Digestion in horses involves a complex process that begins in the mouth and extends through the gastrointestinal tract, including the stomach, small intestine, and large intestine. Horses are non-ruminant herbivores with a digestive system adapted to a high-fiber diet primarily composed of forage. The process starts with mastication, where food is mechanically broken down by the teeth and mixed with saliva to aid in swallowing. In the stomach, enzymatic digestion begins, but the majority of nutrient absorption occurs in the small intestine, where carbohydrates, proteins, and fats are broken down. The large intestine, including the cecum and colon, plays a significant role in fermenting fibrous plant material with the aid of a diverse microbial population, producing volatile fatty acids that serve as an energy source. This page aggregates peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and nutritional aspects of equine digestion, as well as the impact of diet and management practices on digestive health.
Pulse RE, Baker JP, Potter GD.Three mature Thoroughbred geldings were used in duplicated trials conducted before and after cecal fistulation to determine the effects of the fistulation on nutrient digestion and indicator (Cr2O3 and polyethylene) retention time. There were significant increases (P<.01) in crude fiber and ether extract digestion following fistulation, while dry matter, gross energy, and crude protein digestibilities were not changed significantly. Retention times of Cr2O3 and polyethylene were increased significantly (P<-01 and P<.05, respectively) following fistulation. There were no significant di...
Hintz HF, Hogue DE, Walker EF, Lowe JE, Schryver HF.Eleven ponies were fed diets containing 1:0, 3:2 or 1:4 forage-grain ratios for 30 days. Animals were killed 4 hr. after feeding and the entire digestive tracts were removed and segments isolated. Digestion coefficients were calculated for dry matter, protein, available carbohydrate (ACHO) and neutral detergent fiber (NDF) by Cr2O3-nutrient ratio for seven segments of the gut.
The major site of ACHO and protein digestion was prececal; whereas, the major sites of NDF digestion were the colon and cecum regardless of the hay:grain ratio. Therefore the relative importance of digestion in the lo...
Slade LM, Hintz HF.A comparative digestion trial was conducted between horses, ponies, rabbits and guinea pigs. Alfalfa and alfalfa-grain diets were compared.
Although there was a trend for ponies to be more efficient than horses in digesting proximate principles of both diets, differences were not significant. Digestibility coefficients for crude fiber and energy were lowest in rabbits. The digestion of nitrogen-free extract (NFE) was greatest in guinea pigs, whereas digestion of crude protein was lowest.
Horses, ponies and rabbits digested organic matter, NFE and energy in the mixed ration more efficient...
Davies ME.This research article investigates the role of colon liquor – fluid from the colon of a horse – in cultivating cellulolytic bacteria, which break down cellulose. The researchers aim to [...]
A method of preparing hay for feeding to a horse includes placing the hay within the upper compartment of a vessel containing a mesh grid that divides the interior of the vessel into upper and lower compartments, and introducing steam into the lower compartment by means of an atomiser containing a plurality of fins.
A method of preparing hay for feeding to a horse includes placing the hay within the upper compartment of a vessel containing a mesh grid that divides the interior of the vessel into upper and lower compartments, and introducing steam into the lower compartment by means of an atomiser containing a plurality of fins.
Silva AH, Lucena JEC, Taran FMP, Cunha DS, Almeida JAT, Lima RS, Dias WS, Santiago JM.This study aimed to compare the digestibility of tropical grasses by horses by the in vivo method using mobile nylon bags with the in vitro digestibility method using horse feces as a source of inoculum. Five horses were used in a 2 × 5 factorial design with randomized blocks featuring two methods (in vivo and in vitro) and five grasses: Tifton 85 hay (Cynodon spp.), sixweeks threeawn grass (Aristida adsencionis, Linn), Alexandergrass (Brachiaria plantaginea (Link) Hitchc.), capim-de-raiz (Chloris orthonoton, Doell), and Sabi grass (Urochloa mosambicensis). No difference (P>0.05) was f...
Bachmann M, Schusser GF, Wensch-Dorendorf M, Pisch C, Bochnia M, Santo MM, Netzker H, Woitow G, Thielebein J, Kesting S, Riehl G, Greef JM....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 sample...
