This dissertation describes the effects of tetrastarch (130/0.4) on serum colloid osmotic pressure and thromboelastography variables in healthy pony mares. Additional variables assessed during this study included markers of haemodilution (PCV, TS) and serum creatinine and bile acid concentrations. Six clinically healthy Nooitgedacht pony mares were utilized in a crossover study design. Tetrastarch (130/0.4) was administered at 10, 20 and 40 ml/kg bwt to each mare in a random sequence with a two week washout period between each of the treatments. Packed cell volume (PCV), plasma total solids (TS), serum colloid osmotic pressure (COP), and platelet count were measured and thromboelastography (TEG) was performed before treatment (baseline), immediately after infusion (time 0), and 1, 6, 12, 24, 48, and 96 h after tetrastarch infusion. All TEG variables remained within reference range in all treatment groups. Administration of tetrastarch at 40 ml/kg bwt resulted in a prolonged K-time at 6 h post-infusion, and decreased maximum amplitude at 0, 1, 6, 24 and 48 h post-infusion compared to baseline. Administration of tetrastarch increased mean COP values above baseline in all three treatment groups, persisting to 24, 6 and 48 h after treatment with 10, 20 and 40 ml/kg of tetrastarch respectively. This study concluded that, although values remained within established reference ranges, the administration of tetrastarch (130/0.4) at 40 ml/kg bwt is more likely to induce changes in TEG variables than doses of 20 ml/kg or less. Tetrastarch increased COP in healthy horses at all evaluated dose rates. / Dissertation (MMedVet)--University of Pretoria, 2014. / gm2014 / Companion Animal Clinical Studies / unrestricted