Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol84.Issue1-2.Apr2000:
Animal Feed Science and Technology
84 (2000) 137±145
Short communication
Nutrient composition of native forbs of semi-arid
and dry sub-humid savannas of Nigeria
Muh.S. Kallaha,*, J.O. Balea, U.S. Abdullahib,
I.R. Muhammada, R. Lawala
a
National Animal Production Research Institute, Ahmadu Bello University, PMB 1096,
Shika-Zaria, Nigeria
b
Veterinary Teaching Hospital, Faculty of Veterinary Medicine,
Ahmadu Bello University, Samaru, Zaria, Nigeria
Received 20 January 1999; received in revised form 13 July 1999; accepted 3 November 1999
Abstract
A preliminary investigation was carried out to evaluate the nutritive value of six forb species
widely used as feedstuffs in West Africa. The study examined four legumes (Crotalaria
senegalensis, C. goreensis, Alysicarpus glumaceous and A. rugosus) and two non-legumes (Cassia
mimosoides and Ipomea eriocarpa).
Field observations on gross phenology of these forbs illustrate their potentials in increasing the
range of native forages for use in pasture development or improvement. All species sustained
growth on residual soil moisture into the dry season providing green forage when most associated
forages had dried up. Results of chemical analysis reveal that the species have properties in terms of
contents of protein and some mineral elements that could be advantageously employed to balance
animal ration or improve the quality of standing hay of tropical pastures. The species had mean
values of 14±18% CP, 3.5±7.0% Ca and 40±58% DMD. Levels of Ca was high and more than 10
times the standard requirements for ruminant production in the tropics. While levels of P, K, Mg and
Fe were suf®cient, Mn and Na were low, and apparently de®cient. The high levels of Ca resulted in
unusually wide Ca : P ratios of 16 : 1±33 : 1 among the species. The implications of these ®ndings
on uses of the forages in ruminant nutrition and the need for intensive studies on the observed
results are discussed. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Crotalaria senegalensis; C. goreensis; Alysicarpus glumaceous; A. rugosus; Cassia mimosoides and
Ipomea eriocarpa; Forbs; Forage; Legumes; Herbaceous dicots; Nutrient composition; Digestibility; Ca: P ratio;
Semi-arid; Dry sub-humid; Savanna; Nigeria
*
Corresponding author. Tel.: 234-6950596; fax: 234-6951272.
E-mail address: lukman@abu.edu.ng (M.S. Kallah)
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 3 1 - 5
138
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
1. Introduction
The broad objective of this investigation was to explore the potentials of forbs
(herbaceous dicotyledonous plant species) commonly described as `weeds' in arable crop
systems for possible integration into livestock feeding systems. In the semi-arid and dry
sub-humid savannas of West Africa, numerous species of herbaceous dicots especially
from the genera Crotalaria, Alysicarpus, Cassia and Ipomea are known to be widely used
in livestock production. Quite often they are plucked or cut, and fed either as fresh or
conserved fodders. The utilisation of these and many other herbs growing naturally within
the farm environment is rather opportunistic. Although there has been some interest
among farmers of including `herbaceous dicotyledonous plants' in diets of animals, so far
no deliberate attempt has been made to cultivate them to evaluate their agronomic
requirements or nutritional value. A close examination of the possible roles of the
palatable species in livestock production systems is quite desirable.
The data reported in this study arose as a result of preliminary observations made on
feeding systems of peri-urban livestock production. While smallholder animal production
around periphery of urban centres is becoming increasingly important as source of food
and income supplement, availability of forage constitutes a major constraint. The paper
presents nutritional information on the palatable species commonly observed being used
in feeding systems of peri-urban livestock production.
2. Materials and methods
Four legume and two non-legume herbaceous dicots were examined during the study.
The legume species were: Crotalaria senegalensis, C. goreensis, Alysicarpus glumaceus
and A. rugosus, while the non-legumes were Cassia mimosoides and Ipomea eriocarpa.
2.1. Plant materials
Plants populations growing naturally in grain sorghum (Sorghum bicolor L.) ®eld were
sampled for chemical analysis. Whole plant cut at the base 10 cm above ground
constituted a sample. The plants were harvested from Kallah-Sanawa Farms, Dutsin-ma
Local Government Area in Katsina State at end of rainy season for a period encompassing
bloom, pod-soft, pod-ripe and pod-dry stages of plant development. Harvesting was done
at weekly intervals from 20 October to 15 December. The study site falls within the semiarid zone at an altitude of 500 m (Latitude N 128270 , Longitude E 078240 ). Soils within
the area are sandy loams laden over sandy clay loams which according to FPDD (1989)
are generally low in organic matter, available phosphate and cation exchange capacity.