Nogacka AM, García A, de Los Reyes-Gavilán CG, Arboleya S, Gueimonde M.Horses are hindgut fermenters that harbor a complex intestinal microbiota (IM) which provides key enzymes aiding in the breakdown of complex carbohydrates present in their herbivorous diet. Therefore, these animals are deeply dependent on their IM for digestion and nutrition. Consequently, IM imbalances may result in alteration of fermentation patterns with impact on the animal health and the risk of disease. In this context, strategies for assisting the maintenance of a healthy IM in horses are of interest. However, there is limited research concerning the use of probiotics to improve hindgut...
LeCompte Lazić RA, Nielsen BD, Robison CI, Schott HC, Herdt TH, Larson CK.The 2007 Horse NRC reduced cobalt (Co) requirements from 0.1 ppm to 0.05 ppm in dietary dry matter, though preliminary research suggested increasing dietary-Co enhanced fiber digestion in horses. This study aimed to evaluate fiber digestion with varying dietary Co amounts, as well as to compare serum Co concentrations with dietary Co content. Four geldings (mean body weight [BW] 503 ± 37 kg) were studied in a 4 × 4 Latin square design consisting of four 5-week periods, each comprising a 2-week washout phase followed by a 3-week treatment phase. Supplementing 0.0, 5.6, 16.8, or 28.0 mg of Co ...
Webster AP, Price T, Ingersoll T, Suagee-Bedore JK, White RR.Our objectives were to use a quantitative literature review to explore dietary and feed factors influencing apparent total-tract digestibility of dry matter (DMD), crude protein (CPD), neutral detergent fiber (NDFD), ether extract (EED), non-structural carbohydrates (NSCD), non-fiber carbohydrates (NFCD), and residual organic matter (rOMD) in equine diets, and to assess their contributions to digestible energy (DE) supplies. Data from 54 studies were modeled using linear mixed-effect regressions, with publication as a random effect to account for study variability. For each nutrient, five mode...
Pipereau K, Trably E, Santa-Catalina G, García-Bernet D, Carrere H.This study focuses on thermal and non-thermal effects of microwave pretreatment on horse dung as indigenous inoculum before xylose and wheat straw fermentation, emphasizing metabolite production and microbial community changes. Two horse dung microwave pretreatments (MW40°C and MW95°C) were compared with a conventional thermal pretreatment (Th95°C) and an unpretreated condition (Ctrl). Microwave heating pretreatment (MW95°C) leads to similar production as a conventional thermal pretreatment (Th95°C) for xylose and wheat straw fermentation while MW40°C treatment was similar to the control...
Finno CJ.Nutrigenomics defines the interaction between the nutrients in our food and the genes in our body. Examples from human medicine of diseases and associated genes include lactose intolerance (genetic variants in LCT lactase), hypercholesteremia (low density lipoprotein receptor, LDLR) and caffeine sensitivity (adenosine A2A receptor, ADORA2A). In horses, examples include Hyperkalemic Periodic Paralysis (HYPP), where clinical signs of disease are managed through maintaining a diet low in potassium and Polysaccharide Storage Myopathy Type 1 (PSSM1), where low starch and high fat diets are recommen...
Huang X, Li Q, Li X, Li C, Li J, He L, Jing H, Yang F, Li X.China's equine industry has shifted from traditional rough grazing to modern intensive farming, expanding the roles of horses into eventing, leisure, tourism, and meat and dairy production. Concurrently, equine nutrition has evolved from a forage-based diet to a more diverse regimen incorporating grain supplements to meet the heightened energy demands of intensive farming. However, nutrient digestibility and glycemic response vary considerably based on grain type, starch content, composition, and structural properties. Optimal grain selection is therefore essential for energy supplementation a...
Li Y, Lan Y.The gut microbial importance and its crucial roles in host digestion, immunity, and metabolism have received widely attention. Horses, especially indigenous varieties such as Mongolian horses (MGH) and Guizhou horses (GZH), have not received sufficient attention, and the characteristics of their gut microbiota are still unclear. For this purpose, we collected faecal samples from eight MGH and eight GZH to compare their gut microbial differences using amplicon sequencing. The results of alpha diversity analysis indicated that the gut bacterial diversity and gut fungal abundance in GZH were sign...
