Doctor of Philosophy / Department of Animal Sciences and Industry / James S. Drouillard / A series of studies were conducted to evaluate extrusion processing of finishing diets on
growth performance, carcass characteristics, and meat quality attributes of feedlot cattle.
Extruded diets were processed in a 24:1 (length/diameter) corotating, fully intermeshing twinscrew
extruder (model BCTG-62, Bühler AG CH-9240, Uzwil, Switzerland). In Experiment 1,
extrusion processing of corn based diets decreased dry matter intake (DMI) and improved gain
efficiency (G:F) by 15% compared to heifers fed steam-flaked corn (SFC) diets. Carcass
characteristics were not different between treatments. Steaks from heifers fed SFC diets were
juicier and had a less pronounced off-flavor than steaks from heifers fed extruded diets. In
Experiment 2, average daily gain (ADG), DMI, G:F, carcass characteristics, and meat quality
attributes were not different between heifers fed SFC and extruded processed corn diets. In
Experiment 3, we evaluated different degrees of extrusion processing by altering the level of
process water added to the extruder. Mechanical energy inputs, die pressure, die temperature,
and torque of drive motor decreased as the level of water added to the extruder increased from
4% to 12%. Water addition did not affect DMI or ADG of feedlot heifers. However, live body
weight (BW) and G:F decreased as the level of process water increased. Gain efficiency
(carcass-adjusted basis) was 3% greater for extruded corn diets processed with 4% water
compared with SFC diets and was 6% poorer than SFC diets when processed with 12% water.
Apparent total tract digestibility was not different, but IVDMD improved with increasing levels
of water. Improvements in G:F when fed extruded feed was variable among the 3 studies. This
may be due, in part to severe infestation by European Starlings during Experiment 1. Impact of
feed depredation by starlings was therefore evaluated. Starlings consumed 86% of the SFC diet
offered to them compared to, none of the extruded corn diets. In addition, starlings preferentially
selected for the energy dense portion of the rations (steam-flaked corn). Therefore, it is plausible
that a portion of the 15% improvement in G:F observed in Experiment 1 for heifers fed extruded
corn diets can be attributed to differences in feed depredation by starlings. Finally, two studies
were conducted to evaluate extrusion processing of sorghum-based diets. In the first experiment,
DMI was greater and G:F was poorer for heifers fed extruded sorghum diets compared to heifers
fed steam-flaked sorghum (SFS) diets. However, carcass characteristics and meat quality
attributes were not different. In the second study, particle size of the ground sorghum added to
the extruder was evaluated. Processing sorghum to a smaller particle size (581 μm) prior to
extrusion processing decreased DMI, improved G:F, and increased apparent total tract
digestibility compared with larger particle sizes (1,264 μm). However, heifers fed SFS diets were
still more efficient that heifers fed extruded diets made with either particle size of sorghum.
Overall, this research suggests that extruding complete diets into homogeneous pellets may
improve G:F of cattle fed corn-based diets while reducing feed depredation of starlings. It is also
clear from our results that G:F is improved to a greater extent to processing diets under high shear conditions (i.e., high mechanical energy inputs) than when processed under low shear conditions.
| Identifer | oai:union.ndltd.org:KSU/oai:krex.k-state.edu:2097/4622 |
| Date | January 1900 |
| Creators | Depenbusch, Brandon E. |
| Publisher | Kansas State University |
| Source Sets | K-State Research Exchange |
| Language | en_US |
| Detected Language | English |
| Type | Dissertation |
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