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Effect of diet on plasma tryptophan and serotonin in trained mares and geldings
  1. D. Alberghina, DVM, PhD1,
  2. C. Giannetto, DVM, PhD1,
  3. E. K. Visser, BSc, MSc, PhD2 and
  4. A. D. Ellis, BSc, PhD3
  1. 1Department of Experimental Sciences and Applied Biotechnology, Faculty of Veterinary Medicine, University of Messina, 98168 Messina, Italy
  2. 2Animal Sciences Group, Wageningen University and Research Centre, PO Box 65, 8200 AB Lelystad, The Netherlands
  3. 3School of Animal, Rural and Environmental Sciences, Nottingham Trent University, Southwell, Nottinghamshire NG25 0QF
  1. E-mail for correspondence: dalberghina{at}


Concentrations of tryptophan (TRP) and serotonin (5-HT) in plasma were measured in 36 moderately trained Dutch warmblood horses after eight weeks on a high fibre (n=18) or high starch (n=18) diet. Samples were taken three hours after feeding, when the horse was at rest, either at 11.00 or 14.00 hours. Plasma 5-HT and pH were significantly higher in horses fed a high fibre diet than those fed a high starch diet (P<0.05 and P<0.01, respectively), and significantly higher levels of TRP were found in mares than geldings (P<0.05). Plasma 5-HT may therefore be a good marker of serotonergic activity.

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