Jing H, Liu P, Zheng S, Cao K, Li X.Total Mixed Ration (TMR) is recognized for its balanced nutritional composition, improved feed efficiency, enhanced animal production, and stabilization of the gastrointestinal microbiome. It has been extensively implemented in intensive ruminant farming, particularly for cattle and sheep, with demonstrated positive outcomes. However, its effects on the nutritional health of non-ruminant herbivores, such as horses, remain insufficiently investigated. This study aims to evaluate the comparative effects of TMR feeding versus conventional feeding practices in Akhal-Teke horses while maintaining i...
Andueza D, Martin-Rosset W.The nutritive value of forage for horses is closely dependent on the digestibility of organic matter (OMD), which is typically measured in vivo. Researchers have developed a variety of prediction methods to estimate the digestibility value of hay. In ruminants, pepsin-cellulase degradability, expressed as dry matter enzymatic degradability (dCS) and organic matter enzymatic degradability (dCO), is a commonly employed method for predicting OMD in forage types. The objective of this study was to evaluate the feasibility of predicting the dry matter digestibility (DMD), OMD, energy digestibility ...
Bachmann M, Bochnia M, Wensch-Dorendorf M, Glatter M, Schäfer S, Simroth K, Greef JM, Zeyner A.Feed intake and digestibility are important indicators for sufficient nutrient supply, but they can be assessed only to a limited extent in horses on pasture. In horses, feed intake is embedded in a complex behavioural pattern of searching, selecting, chewing and almost constant movement called foraging. The objectives of this study were to estimate organic matter intake (OMI) and organic matter digestibility (OMD) in six horses, 24 h/day on pasture, based on plant alkanes and synthetic n-hexatriacontane (C) excretion. A multi-compartmental model was fitted to the marker excretion and the C m...
Li M, Xu Z, Sun L, Cheng Z, Yu Y, Chen Y, Li F, Zang C.This study aimed to investigate the effects of dietary NFC/NDF ratio on nutrient apparent digestibility, fecal fermentation parameters, microbial diversity, and plasma metabolomics in Yili horses. Twenty-four healthy Yili horses with similar body weights (406 ± 22.73 kg) were divided into four groups, each with six replicates: the Control Group (CG), Low-NFC Group (LG), Medium-NFC Group (MG), and High-NFC Group (HG). The experiment lasted 52 d, comprising a 7-day adaptation period and a 45-day experimental period. Total fecal collection was conducted from days 41 to 45 to calculate nutrient a...
Nilsson E, Moazzami AA, Lindberg JE, Jansson A.Feeding a high amount of starch-rich grains is common practice for performance horses even though the horse has evolved to eat a grass based, i.e. low starch diet. To our knowledge, there are no studies using metabolomics to investigate the effects of a high-starch diet in horses. In this study we investigated differences in the plasma metabolic profile of 6 Standardbred horses fed a no-starch, forage-only (F) diet or a high-starch forage-concentrate (FC) diet for 29 days, respectively in a cross-over design. Postprandial plasma samples were collected on the morning of day 25 of each dietary ...
Mańkowska A, Dobraczyńska BM, Szewczak J, Chodup Z, Radzanowski B, Matychyn I, Witkowska D.Cultivated carrot ( subsp. ) is a valuable component of equine diets due to its high β-carotene content (a precursor of vitamin A) and desirable sensory properties. However, its use may be limited by short shelf life, susceptibility to spoilage, and firm texture, which can be challenging for horses with dental problems. This study aimed to evaluate horses' preferences for different physical forms of carrots. Twenty-one leisure horses aged 3-22 years were individually evaluated in a free-choice test. Each horse was simultaneously offered equal portions (150 g) of five carrot forms: raw, grated...
Franzan BC, da Silva Coelho I, Ramos EM, de Souza ARP, de Almeida FQ, Silva VP.This study aimed to investigate the gradual adaptation of the fecal bacterial community and in vitro fermentative capacity of horses fed a complete extruded diet (CED). Twelve geldings weighing 370 kg were removed from a native pasture and fed coastcross hay (Cynodon spp) for 7 days. In the second week, horses were assigned to two groups: one group was fed exclusively with coastcross hay (HAY) for 28 days and the other group fed with weekly increases of CED (30%, 60%, and 100%) to replace HAY. Fecal samples were collected on Days 7, 14, 21, and 28 for microbiota and in vitro fermentati...
