Sperm in boars go through changes in the epididymis and during ejaculation to become capable of fertilizing an egg. Only ejaculated sperm can undergo further changes for fertilization. The sperm's protein and sugar content change as they mature in the epididymis. Proteins involved in fertilization are processed in the testis and epididymis. These findings help us understand how to assess the maturity and fertility of boar sperm.