Improving sperm banking efficiency in endangered species through the use of a sperm selection method in brown bear (Ursus arctos) thawed sperm

Abstract

BackgroundSperm selection methods such as Single Layer Centrifugation (SLC) have been demonstrated to be a useful tool to improve the quality of sperm samples and therefore to increase the efficiency of other artificial reproductive techniques in several species. This procedure could help to improve the quality of genetic resource banks, which is essential for endangered species. In contrast, these sperm selection methods are optimized and focused on farm animals, where the recovery task is not as important as in endangered species because of their higher sperm availability. The aim of this study was to evaluate two centrifugation methods (300 x g/20 min and 600 x g/10 min) and three concentrations of SLC media (Androcoll-Bear −80, 65 and 50%) to optimise the procedure in order to recover as many sperm with the highest quality as possible. Sperm morphology could be important in the hydrodynamic relationship between the cell and centrifugation medium and thus the effect of sperm head morphometry on sperm yield and its hydrodynamic relationship were studied.ResultsThe samples selected with Androcoll-Bear 65% showed a very good yield (53.1 ± 2.9) although the yield from Androcoll-Bear 80% was lower (19.3 ± 3.3). The latter showed higher values of motility than the control immediately after post-thawing selection. However, both concentrations of colloid (65 and 80%) showed higher values of viable sperm and viable sperm with intact acrosome than the control. After an incubation of 2 h at 37 °C, the samples from Androcoll-Bear 80% had higher kinematics and proportion of viable sperm with intact acrosome. In the morphometric analysis, the sperm selected by the Androcoll-Bear 80% showed a head with a bigger area which was more elongated than the sperm from other treatments.ConclusionsWe conclude that sperm selection with Androcoll-Bear at either 65% or 80% is a suitable technique that allows a sperm population with better quality than the initial sample to be obtained. We recommend the use of Androcoll-Bear 65% since the yield is better than Androcoll-Bear 80%. Our findings pave the way for further research on application of sperm selection techniques to sperm banking in the brown bear.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-017-1124-2) contains supplementary material, which is available to authorized users.

Single Layer Centrifugation Improves the Quality of Fresh Donkey Semen and Modifies the Sperm Ability to Interact with Polymorphonuclear Neutrophils

“…In effect, in the horse, the seminal protein CRISP3 has been found to inhibit the binding mechanism between viable spermatozoa and PMN involved in phagocytosis [ 52 ], improving fertility in mares [ 53 ]. In jennies, suppression of sperm-PMN binding by the presence of seminal plasma has also been identified [ 18 ], which would also be in agreement with the observed effect of seminal plasma in this study. We can thus hypothesize that sperm selection with Equicoll leads to the removal of seminal plasma components involved in the sperm protection from phagocytosis, since a previous study reported that the percentages of phagocytosis are low in the presence of seminal plasma [ 26 ].…”

“…Also in pigs, centrifugation of semen with SLC with Porcicoll prior to cryopreservation increases the cryotolerance and fertilizing ability of frozen/thawed sperm [ 19 , 20 ]. Even in brown bears, centrifugation with SLC has also been reported to improve the proportion of spermatozoa with intact plasma membrane and acrosome [ 17 , 18 ]. In bulls, centrifugation through SLC with a species-specific colloid (Androcoll-B/Bovicoll) also results in an increase in the proportions of spermatozoa with high mitochondrial membrane potential and high relative levels of peroxides [ 16 ], and in some kinematic parameters, but has no impact upon total and progressive motility of cooled-stored semen [ 46 ].…”

“…To the best of our knowledge, however, no study with fresh donkey semen has been performed nor has any evaluated the effects of SLC with Equicoll on mitochondrial activity, and intracellular levels of ROS and calcium. Other studies in rams [ 14 ], pigs [ 15 ], bulls [ 16 ], and brown bears [ 17 , 18 ] have demonstrated that centrifugation with SLC increases the proportions of spermatozoa with an intact plasma membrane and acrosome, high mitochondrial activity, an intact DNA, and progressive motility, and has also been found to increase sperm cryotolerance when performed before cryopreservation [ 19 , 20 ].…”

Does single‐layer centrifugation with Bovicoll improve sperm quality of frozen‐thawed semen in Fleckvieh bulls?

“…Different studies have been carried out in this direction. It was found that SLC positively influenced some of the semen parameters in species and breeds such as great panda (Cai et al, 2018), brown bear (Álvarez‐Rodríguez et al, 2016; Anel‐Lopez et al, 2017), camel (Malo, Crichton, Morrell, Pukazhenthi, & Skidmore, 2017), misty panther (Tipkantha et al, 2016), andalusian donkey (Ortiz et al, 2015), red deer (Anel‐López et al, 2015) or blanca‐celtibérica goat (Jiménez‐Rabadán et al, 2012).…”

“…SLC has been successfully used to select sperm of stallions (Hoogewijs et al, 2011) prior to cryopreservation and remove bacteria from ejaculates in boar semen (Morrell & Wallgren, 2011). SLC has also been tested on many wild animal species, such as giant panda (Cai et al, 2018), brown bear (Anel‐Lopez et al, 2017) and clouded leopard (Tipkantha, Thuwanut, Morrell, Comizzoli, & Chatdarong, 2016). Despite its wide application, there are relatively few publications on the influence of the SLC method carried out before freezing on the quality of bull sperm, which is analysed by kinematic and morphological parameters on thawed semen.…”