Effects of feeding large amounts of grain on colonic contents and feces in horses.
OBJECTIVE
To assess changes in systemic hydration, concentrations of plasma electrolytes, hydration and physical properties of colonic contents and feces, and gastrointestinal transit in horses with access to large amounts of grain.


METHODS
6 horses with right dorsal colon (RDC) fistulas.


METHODS
In a crossover design, horses were alternately fed 1 of 3 diets: orchard grass hay ad libitum after being adapted to this diet for at least 5 days, orchard grass hay ad libitum and 4.55 kg of grain offered every 12 hours after being adapted to orchard grass hay ad libitum for at least 5 days, or orchard grass hay ad libitum and 4.55 kg of grain offered every 12 hours after being adapted to this diet for at least 5 days. Physical examinations were performed and samples of blood, colonic contents, and feces were collected every 6 hours during a 48-hour observation period.


RESULTS
Grain ingestion had several effects, including changes in the concentrations of electrolytes in plasma; RDC contents became more homogenous, dehydrated, foamy, and less dense; RDC contents flowed spontaneously when the cannula was opened; RDC contents expanded when heated in an oven; and feces became fetid and less formed. Horses did not have any clinical signs of colic, endotoxemia, or laminitis.


CONCLUSIONS
Changes observed in the colonic contents and feces may be explained by the large amounts of hydrolyzable carbohydrates provided by grain. Access to large amounts of grain may increase the risk of tympany and displacement of the large intestine.
Lopes
Marco A F
MA
Marion duPont Scott Equine Medical Center, Virginia-Maryland Regional College of Veterinary Medicine, Leesburg, VA 20176, USA.
White
Nathaniel A
NA
Crisman
Mark V
MV
Ward
Daniel L
DL
D000704:Analysis of Variance; D000821:Animal Feed; D000818:Animals; D003106:Colon / Q000737:chemistry*; D018592:Cross-Over Studies; D004492:Edetic Acid; D002523:Edible Grain; D004573:Electrolytes / Q000097:blood; D005243:Feces / Q000737:chemistry*; D005766:Gastrointestinal Contents / Q000737:chemistry*; D006736:Horses / Q000502:physiology*; D013997:Time Factors; D014867:Water / Q000032:analysis
D004573:Electrolytes; D014867:Water; C028222:cobalt-ethylenediamine tetraacetic acid chelate; D004492:Edetic Acid