The annual rainfall is 870 mm in a discrete rainy season beginning early May and lasting
until mid-October.
2.2. Chemical analysis
The forages were dried in a forced draught oven at 608C and the samples were ground
to pass through 1.0 mm screen using a Christy & Norris Laboratory Mill. The ground
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
139
whole plant samples that included stems, leaves, ¯owers and pods/capsules were analysed
for crude protein (CP), acid detergent ®bre (ADF), and lignin (AOAC, 1984; Procedures
No. 7.003±7.37, 7.074±7.076) and neutral detergent ®bre (NDF) (Van Soest et al., 1991).
Apparent dry matter digestibility (DMD) was calculated using the Van Soest (1967)
summative equation as follows:
DMD 0:98CC NDF 1:473 ÿ 0:789 log ADF ÿ 12:9;
where CC is cell contents, NDF the neutral detergent ®bre and ADF the acid detergent
®bre.
The samples were analysed for the mineral elements according to procedures described
by Faithfull (Faithfull, 1971; 1974). Calcium, Mg, Mn and Fe were read using atomic
absorption spectrophotometer (Shimadzu AA Ð 650 model) while K and Na were
determined by ¯ame photometry (FP 410 Corning). Phosphorus levels were estimated
using Spectronic 20 Baush & Lomb.
2.3. Statistical analysis
The data were analysed using General Linear Models Procedure of Statistical Analysis
System Computer Package (SAS, 1985). As there was no signi®cant interaction between
species and period of sampling, data were pooled among sampling dates and least square
means are given with their standard errors.
3. Results
3.1. General observations
Phenologically, seedlings of these plants emerge in mid-season, grow rapidly and
produce numerous branches. Characteristically the Crotalaria and Cassia species are
erect growing plants (up to 2.5 m). Both Alysicarpus species have basal rosettes with
erect stems bearing long linear leaves. I. eriocarpa, on the other hand, is a trailing plant
with bulbous meristematic bases that send out numerous stolons with tendrils which may
spread horizontally or clasp to adjacent vertical object and grow spirally upwards.
Development of organs in the six species was indeterminate with branches, ¯ower and
pod/capsule production occurring simultaneously and continuously until moisture stress
causes the plants to die off.
The last rain showers during the study year were received on 11 October. Thereafter,
while associated grasses dried up, the species evaluated sustained growth under
residual soil moisture with appreciable production of green forage material. At ®nal
harvesting date (15 December) A. glumaceus and C. mimosoides had dried up. The
other four species (i.e. Crotalaria senegalensis, C. goreensis, A. rugosus and Ipomea
eriocarpa) had vegetative green matter of leaf and herbaceous stems which were
progressively woody towards the base. There was evidence of senescence with abscission
of older leaves, while younger leaves became conspicuously lanceolate or reduced
to bracts.
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M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
3.2. Nutrient composition
Composition of nutrients in the species evaluated are presented in Table 1. Mean
organic matter content vary from 83.4% for Ipomea eriocarpa to 89.4% for Cassia
mimosoides. Crude protein content is fairly high in all species with a range of between
14.3% in C. mimosoides and 18.4% in Alysicarpus glumaceus. Cell wall constituents
Table 1
Nutrient composition of native forbs (herbaceous dicotyledonous plants) of semi-arid savanna of Nigeria
Component (% DM)
Mean
SEM
Range
Crotalaria senegalensis
OM
CP
NDF
ADF
LIGNIN
DMDa
87.4
17.3
50.0
34.4
5.4
49.0
0.25
0.34
0.54
0.20
0.25
0.32
82.8±90.3
13.8±19.3
47.5±52.8
32.6±39.5
3.8±8.4
44.6±51.1
Crotalaria goreensis
OM
CP
NDF
ADF
LIGNIN
DMD
86.8
17.3
55.6
40.4
7.4
42.0
0.37
0.33
0.52
0.20
0.24
0.32
80.1±90.5
13.5±20.5
46.7±61.9
32.1±47.6
5.5±9.6
35.3±46.4
Alysicarpus glumaceus
OM
CP
NDF
ADF
LIGNIN
DMD
84.5
18.4
49.6
37.2
7.3
48.1
0.28
0.33
0.52
0.20
0.24
0.32
80.0±87.7
16.0±21.2
46.4±52.1
33.2±40.1
6.5±7.9
45.0±51.2
Alysicarpus rugosus
OM
CP
NDF
ADF
LIGNIN
DMD
85.7
16.9
57.1
42.0
9.2
39.7
0.35
0.34
0.54
0.43
0.25
0.20
81.3±89.1
13.8±22.0
53.8±60.8
38.2±48.8
7.2±11.3
34.8±43.8
Cassia mimosoides
OM
CP
NDF
ADF
LIGNIN
DMD
89.4
14.3
51.4
35.9
8.9
47.5
0.29
0.35
0.48
0.20
0.17
0.32
85.0±92.0
12.5±19.8
46.3±55.1
30.2±43.1
6.9±9.6
42.0±53.9
Ipomea eriocarpa
OM
CP
NDF
ADF
LIGNIN
DMD
83.4
17.2
42.8
27.7
5.4
57.5
0.33
0.37
0.59
0.20
0.28
0.32
80.6±82.2
15.0±20.8
39.3±45.8
19.6±38.8
3.2±7.4
54.5±64.4
a
DMD calculated using Van Soest (1967) summative equation as follows: DMD 0.98 cell
contents NDF (1.473 ÿ 0.789 log ADF) ÿ 12.9.
