The aim of the review is to present mechanisms of digestion in horses through a functional description of the digestive system’s structure with emphasis on nutrient digestibility. In the era of an increasingly intensive and specialised sport usage of horses, also the significance of balancing their dietary nutrient value in accordance with individual requirements of these animals is gaining in importance. At the same time, it is not possible to meet nutritional requirements of a sport horse without knowledge about feed utilisation. In many farm animal species, digestibility is measured postmortem or via complicated and expensive cannulation of the digestive system. In horses, these methods are not applied due to ethical approaches or other limitations (e.g. sport horses); therefore, the importance of marker-based techniques is growing, although not much data is published in the available literature (Sales, 2012). Moreover, in contrast to other non-ruminants, horses are naturally adapted to a constant intake of large quantities of roughages. However, during intensive sport training, they are primarily fed concentrated diets with high amounts of easily digestible, non-structural carbohydrates and reduced amounts of dietary fibre fractions. Therefore, the risk of metabolic diseases and behavioural disorders in the horse increases.
If the inline PDF is not rendering correctly, you can download the PDF file here.
Alexander F. Hickson J.C.D. (1970). The salivary and pancreatic secretions of the horse. In: Physiology of digestion and metabolism in the ruminant A.T. Philipson (ed.). Oriel Press Newcastle Upon Time pp. 375-389.
Barriere Y. Riboulet C. Mechin V. Maltese S. Pichon M. CardinalA. Lapierre C. Lűbberstedt T. Martinant J.P. (2007). Genetics and genomics of lignification in grass cell walls based on maize as model species. Genes Genomes Genomics 1: 133-156.
Bergero D. Peiretti P.G. Cola E. (2002). Intake and apparent digestibility of perennial ryegrass haylages fed to ponies either at maintenance or at work. Livest. Prod. Sci. 77: 325-329.
Bergero D. M i r a g l i a N. Abba C. PolidoriM. (2004). Apparent digestibility of Mediterranean forages determined by total collection of faeces and acid-insoluble ash as internal marker. Livest. Prod. Sci. 85: 235-238.
Bergero D. Prefointaine C. Miraglia N. PeirettiP.G. (2009). A comparison between the 2N and 4N HCl acid-insoluble ash methods for digestibility trials in horses. Animal 3: 1728-1732.
Choct M. Kocher A. (2000). Non-starch carbohydrates: digestion and its secondary effects in monogastrics. Proc. Nutr. Soc. Aust. 24: 31-38.
Clauss M. Schiele K. Ortmann S. Fritz J. CodronD. Hummel J. Kienzle E. (2013). The effect of very low food intake on digestive physiology and forage digestibility in horses. J. Anim. Physiol. Anim. Nutr. 98: 107-118.
Coenen M. Kienzle E. Vervuert I. Zeyner A. (2011). Recent German developments in the formulation of energy and nutrient requirements of horses and the resulting feeding recommendations. J. Eq. Vet. Sci. 31: 219-229.
Coles L.T. Moughan P.J. Darragh A.J. (2005). In vitro digestion and fermentation methods including gas production techniques as applied to nutritive evaluation of foods in the hindgut of humans and other simple-stomached animals. Anim. Feed Sci. Tech. 123: 421-444.
Costa M.C. Arroyo L.G. Allen - Vercoe E. Stampfli H.R. Kim R.T. Sturgeon A Scott Weese J. (2012). Comparison of the fecal microbiota of healthy horses and horses with colitis by high throughput sequencing of the v3-v5 region of the 16S rRNA gene. PLoS ONE 7: e41484. Doi:10.1371/journal.pone.0041484.
Crozier J.A. Allen V.G. Jack N.E. Fontenot J.P. Cochran M.A. (1997). Digestibility apparent mineral absorption and voluntary intake by horses fed alfalfa tall fescue and Caucasian bluestern. J. Anim. Sci. 75: 1651-1658.
Cuddeford D. (2000). Starch digestion in the horse. Advances in Equine Nutrition Vol. II 1998-2000. Kentucky Equine Research pp. 95-104.
