Semen and Sperm Characteristics of Swamp Buffalo (Bubalus bubalis) Bulls for Artificial Insemination in Thailand, in Relation to Season

Koonjaenak S. 2006. Semen and Sperm Characteristics of Swamp Buffalo (Bubalus bubalis) Bulls for Artificial Insemination in Thailand, in Relation to Season. Doctoral thesis. ISSN 1652-6880, ISBN 91-576-7263-6 In this thesis work we tested the hypothesis that tropical climatic conditions affect the quality of fresh and frozen-thawed (FT) spermatozoa from swamp buffalo bulls used for artificial insemination (AI) in Thailand, as is the case with Bos taurus and B. indicus. Ejaculates from five mature, healthy swamp buffalo AI bulls, and FT AI doses (n=218) prepared between 1980 and 1989 and between 2003 and 2005 from 18 AI swamp buffalo sires were assessed over three seasons of the year, the rainy season (i.e. July–October), winter (i.e. November–February) and summer (i.e. March–June), each with a distinct temperature and humidity. Semen and sperm characteristics were evaluated. Analyses included sperm count, motility (assessed subjectively and by computer-assisted sperm analysis [CASA]), morphology (using phase-contrast light microscopy and scanning electron microscopy [SEM]), plasma membrane integrity (PMI) (using a hypo-osmotic swelling test [HOST]) and SYBR-14/propidium iodide [PI]), plasma membrane stability (PMS) (using Annexin-V/PI) and deoxyribonucleic acid (DNA) integrity (using acridine orange [AO] staining and flow cytometry [FCM]). Semen/sperm variables, sire age, ejaculates (week of collection) and year of semen collection/processing were investigated for their statistical relation to season. Whereas semen quality (including sperm output, pH and initial sperm motility) did not differ between the seasons, PMI and the relative proportion of morphologically normal spermatozoa were highest during summer. Few spermatozoa (<15%/ejaculate) had abnormal morphology including SEM, with abnormalities resembling those in other bovidae. Tail defects were the only variable that was affected by season (with the highest percentage of defects seen during the rainy season). In FT semen, PMI (using SYBR-14/PI) and PMS were highest in winter. Across seasons, ~50% of post-thaw spermatozoa depicted linear motility, a proportion that decreased to ~35% during incubation (38C for 60 minutes), without marking any seasonal difference. Sperm velocities such as straight linear velocity (VSL), average path velocity (VAP) and curvilinear velocity (VCL) were highest in semen processed during the rainy season, but amplitude of lateral sperm head displacement (ALH) was highest in summer, and these differences were retained after incubation. The sperm DNA was hardly damaged (with <3% fragmentation, expressed as DNA fragmentation index [DFI], among seasons), being best during the rainy season, although this variable was positively related to loose abnormal sperm heads. In conclusion, seasonal variations did not appear to cause deleterious changes in semen parameters or sperm quality of ejaculated or FT spermatozoa from swamp buffalo AI sires in tropical Thailand, despite some variation among seasons.