Wei L, Wei J, Liu X, Chen W, Wang C, Khan MZ, Zhang Z.Donkeys () remain nutritionally understudied despite their critical roles in agriculture across developing regions, with current feeding practices inappropriately extrapolating horse standards without accounting for species-specific digestive physiology. No comprehensive synthesis has integrated how dietary modifications systematically alter gut microbial communities to drive measurable health outcomes in donkeys, preventing development of evidence-based feeding strategies. This review critically synthesizes current evidence on donkey nutritional requirements and gut microbiota dynamics to est...
Daniels S, Martin S, Harris P, Moore-Colyer M.The in vitro gas production system (GPS), developed to estimate degradation of ruminant feedstuffs, has been adapted for equine use. This study aimed to characterise the bacterial community profile and metabolome of donor faeces and faecal inoculum within the GPS when fermenting the same diet as faecal donors. Six Welsh ponies on identical diets were faecal donors with samples collected for microbiome profiling and system inoculation. Gas production (manual pressure transducer technique) was performed for 156 h with 2 replicate bottles from each donor harvested at 8,20,28 and 36 h. Faecal an...
Ivanković A, Pećina M, Bittante G, Amalfitano N, Konjačić M, Kelava Ugarković N.Local horse breeds, particularly cold-blood types, are often marginalized in economic and social contexts, primarily due to the neglect of their economic, genetic, and cultural potential, as well as their role in preserving the identity of rural areas, local communities, and ecosystems. The valorization of these breeds is a crucial prerequisite for their economic repositioning. The Croatian Posavina horse is a local breed, well adapted to harsh, extensive production systems. Its sustainability is achieved through pasture-based meat production, primarily targeting foreign European markets. Ensu...
Prasad S, Patel B, Kumar P, Lall R.Postbiotics, which are preparations of inanimate microorganisms and their components, have emerged as a promising functional ingredient in animal health and nutrition. Postbiotics are primarily composed of microbial cell fractions, metabolites, enzymes, vitamins, polysaccharides, and short-chain fatty acids. Unlike probiotics, postbiotics do not contain live microorganisms, which strengthens their greater stability and safety in feed/food formulations. Postbiotics offer several beneficial effects, including antioxidant, anti-inflammatory, immune-modulatory, and antimicrobial actions. They enha...
Hart KJ, Hegarty MJ, Hart EH.It is more evident that horse health is linked to the gastrointestinal tract and microbial community structure (MCS) as affected by diet. There are many marketed feeds available to enhance nutrition for horses, however the effects of these feeds on hindgut MCS are largely unknown. Objective: The aim was to test the effect of a complementary forage feed (FF) on the fermentation profile and MCS in contrasting basal diets. Methods: A 2×2 factorial design was used to assess the effect of basal diet, forage only (FOR) or forage/concentrate (MIX), and presence/absence of FF on fermentation paramete...
Smith MA, Ripley N, Gravatte H, Nielsen MK.With rising anthelmintic resistance in adult cyathostomins, the most pervasive equine parasites, the need to assess larvicidal efficacy has increased, yet available methods remain limited. Encysted larvae are quantified using mucosal digestion, wherein a 5% subsample of intestinal mucosa is processed, and a 2% aliquot is counted for early third stage (EL3) and late third stage/mucosal fourth stage (LL3/L4) larvae. This method is imprecise and post-treatment larval differences are often not observed. The following study aimed to assess standard and modified protocol precision and sensitivity. I...
Wei J, Wei L, Ullah A, Geng M, Zhang X, Wang C, Khan MZ, Wang C, Zhang Z.Herbivorous animals rely on complex gastrointestinal systems and microbial communities to efficiently digest plant-based diets, extract nutrients, and maintain health. Recent advances in metagenomic technologies have enabled high-resolution, culture-independent analysis of gut microbiota composition, functional potential, and host-microbe interactions, providing insights into microbial diversity across the herbivore digestive tract. This review summarizes key findings on the gastrointestinal microbiota of herbivores, focusing on ruminant foregut and non-ruminant hindgut fermentation. Ruminants...
