The importance of particle size on organic matter and crude protein in vitro digestibility of maize and soybean meal

F. Lyu, M. Thomas, A.F.B. van der Poel, W.H. Hendriks*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Particle size plays an important role in the digestibility of nutrients by animals. Methodologies developed to simulate the digestive system to determine digestibility values require the grinding of samples to pass a specific sieve size (e.g. 1 mm) before in vitro digestion. The objective of this study was to evaluate if particle size affects in vitro (ileal) digestibility values of organic matter (OM) and crude protein (CP) in maize and soybean meal (SBM). Both ingredients were ground in a laboratory mill over four screens (1.50, 1.00, 0.75 and 0.50 mm) with trapezoidal holes in a sequential manner from large to fine. Particle size distribution, nutrient content and in vitro digestibility were determined of the various samples. With decreasing screen size, geometric mean diameter of particles significantly decreased from 351.4 to 203.2 µm for maize, and from 239.1 to 99.1 µm for SBM. Ash, CP and starch content were not affected whereas the neutral detergent fibre in maize and dry matter content in SBM differed after grinding with various sized screens (P < 0.05). The in vitro digestibility of OM and CP of maize and CP of SBM ground over the four different screens did not differ (P > 0.185). The OM in vitro digestibility differed (P < 0.05) with values for SBM ground over the 1.50 mm screen being lower (P < 0.05) than the smaller screen sizes: 0.814 (1.50 mm) vs 0.833 (1.00 mm), 0.829 (0.75 mm) and 0.834 (0.50 mm), respectively. Based on the current work and literature data, particles ≥ 595 µm of comminuted maize and SBM affect OM and CP in vitro digestibility. Analysis of three feeds and 10 feed ingredients ground over a 1.0 mm sieve showed that the fraction ≥ 595 µm can make up to 32.1% of the mass. It is recommended that before in vitro digestibility determination, particle size distribution is assessed, especially the mass fraction of particles ≥ 595 µm and further grinding is conducted to ensure that particles are < 595 µm for maize and SBM. The cut off size where particles size affects OM and CP in vitro (ileal) digestibility of other feeds or feed ingredients than maize and SBM should be determined.

Original languageEnglish
Article number115243
JournalAnimal Feed Science and Technology
Volume285
DOIs
Publication statusPublished - Mar 2022

Keywords

  • in vitro digestibility
  • Maize
  • Particle size distribution
  • Screen size
  • Soybean meal

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