Seasonal dynamics in dry matter degradation of browse in cattle, sheep and goats

ELSEVIER

Small Ruminant

Research 25 (1997) 129-140

Seasonal dynamics in dry matter degradation of browse in cattle, sheep and goats A. Larbi a**, J.W. Smith a, A.M. Raji b, 1.0. Kurdi a, 1.0. Adekunle a, D-0. Ladipo ’ a International Livestock Research Institute (ILRI), Humid/S u bl lumid Zone Programme, Ibadan, Nigeria b lmtitute oJ’Agriculturu1 Research and Training (LAR & T), Ibadan, Nigeria ’ ICRAF-OSU / IOTA Multipurpose Tree Project, IITA, Ibadan, Nigeria Accepted 20 September

1996

Abstract Rumen degradation characteristics of DM in edible forage of 25 multipurpose tree and shrub fodders (MPTS) harvested at the end of the main-wet (April-August 1992), minor-wet (September-November 1992) and dry (December 1992-March 1993) seasons were determined in rumen-fistulated Bunaji cattle (BC), West African Dwarf (WAD) sheep (WS) and WAD goats (WC) in Ibadan, southwestern Nigeria. Air dry samples of edible forage were incubated for 3, 6, 12, 36, 48, 72 and 96 h in three each of BC, WS and WC castrates fed a basal diet of Panicum maximum supplemented with Gliricidia sepium leaves. Dry matter degradation constants were estimated from non-linear regression. Concentrations of crude protein, neutral detergent fibre and insoluble proanthocyanidins varied widely among seasons. Classification of the MPTS based on a (soluble fraction), b (rumen degradable fraction), c (rate of degradation)) and PD (potential degradation) varied among BC, WS and WG within season. Using PD as an index of forage quality, the MPTS were classified into high, medium and low groups. The b and PD in BC during the dry season were significantly higher than in WS and WG. The results suggested the existence of intraspecies and interspecies variation in rumen degradation characteristics of DM of the MPTS in BC, WS and WG. The PD in BC was highly correlated to WS and WG in the wet seasons. Thus, rumen degradation could be useful in the initial screening of MPTS for further nutritional studies. 0 1997 Elsevier Science B.V. Keywork:

Season; Ruminant

species; Fodder trees and shrubs; Rumen degradation;

1. Introduction The majority of smallholder farmers in subSaharan Africa keep mixed ruminant species. Seasonal fluctuations in quantity and quality of feed are major constraints to livestock production in such

* Corresponding author at: IITA-CIAT, P.O. Box 025443, Miami, FL 33302, USA. Fax: 44-181-681-8583; E-mail: [email protected]

Gas production;

Chemical

composition

systems (Winrock, 1992). Multipurpose tree and shrub fodders (MPTS) are important feed resources for bridging the seasona deficits in feed quantity and quality (Topps, 1992). However, there is a paucity of information on the seasonal effects on comparative digestibility of browse in cattle, sheep and goats (Brown and Johnson, 1984; Migongo-Bake, 1992; Tolkamp and Brouwer, 1993). Rumen degradation is a major determinant of forage quality (Orskov and McDonald, 1979). It is useful for ranking MPTS in terms of nutritive value

00921.4488/97/$17.00 0 1997 Elsevier Science B.V. All rights reserved. PII SO921 -4488(96)0097 l-6

130

A. Lurbi et ul./Smull Ruminunr Research 25 (1997) 129-140

(Siaw et al., 1993; Larbi et al., 1994) and for comparing the digestive capacities of ruminant species (Migongo-Bake, 1992). Several MPTS are currently being evaluated for development of crop-livestock agroforestry technologies in the West and Central African lowland tropics by the International Centre for Research in Agroforestry (ICRAP) in collaboration with the International Institute for Tropical Agriculture (IITA) and Oregon State University. The objectives of the present study were to estimate seasonal effects on in sacco degradation characteristics of dry matter (DM) in edible forage of some of the promising MPTS when incubated in the rumens of Bunaji cattle (BC), West African Dwarf (WAD) sheep (WS) and WAD goats (WG), and determine the effects of season on the relationship between the extent of DM degradation in BC, WS and WG.

Table I CP, NDF and insoluble proanthocyanidins season in Ibadan, southwestern Nigeria

2. Materials and methods

2.1. site The study was conducted at the International Livestock Research Institute (ILRI) research site located at the IITA Headquarters in Ibadan, southwestem Nigeria (7”30’N; 3”54’E). The site has a subhumid climate with total annual rainfall of 1250 mm. There are three seasons, namely: main-wet (April to August), minor-wet (September to November), and dry (December to March) based on the total rainfall and rainy days. Total rainfall amounts during the main-wet, minor-wet, and dry seasons during the study period were 642.5 mm, 418.5 mm and 55.4 mm, respectively.

