activity and age, but not by latitude. This is the first report describing longitudinal fecal testosterone metabolite concentrations in individual adult male polar bears.

Patterns of fecal hormones in a fenced population of white‐tailed deer

AbstractAnalysis of voided feces has become a popular method of monitoring physiological parameters of many wildlife species. During the breeding seasons of 2006–2007 and 2007–2008, we collected fecal samples to determine concentrations of fecal glucocorticoid (FG) and fecal testosterone (FT) metabolites in a fenced population of white‐tailed deer (Odocoileus virginianus). The purpose of the study was to determine how concentrations of FG and FT metabolites fluctuated throughout the breeding season, whether there was a difference between males and females, and whether there was a relationship between the two hormones. FG and FT metabolites of males peaked during the rut, while female glucocorticoid levels remained relatively stable throughout the breeding season. We also observed a significant positive correlation between FG and FT metabolites. During the pre‐rut and rut, males that exhibit high testosterone also had elevated glucocorticoid metabolite concentrations, but in the post‐rut there was no relationship between FT and FG concentrations. We hypothesize that the effect of testosterone on glucocorticoid secretion is partially a result of testosterone‐induced behavior, and not strictly a physiological link between the two hormones. © 2012 The Wildlife Society.

Sex, stress and social status: Patterns in fecal testosterone and glucocorticoid metabolites in male Ethiopian wolves

Ethiopian wolves, Canis simensis, live in large multi-male family packs, where males are philopatric and do not disperse. Within a pack, mating and breeding is largely monopolized by the dominant male and female, although extra-pack copulations are common, and subordinate males may sire pups in neighboring packs. Regardless of paternity, all males in a pack help rear the pups. We non-invasively studied patterns in fecal testosterone and glucocorticoid metabolite concentrations using radioimmunoassays of fecal samples collected from nine wild male Ethiopian wolves between August 2007 and February 2008. We tested the predictions of the Challenge Hypothesis, namely that fecal testosterone metabolite concentrations would be higher during the annual mating season, which is the portion of the reproductive cycle when mating and increased aggression typically occur, and lower when there were pups in the pack for which to care. Contrary to the predictions of the Challenge Hypothesis, we did not detect patterns in fecal testosterone metabolite concentrations associated with reproductive stage during our study period. Similarly, we found no patterns associated with reproductive stage in male fecal glucocorticoid metabolite concentrations. Dominant males had higher average fecal testosterone and glucocorticoid metabolite concentrations than did subordinates, which may be related to higher rates of aggression and mate guarding in dominant males of group-living canids, a pattern also reported in African wild dogs, Lycaon pictus.

Testosterone and tusks: maturation and seasonal reproductive patterns of live, free-ranging male dugongs (Dugong dugon) in a subtropical population

Knowledge of male reproductive status and activity in free-ranging animals is vital to understanding reproductive patterns and population dynamics. Until now, almost all information regarding reproductive behavior of the dugong, a cryptic marine mammal, has relied on post-mortem examination. We examined the relationships between body length, tusk eruption (secondary sexual characteristic), seasonality, and group association on fecal testosterone metabolite concentrations in 322 free-ranging dugongs (159 males, 163 females) in subtropical Moreton Bay, Australia. Fecal testosterone concentrations demonstrated biologically meaningful differences in testicular activity between sexes and across reproductive/age classes, and were correlated with circulating concentrations in serum. Male dugongs have a pre-reproductive period that persists until a body length of 240 cm is achieved. Puberty apparently occurs between 240 and 260 cm body length when fecal testosterone levels increase fourfold (>500 ng/g) over juvenile levels, and is associated with tusk eruption. However, social maturity may be delayed until male dugongs are larger than 260 cm with well-developed tusks. In mature males, the lowest (<500 ng/g) fecal testosterone concentrations occur in the austral autumn months with maximal concentrations in September-October, coincident with the onset of a spring mating season. During spring, solitary mature males had fecal testosterone concentrations double those of mature males sampled within groups, potentially suggesting a mating strategy involving roving of reproductively active males. This study demonstrates that single-point physiological data from individuals across a population have value as indicators of reproductive processes. Our approach provides an efficacious non-lethal method for the census of reproductive status and seasonality in live male dugongs.

