Granulometric analysis is an analytical tool available at the CRA-W to improve the technical and zootechnical qualities of pig and poultry feed.
The purpose of granulometric analysis is to determine the mean size and distribution of the particles that make up the feed. It plays an important role with regard to the physical characteristics of feed in the form of flour: the stability of mixtures, flow in hoppers, dust emission, grinding costs during manufacture and granule solidity. It also influences livestock’s zootechnical performance: nutrient digestibility, constipation and consistency of faeces, formation and severity of gastric ulcers, prevalence of salmonella in pigs, and rate of consumption and adaptability in poultry.
Sieving is one of the oldest methods of granulometric analysis, and also one of the most widely used, as it is inexpensive. The basic principle consists of separating a pulverulent sample by passing it through several sieves whose characteristics are known. The operation determines the average particle size, the homogeneity (or heterogeneity) of the sample and the distribution of different-sized particles. In the context of the BIO2020 programme on the characterisation of feeding practices in organic pork production, a granulometry procedure was applied (E. Royer, 2002-Ifip, Institut du porc). An analysis report could then be produced for pig or poultry feed in the form of histograms and graphs.
The grain size was determined for 36 samples of organic pig feed. The results showed an average grain size that was too high for fattening pigs and too low for sows, with the heterogeneity of the samples increasing with average particle size. Very often, there were too many fine particles. Additionally, seven of the feeds for fattening pigs were too coarsely ground.
This analytical tool remains available to operators in the sector, to help improve the quality of the grinding process, which is essential for extracting the maximum value from feed.