(PTCs) contents of 25 multipurpose

Species

Subfamily

CP(g kg-

A. Acacia ungustissima B. Afieliu bellu C. Albizia lebbeck (NFTA 864) D. Albiziu lebbeck (Ibadan) E. Albizia proceru F. Albiziu suman G. Culliandru cabthyrsus (NFTA 896) H. Culliundra culothyrsus (ILCA 1498 I ) I. Calliundru culothyrsus (ILCA I5 166) J. Calliarzdruculothyrsus (ILCA 16301) K. Cussiu nodosu L. Cassia s&mea M. Cussia spectabilis N. Dactyledaniu burterii 0. Erythrinu poeppigiunu P. Gliricida sepium Q. Leucaena leucocephulu R. Lonchocurpus sericeus S. Milletiu rhonningii T. Newbouldiu laeois U. Paraseriunfhes falcuturia V. Parkia biglobosa W. Peltophorum pterocurpum X. Ptervcarpus santulinoides Y. Tetrapleura tetarpteru Mean Minimum Maximum

Mimosoideae Caesalpinioideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Caesalpinioideae Caesalpinioideae Caesalpinioideae Chrysobalanaceae Papilionoideae Papilionoideae Mimosoideae Papilionoideae Papilionoideae Bignonuaceae Mimosoideae Mimosoideae Caesalpinoideae Papilionoideae Mimosoideae

226 251 244 180 280 276 233 256 271 243 136 210 216 123 232 254 266 206 177 216 261 258 136 219 251 220 123 280

tree and shrub fodders during the main-wet,

’ DM)

ND&I 703 469 549 697 411 449 413 553 578 645 694 488 485 576 418 381 534 551 614 480 504 555 694 587 469 544 381 703

kg -

’ DM)

(April-August)

PTCs(500 nm g85.3 7.9 2.8 5.9 25.3 1.7 137.6 28.8 8.7 33.3 43.9 5.3 26.5 223.9 48.7 31.9 49.7 14.1 51.8 6.3 26.9 3.5 43.9 6.2 7.9 45.8 1.7 223.9

’ NDF)

A. Larbi et al. /Small Ruminant Research 25 (1997) 129-140

131

2.2. Forages

2.3. In sacco dry matter degradation

Forages from 25 MPTS listed in Table 1 were used. The MPTS were selected on the basis of evaluations in earlier agronomic trials and their use in smallholder crop-livestock agroforestry systems in the tropics (Brewbaker, 1989). Samples of edible forage (leaf + stem < 6 mm diameter) were collected randomly at the end of the main-wet (April-August 1992), minor-wet (September-November 19921, and dry (December 1992-March 1993) seasons and airdried. Half of the air-dried samples was ground in a Wiley mill to pass a l-mm screen for chemical analysis. The other half was ground through a 2.5-mm screen for determination of rumen degradation characteristics in sacco.

The nylon bag technique (Mehrez and Orskov, 1977) was used in three each of rumen-fistulated BC, WS and WG castrates housed in individual pens. The animals were offered a basal diet of Panicum maximum supplemented with fresh leaves of Gliricidia sepium. The feed was offered at a daily forage DM allowance of 50 g kg-’ liveweight, of which 30% was fed as supplement. Animals were fed twice a day at 08:OO and 16:00 h, and had free access to water and mineral licks. About 5 g of DM were weighed into nylon bags of size 5 cm X 18 cm made of polyamide (Polymon, Switzerland) with a pore size of 41 pm. The bags were incubated in duplicate in the rumen of each

Table 2 CP, NDF and insoluble proanthocyanidins (PTCs) contents tober) season in Ibadan, southwestern Nioeria

of 25 multipurpose

Species

Subfamily

CPfS kg-

A. Acacia angustissima B. Afzelia bellu C. Albizia lebbeck (NFTA 864) D. Albizia lebbeck (Ibadan) E. Albizia procera F. Albiria saman G. Calliundra cullothyrsus (NITA 896) H. Culliandra callothyrsus (ILCA 1498 1) I. Calliundru cullothyrsus (ILCA 15 166) J. Calliatulra cullothyrsus (ILCA 16301) K. Cassiu nodosa L. Cussia siameu M. Cassia spectabilis N. Dactyledaniu burterii 0. Erythrina poeppigiunu P. Gliricida sepium Q. Leucaena leucocephda R. Lonchocurpus sericeus S. Milletiu thonningii T. Newbouldia laevis U. Puraserianthes jdcataria V. Parkiu biglobosa W. Peitophorum pterocarpum X. Pterocurpus santulinoides Y. Tetrapleura tetarpteru Mean Minimum Maximum

