Cauda epididymal proteins and fertility

10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 We evaluated the relationships between proteins in cauda epididymis fluid (CEF) and fertility scores of dairy bulls. Fertility was expressed as the percentage point deviation of bull non-return rate (PD) from the average fertility of all bulls at an artificial insemination center. Number of services for each bull ranged from 1,074 to 52,820 and PD values, from + 7.7 % to – 6.6 %. CEF from 20 bulls was obtained from vasa deferentia cannulae and separated from sperm by centrifugation immediately after collection. Samples were evaluated by 2-D SDS-PAGE, gels stained with Coomassie blue and polypeptide maps were analyzed by PDQuest software. Protein quantities, defined as the total integrated optical density of the spots, were compared between groups of high (n = 12; PD ≥ 0) and low fertility sires (n = 8; PD < 0) and were also used as independent variables in regression analysis. Proteins were identified by capillary liquid chromatography nanoelectrospray ionization tandem mass spectrometry (CapLC-MS/MS). An average of 118 spots was detected in 2-D maps of the cauda epididymal fluid but we were unable to distinguish any protein that was only expressed in high fertility and or in low fertility bulls. However, the amount of α-L-fucosidase 2 and cathepsin D was 2.3 and 2.4-fold greater (p < 0.05) in high fertility than in low fertility bulls, respectively. Conversely, the intensities of three isoforms (24 – 27 kDa; pI 6.3 – 5.8) of prostaglandin D-synthase (PGDS) were from 3.2 to 2.2fold greater in low fertility sires (p < 0.05). An empirical regression model established that a significant proportion (R = 0.72; p < 0.0001) of the variation in fertility scores (PD values) was explained by the intensities of cathepsin D and one isoform of PGDS (24 kDa; pI 6.3). Thus, multiple proteins present in the cauda epididymal fluid are potential biomarkers of fertility in high use, mature Holstein bulls.