Three-step in vitro digestion model for evaluating and predicting fecal odor emission from growing pigs with different dietary protein intakes
Journal
Animal Bioscience
Journal Volume
35
Journal Issue
10
Start Page
1592
End Page
1605
ISSN
2765-0189
2765-0235
Date Issued
2022-10-01
Author(s)
Abstract
Objective: The objective of this study was to select an effective in vitro digestion–fermentation
model to estimate the effect of decreasing dietary crude protein (CP) on odor emission
during pig production and to suggest potential prediction markers through in vitro and in
vivo experiments.
Methods: In the in vitro experiment, three diet formulations with different CP contents
(170 g/kg, 150 g/kg, and 130 g/kg) but containing the same standardized ileal digestible
essential amino acids (SID-EAA) were assessed. Each diet was evaluated by two different
in vitro gastric-intestinal phase digestion methods (flask and dialysis), combined with fresh
pig feces-ferment inoculation. Eighteen growing barrows (31.9±1.6 kg) were divided into
three groups: control diet (180 g CP/kg, without SID-EAA adjustment), 170 g CP/kg diet,
and 150 g CP/kg diet for 4 weeks.
Results: The in vitro digestion results indicated that in vitro digestibility was affected by the
gastric-intestinal phase digestion method and dietary CP level. According to the gas kinetic
and digestibility results, the dialysis method showed greater distinguishability for dietary
CP level adjustment. Nitrogen-related odor compounds (NH3-N, indole, p-cresol, and
skatole) were highly correlated with urease and protease activity. The feeding study indicated
that both EAA-adjusted diets resulted in a lower odor emission especially in p-cresol and
skatole. Both protease and urease activity in feces were also closely related to odor emissions
from nitrogen metabolism compounds.
Conclusion: Dialysis digestion in the gastric-intestinal phase followed by fresh fecal inoculation fermentation is suitable for in vitro diet evaluation. The enzyme activity in the fermentation and the fecal samples might provide a simple and effective estimation tool for nitrogenrelated odor emission prediction in both in vitro and in vivo experiments.
Subjects
Dietary Protein Manipulation
In vitro Fermentation
Odor Emission
Pig
Simulated Digestion
Type
journal article