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THE POTENTIAL OF TREATMENT WITH ASH SOLUTION IN IMPROVING
DEGRADABILITY OF FIBROUS FEEDS IN ETHIOPIA
Solomon A. Kebede*1, Ulfina G. Girgo2, Gemeda D. Jalleta3
1 Institute of Biodiversity Conservation, P.O.Box 30726, Addis
Ababa Ethiopia tel. 251-91-1350212 Fax: 251- 11-6613722. Email:
2 Ambo College, Jimma University P.O.Box 19, Ambo, Ethiopia
Email:[email protected]
3 Bako Agricultural Research Centre P. O. Box 3, Bako, W. Shoa,
Ethiopia Email:[email protected]
ABSTRACT
Study on the evaluation of potential of ash as a source of alkaline solution to treat
fibrous feeds has been conducted at Bako Agricultural Research Centre, Ethiopia. In
the current study, determination of alkalinity strength of solution of ash from 12
different sources, evaluation of nylon-bag degradability of treated hay and growth
performance of lambs fed hay treated with 5% ash solution were investigated. Ash
from maize stover and from A. Abyssinica, G. lutea and M. lutea have shown the
highest alkalinity strength of 39.5, 36.5, 34.3 and 33.8 in terms of CaCO3 equivalent
while ash from cow dung was with the lowest strength of 5.7. Forty-eight hour nylon-
bag degradability of hay treated with ash from the four sources of the highest
*corresponding author
2
alkalinity strength (61.7 to 68.1) was higher than hay treated with plain water (48.0)
and untreated control (53.4). Chemical analysis has shown that treatment with ash
solution increased Neutral Detergent Fibre (NDF) and Acid Detergent Fibre (ADF). In
the absence of protein supplement, treatment with ash solution of composite source
has resulted in significantly (p<0.05) higher intake (646 g/h/d) than hay treated with
plain water (566 g/h/d). Lambs in all treatments have shown loss of weight though
those fed ash solution treated hay have shown less loss (0.13 vs 0.32kg). There was
no significant difference between treatments in water intake. Presence of variation in
alkalinity strength of ashes from different sources, improvement in degradability
and intake and less weight loss in lambs fed hay treated with ash solution have
indicated that ash solution has potential in improving degradability and feeding
value of fibrous feeds.
Key words: Alkaline solution, alkalinity strength, feed intake, growth performance,
lambs.
3
INTRODUCTION
In the smallholder mixed farming system the major feed
resources include crop residues and natural pasture. These
feeds are of high fibre content with low feeding value. This
is partly due to their inadequate protein content, but in
addition, the abundant energy stored in the cellulose and
hemicellulose content of their cell walls is not readily
available for digestibility by rumen micro organisms.
Improvement of the digestibility of fibrous feeds can result in
4
increase of feeding value. Increase in digestibility of such
fibrous feeds by 10-20% can have immense implication for animal
production by small (holder) farmers (Ørskov, 1988).
Various methods have been employed to improve feeding value of
fibrous feeds. One of these methods is chemical treatment and
have reportedly improved the utilization of fibrous feeds to
such an extent as to make their utilization as feed ingredients
feasible and profitable (Jackson, 1977). For chemical treatment
alkali chemicals are usually employed (Jackson, 1977; Chaudhry,
1998). However none of the proven chemicals such as sodium
hydroxide, calcium hydroxide, potassium hydroxide and ammonia
are suitable for smallholders because of the high cost and
scarcity of the chemicals and danger (caustic burn) associated
with their use.
On this premise a local chemical easily within the reach of
livestock farmers and which can effectively perform the
functions of imported ones, is needed. Under limited
investigations, solutions of ash from wood (Nolte et al., 1987;
Ramirez et al., 1991 and 1992; Laswai et al., 2007), animal dung
5
(Genin et al., 2002) and some crop residues (Adebowale, 1985;
Smith, 1989) appear a suitable alternative. Apart from
improving digestibility of fibrous feeds ash solution treatment
has also been reported to mitigate the effect of anti-quality
factors (e.g. tannin) (Ben Salem et al., 2005a and 2005b). Ash has
also been found to serve as a mineral supplement (Ndlovu,
2007; Phoso, 2009).
In areas where biomass (mainly firewood) is a common source of
fuel a large quantity of ash is available in almost every
household. The ash content and chemical composition are
variable among tree species and also depend on soil type and
climate Pitman (2006). Various woods provide ash in a quantity
ranging from 0.2 to 6.1% depending on the wood species
(Navarro, 1976) commonly 0.5-2.0% for tropical woods (temperate
woods have less ash) and the ash yield may vary with combustion
temperature (Etiégni et al., 1991). Apart from wood materials,
dried cow dung and crop residues are also used as fuel, thus
provide ash. The use of these resources as a potential source
of alkali for treatment of fibrous feeds was found worth
investigating.