Cuddeford D. HughesD. (1990). A comparison between chromium-mordanted hay and acidinsoluble ash to determine apparent digestibility of a chaffed molassed hay/straw mixture. Equine Vet. J. 22: 122-125.
Cuddeford D. Hughes D. (1992). A comparison between the nutritive value of short-cutting cycle high temperature-dried alfalfa and timothy hay for horses Equine Vet. J. 24: 84-89.
Cummings J.H. Macfarlane G.T. (1991). The control and consequences of bacterial fermentation in the human colon. J. App. Bacteriol. 70: 443-459.
Cymbaluk N.F. (1990). Comparison of forage digestion by cattle and horses. Can. J. Anim. Sci. 70: 601-610.
Darlington J.M. HershbergerT.V. (1968). Effect of forage maturity on digestibility intake and nutritive value of alfalfa timothy and orchardgrass by equine. J. Anim. Sci. 27: 572-1576.
De Fombelle A. Veiga L. Drogoul C. Julliand V. (2004). Effect of diet composition and feeding pattern on the prececal digestibility of starches from botanical origins measured with the mobile nylon bag technique in horses. J. Anim. Sci. 82: 3625-3634.
Dyce K.M. Sack W.O. Wensing C.J.G. (2010). Textbook of Veterinary Anatomy. Saunders Elsevier St. Louis pp. 864.
Earing J.E. Cassill B.D. Hayes S.H. Vanzant E.S Lawrence L.M. (2010). Comparison of in vitro digestibility estimates using the DaisyII incubator with in vivo digestibility estimates in horses. J. Anim. Sci. 88: 3954-3963.
Earing J.E. Lawrence L.M. Hayes S.H. Brummer M. Vanzant E. (2013). Digestive capacity in weanling and mature horses. J. Anim. Sci. 91: 2151-2157.
Edouard N. Fleurance G. Martin - Rosset W. Duncan P. Dulphy J.P. GrangeS. Baumont R. Dubroeucq H. Perez - Barberia F.J. Gordon I.J. (2008). Voluntary intake and digestibility in horses: effect of forage quality with emphasis on individual variability. Animal 2: 526-1533.
Faubladier C. Chaucheyras - Durand F. da Veiga L. Jullian d V. (2013). Effect of transportation on fecal bacterial communities and fermentative activities in horses: Impact of Saccharomyces cerevisiae CNCM I-1077 supplementation. J. Anim Sci. 91: 1736-1744.
Fonnesbeck P.V. (1968). Digestion of soluble and fibrous carbohydrate of forage by horses. J. Anim. Sci. 27: 1336-1344.
Frape D. (2004). Equine nutrition and feeding. Blackwell Publishing Ltd. Oxford UK.
FriendD.W. NicholsonJ.W.G. (1965). A harness and feces collection bag for digestibility trials with horses. Can. J. Anim. Sci. 45: 54-57.
Geor R.J. (2010). Digestive strategy and flexibility in horses with reference to dietary carbohydrates. In: The impact of nutrition on the health and welfare of horses Ellis A.D Longland A.C. Coenen M. Miraglia N. (eds). Wageningen Academic Publishers pp. 37-39.
Goachet A.G. Philippeau C. Varloud M. Julliand V. (2009). Adaptations to standard approaches for measuring total tract apparent digestibility and gastro-intestinal retention time in horses in training. Anim. Feed Sci. Tech. 152: 141-151.
GoachetA.G. Varloud M. Philippeau C. Julliand V. (2010). Long-term effects of endurance training on total tract apparent digestibility total mean retention time and faecal microbial ecosystem in competing Arabian horses. Equine Vet. J. Suppl. 38: 387-392.
Goachet A.G. Harris P. Philippeau C. Julliand V. (2014). Effect of physical training on nutrient digestibility and faecal fermentative parameters in Standardbred horses. J. Anim. Physiol. Anim. Nutr. Doi:10.1111/jpn.12177.
Hainze M.T.M. Muntifering R.B. McCall C.A. (2003). Fiber digestion in horses fed typical diets with and without exogenous fibrolytic enzymes. JEVS 23: 111-115.
