The effect of sephadex and sephadex ion-exchange filtration on the improvement in quality and freezability of low-grade buffalo semen ejaculates was assessed. Two types of filtration columns were used: one containing only sephadex G-10 (FS) and the other sephadex G-10 along with ion-exchangers (diethyl amino ethane-52 (DEAE-52) cellulose and carboxy methyl-52 (CM-52) cellulose; FS + IE). Unfiltered samples served as controls. Semen ejaculates extended in Tris-citric acid (1:4) (n = 16; initial motility 40-50%) were filtered at the rate of 1.5 ml/min under negative pressure at room temperature (28-30 degreesC). The mean recovery rate (%) of motile spermatozoa in the FS (85.9 +/- 1.5 1) and FS + IE (77.10 +/- 2.28) filtrates did not differ significantly. Percentages of sperm motility, normal acrosomes, and intact plasma membranes were highest (P < 0.05) in FS + IE, intermediate (P < 0.05) in FS and lowest (P < 0.05) in controls at the three stages of cryopreservation (postfiltration final dilution, after equilibration, and after freezing). Mean sperm abnormalities were lowest (P < 0.05) in the filtrates of FS + IE, moderate (P < 0.05) in FS and highest in controls at all stages of freezing. Compared to dilution and equilibration, freezing greatly reduced (P < 0.05) the overall percent motility, normal acrosomes and intact plasma membranes. The spermatozoa eluted through FS + IE columns proved more resistant (P < 0.05) in bearing dilution, equilibration, freezing and thawing stresses than the spermatozoa from FS and control samples. It is concluded that filtration systems containing an FS + IE column can effectively enhance the quality and freezability of extended, low quality buffalo semen. © 2002 Elsevier Science Inc. All rights reserved.