6
The objectives of this study were:
1. Evaluation of the alkalinity strength of solutions prepared
from various sources of ash.
2. Evaluation of the potential use of the various ash solutions
in treating various fibrous feeds to improve degradability.
3. Evaluation of the feeding value of fibrous feeds treated with
wood ash on gain of lambs.
MATERIALS AND METHODS
Material
Twelve different ash types from various woods, crop residues
and cow dung were prepared for testing the alkalinity strength
of solutions formed from the ashes. These include wood from
trees locally called ‘Addajaboo’ (Markhamia lutea), ‘Gambeela’
(Gardenia lutea), ‘Laftoo’ (Acacia Abyssinica), ‘Dabaka’ (Deinbollo
Kilmandshorica), ‘Bekennisa’ (Croton macrostychus), ‘Hagamsa’ (Carissa
edulis), ‘Wedessa’ (Cordia Africana), ‘Luugoo’ (Ficus sycomorus) and
‘Tatessa’ (Rhus glutinosa), and sorghum and maize stover and cow
7
dung. Metallic barrels of 200 litre capacity were used to form
the ash solution and treat the fibrous feeds.
Methods
Alkalinity strength determination
Ash from the different sources was sieved with 1 mm mesh to
separate it from incompletely burned material and other
impurities. It was stored in airtight containers and sent to
International Livestock Research Institute (ILRI) laboratory in
Addis Ababa for determination of the alkalinity strength.
Alkalinity strength was determined as CaCO3 equivalent through
titration (Applied Membranes, 2007).
8
Potential value of wood ash solution in improving degradability
Ashes from the four sources which showed the highest
alkalinity strength were used to form a 5% (w/v) ash solution.
Poor quality (over-mature) hay of Rhodes grass was soaked for
six hours. In addition hay treated with plain water and
untreated hay were included to serve as controls. The nylon
bag technique was used and degradability at 0, 3, 6, 9, 12,
24, 48, 72 hours were observed in duplicate. The degradability
for each feed and hour was summarized and the average value
was fitted to the following equation of Ørskov and McDonald
(1979).
P=a+b(1-e-ct)
Where P is degradation at time (t), a , b and c are constants
and e is the natural logarithm. The equation was chosen
because it gives some biological meaning to the constants in
so far that a is the intercept or the immediately soluble
fraction, b is the insoluble but potentially degradable
material and c is the rate constant of b (Ørskov, 1986).
9
Animal performance study
32 growing ram lambs with average weight of 21.5 kg were
assigned to 4 feeding treatment groups in a 2 x 2 factorial
arrangement (treated or untreated hay, presence or absence of
supplementation).
Treatments
1. Rhodes (Chloris gayana) grass hay treated with water
2. Rhodes (Chloris gayana) grass hay treated with water +
Desmodium (Desmodium uncinatum) hay
3. Rhodes grass hay treated with wood ash solution
4. Rhodes grass hay treated with wood ash solution +
Desmodium (Desmodium uncinatum) hay
The ash used in this particular study was from a mixed source.
Composition of treated and untreated Rhodes grass (Chloris
gayana) hay was determined through chemical analysis. The grass
hay was chopped and treated (soaked) with 5% W/V ash solution
for six hours. Though other researchers (Nolte et al., 1987;
10
Ramirez et al., 1991) have reported ash solution of 20 to 30 per
cent, in the current study concentrations higher than 5% were
not possible because of excessive insoluble residue. The feed
material was in a perforated plastic bag to avoid wastage and
dripping of the excess liquid was done after soaking was
completed. Samples were taken for dry matter determination
before provision of the feed to the animals and from the
refused leftover once in a week throughout the experiment. One
kg of feed /head/day (as fed) was provided once at 10:30 am.
In addition to the hay, 175 gram per head per day of Desmodium
(Desmidium uncinatum) hay supplement was given to lambs in
treatment two and four. 200 gram /head/ day of concentrate was
offered as supplement to all groups at 9:30 am. Feeding has
taken place for a total of 120 days. Water intake was recorded
throughout the feeding period as the difference between the
amount offered and refused.
Weight recording was done in the first two days of the
experiment, once every fortnight afterwards and for two
consecutive days at the end of the experiment. Data on final
weight, weight gain and feed and water intake were subjected
11
to statistical analysis using SAS (1996) statistical package.
Where there is significant difference between treatments,
means were separated using LSD procedure.
RESULTS AND DISCUSSION
Alkalinity strength determination
The alkalinity strength of solutions from ashes of different
sources is shown in Table 1. Ash from maize stover was found
to have the highest alkalinity strength followed by ash from A.
