Sperm characteristics in plains (Bison bison bison) versus wood (Bison bison athabascae) bison

The objective was to compare sperm characteristics between the two subspecies of North American bison, plains bison (Bison bison bison) and wood bison (Bison bison athabascae). Frozen-thawed ejaculated sperm from age-matched plains (n = 3) and wood (n = 2) bison were evaluated for morphometry, motility, viability, protein profile, and in vitro fertilization characteristics. Sperm morphometry and motility were assessed with computer-based systems, viability was assessed with SYBR-14 and propidium iodide, and fertilizing ability was determined using a heterologous in vitro fertilization system (using bovine oocytes). For plains versus wood bison, there were significant differences for head width (4.76 ± 0.22 vs 4.71 ± 0.19 μm; mean ± SD), head area (35.64 ± 1.91 vs 34.72 ± 2.64 μm²), head perimeter (23.61 ± 0.68 vs 23.31 ± 0.98 μm), midpiece length (14.58 ± 0.4 vs 14.36 ± 0.51 μm), midpiece width (0.81 ± 0.06 vs 0.79 ± 0.07 μm), and tail length (46.61 ± 2.15 vs 45.98 ± 2.08 μm). However, there was no significant difference in head length (overall, 9.04 ± 0.37 μm), progressive motility (41.16 ± 8.39%), or viability (41.58 ± 5.58%). Based on two-dimensional gel electrophoresis, 93 out of 113 protein spots were similar in their expression patterns. Furthermore, we inferred that differences in sperm biometry between these subspecies did not affect in vitro fertilization percentage (overall, 82.62 ± 12.13%). Based on these findings, we concluded that plains bison were an appropriate research model for developing reproductive technologies for wood bison.     

Oestrous cycle of the North American bison (Bison bison) characterized by urinary pregnanediol-3-glucuronide.

An enzyme immunoassay for urinary pregnanediol-3 alpha-glucuronide (PdG) was evaluated for the indirect measurement of progesterone metabolites during the oestrous cycle and early pregnancy of uncaptured North American bison. Comparisons between plasma progesterone and urinary PdG, dose-response parallelism between the standard curve and diluted urine samples and high-performance liquid cochromatography revealed that PdG was a primary immunoreactive urinary metabolite of progesterone in bison. Urine samples were collected directly from the soil from 29 bison cows during the August rutting season and analysed for PdG. Eight bison cows demonstrated complete oestrous cycles ranging from 19 to 26 days (mean cycle length = 23.12 +/- 0.76 days) and behavioural oestrus among four of these cows correlated with PdG nadirs. Mean PdG nadirs were 63.62 +/- 21.61 ng/mg urinary creatinine (Cr) and mean peak midluteal values were 546.01 +/- 130.73 ng/mg Cr. Seven of eight became pregnant, indicating that bison exhibit a second seasonal oestrus. Eighteen other bison cows were pregnant prior to the beginning of the study and demonstrated non-cyclic increased PdG concentrations (greater than 200 ng/mg Cr) during the 30-day course of collection. Three cows ovulated and became pregnant during the 30-day collection period and then exhibited increasing urinary PdG concentrations. This report demonstrates that ovarian function in uncaptured bison can be monitored by means of urinary PdG and that both ovulatory cycles and early pregnancy can be detected.     

Reproductive success of bison bulls (Bison bison bison) in semi-natural conditions

Sexual size dimorphism has been related to a high variance in male reproductive success. Research on American bison (Bison bison bison), a species that shows moderate sexual dimorphism, has put forward the assumption that under wild conditions the largest part of the female herd is bred by a limited number of males. Thus far, this hypothesis has never been supported by genetic data. The aim of this study is therefore to test the hypothesis of extreme male reproductive variance among bison through the determination of the reproductive success of the bulls in private herds. We analysed genetic paternity in four private herds (n=19, 33, 39 and 54) kept under semi-natural conditions. By analysing blood, hair and tissue samples, using 8-10 polymorphic microsatellites, the reproductive success of the bulls was quantified. Additional genetic data were gathered through a survey distributed among bison breeders with private herds over the world. Results show a highly differential reproductive success for bison males in private herds kept under semi-natural conditions. In each study group, a single male sires at least 70% of the calves. In the survey groups, a single male sires 81-100% of the calves. Only one survey group displayed a deviating pattern showing a more evenly distribution of paternity (28.57, 33.33 and 38.10%) among three same aged subadult males.     

