Changes

*Nonracing performance horses (17% pre-competition, 56% post-competition)<ref>Hartmann, A.M, Frankeny, R.L (2003) A preliminary investigation into the association between competition and gastric ulcer formation in non-racing performance horses.  ''J Equine Vet Sci'', 23:560-561.  In:Sanchez, L.C (2010) 'Diseases Of The Stomach' in  Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), Saunders, Chapter 15.</ref>

*Nonracing performance horses (17% pre-competition, 56% post-competition)<ref>Hartmann, A.M, Frankeny, R.L (2003) A preliminary investigation into the association between competition and gastric ulcer formation in non-racing performance horses.  ''J Equine Vet Sci'', 23:560-561.  In:Sanchez, L.C (2010) 'Diseases Of The Stomach' in  Reed, S.M, Bayly, W.M. and Sellon, D.C (2010) '''Equine Internal Medicine''' (Third Edition), Saunders, Chapter 15.</ref>

*Pleasure horses in full work ~ 60%<ref name="Bell">Bell, R.J, Mogg, T, Kingston, J.K (2007) Equine gastric ulcer syndrome in adult horses: a review.  ''N Z Vet J'', 55(1):1-12).</ref>   

*Pleasure horses in full work ~ 60%<ref name="Bell">Bell, R.J, Mogg, T, Kingston, J.K (2007) Equine gastric ulcer syndrome in adult horses: a review.  ''N Z Vet J'', 55(1):1-12).</ref>   

*Foals ~25-57%<ref>Wilson, J.H (1986) Gastric and duodenal ulcers in foals: a retrospective study.  ''Proc Equine Colic Res Symp 2nd:126-128.</ref><ref>Murray, M.J, Grodinsky, C, Cowles, R.R, ''et al.''(1990) Endoscopic evaluation of changes in gastric lesions of Thoroughbred foals.  ''J Am Vet Med Assoc'', 196:1623-1627.</ref><ref>Murray, M.J (1989) Endoscopic appearance of gastric lesions in foals: 94 cases (1987-1988).  ''J Am Vet Med Assoc'', 195:1135-1141.</ref>, the incidence increases dramatically in foals with clinical signs, especially gastrointestinal signs.<ref name="EGUC">The Equine Gastric Ulcer Council (1999) Tutorial Article: Recommendations for the diagnosis and treatment of equine gastric ulcer syndrome (EGUS).  ''Equine Vet Educ'', 11(5):262-272.</ref>

*Foals ~25-57%<ref>Wilson, J.H (1986) Gastric and duodenal ulcers in foals: a retrospective study.  ''Proc Equine Colic Res Symp 2nd:126-128.</ref><ref>Murray, M.J, Grodinsky, C, Cowles, R.R, ''et al.''(1990) Endoscopic evaluation of changes in gastric lesions of Thoroughbred foals.  ''J Am Vet Med Assoc'', 196:1623-1627.</ref><ref>Murray, M.J (1989) Endoscopic appearance of gastric lesions in foals: 94 cases (1987-1988).  ''J Am Vet Med Assoc'', 195:1135-1141.</ref> (the incidence increases dramatically in foals with clinical signs, especially gastrointestinal signs).<ref name="EGUC">The Equine Gastric Ulcer Council (1999) Tutorial Article: Recommendations for the diagnosis and treatment of equine gastric ulcer syndrome (EGUS).  ''Equine Vet Educ'', 11(5):262-272.</ref>

The prevalence and severity of ulcers increases with work intensity<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref> and duration<ref>Orsini, J.A, Pipers, F.S (1997) Endoscopic evaluation of the relationship between training, racing, and gastric ulcers.  ''Vet Surg'', 26:424.  In: Orsini, J (2000) ''Tutorial Article'' Gastric ulceration in the mature horse: a review.  ''Equine Vet Educ'', 12(1):24-27.</ref><ref>Murray, M.J (1994) Gastric ulcers in adult horses.  ''Comp Cont Educ Pract Vet'', 16:792-794.  In:Orsini, J (2000) ''Tutorial Article'' Gastric ulceration in the mature horse: a review.  ''Equine Vet Educ'', 12(1):24-27.</ref>,  thus racehorses in active training are more often affected<ref name="Hammond">Hammond, C.J, Mason, D.K, Watkins, K.L (1986) Gastric ulceration in mature Thoroughbred horses.  ''Equine Vet J'', 18(4):284-287.</ref> and in half of these,  the lesions are moderate to severe.<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref>  In one study, all horses developed gastric ulcers within 2 weeks of entering simulated race training.<ref name="Vatistas 2">Vatistas, N.J, Sifferman, R.L, Holste, J, Cox, J.L, Pinalto, G, Schultz, K.T (1999) Induction and maintenance of gastric ulceration in horses in simulated race training.  ''Equine Vet J Suppl'', 29:40-44</ref>  Lesions are thought to be chronically progressive during race training, but to regress during retirement.<ref name="Hammond">Hammond, C.J, Mason, D.K, Watkins, K.L (1986) Gastric ulceration in mature Thoroughbred horses.  ''Equine Vet J'', 18(4):284-287.</ref>  Horses with signs of gastrointestinal distress also demonstrate an increased frequency and severity of ulcerative lesions.<ref name="EGUC">The Equine Gastric Ulcer Council (1999) Tutorial Article: Recommendations for the diagnosis and treatment of equine gastric ulcer syndrome (EGUS).  ''Equine Vet Educ'', 11(5):262-272.</ref>EGUS prevalence is high in horses with bowel, liver and oesophageal lesions.<ref name="Sandin">Sandin, A, Skidell, J, Haggstrom, J, Nilsson, G (2000) ''Postmortem'' findings of gastric ulcers in Swedish horses older than age one year: a retrospective study of 3715 horses (1924–1996).  ''Equine Vet J'', 32(1):36-42.</ref>  Among show horses, 82% of those with signs of abdominal discomfort had gastric ulcers<ref>Murray, M. (1992) Gastric ulceration in horses: 91 cases (1987-1990).  ''J Am Vet Med Assoc'', 201:117-120.  In: Martineau, H, Thompson, H, Taylor, D (2009) Pathology of gastritis and gastric ulceration in the horse.  Part 1: Range of lesions present in 21 mature individuals.  ''Equine Vet J'', 41(7):638-644.</ref>  Around 30% of adult horses and about 50% of foals have mild gastric erosions which heal without treatment or clinical signs.<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref>  In 201 clinically normal horses in Denmark, 53% had EGUS with severity score >2 and older horses were more likely to have lesions in both regions of the stomach<ref>Luthersson, N, Nielsen, K.H, Harris, P, Parkin, T.D (2009) The prevalence and anatomical distribution of equine gastric ulcer syndrome (EGUS) in 201 horses in Denmark.  ''Equine Vet J'', 41(7):619-24.</ref>

