AbstractThe ejaculated semen consists of two major components viz. sperm cells (spermatozoa) and the fluid part obtained after centrifugation called seminal plasma. The spermatozoa originate from the semniferous tubule and are suspended in the seminal plasma. The seminal plasma is composed of secretions contributed by the testis, epididymis, seminal vesicles, ampullae, prostate and bulbourethral glands. About 60-80 % of the ejaculated semen of the bull originates from these sources. Seminal plasma is a highly complex biological fluid containing proteins, amino acids, enzymes, fructose and other carbohydrates, lipids, major minerals and trace elements. Seminal plasma proteins partly originates from the blood plasma by exudation through the lumen of the male genital tract and partly are synthesized and secreted by various reproductive organs and are known as seminal plasma specific proteins. Several seminal plasma proteins of blood origin viz. prealbumin, albumin, globulin, transferring, α-antitrypsin, β-lipoprotein, β-glycoprotein, orsomucoid, kininogen, Peptide hormones, IgG, IgA and IgM have been identified and characterized. These proteins are involved in regulation of osmotic pressure and pH of seminal plasma, transport of ions, lipid and hormones. A major part of seminal plasma proteins originate from the testis, epididymis, vas deference, prostate, seminal vesicle and bulbourethral glands. The biosynthesis and secretion of these proteins is regulated by testosterone levels in the blood.