COMPARISON OF AMMONIUM, POTASSIUM, SODIUM, CHLORIDE
AND HYDROXYL IONS ON IN VITRO DRY MATTER
DISAPPEARANCE OF MILO STALKS 1
Garry L. Bales, D. Wayne Kellogg and D. D. Miller
N e w Mexico State University 2, Las Cruces 88003
Summary
Effects and some interactions of cations and
anions on in vitro dry matter disappearance
(IVDMD) of milo stalks were studied in five
experiments. From 1 to 5% (of dry matter) of
either sodium hydroxide (NaOH) or potassium
hydroxide (KOH) were added as pretreatment
to milo stalks. Although both NaOH and KOH
treatments increased IVDMD over the control,
NaOH increased IVDMD more than KOH,
especially at higher treatment levels. In Exp. II
ammonium chloride (NH4C1), ammonium hydroxide (NHaOH), potassium chloride (KC1),
KOH, sodium chloride (NaC1) and NaOH were
used in three levels each (on a molar basis) as
pretreatment of milo stalks. All hydroxide
treatments improved IVDMD, but NaOH and
KOH were superior to NH4 OH as pretreatments
of milo stalks with 56.2, 55.0 and 46.4%
IVDMD, respectively. Hydroxide compounds
increased IVDMD, but chloride compounds
reduced IVDMD slightly with increasing increments of the chloride ion. In Exp. III, NaC1
replaced sodium bicarbonate (NaHCOa) as part
of artificial rumen fluid (ARF), and IVDMD of
milo stalks declined from 48 to 46% when
chloride concentration reached 100 milliequivalents. Above 100 meq of chloride ion, IVDMD
declined more rapidly to less than 30% with
165 meq chloride in ARF. Stalks were pretreated
with 10 levels of NH4OH varying from 0 to
4.5% of dry matter in Exp. IV. Addition of less
than 2% of NH 4 OH resulted in higher IVDMD
(43 to 49%), but IVDMD did not increase much
above 50% when more NH4OH was added. In a
final experiment, NaOH was replaced (on a
molar basis) in increments of 10% by NH4OH
as a pretreatment for milo stalks. The IVDMD
percentage declined linearly from 52.3 to
43.4% as NH4OH constituted a greater proportion of chemical treatment. Pretreatment with
hydroxyl ion elevated IVDMD of low quality
forage, but interactions with cations, dissociation constants of the specific chemicals and
levels of chemical affected extent of improvement.
(Key Words: Milo Stalks, Alkali Treatment, Chloride Treatment, In Vitro Dry Matter
Disappearance.)
Introduction
Ruminants would obtain more energy from
forages if the rate and extent of digestion could
be increased (Mertens, 1977). This would
allow more extensive use of forages and increase
production of ruminants fed diets high in
forages. Apparently, the number of cellulolytic
microorganisms in the rumen influences rate of
digestion of specific substrates (Hungate, 1966;
Mertens, 1977). Changes in ionic concentration
of ratios of ions could affect microorganisms
and alter digestion of forages (Ward, 1966).
Chemical treatment of forages and roughages
has been used to improve digestion of low
quality forages by ruminants (Waldo, 1977).
Sodium hydroxide (NaOkl) treatment dramatically increased digestibility of roughages
(Klopfenstein et al., 1972; Ololade et al., 1970.
Waldo, 1977; Wilson and Pigden, 1964). Sodium
hydroxide has been compared to other alkali
treatments in some instances, but effects of
individual ions apparently have not been
isolated (Anderson and Ralston, 1972; Mathews
and McManus, 1976; Rounds et al., 1976;
a Submitted as Journal Article 667, New Mexico Spencer and Amos, 1977).
Agr. Exp. Sta., New Mexico State Univ., Las Cruces.
The experiments reported herein were
The authors express appreciation to M. L. Galyean
designed to determine effects and some interacand H. E. Kiesling for reviewing the manuscript.
2Dept. of Animal and R~nge Sciences.
tions of ammonium, potassium, sodium,
1324
JOURNAL OF ANIMAL SCIENCE, Vol. 49, No. 5, 1979
CATIONS AND ANIONS ON MILO STALK DIGESTION
chloride and hydroxyl ions on in vitro dry
matter disappearance (IVDMD) of milo stalks.