Abyssinica, G. lutea and M. lutea in the respective order. Ash from
sorghum stover has also shown about half the strength of ash
from maize stover. Ash from dried cow dung has the lowest
alkalinity strength which is less than a fifth of the strength
of ashes from most sources.
This might be as a result of leaching of chemical components
that can contribute to the alkalinity strength as the dung
stays to dry out on the ground. Similar result of lower
content of alkali metals in dung ash as compared to ash from
12
other sources has been reported by Genin et al. (2002),
respectively.
Potential value of wood ash solution in improving
degradability
Over all, treatment of straw including with plain water has
resulted in degradability increment (Table 2). The immediately
soluble component in the feed was lowest in hay treated with
plain water while it was the highest in hay treated with A.
Abyssinica. The proportion of the insoluble but potential
degradable fraction was highest for water treated straw. Over
all degradability was the highest for hay treated with A.
Abyssinica wood ash solution and all ash solutions have resulted
in higher overall (a+b) potential degradability than hay
treated with plain water though the difference is not that
high. However, in addition to the total potential
degradability the amount of degradability in the first 48
hours was the lowest for the hay treated with plain water.
Rumen retention time of straw is reported to vary from 36 to
60
13
Table 1. Alkalinity strength of ashes based on CaCO3 (mg/l)
equivalent.
Source of Ash CaCO3 equivalent
(mg/l)
Wood from Addajaboo tree (Markhamia lutea), 33.8
Wood from Gambeela tree (Gardenia lutea) 34.3
Wood from Laftoo tree (Acacia Abyssinica) 36.5
Wood from Dabaka tree (Deinbollo
Kilmandshorica),
27.4
Wood from Bekkanisa (Croton macrostychus), 28.7
Wood from Hagamsaa tree (Carissa edulis) 31.0
Wood from Waddeessa tree (Cordia Africana) 26.1
Wood from Luugoo (Ficus sycomorus) 30.1
Wood from Tatessa (Rhus glutinosa) 24.5
Sorghum Stover 17.4
Maize Stover BH-660 39.5
Dried Cow dung 5.7
hours (Ørskov, 1986), therefore the potential degradability
which will be reached after this period has no nutritional
14
importance to the animal. This may show that the higher
degradability of hay treated with ash solution at 24 and 48
hours was an indication of the improvement that can be
realized by treatment with solution of ash. Variation in the
effect of ash from various sources (dung from two different
species) in improving digestibility has been reported by Genin
et al. (2007).
Table 2. Degradation of untreated and hay treated with ash
solutions and plain water.
Ash type Degradation at hours after
incubation
0 3 12 24 48 72
Addajaboo (Markhamia
lutea)
20.
2
20.
9
27.
8
47.
3
62.
3
64.4
Gambello (Gardenia lutea) 19.
0
22.
9
35.
7
49.
4
61.
7
70.1
Laftoo (Acacia Abyssinica) 26. 30. 36. 54. 68. 71.9
15
0 7 7 6 1
Maize Stover 24.
9
23.
6
34.
0
54.
5
66.
9
68.2
Treated with plain water 11.
7
14.
2
24.
5
34.
6
48.
0
58.0
Untreated 12.
0
21.
9
31.
8
41.
8
53.
4
62.0
Degradability constants from hay treated with ash solution of
various sources, plain water and untreated hay are presented
in Table 3. Rate of degradation (c) of the slowly degrading
fraction (b) was higher for hay treated with ash solution than
with plain water. Extent of potential degradation (a+b) is
also higher for hay treated with ash solution than untreated
or hay treated with plain water. In a similar vein values for
dry matter (DM) and organic matter (OM) digestibility of ash
treated rice straw (0.633 and 0.684) were found to be higher
(P<0.01) than those of urea treated (0.579 and 0.643) and
untreated (0.559 and 0.617) straws (Laswai et al., 2007). Lower
rate of degradability of water treated hay as compared to
untreated hay was observed. Similar observation was made on
maize cob by Tuah and Ørskov (1989). This could be related to
16
higher increase in Neutral Detergent Fibre (NDF) and Acid
Detergent Fibre (ADF) percentage in water treated hay than
untreated hay (Table 4).
Table 3. Degradability constants of untreated and hay treated
with ash solutions and plain water.
Hay type A b c a+b
Treated with ash from
Adajaboo
16.9 58.5 0.0265 78.4
Treated with ash from
Gambella
19.0 56.7 0.0310 75.7
Treated with ash from
Laaftoo
24.1 58.1 0.0266 82.2
Treated with ash from
Maize stover
20.0 56.8 0.0312 76.8
Treated with Plain water 11.5 61.5 0.0193 73.0
Untreated 15.1 50.1 0.0334 65.2
17
Chemical composition and animal performance study
Treatment of hay either with plain water or ash solution has
resulted in an increased per cent of NDF and ADF (Table 4).