141
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
Table 2
Mineral levels in native forbs (herbaceous dicotyledonous plants) of semi-arid savanna of Nigeria
Component (g/kg DM)
Mean
SEM
Range
Crotalaria senegalensis
Ca
P
K
Mg
Na
Mn
Fe
48.2
1.9
16.2
1.6
0.4
0.0a
0.1
1.44
0.06
0.69
0.10
0.01
0.00
0.02
41.92±56.37
1.60±2.20
13.19±18.86
0.82±2.30
0.37±0.43
0.00±0.06a
0.05±0.17
Crotalaria goreensis
Ca
P
K
Mg
Na
Mn
Fe
48.9
1.7
14.2
1.0
0.4
0.0a
0.1
1.44
0.06
0.69
0.10
0.01
0.00
0.02
40.11±61.18
1.20±2.10
4.84±23.65
0.82±1.22
0.30±0.51
0.00±0.02a
0.05±0.28
Alysicarpus glumaceus
Ca
P
K
Mg
Na
Mn
Fe
48.0
2.0
12.2
2.3
0.4
0.0a
0.2
1.44
0.06
0.69
0.10
0.01
0.00
0.02
40.98±53.03
1.70±2.30
7.12±16.76
1.89±3.26
0.35±0.42
0.02±0.05
0.04±0.27
Alysicarpus rugosus
Ca
P
K
Mg
Na
Mn
Fe
42.4
1.6
10.8
1.5
0.4
0.0a
0.2
1.44
0.06
0.69
1.10
0.01
0.00
0.02
35.63±47.42
1.20±2.20
5.60±13.72
1.28±1.97
0.34±0.43
0.00±0.05a
0.04±0.68
Cassia mimosoides
Ca
P
K
Mg
Na
Mn
Fe
35.3
1.9
8.8
0.9
0.3
0.1
0.1
1.40
0.19
1.86
0.06
0.02
0.02
0.05
33.31±39.38
1.60±2.40
3.38±11.70
0.82±1.07
0.27±0.35
0.00±0.08a
0.05±0.28
Ipomea eriocarpa
Ca
P
K
Mg
Na
Mn
Fe
69.9
2.4
18.6
2.8
0.6
0.0a
0.2
1.44
0.06
0.69
0.10
0.01
0.00
0.02
61.02±77.92
2.20±2.60
14.57±24.03
1.72±4.10
0.48±0.60
0.02±0.07
0.07±0.40
a
Trace level.
142
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
(NDF, ADF, Lignin) were lowest in the non-legume I. eriocarpa and highest in the
legume A. rugosus. The Crotalaria and Cassia were intermediate. Reverse ranking order
was found in terms of dry matter digestibility, with low of 39.7% for A. rugosus and high
of 57.5% for I. eriocarpa.
The concentration of mineral elements in the six forb species is given in Table 2. With
exception of Mn, I. eriocarpa ranks highest among the species in mean concentration of
Ca, P, K, Mg and Na while C. mimosoides has the lowest contents of these elements. The
Crotalaria species had the lowest values of Mn and Fe, and intermediate in contents of
the other mineral elements.
3.3. Calcium to phosphorus ratio
Unusually wide ratios were found for the forbs irrespective of the grouping as legume
or non-legume. Mean ratios vary between 19 : 1 for C. mimosoides and 29 : 1 for I.
eriocarpa. Calcium was as high as 7.8% (78 g/kg) in I. eriocarpa while the P content
varied from 0.12% (1.2 g/kg) in C. goreensis and A. rugosus to 0.26% (2.6 g/kg) in
I. eriocarpa.
4. Discussion
Observations on patterns of phenological development of the plants relative to the life
cycles of associated forages in pasture ecosystems within the study area suggest the
potentials of the species in increasing the range of forages available for sown pasture
improvement. Besides extending the supply of green forage into the dry season, the levels
of nutrient constituents were promising and could be of advantage in balancing diets or
pasture stand quality. All species evaluated sustained growth producing fresh fodder and
seeds for up to two months into the dry season when almost all associated grasses had
dried up. The use of these species in pasture plant associations could be strategically
employed to develop pasture system that would supply green forage for a signi®cant
portion of the dry season.
