coefficient of variation of bead concentration was 4.2%, and across all experiments was 6.2%. Least-squares estimates for sperm concentration differed significantly (P < 0.001) across methods. Least-squares estimates of sperm concentration were (decreasing order) Densimeter a , Sybr- PI/Beads b , FSC-SSC/Beads b,c , Spermacue c,d , Sybr-PI d,e and FSC-SSC e (values with different superscripts differ (P < 0.05)). Flow cytometry provides the opportunity of deter- mining sperm concentration and viability counts at the same time. The use of Sybr14-PI allows counting of cells specifically, which could be used to determine sperm concentration on extended semen samples and also to estimate the proportion of live and dead cells. Comparison of sperm DNA fragmentation and motility parameters between Quarter Horse and Mangalarga Marchador stallions M.C. Farrás, E.G. Fioratti, C. Ramires Neto, F.O. Papa, and M.A. Alvarenga Universidade Estadual Paulista, UNESP, Botucatu, SP, Brazil The aim of this study was to compare the semen quality of Quarter Horse stallions (QH) with a Brazilian breed called Mangalarga Marchador (MM) for cooling resistance (5 C and 15 C) and after 4 hours' exposure to 37 C. Two ejaculates were collected from each of 27 stallions (11 MM and 16 QH). The samples were diluted with BotusêmenÒ extender (Botupharma-Botucatu, Brazil) to a concentration of 50 x 106 sperm/mL in a volume that made a total dose of 800 x 106 of sperm cells. The samples were evaluated by a sperm chro- matin dispersion test Halomax Ò (Halotech-Spain) and computerized sperm analyzer (CASA-Hamilton Thorn- HTMIVOS 10) to assess the DNA fragmentation and motility parameters: total motility (MT) and progressive motility (MP). For motility evaluation, 10 mL of each sample were exposed to 37 C. The evaluations were conducted on fresh semen (T0), after 24 hours storage at 5 C or 15 C (T24) and after exposure to 37 C for 4 h after the storage (T24-4). For statistical analysis of MT and MP, we used analysis of variance (ANOVA) and the comparison of means was performed by Tukey test. For the analysis of sperm DNA fragmentation, the Kaplan-Meier survival test was used. Both tests were considered significant at 5%. The QH stallions had better sperm characteristics (P < 0.05) than MM stallions in storage systems, MT/5 C (QH ¼ 72.72 13.52 vs MM ¼ 55.72 24.18), MT/15 C (QH ¼ 73.22 14.54 vs MM ¼ 58.61 26.06), MP/5 C (QH ¼ 39.69 14.49 vs MM ¼ 25.00 18.64) and MP/ 15 C (QH ¼ 34.47 14.35 vs MM ¼ 22.17 16.07). The same occurred when the samples were exposed to 37 C, MT/ 5 C (QH ¼ 16.88 17.47 vs MM ¼ 2.67 6.83), MT/15 C (QH ¼ 14.34 15.97 vs MM ¼ 4.22 6.83), MP/5 C (QH ¼ 9.63 10.33 vs MM ¼ 1.28 3.66) and MP/15 C (QH ¼ 7.72 9.09 vs MM ¼ 1.89 4.03).The results of this study showed no difference between the storage temperatures, 5 C and 15 C, in any parameters evaluated by CASA (P > 0.05), showing that both are effective in maintaining the sperm viability for a period of 24 hours for both breeds studied. The QH group showed lower sperm DNA fragmentation in both storage systems, 5 C and 15 C during the periods T0, T24 and T24-4: QH/5 C: T0 ¼ 10.72 3.03, T24 ¼ 13.40 2.71, T24-4 ¼ 22.88 5.1; MM/5 C: T0 ¼ 11.78 4.66, T24 ¼ 14.11 4.89, T24-4 ¼ 29.11 20.30; QH/15 C: T0 ¼ 10.72 3.03, T24 ¼ 13.19 3.58, T24-4 ¼ 21.63 6.33; MM/15 C: T0 ¼ 11.78 4.66, T24 ¼ 14.56 4.91, T24-4 ¼ 27.50 19.92. The dynamics of sperm DNA fragmentation during the periods T0, T24 and T24-4 showed no difference between the storage tempera- tures and there was a lower resistance for cooling (P < 0.05) of MM sperm as compared with the QH. Acknowledgments Financial support: FAPESP (2009/06835-1; 2010/09387-7). Investigation of cathelicidins presence in horse seminal plasma E.G. Fioratti, A.I.S.B. Villaverde, M.C. Farras, C. Ramires-Neto, and M.A. Alvarenga Department of Animal Reproduction and Veterinary Radiology – São Paulo State University, Botucatu, Brazil The antimicrobial peptides of innate host defense systems show a broad spectrum of antimicrobial activity in vitro and provide a valuable means of defense against invading pathogens. The cathelicidin peptides have been identified in a number of mammalian species and are one of the major components of this peptide-based defense system. Several tests have been performed to correlate the effect of various seminal plasma constituents on fertility. But, to date their influence on the endometrium was not checked. The aim of this trial was to verify the presence of cathelicidins in horse seminal plasma using uni-dimensional SDS-poly- acrylamide gel electrophoresis (SDS-PAGE) and previous described molecular weight (MW) of these peptides in equine. Semen samples were collected from 15 mature, healthy and reproductively active Quarter Horse stallions by artificial vagina. Spermatozoa were separated from seminal plasma by centrifugation (1500 x g) for 10 min at room temperature and protease inhibitor was added. The supernatant was further clarified by centrifugation at 10 000 x g for 10 min (4 C) using an Eppendorf centrifuge and stored at -20 C until use. Total protein was estimated in each seminal plasma sample so that an equivalent amount of protein could be loaded in each lane. Furthermore, this allowed a comparison of the respective protein densities among stallions. Protein concentration was determined by a bicinchoninic acid protein assay kit. SDS-PAGE was per- formed in a vertical system using stacking and resolving gels containing 5% and 15% of polyacrylamide, respectively. Protein concentration was standardized to 24mg total/lane. Molecular weight marker kits, ranging from 3.6 to 31.7 kDa, were used as standards. Separated proteins were stained with 0.1% Coomassie brilliant blue R-250 dye. Gel images from SDS-PAGE were digitized and analyzed (Image- Master Ô 1D) to determine MW and integrated optical density (IOD). Total protein concentration among animals ranged from 6.27 to 25.65 mg/mL, presenting an average of 14.24 7.68 mg/ml. SDS-PAGE analysis revealed the exis- tence of three protein bands within the expected interval 6 th ISSR Abstracts / Journal of Equine Veterinary Science 32 (2012) 475-518 485