Surplus dietary tryptophan reduces plasma cortisol and noradrenaline concentrations and enhances recovery after social stress in pigs.
Social stress occurs in intensive pig farming due to aggressive behavior. This stress may be reduced at elevated dietary levels of tryptophan (TRP). In this study, we compared the effects of high (13.2%) vs. normal (3.4%) dietary TRP to large neutral amino acid (LNAA) ratios on behavior and stress hormones in catheterized pigs ( approximately 50 kg BW), which were exposed to social stress by placing them twice into the territory of a dominant pig ( approximately 60 kg) for 15 min. Pre-stress plasma TRP concentrations were 156+/-15 vs. 53+/-6 micromol/l (p<0.01) in pigs on the high vs. normal TRP diets, respectively. Pre-stress plasma cortisol and noradrenaline concentrations were twofold (p<0.01) and 1.4-fold (p<0.05) lower but plasma adrenaline concentration was similar in pigs on the high vs. normal TRP diets, respectively. During the social confrontations, pigs on the high vs. normal TRP diets show a tendency towards reduced active avoidance behavior (3.2+/-1.1 vs. 6.7+/-1.2 min, p<0.1) but their physical activity (8.5+/-0.6 vs. 10.2+/-0.8 min) and aggressive attitude towards the dominant pig (11+/-3 vs. 7+/-2 times biting) were similar. Immediate (+5 min) post-stress plasma cortisol, noradrenaline and adrenaline responses were similar among dietary groups. After the social confrontations, the post-stress plasma cortisol, noradrenaline and adrenaline concentrations and/or curves (from +5 min to 2 h) were lower/steeper (p<0.05) in pigs on the high vs. normal TRP diets. In summary, surplus TRP in diets for pigs (1) does not significantly affect behavior when exposed to social stress, (2) reduces basal plasma cortisol and noradrenaline concentrations, (3) does not affect the immediate hormonal response to stress, and (4) reduces the long-term hormonal response to stress. In general, pigs receiving high dietary TRP were found to be less affected by stress.
Animal Sciences Group, Wageningen UR, Division of Nutrition and Food, Edelhertweg 15, P.O. Box 65, 8200 AB Lelystad, The Netherlands. sietse-jan.koopmans@wur.nl
Sietse Jan
SJ
Koopmans
Marko
M
Ruis
Ruud
R
Dekker
Hans
H
van Diepen
Mechiel
M
Korte
Zdzislaw
Z
Mroz
D027062:Amino Acid Transport System L / Q000097:blood; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D001923:Brain Chemistry / Q000187:drug effects; D002255:Carbonic Acid / Q000097:blood; D004032:Diet; D006854:Hydrocortisone / Q000097:blood*; D019344:Lactic Acid / Q000097:blood; D009638:Norepinephrine / Q000097:blood*; D020127:Recovery of Function / Q000187:drug effects / Q000502:physiology*; D012463:Saliva / Q000187:drug effects; D012919:Social Behavior; D013315:Stress, Psychological / Q000097:blood* / Q000503:physiopathology*; D013552:Swine; D013997:Time Factors; D014364:Tryptophan / Q000008:administration & dosage* / Q000097:blood / Q000172:deficiency
D027062:Amino Acid Transport System L; D019344:Lactic Acid; D002255:Carbonic Acid; D014364:Tryptophan; D006854:Hydrocortisone; D009638:Norepinephrine