The potential advantages of using dicotyledonous species to enhance the concentration
of mineral elements (e.g. N, Ca, Mg) in the diet of grazing animal had been suggested by
Wilman and Derrick (1994). Multi-species pasture containing the selected forb in a
desired proportion may be developed and sustained. An option was to include in diet a
proportion of species which are inherently high in concentration of particular elements.
The species in this study are particularly high in Ca and K.
Relative to native grasses and other conventional fodder plants (e.g. Haggar, 1970;
Kapu, 1975; Minson, 1990), the species analysed had nutrient levels indicative of forages
of good quality. Crude protein range of 14.3 and 18.4% is more than that found in several
tropical grasses (Minson, 1990). It is comparable to content in the introduced legumes
tested in the coastal grasslands of West Africa (Adjei and Fianu, 1985; Ikhimioya and
Olagunju, 1996). Earlier studies on a wide variety of naturally growing native herbaceous
dicots in East Africa (Dougall and Bogdan, 1966; Gihad, 1976) indicated crude protein
content in the range of 9.5±35.9%. The six species in the present report were within this
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
143
range. Ten species of Crotalaria in the report of Dougall and Bogdan (1966) had higher
mean CP (25%) and P (0.3%) but considerably lower Ca (0.8%) than concentrations
found in our study.
The forages appear promising in terms of their energy content for supporting
production. Judging from the calculated coef®cients of dry matter digestibility, four of the
species have digestibility values above 45% which is considered adequate for high animal
performance on pastures (McDowell, 1972; Holt, 1977). Relative to most tropical forages
the mean values of DMD found in this study are more than encouraging. The forages
grown in combination with grass or included in ration formulation could enhance balance
of nutrient elements that may be lacking in grasses at advanced stages of maturity.
Mineral composition of forages varies with soil fertility, plant specie and stage of
maturity. In the present study, soil fertility status was not examined while interaction
between composition and maturity was not found signi®cant for the stages examined.
Relative to animal requirements for production in tropical grassland ecosystems
(McDowell, 1997) all species appeared quite suitable for animal nutrition in terms of
contents of Ca, P, K, Mg, and Fe, although rather low in Mn for production. They appear
de®cient in Mn and Na compared to animal requirements from the feeding standards
ARC (1980) and McDowell (1997). The levels of P in this study contrast to the suboptimal levels of P commonly reported in grasses, legumes and browses of the savannas
of Nigeria (Kapu, 1975; Adamu et al., 1993; Kallah et al., 1995; Campbell et al., 1996;
Kallah et al., 1997, 1999).
The Ca : P ratio in feeds is an important consideration in the nutrition of the animal Ð
with tolerable limits being in the range of 1 : 1 and 7 : 1 for ruminants. Wide ratios found
in this study is attributable to high Ca content of the forages. Relative to the suggested
range of 0.19±0.77% Ca requirements in diets of ruminants grazing native tropical
pastures (McDowell, 1997) the forages recorded more than 10 times the levels of Ca.
Although the levels of P in forages had been found to fall within the required range, the
gross excess of Ca is likely to aggravate aphosphorosis in unsupplemented animals.
5. Conclusion
Forbs (herbaceous dicotyledonous plants) are important components of grassland
ecosystem of the semi-arid and dry sub-humid savannas of West Africa. In arable crop
systems, they are commonly referred to as `weeds'. Four legumes (Crotalaria
senegalensis, C. goreensis, Alysicarpus glumaceus, A. rugosus) and two non-legumes
(Cassia mimosoides and Ipomea eriocarpa) evaluated are potential useful forages for
inclusion in sown pasture production. The species are palatable with prospects for
extending the dry season supply of green forage. All species were found to sustain growth
and produce fresh fodder into the dry season when most of the associated grasses had
dried up. The six species appear quite promising for unimproved tropical forages in
contents of protein (up to 18% CP), energy (up to 58% DMD) and some mineral
elements. The calcium to phosphorus relations found need critical evaluation. For
integration into sown pasture systems, intensive studies are required to de®ne their
agronomic requirements, yield potentials and further evaluate feeding value parameters.
144
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
Acknowledgements
The authors are grateful to the Director, National Animal Production Research
Institute, Ahmadu Bello University, Shika-Zaria for permission to publish the work.
