Traditional and non-traditional methods used for discrimination among Ossimi rams with different field fertility

Abstract

This study aimed to differentiate among rams of different field fertility by using traditional (semen characteristics, sexual traits and testosterone level) and non-traditional [seminal plasma (SP) proteins profile, and ultrasound imaging of the testes and the accessory genital glands (AGGs)] methods. Also, the relationship between sexual traits and semen characteristics in these rams was investigated. A total of 300 ejaculates from 30 Ossimi rams [19 fertile (F), 8 subfertile (SF), and 3 infertile (IF)] were collected by electroejaculation and examined for sperm motility, viability, morphology and plasma membrane integrity. As well, sperm cell concentration and seminal index of these ejaculates were calculated. Ovine SP was recovered by centrifugation and its total protein concentration was determined by hand-held Refractometer; then SP proteins were separated on 15% (w/v) polyacrylamide gel. Horn length, horn diameter (HD), poll distance, face length, scrotal circumference (SC) and body weight of all rams were determined. All semen characteristics rather than the ejaculate volume (EV) of F rams were greater (P < 0.001) than those of SF and IF rams. On contrary, SF and IF rams had extremely (P < 0.001) prolonged stimulation time (ST) and higher % abnormal morphology (AM) compared with F rams. Moreover, F rams had greater (P < 0.01) HD and SC than SF and IF rams and these two sexual traits were correlated with semen characteristics. Ultrasound imaging of testes and AGGs revealed clear differences among the three groups of rams. Additionally, F rams had greater (P < 0.001) serum (6.51 ± 0.14 ng/mL) and SP (3.27 ± 0.69 ng/mL) testosterone concentrations than SF and IF rams. In total, 9 protein bands with molecular weight range of 6.5–175 kDa were detected in ovine SP. Protein band of 40 kDa was detected in the breeding season only and was prominent in F rams in comparison with SF and IF rams but, those of 175 and 116 kDa were obvious in IF and SF rams and faint to absent in F rams either in breeding or non-breeding season. In conclusion, however, HD and SC discriminate among rams of different field fertility but it is recommended to combine both traditional and non-traditional methods to get precise discrimination. Moreover, SP proteins were closely correlated with semen characteristics and ram fertility and that of 40 kDa might be new candidate of fertility-associated proteins in Ossimi rams.