Promising New Technologies for Semen Evaluation

Introduction Assessment of seminal plasma and sperm-membrane associated constituents has led to the isolation of four proteins that provide utility for predicting fertility potential of bulls. All four of these proteins have been isolated and characterized biochemically. They have also proved to be very valuable as a diagnostic indicator of fertility beyond the traditional breeding soundness exam (BSE) identified by Chenoweth et al. (1992), since bulls with identical physical semen characteristics still may vary greatly in fertility when used for natural mating or artificial insemination. The specific proteins found in bovine semen that reflect fertility potential include osteopontin (OPN), a lipocalin-type prostaglandin D (PGD) synthase, fertility-associated antigen (FAA) and type-2 tissue inhibitor of metalloproteinases (TIMP-2). Since a specific gene encodes for particular protein, the potential exists to easily screen for these predictors of fertility. Single nucleotide polymorphisms (SNPs) in genes are becoming valuable tools in both proteomics and genomics. Subtle mutations in the gene from one individual to another can be detected, leading to the prediction of fertility at a day of age rather than puberty to collect semen. Within the FAA gene, SNPs have been isolated that cause conformational changes in the carboxyl terminus of the protein. When a monoclonal antibody (M1) is used to screen for the FAA protein, the aberrant FAA form is not detected and the bull is subsequently labeled FAA-negative. The use of polymerase chain reactions (PCR) techniques will allow researchers to amplify and easily diagnose those individuals containing mutations or SNPs. The four proteins as fertility markers in bulls and the promising new technologies for assessing semen/donors will be discussed as evaluators of fertility potential.