Bellows, copulations, and sexual selection in bison (Bison bison)

We provide data on the timing and frequency of bellowing episodesand 261 copulations in North American bison (Bison bison) extractedfrom more than 8500 h of observation to examine Darwin's ideathat by using breeding-season vocalizations the male "endeavoursthus to charm or excite the female." Copulatory status affectedvocalization rates; after mating, the frequency of male bellowingdropped to 16.1% of precopulatory rates (p < .0001). Malesbellowed at a higher rate on days when females were in estrus(p < .025) than when they were in anestrus, but females'probability of offspring production in the next year was notcorrelated with bellowing rate. For estrous females, bellowingwas positively correlated with number of attendant males (p< .0001) and inversely related both to the number of daysindividual males had participated in the rut (p < .05) andto the date during the 6-week breeding season (p < .003).Body size also influenced bellowing rate: with other factorsheld constant, small males bellowed more than large males (p< .03). With respect to Darwin's idea that vocalizationsserve as a male display to females, (1) males bellowed neitherbefore nor after copulating when rivals were absent but (2)they bellowed both before and after copulating when rivals werepresent. Overall, these results suggest that bison bellows donot serve as advertisements to females but function as intrasexualdisplays. [Behav Ecol 1991; 2: l-6]     

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.     

Host defense function in neutrophils from the American bison (Bison bison)

Selected host defense functions of neutrophils isolated from American bison (Bison bison) were characterized and compared with those of cattle (Bos taurus). Bison neutrophils had a robust chemotactic response to both IL-8 and LTB(4), with maximal responses occurring at 10(-7) M (IL-8) and 10(-8) M (LTB(4)). The magnitude of the chemotactic response to IL-8 was similar in bison and bovine neutrophils (except at 10(-7) M IL-8, where bison had a stronger response). In response to LTB(4), bison neutrophils had a much stronger chemotaxis at both 10(-8) and 10(-7) M than did bovine cells. Production of reactive oxygen species (ROS) in response to phorbol myristate acetate (PMA) and opsonized zymosan (OpZ) was similar between bison and bovine neutrophils. However, the production of ROS in bison neutrophils stimulated with OpZ was primarily intracellular, while extracellular release of ROS was evident in bovine neutrophils stimulated with OpZ. Like bovine neutrophils, bison neutrophils did not generate a respiratory burst in response to fMLF. Granules prepared from bison neutrophils had potent direct killing action on the Gram-negative bacteria Escherichia coli but failed to kill the Gram-positive bacteria Staphylococcus aureus and, at intermediate doses, actually had a permissive effect for this bacteria. Thus, bison neutrophils have potent host defense capabilities similar in quality to those of bovine neutrophils; however, unique differences are present, which may allow bison neutrophils to respond to the distinct immunological challenges that bison encounter.     

Mycobacterium avium subspecies paratuberculosis in Bison (Bison bison) from Northern Canada

Nested polymerase chain reaction (PCR) using the Mycobacterium avium subspecies paratuberculosis (Map)-specific region, locus 251, was used as a screening tool for the detection of Map DNA in fecal samples from northern Canadian bison herds. Further characterization of positive samples (26/835) was performed because Map DNA was found without signs of disease. Strain typing, using PCR-Restriction endonucleas assay (REA), was limited to two samples but revealed that the samples corresponded to a cattle-related strain and a sheep-related strain. Sequencing of part of the IS1311 region from the two samples revealed a unique three base-pair region, which is only found within the northern Canadian bison isolates.     

DNA fingerprinting and genetic diversity of the European bison (Bison bonasus), American bison (Bison bison), and gray Ukrainian cattle (Bos taurus)

To describe genetic variability and population diversity in domesticated populations of American bison (Bison bison), aurochs (Bison bonasus), and gray Ukrainian cattle (Bos taurus) different variants of DNA fingerprinting technique (utilizing the M13 phage DNA, (TTAGGG)4 synthetic oligonucleotide, and three arbitrary primers as hybridization probes) were used. Several parameters characterizing polymorphism and genetic diversity levels in each population (species) were evaluated on the basis of the profiles obtained. Dendrograms reflecting similarities between individual animals were constructed. Genetic variability of minisatellite and telomeric markers observed in the gray Ukrainian cattle flock was higher than that in aurochs and bisons. Comparison of the intrapopulation similarity (S) and gene diversity (H) indices along with the analysis of clusters in the dendrograms showed that the relatedness between the aurochs individuals was much higher than between the individual animals in the bison and gray Ukrainian cattle flocks. Furthermore, the gray Ukrainian cattle flock was represented by more distant relatives than the bison flock. It is suggested that reduced genetic variability and the appearance of deviant genotype observed in the two bison lines under selection, resulted from close inbreeding and the founder effect. The diagnostic value and efficacy of utilization of different molecular markers for estimation of genetic diversity and relatedness in domesticated animal populations is discussed.     

