The effects of dried grape pomace supplementation on biochemical blood serum indicators and digestibility of nutrients in horses

Twelve adult Slovak warmblood sport horses were used to study the effect of dried grape pomace (DGP) on health through blood serum biochemical indicators, and on apparent total tract digestibility of dry matter (DM), organic matter (OM), crude protein (CP), acid detergent fibre (ADF) and neutral detergent fibre (NDF). The digestibility analysis was carried out by two in vivo methods, total faeces collection (TFC) and using lignin as a marker (ADL). Animals were divided into 3 groups: control group (C, without supplementation), experimental group 1 (E1, feed rations + 200 g of DGP) and experimental group 2 (E2, feed rations + 400 g of DGP). In animals, no health problems were detected during the trial. Of the blood serum indicators, only the concentrations of potassium (increase in E2 group compared to C group) and alanine aminotransferase (decrease in E2 group in comparison with E1 and C group) were affected (P < 0.05). The ADL method resulted in underestimated digestibility coefficients due to low recovery rates of lignin (less than 90%) in C group and E1 group. According to TFC, in E1 group higher digestibility coefficients were detected for DM, OM and CP (P > 0.05) compared to C group. However, in E2 group lower digestibility of all the studied nutrients was found (P > 0.05) in comparison with C group and E1 group. These results suggest that DGP could be used in horse diets up to 200 g without negative effect on their health and for a possible digestibility improvement of some nutrients.