Promising tropical grasses and legumes as feed resources in Central Tanzania II. In sacco rumen degradation characteristics of four grasses and legumes

ANIMAL FEED SCIENCE AND TECHNOLOGY

Animal Feed Science Technology

69 (1997) 341-352

Promising tropical grasses and legumes as feed resources in Central Tanzania II. In sacco rumen degradation characteristics of four grasses and legumes Rhodes N. Mero a, Peter Udkn b3* A Agricultural

Research Institute

h Swedish Uniremity

of Agricultural

Selian, Arusha.

Tanzania

Sciences, lJppsala,

Sweden

Accepted 12 August 1996

Abstract AbstractThe organic matter (OM) degradation in the rumen of leaves and stems from 4 promising grasses and 4 legumes, was studied using the in sacco technique. The data on OM degradability (g/100 g) was fitted to the exponential equation D = a + b(l - Cc’). It was shown that in grasses and legumes, leaves had higher ( P < 0.001) extent of OM degradation at the 48-h incubation time than corresponding stems, while the degradation rates (c) for leaves and stems were about the same in grasses. Legumes had higher degradation rates for leaves than for stems. The potential OM degradability (a + b) of legume and grass species was also significantly higher (P < 0.001) in leaves than in stems. It can be concluded from the rumen degradation characteristics of the species that they have potential as nutritious feeds for ruminants in central Tanzania. The higher potential degradability of leaves than stems would imply a greater potential in the nutritive value of the leaves. 0 1997 Elsevier Science B.V. KWW~~S: In sacco; Tropical;

Grasses; Legumes;

Tanzania

1. Introduction Improved pastures are important basal feeds for ruminants in Tanzania, and because of their high dry matter production in the growing season, they allow higher carrying capacity than the native pastures (Wigg, 1973) and are also superior to other low-quality forages like straws and stovers.

* Corresponding author. Department of Animal Nutrition and Management, Box 7024, 750 07 Uppsala, Sweden. Tel.: +46-018-672058; fax: +46-018.672995; e-mail: [email protected]

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Feed Science Technology 69 (1997) 341-352

Studies to evaluate and identify grasses and legumes species suitable for semiarid areas have been conducted in central Tanzania, and the results are documented by Mero and Masaoa (1991). In these studies, attention has been focused on forage dry matter production, chemical composition and in vitro organic matter digestibility of potentially adapted pasture species. Species identified as promising in terms of forage production, protein content, in vitro and in vivo digestibility and voluntary intake, are Panicum coloratum, Cenchrus ciliaris, Chloris gayana, Macroptilium atropurpureum, Macrotyloma axillare, Stylosanthes scabra and Neonotonia wightii (Mero et al., 1996; Mero and

UdCn, 1997a,b, unpublished). Screening of the legume species for phenolic compounds using the ytterbium method developed by Reed et al. (1985) also revealed insignificant amounts of these compounds in the species. Although laboratory analyses provide information regarding the nutritive value of the pasture species, the use of the in sacco technique in screening forages could provide additional information regarding the degradation characteristics in the rumen. Organic matter digestibility (OMD), as measured by this technique, has been proved to predict in vivo organic matter digestibility with higher precision than the in vitro method by Tilley and Terry (LeDu and Penning, 1982). The in sacco method has also been shown to be promising in predicting DM and apparent digestible DM intakes of temperate forages by sheep, of browse species by goats, and of crop residues and forages by cattle from their rumen degradation characteristics (Chenost et al., 1970; Kibon and 0rskov, 1993; Shem et al., 1995). The present experiment was conducted to study the in sacco rumen OM degradation characteristics from promising forage grasses and legumes adapted to semiarid environments. 2. Materials and methods Four grasses and four legumes, established at the Zonal Research and Training Centre Mpwapwa were studied to measure their organic matter degradability in the rumen, at 6 incubation times. The grasses were C. ciliuris cv. Biloela, (CCB), C. ciliaris cv. Gayndah (CCG), P. colorutum cv. Bambatsi (PCB) and C. gayana cv. Mpwapwa (cGM). The legumes were M. uxillare cv. Archer (MAA), N. wightii cv. Mpwapwa (NWM), S. scabra cv. seca (SSS) and M. atropurpureum cv. Siratro (MAS). The grasses and legumes were all harvested as first cut crops at the age of 8 weeks in the 1990 growing season and separated into leaf and stem fractions. The species were harvested fresh, predried at 60°C and ground using a hammer mill through a 3-mm screen. Samples of each morphological fraction of individual species were weighed in nylon bags of sizes as described by Orskov et al. (1980). Approximately 3 g of the samples were weighed into each bag. An adult, approximately 450 kg fistulated steer of the Mpwapwa breed was maintained on a diet of grass hay, sunflower seed cake and minerals. The mineral mix was Maclic super with the following composition (% w/w): Ca 19.95, P 11.76, Na 10.26, Cl 15.85, Mg 1.1, Cu 0.16, Co 0.02, Fe 0.5, K 0.006, I 0.02, Zn 0.5, Mn 0.4, S 0.33, Se 0.001.

