Effects Of Dietary Protein Sources And Protein Levels On Gut Health And Liver Metabolism In Weaned Piglets

In the pig industry,moderate protein addition restriction compared to traditional diets has been shown to maximize nitrogen utilization,relieve diarrhoea in piglets,and reduce feed costs.This study took weaned piglets as the research object,and studied the intestinal health and liver metabolism of weaned piglets by feeding diets with different protein sources and protein levels two weeks after weaning,aiming to explore the effects of feeding low-protein diets on piglets’ intestinal health and liver metabolism two weeks after weaning,so as to provide scientific theoretical guidance for the formulation of low-cost and high-efficiency weaned piglet diets.In this study,96 weaned piglets with an average weight of 8.53±1.68 kg were selected and randomly divided into 4 groups according to litter type,weight and sex,with 6 replicates in each group and 4 pigs in each replicate.It adopts the management mode of all-in,all-out feeding,and all-leakage ground feeding.The trial period was 28 d,and in the first stage of the test(0-14 d),the diet was treated as low soybean meal + 16% crude protein(CP)group,low soybean meal + 18% CP group,high soybean meal +16% CP group and high soybean meal + 18% CP group,and the second stage(15-28 d)was uniformly fed high soybean meal+ 18% CP diet.After the first phase of the trial,4 piglets with a weight close to the average weight of this treatment were selected for slaughter,intestinal and liver tissue samples were collected,and the effects of protein and soybean meal levels on intestinal health and liver metabolism of piglets were explored by using real-time fluorescence quantification and UPLC-MS/MS and other methods and techniques,mainly obtaining the following results:1.At the level of soybean meal,the crypt depth of piglets in the high soybean meal group was significantly higher than that in the low soybean meal group(P<0.01).The m RNA levels of tight junction proteins ZO-1 and claudin-1 in duodenal tissues were also increased(P<0.01,P<0.05).The number of piglet jejunal goblet cells(P<0.05)was significantly increased,and the expression level of mucin-2 m RNA in the piglets in the high soybean meal group was significantly higher than that in the low soybean meal group(P<0.05).At the protein level,the ileal villi height and crypt depth of weaned piglets with 18%CP level were significantly higher than those in the 16% CP group(P<0.01).Higher m RNA levels of the tight junction protein ZO-1 in duodenal tissue(P<0.05);The number of goblet cells(P<0.01)was significantly increased and the interaction between the two was significant(P<0.05).2.At the level of soybean meal,the expression level of GLP-2R m RNA in the jejunum of piglets in the high soybean meal group was significantly higher than that in the low soybean meal group(P<0.05).The expression level of IL-8 m RNA in the ileum was significantly higher than that in the low soybean meal group(P<0.05),and the expression level of TGF-β m RNA was significantly lower than that in the low soybean meal group(P<0.01).The expression level of SLC7A7 m RNA,a basic amino acid transporter in the duodenum,was significantly higher than that in the low soybean meal group(P<0.05).At the protein level,the expression level of SLC7A7 m RNA,a basic amino acid transporter in the duodenum of piglets in the 18% CP group,was significantly higher than that in the 16% CP group(P<0.01),and the expression level of SLC15A1 m RNA in the small peptide transporter was significantly higher than that in the 16% CP group(P<0.01).3.At the soybean meal level,the differential metabolite enrichment pathways between the two groups mainly were: mutual conversion of pentose and glucuronate(P<0.01),indole alkaloid biosynthesis(P<0.01),O-antigen nucleotide glycan biosynthesis(P<0.05),amino sugar and nucleotide sugar metabolism(P<0.05),serotonergic synapses(P<0.05);At the protein level,the differential metabolite enrichment pathways between the two groups were mainly nicotinate and nicotinamide metabolism(P<0.05).In summary,in the 14-day diet of piglets after weaning,when the total amount of soybean meal accounted for less than 15% of the total basic diet,the higher the soybean meal content,the better the intestinal development of piglets;High soybean meal and 18%CP can improve the intestinal morphology and intestinal barrier function of weaned piglets.Reducing the content of dietary soybean meal in weaned piglets will enhance the expression level of metabolites related to glucose metabolism pathways.6-hydroxynicotinate was significantly enriched in the 18% CP group,which improved the resistance of piglets to pathogens.