Directory UMM :Data Elmu:jurnal:A:Animal Feed Science and Technology:Vol85.Issue1-2.May2000:
Animal Feed Science and Technology
85 (2000) 89±98
Nutritive evaluation of some Acacia tree leaves
from Kenya
S.A. Abdulrazaka,b,*, T. Fujiharaa, J.K. Ondiekb, E.R. érskovc
a
Laboratory of Animal Science, Shimane University, Matsue-shi-690-8504, Shimane, Japan
b
Department of Animal Science, Egerton University, P.O. Box 536, Njoro, Kenya
c
Rowett Research Institute, Bucksburn Road, Aberdeen AB2 9SB, Scotland, UK
Received 16 August 1999; received in revised form 6 December 1999; accepted 3 March 2000
Abstract
A study was conducted to evaluate the nutritive potential value of six species of acacia tree
leaves: Acacia brevispica, nubica, tortilis, seyal, nilotica, and mellifera from Kenya. A wide
variability in chemical composition, polyphenolics and gas production and in situ dry matter (DM)
degradability was recorded. Crude protein (CP) content ranged from 134 to 213 g/kg DM. The
content of neutral detergent ®bre (NDF) and acid detergent ®bre (ADF) ranged from 154 to 308 and
from 114 to 251 g/kg DM, respectively, and was signi®cantly (p100 mg/g (pA. tortilis>A. mellifera>A. brevispica>A. seyal>A. nilotica. It is concluded that based on the
moderate to high CP values and the degradation characteristics, these species have potential as
livestock fodder. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Acacia; In situ degradability; Gas production; Nutritive value
*
Corresponding author. Tel.: 81-852-32-6584; fax: 81-852-32-6537.
E-mail address: abdul@life.shimane-u.ac.jp (S.A. Abdulrazak)
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 3 3 - 4
90
S.A. Abdulrazak et al. / Animal Feed Science and Technology 85 (2000) 89±98
1. Introduction
The use of browse species as fodder for ruminant is increasingly becoming important
in many parts of the tropics. Generally, tree fodder is richer in crude protein (CP),
minerals and digestible nutrients than grasses (Devendra, 1990; Topps, 1992). The use of
tree legume fodder as supplement has improved intake, digestibility and animal
performance (Norton, 1994; Abdulrazak et al., 1996). In Kenya, there is limited
information on the nutritive value of tree shrubs fed to livestock (Abdulrazak, 1995).
Moreover, studies on native tree species are limited than those of the introduced tree
species like Leucaena, Gliricidia, Calliandra and Sesbania. The recent infestation of
Leucaena leucocephala by the pest Heteropsylla cubana (Reynolds and Bimbuzi, 1993)
and the low palatability of Gliricidia sepium (Abdulrazak, 1995) suggests the importance
of screening other browses for further use in farming system. Acacia trees dominate in
many parts of the arid and semi arid areas of Sub-Saharan Africa, and have multiple uses.
They provide food, medicine, fodder aside from being resistant to diseases and the harsh
climatic conditions (Le Houerou, 1980). The presence of phenolic compounds in acacia
species has a negative affect on their nutritional value and also on their intake by
livestock (Degen et al., 1998). Tannins have been attributed to be one of the major causes
of their limited use as livestock fodder (Makkar, 1993). Generally, tannins in fodder tree
are known to have a negative effect on intake and digestibility (Kumar and D'Mello,
1995). Studies on some acacias have shown them to have either a positive (Ben Salem
et al., 1999) or a negative effect (Degen et al., 1998) on animal performance. This
variable effect could be attributed to the type of species, season and nutritive value. In
vitro gas production (Siaw et al., 1993; Khazaal and érskov, 1994) and in sacco rumen
degradability (Kibon and érskov, 1993; Apori et al., 1998) has been used to assess the
nutritive value of browse species. These rapid and less expensive methods have been used
to screen feed resources before making them available to livestock (Larbi et al., 1998).
The objective of this study was to assess the potential nutritive value of some selected
species of acacia from Kenya based on their chemical composition, polyphenolic
concentration, in vitro gas production and in sacco degradability.