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84 (2000) 137±145
Short communication
Nutrient composition of native forbs of semi-arid
and dry sub-humid savannas of Nigeria
Muh.S. Kallaha,*, J.O. Balea, U.S. Abdullahib,
I.R. Muhammada, R. Lawala
a
National Animal Production Research Institute, Ahmadu Bello University, PMB 1096,
Shika-Zaria, Nigeria
b
Veterinary Teaching Hospital, Faculty of Veterinary Medicine,
Ahmadu Bello University, Samaru, Zaria, Nigeria
Received 20 January 1999; received in revised form 13 July 1999; accepted 3 November 1999
Abstract
A preliminary investigation was carried out to evaluate the nutritive value of six forb species
widely used as feedstuffs in West Africa. The study examined four legumes (Crotalaria
senegalensis, C. goreensis, Alysicarpus glumaceous and A. rugosus) and two non-legumes (Cassia
mimosoides and Ipomea eriocarpa).
Field observations on gross phenology of these forbs illustrate their potentials in increasing the
range of native forages for use in pasture development or improvement. All species sustained
growth on residual soil moisture into the dry season providing green forage when most associated
forages had dried up. Results of chemical analysis reveal that the species have properties in terms of
contents of protein and some mineral elements that could be advantageously employed to balance
animal ration or improve the quality of standing hay of tropical pastures. The species had mean
values of 14±18% CP, 3.5±7.0% Ca and 40±58% DMD. Levels of Ca was high and more than 10
times the standard requirements for ruminant production in the tropics. While levels of P, K, Mg and
Fe were suf®cient, Mn and Na were low, and apparently de®cient. The high levels of Ca resulted in
unusually wide Ca : P ratios of 16 : 1±33 : 1 among the species. The implications of these ®ndings
on uses of the forages in ruminant nutrition and the need for intensive studies on the observed
results are discussed. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Crotalaria senegalensis; C. goreensis; Alysicarpus glumaceous; A. rugosus; Cassia mimosoides and
Ipomea eriocarpa; Forbs; Forage; Legumes; Herbaceous dicots; Nutrient composition; Digestibility; Ca: P ratio;
Semi-arid; Dry sub-humid; Savanna; Nigeria
*
Corresponding author. Tel.: 234-6950596; fax: 234-6951272.
E-mail address: lukman@abu.edu.ng (M.S. Kallah)
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 9 9 ) 0 0 1 3 1 - 5
138
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
1. Introduction
The broad objective of this investigation was to explore the potentials of forbs
(herbaceous dicotyledonous plant species) commonly described as `weeds' in arable crop
systems for possible integration into livestock feeding systems. In the semi-arid and dry
sub-humid savannas of West Africa, numerous species of herbaceous dicots especially
from the genera Crotalaria, Alysicarpus, Cassia and Ipomea are known to be widely used
in livestock production. Quite often they are plucked or cut, and fed either as fresh or
conserved fodders. The utilisation of these and many other herbs growing naturally within
the farm environment is rather opportunistic. Although there has been some interest
among farmers of including `herbaceous dicotyledonous plants' in diets of animals, so far
no deliberate attempt has been made to cultivate them to evaluate their agronomic
requirements or nutritional value. A close examination of the possible roles of the
palatable species in livestock production systems is quite desirable.
The data reported in this study arose as a result of preliminary observations made on
feeding systems of peri-urban livestock production. While smallholder animal production
around periphery of urban centres is becoming increasingly important as source of food
and income supplement, availability of forage constitutes a major constraint. The paper
presents nutritional information on the palatable species commonly observed being used
in feeding systems of peri-urban livestock production.
2. Materials and methods
Four legume and two non-legume herbaceous dicots were examined during the study.
The legume species were: Crotalaria senegalensis, C. goreensis, Alysicarpus glumaceus
and A. rugosus, while the non-legumes were Cassia mimosoides and Ipomea eriocarpa.
2.1. Plant materials
Plants populations growing naturally in grain sorghum (Sorghum bicolor L.) ®eld were
sampled for chemical analysis. Whole plant cut at the base 10 cm above ground
constituted a sample. The plants were harvested from Kallah-Sanawa Farms, Dutsin-ma
Local Government Area in Katsina State at end of rainy season for a period encompassing
bloom, pod-soft, pod-ripe and pod-dry stages of plant development. Harvesting was done
at weekly intervals from 20 October to 15 December. The study site falls within the semiarid zone at an altitude of 500 m (Latitude N 128270 , Longitude E 078240 ). Soils within
the area are sandy loams laden over sandy clay loams which according to FPDD (1989)
are generally low in organic matter, available phosphate and cation exchange capacity.
