Abstract. The literature on hemostatic processes in swine is sparse and often fragmentary; hence, we conducted our study to characterize age-related changes in selected parameters of primary and secondary hemostasis in 50 growing pigs between day 2 and week 24 of age. We measured platelet count (PLT), mean platelet volume, platelet-to-large cell ratio, prothrombin time, activated partial thromboplastin time (aPTT), thrombin time (TT), and fibrinogen concentration. Among primary hemostasis parameters, PLT underwent the largest fluctuation with the animals' age, ranging from 340 to 730 × 10 9 /L. However, statistical significance was only detected for 4-week-old piglets compared to 18-week-old animals. Of the secondary hemostasis parameters measured, TT and aPTT were the most changeable. Activated partial thromboplastin time displayed a characteristic biphasic course, being relatively short before week 5 of age (17.8-19.9 s) and then becoming much longer (28.7-52.5 s). The aPTTs measured in animals 6 weeks of age and older were statistically different (p < 0.01) from those in younger piglets. The 2 main components of hemostasis, platelet hemostasis and plasma coagulation, did not develop at the same time. It took much longer for secondary hemostasis to stabilize, whereas platelet parameters were stable early in life.

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Acute colic in horses, especially presentations requiring surgical correction, such as large colon volvulus, very often involves defective or excess platelet activation. The PFA-100 is a new point-of-care analyser that evaluates platelet function by measuring closure time (CT) in the whole blood of healthy horses in a standardised manner. However, there are no reports on platelet function in horses with colic measured by the PFA-100. The aim of the present study was to investigate platelet function in a group of horses suffering ascending colon displacement (ACD) and who underwent surgery compared to a group of control (C) horses. Thirty ACD cases and twenty untreated clinically healthy control horses were included. Blood samples were collected from the ACD horses prior to and 24, 48 and 72 h after laparotomy. Red blood cell count (RBC), haematocrit (HCT), haemoglobin (Hb) concentration, white blood cell count (WBC), total plasma protein (TP) concentration, platelet count (PLT), platelet volume (MPV) and ADP closure time (CT-ADP) were measured. CT was determined on a PFA-100® device using collagen/ADP cartridges. There were no significant differences in RBC, PLT and MPV between C and ACD horses pre-operatively. Reduced PLT was observed in the post-operative period. The mean CT-ADP of C horses was 96.43 ± 12.53 and 91.43 ± 2.51 seconds in the ACD group prior to surgery. CT-ADP was changed after surgery whereby CT-ADP time was more than doubled. We conclude that the PFA-100 ® can be used to detect platelet function defects in horses.