2. Material and methods
2.1. Source of acacia samples
Leaves and petioles from six species of acacias, Acacia brevispica, nubica, tortilis,
seyal, nilotica and mellifera were harvested from Chemeron site, Egerton station in
Marigat area, Baringo district, Rift valley of Kenya. The area is located at an altitude
of 1066 m above sea level. The mean annual rainfall and temperature is 700 mm
and 24.08C, respectively. The selection of the tree species was based on herdsmen
knowledge of the tree forages preferred by small ruminants. Forages were harvested at
the end of rainy season from at least 12 individual trees or shrubs of each species, then
pooled and oven-dried at 608C for 48 h before being shipped to Matsue, Japan for later
analysis.
S.A. Abdulrazak et al. / Animal Feed Science and Technology 85 (2000) 89±98
91
2.2. Chemical analysis
Dry matter (DM), ash and nitrogen (N) content were measured according to (AOAC,
1990). Crude protein (CP) was calculated by multiplying N6.25. Neutral detergent ®bre
(NDF), acid detergent ®bre (ADF) and acid detergent lignin (ADL) were determined
according to Van Soest et al. (1991). Mineral concentration was determined by digesting
samples in HNO3/HClO4 and by using inductively coupled plasma spectroscopy (ICP) to
detect the elements Ca, Mg, P, S, Mn, Mo, Zn, Co, Cu and Fe (Varma, 1991). A
¯uorometric detection method using 2,3-diamononaphthalene derivative was used for the
determination of Se (Watkinson, 1966).
2.3. Phenolics compounds
The extraction of phenolics was done using 70% aqueous acetone. The tubes
containing samples were centrifuged at 48C for 20 min at about 2400 rpm and the
supernatant was stored for analysis. Total extractable phenols (TEPH) were determined
according to Julkunen-Titto (1985). A 0.05 ml aliquot and various amounts (0±0.1) of a
tannic acid (0.5 mg/ml; dissolving 25 mg tannic acid in 50 ml of distilled water) standard
solution was made up to 1.0 ml with distilled water. Then, 0.5 ml of Folin Ciocalteu
reagent (1 N) was added and all tubes which were subsequently vortexed, followed
by addition of 2.5 ml Na2CO3 (20%) and vortexing all the tubes again. After 35 min,
the absorbance at 725 nm was read using an UV-1200 Spectrophotometer. The
concentration of TEPH was calculated using the regression equation of the standard.
Total extractable tannins (TET) were estimated indirectly after being absorbed to
insoluble polyvinylypolyrrolidone (PVP). The mixture was then centrifuged at 2400 rpm
for 10 min and the supernatant was used to determine the total remaining phenols.
Concentration of TET was calculated by subtracting the TEPH remaining after PVP
treatment from TEPH. The total condensed tannins (TCT) were measured using the
method of Porter et al. (1986).
2.4. In situ degradability study
To determine the in sacco degradation characteristics of the samples, 4 g of dry sample
milled through a 2.5 mm screen was weighed in nylon bags (140 mm75 mm, pore size
40±60 um). The bags were incubated in the rumen of three cannulated sheep. The animals
were offered timothy hay ad libitum plus 200 g DM of concentrate twice a day at 08.00
and 17.00 h. Animals had free excess to water and mineral/vitamin licks. Nylon bags
were withdrawn at 4, 8, 16, 24, 48, 72 and 96 h after insertion. The 0 h measurement was
obtained by soaking the two bags of each sample in warm water (378C) for 1 h. The 0 h
and incubated bags were then washed with cold water for 15 min in a washing machine
and dried for 48 h at 608C. The DM degradation data were ®tted to the exponential
equation pab (1ÿeÿct) (érskov and McDonald, 1979; McDonald, 1981) to determine
the degradation characteristics (a, b, A, B, AB, c, ED); where p is the DM degradation at
time t, A denotes washing loss (representing the soluble fraction of the feed);
B(ab)ÿA; i.e. insoluble but fermentable fraction; c is the rate of degradation of B;
92
S.A. Abdulrazak et al. / Animal Feed Science and Technology 85 (2000) 89±98
a represents zero intercept; ED denotes effective degradability, calculated at an out¯ow
rate of 0.05 hÿ1.