The annual rainfall is 870 mm in a discrete rainy season beginning early May and lasting
until mid-October.
2.2. Chemical analysis
The forages were dried in a forced draught oven at 608C and the samples were ground
to pass through 1.0 mm screen using a Christy & Norris Laboratory Mill. The ground
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
139
whole plant samples that included stems, leaves, ¯owers and pods/capsules were analysed
for crude protein (CP), acid detergent ®bre (ADF), and lignin (AOAC, 1984; Procedures
No. 7.003±7.37, 7.074±7.076) and neutral detergent ®bre (NDF) (Van Soest et al., 1991).
Apparent dry matter digestibility (DMD) was calculated using the Van Soest (1967)
summative equation as follows:
DMD 0:98CC NDF 1:473 ÿ 0:789 log ADF ÿ 12:9;
where CC is cell contents, NDF the neutral detergent ®bre and ADF the acid detergent
®bre.
The samples were analysed for the mineral elements according to procedures described
by Faithfull (Faithfull, 1971; 1974). Calcium, Mg, Mn and Fe were read using atomic
absorption spectrophotometer (Shimadzu AA Ð 650 model) while K and Na were
determined by ¯ame photometry (FP 410 Corning). Phosphorus levels were estimated
using Spectronic 20 Baush & Lomb.
2.3. Statistical analysis
The data were analysed using General Linear Models Procedure of Statistical Analysis
System Computer Package (SAS, 1985). As there was no signi®cant interaction between
species and period of sampling, data were pooled among sampling dates and least square
means are given with their standard errors.
3. Results
3.1. General observations
Phenologically, seedlings of these plants emerge in mid-season, grow rapidly and
produce numerous branches. Characteristically the Crotalaria and Cassia species are
erect growing plants (up to 2.5 m). Both Alysicarpus species have basal rosettes with
erect stems bearing long linear leaves. I. eriocarpa, on the other hand, is a trailing plant
with bulbous meristematic bases that send out numerous stolons with tendrils which may
spread horizontally or clasp to adjacent vertical object and grow spirally upwards.
Development of organs in the six species was indeterminate with branches, ¯ower and
pod/capsule production occurring simultaneously and continuously until moisture stress
causes the plants to die off.
The last rain showers during the study year were received on 11 October. Thereafter,
while associated grasses dried up, the species evaluated sustained growth under
residual soil moisture with appreciable production of green forage material. At ®nal
harvesting date (15 December) A. glumaceus and C. mimosoides had dried up. The
other four species (i.e. Crotalaria senegalensis, C. goreensis, A. rugosus and Ipomea
eriocarpa) had vegetative green matter of leaf and herbaceous stems which were
progressively woody towards the base. There was evidence of senescence with abscission
of older leaves, while younger leaves became conspicuously lanceolate or reduced
to bracts.
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M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
3.2. Nutrient composition
Composition of nutrients in the species evaluated are presented in Table 1. Mean
organic matter content vary from 83.4% for Ipomea eriocarpa to 89.4% for Cassia
mimosoides. Crude protein content is fairly high in all species with a range of between
14.3% in C. mimosoides and 18.4% in Alysicarpus glumaceus. Cell wall constituents
Table 1
Nutrient composition of native forbs (herbaceous dicotyledonous plants) of semi-arid savanna of Nigeria
Component (% DM)
Mean
SEM
Range
Crotalaria senegalensis
OM
CP
NDF
ADF
LIGNIN
DMDa
87.4
17.3
50.0
34.4
5.4
49.0
0.25
0.34
0.54
0.20
0.25
0.32
82.8±90.3
13.8±19.3
47.5±52.8
32.6±39.5
3.8±8.4
44.6±51.1
Crotalaria goreensis
OM
CP
NDF
ADF
LIGNIN
DMD
86.8
17.3
55.6
40.4
7.4
42.0
0.37
0.33
0.52
0.20
0.24
0.32
80.1±90.5
13.5±20.5
46.7±61.9
32.1±47.6
5.5±9.6
35.3±46.4
Alysicarpus glumaceus
OM
CP
NDF
ADF
LIGNIN
DMD
84.5
18.4
49.6
37.2
7.3
48.1
0.28
0.33
0.52
0.20
0.24
0.32
80.0±87.7
16.0±21.2
46.4±52.1
33.2±40.1
6.5±7.9
45.0±51.2
Alysicarpus rugosus
OM
CP
NDF
ADF
LIGNIN
DMD
85.7
16.9
57.1
42.0
9.2
39.7
0.35
0.34
0.54
0.43
0.25
0.20
81.3±89.1
13.8±22.0
53.8±60.8
38.2±48.8
7.2±11.3
34.8±43.8
Cassia mimosoides
OM
CP
NDF
ADF
LIGNIN
DMD
89.4
14.3
51.4
35.9
8.9
47.5
0.29
0.35
0.48
0.20
0.17
0.32
85.0±92.0
12.5±19.8
46.3±55.1
30.2±43.1
6.9±9.6
42.0±53.9
Ipomea eriocarpa
OM
CP
NDF
ADF
LIGNIN
DMD
83.4
17.2
42.8
27.7
5.4
57.5
0.33
0.37
0.59
0.20
0.28
0.32
80.6±82.2
15.0±20.8
39.3±45.8
19.6±38.8
3.2±7.4
54.5±64.4
a
DMD calculated using Van Soest (1967) summative equation as follows: DMD 0.98 cell
contents NDF (1.473 ÿ 0.789 log ADF) ÿ 12.9.