Mimosoideae Caesalpinioideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Caesalpinioideae Caesalpinioideae Caesalpinioideae Chrysobalanaceae Papilionoideae Papilionoideae Mimosoideae Papilionoideae Papilionoideae Bignonuaceae Mimosoideae Mimosoideae Caesalpinoideae Papilioniodeae Mimosoideae

187 224 218 169 241 278 174 275 225 217 107 175 15.5 103 234 222 229 192 167 149 214 260 107 204 224 193 103 278

tree and shrub fodders during minor-wet

’ DM)

(September-(X-

NDF(g kg - ’ DM)

PTCs(500 nm g-

606 425 394 639 298 435 350 315 418 431 568 412 358 555 447 425 384 559 167 444 387 441 568 545 425 445 167 639

354.6 14.8 64.1 14.5 93.4 7.2 112.3 19.4 59.2 48.5 38.3 8.4 41.7 173.9 6.8 79.3 76.3 18.4 54.7 10.6 45.2 9.1 38.3 14.1 14.6 63.1 6.8 354.6

’ NDF)

132

A. Larbi et al./Small Ruminant Research 25 (1997) 129-140

animal for 3, 6, 12, 48, 72 and 96 h. After incubation, bags were washed under running cold tap water until the rinse water was clear, and dried at 60°C for 48 h. Zero-time (washing losses) were estimated by soaking two bags per sample in warm tap water at 37°C for 1 h followed by washing and drying. Dry matter degradation constants were estimated from the non-linear equation proposed by Orskov and McDonald (1979): PD = a + b(l e- ‘I), where a is the soluble fraction of DM, b is the rumen degradable fraction, c is the rate of degradation of b at time t, and PD is the potential degradation.

ysed according to Goering and Van Soest (1970). Insoluble proanthocyanidins (PTCs) were determined by the method of Reed et al. (1982) and Reed et al. (1986). 2.5. Statistical analysis Data were analysed separately for each season using the Statistical Analysis Systems Institute Inc. package @AS Institute Inc., 1988). Effects included in the model were MPTS, ruminant species and the MPTS by ruminant species interaction. Cluster analysis was used to classify the MPTS. The classification was done on standardized values of a, b, c, PD using the average linkage method in the hierarchial clustering procedure. Univariate regression analysis was used to establish relationships between PD in BC, WS, and WG within season.

2.4. Analytical procedures Total N was determined by the Kjeldahl method (AOAC, 1990). Crude protein (CP) was calculated as N X 6.25. Neutral detergent fibre (NDF), was anal-

Table 3 CP, NDF and insoluble proanthocyanidins season in Ibadan, southwestern Nigeria

(PTCs) contents

of 25 multipurpose

Species

Subfamily

CP(g kg-

A. Acacia angustissima B. Afzelia bellu C. Albiziu Zebbeck (NFTA 864) D. Albizia lebbeck (Ibadan) E. Albizia procera F. Albizia saman G. Calliandra callothyrsus (NFTA 896) H. Culliundru callothyrsus (ILCA 14981) I. Calliandra callothyrsus (ILCA 15 166) J. Calliandra caflothyrsus (ILCA 16301) K. Cassia nodosa L. Cassia siamea M. Cassia spectubilis N. Dactyledania barterii 0. Erythrinu poeppigiana P. Gliricida sepium Q. Leucuena ieucocephala R. Lonchocarpus sericeus S. Milletiu thonningii T. Newbouldia laevis U. Paraserianthes falcataria V. Parkia biglobosa W. Peltophorum pterocarpum X. Pterocarpus santalinoides Y. Tetrapleura tetarptera Mean Minimum Maximum

Mimosoideae Caesalpinioideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Mimosoideae Caesalpinioideae Caesalpinioideae Caesalpinioideae Chrysobalanaceae Papilionoideae Papilionoideae Mimosoideae Papilionoideae Papilionoideae Bignonuaceae Mimosoideae Mimosoideae Caesalpinoideae Papilionoideae Mimosoideae

147 205 282 162 260 229 211 292 263 236 100 212 145 112 221 253 235 182 148 128 199 256 101 214 205 196 100 292

tree and shrub fodders during the dry (December-March)

’ DM)

NDF(g kg593 376 549 561 417 448 439 553 615 506 483 338 371 508 418 380 571 510 463 408 504 359 484 594 376 477 338 625