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Feed Science Technology 69 (1997) 341-352

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Before starting the experiment, a 21-day preexperimental period was allowed, during which the animal was offered 6 kg of grass hay, 2 kg sunflower seed cake (20% CP) and minerals. The minerals and the protein supplement were first offered before feeding the hay. The supplements and minerals were fed at 8.00 h, while the hay was offered half at 9.00 h and the other half at 14.30 h. Single bags containing grass leaf or stem material were incubated for 0, 6, 12, 18, 24. 48, or 96 h. The above procedure was repeated 4 times. After each incubation time, the bags were removed from the steer, thoroughly washed by hand using running tap water, and later soaked in a beaker with neutral detergent (ND) solution (Van Soest et al., 1991) at 95°C overnight. After treatment with ND solution, the samples were washed again individually by hand under running tap water until visually free of detergents, and dried at 105°C to constant weight, cooled in a desiccator, and weighed. The four legume species were incubated using the same procedure as for the grasses. The DM and ash content of the original sample and of the in sacco residue were determined according to AOAC (1975).

3. Data analysis The exponential equation D = a + b(1 - e-“‘) as described by Brskov et al. (1980, 1981) was fitted to the OM degradability data where: D = OM degraded, a, h and c = model parameters and t = time (h). The instantaneously degradable u-fraction corresponds to the intercept at time zero, the potential degradability of the slowly degradable fraction to b, a + b corresponds to the total potential degradability, and the rate constant for the degradation of the b-fraction corresponds to c. The individual data sets from the 4 replicates of leaves and stems of individual grass and legume species were either fitted separately or combined over replicates or species. Effective OM degradability (EOMD) was calculated by the equation EOMD = a + bc/(c + k), where k represents fractional outflow rates per hour from the rumen and the amount of sample that will actually be degraded in the rumen. The values of k were varied between 0.02-0.06. The data of degradation rate constant, 48 h OM loss and potential degradability, were analyzed using INSTAT statistical package as described by Bum et al. (1987). The mathematical model used was: Yi,j.k = p + (Y,+ /3, +k + E,,~,~ where p represents the overall mean, (\I; stands for the I’th species, pj represents effects of the jth fraction, 1. is the effect of the kth replicate, and E~,~,~stands for the residual effects. Treatment means were ranked using LSD as described by Snedecor and Cochran, 1980.

4. Results Mean values for OM losses are shown in Table 1. Parameters obtained from fitting (replicates combined) are presented in Table 2 and in Fig. 1 the graphs are presented by family and plant fraction. The extent of OM degradation of the leaves from all grass and legume species was higher compared with stems at all incubation times (Table 1). In

28.51 8.52 38.74 7.81

10.58 0.68 20.40 1.23 18.92 1.24 19.62 1.19

Stem SEM Leaf SEM

Stem SEM Leaf SEM

Stem Leaf

Stem Leaf

CCB

PCB

Mean

SEM

26.33 34.47 3.37 2.60

13.67 19.76 2.04 1.02

24.72 1.87 34.38 2.68

34.07 3.90 37.56 4.03

14.90 1.00 21.96 3.16

Stem SEM Leaf SEM

CCG

6

time (h)

18.04 1.81 27.18 3.83

0

Incubation

10.28 0.13 17.06 1.41

Fraction

grasses

Stem SEMb Leaf SEM

Grasses CGM

Species”