Experimental Procedure
Experiment I. Air-dried milo stalks (sorghum,
grain variety, aerial pt wo heads, s-c 1-07o961)
were ground in a Wiley mill with a 40-mesh
screen. Composition of stalks is shown in table
1. Either NaOH or potassium hydroxide (KOH)
was prepared in varied concentrations and 1 ml
was added to .5 g of milo stalks. Concentrations
varied to produce 1, 2, 3, 4 and 5% KOH or
NaOH on a dry matter basis. Stalks were
treated with respective chemical solutions,
mixed and stored for 24 hr at room temperature
in 50-ml covered tubes. Each chemical treatment
and both substrate and inoculum controls were
triplicated. After storage 1 ml of a 1% ammonium hydroxide (NHaOH) solution was added
as a source of a m m o n i u m ion for use by microorganisms. Also, 38 ml of artificial rumen fluid
(ARF) were added to each tube (Bales et al.,
1976). Table 2 gives the composition of ARF.
Treated forages were not neutralized or washed
before IVDMD determination. After 1 hr of
incubation at 38 C, 1 ml of strained rumen
fluid obtained from a permanently fistulated
Hereford steer that received pelleted milo stalks
and long alfalfa hay was added to each tube
according to a revision (Bales et al., 1976) of
the first digestion stage in the procedure
outlined by Tilley and Terry (1963). The pH
was checked four times during the 48-hr
incubation and was adjusted to 6.75 with acetic
acid or sodium bicarbonate. Data were analyzed
by analysis of variance and means were separated
by Duncan's new multiple range test.
Compounds were measured by weight in
experiment I to compare with published
TABLE 1. PROXIMATE ANALYSIS AND
CONTENT OF SELECTED MINERALS
IN MILO STALKS ON A DRY BASIS
Component
%
Crude protein
Crude fiber
Ether extract
Ash
Calcium
Magnesium
Phosphorus
Potassium
Nitrogen-free extract
2.5
33.3
2.7
14.3
.3
.2
.1
2.4
47.2
1 325
TABLE 2. COMPOSITIONOF ARTIFICIAL
RUMEN FLUID (BALES ETAL., 1976)a,b
Component
Grams
per liter
Sodium bicarbonate, NaHCO3
Sodium chloride, NaC1
Potassium chloride, KCI
Calcium chloride, CaCI2 92ft 20
Magnesium sulfate, MgSO4 97H20
Cobalt chloride, CoCI 96ft 2O
Casein hydrolysate
Cysteine
Biotin
Para amino benzoic acid
lsobutyric acid
Valeric acid
Acetic acidC
Phosphoric acidd
10.41
3.27
.746
.183
.492
.0015
1.0
.5
.00005
.0001
.058
.113
2.86
1.88
aThe pH of the solution was adjusted to 6.6 with
acetic acid.
bvitamins and cobalt chloride were prepared in
1000 • stock solutions and added last.
CAdded as 3 ml of glacial acetic acid.
dAdded as 1.3 ml of 85% phosphoric acid.
research. In subsequent experiments, compounds were compared on the basis of molar
equivalence.
Experiment IL Three levels each of three
cations (ammonium, potassium and sodium
ions) and two anions (chloride and hydroxyl
ions) were used in a 3 • 3 • 2 factorial arrangement. A m m o n i u m chloride (NH4C1), potassium
chloride (KC1), KOH, sodium chloride (NaCI)
and NaOH were prepared in stock solutions of
.3566, .7133 or 1.0699 M concentrations. One
milliliter of stock solution or of fresh solution
of NH4OH in the above concentrations was
added to .5 g milo stalks. A m m o n i u m compounds provided 1, 2 or 3% nitrogen. Stalks
were stored 3 days following chemical treatment.
Then incubation with 39 ml ARF and rumen
fluid was initiated. Other procedures were
similar to those outlined for Exp. I. Exp. II was
repeated with storage following chemical
treatment of both 3- and 5-day durations.
