The effect of type of additive on rumen fermentation and digestion of
grass silage in cattle

Aila Vanhatalo, Tuomo Varvikko and IlmoAronen

Vanhatalo, A., Varvikko, T. & Aronen, I. 1992.The effect of type of additive on
rumen fermentation and digestion of grass silage in cattle. Agric. Sci. Finl. 1:163-
175. (Agric. Res. Centre of Finland, Inst. Anim. Prod., SF-31600 Jokioinen,Finland.)

Four grass silages made from a second cut cocksfoot-timothy grass were ensiled with
the application of water, i. e., without additive (NA), formic acid (FA), lignosulfonate
+ formic acid + acetic acid (LFA) and cellulase + glucose oxidase enzymes (E), The
silages were fed at maintenance level to four dry cows, which had been equipped with
a rumen cannula and a simple T-shaped duodenal cannula, in a digestibility experiment
designed as a 4x4 latin square. The silages and a mixture of barley and oats (1:1) were
given at a ratio of 70:30 on a dry matter basis.
All the silages were well preserved, but fermentation in the silo was more restricted

in silages ensiled with acid-based additives. The enzyme treatmentresulted in reduced
levels of cell wall contents compared to the other silages. The apparent digestibilities
oforganic matter (OM) and neutral detergent fibre with E silage were higher (P<0.05)
than with the other silages. The microbial N flow at the duodenum was significantly
higher (PcO.OOl) with the LFA diet compared to the other diets (NA 52; FA 53; LFA
66 and E 47 g N/d) and the efficiency of microbial protein synthesis tended to be lower
with the E diet compared to the other diets (NA 31; FA 31; LFA 38 and E 20 g N/OM
apparently digested in the rumen).

The molar proportion of acetate in the rumen was significantly higher (PcO.OOl) and
the proportion of propionate significantly lower (PcO.OOl) with acid silages than with
E and NA silages. The proportion of butyrate was significantly higher with E silage
compared to the others.

Key words: enzymes, acids, microbial protein, rumen degradation,mobile bag

Introduction

Ensiling grass into silage aims at maintaining the
high nutritional value of original grass. This can be
done using acids to create an environment with a
sufficiently low pH within a shortperiod of time to
stagnate the biological activities in the grass. Alter-
natives to acid additives include so-called biologi-
cal additives, e.g. lactic acid bacteria or fibre de-
grading enzymes, which develop an acidic environ-
ment through fermentation during the ensiling.

In Finland acid-based additives have been pre-
dominantly used during the past few decades in
silage making to ensure sufficiently good grass
silage for high-quality milk products, even for
cheese making. However, as acid additives are
corrosive to machinery and not user-safe, there is
an increasing tendency to reduce the use of acids in
silage making by replacing them with biological
additives.

Thus, a number of trials have been carried out to
study theresponse ofcattle to grass silages preserv-

163

Agric. Sei. Fint. 1 (1992)

https://www.c-info.fi/en/info/?token=M93C6TyY3ov9Sj8w.DBW426uhWXT-zuRMHZ-Prg.ngvifmhtlWT2mdnmNscQho_M_a-qwnu5YnYLd9yyfSOnej9O8F2CEonAW8sBwe2J18MbbnUb8i0Zay6ejal4uvwDf6ZWWv0Wpmtw1IYM5DkkgInMEP2E34cHqQoDXo3nTgSKHQ57lRXxpTM1pDJ5_XrtgV8Rf9-tS1d8mKvf6Zt58_AR06CPmb_TMYKswkhSfXqpduxKqy9VRIINcSVRdVq7PSNB5gG0SOH7veh5isFHSJ4qtGSQ4R7utxXx5iBP95UDiZcXTalN_ybAW6F6ufkN8gh62WladnAdDpSbdI7O39TzEA


ed using biological or acid-based additives (e.g.
Gordon 1989,Heikkilä et al. 1989,Jaakkola and
Huhtanen 1990, Jaakkola et ai. 1990, Kennedy

1990, Heikkilä et ai. 1991). However, there are
only few reports (Jaakkola et al. 1991,Jacobs and
MeAllan 1991, van Vuuren et al. 1991) compar-
ing the digestibility and rumen fermentation pat-
terns of grass silage preserved with acid and bio-
logical additives. The purpose of the present expe-
riment was to compare digestibility, rumen fermen-
tation, and ruminal and intestinal degradability of
grass silages preserved withacid or biological addi-
tives.

Material and methods

Experimental silages

The experimental silages were prepared from a
second cut cocksfoot (Dactylis glomerata)-timothy
(Phleum pratense) grass by a flail harvester using:

no additive (NA)
AIV-2 (Valio Finnish Co-operative Dairies'

Association) 5.5 1/t, containing 80 % (w/w) formic
acid and 2 % orthophosphoric acid (FA)

- Farmi-solution (Farmos-Group Ltd.) 5,6 1/t,
containing 50 % lignosulphonate, 25 % formic acid
and 25 % acetic acid (LFA)

- Clampzyme (Finnish Sugar Ltd.) 0.2 1/t, con-
taining cellulase and glucose oxidase enzymes (E)

All the additives were applied by a pressure
pump at cutting using the application rates recom-
mended by the manufacturers. The silages were
ensiled in fibreglass silos of 3 m 3 for seven months.

