Protein Level and Infantile Diarrhea in a Postweaning Piglet Model

Abstract

Infantile diarrhea is a serious public health problem around worldwide and results in millions of deaths each year. The levels and sources of dietary protein are potential sources of diarrhea, but the relationship between the pathogenesis causes of infantile diarrhea and protein intake remains poorly understood. Many studies have indicated that the key to understanding the relationship between the protein in the diet and the postweaning diarrhea of piglets is to explore the influences of protein sources and levels on the mammalian digestion system. The current study was designed to control diarrhea control by choosing different protein levels in the diet and aimed at providing efficient regulatory measures for infantile diarrhea by controlling the protein levels in diets using a postweaning piglets model. To avoid influences from other protein sources, casein was used as the only protein source in this study. Fourteen piglets (7.98±0.14 kg, weaned at 28 d) were randomly allotted to two dietary treatments: a control group (Cont, containing 17% casein) and a high protein group (HP, containing 30% casein). The experiment lasted for two weeks and all animals were free to eat and drink water ad libitum. The diarrhea score (1=normal; 3=watery diarrhea) and growth performance were recorded daily. The results showed that the piglets in HP group had persistent diarrhea during the whole study, while no diarrhea was noticed in the control groups. Also, the feed intake and body weights were reduced in the HP groups compared with the other group (P<0.05). The diarrhea-related mRNA abundances were analyzed by real-time PCR; the results showed that HP treatment markedly decreased the expression of aquaporin (AQP, P<0.05) and the tight junction protein (P<0.05), but increased inflammatory cytokines (P<0.01) than those in control group. In addition, the Adenosine 5′-monophosphate (AMP)-activated protein kinase (AMPK) signaling pathway (P<0.01) was inhibited in the HP group. Intestinal microbiota was tested by 16S sequencing, and we found that the HP group had a low diversity compared the other group. In conclusion, despite being highly digestible, a high casein diet induced postweaning diarrhea and reduced the growth performance of the postweaning piglets. Meanwhile, AQP, tight junction protein, and intestinal immune were compromised. Thus, the mechanism of how a highly digestible protein diet induces diarrhea might be associated with the AMPK signaling pathway and intestinal microbiome.

Dietary high protein-induced diarrhea and intestinal inflammation by activation of NF-κB signaling in piglets

“…Our study showed that VH, VW, VH:CD ratio, and the villous surface area of the ileum narrowed under treatment with HP, which is in accordance with piglets’ intestinal mucosa being more easily damaged when fed a high CP ( van Beers-Schreurs et al., 1998 ; Wu et al., 2017 ), thus resulting in poor growth performance. A previous study demonstrated that CD was increased when pigs were fed with higher protein levels ( Gao et al., 2020 ), conflicting with our finding that dietary HP decreased colonic CD, which could be because that research focused more on the ileum, while the change appeared in the colon in our study. Crypt depth may be dependent on the proliferation and shedding rate of epithelial cells ( Hampson, 1986 ; Williams et al., 2013 ); however, more experiments are needed to further elucidate this notion.…”

Effects of Dietary Protein Level on the Microbial Composition and Metabolomic Profile in Postweaning Piglets

“…The diets we mixed in this experiment were described in our previous study [ 11 ]. The diets were free of antibiotics and growth enhancers, and they met or surpassed NRC standards for all essential amino acids.…”

Effects of dietary protein level on small intestinal morphology, occludin protein, and bacterial diversity in weaned piglets

“…Protein is an indispensable nutrient for the growth of piglets, but piglets are very sensitive to crude protein (CP) levels. Lower CP levels reduce villus height and crypt depth in the small intestine, affect the balance of microbiota, decrease the digestion and utilization of proteins in the intestine, and decrease the growth performance of piglets (Luo et al, 2015;Peng et al, 2016Peng et al, , 2017, whereas excessive CP levels result in a large amount of undigested and utilized proteins entering the intestine and fermenting spoilage and increase the pH in the stomach and small intestine, thereby providing suitable conditions for colonization of the intestine by pathogens and disrupting the balance of intestinal bacteria, leading to diarrhea (Gao et al, 2020;Zhang et al, 2020).…”

“…At present, diarrheal disease has been the cause of high mortality in children (Liu et al., 2019; Taborda et al., 2018). How to control infant diarrhea by regulating the level of protein has been a focus of recent research (Gao et al., 2020). The piglet model has become the best model for human nutrition.…”