Effects of pH during liquid storage of goat semen on sperm viability and fertilizing potential.

•Sperm motility was strongly correlated with pH during liquid storage of goat semen.•Extender renewal improved sperm motility by maintaining a stable semen pH.•Semen coating with egg yolk improved sperm motility by increasing tolerance to pH.•The new extender, n-m-ZAP, sustained a stable pH and dramatically improved sperm fertility.