An in vitro model for caecal proteolytic fermentation potential of ingredients in broilers

Area of Science:

• Animal Nutrition
• Gut Microbiology
• Digestive Physiology

Background:

• Protein fermentation in chicken caeca can produce harmful metabolites, impacting gut health.
• Increased protein fermentation (PF) is linked to poor precaecal digestion, leading to more undigested protein entering the caeca.
• The fermentability of undigested protein based on its ingredient source is not well understood.

Purpose of the Study:

• To develop an in vitro method to predict feed ingredients that increase the risk of protein fermentation (PF).
• To assess the fermentability of undigested protein from different sources in simulated chicken caecal conditions.

Main Methods:

• An in vitro procedure simulated gastric, enteric digestion, and subsequent caecal fermentation.
• Dialysis removed amino acids and peptides <3.5 kD from the soluble fraction, mimicking intestinal absorption.
• Remaining digesta fractions were inoculated with N-free caecal microbes, measuring gas production (GP) as an indirect PF indicator.

Main Results:

• The maximum GP rate averaged 21.3 ± 0.9 ml/h, exceeding the positive control (urea) in some cases.
• Minimal differences in GP kinetics were observed among various protein ingredients.
• No significant differences in branched-chain fatty acids or ammonia concentrations were found after 24 hours.

Conclusions:

• Solubilized undigested proteins >3.5 kD are rapidly fermented by caecal microbes.
• Fermentation rate is independent of the protein ingredient source when equal nitrogen amounts are present.
• The developed in vitro method can help predict the risk of protein fermentation from feed ingredients.