’ DM)

PTCs(500 nm g151.9 10.4 39.6 6.7 25.1 4.6 26.6 15.4 38.8 7.3 12.6 5.4 17.7 147.4 5.1 5.6 37.7 11.4 31.8 6.2 17.7 5.8 12.6 6.8 10.3 31.9 4.6 151.9

’ NDF)

A. Larbi et al./Small Ruminant Research 25 (1997) 129-140

3. Results

3.1. Chemical composition There were notable differences in the seasonal concentrations of CP, NDF and PTCs among the MPTS (Tables 1-3). In the main-wet season, CP ranged from 123 g kg-’ DM in Dactyledania barterii to 280 g kg-’ DM in Albizia procera, NDF from 381 g kg-’ DM in G. sepium to 703 g kg-’ DM in Acacia angustissima, and PTCs from 1.7 g- ’ (a)

CATTLE

(b)

SHEEP

133

NDF in Albizia saman to 223.9 g-’ NDF in D. barterii (Table 1). Crude protein concentration ranged from 103 g kg-’ DM in D. barterii to 278 g kg-’ DM in Albizia saman, NDF from 167 g kg-’ DM in Mifletia thonningii to 639 g kg-’ DM in the indigenous Albizia lebbeck, and PTCs from 6.8 in Erythrina poeppigiana to 354.6 in Acacia angustissima, in the minor season (Table 2). In the dry season, CP ranged from 100 g kg-’ DM in Cassia nodosa to 292 g kg-’ DM in Calliandra calothyrsus (ILCA, 14981), NDF from 338 g kg-’ DM in Cassia siamea

”

PFBMDLKOCSTXUQYAI

(c) 4 :::

WGNRI

AE

V

GOATS

[

PUCOXYHRSTEVABMDLQKIWONPI

Browse Fig. 1. Hierarchy for the classification of multipurpose Dwarf (WAD) sheep (b) and WAD goats (c).

species

tree and shrub fodders during the main-wet

season in Bunaji cattle (a), West African

A. Larbi et al./Small

134

Ruminanr Research 25 (1997) 129-140

to 615 g kg-’ DM in Calliandra calothyrsus (ZLCA, 15166), and PTCs from 4.6 g- ’ NDF in Albizia saman to 15 1.9 g- ’ NDF in Acacia anguistissima (Table 3). 3.2. In sacco degradation

varied among BC, WS and WG. The dendrograms suggest interspecies and intraspecies variation in rumen degradation characteristics in BC, WS and WG. This variation is partly demonstrated in provenances of Albizia lebbeck and Calliandra calothyrsus, and species of Albizia and Cassia.

Figs. l-3 show the results of the application of cluster analysis to the data matrix. Within season, classification of the MPTS based on a, b, c and PD

3.2.1. MPTS with high PD Classification of the MPTS into high, medium and low forage quality groups based on PD as an

(a) CAlTLJZ

P

1

EVSTYQKUOXPCAJORWHNDLBM

(b)

SHEEP

(c) GOATS 1.60 J “I c :.@I h 0.80 i o.60

Browse species Fig.2. Hierarchy for the classification of multipurpose tree and shrub fodders during the minor-wet season in Bunaji cattle (a), West African Dwarf (WAD) sheep (b) and WAD goats cc).

A. Lurbi et al./Smdl

Ruminant Research 25 (1997) 129-140

135

(a) CATTLE 1.60 $

1.40

.J

1.20

$

1.w

i

ct.80

;1

cl.60

I I

0.40

3B

0.20

i:

0

I

N

1

HGFCUOQKMXARSTELYDPBVW

(b) SHEEP 1.60 i

I4 1.20

I s

1.w

i

o.Bo

.:

i

oAo 0.60

2

0.20

2

0 FUQYKTEDLBPMCOXIGIHAWVSNR

(c)

GOATS

PMPUCIH

I

G

LADEBVR

WNSTXK

Browse species Fig. 3. Hierarchy for the classification of multipurpose (WAD) sheep (b) and WAD goats (cl.

tree and shrub fodders during the dry season in Bunaji cattle (a), West African Dwarf

index of forage quality in BC, WS and WG is presented in Table 4. Of the 25 MPTS, five ( Afzelia bella, Albizia lebbeck NFTA 864, Cassia siamea, Cassia spectabilis, G. sepium) were high PD in all ruminant species during the wet seasons. In the dry season, 13 MPT ( Afzelia bella, Albizia lebbeck NFTA 864, local Albizia lebbeck, Albizia saman, Calliandra calothyrsus provenances N 896, ILCA 1498 1, ILCA 15166, ILCA 16301, Cussia nodosa,

Cassia siamea, G. sepium, Leucaena leucocephala, Tetrapleura tetraptera) in BC, five (Acacia anguistissima, Afzelia bella, Albizia procera, Cassia spectabilis and G. septum) in WS, and eight (local Albizia lebbeck, Albizia procera, Calliandra calothyrsus NFTA 896, ILCA 14981, 16301, Cassia siamea, Cassia spectabilis, G. sepium, Leucaena leucocephala, T. tetraptera) in WG were classified as having high PD.

