Towards better pellet quality

Janne Karin Brodin

Producing feed pellets of even and predictable physical quality is a big challenge for the feed industry. Given that the farmer buys pellets, not feed meal, it is vital that the feed remains in pellet form, and does not disintegrate too much into small particles and dust. Kari Lundblad’s PhD thesis is a step forward for the feed industry’s understanding of factors that affect pellet quality.

PhD Kari Lundblad Photo: ukjent

Processing methods and their effect on feed concentrates
The primary aim of this doctoral work has been to investigate the effects of different processing methods on physical as well as nutritional quality of the feed. Various raw materials were tested for water adsorption during conditioning with water or with steam. Steam conditioning at high and low temperatures, expander treatment and extrusion were tested for effect on technical and nutritional quality of feed pellets for nursery pigs and broiler chickens.

The PhD project has been a collaborative effort between Felleskjøpet Fôrutvikling, UMB / Department of Animal and Aquacultural Sciences, SINTEF Energiforskning AS in Trondheim and Kansas State University in the USA.

Ability for water adsorption in raw material
Chemical composition of the raw materials and the physical state of water added affects water adsorption of raw materials. The starch rich raw materials had greatest water adsorption when rehydrated in water at 80ºC, whereas the protein rich ingredients adsorbed most water in moist air. The results suggest that a combination of steam and water should be used to optimize the effect of conditioning during the manufacture of pelleted animal feed.

Depending on the ingredient composition, physical quality of feed was efficiently improved by adding water into the mixer and by use of expander conditioning. Adding water into the mixer in a barley- and a maize-based diet for pigs improved pellet quality. Expander conditioning improved pellet quality in both diets, but greatest improvement was observed for the maize-based diet. Expander conditioning and extruder processing did not improve pellet quality in a wheat-based diet. The results suggest that expander conditioning will improve pellet quality, especially when using raw materials that negatively affect pellet quality. However, ordinary steam conditioning in combination with water addition into the mixer is a low cost alternative to improve pellet quality.

Weight gain and feed efficiency
Hydro-thermal processing, and in particular extruder processing improved gain: feed in pigs. There was no advantage using extruder processing or expander conditioning compared to ordinary steam conditioning for broiler chickens, although starch digestibility was greater for broiler chickens fed the hydro-thermally processed treatments compared to the mash control.

Digestibility of starch, essential amino acid, as well as apparent ileal digestibility and standardized ileal digestibility of the essential amino acids Lys, Arg, Ile and Thr was significantly greater for pigs fed hydro-thermal processed diets compare to mash control. These improvements in digestibility may explain the improved feed utilisation observed for the hydro-thermal processed diets.

Illustration shape and colour in extruded feed Photo: Amandus Kahl GmbH

Improved understanding of factors that influence pellet quality
Pellet quality is of great financial importance in animal production, and it is a big problem that quality varies with the raw material available and from factory to factory.

By considering each raw material separately, this doctoral work has improved our understanding of what must be done to improve pellet quality when using raw materials that would normally result in poor quality pellets.

Kari Lundblad is 33 years old, and comes from Råde in Østfold municipal. She took her Cand. Agric degree in animal nutrition at IHA/UMB in 2000.

In connection with the PhD degree there have been carried out scientific work both at IHA/UMB, SINTEF Energiforskning AS in Trondheim and at Kansas State University in USA, where Lundblad stayed for about one year of the PhD period.

The trial lecture and the public defence took place Friday June 5 2009 at IHA.

Title of the thesis: Effect of diet conditioning on physical and nutritional quality of feed for pigs and chickens

Prescribed subject of the trial lecture: The fate of nutritionally important components during processing of feed and the effects on animal performance.

Lundblad's main supervisor has been Research officer Dr. Mette Sørensen, IHA/APC

Research officer Dr. Egil Prestløkken, Felleskjøpet, Professor Birger Svihus, IHA og Dr. Joe D. Hancock, Kansas State University, USAhave been assistant supervisors.

Updated: 15.06.09
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