Hammer-milling maize and soybean meal: Physical and nutritional characteristics of particles

Feed processing involves the use of various technologies to transform feed ingredients into valuable feeds enabling the production of animal-sourced foods (e.g. meat, eggs, milk). Hammer-milling, a standard technology used in the feed industry, is a critical process affecting feed efficiency and animal production. After grinding, the particle size of ingredients is reduced, the physical characteristics of particles and nutrient distribution are changed, which can affect the digestibility and kinetics of nutrient digestion.

The research described in this thesis provides hitherto unknown insights into the breakage of maize and soybean meal as a result of hammer-milling via physical and chemical characteristics as well as in vitro digestibility of nutrients of size-fractionated particles. Moisture content and mixture ratio effects of feed ingredients on the breaking behaviour were also investigated enabling the development of novel grinding strategies to produce feeds with higher nutrient digestibility. This thesis provides important data on the importance of sample preparation before in vitro digestion analysis to improve the prediction and repeatability of nutrient digestibility estimates.