Tryptophan (Trp) is an essential amino acid in swine nutrition that can affect growth, protein synthesis, immunity, intestinal barrier function and serotonin /melatonin production. Tryptophan is known to play a role in the regulation of aggressive behavior during stressful situations. Increased serotonin expression in the hypothalamus of the brain can lower cortisol levels (stress hormone), highlighting its importance in managing stress responses. Additionally, serotonin stimulates the expression of ghrelin, a hormone that enhances appetite, thereby promoting increased food intake and feed consumption. These South Korean researchers wanted to evaluate the effects of different levels of tryptophan supplementation in the feed of weaning pigs and lactating sows. In experiment 1, a total of 144 weaning pigs (Landrace × Yorkshire × Duroc) with initial mean body weight of 6.63 ± 0.21 kg were allotted to three treatment groups with six replicates per group of eight pigs per replicate in a completely randomized design. The treatments included a CW (basal diet only), TW6 (0.06% tryptophan + basal diet), and TW12 (0.12% tryptophan + basal diet). In experiment 2, a total of 40 lactating sows (Landrace × Yorkshire) were allotted to four treatment groups with ten replicates per group of one pig per replicate in a completely randomized design. The treatments included a CL group (basal diet only), TL3 (0.03% tryptophan + basal diet), TL6 (0.06% tryptophan + basal diet), and TL9 (0.09% tryptophan + basal diet).
The researchers found the following:
- Experiment 1
- TW12 group had significantly higher (p < 0.05) average daily gain and feed efficiency than the CW group.
- TW12 group had significantly reduced ear-biting behavior (p < 0.05) compared to the CW group
- Experiment 2
- TL3 and TL6 groups showed significantly reduced (p < 0.05) backfat loss compared to CL group.
- Average daily feed intake improved with tryptophan, with TL6 significantly higher (p < 0.05) than CL. Additionally, lying behavior increased and stereotypic behavior decreased (p < 0.05) significantly.
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