Animals and their feeding

The four non-pregnant and non-lactating cows (live
weight 550 kg) of Finnish Ayrshire breed used in
the experiment were equipped with a rumen can-
nula and a simple T-piece duodenal cannula. The
animals were fed in a balanced 4x4 latin square
close to maintenance level (Salo et al. 1982), the
diets consisting of experimental grass silages
supplemented with a mixture of barley and oats

(1:1). The ratio of forage to concentrate was 70:30
on a dry matter (DM) basis. The animals were fed
twice daily in equal amounts at 12 h intervals. A
commercial mineral supplement was included in
the diet and water was freely available.

Experimental procedures

The length of each experimental period was 28
days with a 10-day adaptation period. Representa-
tive samples of the grass silages and concentrate
mix were obtainedfrom each experimental period.

The flow of nutrients to the small intestine was
estimated using the graphic alternative (McAllan
and Smith 1983) of the double-marker method
(Faichney 1975). Cr-mordanted straw and LiCo-
EDTA prepared as describedby Udén et al. (1980)
were used as a marker for the solid and liquid phase
ofdigesta. Cr-mordanted straw was administered to
the rumen from day 8 twice a day (2 x 7.5 g) and
LiCo-EDTA (sg/d) was infused continuously into
the rumen from day 9 onwards.

Duodenal digesta was spot-sampled on days 17,
18 and 19. Samples (150 ml) were collected at three
hours' intervals, four times a day, starting at 8, 9
and 10 o'clock on consecutive collection days. The
spot samples ofeach animal were pooled to provide
one composite unrepresentative digesta sample.
One half of this sample was centrifuged (700 x g/ 10
min) to separate the particulate and liquid phases.
The particulate phase and the other half of the
digesta sample were dried at 60 °C and milled to
pass a 1 mm screen. The liquid phase was stored at
-20 °C before analysis.

In order to determine the overall digestibility of
nutrients using acid-insoluble ash as a natural
marker, faecal grab samples were taken twice a day
from day 14 to day 18 when feeding the animals.

To estimate the rumen liquid outflow rate, a
single dose of LiCo-EDTA (8 g) was infused into
the rumen during one feeding interval. The infusion
was started at evening feeding on day 19 and con-
tinued till the next morning feeding. On day 20, the
ruminal and duodenal digesta samples were col-
lected before morning feeding and at 1.5 hours'

164

Agric. Sei. Finl. 1 (1992)



intervals thereafter during the daytime feeding
cycle. The liquid phase of the samples was separ-
ated and stored as described above.

Nitrogen of microbial origin in duodenal N was
measured using purine bases ofnucleic acids as mar-
kers (Zinn and Owens 1986). The contents of the
purine bases in the microbial mass were analyzed
from the rumen samples collected on day 21 imme-
diately before morning feeding and four hours the-
reafter. The microbial mass was isolated by separa-
ting the rumen liquid as described earlier and by furt-
her centrifuging (26000 x g/20 min) the supernatant.

To measure rumen fermentation, samples of
rumen fluid were collected on day 21 right before
feeding and 0.5, 1,2, 3,4, 6, 8 and 10 h after feed-
ing. The ammonia-N and pH of the digesta were
measured immediately, and samples for the mea-
surement of volatile fatty acids (VFA) were stora-
ged withAg20 in a refrigerator for later analysis.

To determine the rumen degradability and subse-
quent intestinal degradability of the experimental
silages, nylon bag techniques were used. Each
experimental silage was incubated in the animal fed
with that particular silage diet. Five nylon bags (60
x 120 mm) made of polyester (PES 41 pm/33 %,

Polymon, Switzerland) containing fresh, chopped
(< 10 mm) silage (2.5 g DM) were inserted into the
rumen on day 14 and incubatedfor periods of 2,4,
8, 16, 24, 48, 72 and 96 h. After removal, the bags
were machine-washed and dried at 60 °C in a
forced-draught oven.

Fifteen mobile bags (35 x 50 mm, PES 10 pm/2
%/C) per experimental silage were introduced into
the duodenumfrom day 14 onwards. Each bag con-
tained 0.8 g DM freeze-dried or rumen-incubated
(30 h) silage, that was milledthrough a 2 mm mesh.
One animal received a maximum of20 mobile bags
per day. Subsequently, the bags were collected
from the faeces and machine-washed (40 °C) and
dried at 60 °C.

