Excess feeding of stovers from sorghum and maize for small ruminants
and cattle in cereal based integrated farming systems in Africa
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Second FAO Electronic Conference on Tropical Feeds
Livestock Feed Resources within Integrated Farming Systems
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EXCESS FEEDING OF STOVERS FROM SORGHUM AND MAIZE FOR SMALL
RUMINANTS AND CATTLE IN CEREAL BASED INTEGRATED FARMING
SYSTEMS IN AFRICA
E.L.K. Osafo (1), E. Owen (2), J. Methu (3), A. Abate (4),
J.C. Tanner (5) and A.A.O. Aboud (6)
(1) Department of Animal Science, University of Science and
Technology, Kumasi, Ghana;
E-Mail: USTLIB@UST.gn.apc.org
(2) Department of Agriculture, The University of Reading,
Earley Gate, PO Box 236, Reading, RG6 6AT, UK;
E-Mail: E.Owen@reading.ac.uk
(3) Kenya Agricultural Research Institute, NARC, Muguga, PO
Box 30148, Nairobi, Kenya;
(4) Department of Animal Production, University of Nairobi, PO
Box 29053, Nairobi, Kenya;
(5) International Livestock Research Institute, PO Box 30709,
Nairobi, Kenya;
(6) Department of Animal Science and Production, Sokoine
University of Agriculture, PO Box 3004, Morogoro, Tanzania
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ABSTRACT
Surveys of small-scale farmers growing sorghum in Ethiopia and
maize in Kenya showed that stover was used as livestock feed
during the dry season. Feeding method generally involved
offering crudely-chopped (i.e. machete), stover in large
quantities, with refusals either re-offered to less valuable
animals (eg. donkeys in Ethiopia), and/or used as fuel, mulch
or compost with excreta. Experiments were undertaken to
quantify the effect of varying extents of excess feeding on
stover intake and livestock production; cottonseed cake and
minerals supplementation was provided. In Ethiopia, using
machine-chopped sorghum stover, sheep offered 25, 50 or 75 g
stover/kg live weight (M), daily (d), increased their intake
and growth rate with increasing excess rate (intake, g DM/kg
M.d: 22.1, 31.1 and 32.5; growth rate, g/d: 28.2, 54.1 and
62.2). With increasing excess rate, sheep consumed more leaf
and less stem. Amount of stover refused also increased with
excess rate (g/kg offered: 51, 318 and 526). Goats responded
similarly. In another study, the effects of increasing the
excess rate (25 vs 50 g/kg M.d) and chopping were additive in
improving intake and growth rate of sheep. However, with
cattle, chopping reduced intake of stover, but increasing the
excess rate of unchopped stover improved performance. In a
comparison of stover from a bird-resistant and
non-bird-resistant variety, there was no difference in intake
by sheep, but in the same trial, increasing the excess rate
from 25 to 50 g/kg M.d increased intake. In Kenya, when
mid-lactation, cross-bred cows were fed minerals and 3.2 kg
DM/d cottonseed cake and offered 30, 60 or 90 g DM/kg M.d of
unchopped maize stover, intake of stover (kg DM/d: 8.1, 11.3
and 13.2) and yield of milk (l/d: 10.0, 11.3 and 12.3)
increased with increasing excess rate. The experiments
demonstrate improved animal productivity from an excess
feeding-rate strategy for sorghum and maize stovers. It is
concluded that integrated farming systems involving excess
feeding strategies now need to be modeled, so that
interventions to improve the systems may be identified.
However, to develop the models, it will be necessary to
generate further input/output information, especially
regarding strategies for utilising refused stover.
KEY WORDS: Excess feeding, straw, sorghum, maize, stover
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EXCESS FEEDING OF STOVERS FROM SORGHUM AND MAIZE FOR SMALL
RUMINANTS AND CATTLE IN CEREAL BASED INTEGRATED FARMING
SYSTEMS IN AFRICA
E.L.K. Osafo (1), E. Owen (2), J. Methu (3), A. Abate (4),
J.C. Tanner (5) and A.A.O. Aboud (6)
(1) Department of Animal Science, University of Science and
Technology, Kumasi, Ghana;
E-Mail: USTLIB@UST.gn.apc.org
(2) Department of Agriculture, The University of Reading,
Earley Gate, PO Box 236, Reading, RG6 6AT, UK;
E-Mail: E.Owen@reading.ac.uk
(3) Kenya Agricultural Research Institute, NARC, Muguga, PO
Box 30148, Nairobi, Kenya;
(4) Department of Animal Production, University of Nairobi, PO
Box 29053, Nairobi, Kenya;
(5) International Livestock Research Institute, PO Box 30709,
Nairobi, Kenya;
(6) Department of Animal Science and Production, Sokoine
University of Agriculture, PO Box 3004, Morogoro, Tanzania
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INTRODUCTION
Farmer group surveys in sorghum-growing areas of Ethiopia
(Nazret, Eastern Hararghe and Ada) showed farm sizes to range
from 1.6 to 5 ha, with up to 54% of the cultivated area in
sorghum (Osafo, 1993). Despite problems of grain damage by
birds, farmers preferred local, non-bird-resistant varieties
of sorghum to modern, bird-resistant ones, because of higher
palatability of grain and more drought resistance. Sorghum
stover and teff straw were major livestock feeds in the dry
season, with draught oxen and milk cows having priority over
small ruminants and donkeys, in access to crop residues.