Experiment III. Effect of chloride ion on
IVDMD was studied by increasing its concentration in ARF. Milo stalks were incubated using
the procedure outlined in Exp. I without
preliminary chemical treatment. Chloride concentration was raised in 7 meq increments from
10 to 164 meq by substituting NaC1 for sodium
1326
BALES ET AL.
bicarbonate (NaHCO3). Thus, constant sodium
ion concentration was maintained. The base of
10 meq of chloride was contributed to A R F by
KC1. Initial pH was maintained between 6.6 and
6.8 by addition of acetic acid. As chloride ion
concentration increased, pH decreased to 5.8 at
the highest chloride concentration tested. The
pH was not adjusted in this experiment to avoid
changing sodium, potassium and ammonium
concentrations. Three tubes were used for each
level of chloride with three additional tubes
(total of six) between 80 and 101 meq of
chloride. Response curves were estimated by
regression analysis.
Experiment IV. Ten levels of NH4OH were
used to determine effect of levels of NHaOH on
IVDMD of milo stalks. Stock solutions of
NH4OH were prepared to provide (on a dry
matter basis) concentrations as high as 4.5%
(1.284 M) NHaOH in .5% increments. One
milliliter of stock solution of NHaOH was
added to each of three tubes containing .5 g
milo stalks. Tubes were stored 48 hr at room
temperature prior to incubation with A R F and
rumen fluid. Regression analysis with lack of fit
test was used to determine linearity of response.
Experiment V. The final experiment evaluated NH4OH as a replacement for NaOH. Milo
stalks (.5 g) were treated with 1 ml o f NaOH
(1.0692 M) or a mixture of NaOH and NHaOH.
Mixtures varied from 10 to 90% NHaOH in
10% increments, thus 1.0692 M concentration
of the hydroxides was maintained. Treated
forages were stored for 3 days with nine tubes
per treatment prior to addition of modified
ARF. In this experiment, A R F contained 20%
less NaHCO3 and NaC1 than table 2 indicates to
maintain equal concentrations o f sodium ions
in the incubating solution. Inoculation with 1
ml strained rumen fluid occurred as before.
Analysis of variance with orthoginal polynomials
was employed to test for linearity of response.
Regression analysis was used to estimate the
response curve.
R esu Its
Experiment
I.
An interaction occurred
(P<.01) between chemical treatments and levels
of chemical (table 3). Sodium hydroxide
increased (P<.005) IVDMD of milo stalks more
than KOH and the difference was greater as
level o f treatment increased. Values of IVDMD
for milo stalks treated with 5% NaOH averaged
61.4% compared to 55.0% for stalks treated
with 5% KOH. Percentage IVDMD increased
(P<.005) with additions of both chemicals and
3% NaOH and 4% KOH were required to
increase (P<,01) IVDMD above the control (no
chemical treatment) value of 47.5%. This
experiment compared the chemical on a weight
basis and provided more moles of hydroyl ions
with NaOH than KOH at each level. The
IVDMD of milo stalks was similar for KOH and
NaOH treatment on a molar basis.
Experiment 11. In addition to differences
(P<.005) among cation, anions and levels of
chemical treatments, there were significant twoand three-way interactions. The IVDMD values
varied (P<.005) among chemical treatments
depending upon combination of cations and
anions and levels added to milo stalks. The
IVDMD percentage was similar with all chloride
treatments, but NaOH and KOH treatments
resulted in higher (P<.01) IVDMD values than
NH4OH (table 4). There was no effect of level
on IVDMD due to treatment with ammonium
compounds. Increasing levels of compounds
containing potassium and sodium increased
(P<.01) IVDMD values with each level of
increase. Increasing chloride levels reduced
(P<.05) IVDMD from the control value of
41.9% to 40.0%, while treatment with hydroxide
compounds increased (P<.01) IVDMD of milo
stalks. Elevation of IVDMD by KOH and NaOH
was greater (P<.01) at high levels of the hydroxides than with NHaOH. The decline (P<.05) of
IVDMD was similar for each chloride compound.
Potassium and sodium compounds were
more effective than ammonium compounds in
increasing (P<.005) IVDMD of treated milo
stalks. Hydroxides were more effective (P
<.005) than chlorides in increasing IVDMD of
treated milo stalks. Overall means of 1VDMD
values increased (P<.005) as levels of chemical
were increased. However, specific interactions
mentioned above should be considered when
these main effects are interpreted.