Chemical analyses

The DM content of the grass silages was deter-
mined by oven-drying (105 °C), correcting the

values for volatile losses according to Huida et al.
(1986). Organic matter (OM) content was measu-
red by ashing at 500 °C for 2 h and total N by the
Kjeldahl method. Determinations of neutral deter-
gent fibre (NDF) and acid detergent fibre (ADF)
were made according to Van Soest (1963) and
Van Soest and Wine (1967), calculating the con-
tent of hemicellulose as the difference between
NDF and ADF and the content of lignin as the dif-
ference between ADF and cellulose. Experimental
silages as well as rumen liquor and the liquid phase
of duodenal digesta were analyzed for ammonia-N
(McCullough 1967). Silages and rumen liquor
were further analyzed for VFAs (Huida 1973).
Also the lactic acid concentration (Barker and
Summerson 1941)and water soluble carbohydrates
(WSC) (Somogyi 1945) in the silages were measu-
red. Nucleic acids in the microbial fraction and
duodenal digesta were determined according to
Zinn and Owens (1986). Chromium and cobalt
concentrations in faecal and digesta samples were
determined by atomic absorption spectrophoto-
metry (Williams et al. 1962).Faecal samples were
analyzed also for acid-insoluble ash (Van Keulen
and Young 1977).

Calculations and statistical analysis

The duodenal flow of nutrients was calculated
based on the amounts of Co and Cr excreted in
faeces. The liquid outflow rate from the rumen was
calculated as the slope of theregression of the natu-
ral logarithm ofthe Co concentration against time.
The total outflow of liquid at the duodenum was
calculated as the difference between total digesta
flow and DM flow. The estimate of rumen volume
was calculated as total outflow (l)/[liquid dilution
rate (1/h) x 24 (h)].

The rumen degradability of feed N in vivo was
estimatedby assuming an endogenous N flow of 15
% of the duodenal N flow (Tamminga et al. 1989).

To characterize the rumen degradability of the
experimental silages, their degradability values
were fitted in to the following equations (McDo-
nald 1981):

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Agric. Sei. Finl. 1 (1992)



p=a' up to time t
o

p 2=a+b{ l-c*) from timeto onwards,
where a 1 represents the rapidly degradable fraction
of the feed during the washing ('0 h wash'), p 2 is the
proportionate disappearance of feed after time t (h)
(t>t o

) and a, b and c are the constants for the in-
stantly degradable and slowly degradable fraction
of the feed and rate ofdegradation of the latter from
time t onwards. The lag time, t o, was calculated as:
t=Mc In\h/(a+h-a)\.

The values obtained for N were corrected for
microbial contamination as suggested by Lindberg

(1988).
The total tract degradability (TTD) of the feeds

was calculated as a sum of the 30-h ruminal degra-
dation and the subsequent intestinal degradation of
the undegraded feed residue.

The standard analysis of variance appropriate to
the latin square design was applied to digestibility
and nylon bag data using the Tukey's test for treat-
ment comparisons.

Rumen fluid data was analyzed by analyses of
variance using the following model:

= H-+ Ai +PJ
+Tk

+ eijk +H I + AH i,
+ PHji +

+ eijklm’
where A, P, T and H stand for the effects ofanimal,
period, treatment and sampling time, respectively,
and e.... the residual error term. e... was used as anijkltn ijk

error term for testing the main effects A, P and T.

Dilution rate data were analyzed using the same
model as withrumen fluid data, with the exception
that the effect of sampling site replaced sampling
time in the model. Tukey's test was used for the
comparison of the treatments.

Table 2. The fermentation characteristics of the silages pre-
served with different additives.

Silage additive Grass

NA FA LFA E

pH 4.1 4.2 4.1 4.1

In dry matter
(g/kg dry matter)

WSC 18 89 18 24 91
Lactic acid 92 11 60 86
Acetic acid 14 7 20 10
Formic acid - 21 8
Total acids 106 39 88 96
Ethanol 5 11 19 8

Lactic/Acetic 6.9 1.7 3.1 8.6

In total N (g/kg)
Ammonia N 47 18 45 55
Soluble N 541 432 467 499 22

For silage additives, see text.
WSC, water soluble carbohydrates.
None of the silages contained propionic or butyric acid.

Table 1.The chemical composition (g/kg dry matter) of the silages, grass and concentrate.

Silage additive Grass Concen-
NÄ FA LFA E trate

Dry matter, g/kg 177 196 175 187 173 888
Ash 100 93 99 95 95 28
Nitrogen 28 28 29 28 27 19
NDF 531 541 541 508 589 269
ADF 320 319 319 299 305 90
Cellulose 280 280 279 260 262 70
Hemicellulose 211 221 221 207 284 179
Lignin 40 39 40 40 43 20

For silage additives, see text.
NDF, neutral detergent fibre; ADF, acid detergent fibre.