Stover feeding involved in situ grazing and stall feeding, the
latter using either long stover, or crudely chopped (i.e.
machete). Stems were used for fencing. Because of acute
shortage of fuelwood, uneaten stover was used as fuel, often
mixed with cow faeces and tree leaves (e.g. Eucalyptus). There
was little use of residues for mulching or composting.
Surveys (Methu et al., 1996; Wais, 1996) showed that
smallholder dairying in Central Kenya Highlands (Kiambu) based
on cut-and-carry feeding with exotic dairy breeds (mainly
Friesian and Ayrshire), is a major enterprise on small-scale
(2 ha) farms. Crops grown involve Napier grass (0.8 ha), maize
(0.36 ha, two crops per year) and horticultural crops. Except
in the dry season, napier grass is the major basal component
of dairy rations. Maize stover (approximately 2.6 t
DM/ha.year) could play a larger role in dry-season feeding if
problems of low intake and low nutritive value were
alleviated. Omore (1996) reported milk yields averaging only
5.8 kg/d over lactations extending beyond 24 months.
Concentrate feeds from commercial dairy meals, cereal brans
and oilseed cakes were purchased by over 70% of farmers, but
concentrates were fed at very low levels.
In both Ethiopia and Kenya, there was no evidence of farmers
adopting technologies such as urea-ammonia treatment of
sorghum and maize stovers to improve intake and nutritive
value. Farmers surveyed in Kenya were unaware of residue
upgrading technologies (Methu et al., 1996). This confirms the
earlier findings of Owen and Jayasuriya (1989) and the recent
conclusions of Devendra (1996).
Research by Wahed et al.(1990) using barley straw, and
Zemmelink (1980) using tropical grasses and legumes, showed
that an `excess feeding' strategy resulted in increased intake
of digestible organic matter. In view of this, a series of
experiments was conducted with sorghum and maize stovers to
investigate whether excess feeding would increase intake and
productivity of ruminants. It was hypothesised that this
approach would provide an adoptable and sustainable strategy
for alleviating the problem of low nutritive value of stovers.
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EXPERIMENTS UNDERTAKEN
THE EXCESS FEEDING APPROACH
The method involved offering differing amounts of stover, on
the basis of the live weight (M) of animals, such that the
proportion refused increased dramatically above the
conventional ad libitum rate of 0.15 kg refused/kg offered.
Except for one experiment (Osafo et al., 1993a), supplements
of cottonseed cake and minerals were provided. Measurements
were made of the quantity and quality (botanical fractions) of
stover offered and refused.
Three experiments with sorghum stover were conducted at the
International Livestock Research Institute (ILRI), Debre Zeit,
Ethiopia and one with maize stover at the Kenya Agricultural
Research Institute (KARI), Muguga, Nairobi.
EXPERIMENT 1: EFFECTS OF AMOUNT OF CHOPPED SORGHUM STOVER
OFFERED IN GOATS AND SHEEP
The stover used (Seredo, bird-resistant variety) was coarsely
chopped using a tractor-driven chopper (Alvan-Blanch Maxi
chaff cutter). Both goats and sheep increased their intake of
stover with increasing amounts of stover offered, and this was
reflected in increasing growth rates (Table 1). As the amount
offered increased, the content of leaf and sheath in the
stover consumed increased and that of stem decreased,
indicating selection for the more nutritious leaf and sheath
components. Also clearly evident, was the increasing
proportion of refused stover as the amount offered increased
(Table 1).
Table 1: Effects of amount of chopped sorghum stover offered,
in goats and sheep in Ethiopia (Aboud et al., 1993)
Goat Sheep
---------------- ----------------
Amount offered (g/kg M.d) 25 50 75 25 50 75
Number/treatment 7 7 7 8 8 7
Initial weight (M) (kg) 15.4 16.3 16.3 14.7 16.3 16.5
Stover refused
(kg/kg offered) 0.15 0.43 0.57 0.05 0.32 0.53
Stover intake (1)
(g DM/kg M.d) 19.9 26.3 29.1 22.1 31.1 32.5
Growth rate (1) (g/d) 9.4 23.4 31.6 28.2 54.1 62.2
(1) Measurements over 75 d following a 21-d preliminary
period, supplements given: 150 g/d cottonseed cake and mineral
licks; s.e.d. for stover intake, 1.09; s.e.d. for growth rate,
8.70
EXPERIMENT 2: EFFECTS OF AMOUNT OF STOVER OFFERED AND CHOPPING
IN SHEEP AND CATTLE
The stover used was a non-bird-resistant variety (Dinkamash).