141
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
Table 2
Mineral levels in native forbs (herbaceous dicotyledonous plants) of semi-arid savanna of Nigeria
Component (g/kg DM)
Mean
SEM
Range
Crotalaria senegalensis
Ca
P
K
Mg
Na
Mn
Fe
48.2
1.9
16.2
1.6
0.4
0.0a
0.1
1.44
0.06
0.69
0.10
0.01
0.00
0.02
41.92±56.37
1.60±2.20
13.19±18.86
0.82±2.30
0.37±0.43
0.00±0.06a
0.05±0.17
Crotalaria goreensis
Ca
P
K
Mg
Na
Mn
Fe
48.9
1.7
14.2
1.0
0.4
0.0a
0.1
1.44
0.06
0.69
0.10
0.01
0.00
0.02
40.11±61.18
1.20±2.10
4.84±23.65
0.82±1.22
0.30±0.51
0.00±0.02a
0.05±0.28
Alysicarpus glumaceus
Ca
P
K
Mg
Na
Mn
Fe
48.0
2.0
12.2
2.3
0.4
0.0a
0.2
1.44
0.06
0.69
0.10
0.01
0.00
0.02
40.98±53.03
1.70±2.30
7.12±16.76
1.89±3.26
0.35±0.42
0.02±0.05
0.04±0.27
Alysicarpus rugosus
Ca
P
K
Mg
Na
Mn
Fe
42.4
1.6
10.8
1.5
0.4
0.0a
0.2
1.44
0.06
0.69
1.10
0.01
0.00
0.02
35.63±47.42
1.20±2.20
5.60±13.72
1.28±1.97
0.34±0.43
0.00±0.05a
0.04±0.68
Cassia mimosoides
Ca
P
K
Mg
Na
Mn
Fe
35.3
1.9
8.8
0.9
0.3
0.1
0.1
1.40
0.19
1.86
0.06
0.02
0.02
0.05
33.31±39.38
1.60±2.40
3.38±11.70
0.82±1.07
0.27±0.35
0.00±0.08a
0.05±0.28
Ipomea eriocarpa
Ca
P
K
Mg
Na
Mn
Fe
69.9
2.4
18.6
2.8
0.6
0.0a
0.2
1.44
0.06
0.69
0.10
0.01
0.00
0.02
61.02±77.92
2.20±2.60
14.57±24.03
1.72±4.10
0.48±0.60
0.02±0.07
0.07±0.40
a
Trace level.
142
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
(NDF, ADF, Lignin) were lowest in the non-legume I. eriocarpa and highest in the
legume A. rugosus. The Crotalaria and Cassia were intermediate. Reverse ranking order
was found in terms of dry matter digestibility, with low of 39.7% for A. rugosus and high
of 57.5% for I. eriocarpa.
The concentration of mineral elements in the six forb species is given in Table 2. With
exception of Mn, I. eriocarpa ranks highest among the species in mean concentration of
Ca, P, K, Mg and Na while C. mimosoides has the lowest contents of these elements. The
Crotalaria species had the lowest values of Mn and Fe, and intermediate in contents of
the other mineral elements.
3.3. Calcium to phosphorus ratio
Unusually wide ratios were found for the forbs irrespective of the grouping as legume
or non-legume. Mean ratios vary between 19 : 1 for C. mimosoides and 29 : 1 for I.
eriocarpa. Calcium was as high as 7.8% (78 g/kg) in I. eriocarpa while the P content
varied from 0.12% (1.2 g/kg) in C. goreensis and A. rugosus to 0.26% (2.6 g/kg) in
I. eriocarpa.
4. Discussion
Observations on patterns of phenological development of the plants relative to the life
cycles of associated forages in pasture ecosystems within the study area suggest the
potentials of the species in increasing the range of forages available for sown pasture
improvement. Besides extending the supply of green forage into the dry season, the levels
of nutrient constituents were promising and could be of advantage in balancing diets or
pasture stand quality. All species evaluated sustained growth producing fresh fodder and
seeds for up to two months into the dry season when almost all associated grasses had
dried up. The use of these species in pasture plant associations could be strategically
employed to develop pasture system that would supply green forage for a signi®cant
portion of the dry season.