136

A. Lnrbi et al. /Small

Ruminant Research 25 (1997) 129-140

Table 4 Seasonal groupings of browse species listed in Table 1 based on potential degradability (PD, g kg-’ DM) in Bunaji cattle, West African Dwarf (WAD) sheep and WAD goats Season a

Ruminant

Group b High

Medium

Main-wet

Cattle

B,D,L,

CF.

A,E,G,H,I,J,K,N,

Q.Y

O,R,S,TJJ,V,W,X

Sheep

MI B,D,L

WK.

AEG,H,I,J,N

M,P

Q,S,T,

O,R,UV,W,X,Y

B,D,L, M,E

C,F,H,

A,E,G,I,J,K,N,G,

QST

RS,U,V,W,X,Y

WX BJXL, M,P J%D,L, M,P

WX, Q,T,Y WK QS,T C,F,H,K QS,T,Y

OR,S,U,V,W,X A,E,G,H,I,J,N, O,R,Y,v,W,x AEG,l,J,N, Q,JUJ,v,w,x

B,C,D,F,G H,I,J,K,L

A,E,M,O S,T,U,X

N,R,V,W

C,D,F,G H,I,K,L

J,N,O,R,S V,W,X

Goats

Minor-wet

Cattle

M,E Sheep Goats

Dry

Cattle

Sheep

P,Q.Y A&E, M,P

Goats

Low

A,E,G,H,I,J,N,

Q,T,UY DEG,H,J, A,C,F, J%KN,O,R, L,M,P,Q,Y 1,U S,T,v,w,X

a Season: main-wet, April-August 1992; minor-wet, SeptemberNovember 1992; dry, December I992-March 1993. b Grouping based on PD (g kg-’ DM) estimated from the equation: PD = a+ b(l e - “J. High, > 700; medium, 500-600; low, < 500.

3.2.2. MPTS with medium PD In the wet seasons, Albizia lebbeck NFTA 864, Albizia saman and Leucaena leucocephala were of medium quality in all the ruminant species, whilst Newbouldia laevis had medium PD in WS and WG. Calliandra calothyrsus ILCA 14981 had medium PD in WG (Table 4). Milletia thonningii had medium quality in WS during the main-wet season, and WS and WG during the minor-wet season. Tetrapleura tetraptera had medium quality in BC during the main-wet season, and in BC and WS during the minor-wet season. In the dry season, only Paraserianthes falcataria had medium PD in all ruminant species. Newbouldia laevis and T. tetraptera had medium PD in BC and WS, Acacia angustissima in BC and WG. Albizia lebbeck (NFTA 864), Albizia

saman and Calliandra calothyrsus ILCA 15 166 had medium PD in WS and WG. 3.2.3. MPTS with low PD Six MPTS namely, D. barterii, Lonchocarpus sericeous, Parkia biglobosa, Peltophorum pterocarpum, Pterocarpus santalinoides and T. tetraptera had low PD in BC, WS and WG in all seasons (Table 4). Acacia angustissima, Albizia procera, Calliandra calothyrsus provenances NFTA 896, ILCA 15 166, 16301, E. poeppigiana and Paraserianthes falcataria had low PD in all the ruminant species in the wet seasons. In the dry season, E. poeppigiana and M. thonningii had low PD in WS and WG, Afzelia bella and Cassia nodosa in WG, and Calliandra calothyrsus ILCA 16301 in WS. 3.3. Season and ruminant species interaction effects on 6, c and PD The b and PD did not differ significantly among BC, WS and WG in the wet seasons (Table 5).