Heanlein G.F.W. Smith R.C. Yoon Y.M. (1966). Determination of the fecal excretion rate of horses with chromic oxide. J. Anim. Sci. 25: 1091-1095.
Hintz H.F. Cymbaluk N.F. (1994). Nutrition of the Horse. Annu. Rev. Nutr. 14: 243-267.
Hussein H.S. Vogedes L.A. Fernandez G.C.J. Frankeny R.L. (2004). Effects of cereal grain supplementation on apparent digestibility of nutrients and concentrations of fermentation endproducts in the feces and serum of horses consuming alfalfa cubes. J. Anim. Sci. 82: 1986-1996.
Jackson S.G. (1997). The digestive tract of horse - practical considerations. Advances in Equine Nutrition Vol. I 1992-1997. Kentucky Equine Research pp. 1-12.
Jagger S. Wiseman J. Cole D.J.A. Craigon J. (1992). Evaluation of inert markers for the determination of ileal and faecal apparent digestibility values in the pig. Br. J. Nutr. 68: 729-739.
Jansson A. Lindberg J.E. (2012). A forage-only diet alters the metabolic response of horses in training. Animal 6: 1939-1946.
JensenR.B. Brokner C. Knudsen K.E. Tauson A.H. (2010). A comparative study of the apparent total tract digestibility of carbohydrates in Icelandic and Danish warmblood horses fed two different haylages and a concentrate consisting of sugar beet pulp and black oats. Arch. Anim. Nutr. 64: 343-356.
Józefiak D. Sip A. Rawski M. Rutkowski A. Kaczmarek S. Hojberg O. Jensen B.B. Engberg R.M. (2011). Dietary divercin modifies gastrointestinal microbiota and improves growth performance in broiler chickens. Brit. Poultry Sci. 52: 492-499.
Józefiak D. Kierończyk B. Rawski M. Hejdysz M. Rutkowski A. Engberg R.M. Højberg O. (2014). Clostridium perfringens challenge and dietary fat type affect broiler chicken performance and fermentation in the gastrointestinal tract. Animal Doi:10.1017/ 7151731114000536
Kienzle E. (1994). Small intestinal digestion of starch in the horse. Rev. Med. Vet. 145: 199-204.
Kotb A.R. Luckey T.D. (1972). Markers in nutrition. Nutr. Abs. Rev. 42: 813-845.
Kronfeld D.S. (1998). A practical method for ration evaluation and diet formulation; an introduction to sensitivity analysis. Advances in equine nutrition. Equine Nutr. Conf. for Feed Manufactures 27-28.04.1998 Lexington Kentucky USA Kentucky Equine Research Inc. pp. 77-88.
Kutzner - MulliganJ. EisemannJ. Siciliano P. Smith J. HewittK. Sharlette J. Pratt - Phillips S. (2013). The effect of different feed delivery methods on time to consume feed and the resulting changes in postprandial metabolite concentrations in horses. J. Anim.Sci. 91: 3772-3779.
Lawrence L. (2008). Nutrient needs of performance horses. R. Bras. Zootec. 37: 206-210.
Lindeboom N. Chang P.R. Tyler R.T. (2004). Analytical biochemical and physicochemical aspects of starch granule size with emphasis on small granule starches: a review. Starch - Stärke 56: 89-99.
Lopes M.A.F. Pfeiffer C.J. (2000). Functional morphology of the equine pelvic flexure and its role in disease. A review. Histol. Histopathol. 15: 983-991.
Mackenthun E. Coenen M. Vervuert I. (2013). Effects of Saccharomyces cerevisiae supplementation on apparent total tract digestibility of nutrients and fermentation profile in healthy horses. J. Anim. Physiol. Anim. Nutr. 97: 115-120.
Mackie R.I. Wilkins C.A. (1988). Enumeration of anaerobic bacterial microflora of the equine gastrointestinal tract. Appl. Environ. Microbiol. 54 p. 2155.
Martin R.G. McMeniman N.P. Dowsett K.F. (1989). Pasture intakes of pregnant and lactation mares in south-east Queensland. Proc. ENPS. 11: 176-178.