Both sheep and cattle showed greater intakes when the amount
of stover offered was doubled, and this was reflected in
increased growth rates (Table 2). However, chopping increased
intake in sheep, but decreased intake in cattle. This result
has an important practical implication in view of the fact
that chopping (albeit ill-defined) is widely advocated when
feeding sorghum and maize stovers.
Table 2: Effects of amount of stover offered and chopping, in
sheep and cattle in Ethiopia (Osafo et al., 1993b)
Form of stover UNCHOPPED CHOPPED
------------- -------------
Amount offered (g/kg M.d) 25 50 25 50
SHEEP (1)
No. of pens (2) 4 4 4 4
Initial weight (M) (kg/pen) 51.8 51.0 50.4 51.2
Growth rate (3) (g/animal.d) 30.5 56.0 45.8 70.5
Stover offered (kg DM/pen.d) 1.25 2.56 1.23 2.60
Stover refused (kg/kg offered) 0.21 0.52 0.11 0.38
Stover intake (4) (kg DM/pen.d) 0.98 1.24 1.08 1.60
Stover intake (g DM/kg M.d) 18.9 24.3 21.4 31.3
CATTLE (5)
No. of steers 8 8 7 8
Initial weight (M), kg 204 204 200 203
Growth rate (6) (kg/d) 0.25 0.43 0.36 0.44
Stover offered (kg DM/d) 4.9 9.5 5.1 9.9
Stover refused (kg/kg offered) 0.24 0.51 0.29 0.62
Stover intake (7) (kg DM/d) 3.7 4.7 3.6 3.9
Stover intake (g DM/kg M.d) 18.1 23.0 18.0 19.2
(1) Measurements over 56 d, supplements given: 310 g/d
cottonseed cake and mineral licks;
(2) 3 rams/pen;
(3) s.e.d. 4.86;
(4) s.e.d. 0.100;
(5) measurements over 49 d, supplements given: 800 g/d
cottonseed cake and mineral licks;
(6) s.e.d. 0.083;
(7) s.e.d. 0.22
EXPERIMENT 3: EFFECTS OF AMOUNT OF CHOPPED STOVER OFFERED AND
VARIETY OF STOVER IN SHEEP
Experiment 3 tested the hypothesis that stover from
bird-resistant sorghum would be less nutritious than stover
from non-bird-resistant sorghum because of the higher
anti-nutritive factors in bird-resistant varieties (Reed et
al., 1987). Table 3 shows that although digestibility was
lower in the bird-resistant stover, intake was unaffected.
This was probably due to the higher leaf-plus-sheath to stem
ratio in the bird-resistant stover used. Osafo (1993) found
large variation in the leaf-plus-sheath:stem ratios between
varieties of both bird-resistant and non-bird-resistant
sorghums. Experiment 3 involved offering stover without
supplementation to simulate farmer practice. It is notable
that sheep offered the higher rate of stover maintained
weight.
Table 3: Effects of amount of chopped sorghum stover offered
and variety of stover, in sheep in Ethiopia (Osafo et al.,
1993a)
Variety Non-bird Bird
resistant (1) resistant (2)
Amount offered ------------- -------------
(g DM/kg M.d) 25 50 25 50
INTAKE TRIAL (3)
No. of rams 12 12 12 12
Initial weight (M) (kg) 20.0 20.1 20.1 19.9
Growth rate (4) (g/d) -25.3 3.5 -16.1 -4.0
Stover offered (g DM/d) 548 1019 537 1011
Stover refused
(kg DM/kg DM offered) 0.13 0.38 0.11 0.38
Stover intake (5) (g DM/d) 474 633 478 628
DIGESTIBILITY TRIAL (6)
No. of rams 4 4 4 4
Live weight (M) (kg) 17.8 18.2 17.8 17.0
Stover offered (g DM/d) 622 1093 619 1067
Stover refused
(kg DM/kg DM offered) 0.13 0.39 0.10 0.37
Stover intake (g DM/d) 544 670 558 676
OM digestibility (7) 0.58 0.56 0.53 0.54
NDF digestibility (8) 0.61 0.57 0.55 0.55
(1) Mixture of Dinkamash and 76T123 varieties),
leaf-plus-sheath:stem, 0.82;
(2) Seredo, leaf-plus-sheath:stem, 1.25;
(3) measurements over 42 d, supplement given: mineral licks
only;
(4) s.e.d 6.2;
(5) s.e.d. 16.0;
(6) measurements over 7 d, supplement given: mineral licks
only;
(7) s.e.d. 0.024;
(8) s.e.d. 0.029
EXPERIMENT 4: EFFECTS OF AMOUNT OF MAIZE STOVER OFFERED IN
MILK COWS
In both Latin squares, intake of maize increased as the amount
offered increased, and this was reflected in greater milk
production, though responses were non-significant (Table 4).
