Identification of biomarker candidates for fertility in spermatozoa of crossbred bulls through comparative proteomics.

Associations between expression of some proteins in spermatozoa and fertility have been sought in recent years to identify the male fertility markers. Since the incidence of sub-fertility is high in crossbred bulls, the present investigation was carried out on high- and low-fertile crossbred bulls to identify fertility markers in spermatozoa through proteomics approach. Sperm proteome of high-fertile bulls were compared with low-fertile bulls using 2D-DIGE and MALDI-TOF-MS techniques and the results were validated with immuno-blotting. The proteins MDH2, ENO1, RIBC1, CAPN7, ATP5D, LacA like protein-2 like, NCAPD3, DECR1, GCNT2, GDI2, TOP and USP12 were over expressed in high-fertile spermatozoa, whereas DST like isoform 1, TMEM43 and BSP1 were over expressed in low-fertile spermatozoa (P < 0.05). The differential expression ranged from 1.57 (GDI2) to 5.1 (BSP1) fold between the two groups. Based on the GO annotation, majority of them were involved in cellular and metabolic processes, with catalytic and binding activities, and localized in cell and organelles. Among these proteins, ENO1 and BSP1 were selected based on the degree of differential expression and reliability in identification, for further validation. Immuno-blotting studies indicated that ENO1expression was positively correlated (P < 0.05) while the expression of BSP1 was negatively (P < 0.01) correlated with bull fertility. The proportion of capacitated spermatozoa in frozen thawed spermatozoa of low-fertile bulls was higher (P < 0.05) as compared to high-fertile bulls. Collectively, the study identified some potential molecules in spermatozoa of bulls, which may act as a panel of biomarkers for fertility.

Testicular cell indices and peripheral blood testosterone concentrations in relation to age and semen quality in crossbred (holstein friesian×tharparkar) bulls.

Present study analyzed the changes in peripheral blood testosterone concentrations and testicular cytogram in relation to age and semen quality in crossbred males. Three different age groups of crossbred males viz. bull calves (6 months, n = 5), young bulls (15 months, n = 5) and adult bulls (4 to 6 years, n = 8) were utilized for the study. Testicular fine needle aspiration cytology technique was used to quantify testicular cytology and their indices. Peripheral blood testosterone concentrations were measured using enzyme-linked immunosorbent assay method. Semen samples collected from adult bulls were microscopically evaluated for quality parameters. Mean peripheral blood testosterone concentrations in bull calves, young bulls and adult bulls were 2.28±0.09 ng/mL, 1.42±0.22 ng/mL and 5.66±1.08 ng/mL respectively, and that in adult bulls were significantly different (p<0.01) from young bulls and bull calves. There was no significant difference between the proportion of different testicular cells in bull calves and young bulls. Between young and adult bulls, significant differences (p<0.01) were observed in the proportion of spermatocytes, spermatozoa, and sperm: Sertoli cell ratio. The proportions of Sertoli cells showed a significant difference (p<0.01) between the three age groups. The number of primary spermatocytes had a positive correlation with peripheral blood testosterone concentrations in bull calves (r = 0.719, p<0.01). Number of Sertoli cells per 100 germ cells was negatively correlated with blood testosterone concentration in young bulls (r = -0.713, p<0.01). Among different semen parameters in adult bulls, ejaculate volume (r = 0.790, p<0.05) had positive relationship, and sperm motility had significant negative correlation (r = -0.711, p<0.05) with testosterone concentrations. The number of Sertoli cells and Sertoli cell index had a positive correlation with various semen quality parameters (p<0.001). Results of the present study conclude that number of Sertoli cells and Sertoli cell index are good indicators of semen quality, but peripheral blood testosterone concentrations may not have a direct relationship with various seminal attributes in crossbred bulls.