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Agric. Sei. Finl. 1 (1992)



Results

Chemical composition and fermentation
of the silages

The chemical composition (Table 1) and fermenta-
tion (Table 2) of the silages were clearly affected
by the additive used. The DM content was highest
in FA silage, and E silage had the lowest contents
ofcell walls. Compared withE and NA silages, fer-
mentation was restricted during ensiling by the
acid-based additives, particularly FA. The content
of WSC in FA silage was close to that in original

grass, and ammonia-N and total acid content was
low compared with the other silages.

Intake and digestion of organic matter and
fibre

There was no difference (P>0.05) in OM intake or
in faecal OM between the silages (Table 3). How-
ever, compared with the other silages, the amount
of OM entering the duodenum was lower (P<0.01)
in E silage and the microbial OM higher (PO.OOl)
in LFA silage. Digestibility of OM in the rumen,
disappearance of digestible OM before the intes-

Table 3. The effect ofsilage additive on organic matter (OM) and cell wall digestion.

Statistical
Silage additive... NA FA LFA E SEM significance

ofadditive

Organic matter (g/24h)
In feed 4633 4714 4886 4746 67.9 NS
At duodenum 2907 b 2994 b 3101 b 2339 a 80.7 **

Microbial OM§ 580 a 590 a 729 b 520 a 18.3 ***

In faeces 1040 1078 1127 978 31.9 NS

Digestibility in the rumen
Apparent 0.370 a 0.366 a 0.364 a 0.510 b 0.0227 **

Truet 0.496 a 0.493 a 0.512 a 0.619 b 0.0213 *

Disappearance of digestible
OM before intestine
Apparent 0.477 a 0.476 a 0.473 a 0.642 b 0.0293 *

True 0.640 a 0.640 a 0.666 ab 0.779 b 0.0275 *

Apparent digestibility 0.774 0.771 0.769 0.794 0.0052 *

Neutral detergent fibre (g/24h)
In feed 2253 ab 2329 ab 2441 b 2230 a 41.9 *

At duodenum 675 697 711 561 32.8 NS
In faeces 586 595 615 516 23.4 NS

Digestibility
Rumen 0.699 0.699 0.708 0.750 0.0109 *

Total 0.738 0.743 0.747 0.769 0.0093 NS

Total digestibility
Hemicellulose 0.709 0.717 0.710 0.741 0.0101 NS
Cellulose 0.799 0.798 0.815 0.823 0.0100 NS

For silage additives, see text.
§ Assuming a N:OM ratio ofmicrobial matter 0.09 (Czerkawski 1986).
t Corrected according to microbial organic matter.
a,b Means in the same row with different superscripts were significantly different (P<0.05).
NS, not significant; *, P<0.05; �*, P<0.01; ***, P<o.ool.

167

Agric. Sei. Finl. 1 (1992)



tine, and apparent total OM digestibility were
highest (P<0.05) with E treatment. The intake of
NDF and ADF (data not shown) was lower and
their digestion in the rumen or in the total tract tend-
ed to be higher with E-treated silage than with the
other silages (Table 3). Total digestibility of hemi-
cellulose and cellulose tended to be highest with E
treatment as well.

Intake and digestion of nitrogen

Nitrogen intake, faecal N and apparent digestibility
of N were similar (P>0.05) for all the diets (Table
4). Non-ammonia-N (NAN) and feed N entering
the small intestine were lower (P<0.05) for E treat-
ment as compared with the others, while microbial
N was highest (PO.OOl) and microbial N synthesis
most efficient (P<0.05) for LEA treatment. Silage-
N degradability was lowest in FA silage.

Ruminal and intestinal degradability of silages

Except for the potential degradability (a+h) of cell
walls (P<0.05), no statistically significant differ-
ences were found between the silages in the con-
stants describing the degradability of OM, NDF or
N in the rumen. However, there was a tendency
towards lower a and higher b values, and effective
protein degradability (EPD) was always lower for
silages ensiled with acid-based additives (Table 5).
The correction of EPD values for microbial protein
according to Lindberg (1988) increased all the
values notably, the EPD for FA silage being signi-
ficantly (P<0.001) lower than that of the other si-
lages.

No statistically significant differences (P>0.05)
were found in lag time, 30-h rumen degradation,
intestinal degradation, or total degradation of the
nutrients between the silages.

Table 4. The effect ofsilage additive on N intake, flow ofN to the duodenum and efficiencies ofmicrobial protein synthesis.

