Carboxymethylchitosan with medium-molecular-weight affects kinectics and acrosome of stallion sperm after freezing/thawing.
Authors: de Moura Thalles Cloves Maciel, Arruda Lúcia Cristina Pereira, Cahú Thiago Barbosa, Bezerra Ranilson de Souza, Carneiro Gustavo Ferrer, Guerra Maria Madalena Pessoa
Journal: Journal of equine veterinary science
Summary
# Editorial Summary: Carboxymethylchitosan in Stallion Semen Cryopreservation Effective semen cryopreservation is essential for preserving valuable stallion genetics, but the freeze-thaw process causes cellular damage that compromises fertility outcomes; this research examined whether adding medium-molecular-weight carboxymethylchitosan (CQm), a potential antioxidant, to commercial freezing extenders could protect sperm quality. Researchers collected 20 ejaculates from four stallions and supplemented the Botucrio commercial extender with CQm at concentrations of 0, 0.75, 1.5, and 3 mg/mL before freezing at −196°C and thawing at 37°C. Contrary to expectations, the higher CQm concentrations (1.5 and 3 mg/mL) significantly impaired sperm function, reducing total and progressive motility, velocity measures (VCL, VSL, VAP), and wobble compared to the unsupplemented control group, with the highest dose (3 mg/mL) additionally causing marked acrosomal membrane damage. For practitioners involved in breeding programme management, these findings suggest that whilst medium-molecular-weight carboxymethylchitosan shows theoretical promise as an antioxidant, the concentrations tested here are counterproductive; alternative protective agents or substantially lower concentrations warrant investigation to improve post-thaw semen viability without compromising kinetic or fertilisation capacity.
Read the full abstract on PubMed
Practical Takeaways
- •High concentrations of carboxymethylchitosan in freezing extenders are detrimental to post-thaw sperm quality in stallions; avoid concentrations of 1.5-3 mg/mL in commercial protocols
- •When optimizing semen extenders with antioxidant additives, lower concentrations should be tested first, as more is not necessarily better for preserving sperm function
- •For breeding programs relying on frozen stallion semen, verify that any new additive claims are supported by rigorous testing of multiple sperm parameters before adoption
Key Findings
- •CQm concentrations of 1.5 and 3 mg/mL significantly reduced total motility, progressive motility, and velocity parameters (VCL, VSL, VAP, WOB) compared to control group (P < 0.05)
- •High concentration CQm at 3 mg/mL resulted in lower percentages of sperm with intact acrosomes compared to control group (P < 0.05)
- •Medium-molecular-weight carboxymethylchitosan at higher concentrations damages kinematic properties and acrosome integrity of stallion sperm after freezing/thawing cycles