Feed Strategy - November 2019 - 38

38 ❙ FeedStrategy
PARTICLE SIZE IN ANIMAL FEED
retentioning, more moisture can
be absorbed, and the particles can
be heated more thoroughly. Forces
acting on these soaked particles lead
to less fractures and more elastic
deformation, resulting in a reduced
grinding effect with increasing
retention time.

Pellet mill size
During the study, it was observed
that the grinding effect during
pelleting decreases as the size of the
equipment increases. With a larger
die diameter, the circumferential
die speed usually decreases. Thus,
the rolls run over the particles less
often and the motion of the feed
mash inside the die hole is therefore
higher per roll overrun. Furthermore,
the angle of nip changes due to the
increase in the die- and roll-diameter,
which is why intake and pre-compaction are gentler.

Influence of particle size
on pelleting
The influence of pelleting on
particle size has been discussed;
however, the initial particle size also
has a significant influence on the
pelleting process and especially on
pellet quality.
During conditioning and
compaction, liquid and solid bridges
on the particle surface are formed.
Coarse particles are a source of
pellet fracture because they have

a smaller surface area and are less
solid, which means that liquid
bridges form on their surface. The
risk of transverse cracks increases
with increasing particle size in relation to the die diameter.
In contrast, fine particles act like
glue and form a better and tighter
framework due to the larger overall
surface area where single particles stick
to each other due to cohesive forces.
Therefore, pellet quality improves with
decreasing particle size.

The importance of particle
size during pelleting for
animal nutrition
As particles size should preferably be fine to achieve high pellet
quality, a conflict occurs regarding
nutritional requirements, especially
where poultry feed is concerned. For
chickens, coarse particles are required
to achieve good animal performance.
But these coarse particles have fewer
binding properties and the pellets
break easier, creating fines and therefore increasing feed loss.
The grinding effect during
pelleting is generally not taken into
account. Particle size is only determined after grinding, whereas the
actual particle size in the pellets is
smaller than the required size.
By combining knowledge
about the physiological requirements of animals and the effects of
processing using process control,

Figure 3: Fine particles act
like glue, achieving high
pellet quality (a), while coarse
particles can be a source of
fracture in the pellet and lead to
low pellet quality (b).
Courtesy Bühler Group

particle size adaptation can be an
ideal tool for optimizing animal
performance and health, as well as
improving feed production. ■
Editor's note: This is the final
installment of a five-part series,
"All about particle size: the influence of feed particle size on animal
performance," contributed by the
Bühler Group. It aims to explain
the importance of particle size in
pig and broiler feed and explore
the possibilities for modifying and
controlling particle size during feed
processing.

Meike Rühle is a process engineer with the Bühler Group.

www.FeedStrategy.com ❙ November 2019


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Feed Strategy - November 2019

Table of Contents for the Digital Edition of Feed Strategy - November 2019

Feed Strategy - November 2019
Contents
In the Mix
FeedStrategy.com
Climate change and animal feed: mycotoxin risk mitigation
How to adapt to the changing mycotoxin landscape
Scientists seek new ways to combat spread of mycotoxins
Feed additives that will succeed in 2020 and beyond
Marketing nutrition by extending credit
More feed, fewer mills: feed industry consolidation
How to target protein content in late-lactation cow diets
Critical junctures in early chick nutrition confi rmed
How pelleting influences particle size in animal feed
Products
Advertisers’ Index
Feed Strategy - November 2019 - CT1
Feed Strategy - November 2019 - CT2
Feed Strategy - November 2019 - Feed Strategy - November 2019
Feed Strategy - November 2019 - Cover2
Feed Strategy - November 2019 - CT3
Feed Strategy - November 2019 - CT4
Feed Strategy - November 2019 - Contents
Feed Strategy - November 2019 - In the Mix
Feed Strategy - November 2019 - FeedStrategy.com
Feed Strategy - November 2019 - Climate change and animal feed: mycotoxin risk mitigation
Feed Strategy - November 2019 - 5
Feed Strategy - November 2019 - 6
Feed Strategy - November 2019 - 7
Feed Strategy - November 2019 - How to adapt to the changing mycotoxin landscape
Feed Strategy - November 2019 - 9
Feed Strategy - November 2019 - 10
Feed Strategy - November 2019 - 11
Feed Strategy - November 2019 - Scientists seek new ways to combat spread of mycotoxins
Feed Strategy - November 2019 - 13
Feed Strategy - November 2019 - 14
Feed Strategy - November 2019 - 15
Feed Strategy - November 2019 - Feed additives that will succeed in 2020 and beyond
Feed Strategy - November 2019 - 17
Feed Strategy - November 2019 - 18
Feed Strategy - November 2019 - 19
Feed Strategy - November 2019 - 20
Feed Strategy - November 2019 - 21
Feed Strategy - November 2019 - Marketing nutrition by extending credit
Feed Strategy - November 2019 - 23
Feed Strategy - November 2019 - More feed, fewer mills: feed industry consolidation
Feed Strategy - November 2019 - 25
Feed Strategy - November 2019 - 26
Feed Strategy - November 2019 - 27
Feed Strategy - November 2019 - How to target protein content in late-lactation cow diets
Feed Strategy - November 2019 - 29
Feed Strategy - November 2019 - 30
Feed Strategy - November 2019 - Critical junctures in early chick nutrition confi rmed
Feed Strategy - November 2019 - 32
Feed Strategy - November 2019 - 33
Feed Strategy - November 2019 - How pelleting influences particle size in animal feed
Feed Strategy - November 2019 - 35
Feed Strategy - November 2019 - 36
Feed Strategy - November 2019 - 37
Feed Strategy - November 2019 - 38
Feed Strategy - November 2019 - Products
Feed Strategy - November 2019 - Advertisers’ Index
Feed Strategy - November 2019 - Cover3
Feed Strategy - November 2019 - Cover4
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