title: Dietary L-tryptophan supplementation with reduced large neutral amino acids enhances feed efficiency and decreases stress hormone secretion in nursery pigs under social-mixing stress.
abstract: Tryptophan (Trp), the rate-limiting substrate of serotonin [5-hydroxytryptoamine (5-HT)] synthesis in the brain, competes with large neutral amino acids (LNAA) to cross the blood-brain barrier. This study was designed to evaluate the effect of L-Trp supplementation on nursery pigs experiencing social-mixing stress and fed diets varying in LNAA concentrations. Forty-eight individually housed barrows at 6 wk of age were randomly allotted to 4 dietary treatments based on a 2 × 2 factorial arrangement, with L-Trp supplementation (0 or 0.6%) and LNAA concentrations (4.5 or 3.8%) as the 2 main factors. Pigs were fed the diets for 7 d. On d 4, pigs within a treatment were paired in a new pen to create social-mixing stress and behavior was recorded for 24 h. Body weight was measured on d 0, 4, 5, and 7. Saliva and blood were collected on d 4 and 7. On d 7, pigs were killed to obtain hypothalami. During the entire period excluding the mixing day (d 5), L-Trp supplementation improved (P < 0.01) feed efficiency of pigs and lowering the LNAA further enhanced (P < 0.05) the effects of L-Trp. Supplementation of 0.6% L-Trp increased (P < 0.001) hypothalamic 5-HT and 5-hydroxyindoleacetic acid. The salivary cortisol concentration was reduced (P < 0.05) by lowering the LNAA. Collectively, lowering the LNAA further enhanced the improvement of feed efficiency by L-Trp supplementation of nursery pigs under social-mixing stress in association with reduced stress hormones, indicating that reducing LNAA in the diet can facilitate the effect of L-Trp on the stress response of pigs.
authors: Department of Animal Science, North Carolina State University, Raleigh, NC, USA.
authors: Yan Bin
authors: YB
authors: Shen
authors: Gwendoline
authors: G
authors: Voilqué
authors: Jack
authors: J
authors: Odle
authors: Sung Woo
authors: SW
authors: Kim
mesh_terms: D000222:Adaptation, Physiological; D000374:Aggression; D000596:Amino Acids / Q000008:administration & dosage / Q000494:pharmacology*; D000821:Animal Feed / Q000032:analysis; D000818:Animals; D004032:Diet / Q000662:veterinary; D019587:Dietary Supplements; D004734:Energy Metabolism / Q000187:drug effects*; D006854:Hydrocortisone / Q000737:chemistry / Q000378:metabolism; D007031:Hypothalamus / Q000737:chemistry / Q000378:metabolism; D008297:Male; D008315:Malondialdehyde / Q000378:metabolism; D009043:Motor Activity; D012463:Saliva / Q000737:chemistry; D012919:Social Behavior; D013312:Stress, Physiological / Q000502:physiology*; D013552:Swine / Q000502:physiology*; D014364:Tryptophan / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000596:Amino Acids; D008315:Malondialdehyde; D014364:Tryptophan; D006854:Hydrocortisone