Seasonal Shifts in Diet and Gut Microbiota of the American Bison (Bison bison)

North American bison (Bison bison) are becoming increasingly important to both grassland management and commercial ranching. However, a lack of quantitative data on their diet constrains conservation efforts and the ability to predict bison effects on grasslands. In particular, we know little about the seasonality of the bison diet, the degree to which bison supplement their diet with eudicots, and how changes in diet influence gut microbial communities, all of which play important roles in ungulate performance. To address these knowledge gaps, we quantified seasonal patterns in bison diet and gut microbial community composition for a bison herd in Kansas using DNA sequencing-based analyses of both chloroplast and microbial DNA contained in fecal matter. Across the 11 sampling dates that spanned 166 days, we found that diet shifted continuously over the growing season, allowing bison to take advantage of the seasonal availability of high-protein plant species. Bison consumed more woody shrubs in spring and fall than in summer, when forb and grass intake predominated. In examining gut microbiota, the bacterial phylum Tenericutes shifted significantly in relative abundance over the growing season. This work suggests that North American bison can continuously adjust their diet with a high reliance on non-grasses throughout the year. In addition, we find evidence for seasonal patterns in gut community composition that are likely driven by the observed dietary changes.     

Hormonal control of estrous cyclicity and attempted superovulation in wood bison (Bison bison athabascae)

The wood bison (Bison bison athabascae) is a threatened Canadian species that has faced extinction twice in the last 100 yr. Development of assisted reproductive technologies could help ensure the long-term propagation and genetic management of this species. The objectives of this study were to refine estrus synchronization techniques and evaluate superovulatory responses after FSH or eCG administration. In Experiment 1, females were fitted with Syncro-mate B (SMB) implants for 9 d and received an injection of either estradiol valerate (E2V; n = 9) or cloprostenol (PGF; n = 9) at implant insertion (Day-9). In Experiment 2, estrus was synchronized with SMB implants and a PGF injection of Day-9, and superovulation was attempted on Day-2 with either 2500 IU eCG (n = 5) or 400 mg Folltropin-V (n = 5). In each experiment, biosin were examined daily for estrual behavior. Ultrasonography was used during the luteal phase to detect ovulation and assess ovarian status; feces were analyzed by ELISA for immunoreactive progestogens (P) to study ovarian endocrine responses. In Experiment 1, a closer synchrony of estrus was observed between Days 2 to 4 among the PGF-treated (77.8%) than the E2V-treated (66.7%) females. Corpora lutea (CL) were detected in 55% of E2V- and PGF-treated females. In Experiment 2, neither treatment successfully induced superovulation, with only a single female per treatment producing > or = 1 CL. In both experiments, progestogen profiles were similar for each treatment (P < 0.05).     

Identification of bovine and novel interferon-tau alleles in the American plains bison (Bison bison) by analysis of hybrid cattle x bison blastocysts

The objective of this study was to generate bison x cattle hybrid embryos by in vitro fertilization, to assess their developmental potential, to determine the pattern of secretion of the embryonic signaling molecule interferon-tau (IFN-tau), and to identify novel IFN-tau mRNA polymorphism in the American plains bison. A total of 600 bovine oocytes were inseminated with frozen-thawed bison semen. Of these, 40.7% cleaved and 14.8% proceeded to the blastocyst stage. Individual blastocysts were cultured on a basement membrane (Matrigel) and their ability to attach and form outgrowths was monitored. A total of 36 blastocysts were cultured of which 22 formed outgrowths. During individual culture, medium samples were collected and their IFN-tau concentration was measured. On day 6 after onset of individual culture, attached outgrowths produced significantly more IFN-tau than unattached viable or degenerate blastocysts. At this time, female conceptuses also produced significantly more IFN-tau than their male cohorts. However, by day 12 this difference had disappeared. Total mRNA was extracted from three individual outgrowths and analyzed by RT-PCR. Subsequent sequencing of 28 clones showed several known bovine IFN-tau sequences as well as two novel sequences termed bisIFN-tau1 and 2. To determine the origin of these, DNA was extracted from bison semen and analyzed by PCR. One bovine IFN-tau sequence (bovIFN-tau1d) as well as bisIFN-tau2 and a third novel sequence bisIFN-tau3 were detected. This study demonstrates the feasibility of using hybrid embryos for the analysis of developmentally regulated gene expression in species where embryos may not be available.     