Storage of chemically-treated forage for 5
days rather than 3 days did not change IVDMD
percentages except that IVDMD values of
forage treated with NHaOH increased from
46.5 to 47.9%. However, IVDMD values for
NH4OH were still below those for KOH and
NaOH.
Experiment IlL As NaC1 replaced NaHCO3,
IVDMD declined slightly until chloride concentration reached 100 meq (figure 1). This
response was fitted by the equation: Y = 48.0
- .018 X (R 2 = .20, SE = .9), where Y =
IVDMD percentage and X =. chloride concentra-
CATIONS AND ANIONS ON MILO STALK DIGESTION
1327
TABLE 3. EFFECT OF INCUBATING GROUND MILO STALKS WITH 1 TO 5% SODIUM
OR POTASSIUM HYDROXIDE ON IN VITRO DRY MATTER DISAPPEARANCEa
Level of chemical, % of dry matter
Chemical
0
NaOH
1
2
3
4
5
Means
SE
48.1g hi
50.1fg
54.2 de
56.7 c
61.4 b
54.1
1.3
46.0i
47.0
.7
46.7 i
48.4
.8
49.2fg h
51.7
1.1
51.5 ef
54.1
1.2
55.0 cd
58.2
1.5
49.7
51.9
.9
(47.5g hi)
KOH
Means
SE
47.5
.4
avalues are means of three tubes.
b'e'd'e'f'g'h'ivalues followed by different letters differ significantly (P<.O1).
t i o n in milliequivalents. When chMride c o n c e n t r a t i o n e x c e e d e d 100 m e q , t h e r e s p o n s e curve
was m u c h steeper. The e q u a t i o n , Y = 72.7 .266 X (R 2 = .90, SE = 1.9), r e p r e s e n t e d t h e
l a t t e r phase o f t h e r e s p o n s e curve. The t w o
curves i n t e r c e p t e d at 100 m e q o f chloride. T h e
entire r e s o o n s e curve was f i t t e d b v t h e e q u a t i o n ,
= 43.1"+ .183X - . 0 0 1 6 7 X 2 ('R2 = .96, SE =
1.2). This n o n l i n e a r e q u a t i o n e s t i m a t e d t h e
TABLE 4. EFFECT OF INCUBATING GROUND
MILO STALKS WITH THREE LEVELS
(MOLAR BASIS) OF SELECTED CHEMICAL
COMPOUNDS ON IN VITRO DRY
MATTER DISAPPEARANCEa,b
Level of
chemical treatment c
Ion
1
2
3
Means
SE
(%)
ClNH 4 +
OH
C1K+
OHC1Na +
OHMeans
SE
41.0J k
40.6J k
39.7 k
40.4
.4
45.0 i
41.2J k
47.2 hi
40.2J k
47.0 hi
39.4 k
46.4
40.3
.3
.3
49.0g h
42.2J
55.3 f 60.6 d
41.4J k 41.0J k
55.0
41.5
1.2
.4
49.2g
44.6
.6
57.6 e
47.0
1.2
56.2
46.6
.7
1.3
61.8 d
48.3
1.6
avalues are means of six tubes.
bcontrol (no chemical) tubes averaged 41.9%
IVDMD.
m a x i m u m I V D M D value w i t h chloride c o n c e n t r a t i o n o f 55 m e q .
Experiment IV, L o w e r levels o f N H 4 O H
elevated ( P < . 0 1 ) IVDMD p e r c e n t a g e , b u t t h e
i m p r o v e m e n t in I V D M D did n o t c o n t i n u e
p r o p o r t i o n a l l y as t r e a t m e n t levels o f N H 4 O H
were increased (figure 2). The IVDMD o f milo
stalks r e a c h e d a m a x i m u m at 50.5% IVDMD
c o r r e s p o n d i n g t o a t r e a t m e n t level o f 2.5%
NH4OH. When m o r e t h a n 2% N H 4 O H was
used, a d i s t i n c t a m m o n i a o d o r was d e t e c t e d in
t h e t r e a t e d forage.
