Extraction and identification of the chyme proteins in the digestive tract of growing pigs

This study aimed to explore the rule of degradation of dietary proteins by identifying chyme proteins in different segments of the digestive tract of growing pigs, using proteomics techniques. Six growing pigs were fed a corn-soybean meal-based diet for 7 days. The feedstuff and chyme proteins were separately extracted and separated with SDS-PAGE. 2D LCMS/MS combined with protein database searching identified 1,513 proteins in different segments of the gastrointestinal tract, the number of identified exogenous proteins gradually decline from the stomach to colon, with large amounts in the duodenum to the large intestine. More corn proteins than soybean proteins were identified both in the feedstuff and chyme, and these were significantly decreased after digestion in the stomach. More membrane proteins than non-membrane proteins were identified in whole digestive tract. These results regarding the profiles of chyme proteins in different segments of the gastrointestinal tract would provide useful information for optimizing feed formula in pigs.

Increases in circulating amino acids with in-feed antibiotics correlated with gene expression of intestinal amino acid transporters in piglets

In-feed antibiotics have been commonly used to promote the growth performance of piglets. The antibiotics can increase protein utilization, but the underlying mechanism is largely unknown. The present study investigated the effects of in-feed antibiotics on intestinal AA transporters and receptors to test the hypothesis that the alteration of circulating AA profiles may be concomitant with the change of intestinal AA transporters and receptors. Sixteen litters of piglets at day 7 started to receive creep feed with (Antibiotic) or without (Control) antibiotic. Piglets were weaned at day 23 after birth, and fed the same diets until day 42. In-feed antibiotics did not affect the BW of 23-day-old (P = 0.248), or 42-day-old piglets (P = 0.089), but increased the weight gain to feed ratio from day 23 to 42 (P = 0.020). At day 42 after birth, antibiotic treatment increased the concentrations of most AAs in serum (P < 0.05), and decreased the concentrations of most AAs in jejunal and ileal digesta. Antibiotics upregulated (P < 0.05) the mRNA expression levels for jejunal AAs transporters (CAT1, EAAC1, ASCT2, y⁺LAT1), peptide transporters (PepT1), and Na⁺-K⁺-ATPase (ATP1A1), and ileal AA transporters (ASCT2, y⁺LAT1, b^0,+AT, and B⁰AT1), and ATP1A1. The antibiotics also upregulated the mRNA expression of jejunal AAs receptors T1R3 and CaSR, and ileal T1R3. Protein expression levels for jejunal AA transporters (EAAC1, b^0,+AT, and ASCT2) and PepT1 were also upregulated. Correlation analysis revealed that the alterations of AA profiles in serum after the in-feed antibiotics were correlated with the upregulations of mRNA expression levels for key AA transporters and receptors in the small intestine. In conclusion, the in-feed antibiotics increased serum level of most AAs and decreased most AAs in the small intestine. These changes correlated with the upregulations of mRNA expression levels for key AA transporters and receptors in the small intestine. The findings provide further insights into the mechanism of in-feed antibiotics, which may provide new framework for designing alternatives to antibiotics in animal feed in the future.