Statistical
Silage additive... NA FA LFA E SEM significance

ofadditive

Nitrogen (g/24h)
In feed 127 129 138 132 2.6 NS
At duodenum
Total-N 174b 179 b 188 b 138 a 5.1 **

Ammonia-N 4 5 6 3 0.5 NS
NAN 169b 174 b 182 b 135 a 5.0 **

Microbial N 52 a 53 a 66 b 47 a 1.7 ***

FeedN§ 91b 94 b 89 b 67 a 4.5 *

In faeces 30 32 32 30 1.3 NS

Apparent digestibility 0.762 0.753 0.765 0.772 0.0090 NS

Silage-N degradability 0.284 0.271 0.353 0.492 0.0050 *

NAN at duodenum/N intake 1.34 b 1.35 b 1.32 b 1.02 a 0.005 *

Microbial N g/kg OMADRt 31 ab 31 ab 38 b 20 a 2.5 *

Microbial N g/kg OMTDR} 23 b 23 b 26 b 16 a 1.3 **

Microbial N g/kg DCHO/ 19 b 19b 23 c 16 a 0.5 ***

For silage additives, see text.
§ assuming endogenous flow ofN to be 15 % of duodenal N flow (Tamminga et. al. 1989).
f Organic matter apparently digested in the rumen.
{ Organic matter truly digested in the rumen.
/ Digestible carbohydrates.
a,b Means in the same row with different superscripts were significantly different (P<0.05).
NS, not significant; *, P<0.05; **, P<0.01; ***, P<o.ool.

168

Agric. Sei. Finl. 1 (1992)



Table 5. The rumen degradation characteristics (a, constant for the instantly degradable fraction; b, constant for the slowly
degradable fraction; c, rate of degradation of b) of silage organic matter, neutral detergent fibre and nitrogen and intestinal
degradation of their rumen undegraded feed residues.

Statistical
Silage additive... NA FA LFA E SI M significance

of additive

Organic matter
Rumen degradation parameters

a 0.240 0.165 0.192 0.227 0.0212 NS
b 0.622 0.685 0.659 0.626 0.0196 NS
a+b 0.862 0.850 0.851 0.853 0.0038 NS
c 0.062 0.058 0.056 0.064 0.0059 NS

Lag time (h) 1.7 1.8 1.9 2.3 0.59 NS

Degradability of feed
in the rumen/ 0.720 0.685 0.695 0.703 0.0160 NS
in the intestine§ 0.102 0.112 0.102 0.112 0.0076 NS
in the total tract 0.749 0.720 0.727 0.737 0.0132 NS

Neutral detergent fibre
Rumen degradation parameters

a -0.035 -0.110 -0.091 -0.133 0.0274 NS
b 0.842 0.902 0.882 0.910 0.0251 NS
a+b 0.807 b 0.792ab 0.791ab 0.777 a 0.0050 *

c 0.059 0.057 0.054 0.062 0.0054 NS
Lag time (h) 2.0 2.1 2.2 2.9 0.45 NS

Degradability of feed
in the rumen/ 0.592 0.556 0.554 0.542 0.0254 NS
in the intestine§ 0.061 0.064 0.063 0.063 0.0065 NS
in the total tract 0.614 0.584 0.581 0.574 0.0228 NS

Nitrogen
Rumen degradation parameters

a 0.435 0.315 0.398 0.452 0.0436 NS
b 0.487 0.607 0.528 0.468 0.0378 NS
a+b 0.922 0.922 0.926 0.920 0.0079 NS
c 0.085 0.072 0.074 0.077 0.0071 NS
EPDf 0.779 0.730 0.757 0.777 0.0123 NS
EPDt 0.912 b 0.875 a 0.896 b 0.912 b 0.0047 ***

Lag time (h) 4.1 1.9 1.8 2.0 1.07 NS

Degradability of feed
in the rumen/ 0.864 0.829 0.843 0.842 0.0105 NS
in the intestine§ 0.541 0.566 0.527 0.564 0.0205 NS
in the total tract 0.939 0.926 0.927 0.931 0.0045 NS

For silage additives, see text.
/ Incubated in the rumen for 30 h.
§ To prepare the rumen undegraded feed residue rumen incubation period of30 h was used,

t Effective protein degradability calculated with k=0.033.
I EPD corrected for microbial contamination as suggested by Lindberg (1988).
a,b Means in the same row with different superscripts were significantly different (P<0.05).
NS, not significant; *, P<0.05; ***, P<o.ool,

169

Agric. Sei. Finl. 1 (1992)



Rumen fermentation and liquid dilution rate

The average rumen pH was not affected by the
silage additive (Table 6). The concentration of
ammonia-N in the rumen was significantly
(P<0.05) higherfor LFA and NA diets as compared
to the other diets.

The concentration of total VFA was not affected
by the silage additive, but the molar proportion of
acetate was significantly (P<0.001) higher and that
of propionate lower with FA and LFA than with E
and NA silages (Table 6). The proportion of buty-

Table 6. The effect ofsilage additive on rumen fermentation.

rate was significantly higherwith E treatment com-
pared to the others. Statistically significant differ-
ences between the curve patterns were not found
for any of the fermentationparameters measured.

The liquid dilution rate tended to be higher with
FA and LFA silages compared to NA and E silages
(Table 7). The estimate of rumen volume was
smallest with E silage and largest with NA silage.
The liquid outflowrate from the rumen was slowest
with E silage, the value being significantly
(P<0.05) different from those with LFA and NA
silages.

