Comparison of forages’ digestion levels for different in vitro digestion techniques in horses

Abstract

Forages are widely used in horse diets. Different in vitro techniques are being tried to determine the fermentation levels of forages in the horse digestive tract. This study aimed to evaluate the digestion levels of four dry forages commonly used in horse nutrition: alfalfa herbage, meadow hay, wheat straw, and Italian ryegrass. In vitro total digestion (TDT), in vitro Sunvold-large intestine digestion (SDT) and in vitro Menke-large intestine digestion (MDT) techniques were compared. The study determined in vitro true dry matter digestion (T-DMD), in vitro true organic matter digestion (T-OMD) and in vitro true neutral detergent fibre digestion (T-NDFD). Additionally, concentrations of straight short-chain fatty acids (SCFAs; acetic acid - AA, propionic acid , butyric acid, and valeric acid ) and branched short-chain fatty acids (BSCFA) were assessed. The highest in vitro T-DMD, T-OMD and T-NDFD values were determined by the in vitro TDT for the four forages (p<0.05). In vitro T-DMD and T-OMD values of alfalfa herbage were higher than those of Italian ryegrass, meadow hay and wheat straw in the in vitro TDT (p<0.001). In addition, in vitro T-DMD and T-OMD values of alfalfa herbage in the in vitro SDT were higher than those of meadow hay and wheat straw (p<0.001). In the in vitro TDT, the molarity of AA, total SCFA and BSCFA in the digestion fluid of alfalfa herbage was higher than those of other forages (p<0.05). The in vitro total enzymatic+fermentative digestion technique for horse forages revealed higher values than the in vitro fermentative digestion techniques. In general, the higher the non-structural carbohydrate and crude protein contents in the forage, the higher the results of the in vitro TDT compared to the other techniques.