Addition of antifreeze protein type I or III to extenders for ram sperm cryopreservation

Antifreeze proteins (AFP) play an important role in cellular survival at sub-zero temperatures. This study assessed the effect of AFP type I or III in semen extender (TRIS-egg yolk) for ram sperm cryopreservation. Pooled semen of four rams were allocated into five treatments: Control (CONT, without AFP); AFP Type I [0.1 (AFPI-0.1) or 0.5 (AFPI-0.5) μg/mL]; or III [0.1 (AFPIII-0.1) or 0.5 (AFPIII-0.5) μg/mL], and then frozen in six replicates. Treatments affected kinetic parameters, plasma membrane integrity and morphology (P 0.05) were observed in hypoosmotic test, sperm acrosome status, mitochondrial activity, chromatin condensation, perivitelline membrane binding rate and lipoperoxidation. In conclusion, the use of AFP, predominantly type I, may increase sperm cell protection during cryopreservation, with no adverse effect on potential fertilization capacity or increase in reactive oxygen species, being a potential cryoprotectant to ram sperm. [Display omitted] •Antifreeze protein (AFP) supplementation in ram sperm extender improves cryoresistance.•AFP type I enhanced the percentage of plasma membrane integrity in ram sperm.•AFP type I in ram semen extender led to greater sperm kinetics compared to control.•AFP treated groups had greater percentage of normal sperm cells compared to control.•AFP type I is a potential cryoprotectant to ram sperm.