1. Adjusting Roller Settings Based On Kernel Size Improved Starch Digestibility Of
Dry-Rolled Barley Grain
M. Ahmad1
, M. Oba1
, D. Gibb2
, and T. A. McAllister2
University of Alberta, Edmonton, Alberta, Canada1
, Agriculture and Agri-Food Canada, Lethbridge, Alberta, Canada2
Background Methods Results
Objective
Conclusion
To evaluate the effect
of adjusting roller
settings based on
kernel size on in situ
starch digestibility of
dry rolled barley.
Figure 1. The in situ starch digestibility of dry-rolled barley with two different
roller setting methods; multiple roller setting (MRS) vs. single roller setting
(SRS). Samples were incubated in the rumen of cow for six time points (0, 3, 6,
12, 24, and 48 h).
The in situ starch digestibility was greater (P < 0.01) for
MRS method compared with SRS method (Table. 1).
 Starch digestibility at 48 h incubation time was not
affected (P = 0.76) by treatment.
The rate of in situ starch digestion was also greater
(P = 0.05) for MRS method (18.6 vs. 11.9 % h-1
) than
SRS method.
Screening of barley grain prior to processing, and
adjusting roller settings based on its kernel size improve
the rate of starch digestion in the rumen and may
improve the efficiency of grain utilization possibly by
reducing unprocessed grains in the diets.
References: Karkallas, J. 1985. An improved enzymatic method for the determination of native and modified starch. J. Sci. Food Agric. 36: 1019–1027.
Khorasani, G. R., J. Helm, and J. J. Kennelly. 2000. In situ rumen degradation characteristics of sixty cultivars of barley grain. Can. J. Anim. Sci. 80: 691-701.
Table 1: The in situ Starch digestibility of dry-rolled barley at two different
roller settings methods
MRS SRS SEM P value
0h digestibility % 22.8 14.9 1.09 <0.01
3h digestibility % 55.0 38.6 1.8 <0.01
6h digestibility % 62.6 54.4 1.94 0.01
12h digestibility % 78.9 69.7 1.24 <0.01
24h digestibility % 85.3 83.1 0.75 0.05
48h digestibility % 93.1 93.4 0.54 0.76
Rate of digestion (k)
%/h 18.63 11.9 0.82 <0.01
MRS = Multiple roller settings method; SRS = Single roller setting method; SEM =
Standard error mean
 Whole barley is hardly digested due to its hard
pericarp.
 Processing increases microbial attachment to starch
content of the grain.
 Barley grain naturally varies in kernel size (Khorasani
et al., 2000).
 Single roller setting may not be effective for various
kernel sizes.
 Dry rolling with single roller setting;
May not provide uniform particle size.
Large kernel may shatter and produce more fines.
Small kernels may pass as unchanged.
May decrease efficiency of the roller mill.
Restrict ruminal micro flora to act on starch.
Decrease starch digestibility in the rumen.
May decrease animal performance.
 Adjusting roller settings based on kernel size;
May decrease variation in particle size.
Decrease percentage of unprocessed grains.
Decrease percentage of fines.
Increase surface area for microbial attachment.
Increase starch digestibility in the rumen.
 Twenty cultivar lots of barley samples were dry-rolled
using two methods;
 Multiple-roller-setting (MRS) method with Processing
index (77%).
 Single-roller-setting (SRS) method with Processing
index (87%).
 In MRS method, grain samples were screened through
7, 6 , and 4 mm sieves.
 Spaces for roller mill were set at 1.487, 1.194, and
1.000 mm for large (> 7 mm), medium (> 6 mm), and
small kernels (> 4 mm), respectively.
 In SRS method, the samples were dry-rolled through
the roller space of 1.194 mm.
 Samples in Nylon bags were placed in the rumen of
cow for 6 time points.
 Samples were analyzed for starch using Karkallas et
al. (1985) procedure.
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60
Incubation Time ( h )
StarchDigestibility%
MRS
SRS
 Statistical analysis:
Data were statistically analyzed using
ANOVA procedure of JMPRolled barley