Mayes R.W. Lamb C.S. Colgrove P.M. (1986). The use of dosed and herbage n-alkanes as markers for the determination of herbage intake. J. Agr. Sci. 107: 161-170.
Meyer H. Radicke S. Kienzle E. WilkeS. Kleffken D. Illenseer M. (1993). Investigations on preileal digestion of oats corn and barley starch in relation to grain processing. In: 13th Equine Nutrition and Physiology Proceedings. Equine Nutrition and Physiology Society Gainsville Florida pp. 92- 97.
Milinovich G.J. Trott D.J. BurrelP.C. Croser E.L. Al Jassim R.A.M. Morton J.M. van Eps A.W. Pollitt C.C. (2007). Fluorescence in situ hybridization analysis of hindgut bacteria associated with the development of equine laminitis. Environ. Microb. 9: 2090-2100.
Miraglia N. Bergero D. Bassano B. Tarantola M. Ladetto G. (1999). Studies of apparent digestibility in horses and the use of internal markers. Livest. Prod. Sci. 60: 21-25.
Moeller B.A. McCall C.A. Silverman S.J. (2008). Estimation of saliva production in cribbiting and normal horses. JEVS 28: 85-90.
Moore B.E. Dehority B.A. (1993). Effects of diet and hindgut defaunation on diet digestibility and microbial concentrations in the cecum and colon of the horse. J. Anim. Sci. 71: 3350-3358.
Moore J.N. Melton T. Carter W.C. Wright A.L. Smith M.L. (2001). A new look at equine gastrointestinal anatomy function and selected intestinal displacements. AAEP Proc. 47: 53-60.
Myers W.D. LuddenP.A. NayigihuguV. Hess B.W. (2004). Technical Note: A procedure for the preparation and quantitative analysis of samples for titanium dioxide. J. Anim. Sci. 82: 179-183.
Nagpal R. Puniya A.K. Griffith G.W. Gujnan G. Punija M. Sehgal J.P. Singh K. (2009). Anaerobic rumen fungi: potential and applications. NBAIM 2: 375-393.
Nielsen B.D. O ’ Connor - Robinson C.I. Spooner H.S. SheltonJ. (2010). Glycemic and insulinemic responses affected by age of horse and method of feed processing. J. Equine Vet. Sci. 30: 249-258.
Nomina Anatomica Veterinaria (2002). PWRiL Warsaw pp. 357.
Nørgaard P. Husted S. Ranvig R. (2004). Effect of supplementation with whole wheat or whole oat grains on the dimensions of faeces particles from lambs. J. Anim. Feed Sci. 13: 175-460.
O’Keefe N.M. Gray K.A. McMeniman N.P. (1998). An in vitro system to determine the digestibility of feeds for horses. Anim. Prod. Aus. 22 p. 353.
O’Neill H.M. Smith J. Bedford M. (2014). Multicarbohydrase enzymes for non-ruminants. Asian Australas. J. Anim. Sci. 27: 290-301.
Ordakowski A.L. Kronfeld D.S. Holland J.S. Hargreaves B.J. Gay L.S. Harris P.A. Dove H. Sklan D. (2001). Alkanes as internal markers to estimate digestibility of hay or hay plus concentrate diets in horses. J. Anim. Sci. 79: 1516-1522.
Orton R.K. Hume I.D. Leng R.A. (1985). Effects of exercise and level of dietary protein on digestive function in horses. Equine Vet. J. 17: 386-390.
Ott E.A. Barnett R.D. (1984). Digestibility of triple recleaned northern oats and Florida 502 oats by horses. Department of Animal Science Research Report AL-1984-11 June 1984 Florida Agricultural Experiment Station Gainesville USA Florida.
Pagan J.D. (1997). Forage for horses: more than just a filler. Advances in Equine Nutrition I 1992-1997. Kentucky Equine Research pp. 13-28.
Pagan J.D. (2008). Nutrient requirements: applying the science. Advances in Equine Nutrition IV. 2004-2008. Kentucky Equine Research pp. 1-6.
Pagan J.D. Harris P. Brewster - Barnes T. Duren S.E. Jackson S.G. (1998). Exercise affects digestibility and rate of passage of all-forage and mixed diets in thoroughbred horses. J. Nutr. 128: 2704-2707.