2.5. In vitro gas production
Samples were incubated in vitro with rumen ¯uid in calibrated glass syringes following
the procedure of Menke and Steingass (1988). Rumen liquor was obtained from three
sheep fed on timothy hay and concentrate. Air-dried and ground (1.0 mm) samples of
about 2005 mg were weighed in duplicate into calibrated glass syringes of 100 ml. The
piston was then lubricated with pure oil to ease movement and to prevent escape of gas.
The syringes were pre-warmed (398C) for 1 h, before the addition of 301.0 ml of
rumen-buffer mixture into each syringe. The syringes were incubated in a water bath
maintained at 390.18C, and were gently shaken every hour during the ®rst 8 h of
incubation. Readings were recorded before incubation (0 h) and 3, 6, 12, 24, 48, 72 and
96 h after incubation. The mean gas volume readings were ®tted to the exponential
equation pab (1ÿeÿct) (érskov and McDonald, 1979), where p is the gas production
at time t; ab are the potential gas production and c denotes the rate of gas production.
2.6. Statistical analysis
Analysis of variance (ANOVA) was carried out on chemical composition, phenolics,
cell wall parameters, in sacco degradability and in vitro gas production with species as the
main factor using a general linear model (GLM) of Statistica for windows (Statistica,
1993). Signi®cance between means was tested using the least signi®cant difference
(LSD). A simple correlation analysis was used to establish the relationship between
polyphenolics concentration and in vitro gas production and DM degradability.
3. Results and discussion
The chemical composition of the acacia species is presented in Table 1. The CP ranged
from 134 to 213 g/kg DM and was lowest in A. seyal. The NDF and ADF content were
lowest in A. nubica and highest in A. nilotica. A. seyal had the highest lignin
concentration (121 g/kg DM) and A. nubica the lowest (51 g/kg DM). For all the samples
the ADF fraction was a large proportion of the NDF, which indicate high content of
cellulose and lignin and low levels of hemicellulose. The nitrogen bound to ®bre varied
between 164±335 and 86±250 g/kg N for NDF and ADF, respectively, with lower
concentration in A. nubica. The TEPH and TCT concentration ranged between 56±512
and 0.2±28.4 mg/g DM, respectively, and were lowest (p
85 (2000) 89±98
Nutritive evaluation of some Acacia tree leaves
from Kenya
S.A. Abdulrazaka,b,*, T. Fujiharaa, J.K. Ondiekb, E.R. érskovc
a
Laboratory of Animal Science, Shimane University, Matsue-shi-690-8504, Shimane, Japan
b
Department of Animal Science, Egerton University, P.O. Box 536, Njoro, Kenya
c
Rowett Research Institute, Bucksburn Road, Aberdeen AB2 9SB, Scotland, UK
Received 16 August 1999; received in revised form 6 December 1999; accepted 3 March 2000
Abstract
A study was conducted to evaluate the nutritive potential value of six species of acacia tree
leaves: Acacia brevispica, nubica, tortilis, seyal, nilotica, and mellifera from Kenya. A wide
variability in chemical composition, polyphenolics and gas production and in situ dry matter (DM)
degradability was recorded. Crude protein (CP) content ranged from 134 to 213 g/kg DM. The
content of neutral detergent ®bre (NDF) and acid detergent ®bre (ADF) ranged from 154 to 308 and
from 114 to 251 g/kg DM, respectively, and was signi®cantly (p100 mg/g (pA. tortilis>A. mellifera>A. brevispica>A. seyal>A. nilotica. It is concluded that based on the
moderate to high CP values and the degradation characteristics, these species have potential as
livestock fodder. # 2000 Elsevier Science B.V. All rights reserved.
Keywords: Acacia; In situ degradability; Gas production; Nutritive value
*
Corresponding author. Tel.: 81-852-32-6584; fax: 81-852-32-6537.
E-mail address: abdul@life.shimane-u.ac.jp (S.A. Abdulrazak)
0377-8401/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved.
PII: S 0 3 7 7 - 8 4 0 1 ( 0 0 ) 0 0 1 3 3 - 4
90
S.A. Abdulrazak et al. / Animal Feed Science and Technology 85 (2000) 89±98
1. Introduction
The use of browse species as fodder for ruminant is increasingly becoming important
in many parts of the tropics. Generally, tree fodder is richer in crude protein (CP),
minerals and digestible nutrients than grasses (Devendra, 1990; Topps, 1992). The use of
tree legume fodder as supplement has improved intake, digestibility and animal
performance (Norton, 1994; Abdulrazak et al., 1996). In Kenya, there is limited
information on the nutritive value of tree shrubs fed to livestock (Abdulrazak, 1995).
