No abstract

EVALUATING THE EFFECTIVENESS OF VARYING DOSES OF SUPPLEMENTAL TRYPTOPHAN AS A CALMATIVE IN HORSESTryptophan (Trp), the amino acid precursor to serotonin, is a common ingredient in many commercial equine calming supplements. However, there is little scientific research to support the efficacy of tryptophan at modifying horse behavior. The objective of this study was to examine how various doses of tryptophan supplementation impacted reactive behavior and physiological stress measurements in the horse. Eleven horses (9 geldings, 2 mares) were given four treatments-0 mg Trp/kg bodyweight (CON), 20 mg Trp/kg bodyweight (LOW), 40 mg Trp/kg bodyweight (MED), and 60 mg Trp/kg bodyweight (HIGH)-in a randomized crossover design.Each treatment lasted three days. On Days 1 and 3 of each treatment, horses underwent a behavior test to measure startle response. Heart rate measurements and the speed at which the horses fled from startling stimuli were recorded. In addition, serum glucose, lactate, and cortisol levels were analyzed both immediately before the startle test and again 15 minutes after the test. Significant sedative effects were seen at LOW Day 1 on heart rate increase during the startle test (P = 0.05) and on change in serum lactate levels (P = 0.03). At MED Day 1, sedative effects were seen on change in serum cortisol levels (P = 0.01). Some excitatory effects were seen at MED Day 3 on the time for heart rate to return to baseline after the startle test (P = 0.03). No significant effects were seen at HIGH Day 1 or Day 3. A subset of blood samples was analyzed for serum free Trp and the ratio of Trp to other large neutral amino acids, which verified treatment effect. !iii ACKNOWLEDGEMENTS There are so many people I would like to thank for their help and guidance in completing this project. I learned so much from my advisor, Dr. Temple Grandin. Working with her has been the opportunity of a lifetime. I am so grateful for the help and support of my committee members as well. Dr. Terry Engle, for advising me when I didn't know what to do, for always being willing to meet with me to answer my never-ending stream of questions, and for reassuring me that everything was going ok. Dr. Jason Ransom, for his insights, suggestions, and guidance; his commitment and willingness to help didn't waiver, even when he relocated to Washington. Dr. Don Rojas, for providing new insight on the project. I appreciate Dr. Tanja Hess' advice and assistance with balancing the horses' diets. I would also like to thank Dr. Karen Sellins for her patience and help with ordering supplies for the project, finding volunteers, and in teaching me the laboratory procedures necessary to analyze the blood samples. I am sincerely grateful to Dr. Ann Hess, who took the time to meet with me on several occasions, and who patiently helped me work through the statistical analysis. I also appreciate Dr. Jerry Black's assistance in finding horses for me to use for the project and Wayne Miller's help with setting everything up at the Equine Teaching and Research...