Statistical
Silage additive... NA FA LFA E SEM significance

of additive

pH 6.75 6.73 6.80 6.73 0.065 NS
Ammonia N (mmol/1) 8.88 b 8.86 b 10.51 a 10.17 a 0.969 ***

Total VFA (mmol/1) 96.9 b 100.3 97.4 100.0 3.76 NS

Molar proportion of
VFAs (mmol/mol)
Acetic acid 655 b 695 a 690 a 649 b 7.5 ***

Propionic acid 221 a 169 d 181 c 206 b 7.9 ***

Butyric acid 96 c 107 b 96 c 112 a 3.3 ***

Isovaleric acid 18.1 b 18.8 cb 22.2 a 20.6 ab 1.87 ***

Valeric acid 10.8 b 10.8 11.9 11.5 1.24 NS
Ratio (Ac+Bu)/Pr 3.5 d 4.8 a 4.4 b 3.8 c 0.19 ***

Ratio Pr/Bu 2.4 a 1.6 c 1.9 b 1.9 b 0.12 ***

For silage additives, see text.
Ac, acetic acid; Pr, propionc acid; Bu, butyric acid.
a,b,c,d Means in the same row with different superscripts were significantly different (P<0.05).
NS, not significant; ***, P<o.ool.

Table 7. The effect ofsilage additive on rumen outflow rate (D), rumen volume and liquid outflow in cattle.

Statistical
Silage additive... NA FA LFA E SIM significance

ofadditive
Liquid D(l/h) 0.075 0.092 0.091 0.082 0.0054 NS
Rumen volume (1) 54.6 46.6 46.9 40.1 3.83 NS
Liquid outflow (1/d) 95.6 b 91.8 ab 98.7 b 75.3 a 3.91 *

For silage additives, see text.
a,b Means in the same row with different supercripts were significantly different (P<0.05).
NS, not significant; *, P<0.05.

170

Agric. Sei. Fin!. 1 (1992)



Discussion

Silage quality

In accordance with previous results (Henderson et
al. 1982,Kennedy 1990,Heikkilä et al. 1989, Van
Vuuren et al. 1989, Jaakkola 1990, Jaakkola et
al. 1990, Jacobs and McAllan 1991, Heikkilä et
al. 1991), the cell wall content of E silage found to
be clearly reduced compared to others indicating
the activity of enzymes to hydrolyze cell walls to
WSC.

Dry matter content was highest in FA silage re-
flecting higher effluent losses compared to those
from other silages (4.1 vs. average 1.7 % DM, see
Toivonen 1989). The E and NA silages were
notably more fermented than the LFA and es-
pecially FA silages preserved with acid-based addi-
tives. Similar differences between silages have
been found in previous comparative studies (Kau-
ramaa et al. 1987, Jaakkola et al. 1991, Jacobs
and McAllan 1991). In accordance with Kaura-
maa et al. (1987), only minor differences in fer-
mentation patterns were found between E and NA
silage. However, the use of enzymes in silage
making especially under poor weather conditions
has resulted in more favourable fermentation than
in ensiling without additives (Jaakkola 1990,
Jaakkola et al. 1991). Obviously the use of pilot
silos in making the experimental silages resulted in
good-quality fermentation in NA silage, too.

Digestion of organic matter and fibre

The proportion of digestible OM apparently digest-
ed before the intestine was rather low (average
0.52) and the total N entering the duodenum was
rather high (Tables 3 and 4). These values may be
affected by duodenal digestive juices, since the
duodenal cannulas were checked at slaughter and
found to be located posterior to the pancreatic duct.
However, the disappearance of digestible fibre
before the small intestine indicated no overestima-
tion (Table 3). Hence, the possible contamination
should have no influence on the comparison of the

treatments.
Jaakkola et al. (1991) could find no marked

improvements in the digestibility of grass silage
OM through the use of cell wall degrading en-
zymes. However, in the present study, in agreement
with the experiment of Jacobs et al. (1991) with
growing steers, the OM digestibility ofE silage was
significantly higher than that of untreated or acid
treated silages (Table 3). In accordance with the
results of Jaakkola et al. (1991), the digestibility
of cell walls also tended to be higher for the E
silage diet as compared to the others. Several previ-
ous reports have pointed out that enzyme treatment
impaired rather than improved the fibre digestibi-
lity of grass silage with sheep (Heikkilä et al.
1989, Toivonen 1989, Jaakkola 1990, Heikkilä
et al. 1991), and also with growing cattle (Jaak-
kola and Huhtanen 1990, Jaakkola et al. 1990).

It has been suggested that the higher digestibility
of cellulose in E silage compared to FA and NA
silages with cattle is a consequense of a longer
rumen residence time (RRT) (Jaakkola et al.
1991). A longer rumen retention time has been
observed for cattle given forage diets thanfor sheep
(Rees and Little 1980), especially at low levels of
feeding (Colucci et al. 1984).

