The aim of this study was to determine the effects of the antioxidants glutamine and hyaluronan and the inclusion of different levels on microscopic semen parameters, lipid peroxidation and the antioxidant activities following the freeze-thawing of Angora goat semen. Ejaculates collected front three Angora goat bucks, were evaluated and pooled at 37 degrees C. The semen samples which were diluted with a Tris-based extender containing additives including glutamine (2.5:5 mM) and hyaluronan (500; 1000 mu l/ml), and an extender containing no antioxidants (control) were cooled to 5 C and frozen in 0.25 ml French straws and stored in liquid nitrogen. Frozen straws were thawed individually (37 degrees C) for 20s in a water bath for microscopic evaluation. Freezing extenders supplemented with 2.5 and 5 mM glutamine led to higher sperm motility and hypo-osmotic swelling test (HOST) values, compared to the control (P<0.05) following the freeze-thawing process. The addition of 500 mu l/ml hyaluronan resulted in a higher HOST percentage, compared to the addition of 1000 mu l/ml hyaluronan and the control (P<0.001). No significant difference was recorded in the percentage acrosome and total sperm abnormalities, following supplementation with antioxidants. The addition of antioxidants did not prevent malondialdehyde (MDA) formation, compared to the controls. Antioxidant treatment however decreased (P<0.01) the superoxide dismutase (SOD) activity. The maintenance of catalase (CAT) activity was demonstrated to be insignificant following addition of antioxidants. Further studies are required to obtain more repeatable results regarding the characterization of the enzymatic and non-enzymatic antioxidant systems in cryopreserved goat sperm. (C) 2008 Elsevier B.V. All rights reserved.