Table 5 Seasonal effects on dry matter degradation constants of 25 browses species in Bunaji cattle, West African Dwarf (WAD) sheep and WAD goats Season

’

Degradation

constants

’

b

c

PD

Main-wet

Cattle Sheep Goats SEM

304 p 303 a 323 a 18.6

0.0471 b 0.0672 a 0.0489 b 0.00689

521a 519* 540 a 24.0

Minor-wet

Cattle Sheep Goats SEM

323 = 320 a 344 a 19.2

0.0586 b 0.0733 a 0.0433 c 0.00704

539 a 537 a 561 a 24.5

Dry

Cattle Sheep Goats SEM

520 a 425 b 436 b 23.1

0.0279 b 0.0293 b 0.035 1 = 0.0025 1

719 a 624 b 635 b 23.9

’ Estimates from the equation: PD = a + b(f e- ‘I). b, slowly degradable fraction; PD. potential degradability (g kg- ’ DM); c, fractional rate of degradation (h- ’ ). ’ Season: main-wet, April-August 1992; minor-wet, SeptemberNovember 1992; dry, December 1992-March 1993. Means in a column with the same superscripts do not differ, * P > 0.05.

A. Lurbi et ul./Smull

137

Rurninunt Rcseurch 25 (1997) 129-140

a’ 1Cattle 70

-

60

-

l

Sheep 70

30

20

80

90

goICattle

80

80

-

70

70

-

60

60

-

40

60

50

70

80

b-3

50

40

I

3c k

I

/

7.c b. 2c

,

)

30

Sheep 40

50

60

70

80

90

20

30

40

50

Fig. 4. The relationship between potential degradation of dry matter in Bunaji cattle, West African during the main wet (a, b) and minor-wet (c, d) seasons.

However, in the main-wet season, the c in WS was higher than BC and WG. In the dry significantly season, the b and PD of BC were significantly higher than WS and WG, whilst the c of WS was significantly higher than BC and WG. 3.4. Relationships between PD in BC, WS and WG The PD in BC was highly correlated to PD in WS and WG during wet seasons (Fig. 4). However, the PD in BC was poorly correlated to that of WS (r = 0.35, P > 0.412) and WG (r = 0.38, P > 0.281) during the dry season.

80

70

80

90

Dwarf (WAD) sheep and WAD goats

4. Discussions

The ranges of CP, NDF and PTCs were comparable to earlier reports for several browse species in the tropics (Le Houerou, 1980; Onwuka et al., 1989; Rittner and Reed, 1992; Topps, 1992; Nsahlai et al., 1994). Seasonal variations in these constituents probably occurred as a result of differences in length of season and environmental conditions such as rainfall, temperature and relative humidity (Akkasaeng et al., 1989). Seasonal variations in CP, NDF, and PTCs in the MPTS may be partly attributed to differences in leaf to stem ratio and duration of cell-wall elabora-

138

A. Larbi

et al./Smull

Ruminant

tion and/or accumulation of toxic or secondary compounds in the latter (Mould and Robbins, 1981). All the MPTS had CP levels greater than 80 g kg-’ DM, the level below which voluntary intake of tropical forages is limited (Minson, 1980). The relatively higher CP levels of the MPTS during the dry season suggest that they could effectively provide supplemental N when browsed with native pasture or when offered to stall-fed animals on low N cereal crop residue diets. However, the availability of the CP may depend on the concentrations of antinutritive factors such as PTCs (Arthun et al., 1992; Broderick, 1995). The cluster analyses identified cluster groups of species, suggesting interspecies and intraspecies variation in rumen DM degradation characteristics in BC, WS and WG within season. Similarly, other workers (Kibon and Orskov, 1993; Siaw et al., 1993; Larbi et al., 1994) have reported interspecies and intraspecies variation in DM degradation characteristics of browse. The wide variation in PD reported in the present study confirmed earlier reports (Kamatali et al., 1992; Siaw et al., 1993). It is evident from Tables l-3 that the variations in rumen degradation characteristics could not be solely attributed to the differences in CP, NDF, and PTCs. Thus other factors must be implicated as, for instance, the configuration of cell-wall polysaccharides and their effect on rumen microbial attachment and colonization of digesta particles (Cheng et al., 1984). Using the average PD of DM reported in the present study as an index of forage quality, some MPTS, e.g. Afzelia bella, Albizia lebbeck NFTA 864, Cassia siamea, Cassia spectabilis, G. sepium, appeared to be of higher quality than others, e.g. D. barterii, Lonchocarpus sericeus, Parkia biglobosa, Peltophorum pterocarpum, Pterocarpus santalinoides and T. tetraptera. Further studies are needed to determine whether the higher PD of DM could be translated into animal output which is a better determinant of forage quality, especially under subSaharan Africa feeding systems where nitrogen available at the rumen level is not optimal. The b and PD did not differ significantly among BC, WS and WG in the wet seasons (Table 5). Wilson (1977) found no significant differences between the digestibility of leaves of trees and shrubs by sheep and goats. Larbi et al. (1993) found no

