Reprod Dom Anim 50, 206–213 (2015); doi: 10.1111/rda.12471 ISSN 0936–6768

Effect of Reproductive Seasonality on Gamete Quality in the North American Bison (Bison bison bison) S Krishnakumar1, DP Whiteside2,3, B Elkin2,4 and JC Thundathil1 1 Department of Production Animal Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada; 2Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, University of Calgary, Calgary, AB, Canada; 3Animal Health Centre, Calgary Zoo, Calgary, AB, Canada; 4Wildlife Division, Department of Environment and Natural Resources, Government of Northwest Territories, Yellowknife, NT, Canada

Contents The objective was to investigate the effects of reproductive seasonality on gamete quality in plains bison (Bison bison bison). Epididymal sperm (n = 61 per season), collected during the breeding season (July–September), had significantly higher post-thaw total motility (36.76  14.18 vs 31.24  12.74%), and lower linearity (0.36  0.06 vs 0.39  0.04) and wobbliness (0.49  0.04 vs 0.51  0.03; mean  SD) compared to non-breeding season (January–March) samples. Representative samples (n = 4) from each season were used in heterologous IVF trials using cattle oocytes. Cleavage, morulae and blastocyst percentage were higher for breeding vs non-breeding season sperm samples (81.88  6.8 vs 49.94  6.77; 41.89  13.40 vs 27.08  23.21; and 30.49  17.87 vs 13.72  18.98%, respectively). Plains bison ovaries collected during the breeding (n = 97 pairs) and non-breeding (n = 100 pairs) seasons were classified as luteal or follicular. Oocytes recovered from these ovaries were classified into five grades based on morphology. There was no significant difference in the number of luteal ovaries or grades of oocytes recovered. Oocytes were matured, fertilized (with frozen sperm from three bison bulls) and cultured in vitro. Cleavage percentage was higher for oocytes collected during breeding vs non-breeding season (83.72  6.42 vs 73.98  6.43), with no significant difference in subsequent development to blastocysts. In summary, epididymal sperm from non-breeding season had decreased total motility and resulted in reduced embryo production in vitro. Oocytes collected during non-breeding season had reduced ability to be matured, fertilized and/or undergo cleavage in vitro. Data suggested that season influenced gamete quality in plains bison.

Introduction There are two subspecies of the North American bison: plains bison (Bison bison bison) and wood bison (Bison bison athabascae). Currently, the North American bison is classified as Near Threatened by the International Union for the Conservation of Nature (IUCN Red List; Assessment year 2008). Our laboratory is developing cryopreservation methods for preserving bison sperm and assessing protocols for in vitro production of bison embryos as a part of ex situ conservation efforts. In that regard, it is important to consider reproductive seasonality of bison (Rutberg 1984; Komers et al. 1992; Berger and Cunningham 1994). However, the effects of seasonality on gamete quality have not been documented for the bison. There are several reasons for studying the effects of reproductive seasonality on bison gamete quality: firstly,

to determine the most suitable time of the year for harvesting germplasm for efficient preservation of genetics; secondly, to make informed decisions on timing of a cull for efficient recovery and preservation of germplasm of a diseased herd, if necessary; and lastly, seasonal influences on gamete quality in bison may serve as an experimental model for studies on gamete biology which may then be expanded to other endangered species. Seasonal effects on the quality of sperm and oocytes have been reported in several species. Season has been shown to affect the fertilizing ability and cryotolerance of stallion sperm (Janett et al. 2003). Summer infertility occurs in water buffalo (Bubalus bubalis) due to impaired sperm function (Koonjaenak et al. 2007). The chromatin integrity of sperm from sheep, Iberian red deer and brown bears (Garcia-Macias et al. 2006) has been reported to be influenced by season. Furthermore, a decrease in the proportion of sperm tagged for proteolytic degradation (ubiquitin-tagged sperm) during the breeding season in stallion has been reported (Sutovsky et al. 2003). Furthermore, seasonal effects on oocyte quality, and their ability to undergo in vitro maturation, fertilization and embryo development, have also been documented in several domestic and wildlife species (bovine: Al-Katanani et al. 2002; sheep: Stenbak et al. 2001; domestic cat: Spindler and Wildt 1999; and camel: Abdoon 2001; rhesus monkeys: Zheng et al. 2001). This study was designed to investigate the effects of reproductive seasonality on (i) paired testes volume and ovarian activity; and (ii) sperm and oocytes quality of plains bison.

Materials and Methods All procedures were approved by the Animal Care Committee of the University of Calgary (Protocol #M10083) and conducted in accordance with the guidelines established by the Canadian Council on Animal Care. Collection and cryopreservation of epididymal sperm Epididymal sperm were collected from plains bison (n = 61 per season) slaughtered at the local abattoir from July to September (breeding season samples) and from January to March (non-breeding season samples). © 2014 Blackwell Verlag GmbH

Effect of Seasonality on Bison Gametes

These animals were raised for meat purpose in farms across Alberta. All animals were at least 18 months of age and had a body weight ranging from 544 to 907 kg. Epididymal sperm collected in Tyrode’s HEPES-buffered medium were transported to the laboratory at 37°C and processed for cryopreservation according to the protocol previously described (Krishnakumar et al. 2011). Samples with

Effect of reproductive seasonality on gamete quality in the North American bison (Bison bison bison).

The objective was to investigate the effects of reproductive seasonality on gamete quality in plains bison (Bison bison bison). Epididymal sperm (n = ...
411KB Sizes 0 Downloads 5 Views