A 3-wk study was conducted at a commercial feed mill in northwest Iowa to determine
where the formation of fines occurs during pelleted feed manufacturing and if differences
are present in nutrient composition between fines and pellets. During the study,
1,781pelleted feed samples were collected from 4 swine and 2 turkey diets. Samples
were collected from 4 different locations throughout the mill to determine progression
of fines formation during the manufacturing process. These locations included
the pellet mill, pellet cooler, fat coater, and at load-out. Samples were taken on 7 to 10
different runs for each diet throughout the 3-wk period. Pellet durability index (PDI)
and percentage fines were determined for all samples, and nutrient analysis was determined
on a pooled sample from each run within diet. Nutrient analysis was determined
via near-infrared spectroscopy (NIR) at the processing site and via wet chemistry at a
commercial lab.
Overall, PDI was different (P < 0.05) between locations in the mill. Pellet durability
index increased from the pellet mill to the fat coater but then decreased between the
fat coater and load-out. The largest increase in PDI was seen between the cooler and fat
coater. Percentage fines decreased (P < 0.05) from the pellet mill to the cooler, but then
increased as pellets went to the fat coater and then to load-out. The largest increase in
fines was found between the cooler and fat coater and between the fat coater and loadout
(5.6 and 6.5%). Dry matter and crude fiber were greater (P < 0.05) and fat tended
to be greater (P < 0.08) in fines than in pellets as determined by NIR, whereas CP was
significantly lower (P < 0.05) in the fines than in pellets. These differences were verified
by wet chemistry results. Wet chemistry also found that fines tended to be higher
(P < 0.05) in ADF, but fines were similar in Ca and P compared with pellets.
In conclusion, fines increased as pellets were moved from the pellet mill to the load-out
area. Pellet durability index improved from the pellet mill to the fat coater due to the
removal of moisture in the pellet but then worsened at load-out, most likely due to the
addition of fat, which may have started to soften the pellets. Both NIR and wet chemistry
found that fines were higher in fiber and fat but lower in CP than pellets. These
differences in nutrient content of the pellets compared with fines and the possibility of fines refusal at the feeder may lead to poorer pig performance. More research is needed
to determine if fines formation can be reduced in the mill and if differences in nutrient
composition of fines compared with pellets could lead to performance differences in
pigs.
