Progressive response of large intestinal bacterial community and fermentation to the stepwise decrease of dietary...

Area of Science:

• Animal Nutrition
• Microbiology
• Gut Health

Background:

• Dietary crude protein (CP) levels significantly influence the gut microbiome and its metabolites in growing pigs.
• Balancing essential amino acids (EAA) is crucial when reducing dietary CP to meet nutritional requirements.

Purpose of the Study:

• To investigate the effects of varying dietary crude protein (CP) levels, balanced with essential amino acids (EAA), on the intestinal bacterial community and their metabolites in growing pigs.
• To determine the optimal CP level for promoting a healthy gut environment in pigs.

Main Methods:

• Forty growing pigs were fed diets with four different CP levels (20.00%, 17.16%, 15.30%, 13.90%) for 4 weeks.
• Crystalline amino acids were added to ensure EAA requirements were met across all treatments.
• Ileal, cecal, and colonic digesta and mucosa samples were collected for bacterial analysis (diversity, population counts) and metabolite profiling (SCFAs, ammonia, amines).

Main Results:

• Moderate CP reduction (LP, MP groups) increased bacterial diversity in the colon and ileal mucosa compared to normal (NP) and extremely low CP (ELP) diets.
• Bifidobacterium populations decreased linearly with reduced CP, while Escherichia coli increased in the ELP group.
• Short-chain fatty acid (SCFA) patterns varied, with ileal SCFAs increasing and cecal/colonic SCFAs decreasing as CP reduced. Ammonia levels decreased linearly with CP reduction.

Conclusions:

• Moderate reduction in dietary CP, when balanced with EAA, can enhance large intestinal bacterial community structure and fermentation.
• Extremely low CP diets negatively impact gut bacteria and metabolites, suggesting a threshold for beneficial CP reduction.
• Dietary CP levels significantly modulate gut microbial composition and function in growing pigs.