The potential advantages of using dicotyledonous species to enhance the concentration
of mineral elements (e.g. N, Ca, Mg) in the diet of grazing animal had been suggested by
Wilman and Derrick (1994). Multi-species pasture containing the selected forb in a
desired proportion may be developed and sustained. An option was to include in diet a
proportion of species which are inherently high in concentration of particular elements.
The species in this study are particularly high in Ca and K.
Relative to native grasses and other conventional fodder plants (e.g. Haggar, 1970;
Kapu, 1975; Minson, 1990), the species analysed had nutrient levels indicative of forages
of good quality. Crude protein range of 14.3 and 18.4% is more than that found in several
tropical grasses (Minson, 1990). It is comparable to content in the introduced legumes
tested in the coastal grasslands of West Africa (Adjei and Fianu, 1985; Ikhimioya and
Olagunju, 1996). Earlier studies on a wide variety of naturally growing native herbaceous
dicots in East Africa (Dougall and Bogdan, 1966; Gihad, 1976) indicated crude protein
content in the range of 9.5±35.9%. The six species in the present report were within this
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
143
range. Ten species of Crotalaria in the report of Dougall and Bogdan (1966) had higher
mean CP (25%) and P (0.3%) but considerably lower Ca (0.8%) than concentrations
found in our study.
The forages appear promising in terms of their energy content for supporting
production. Judging from the calculated coef®cients of dry matter digestibility, four of the
species have digestibility values above 45% which is considered adequate for high animal
performance on pastures (McDowell, 1972; Holt, 1977). Relative to most tropical forages
the mean values of DMD found in this study are more than encouraging. The forages
grown in combination with grass or included in ration formulation could enhance balance
of nutrient elements that may be lacking in grasses at advanced stages of maturity.
Mineral composition of forages varies with soil fertility, plant specie and stage of
maturity. In the present study, soil fertility status was not examined while interaction
between composition and maturity was not found signi®cant for the stages examined.
Relative to animal requirements for production in tropical grassland ecosystems
(McDowell, 1997) all species appeared quite suitable for animal nutrition in terms of
contents of Ca, P, K, Mg, and Fe, although rather low in Mn for production. They appear
de®cient in Mn and Na compared to animal requirements from the feeding standards
ARC (1980) and McDowell (1997). The levels of P in this study contrast to the suboptimal levels of P commonly reported in grasses, legumes and browses of the savannas
of Nigeria (Kapu, 1975; Adamu et al., 1993; Kallah et al., 1995; Campbell et al., 1996;
Kallah et al., 1997, 1999).
The Ca : P ratio in feeds is an important consideration in the nutrition of the animal Ð
with tolerable limits being in the range of 1 : 1 and 7 : 1 for ruminants. Wide ratios found
in this study is attributable to high Ca content of the forages. Relative to the suggested
range of 0.19±0.77% Ca requirements in diets of ruminants grazing native tropical
pastures (McDowell, 1997) the forages recorded more than 10 times the levels of Ca.
Although the levels of P in forages had been found to fall within the required range, the
gross excess of Ca is likely to aggravate aphosphorosis in unsupplemented animals.
5. Conclusion
Forbs (herbaceous dicotyledonous plants) are important components of grassland
ecosystem of the semi-arid and dry sub-humid savannas of West Africa. In arable crop
systems, they are commonly referred to as `weeds'. Four legumes (Crotalaria
senegalensis, C. goreensis, Alysicarpus glumaceus, A. rugosus) and two non-legumes
(Cassia mimosoides and Ipomea eriocarpa) evaluated are potential useful forages for
inclusion in sown pasture production. The species are palatable with prospects for
extending the dry season supply of green forage. All species were found to sustain growth
and produce fresh fodder into the dry season when most of the associated grasses had
dried up. The six species appear quite promising for unimproved tropical forages in
contents of protein (up to 18% CP), energy (up to 58% DMD) and some mineral
elements. The calcium to phosphorus relations found need critical evaluation. For
integration into sown pasture systems, intensive studies are required to de®ne their
agronomic requirements, yield potentials and further evaluate feeding value parameters.
144
M.S. Kallah et al. / Animal Feed Science and Technology 84 (2000) 137±145
Acknowledgements
The authors are grateful to the Director, National Animal Production Research
Institute, Ahmadu Bello University, Shika-Zaria for permission to publish the work.
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