Experiment V. The I V D M D p e r c e n t a g e
increased linearly ( P < . 0 0 5 ) f r o m 43.4 t o 52.3%
as NaOH c o n s t i t u t e d a greater p r o p o r t i o n (10
t o 100%) o f t h e chemical t r e a t m e n t on a m o l a r
basis (figure 3). This r e s p o n s e curve was f i t t e d
b y t h e e q u a t i o n , Y = 41.8 + 10.6 X (R 2 = .86,
SE = 1.3), w h e r e Y = IVDMD p e r c e n t a g e and X
= m o l e s NaOH. A m m o n i u m h y d r o x i d e did n o t
a d e q u a t e l y replace NaOH w h e n t r e a t e d stalks
w e r e s t o r e d for 3 days.
~
o
=S4~"
J
o
~o
90
ao
oo
30
?o
*o
5o
NaOH, %
60 ~o
so
40
?o
30
80
2o
oo
~o
Joo
o
NH4OH,%
CLevels were .3566, .7133 or 1.0699 M concentrations of the six compounds.
d'e'f'g'h'i'j'kvalues followed by different letters
differ significantly (P<.O1).
Figure 1. Effect of increasing chloride ion concentration by replacing NaHCO 3 with NaCI in artificial
rumen fluid on in vitro dry matter disappearance of
milo stalks.
1328
BALES ET AL.
60
45
55
40
~5c
#
/
g
~35
o45
\
3C
40
0
~0
45
60
75
90
105
I;~0
135
i50
165
CHLORIOE, =,~
Figure 2. Effect of increasing NH4 OH levels during
reconstitution and storage on in vitro dry matter
disappearance of milo stalks.
Discussion
Potential of chemical treatment to improve
forage has been recently reviewed (Waldo,
1977) with the conclusion that research,
particularly with NaOH, and technology are
available to improve digestibility and intake of
low quality forages by treatment with alkali.
However, NaOH could potentially add to
salinity problems and treated products often
contain little nitrogen (Ololade and Mowat,
1975; Waldo, 1977). Use of other chemical
compounds could avoid these disadvantages.
Potential difficulty with sodium toxicity to
the animal and ultimately to soil could be
avoided b y using different cations. In Exp. I,
treatment with KOH increased IVDMD of
stalks over the control, but a higher concentration (on a dry matter basis) was required than
for NaOH. Similar results were observed with
treated Coastal bermuda-grass (Spencer and
Amos, 1977). Anderson and Ralston (1973)
and Rounds et al. (1976) found that NaOH and
KOH had similar effects on rye-grass straw and
corn cobs. Results were quite different when
ground lucerne was treated with a dry process
involving pelleting because KOH was as effective
as NaOH (Mathews and McManus, 1976).
Legumes have proportionately less cell wall
constituents than grasses. Forages apparently
vary in their reaction to chemical treatment and
the level of chemical employed also affects the
response. In spite of its potential disadvantages,
NaOH appears superior to KOH in some circumstances and has found greater use as a forage
treatment.
Problems associated with feeding forages
high in potassium to ruminants have not been
encountered. Consumption of potassium usually
5
I0
1.5
2.0
25
30
35
40
4.5
NH40H,%
Figure 3. Effect of replacing sodium hydroxide
(1.0692 M) with increments of ammonium hydroxide
on a molar basis during reconstitution and storage on
in vitro dry matter disapperance of milo stalks.
exceeds requirements of about .5% of the diet
(Ward, 1966), but cattle grazing native winter
ranges have needed supplemental potassium
(Karn and Clanton, 1977). Although large oral
doses (238 to 648 g) were fatal when administered rapidly, cows regularly consume up to
500 g of potassium daily in pasture or soilage
(Ward, 1966). Sodium toxicity to ruminants
can occur, but if water is available high intakes
of sodium as NaCI have not proved hazardous
(Moseley and Jones, 1974; Nelson et al., 1955).
Forages treated with 4% NaOH have been fed
successfully (Klopfenstein, 1975 ; Rounds et al.,
1976).
Ammonium hydroxide would supply nitrogen, but the cation associated with the hydroxide was important in this study because NH4 OH
increased IVDMD less than KOH or NaOH
in Exp. II and V. The ranking of chemical
treatments was the same in an in vitro experiment with ryegrass straw (Anderson and
Ralston, 1973). Klopfenstein (1975) and
Rounds et aL (1976) found that 4% NaOH was
superior to 4% NH4OH for treating corn cobs
for lambs. In the latter experiments, excessive
ammonia interfered with consumption of
treated corn cobs unless mixed with other feeds
(Rounds et aL, 1976).
