Horse Seminal Plasma proteins (HSP-1 and HSP-2) concentration: a possible marker for poor fertility?

Seminal plasma (SP) proteins have been assessed in relation to reproductive fertility levels or infertility, in several species of mammals, particularly domestic animals. Horse seminal plasma proteins 1 (HSP-1) and 2 (HSP-2) are the most abundant proteins in equine seminal plasma. The aim of this study was to investigate in adult stallions the concentrations of seminal plasma HSP-1/2 and total protein in the breeding season and non-breeding season and to determine if these concentrations were related with fertility. Seminal plasma was obtained from 42 ejaculates of 11 adult stallions (3-25 yrs). Stallions were allocated into two groups (good and poor fertility) according to pregnancy rates of mares, and to their semen viability data in the first collection day. Seminal plasma HSP-1/2 concentrations (mg/mL) were measured and analyzed by an Ultra High Performance Liquid Cromatography using a UHPLC column. There were significant differences (P<0.05) in total protein and HSP1/2 concentration (mg/mL, meanplusmn;SD) in the ejaculates from good and poor fertility stallions. The HSP1/2 concentration did not show differences in the first and second ejaculates of good fertility stallions in both the non-breeding and breeding season. Seminal plasma of stallions classified as poor fertility showed significant difference (P<0.05) in HSP-1/2 concentration between the first and second ejaculate in both the non-breeding and breeding season. In conclusion, the concentration of the major proteins of stallion seminal plasma HSP1/2 was higher in ejaculates from stallions with poor fertility, is not influenced by the season and could serve as biomarker for poor fertility in stallions.