The reproductive endocrinology and behavior of Vancouver Island marmot (Marmota vancouverensis)

The Vancouver Island marmot (Marmota vancouverensis; VIM) is one of North America's most endangered species with fewer than 150 individuals remaining in the wild. A captive breeding program was established across four facilities in Canada as an insurance population and source of animals for reintroduction to the wild. The purpose of this study was to gather information about the basic reproductive biology and behavior of this species, which is essential to improve captive breeding programs. Regular fecal samples were obtained from adult female (n = 14) and male (n = 10) marmots, 2 years of age and older, over 1-3 breeding seasons (2-3 months duration posthibernation) for steroid hormone analysis. Enzyme immunoassays were validated for quantifying fecal testosterone metabolite concentrations for males, and fecal estrogen and progesterone metabolite concentrations for females. Results indicated that fecal progesterone metabolite concentrations can be used to monitor ovulation and pregnancy. Behavioral monitoring through infrared video surveillance was conducted in four breeding pairs over a 2-year period (n = 7 behavioral profiles). Breeding behaviors correlated strongly with changes in reproductive endocrine profiles. A high frequency of play behavior or "wrestling" was observed in conjunction with breeding activity before an elevation in progesterone metabolite concentrations. Impending parturition was associated with increased aggression and exclusion of the male from the maternal nestbox as well as an increase in nesting activity. Observational data combined with hormonal analysis suggest that female VIMs are induced ovulators and that multiple breeding attempts may be required for ovulation and conception. Gestation appears to be approximately 34 days from peak breeding activity (32 days from estimated ovulation). Fecal testosterone concentrations suggest that testicular activity is seasonal with the reproductive activity occurring immediately posthibernation. Monitoring breeding behavior is a useful means of indicating estrus, conception and pregnancy, which can also be supported by the hormonal analysis of daily fecal samples of individual animals.

Social factors increase fecal testosterone levels in wild male gray-cheeked mangabeys ( Lophocebus albigena)

Testosterone can be expected to play a significant role in mediating behavior and life history in social animals, but the number of species with data from the wild is still too small to make generalizations. We investigated the influence of social factors (social status, aggression, and reproductive females) and environmental variation (rainfall and temperature) on fecal testosterone concentrations in wild male gray-cheeked mangabeys ( Lophocebus albigena) living in five groups in Kibale National Park, Uganda. This species is phylogenetically closely related to baboons, but is arboreal, with multi-male, multi-female groups rarely exceeding 20 individuals. We analyzed 358 fecal samples from 21 adult males. We found that the highest-ranking males had the highest testosterone concentrations while immigrant males had the lowest testosterone concentrations. Aggression was not correlated with testosterone levels. The presence of females with sexual swellings at their most tumescent stage increased testosterone concentrations in all males. Finally, individuals tended to have lower testosterone when the temperature was higher.

Variation in Fecal Testosterone Hormone Concentration with Season and Harem Size in Misaki Feral Horses

On Misaki peninsula, Japan, fecal samples were collected from 14 Misaki stallions at monthly intervals for 12 consecutive months. The fecal testosterone concentration was measured by radioimmunoassay. We examined monthly fecal testosterone hormone patterns and the relationship between fecal testosterone concentration and breeding season and later harem size. Marked monthly variations in fecal testosterone concentration were observed. The fecal testosterone concentration began rising in March; the highest mean monthly concentration, 2.87 +/- 0.18 ng/g, was found in April, and the level remained elevated until the end of August and thereafter decreased. A significant correlation was found between the fecal testosterone concentrations and harem size in both the breeding and non-breeding season among the 14 stallions. It is therefore possible that the testosterone levels in feces, instead of blood, correlate very well with harem size in Misaki stallions. Our findings emphasized that the fecal testosterone concentration can be a powerful indicator for monitoring of endocrine status in wild stallions.