The reason could be solubilisation and removal of highly
soluble components from the hay soaked in water and wood ash
solution. Similar increase in NDF percentage of acacia as a
result of wood ash treatment has been reported by Ben Salem et
al. (2005a). On the contrary reduction in NDF and ADF content
was reported as a result of lime treatment of rice straw
(Nguyen et al., 2001). Similarly ash content of hay soaked in
water was decreased as compared to that of the untreated hay
while ash content of hay treated with ash solution was
increased. This could also be the removal of some soluble
minerals by water treatment while ash solution treatment
increases mineral content of the hay over and above that could
be removed by solubilisation as a result of the high ash
content of the solution itself.
18
Table 4. Chemical composition of hay used in the experiment
untreated, treated with water or ash solution for 6 hrs.
Feed DM% Ash NDF ADF
Rhodes hay 94.0 7.96 80.4 49.0
Rhodes hay soaked in H2O
for 6 hrs.
93.7 6.14 84.2 53.0
Rhodes hay soaked in ash
solution for 6 hrs.
93.5 8.13 83.9 52.4
DM%= dry matter percentage of partially dried sample
Feed and water intake and initial and final weight of animals
is presented in Table 5. Treatment has no significant effect
on weight gain and water intake but there was significant
difference in feed intake. Animals given hay treated with wood
ash solution have the highest intake and the lowest weight
loss. Desmodium supplementation did not cause improvement in
hay dry matter intake either in the groups fed untreated or
treated hay. The lack of improvement in intake and gain due to
desmodium supplementation could be the result of low quality
of the hay (over-mature). Preston and Leng (1984) have
suggested that for forage supplementation to enhance the
19
utilisation of fibrous feeds (crop residues), the forage
should be of good quality and digested. Overall level of
intake observed in the study (above 2.4 per cent of body
weight) seems adequate to result at least maintenance of body
weight, but the animals have shown loss of weight. This might
have resulted from lower digestibility of the feed staffs
despite improved nylon bag degradability. Ash treated straw
may have a negative effect on rumen micro organisms when fed
as opposed to small quantity degraded in the nylon bag. The
other possibility would be overestimation of intake.
Procedures followed in the study were more accurate in
measurement of feed offered but less accurate in terms of
measuring the refusal (smaller particles could have been
missed during collection and measurement of the refusal).
There was no significant difference in water intake.
Table 5. Mean value, initial and final weight and weight gain
of feed and water intake of sheep in the four treatment.
Treatment No IWT FWT(kg AFI(g WG(kg (g/ AWI
20
. (kg) ) ) ) kg0.75/d)
Grass hay
treated with
water
6 20.5±0
.78
20.2±0
.81
566b -0.32 59.4b 331
Grass hay
treated with
water +
Desmodium hay
8 22.0±0
.68
21.7±0
.70
542b -0.28 53.3c 419
Grass hay
treated with
ash solution
8 21.7±0
.68
21.6±0
.70
646a -0.13 64.3a 328
Grass hay
treated with
ash solution
+ Desmodium
hay
7 21.9±0
.72
21.6±0
.75
528b -0.31 52.2c 338
NS NS ** NS ** NS
IWT=Initial Weight; FWT=Final weight; WG=Weight gain; AFI=Average Daily
Feed Intake (gm); AWI=Average Water Intake (ml) WG=Weight gain;
(g/kg0.75/d)=feed intake per unit metabolic weight per day; NS= Not
significant. Means followed by different superscript are significantly
different.
21
CONCLUSION
The alkalinity strength study indicated that difference exist
among the various ash sources and when use is to be made of ash
solution the one which would provide solution with higher
alkalinity strength should be selected. Degradability study
showed that there is sizeable improvement in rate of
degradation as a result of treatment with ash solution
resulting in improvement of amount degraded in the first 24 to
48 hours. This is important since digestion would take place
within the normal rumen retention time which is within 36 to 60
hours. The feeding study has shown significantly higher intake
and non-significantly lower weight loss in lambs fed hay
treated with wood ash solution than with plain water. The
findings in this study indicated potential of ash solution in
improving the feeding value of fibrous feed resources. To
optimize use of the ash solution further study is required to
evaluate the effect of treatment at different ash
22
concentrations. Treating large quantity of fibrous feed at
small farms level is difficult because of the lack of adequate
amount ash. Under this condition repeated use of the same
solution could be considered and determined, the number of
repeated uses of the same solution on different batches of feed
is worth investigated.
ACKNOWLEDGMENT
The authors would like to acknowledge Oromia Agricultural
Research Institute and the Ethiopian Science and Technology
Agency for financing g the study.
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