The RRT of the silages was not measured in the
present experiment, but as the proportion ofdigest-
ible OM and NDF digested in the rumen was high-
est with E silage, the higher digestibility of E silage
may be related to possible differences in RRT
between the silages. The contradiction in results
between the experiments may be related at least
partly to the different feeding levels. In the present
experiment, the cattle were fed near maintenance
level in contrast to experiments performed with
growing cattle, or with another species, sheep.

Digestion of nitrogen

The NAN flow entering the duodenum was signifi-
cantly lower with the E diet than the other diets
(Table 4), mainly due to the significantly lower
feed N flow. The flow of microbial N was clearly
highest for the LFA diet. In the study of Jacobs and

171

Agric. Sei. Fin!. 1 (1992)



MeAllan (1991), the flow of nitrogenous com-
pounds was similar for untreated, FA and enzyme
silages. On the other hand, Jaakkola et al. (1991)
found that the quantity of microbial N entering the
duodenum was significantly higher with FA silage
than with E silage. The contradiction between the
experiments may be due to the different application
rate of formic acid used, resulting in differences in
the extent of fermentation. When feeding restrict-
ively fermented silages, more fermentable carbo-
hydrates are available for rumen microbes than
from extensively fermented silages (Chamberlain
1987). This is possibly one reason for the higher
microbial N obtained with the LFA diet in the pre-
sent experiment. The advantage of restricted fer-
mentation of FA silage in the present experiment
was probably lost because of considerable effluent
losses in the silo (Toivonen 1989) due to the re-
duced moisture-holding capacity of FA silage
(Woolford 1978).

Supplementation ofgrass silage with concentrate
has generally increased the efficiency of microbial
protein synthesis in the rumen (ARC 1984). The
present average efficiency of 30 g microbial
N/organic matter apparently digested in the rumen
(OMARD) is consistent with the value given for
similar feeding by ARC (1984). The lowest effi-
ciency, which was obtained for the E diet (Table 3),
contrasts with the results of Jacobs and McAllan
(1989, 1991), who reported higher efficiency for E
feeding compared with FA feeding, especially
when the E diet was supplemented with rapeseed
meal. Jacobs and McAllan (1989) concluded that
enzyme treatment of the grass during ensiling had a
marked effect on the availibility or utilizability of
structural carbohydrates. Nevertheless, the present
results rather support the suggestion by Jaakkola
et al. (1991) that not even a high-quality supple-
ment compensates for the difference in silage qual-
ity caused by lactic acid fermentation.

Degradability of silages in the rumen and the
intestine

Compared with the acid-based additives, the E

additive tended to increase the instantly degradable
fraction a of OM and N of E with no effect on
potential degradation, but it decreased the potential
degradability of the cell walls. This finding was in
line with the earlier results of Huhtanen et al.
(1985) and Van Vuuren et al. (1989) indicating
that the breakdown of cell walls occurs in the silo
rather than in the rumen.

The EPD values and rate of degradation c of si-
lages preserved with acid additives tended to be
lower than those of other silages, in accordance
with theresults ofSetälä et al. (1985) and Vik-Mo
(1989) which indicate that the rate ofcrude protein
degradability was regulated mainly by the pro-
teolysis in the silage. Nevertheless, the EPD values
of grass silages were high and the correction for
microbial contamination still increased them
notably, in agreement with the results ofLindberg

(1988). This emphasizes the need to take the cor-
rection into account when calculating the EPD
values of forages. The degradability of silage-N in
vivo (Table 4) was notably lower than the re-
spective values obtained with the nylon bag met-
hod. As the in vivo value was calculated by differ-
ence, possible errors in the determination of micro-
bial or endogenous N will be accumulated in the
fraction of feed N. However, both methods ranked
the value for FA silage as lowest.

Intestinal OM, NDF and N degradability of
rumen-undegraded feed was rather low regardless
of the additive used, on an average 10.7 % for OM,
6.3 % for NDF and 55.0 % for N. In a previous
experiment (Varvikko and Vanhatalo 1988), the
respective value for grass silage N was also low, 57
% on an average, suggesting that the values used in
protein evaluation systems, e.g. 85 % by ARC
(1984), overestimate the intestinal degradability of
grass silage N.

Rumen fermentation and liquid dilution rate

Consistent with the results of Gordon (1989), but
not with those of Jaakkola et al. (1991), the molar
proportion of acetate in the rumen fluid was found
to be significantly higher with acid-treated silages

172

Agric. Sei. Fin!. 1 (1992)



than with E or NA silages. In accordance with pre-
vious reports (Gordon 1989, Jaakkola et al.
1991), the molar proportion of propionate in the
rumen fluid was significantly higher in E and NA
feeding, i. e., in silages with a high content of lactic
acid, than in FA and LEA feedings. Actually, the
propionate increased along with the increasing
lactate content in the silage, indicating the conver-
sion of silage lactate to propionate in the rumen
(Chamberlain et al. 1983, Newbold et al. 1987,
Jaakkola and Huhtanen 1989). Contrary to the
results of Gordon (1989) and Jaakkola et al.
(1991), the proportion ofbutyric acid for diet E was
higher than for diet FA. When compared with un-
treated silage, a small increase in the proportion of
butyric acid was found with E silage (Van Vuuren
et al. 1991). However, the changes in rumen VFAs
found in the present experiment were commensur-
ate to the reduction in milk fat content withE silage
feeding compared to FA silage feeding in dairy
cows (Heikkilä et al. 1989, 1991).