Moreover, studies on native tree species are limited than those of the introduced tree
species like Leucaena, Gliricidia, Calliandra and Sesbania. The recent infestation of
Leucaena leucocephala by the pest Heteropsylla cubana (Reynolds and Bimbuzi, 1993)
and the low palatability of Gliricidia sepium (Abdulrazak, 1995) suggests the importance
of screening other browses for further use in farming system. Acacia trees dominate in
many parts of the arid and semi arid areas of Sub-Saharan Africa, and have multiple uses.
They provide food, medicine, fodder aside from being resistant to diseases and the harsh
climatic conditions (Le Houerou, 1980). The presence of phenolic compounds in acacia
species has a negative affect on their nutritional value and also on their intake by
livestock (Degen et al., 1998). Tannins have been attributed to be one of the major causes
of their limited use as livestock fodder (Makkar, 1993). Generally, tannins in fodder tree
are known to have a negative effect on intake and digestibility (Kumar and D'Mello,
1995). Studies on some acacias have shown them to have either a positive (Ben Salem
et al., 1999) or a negative effect (Degen et al., 1998) on animal performance. This
variable effect could be attributed to the type of species, season and nutritive value. In
vitro gas production (Siaw et al., 1993; Khazaal and érskov, 1994) and in sacco rumen
degradability (Kibon and érskov, 1993; Apori et al., 1998) has been used to assess the
nutritive value of browse species. These rapid and less expensive methods have been used
to screen feed resources before making them available to livestock (Larbi et al., 1998).
The objective of this study was to assess the potential nutritive value of some selected
species of acacia from Kenya based on their chemical composition, polyphenolic
concentration, in vitro gas production and in sacco degradability.
2. Material and methods
2.1. Source of acacia samples
Leaves and petioles from six species of acacias, Acacia brevispica, nubica, tortilis,
seyal, nilotica and mellifera were harvested from Chemeron site, Egerton station in
Marigat area, Baringo district, Rift valley of Kenya. The area is located at an altitude
of 1066 m above sea level. The mean annual rainfall and temperature is 700 mm
and 24.08C, respectively. The selection of the tree species was based on herdsmen
knowledge of the tree forages preferred by small ruminants. Forages were harvested at
the end of rainy season from at least 12 individual trees or shrubs of each species, then
pooled and oven-dried at 608C for 48 h before being shipped to Matsue, Japan for later
analysis.
S.A. Abdulrazak et al. / Animal Feed Science and Technology 85 (2000) 89±98
91
2.2. Chemical analysis
Dry matter (DM), ash and nitrogen (N) content were measured according to (AOAC,
1990). Crude protein (CP) was calculated by multiplying N6.25. Neutral detergent ®bre
(NDF), acid detergent ®bre (ADF) and acid detergent lignin (ADL) were determined
according to Van Soest et al. (1991). Mineral concentration was determined by digesting
samples in HNO3/HClO4 and by using inductively coupled plasma spectroscopy (ICP) to
detect the elements Ca, Mg, P, S, Mn, Mo, Zn, Co, Cu and Fe (Varma, 1991). A
¯uorometric detection method using 2,3-diamononaphthalene derivative was used for the
determination of Se (Watkinson, 1966).
2.3. Phenolics compounds
The extraction of phenolics was done using 70% aqueous acetone. The tubes
containing samples were centrifuged at 48C for 20 min at about 2400 rpm and the
supernatant was stored for analysis. Total extractable phenols (TEPH) were determined
according to Julkunen-Titto (1985). A 0.05 ml aliquot and various amounts (0±0.1) of a
tannic acid (0.5 mg/ml; dissolving 25 mg tannic acid in 50 ml of distilled water) standard
solution was made up to 1.0 ml with distilled water. Then, 0.5 ml of Folin Ciocalteu
reagent (1 N) was added and all tubes which were subsequently vortexed, followed
by addition of 2.5 ml Na2CO3 (20%) and vortexing all the tubes again. After 35 min,
the absorbance at 725 nm was read using an UV-1200 Spectrophotometer. The
concentration of TEPH was calculated using the regression equation of the standard.
