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Formation of fines during the pelleted feed manufacturing process and the resulting differences in nutrient composition of fines and pellets
A 3-wk study was conducted at a commercial feed mill to determine where the formation of fines occurred during pelleted feed manufacturing and if differences in nutrient composition exist between fines and pellets. During the study, 1,781 pelleted feed samples representing 4,203 metric tonnes were collected from 4 swine and 2 turkey diet formulations. Progression of fines formation during the manufacturing process was determined by collecting samples immediately after the pellet mill, pellet cooler, fat coater, and at load-out. Samples were taken on 7 to 10 different runs of feed for each diet. 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. Overall, PDI was different (P<0.05; SEM=0.82) between mill sampling locations. Pellet durability index was similar between the pellet mill (77.0%) and pellet cooler exit (78.3%). From the pellet cooler exit, PDI increased (P < 0.05) to the fat coater exit (84.6%) but then decreased between the fat coater exit and load-out (84.6 vs. 81.9%). The largest increase in PDI was observed between the pellet cooler exit and fat coater exit (78.3 vs. 84.6%). Percentage fines decreased (P<0.05; SEM=0.76) from the pellet mill to cooler exit (9.44 vs 8.54%), but then increased (P<0.05; SEM=0.77) after the fat coater and from the fat coater to load-out (14.20 vs 20.46%). The largest increase in fines was observed between pellet cooler and fat coater exits and between the fat coater exit and load out (5.6 and 6.5%). For nutrient composition, DM and fat were greater (P<0.05) and ADF tended to be greater (P<0.08) in fines than in pellets. However, crude protein was lower (P<0.05) in fines than in pellets. In conclusion, fines increased from the pellet mill to load-out and PDI improved from the pellet mill to the fat coater but then was poorer at load-out. Fines were higher in fiber and fat, but lower in CP when compared to pellets.
Item, %1 |
Fines |
Pellets |
SEM |
Probability, P < |
DM |
88.83 |
88.32 |
0.16 |
0.031 |
CP |
13.58 |
15.24 |
0.48 |
0.021 |
ADF |
4.09 |
3.59 |
0.20 |
0.087 |
Ca |
0.74 |
0.74 |
0.07 |
0.975 |
P |
0.50 |
0.53 |
0.02 |
0.354 |
Fat |
9.00 |
7.71 |
0.42 |
0.039 |
1 Values represent the mean of 32 samples.
Keywords: feed mill, fines, pellets, pellet durability index