Again in contrast to previous results (Jaakkola
et al. 1991, Jacobs and McAllan 1991), the liquid
dilutionrate, rumen volume and liquid outflow rate
from the rumen were different for the E diet com-
pared to the other diets in the present study. How-
ever, also in the experiment by Jacobs and McAl-
lan (1991), the estimated rumen volume tended to

be smaller for the E diet compared to the FA and
NA diets. The liquid dilution rate did not seem to
be associated with microbial protein synthesis
either in this study or in the study by Jaakkola et
al. (1991), even though the differences between the
diets in synthesized microbial protein were quite
clear in both of experiments.

In conclusion, acid-based additives resulted in
more restricted fermentation during ensiling than
did enzymes or the absence of additive. The
improved OM and cell wall digestibility in vivo of
the E diet as compared to the other diets were obvi-
ously a consequence of the low feeding level in the
present experiment. The highest efficiency of
microbial protein synthesis in the rumen obtained
for LFA feeding was attributed to the small effluent
losses and the restricted fermentation of silage in
the silo. Regardless of the additive used, the EPD
values of the silages were high, especially when
corrected for microbial contamination, and the
values for intestinal degradation of rumen-
undegraded N were low compared to the values
used in protein evaluation systems.

Acknowledgements. The financial contribution by the Fin-
nish feed industry towards carrying out this experiment is
gratefully acknowledged. The authors are also indebted to
Ms. Aino Matilainen for her technical assistance in the
study.

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Manuscript received December 1991

Aila Vanhatalo
Tuomo Varvikko
Ilmo Aronen
Agricultural Research Centre of Finland
Institute of Animal Production
SF-31600 Jokioinen,Finland

SELOSTUS

Eri säilöntäaineidenvaikutus säilörehun laatuun sekä säilörehudieetin sulavuuteen,
mikrobisynteesiin ja pötsifermentaatioon naudalla

Aila Vanhatalo, Tuomo Varvikko ja IlmoAronen
Maatalouden tutkimuskeskus

Tutkimuksessa verrattiin eri säilöntäaineilla valmistettujen
säilörehujen vaikutusta naudan pötsifermentaatioon, ravin-
toaineiden virtaukseen ohutsuoleen ja mikrobisynteesiin.
Säilörehut tehtiin koiranheinä-timotei-nurmen toisesta
sadosta seuraavilla säilöntäaineilla: ilman säilöntäainetta
(NA), muurahaishappo (FA), lignosulfonaattien, muurahais-
ja etikkahapon seos (LFA) ja sellulaasia ja glukoosioksidaa-
sia sisältävä entsyymiseos (E). Koe-eläiminä oli neljä ylläpi-
totasolla ruokittua pötsi- ja ohutsuolifistelöityä hiehoa (elo-
paino 550 kg). Koe jäljestettiin 4x4 latinalaisen neliön
mukaan ja koeruokintoihin sisältyi tutkittavan säilörehun
lisäksi väkirehua (ohra-kaura 1:1) 30 % dieetin kuiva-
aineesta.

Kaikki säilörehut olivat hyvälaatuisia, mutta hapoilla säi-
lötyt rehut olivat vähemmän käyneitä kuin entsyymi- japai-

norehu. Entsyymirehun kuitupitoisuus oli alempi kuin mui-
den rehujen. E dieetin orgaanisen aineen jakuidun näennäi-
set sulavuudet olivat merkitsevästi korkeampia (P<0.05)
kuin muiden dieettien. Mikrobivalkuaisen virtaus ohut-
suoleen oli merkitsevästi korkeampi (P<0.001) LFA diee-
tillä (NA 52; FA 53; LFA 66 jaE 47 g N/d) ja mikrobisyn-
teesin tehokkuus alempi E dieetillä muihin verrattuna (NA
31; FA 31; LFA 38jaE20gN / pötsissä näennäisesti sula-
nut orgaaninen aine). Etikkahapon osuus pötsin haihtuvista
rasvahapoista oli FA ja LFA dieeteillä merkitsevästi kor-
keampi (P<0.001) ja propionihapon osuus merkitsevästi
alempi (P<0.001) kuin E ja NA dieeteillä. Voihapon osuus
oli E dieetillä merkitsevästi (P<0.001) muita korkeampi.

175

Agric. Sei. Finl. 1 (1992)