ABSTRACT
The aboveground biomass of dry knotweed was administered daily to large groups of young (1- to 3-year-old) stallions of the Czech Warmblood, Czech-Moravian Coldblood and Silesian Norik breeds, fed individually for 4 and 6 months in two successive winter experiments. Their fitness was compared with control groups consisting of equally numerous subgroups comparable in age, breed, body mass and initial blood parameters. The effects of knotweed on the horses’ fitness were evaluated based on changes in blood characteristics. Even if administered in small amounts, 150 g per day, knotweed could (1) increase the thrombocyte numbers, (2) increase the globulin content (thus improving the horses’ immunity, which is desired in large groups of animals), (3) stimulate lipid metabolism in cold-blooded horses and (4) decrease the concentration of cholesterol. The long-lasting effect of knotweed on both the urea and triglyceride–cholesterol ratio presumably reflected, between the two experiments, the temporary protein starvation of horses on pastures with poor quality of grass in a dry summer.