As the level of NH4OH was increased in
experiments II, IV and V, IVDMD of milo
stalks increased with lower levels of NH4OH,
but proportional increases in IVDMD did not
occur with higher levels of NHaOH. Similar
results have been observed with ryegrass straw
where 2% NH4 OH improved digestibility of dry
matter in vitro from 32.1% for control to
35.3%, but no further increase was observed
with higher levels of NHaOH (Anderson and
CATIONS AND ANIONS ON MILO STALK DIGESTION
Ralson, 1973). Concentrations up to 8% NaOH
and KOH increased IVDMD in the same experiment. Levels of N a O l l f r o m 0 to 8% have
generally p r o d u c e d linear increases in IVDMD
(Waldo, 1977).
A m m o n i u m h y d r o x i d e reacted m o r e slowly
(P<.01) than NaOH or KOH in Exp. II. This
effect had been reported previously (Tarkow
and Feist, 1969), and may be due to the m u c h
lower degree of ionization of NH4OH. If the
h y d r o x i d e ion were less available, the reaction
would have proceeded at a slower rate.
Though not used in these experiments,
calcium h y d r o x i d e has been used successfully in
c o m b i n a t i o n with NaOH to treat corn stover
and corn cobs (Oji et al., 1977; Rounds et al.,
1976; Waller and Klopfenstein, 1975).
These experiments emphasize the i m p o r t a n c e
of h y d r o x y l ion availability in improving
digestibility of low-quality forage. The extent
of influence of the h y d r o x y l ion was t e m p e r e d
by the cation associated with it. A m m o n i u m
chloride, KC1 or NaCI did not improve IVDMD.
In fact, chloride c o m p o u n d s tended to reduce
IVDMD in these experiments. A slight r e d u c t i o n
in I V D M D occurred as chloride c o n c e n t r a t i o n
increased to 100 meq, and above 100 m e q of
chloride the depression of IVDMD was m u c h
greater.
When steers received 240 g NaC1 daily by
gelatin capsule, digestion of crude fiber of
prairie grass hay (68.2%) was similar to that
(69.4%) obtained on the basal diet (Nelson et
al., 1955). In a similar e x p e r i m e n t with wethers,
daily intake of 42 g of NaCI reduced digestibility
of organic m a t t e r f r o m 69.2 to 66.8% through
effects on crude fiber and nitrogen-free extract
(Nelson et al., 1955). Moseley and Jones (1974)
found that organic m a t t e r digestibility of a diet
of grass hay fed ad l i b i t u m with a s u p p l e m e n t
of 200 g pelleted barley was 54.5, 53.7, 51.4
and 49.1% with sodium (from NaCI) contents
of .46, 1.66, 2.46 and 3.10%, respectively, of
the dietary dry matter. Although the highest
level of sodium reduced organic m a t t e r digestibility, dry m a t t e r digestibility was similar for
each of the diets (Moseley and Jones, 1974).
Cardon (1953) found no effect of .8 or .9 kg
o f NaCI on cellulose digestion by three cows
receiving 6.8 kg alfalfa daily. There was no
effect of NaCI in vitro either, but pH was not
constant and cellulose digestion was low
(Cardon, 1953). Up to 20% NaCI in feed or 2%
in water of sheep had no effect on dry m a t t e r
digestibility of lucerne or a straw and lucerne
1 329
m i x t u r e (Wilson, 1966). Changes in salivary
flow rate allowed sheep to partially adjust for
elevated saline intakes (Tomas and Potter,
1975). Physiological adjustments m a y reduce or
prevent detrimental effects of chloride measured
in vitro in these experiments.
In conclusion, chemical t r e a t m e n t o f milo
stalks with NaOll, KOH and N H 4 O H raised
I V D M D above control, NaCI, KCL and NII4CI
treatments. However, the e x t e n t o f improvem e n t due to hydroxides was governed by
interactions with cations, dissociation constants
of the specific chemical and the level o f chemical. Research is needed in vivo to apply these
results in practical solutions.
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