Total extractable tannins (TET) were estimated indirectly after being absorbed to
insoluble polyvinylypolyrrolidone (PVP). The mixture was then centrifuged at 2400 rpm
for 10 min and the supernatant was used to determine the total remaining phenols.
Concentration of TET was calculated by subtracting the TEPH remaining after PVP
treatment from TEPH. The total condensed tannins (TCT) were measured using the
method of Porter et al. (1986).
2.4. In situ degradability study
To determine the in sacco degradation characteristics of the samples, 4 g of dry sample
milled through a 2.5 mm screen was weighed in nylon bags (140 mm75 mm, pore size
40±60 um). The bags were incubated in the rumen of three cannulated sheep. The animals
were offered timothy hay ad libitum plus 200 g DM of concentrate twice a day at 08.00
and 17.00 h. Animals had free excess to water and mineral/vitamin licks. Nylon bags
were withdrawn at 4, 8, 16, 24, 48, 72 and 96 h after insertion. The 0 h measurement was
obtained by soaking the two bags of each sample in warm water (378C) for 1 h. The 0 h
and incubated bags were then washed with cold water for 15 min in a washing machine
and dried for 48 h at 608C. The DM degradation data were ®tted to the exponential
equation pab (1ÿeÿct) (érskov and McDonald, 1979; McDonald, 1981) to determine
the degradation characteristics (a, b, A, B, AB, c, ED); where p is the DM degradation at
time t, A denotes washing loss (representing the soluble fraction of the feed);
B(ab)ÿA; i.e. insoluble but fermentable fraction; c is the rate of degradation of B;
92
S.A. Abdulrazak et al. / Animal Feed Science and Technology 85 (2000) 89±98
a represents zero intercept; ED denotes effective degradability, calculated at an out¯ow
rate of 0.05 hÿ1.
2.5. In vitro gas production
Samples were incubated in vitro with rumen ¯uid in calibrated glass syringes following
the procedure of Menke and Steingass (1988). Rumen liquor was obtained from three
sheep fed on timothy hay and concentrate. Air-dried and ground (1.0 mm) samples of
about 2005 mg were weighed in duplicate into calibrated glass syringes of 100 ml. The
piston was then lubricated with pure oil to ease movement and to prevent escape of gas.
The syringes were pre-warmed (398C) for 1 h, before the addition of 301.0 ml of
rumen-buffer mixture into each syringe. The syringes were incubated in a water bath
maintained at 390.18C, and were gently shaken every hour during the ®rst 8 h of
incubation. Readings were recorded before incubation (0 h) and 3, 6, 12, 24, 48, 72 and
96 h after incubation. The mean gas volume readings were ®tted to the exponential
equation pab (1ÿeÿct) (érskov and McDonald, 1979), where p is the gas production
at time t; ab are the potential gas production and c denotes the rate of gas production.
2.6. Statistical analysis
Analysis of variance (ANOVA) was carried out on chemical composition, phenolics,
cell wall parameters, in sacco degradability and in vitro gas production with species as the
main factor using a general linear model (GLM) of Statistica for windows (Statistica,
1993). Signi®cance between means was tested using the least signi®cant difference
(LSD). A simple correlation analysis was used to establish the relationship between
polyphenolics concentration and in vitro gas production and DM degradability.
3. Results and discussion
The chemical composition of the acacia species is presented in Table 1. The CP ranged
from 134 to 213 g/kg DM and was lowest in A. seyal. The NDF and ADF content were
lowest in A. nubica and highest in A. nilotica. A. seyal had the highest lignin
concentration (121 g/kg DM) and A. nubica the lowest (51 g/kg DM). For all the samples
the ADF fraction was a large proportion of the NDF, which indicate high content of
cellulose and lignin and low levels of hemicellulose. The nitrogen bound to ®bre varied
between 164±335 and 86±250 g/kg N for NDF and ADF, respectively, with lower
concentration in A. nubica. The TEPH and TCT concentration ranged between 56±512
and 0.2±28.4 mg/g DM, respectively, and were lowest (p