The Effects of an Oxygen Scavenger and Coconut Water on Equine Sperm Cryopreservation

•Coconut water (CW) is a viable substitute to egg yolk (EY) in cryopreserving stallion sperm.•Oxyrase may not give added benefit in stallion sperm cryopreservation.•Post-thaw stallion sperm fertility rates are higher with CW than EY.

Alternative sources of lipoproteins in semen extenders could replace animal by-products. We hypothesized that: (1) post-thaw semen parameters and fertility would not be different in coconut water (CW)-treated samples compared with egg yolk (EY)-treated samples and (2) the use of an oxygen scavenger (Oxyrase) would improve post-thaw sperm motility and membrane integrity and decrease lipid peroxidation. Experiment 1: three ejaculates each from five stallions were split into four treatments: EY, CW, egg yolk with Oxyrase, and coconut water with Oxyrase. Computer-assisted sperm analysis measured progressive and total motility, velocity, and linearity. Membrane integrity, apoptosis, and lipid peroxidation were evaluated using propidium iodide, annexin, and BODIPY fluorescent probes, respectively. Samples were cryopreserved, stored in liquid nitrogen, and then thawed to 37°C and analyzed again. Experiment 2: one ejaculate was divided into two aliquots and cryopreserved using either CW or EY. In a crossover design, 12 mares were bred on two consecutive cycles with either EY or CW. Pregnancy evaluations were at 14-day gestation. No differences were detected in sperm parameters between CW and EY (P > .05). Oxyrase did not improve sperm motility parameters in post-thaw samples, nor did it show protective effects for viability or against membrane damage (P > .05). More mares became pregnant using CW than EY (11/12 vs. 6/12, respectively; P = .013). Use of CW is a viable alternative to animal-based products in the cryopreservation of stallion semen.