Peiretti P.G. Miraglia N. Bergero D. (2011). Effects of oat or corn on the horse rations digestibility. JFAE 9: 268-270.
Potter G.D. Arnold F.F. Householder D.D. Hansen D.H. BrownK.M. (1992). Digestion of starch in the small or large intestine of the equine. Pferdeheilkunde Sonderheft pp. 107-111.
Ragnarsson S. Jansson A. (2011). Comparison of grass haylage digestibility and metabolic plasma profile in Icelandic and Standardbred horses. J. Anim. Physiol. Anim. Nutr. 95: 273-279.
Reece W.O. (2009). Functional anatomy and physiology of domestic animals. Wiley-Blackwell Iowa USA.
Rodiek A.V. StullC.L. (2007). Glycemic index of ten common horse feeds. J. Equine Vet. Sci. 2: 205-211.
Sales J. (2012). A review on the use of indigestible dietary markers to determine total tract apparent digestibility of nutrients in horses. Anim. Feed Sci. Technol. 174: 119-130.
Sarkijarvi S. Saastamoinen M.T. Kajan T o L. (2000). Effect of different cereal grain on equine diet digestibility. Advances in the Horse Nutrition II 1998-2000. Kentucky Equine Res. pp. 113-114.
Schaafstra F.J.W.C. van Doorn D.A. Schonewille J.T. van Riet M.M.J. Visser P. Hendriks W.H. (2012). Evaluation of ADL AIA and TiO2 as markers to determine apparent digestibility in ponies fed increasing proportions of concentrate. In: Forages and grazing in horse nutrition M. Saastamoineni (ed.). EAAP publication 132 Wageningen Academic Publishers pp. 121-122.
Schneeman B. (1998). Dietary fiber and gastrointestinal function. Nutr. Res. 18: 625-632.
Schneider B.H. Flatt W.P. (1977). The evaluation of feeds through digestibility experiments.Anim. Feed Sci. Technol. 2: 102-104.
Sneddon J.C. Argenzio R.A. (1998). Feeding strategy and water homeostasis in equids: the role of the hind gut. J. Arid Environ 38: 493-509.
St . Pierre B. de la Fuente G. O ’ Neill S. Wright A.G. AlJassim R. (2012). Analysis of stomach bacterial communities in Australian feral horses. Mol. Biol. Rep. 40: 369-376.
Swinney D.L. Potter G.D. Greene L.W. SchumacherJ. Murray - Gerzik M. Goldy G. (1995). Digestion of fat in the equine small and large intestine. Proc. 14th Equine Nutr. Physiol. Soc. pp. 30-35.
Tagaki H. Hashimoto Y. YonemochiC. Ishibashi T. AsaiY. Watanabe R. (2003) Digestibility of cereals oil meals brans and hays in thoroughbreds. J. Equine Sci. 14: 199-124.
Tilley J.M.A. Terry R.A. (1963). A two-stage technique for the in vitro digestion of forage crops. J. Brit. Grassland Soc. 18: 104-111.
Treverton B. Friend M.A. (2000). Development of an in vitro technique for estimating the digestibility of horse feeds. Asian-Aus. J. Anim. Sci. 13 Supplement A p. 62.
Van BusselW. Kerkhof F. van Kessel T. Lamers H. Nous D. Verdonk H. Verhoeven B. (2010). Accurate determination of titanium as titanium dioxide for limited sample size digestibility studies of feed and food matrices by inductively coupled plasma optical emission spectrometry with real-time simultaneous internal standardization. Atom. Spectrosc. 31: 81-88.
Visser P. (2010). A comparison between the measurement of the apparent digestibility coefficient in ponies based on the total faecal collection method and on the dietary marker titanium dioxide. Doctoral Thesis. Faculty of Veterinary Medicine Theses Netherlands Utrecht University.
WilmanD. AdesoganA. (2000). A comparison of filter bag methods with conventional tube methods of determining the in vitro digestibility of forages. Anim. Feed Sci. Technol. 84: 33-47.