Park C, Jeong C, Son M, Yi J.This study evaluated a 181-day finishing system for horses entering the Korean meat chain by comparing retired thoroughbred geldings and Belgian-crossbred geldings under identical management and an ad libitum forage-based total mixed ration. Ten geldings ( = 5 per group) were individually housed, with body weight and feed intake recorded monthly. After slaughter, carcass traits and meat quality grade were assessed, and longissimus thoracis et lumborum samples were analyzed for proximate composition. Belgian-crossbreds consumed more dry matter (18.68 vs. 13.60 kg DM/day), corresponding to 2.3% ...
Boshuizen B, Willems M, De Maré L, Hosotani G, De Oliveira JE, Horemans B, Vidal Moreno De Vega C, Verdegaal EJMM, Delesalle C.Aleurone, a bioactive wheat bran component, has been shown to modulate host metabolism and gut microbiota, but its effects across different compartments of the equine gastrointestinal (GI) tract remain unclear. In this study, we aimed to characterize aleurone-derived metabolite profiles using an fermentation model with digesta from three equine GI compartments (jejunum, cecum, and colon). Unassigned: Three substrates (control feed, aleurone-containing feed, and pure aleurone) were fermented over 72 h, and targeted metabolomics was performed on 38 metabolites. Unassigned: Significant substrate...
Tanabe T, Matsui A, Tominari M, Ueda K, Mitani T, Kawai M.We investigated the changes in the forage and nutrient intake of thoroughbred foals on pastures with whole-day stocking with age. Twelve thoroughbred foals were used and were allowed to graze on a pasture for 21 h/day from June to September. All foals were weaned just before 5 months of age. The pasture intake of the foals was measured using the double-indicator method. During the suckling period, the total voluntary dry matter intake (VDMI) of the pasture for foals was higher at 4 months (2.1 kgDM/day) than at 2 months (1.3 kgDM/day). However, VDMI of pastures per body weight (%BW) for foal...
Long JF, Hutton R, Abrams A, Duberstein JA, Duberstein KJ.Bermudagrass (Cynodon dactylon L.) is a common forage in the southeastern United States but remains controversial in equine diets due to reported associations with impaction colic. Reduced fiber digestibility has been proposed as a contributing factor, however differences in mastication of fine-stemmed bermudagrass hay have not been studied and may play a role in digestive disturbances. Objective: To compare chewing characteristics, including chews per unit weight and chews per minute, in horses consuming bermudagrass hay compared to other common hay types. Methods: Two studies were conducted....
DiSilvestro AN, Wesolowski LT, Williams BD, Warren LK, Athrey G, White-Springer SH.Energy-dense feeds commonly provided to equine athletes may be high in starch, which alter gastrointestinal microbiota and could promote systemic inflammation. Objective: To test the hypothesis that exercise-induced inflammation would be greater in horses receiving a starch- versus fiber-based concentrate. Methods: Quarter Horses (mean±SD 16±1mo; 337±30kg) received either a fiber-based control (CON; 7 fillies, 8 geldings) or an isocaloric, isonitrogenous starch concentrate (STARCH; 8 fillies, 7 geldings) for 24d. Fecal metagenomics were evaluated on d0 and 21. Blood inflammatory mediators w...
Moore-Colyer M, Harris P, Daniels S.Haylage is widely fed to all categories of stabled horses across Europe and New Zealand. Haylage can vary from high energy nutrient dense forage to low energy highly fibrous fodder, yet little is known about the impact different haylages have on metabolism in horses. This study provides the first direct comparison of feeding four different haylages: early cut (Lolium multiflorum), later cut (Lolium perenne) rye grass (R1 and R2); early and late cut meadow grass (M1 and M2), on urinary and faecal metabonomics, in ponies at maintenance. Using replicated Latin Square design, eight individually ho...
Wu Y, Ma Y, Zan Y, Bai X, Li J, Li H.The equine gastrointestinal microbiome plays an essential role in digestion, energy metabolism, immune regulation, and maintenance of intestinal homeostasis. Increasing evidence suggests that microbial-derived metabolites provide a functional link between diet, the microbiome, and host physiology. This narrative review summarizes current knowledge on how dietary factors, including structural carbohydrates, non-structural carbohydrates, protein, and lipids, influence microbial function and metabolite production in horses. Relevant publications available up to June 2026 were identified through s...