Research

25 (1997)

129-140

differences between sheep and goats in in vivo DMD when offered wilted leaves of Erythyrina abyssinica. However, in the dry season, PD of BC were significantly higher than WS and WG, partly as a reflection of the relatively higher b in BC than WS and WG. Aerts et al. (1985) concluded from 82 comparative digestion trials that organic matter in grass hay was better digested by cows than sheep. Blankenship et al. (1982) reported significant variation in in vitro DM digestibility among cattle, sheep and goats in Texas. In a statistical review of digestion in goats compared with other ruminants, Tolkamp and Brouwer (1993) concluded that overall feed digestibility was lower in goats compared to cattle and that the difference tends to be larger in low protein diets. The relatively higher PD for BC in this study partly suggests that BC may be more efficient in digesting dry season edible forage of some MPTS than WS and WG. Therefore, keeping mixed ruminant species should provide effective utilization of diverse MPTS in smallholder farming systems. The PD in BC was highly correlated to WS or WG during wet seasons (Fig. 4). This observation suggests that WS and WG were reliable in predicting the PD of MPTS for BC. Several authors (Aerts et al., 1985; Tolkamp and Brouwer, 1993) have suggested good agreement in the digestive capacity of cattle, sheep and goats. We cannot explain the poor correlation between the PD of BC, WS and WG during the dry season.

5. Conclusion Rumen degradation characteristics of DM in BC, WS, and WG vary within and among species of MPTS from season to season. Rumen degradation characteristics could be used to characterize and detect variation in forage quality in MPTS. Based on PD, groups of MPTS were identified which could be useful in selection of materials for further nutritional studies. For example, Afzelia bella, Albizia lebbeck (Ibadan), Cassia siamea, Cassia spectabilis and G. sepium were of high quality in BC, WS and WG in both wet and dry seasons, while Calliandra calothyrsus provenances, Albizia procera, Leucaena leucocephala and T. tetraptera were of high quality in BC and WG only during the dry season. The study has

A. Larbi

et ul./Smull

Ruminant

also given some indication of the variability in rumen degradation characteristics existing between and within the MPTS currently being evaluated for agroforestry technologies in the tropics.

Acknowledgements The authors wish to express their gratitude to the staff of ILRI Humid Zone Programme, Ibadan Nigeria, and the Nutrition Laboratory, Addis Ababa, Ethiopia for their invaluable assistance.

References Aerts, J.W., de Boever, J.L., Cottyn, B.G., de Brabande, D.L. and Buyse, F.X., 1985. Comparative digestibility of feedstuffs by sheep and cows. Anim. Feed Sci. Technol., 12: 47-56. Akkasaeng, R., Gutteridge, R.C. and Wanapat, M., 1989. Evaluation of trees and shrubs for forage and fuelwood in north east Thailand. Inter. Tree Crops J., 5: 209-220. Arthun, D., Holeckek, J.L., Wallace, J.D., Galyean, M.L., Cardenas, M. and Ratique, S., 1992. Forb and shrub influences on steer nitrogen retention. J. Range Manage., 45: l33- 135. AOAC, 1990. Official Methods of Analysis. 15th edn., Association of Official Analytical Chemists, Washington, DC, USA, pp. 69-88. Blankenship, L.H., Vamer, L.W. and Lynch, G.W., 1982. In uitro digestibility of south Texas range plants using inoculum from four ruminant species. J. Range Manage., 35: 664-666. Brewbaker, J.I., 1989. Nitrogen fixing trees for fodder and browse in Africa. In: B.T. Kang and L. Reynolds (Editors), Alley Farming in the Humid and Subhumid Tropics. IDRC, Ottawa, Canada, pp. 55-61. Broderick, G.A., 1995. Desirable characteristics of forage legumes for improving protein utilization in ruminants. J. Anim. Sci., 73: 2760-2773. Brown, L.E. and Johnson, W.L., 1984. Comparative intake and digestibility of forages and byproducts by goats and sheep: a review. Int. Goat Sheep Res., 2: 212-226. Cheng, K.J., Stewart, C.S., Dinsdale, D. and Costerton, J.W., 1984. Electron bacteria involved in the digestion of plant cell walls. Anim. Feed Sci Technol., 10: 93- 120. Goering, H.K. and Van Soest, P.J., 1970. Forage fiber analysis (apparatus, reagents, procedures and some applications). Agricultural Handbook No. 379. ARS-USDA, Washington, DC., 20 PP. Kamatali, P., Teller, E., Vanbelle, M., Collignon, G. and Foulon, M., 1992. In situ degradability of organic matter, crude protein and cell wall of various tree forages. Anim. Prod., 55: 29-34.

