I found this
Sperm actually only makes up about 5% of semen. The rest comes from the Seminal Vesicle, Prostate Gland and Cowpers Gland. The albumen, sugars, acids and enzymes produced by these glands make up the majority of ejaculate and make the sperm motile and enable them to live outside the body. Pre-cum is produced by the Cowpers Gland, and functions to make the acidic urethra more hospitable for the semen