Seasonality of reproduction in wild boar (Sus scrofa) assessed by fecal and plasmatic steroids

The collection of biological samples through non-invasive techniques represents one way of monitoring in vivo physiological changes associated with reproductive activity. Such techniques are particularly important for the study of animal species in the wild.The goals of this study were 1) to evaluate fecal progestogen (P), estrogen (E), and androgen (A) by means of radioimmunoassays, in male and female wild boars culled in the Piedmont, Italy area; 2) to compare them with plasmatic concentrations and the animals’ reproductive status; and 3) to assess variations in reproductive seasonality between two populations of wild boars living in a mountainous vs. a plain habitat in Piedmont.The results demonstrate a positive correlation between fecal and plasmatic steroid concentrations (r = 0.46, 0.58, and 0.45 for plasma P₄ and P, E₂ and E, and T and A; P < 0.05). Moreover, high fecal levels of both P and E (>170 ng/g and >100 pg/g respectively) were found in 70.6% of pregnant sows and in none of the non-pregnant animals, thus supporting the use of this technique for detecting pregnancy status in wild boar.Similar birth patterns were displayed by the mountain and plain populations, but births peaked significantly only in the mountain population, in the spring (46%, P < 0.05, vs. other seasons). A corresponding autumnal peak of plasma testosterone concentrations in males was displayed only by the mountain population (7.4 vs. < 2.0 ng/mL in the other seasons, P < 0.05).The correlation between fecal and plasmatic steroid concentrations obtained in this study supports the applicability of this non-invasive sampling technique for monitoring reproductive status in wild boar, thus enabling a more informed and correct management of the species.     

Isozyme characterization of cattle (Bos taurus) and American buffalo (Bison bison) cell cultures.

Four Bovidae cell lines (BEK-1, MDBK, Bu and EBTr) were characterized by means of enzymatic biochemical markers. Out of 15 enzymatic systems, 3--adenosine deaminase (Ada), phosphoglucomutase (Pgm) and nucleoside phosphorylase (Np)--were found to be polymorphic and quite suitable for biochemical identification of each cell line. The Bu cell line has shown a Np phenotypic pattern which could be distinctive of the Bison bison species.     

Reproductive effort and associated costs in bison (Bison bison): do older mothers try harder?

To examine the prediction that reproductive effort should increasewith age, I compared female bison (Bison bison) of varying agesin terms of maternal behavior, reproductive costs, and the qualityand quantity of offspring. In support of predictions, oldermothers showed more tolerance toward and spent more time nursingtheir calves in months 1–5 than expected based on agedifferences in size and presumed milk production. The two oldestmothers, who died before calving again, appeared to make thegreatest effort. When mothers were barren between calves, whichoccurred more often in older females, their increased investmentenhanced the weight, dominance, maturation rate, and/or fecundityof previous and subsequent offspring. In contrast to predictions,however, offspring quality did not generally increase with maternalage; in fact, primiparae tended to produce larger daughters.Nursing behavior varied little in month 1, when offspring conditionwas apparendy most affected. Young mothers contacted their calvesmore often and tended to graze more during the first month.Reproductive costs appeared greater for young mothers; theirfecundity in years after calving was relatively low. Proportionalweight loss following reproduction decreased with age, althoughchanging growth rates complicate interpretation. The resultssuggest a general decrease in reproductive effort, or at leastin associated costs, during the reproductive life span. Thispattern may be due in part to the increased experience and dominancestatus of older mothers, through which they may avoid some ofthe reproductive costs incurred by primiparae.     

Endocrine and behavioral observations during transition of non-breeding into breeding season in female American bison (Bison bison)

This study provides endocrine data in relation to behavioral events during the transition of the non-breeding into the breeding season in American bison (Bison bison). Fecal progesterone metabolite patterns (20-oxo-P) were obtained in 13 adult female American bison and hormonal data were correlated with behavioral observations; i.e. copulation, male tending, female tail-up behavior and gestation length. Based on fecal progesterone metabolite patterns, the breeding season started between the middle of July and early August. Predictable short cycles reflected the transition from non-breeding to the breeding season; the luteal phase of these cycles was 4.10+/-0.86 days. Copulations and female tail-up behavior were reliably associated with the hormonally detected ovulation. Male tending behavior was more loosely associated with hormonally detected ovulation. The observed hormonal pattern in the study females indicated that 9 of 10 pregnant cows conceived during the second ovulatory period in the breeding season. One other cow conceived during her third ovulatory period, and one cow did not conceive until later in the breeding season by beginning of October. Gestation duration was on average 266.30+/-1.00 days. In summary, this study confirmed that the bison is a seasonally polyestrous species; the transition from the non-breeding into the breeding season was characterized by short cycles with low progesterone metabolite values.     

Restriction fragment length polymorphism (RFLP) of exon 2 of the MhcBibi-DRB3 gene in American bison (Bison bison)

Polymerase chain reaction (PCR) primers specific to exon 2 of the bovine lymphocyte antigen (BoLA)-DRB3 gene were successfully used to amplify the equivalent region in 469 American bison (Bison bison). In domestic cattle, alleles of DRB3 are assigned through a restriction fragment length polymorphism (RFLP) analysis of the patterns of fragment lengths observed after digestion with the restriction enzymes RsaI, BstYI and HaeIII. In bison, using the same procedure, the observed RFLP patterns provided evidence for the strong conservation of restriction sites previously reported in cattle.