Kinetics of Cell-Wall Digestion of Orchardgrass and
Alfalfa Silages Treated with Cellulase and Formic Acid1,*
E.M.G. NADEAU,*v3 D. R. BUXTON,*!4 E. LINDGREN,t
and P. LlNGVALLt
‘Iowa State University, Ames 50011
tDeparlment of Animal Nutrition and Management,
The Swedish University of Agricultural Sciences,
23 Uppsala. Sweden
The objectives of this study were to determine the
effects of cellulase (from
combined with formic acid, applied before ensil-
ing, on the subsequent concentration and composition
of the cell wall and on the extent and rate of in situ
cell-wall digestion of orchardgrass
L.) and alfalfa
L.). Treated and
control forages of both plant species were ensiled for
at least 60 d before being ruminally digested by two
fistulated cows. Analyses of NDF, ADF, and acid de-
tergent lignin were conducted sequentially on original
and digested samples. Data were fitted with
order, nonlinear model to estimate extents and rates
of digestion of potentially digestible NDF, cellulose,
and hemicellulose. The concentration of indigestible
residue and the discrete lag time before digestion
were also determined for the cell-wall components.
After ensiling, the mean NDF concentration of
treated silages was 19% lower than that of control
silages; the effect was greater for orchardgrass than
for alfalfa. The extent of digestion of NDF, cellulose,
and hemicellulose, respectively, was
lower for treated silages than for control silages.
Treatment effects on the extent of digestion varied
between plant species. Cellulose from treated or-
chardgrass was digested 19% more slowly than cellu-
lose from the control silage. Indigestible residue con-
centrations of NDF, cellulose, and hemicellulose,
Received July 24, 1995.
1Joint contribution of the Field Crops Research Unit, US Dairy
Forage Research Center of USDA-ARS, and Iowa State University.
Journal Paper Number 5-16455 of the Iowa Agriculture and Home
Economics Experiment Station. Project Number 2709.
2Names are necessary to report factually on available data;
however, the USDA neither guarantees nor warrants the standard
of the product? and the use of the name by the USDA implies no
approval of the product to the exclusion of others that may also be
3Department of Agronomy.
4Address reprint requests to D. R. Buxton, USDA-ARS, 1577
Agronomy Hall, Iowa State University, Ames 50011.
respectively, were 7,
lower in treated
silages than in control silages. Thus, extensive cell-
wall degradation by cellulase during ensiling resulted
in less digestible cell-wall material for ruminal diges-
tion but greater total cell-wall degradation, including
that during ensiling and ruminal incubation, espe-
cially during early digestion in the rumen.