Abstract
Tryptophan (Trp) plays an essential role in pig behavior and growth performances. However, little is known about Trp's effects on tight junction barrier and intestinal health in weaned pigs. In the present study, twenty-four (24) weaned pigs were randomly assigned to one of the three treatments with 8 piglets/treatments. The piglets were fed different amounts of L-tryptophan (L-Trp) as follows: 0.0%, 0.15, and 0.75%, respectively, named zero Trp (ZTS), low Trp (LTS), and high Trp (HTS), respectively. No significant differences were observed in average daily gain (ADG), average daily feed intake (ADFI), and gain: feed (G/F) ratio between the groups. After 21 days of the feeding trial, results showed that dietary Trp significantly increased (P < 0.05) crypt depth and significantly decreased (P < 0.05) villus height to crypt depth ratio (VH/CD) in the jejunum of pig fed HTS. In addition, pig fed HTS had higher (P < 0.05) serum diamine oxidase (DAO) and D-lactate. Furthermore, pig fed HTS significantly decreased mRNA expression of tight junction proteins occludin and ZO-1 but not claudin-1 in the jejunum. The number of intraepithelial lymphocytes and goblet cells were not significantly different (P > 0.05) between the groups. Collectively, these data suggest that dietary Trp supplementation at a certain level (0.75%) may negatively affect the small intestinal structure in weaned pig.
Highlights
The postweaning period represents a delicate transitional phase in pig’s life
average daily gain (ADG) was numerically improved by 8% and 11% during d7–d14 and 16% and 36% during d14–d21, respectively, by low Trp supplementation (LTS) and high Trp supplementation Trp (HTS) compared to zero Trp supplementation (ZTS)
The results showed that pig fed HTS significantly increased (P < 0.05) CD and decreased villus height to crypt depth ratio (VH/CD) (P < 0.05) in the jejunum compared to ZTS and LTS
Summary
The postweaning period represents a delicate transitional phase in pig’s life. The numerous stresses to their endocrinology, metabolism, and physiology that piglets experience following weaning are reflected in homeostatic changes to their bodies. The gastrointestinal tract is responsive to stressors. Weaning is known to compromise the digestive, absorptive, and secretory capacity of the small intestine which can cause morphological and histological changes of the small intestine [1,2,3,4]. Weaning induces a deleterious effect on intestinal barrier function [5, 6]. Tryptophan has a potential role to facilitate stress adaptation of animals and human through increasing hypothalamic serotonin (5-hydroxytryptamine, 5-HT) level [7, 8]. Several studies have shown that dietary Trp may reduce
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