The proportions of leaves and husks in the stover consumed
were greater than in the stover offered, suggesting selection
for these components as opposed to selection against stems and
sheaths. As in Experiments 1 to 3, the proportion of stover
refused increased markedly with increasing offer rate. The
milk yields achieved in this experiment, from mid-lactation
cows on a basal diet of maize stover, were substantial,
although it is acknowledged that 3.2 kg DM/d cottonseed cake
was fed.
Table 4: Effects of amount of maize stover offered, in
lactating cows in Kenya (Methu et al., 1996)
1994 stover (1) 1995 stover (2)
--------------- ---------------
Amount offered
(g DM/kg M.d) 29 57 87 33 60 87
Live weight (M) (kg) 425 436 439 424 438 437
Stover offered (kg DM/d) 12.3 24.7 38.2 13.8 26.5 38.0
Stover intake (3) (kg DM/d) 8.3 11.5 13.2 7.9 11.0 13.2
Stover refused
(kg DM/kg DM offered) 0.32 0.54 0.65 0.41 0.58 0.65
Milk yield (4) (kg/d) 11.2 11.3 13.0 8.8 11.2 11.5
STOVER OFFERED (%)
Stem 42 42 42 50 50 50
Leaf 17 17 17 12 12 12
Sheath 15 15 15 13 13 13
Husk 25 25 25 24 24 24
STOVER CONSUMED (%)
Stem 19 21 31 20 12 20
Leaf 24 28 29 18 19 17
Sheath 23 12 6 22 20 9
Husk 34 39 34 40 49 54
(1) 3 Ayrshire cows in 3x3 Latin square, 24 d/period,
supplements given: 3.2 kg DM/d cottonseed cake and 150 g/d
mineral premix;
(2) 3 Friesian cows in 3x3 Latin square, 24 d/period,
supplements given: 3.2 kg DM/d cottonseed cake and 150 g/d
mineral premix;
(3) s.e.d. for Ayrshires, 1.12, s.e.d. for Friesians, 0.46;
(4) s.e.d. for Ayrshires, 1.54, s.e.d. for Friesians, 0.71
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CONCLUSIONS
The experiments confirmed the hypothesis that excess feeding
of sorghum or maize stover is a method of increasing intake
and productivity of small ruminants and cattle, thus
alleviating the problem of low nutritive value of stovers.
At first sight, the large amount of refused stover generated
by excess feeding would be conceived as unsustainably
wasteful. However, as indicated by surveys in Ethiopia,
residues uneaten by ruminants have a value as feed for donkeys
or substitute for fuelwood.
Stovers refused in an in situ grazing system would be
available for soil incorporation to increase organic matter
(Powell et al., 1995). However, refused stovers, which would
tend to be dominated by the stem fraction, would contain high
C:N ratios. Not only are such residues slow to decompose under
field conditions, but may also immobilise mineral nitrogen
making it unavailable for plant growth.
In Kenya refused maize stover is used as bedding in zero
grazing units. Farmers combine urine-soaked stover with cattle
faeces in heaps or pits for composting prior to application to
crops. Collaborative research being conducted by KARI and ILRI
is currently examining how interactions between the quality of
diets based on maize stover, bedding, manure management and
composting techniques influence the quality of organic
fertilizers produced. Under the intensive farming systems
practised in the highlands of East and Central Africa, excreta
is a highly valued output of the livestock sub-system.
In Indonesia, excess feeding of indigenous forages is already
practised by farmers with the main intention of maximising
yield of manure-compost production made from refused forage
and excreta (Tanner et al., 1996). In Indonesia, excess
feeding therefore not only increases animal productivity per
se, but also maximises outputs from the livestock enterprise
which are of benefit to crops.
There is a need to model input-output relationships concerning
the excess feeding approach and the use of supplements in
order to optimise the sustainable use of sorghum and maize
stovers in cereal-based integrated farming systems in Africa
and elsewhere.
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ACKNOWLEDGEMENTS
Authors acknowledge financial sponsorship from the ODA's
Livestock Production Programme (LPP) and the International
Livestock Research Institute, Nairobi.
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