Grass hay is a primary forage source for horses, providing essential fiber necessary for healthy digestive function. It is composed of various grass species that are harvested, dried, and stored for equine consumption. Grass hay is an integral part of a horse's diet, offering nutrients such as carbohydrates, proteins, vitamins, and minerals. The nutritional content of grass hay can vary depending on factors such as grass species, soil quality, and harvest timing. Common types of grass hay include timothy, orchard, and brome. This page compiles peer-reviewed research studies and scholarly articles that examine the nutritional composition, digestibility, and effects of grass hay on equine health and performance.
Guerrero JLS, Brito PHS, Ferreira MA, Arantes JA, Rusch E, Oliveira BVDS, Velasco-Bolaños J, Carregaro AB, Dória RGS.The prevalence of gastric disorders in high-performance horses, especially gastric ulceration, ranges from 50 to 90%. These pathological conditions have negative impacts on athletic performance and health. This study was designed to evaluate changes in gastric pH during a 24 h period and to compare gastrin concentrations at different time points in horses undergoing general inhalation anesthesia and dorsal recumbency. Twenty-two mixed-breed mares weighing 400 ± 50 kg and aged 8 ± 2 years were used. Of these, eight were fasted for 8 h and submitted to 90 min of general inhalation anesthesia i...
Halpin MY, Drouillard JS, Fehlberg LK, Douthit TL, Lattimer JM.To assess the impact of protein on fermentation by equine cecal microorganisms, cecal fluid from 4 cecally cannulated horses was used to inoculate fermentation bottles containing buffer, forage, and supplemental protein. In experiment 1, sodium caseinate (SC) provided 0, 0.5%, 1%, 2%, or 4% additional crude protein (CP) to bottles containing alfalfa or native warm-season prairie grass hay. Bottles were equipped with continuous gas pressure monitors and placed into a shaking incubator for 48 hours at 39°C. Cultures with alfalfa had greater (P < .0001) in vitro dry matter disappearance (IVDMD...
Schaafstra FJWC, van Doorn DA, Schonewille JT, Roelfsema E, Westermann CM, Dansen O, Jacobs M, Lee JY, Spronck EA, Blok MC, Hendriks WH.Exercise and physical training are known to affect gastrointestinal function and digestibility in horses and can lead to inaccurate estimates of nutrient and energy digestibility when markers are used. The effect of exercise on apparent nutrient digestibility and faecal recoveries of ADL and TiO2 was studied in six Welsh pony geldings subjected to either a low- (LI) or high-intensity (HI) exercise regime according to a cross-over design. Ponies performing LI exercise were walked once per day for 45 min in a horse walker (5 km/h) for 47 consecutive days. Ponies submitted to HI exercise were gra...
Dittmann MT, Kreuzer M, Runge U, Clauss M.Horses achieve a higher degree of particle size reduction through ingestive mastication than functional ruminants. We characterized mastication using chew-monitoring halters (RumiWatch) in six domestic horses, cattle, and Bactrian camels each. All animals were offered grass hay of the same batch for 15 min. In cattle and camels, measurements were continued after eating until rumination was observed. Except for one horse, 96% of the horses' ingestive mastication data were identified as "rumination" by the proprietary RumiWatch algorithm, whereas ingestion and rumination by cattle and camels wer...
Hassel DM, Spier SJ, Aldridge BM, Watnick M, Argenzio RA, Snyder JR.To determine the effects of two diets and water supplies on intestinal pH and mineral concentrations in the colon of horses, and to identify whether differences in these parameters exist in horses with and without enterolithiasis, surgical fistulation of the right dorsal colon was performed in six adult horses, three with and three without enterolithiasis. Each horse underwent four feeding trials: grass hay and untreated water, alfalfa hay and untreated water, grass hay with filtered/softened water, and alfalfa hay with filtered/softened water. Samples of colonic contents were analyzed for pH,...
