Birchen and Blue Leonesa sperm cryopreservation: a new technique for evaluating the integrity of cockerel sperm membranes

ABSTRACT

1. Birchen and Blue Leonesa are two endangered chicken breeds mainly raised in Curueño Valley in North Spain. The establishment of a germplasm bank to guarantee the preservation of these breeds is needed. However, cockerels from different breeder flocks can show variance in semen cryoresistance.

2. The following work focused on the sperm characterisation and cryopreservation of Birchen and Blue Leonesa cockerels from four different breeders. A total of 30 semen pools were analysed. Besides conventional sperm analysis, including motility by computer-aided sperm analysis (CASA) and DNA fragmentation by TUNEL, the present study tested a double staining method (MitoTracker^TM Green FM/propidium iodide). This gave simultaneous assessment of plasma and acrosomal and mitochondrial membranes, which were previously validated by SYBR-14/PI, CASA, aniline blue and TUNEL.

3. No significant differences were found among fresh semen variables between breeds and breeders. For post-thawed variables, significant differences (P < 0.05) were found between breeders in sperm viability (58.0 ± 1.90 breeder D vs. 35.2 ± 7.41 breeder A, 37.2 ± 4.09 breeder B and 22.3 ± 5.92 breeder C) and DNA fragmentation (62.4 ± 9.91 breeder C vs. 31.8 ± 7.08 breeder B and 24.5 ± 5.49 breeder D). The lowest DNA fragmentation values for semen from breeder D birds were coincident with higher integrity of the mitochondrial membrane.

4. The results revealed higher sperm cryoresistance in the cockerels from one of the breeders, possibly due to differences in management system (e.g. diet, housing, control of stress elements and pathogens, reproduction practices or maintenance of genetic diversity). These differences may determine the sperm freezability, and thus the effectiveness of developing a germplasm bank.

KEYWORDS:

• Cryoresistance
• rooster
• sperm
• inbreeding
• MitoTracker^TM Green FM

Acknowledgments

The authors thank the Asociación de Criadores de Gallos de León, El Curueño for their help in providing their Blue and Birchen Leonesa cockerels for the semen collection.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research is part of a project that received funding from the European Union’s Horizon 2020 Research and Innovation Programme under grant agreement Nº 677353 IMAGE. Part of this research was funded by the project [RTA2017-00034-00-00].