The prevalence and severity of ulcers increases with work intensity<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref> and duration<ref>Orsini, J.A, Pipers, F.S (1997) Endoscopic evaluation of the relationship between training, racing, and gastric ulcers.  ''Vet Surg'', 26:424.  In: Orsini, J (2000) ''Tutorial Article'' Gastric ulceration in the mature horse: a review.  ''Equine Vet Educ'', 12(1):24-27.</ref><ref>Murray, M.J (1994) Gastric ulcers in adult horses.  ''Comp Cont Educ Pract Vet'', 16:792-794.  In:Orsini, J (2000) ''Tutorial Article'' Gastric ulceration in the mature horse: a review.  ''Equine Vet Educ'', 12(1):24-27.</ref>,  thus racehorses in active training are more often affected<ref name="Hammond">Hammond, C.J, Mason, D.K, Watkins, K.L (1986) Gastric ulceration in mature Thoroughbred horses.  ''Equine Vet J'', 18(4):284-287.</ref> and in half of these,  the lesions are moderate to severe.<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref>  In one study, all horses developed gastric ulcers within 2 weeks of entering simulated race training.<ref name="Vatistas 2">Vatistas, N.J, Sifferman, R.L, Holste, J, Cox, J.L, Pinalto, G, Schultz, K.T (1999) Induction and maintenance of gastric ulceration in horses in simulated race training.  ''Equine Vet J Suppl'', 29:40-44</ref>  Lesions are thought to be chronically progressive during race training, but to regress during retirement.<ref name="Hammond">Hammond, C.J, Mason, D.K, Watkins, K.L (1986) Gastric ulceration in mature Thoroughbred horses.  ''Equine Vet J'', 18(4):284-287.</ref>  Horses with signs of gastrointestinal distress also demonstrate an increased frequency and severity of ulcerative lesions.<ref name="EGUC">The Equine Gastric Ulcer Council (1999) Tutorial Article: Recommendations for the diagnosis and treatment of equine gastric ulcer syndrome (EGUS).  ''Equine Vet Educ'', 11(5):262-272.</ref>EGUS prevalence is high in horses with bowel, liver and oesophageal lesions.<ref name="Sandin">Sandin, A, Skidell, J, Haggstrom, J, Nilsson, G (2000) ''Postmortem'' findings of gastric ulcers in Swedish horses older than age one year: a retrospective study of 3715 horses (1924–1996).  ''Equine Vet J'', 32(1):36-42.</ref>  Among show horses, 82% of those with signs of abdominal discomfort had gastric ulcers<ref>Murray, M. (1992) Gastric ulceration in horses: 91 cases (1987-1990).  ''J Am Vet Med Assoc'', 201:117-120.  In: Martineau, H, Thompson, H, Taylor, D (2009) Pathology of gastritis and gastric ulceration in the horse.  Part 1: Range of lesions present in 21 mature individuals.  ''Equine Vet J'', 41(7):638-644.</ref>  Around 30% of adult horses and about 50% of foals have mild gastric erosions which heal without treatment or clinical signs.<ref name="Merck">Merck & Co (2008) The Merck Veterinary Manual (Eighth Edition), Merial</ref>  In 201 clinically normal horses in Denmark, 53% had EGUS with severity score >2 and older horses were more likely to have lesions in both regions of the stomach<ref>Luthersson, N, Nielsen, K.H, Harris, P, Parkin, T.D (2009) The prevalence and anatomical distribution of equine gastric ulcer syndrome (EGUS) in 201 horses in Denmark.  ''Equine Vet J'', 41(7):619-24.</ref>