Carbohydrate digestion in the stomach of horses grazed on pasture, fed hay or hay and oats

• Published in: Journal of equine veterinary science 2024-10, Vol.141, p.105152, Article 105152
• Main Authors: Bachmann, Martin, Schusser, Gerald Fritz, Wensch-Dorendorf, Monika, Pisch, Caroline, Bochnia, Mandy, Santo, Milena Marie, Netzker, Hanna, Woitow, Gerhard, Thielebein, Jens, Kesting, Stefan, Riehl, Gerhard, Greef, Jörg Michael, Heinichen, Karin, Zeyner, Annette
• Format: Article
• Language: English
• Subjects: Digestive disorders; Equine Gastric Ulcer Syndrome; Fructans; Starch; Sugars
• ISSN: 0737-0806
• DOI: 10.1016/j.jevs.2024.105152

•Starch concentration in gastric digesta decreased up to 44 %.•Sucrose was completely cleared from gastric digesta on pasture and with hay.•Fructans disappeared from gastric digesta on pasture and with hay.•Higher evidence for gastric degradation of fibre was in horses on pasture. Concentrations of starch, mono- and disaccharides, fructans, hemicellulose and cellulose were analysed in feed and gastric digesta of horses in relation to acid insoluble ash as a marker indigestible in the stomach. Twenty-four horses were allocated to pasture 24 h/d (PST; n = 4), hay ad libitum (HAY; n = 8), hay ad lib. and oats at 1 g starch/kg body weight (BWT)/meal (OS1; n = 6) and hay ad lib. and oats at 2 g starch/kg BWT/meal (OS2; n = 5). One horse was excluded from the analysis. The horses were fed the ration a minimum of 34 days. Following euthanasia and dissection, digesta was sampled from Pars nonglandularis (PNG) and Pars glandularis (PG). Oat starch concentration in gastric digesta decreased from 309 to 174 g/kg dry matter (DM) in OS1 (44 %-reduction) and from 367 to 261 g/kg DM in OS2 (29 %-reduction) (P < 0.001). Glucose, fructose and sucrose disappeared from gastric digesta distinctly more in PST, HAY and OS1 than in OS2. In PST and HAY, sucrose concentration was completely cleared (P < 0.001). The concentration of fructans was reduced predominantly in PST (84 %-reduction) and HAY (54 %-reduction), mainly in the PNG (P < 0.05). Fructan degradation did not occur in the high-starch diet (OS2). Some evidence for fibre degradation was observed in PST (P < 0.01). Soluble carbohydrates disappear from the stomach dependent on the type of ration, which may lead to changes in the composition of the gastric microbial community and the endogenous response.