Vervuert I, Bothe C, Coenen M.This study was conducted to evaluate the effects of different barley processing techniques on the glycaemic and insulinaemic responses in horses. It was hypothesized that the changes in pre-caecal starch digestibility caused by barley processing would affect metabolic responses. Six horses were fed in random order: whole (WB), finely ground (FGB), steamed (SB), steam-flaked (SFB) and popped barley (PB). The total barley intake was adjusted to 630 g starch/horse/day (1.2-1.5 g starch/kg BW/day). During a 10-day stabilization period, the horses also received 6 kg grass hay/horse/day. On the bloo...
Ralston SL.Horses suffering from trauma, sepsis, and severe burns need 12% to 16% of protein (dry matter basis) in their diet. Since reduced appetite may be a problem, relatively energy dense (greater than 2 Mcal DE/kg) feeds should be offered. In hepatic failure, maintenance protein requirements (8% on a dry matter basis for adult horses) should be met with feeds that are high in short branched-chain amino acids and arginine but low in aromatic amino acids and tryptophan (for example, milo, corn, soybean, or linseed meal) in addition to grass hay. Vitamins A, C, and E should also be supplemented. In cas...
Bertone AL, Ralston SL, Stashak TS.Each of 3 digestion trials (3 forage diets) was performed on 2 groups of horses 6 to 12 months after sham operation (group 1; n = 3) or large-colon resection (group 2; n = 5). Diets were alfalfa pellets, alfalfa hay, and grass hay. Feed and fecal analyses were performed to determine apparent digestion of dry matter, organic matter, and crude protein and true digestion of dry matter, organic matter, crude protein, total plant cell wall, hemicellulose, cellulose, and lignin. Additional fecal and metabolic variables determined were percentage of fecal water, total fecal water, metabolic organic m...
Ralston SL, Sullins KE, Stashak TS.The effect of 60% resection of the large colon vs ischemic insult without resection on the ability of horses to digest grass hay was investigated. Digestion trials were performed on 9 horses before surgery (base line) and 3 weeks, 6 weeks, and 6 months after surgery. The percentage of apparent digestion of crude protein, crude fiber, nitrogen-free extract, calcium, phosphorus, magnesium, manganese, copper, and zinc was calculated. Horses that had resection (n = 5) had decreased apparent digestion of crude protein, crude fiber, and phosphorus 3 weeks after surgery, compared with those in horses...
Dittmann MT, Kreuzer M, Runge U, Clauss M.Horses achieve a higher degree of particle size reduction through ingestive mastication than functional ruminants. We characterized mastication using chew-monitoring halters (RumiWatch) in six domestic horses, cattle, and Bactrian camels each. All animals were offered grass hay of the same batch for 15 min. In cattle and camels, measurements were continued after eating until rumination was observed. Except for one horse, 96% of the horses' ingestive mastication data were identified as "rumination" by the proprietary RumiWatch algorithm, whereas ingestion and rumination by cattle and camels wer...
Schaafstra FJWC, van Doorn DA, Schonewille JT, Roelfsema E, Westermann CM, Dansen O, Jacobs M, Lee JY, Spronck EA, Blok MC, Hendriks WH.Exercise and physical training are known to affect gastrointestinal function and digestibility in horses and can lead to inaccurate estimates of nutrient and energy digestibility when markers are used. The effect of exercise on apparent nutrient digestibility and faecal recoveries of ADL and TiO2 was studied in six Welsh pony geldings subjected to either a low- (LI) or high-intensity (HI) exercise regime according to a cross-over design. Ponies performing LI exercise were walked once per day for 45 min in a horse walker (5 km/h) for 47 consecutive days. Ponies submitted to HI exercise were gra...
Hassel DM, Spier SJ, Aldridge BM, Watnick M, Argenzio RA, Snyder JR.To determine the effects of two diets and water supplies on intestinal pH and mineral concentrations in the colon of horses, and to identify whether differences in these parameters exist in horses with and without enterolithiasis, surgical fistulation of the right dorsal colon was performed in six adult horses, three with and three without enterolithiasis. Each horse underwent four feeding trials: grass hay and untreated water, alfalfa hay and untreated water, grass hay with filtered/softened water, and alfalfa hay with filtered/softened water. Samples of colonic contents were analyzed for pH,...
