Use of native chicken breeds (Gallus gallus domesticus) for the development of suitable methods of Cantabrian capercaillie (Tetrao urogallus cantabricus) semen cryopreservation

Background: The Cantabrian capercaillie (Tetrao urogallus cantabricus) is critically endangered. This subspecies has the lowest genetic variability and it is in regression. It belongs to Phasianidae family; therefore, the domestic chicken (Gallusgallus domesticus) could be a good model for developing reproductive technologies for use in capercaillie populations with low availability of animals. Objectives: In this study, we analyzed the response of capercaillie sperm to the freezing-thawing process for contributing to the development of a semen cryobank of Cantabrian capercaillie. Methods: We used domestic chicken as the animal model in order to obtain the freezing protocol before applying on capercaillie. In the first experiment, two different extenders (EK and LR84) and different concentrations [4% and 6% dimethyl-acetamide (DMA) v:v] of cryoprotectants were evaluated using in-straw freezing method in domestic chickens. A pilot study in capercaillie males, using the same conditions evaluated in chicken, was performed. Results: In chicken, we found that the LR84-4% DMA media provided the best results for freezing semen. In capercaillie study, LR84 extender seemed to be the most appropriate diluent and 4%was the better dose of DMA cryoprotectant agent. Further, based on previous studies carried out in rooster samples, we also tested the glycerol (8% v/v) as a cryoprotectant for capercaillie semen cryopreservation. Conclusions: Our results suggest that sperm from both domestic and wild species had a similar response to freezing-thawing processes. Mediterranean chickens may be used as a suitable model for developing sperm freezing protocols that can be extrapolated to threatened capercaillie populations. In addition, LR84 media with glycerol was the most efficient extender to freeze capercail lie sperm native.