Research 25 (1997) 129-140

139

Kibon, A. and Orskov, E.R., 1993. The use of degradation characteristics of browse plants to predict intake and digestibility by goats. Anim. Prod., 57: 247-251. Larbi, A., Thomas, D. and Hanson, J., 1993. Forage potential of Erythrina abyssinicu: intake, digestibility and growth rates for stall-fed sheep and goats in southern Ethiopia. Agrofor. Syst., 21: 263-270. Larbi, A., Kurdi, LO., Said, A.N. and Hanson, J., 1994. In situ ntmen evaluation of Erythrinu provenances. J. Anim. Sci. (Suppl. 1). 77: 167. Le Houerou, H.N., 1980. Browse in northern Africa. In: H.N. Le Houerou (Editor), Browse in Africa: The Current State of Knowledge. International Livestock Centre for Africa (ILCA), Ethiopia, Addis Ababa, pp. 52-55. Mehrez, N.P. and Orskov, E.R., 1977. A study of the artificial fibre bag technique for determining the digestibility of feeds in the rumen. J. Agric. Sci., 88: 645-650. Migongo-Bake, W., 1992. Rumen dry-matter digestive efficiency of camels, cattle, sheep and goats in a semiarid environment in eastern Africa. In: J.W.S. Stares, A.N. Said and J.A. Kategile (Editors), The Complementarity of Feed Resources for Animal Production in Africa. Proceedings of the Joint Feed Resources Network Workshop held in Gaborone, Botswana, 4-8 March I99 I, International Livestock Centre for Africa (ILCA), Addis Ababa, Ethiopia., pp. 27-35. Minson, J.D., 1980. Nutritional differences between tropical and temperate pastures. In: F.H.W. Morley (Editor), Grazing Animals. C.A.B., Fumham Royal, Slough, UK, pp. 167-182. Mould, E.D. and Robbins, C.T., 1981. Evaluation of detergent analysis in estimating nutritional value of browse. J. Wild]. Manage., 45: 937-947. Nsahlai, I.V., Siaw, D.E.K. and Osuji, P.O., 1994. The relationships between gas production and chemical composition of 23 browses of the genus Seshaniu. J. Sci. Food Agric., 65: 13-20. Onwuka, C.F.I., Akinsoyinu, A.O. and Tewe, O.O., 1989. Feed value of some Nigerian browse plants: chemical composition and in uitro digestibility of leaves. E. Afr. Agric. For. J., 54: 157-163. Orskov, E.R. and McDonald, I., 1979. The estimation of protein degradability in the rumen from incubation measurements weighted according to rate of passage. J. Agric. Sci. (Camb.), 92: 4999503. Reed, J.D., McDowell, R.E., Van Soest, P.J. and Horvath, P.J., 1982. Condensed tannins: a factor limiting the use of cassava forage. J. Food Sci. Agric., 3: 213-220. Reed, J.D., Horvath, P.J., Allen, M.S. and Van Soest, P.J., 1986. Gravimetric determinations of soluble phenolics including tannins from leaves by precipitation with trivalent ytterbium. J. Food Sci. Agric., 36: 255-261. Rittner, U. and Reed, D., 1992. Phenolics and in-vitro degradability of protein and tibre in West African browse. J. Sci. Food Agric., 58: 21-28. SAS Institute Inc./STAT, 1988. User’s Guide version 6. Statistical Analysis Systems Institute Inc., Caty, North Carolina, USA, pp. 283-773.

140

A. Lnrhi et ul./Smull

Rumirwnt Research 25 (1997) 129-140

Siaw, D.E.K.A., Osuji, P.O. and Nsahlai, I.V., 1993. Evaluation of multipurpose tree germplasm: the use of gas production and rumen degradation characteristics. J. Agric. (Camb.), 120: 319-330. Topps, J.H., 1992. Potential, composition and use of legume shrubs and trees as fodder for livestock in the tropics. J. Agric. Sci. (Camb.), 118: 1-8. Tolkamp, B.J. and Brouwer, B.O., 1993. Statistical review of

digestion in goats compared with other ruminants. Small Rumin. Res., 11: 107-123. Wilson, A.D., 1977. The digestibility and voluntary intake of the leaves of trees and shrubs by sheep and goats. Aust. J. Agric. Res., 28: 501-508. Winrock, 1992. Assessment of animal Agriculture in sub-Saharan Africa. Winrock International Institute for Agricultural Development, Morrilton, Arkansas, USA, 192 pp.