Seasonal influence on fecal immunoreactive testosterone concentrations of male Formosan black bears (Ursus thibetanus formosanus)

We investigated the effect of seasonal influence and geographic location on the testosterone concentrations of three adult male Formosan black bears kept at a Low Altitude Experimental Station, simulating natural breeding conditions. Estimations of fecal testosterone for males 1, 2, and 3 were made during January to October 2000, April 2001 to December 2003, and April 2002 to December 2003, respectively, using non-invasive enzyme-linked immunosorbent assays. Results indicated that fecal immunoreactive testosterone recrudesces after winter and ceases after summer. Mating behaviors were observed both before and after the fecal immunoreactive testosterone peak of March–May. In addition, fecal immunoreactive testosterone concentrations were significantly (p < 0.01) higher during January to June than from July to December. As expected, levels corresponded to the longer and earlier breeding seasons of subtropical zones. Formosan black bears appear to be seasonal breeders who breed primarily in spring, synchronized with sunlight and ambient temperature. The aim of this study was to determine if testosterone concentrations respond to seasonality thereby reflecting bear mating demands. Baseline parameters established in this study will help to evaluate endocrine information applicable for guidelines in future management and preservation of Formosan black bears in the field.

Seminal and endocrine characteristics of male Pallas' Cats (Otocolobus manul) maintained under artificial lighting with simulated natural photoperiods

Pallas' cats (Otocolobus manul) have a pronounced reproductive seasonality controlled by photoperiod. Previous studies of reproduction in captive Pallas' cats exposed to natural light showed a breeding season of December-April. This study evaluated the impact of artificial lighting timed to simulate natural photoperiods on male reproductive seasonality of four Pallas' cats housed indoors. Semen evaluation, blood collection, and body weight measurements were conducted every 1-2 months from November 2000-June 2001. Fecal samples were collected from each male twice weekly to assess testosterone and corticoid concentrations. Mean values for reproductive traits (sperm attributes, testicular volume) were highest from February-April, the defined breeding season. Fecal testosterone concentrations were highest from mid-January to mid-March. Male Pallas' cats managed indoors under simulated photoperiods experienced a delayed onset of the breeding season by 1-2 months and a decreased length of the breeding season. Over the course of the study, fecal corticoid concentrations did not seem to differ among seasons. Although mating attempts during this study were unsuccessful, subsequent pairings of male and female Pallas' cats in the same research colony during the 2002 and 2003 breeding seasons produced viable offspring. These results suggest that male Pallas' cats, housed indoors under simulated photoperiods, exhibit distinct reproductive cyclic patterns, characterized by a delayed and truncated breeding season. Adrenocortical activity varied among individuals, but did not adversely affect reproductive parameters. Housing Pallas' cats indoors under simulated photoperiods may represent a viable strategy for maintaining breeding success while limiting disease exposure. Zoo Biol 0:1-13, 2007. (c) 2007 Wiley-Liss, Inc.

Investigations on reproductive physiology in the male Eurasian lynx (Lynx lynx)

This study characterized (in vivo) morphological and functional parameters of reproductive organs of adult male lynx ( n = 3) prior to, during, and after the breeding season ( n = 3). Size and morphology of the reproductive tract were monitored by transcutaneous (testes) and transrectal (accessory sex glands) ultrasonography. Semen was collected by electroejaculation. Ejaculate volume, sperm number, motility, and morphology of spermatozoa as well as testosterone concentrations in blood serum and feces were evaluated. The testes and prostate had seasonal changes in size and echotexture. The mean (±S.D.) maximum and minimum testicular volume were 2.8 ± 0.8 cm 3 and 1.5 ± 0.3 cm 3, respectively. Fecal testosterone concentrations were highest in February (1240 ± 393 ng/g feces), with a second increase in May (971 ± 202 ng/g feces), but concentrations were lowest in January (481 ± 52.9 ng/g feces). Ejaculate volume, total sperm number and percentage of motile, and intact spermatozoa were maximal in March (the middle of the breeding season). In one of the eight litters, multiple paternity was proven; however, in the remaining seven litters, all 16 cubs were sired by the same male. This particular male had the most developed and active testes and best semen quality, which may be important for sperm competition.

