During pregnancy, tryptophan (Trp) is required for several purposes, and Trp metabolism varies over time in the mother and fetus. Increased oxidative stress (OS) with high metabolic, energy and oxygen demands during normal pregnancy or in pregnancy-associated disorders has been reported. Taking the antioxidant properties of Trp and its metabolites into consideration, we made four hypotheses. First, the use of Trp and its metabolites is optional based on their antioxidant properties during pregnancy. Second, dynamic Trp metabolism is an accommodation mechanism in response to OS. Third, regulation of Trp metabolism could be used to control/attenuate OS according to variations in Trp metabolism during pregnancy. Fourth, OS-mediated injury could be alleviated by regulation of Trp metabolism in pregnancy-associated disorders. Future studies in normal/abnormal pregnancies and in associated disorders should include measurements of free Trp, total Trp, Trp metabolites, and activities of Trp-degrading enzymes in plasma. Abnormal pregnancies and some associated disorders may be associated with disordered Trp metabolism related to OS. Mounting evidence suggests that the investigation of the use of Trp and its metabolites in pregnancy will be meanful.

Two experiments were designed to explore the effects of coated zinc (Zn) oxide nanoparticles (NZO) on the diarrhea ratio, antioxidant capacity, intestinal morphology, and zinc excretion in growing pigs. In Exp.1, 270 growing pigs (21.88 ± 0.8 kg initial BW) were allocated to three treatments, each for 30 d: (i) control group (CG), basal diet containing Zn-free premix + 100 mg Zn/kg from ZnSO₄; (ii) high Zn (HZN), basal diet containing Zn-free premix + 2,250 mg Zn/kg from ZnO; (iii) coated nano ZnO (CNZO), basal diet containing Zn-free premix + 100 mg Zn/kg from coated NZO. In Exp.2, 21 crossbred growing pigs (17.04 ± 0.01 kg initial BW) were allocated to three treatments, each for 28 d: (i) HZN, basal diet containing Zn-free premix + 2,250 mg Zn/kg from ZnO; (ii) low concentration of nano ZnO (LNZO), basal diet containing Zn-free premix + 100 mg Zn/kg from 5% coated NZO material; (iii) high concentration of nano ZnO (HNZO), basal diet containing Zn-free premix + 100 mg Zn/kg from 10% coated NZO material. In Exp. 1, compared with the CG diet, CNZO significantly reduced the diarrhea rate (P < 0.05) and increased the activities of glutathione peroxidase and superoxide dismutase (P < 0.05). Compared with HZN, CNZO decreased the activities of serum alanine aminotransferase, and alkaline phosphatase, as well as the fecal zinc concentration (P < 0.05). In Exp. 2, pigs fed LNZO or HNZO had an increased final BW, average daily weigh and diarrhea rate, and a decreased level of Zn in the plasma, liver, and feces on day 14 compared with the HZN group (P < 0.05). The villous height and villous height/crypt depth ratio of duodenum were higher (P < 0.05) in the HZN group than the HNZO group, whereas the higher villous height of jejunum was observed in the LNZO group compared with that in the HNZO group (P < 0.05). We found that CNZO (100 mg/kg Zn) could improve the antioxidant capacity and reduce fecal Zn emission. However, the diarrhea rate was not effectively suppressed when compared with the HNZO supplementation. Furthermore, coated NZO material of 5% concentration is more effective in improving the morphology of intestinal villus.

Animal protein sources such as fishmeal and plasma powder are excellent and indispensable sources of energy, amino acids, and minerals in animal production. Amino acid imbalance, especially methionine-to-sulfur amino acid (Met:SAA) ratio, caused by an imbalance of animal protein meal leads to growth restriction. This study was conducted to evaluate the effects of imbalanced Met:SAA ratio supplementation of different animal protein source diets on growth performance, plasma amino acid profiles, antioxidant capacity and intestinal morphology in a piglet model. Twenty-four weaned piglets (castrated males; BW = 10.46 ± 0.34 kg), assigned randomly into 3 groups (8 piglets/group), were fed for 28 d. Three experimental diets of equal energy and crude protein levels were as follows: 1) a corn-soybean basal diet with a Met:SAA ratio at 0.51 (BD); 2) a plasma powder diet with a low Met:SAA ratio at 0.41 (L-MR); 3) a fishmeal diet with a high Met:SAA ratio at 0.61 (H-MR). Results revealed that compared to BD, L-MR significantly decreased (P < 0.05) the activities of plasma total antioxidant capacity and glutathione peroxidase, plasma amino acid profiles, and significantly reduced (P < 0.05) villus height and crypt depth in the duodenum and jejunum. Additionally, L-MR significantly reduced (P < 0.05) the mRNA expression level of solute carrier family 7 member 9 (SlC7A9) in the ileum, and significantly increased (P < 0.05) mRNA expression levels of zonula occludens-1 (ZO-1) in the duodenum, and Claudin-1, ZO-1, sodium-coupled neutral amino acid transporters 2 (SNAT2) and SlC7A7 in the jejunum. H-MR significantly increased (P < 0.05) plasma SAA levels, and significantly reduced (P < 0.05) average daily feed intake, villus height, and villus height-to-crypt depth (VH:CD) ratio in the ileum compared to BD. In conclusion, L-MR may result in oxidative stress and villous atrophy but proves beneficial in improving intestinal barrier function and the activity of amino acid transporters for compensatory growth. H-MR may impair intestinal growth and development for weaned piglets. The research provides a guidance on the adequate Met:SAA ratio (0.51) supplementation in diet structure for weaned piglets.

This study was conducted to evaluate the effects of dietary insect powder supplementation as a protein source on plasma amino acid profiles, intestinal amino acid transport and sensing in a piglet model. A total of 144 weanling piglets were randomly assigned to four experimental diets for two phases (Days 1–28 and Days 29–56), to assess the effects on amino acid profiles and transportation in the segments of the intestine. The groups were basal diet (control), control diet plus Tenebrio molitor (TM), control diet plus Musca domestica larvae (MDL) and control diet plus Zophobas morio (ZM). The plasma free amino acid levels were stable comparable among treatments, except that the lysine level was significantly reduced by dietary MDL and ZM supplementation in the first phase (p < 0.05). In the 1st phase, the sensitivity of intestinal segments to the regulation of the amino acid level by insect powder supplementation follows sequence: colon > ileum > jejunum, while the order switched to jejunum > colon > ileum in the 2nd phase. The relative RNA expressions of mitogen-activated protein 4 kinase 3 (MAP4K3), sodium dependent neutral amino acid transporter2 (SNAT2), the transient receptor potential cation channel subfamily V member 1 (TRPV1) and taste 1 receptor member 1/3 (T1R3) in the segments of the intestine were affected by different dietary insect powder supplementation. G protein-coupled receptor family C group 6 member A (GPRC6A) level in the jejunal and colonic mucosa was upregulated by MDL supplementation (p < 0.05). These results indicated that dietary insects improved the metabolism of the amino acid in the prophase (the 1st phase) through regulating the sensing gene and mTOR signal pathway in intestinal mucosa by targeting different receptors. The finding demonstrates that the insect powder is a potentially promising source for protein deposition.