Vervuert I, Bothe C, Coenen M.This study was conducted to evaluate the effects of different barley processing techniques on the glycaemic and insulinaemic responses in horses. It was hypothesized that the changes in pre-caecal starch digestibility caused by barley processing would affect metabolic responses. Six horses were fed in random order: whole (WB), finely ground (FGB), steamed (SB), steam-flaked (SFB) and popped barley (PB). The total barley intake was adjusted to 630 g starch/horse/day (1.2-1.5 g starch/kg BW/day). During a 10-day stabilization period, the horses also received 6 kg grass hay/horse/day. On the bloo...
Halpin MY, Drouillard JS, Fehlberg LK, Douthit TL, Lattimer JM.To assess the impact of protein on fermentation by equine cecal microorganisms, cecal fluid from 4 cecally cannulated horses was used to inoculate fermentation bottles containing buffer, forage, and supplemental protein. In experiment 1, sodium caseinate (SC) provided 0, 0.5%, 1%, 2%, or 4% additional crude protein (CP) to bottles containing alfalfa or native warm-season prairie grass hay. Bottles were equipped with continuous gas pressure monitors and placed into a shaking incubator for 48 hours at 39°C. Cultures with alfalfa had greater (P < .0001) in vitro dry matter disappearance (IVDMD...
Bertone AL, Ralston SL, Stashak TS.Each of 3 digestion trials (3 forage diets) was performed on 2 groups of horses 6 to 12 months after sham operation (group 1; n = 3) or large-colon resection (group 2; n = 5). Diets were alfalfa pellets, alfalfa hay, and grass hay. Feed and fecal analyses were performed to determine apparent digestion of dry matter, organic matter, and crude protein and true digestion of dry matter, organic matter, crude protein, total plant cell wall, hemicellulose, cellulose, and lignin. Additional fecal and metabolic variables determined were percentage of fecal water, total fecal water, metabolic organic m...
Ralston SL, Sullins KE, Stashak TS.The effect of 60% resection of the large colon vs ischemic insult without resection on the ability of horses to digest grass hay was investigated. Digestion trials were performed on 9 horses before surgery (base line) and 3 weeks, 6 weeks, and 6 months after surgery. The percentage of apparent digestion of crude protein, crude fiber, nitrogen-free extract, calcium, phosphorus, magnesium, manganese, copper, and zinc was calculated. Horses that had resection (n = 5) had decreased apparent digestion of crude protein, crude fiber, and phosphorus 3 weeks after surgery, compared with those in horses...
Ralston SL.Horses suffering from trauma, sepsis, and severe burns need 12% to 16% of protein (dry matter basis) in their diet. Since reduced appetite may be a problem, relatively energy dense (greater than 2 Mcal DE/kg) feeds should be offered. In hepatic failure, maintenance protein requirements (8% on a dry matter basis for adult horses) should be met with feeds that are high in short branched-chain amino acids and arginine but low in aromatic amino acids and tryptophan (for example, milo, corn, soybean, or linseed meal) in addition to grass hay. Vitamins A, C, and E should also be supplemented. In cas...
Guerrero JLS, Brito PHS, Ferreira MA, Arantes JA, Rusch E, Oliveira BVDS, Velasco-Bolaños J, Carregaro AB, Dória RGS.The prevalence of gastric disorders in high-performance horses, especially gastric ulceration, ranges from 50 to 90%. These pathological conditions have negative impacts on athletic performance and health. This study was designed to evaluate changes in gastric pH during a 24 h period and to compare gastrin concentrations at different time points in horses undergoing general inhalation anesthesia and dorsal recumbency. Twenty-two mixed-breed mares weighing 400 ± 50 kg and aged 8 ± 2 years were used. Of these, eight were fasted for 8 h and submitted to 90 min of general inhalation anesthesia i...