The seasonal fertility of North American bison ( Bison bison) bulls

The objective of this study was to determine the presence and magnitude of seasonal fluctuations in semen quality and other reproductive indices in bison bulls. Testicles from 288 commercially slaughtered bison bulls were collected monthly over a 1-year period. Carcass and testicle weight were determined and measurements of seminiferous tubule lumen, diameter, and epithelial thickness were made. Sperm cell morphology and defects were described and quantified using epididymal semen from each testicle. Twenty-one Plains ( Bison bison bison) and Wood bison ( Bison bison athabascae) breeding bulls, averaging 6.0 years of age (range 2.5–8.0), from three farms were selected for semen collection and evaluation on the basis of producer co-operation. Semen was collected by electro-ejaculation on four seasonal occasions during a 12-month period. Ejaculate quality was judged on the basis of volume, density, gross and individual motility, morphology, live/dead ratio, and concentration. Sperm cell morphologies were evaluated microscopically and classified according to criteria used for bovine semen. Fecal testosterone was measured at each semen collection using a commercial competitive binding radioimmunoassay. There was an increase in carcass weights over the study period and testis weights were moderately correlated ( r = 0.44) with carcass weights. However, mean testes weights were heavier ( P < 0.05) in the summer than in winter, spring, or fall periods. There were no differences in the proportion of normal and abnormal epididymal sperm between seasons but there were seasonal changes in the testicular parenchyma. Seminiferous tubule and lumen diameter, and epithelial thickness were greatest ( P < 0.05) in summer. Live bulls gained weight between April and November, but lost weight over the winter. Normal sperm cell percentages as well as individual sperm cell motility in electro-ejaculated sperm samples were higher ( P < 0.05) at the pre-breeding collection relative to other collections, but no change in sperm cell concentrations occurred over the study period. Fecal testosterone concentrations were highest at the pre-breeding period (June) but decreased ( P < 0.05) in each subsequent collection to reach their lowest levels in the April. While many changes in seen characteristics were not significant, overall results indicate the presence of some reproductive seasonality and increased testicular capacity in the summer breeding season. Bulls showing marginal semen quality in the winter but otherwise carrying desirable genetic traits may warrant another evaluation in late spring prior to being culled from a breeding program.

The onset of puberty in North American bison ( Bison bison) bulls

Prepubertal testicular development was evaluated in young North American bison ( Bison bison) bulls over a 12 months period, by following various parameters of semen quality intended to measure sexual maturity level. The study goals were to characterize bison male reproductive development and to define the age and onset of puberty. Semen was collected by electro-ejaculation from 12 bulls once a month for a period of 12 months, from 13 through 24 months of age. Volume, density, gross motility, individual motility, morphology, live/dead ratio, and concentration were used to judge the quality of the ejaculates. Abnormal sperm were classified into categories according to descriptions used for bovine evaluations and guidelines created by the Western Canadian Association of Bovine Practitioners were used for determining satisfactory semen quality. Minimums of 60% progressive motility and 70% normal sperm cells identified samples as satisfactory. Puberty was defined as the point in testicular development where an ejaculate contains a minimum of 50 × 10 6 sperm cells, showing at least 10% progressive motility. Fecal samples collected from bulls prior to electro-ejaculation for testosterone determination by a commercial testosterone specific antibody radioimmunoassay showed no significant changes in mean fecal testosterone concentrations over time. Changes in mean body weights over the study period were calculated, the average body weight at 13 and 24 months of age were 263 ± 18.6 and 475 ± 52.2 kg, respectively. Under these experimental conditions, age was determined to be the most significant factor in determining the onset of puberty. On average, bulls reached puberty at 16.5 ± 2.5 months. There was a significant increase in the number of normal sperm with increasing bull age as well as significant decreases in proximal cytoplasmic droplets and head defects, but no significant changes in midpiece and principal piece defects. There were significant increases with age in individual progressive motility, gross motility, concentration, density, and volume but not in the percent of live sperm. Bison bulls used for breeding should be capable of passing a breeding soundness evaluation by 24 months of age. The commercial bison industry semen tests, and possibly rejects, many developmentally incomplete bulls between 19 and 21 months of age. We suggest that these may actually be developing normally and should not be hastily discarded; it may be worth testing again at 24 months.