TITLE:
Alternative Protein Sources for Mitigating Post-Weaning Diarrhea in Piglets: Mechanistic Links among Protein Digestibility, Gut Microbiota, and Intestinal Barrier Function and Immune Regulation
AUTHORS:
M. Chantal Nzeyimana, Dieudonné Nsengiyumva, Constantin Nimbona, Napoleon Munyaneza, Yi Bao, Ruqing Zhong, Chen Liang, Hongfu Zhang
KEYWORDS:
Post-Weaning Diarrhea, Alternative Protein Sources, Protein Digestibility, Proteolytic Fermentation, Gut Microbiota, Intestinal Barrier
JOURNAL NAME:
Open Journal of Animal Sciences,
Vol.16 No.4,
October
28,
2026
ABSTRACT: Enterotoxigenic Escherichia coli (ETEC) is an important infectious cause of post-weaning diarrhea (PWD) and abrupt feed changes, low feed intake, immature digestive system, microbial dysbiosis, epithelial barrier function and mucosal inflammation have been identified as predisposing factors to and severity of PWD. Dietary protein may play a major role in this, with indigestible protein entering the hindgut potentially stimulating the production of protease fermentation, ammonia, biogenic amines, indoles, phenols and branched chain fatty acids, and antigenic and bioactive protein with effects on the epithelial and immune responses. This review presents a mechanism-based evaluation of the effects of various protein sources on 5 interrelated domains: small intestinal protein digestibility, hindgut fermentation, microbiota composition and metabolic activity, epithelial barrier integrity and immune-inflammatory regulation. Spray-dried plasma is one of the few ingredients reviewed that has relatively widespread evidence of enhancing early post-weaning feed intake and growth performance, with selected controlled studies demonstrating benefits for barrier function, immunity, and diarrhea; however, there are drawbacks with cost and supply, and a biosafety requirement. The effects produced by products of yeast origin are directed towards microbiota and immunity and vary depending on the type of product used (whole yeast, hydrolysates, cell wall fractions, beta-glucans, mannans or live cultures). There is still limited direct evidence for the protein source of consistent PWD mitigation that is species, processing and inclusion level dependent, though other protein sources such as insect meals, microalgae and novel legumes have potential to diversify protein sources and promote sustainability. No one protein source is optimal to regulate all the pathways that affect PWD. So, in each phase, an appropriate mixture of highly digestible proteins and complementary functional ingredients provides a more biologically sound approach than using only one of the alternative protein sources. Overall, alternative protein sources can help mitigate post weaning diarrhea (PWD) through improvement of protein digestibility, modulation of hindgut fermentation and gut microbiota, support the integrity of the intestinal barrier and help to regulate excessive inflammatory responses; however, the effectiveness is dependent on the protein source, processing conditions, level of inclusion and the physiological and disease state of the piglet.