Table 1 Organic matter losses(%) from leaves and stems of four tropical (means of 4 replicates)

3.20 2.43

31.94 45.73

29.43 2.15 40.57 1.36

29.90 6.86 51.07 7.07

41.37 3.94 48.47 1.49

27.06 2.57 42.82 3.54

12

and legumes

incubated

46.78 63.26 3.79 2.28

40.16 56.79 3.14 3.31

1.33

2.86

56.76 77.77

51.33 0.76 73.88 1.34

41.14 2.13 57.69 1.52 35.35 2.82 47.88 1.94

53.90 5.12 79.88 2.85

48.30 5.39 65.01 4.18

42.07 6.60 60.47 5.45

64.50 2.20 78.64 1.92

57.31 0.51 78.69 2.29

48

56.89 4.85 68.42 2.86

40.78 3.75 61.93 4.27

24

2.37 0.95

64.35 83.40

59.52 0.96 80.93 1.42

62.04 3.12 84.22 1.78

70.50 1.53 85.38 1.12

65.35 0.44 83.07 1.12

96

by neutral detergent

48.21 3.09 62.92 4.25

35.01 2.78 55.89 2.76

18

in nylon bags in the rumen followed

extraction

Stem SEM Leaf SEM

Stem SEM Leaf SEM

Stem Leaf

Stem Leaf

MAS

SSS

Mean

SEM’

2.26 0.97

19.15 37.00

13.83 0.55 35.55 2.66

24.48 3.12 39.59 2.62

11.59 1.44 36.14 0.64

20.68 2.18 35.53 2.46

2.47 1.86

34.67 57.76

27.92 0.86 57.60 3.57

1.61

37.14 2.36 63.04

34.29 3.64 55.62 5.09

39.3 1 1.44 54.76 3.90

2.48 2.04

41.27 66.99

35.67 3.01 72.33 2.80

39.67 3.55 65.33 1.67

42.19 4.84 62.71 4.15

41.54 2.11 67.58 5.37

“CGM: C. ~~IYVUZCY. Mpwapwa; CCG: C. rilimris cv. Gayndah; CCB: C. cihris cv. Biloela; MAA: M. axillnre cv. Archer: MAS: M. atropurpuruem cv. Siratro; SSS: S. scabru cv. Seca. hSEM = standard error of the mean.

Stem SEM Leaf SEM

Stem SEM Leaf SEM

MAA

Legumrs NWM

cv. Bambatsi;

1.25 2.08

55.83 79.16

53.24 2.59 83.57 0.96

54.16 2.23 73.87 0.80

58.24 2.60 81.05 5.39

51.61 1.05 78.15 0.83

PCB: P. colorurum

2.53 I .75

47.52 74.52

43.66 4.78 78.85 0.46

48.15 1.91 71.95 1.07

43.83 3.55 75.86 5.21

54.42 I .36 71.43 0.75

2.19 2.58

61.27 84.30

54.82 1.92 88.95 0.57

62.57 1.I5 76.94 1.26

64.3 1 2.7 1 86.2 1 3.88

63.61 1.14 85.11 1.07

NWM: N. wightii cv. Mpwapwa;

2.09 2.48

59.23 81.56

53.19 2.52 85.98 1.62

59.76 1.42 75.84 1.00

61.59 3.11 85.41 4.19

62.37 0.76 79.00 2.02

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Table 2 Parameter estimates from fitting the function matter (%) over time (hjd

D = a + b(l - e-“)

to the cumulative

degradation

of organic

Fraction

a

b

c

a+b

RSDf

Stem Leaf

8.99 14.46

60.07 70.90

0.03 14 0.0451

69.06 85.36

1.31 2.89

CCG

Stem Leaf

16.13 21.12

53.59 64.25

0.0553 0.0524

69.72 85.37

2.12 2.20

CCB

Stem Leaf

11.86 20.85

49.14 63.70

0.0503 0.0527

61.00 84.55

3.48 0.96

PCB

Stem Leaf

18.17 19.92

44.75 63.93

0.0277 0.0355

62.92 83.85

1.05 2.05

Total

Stem Leaf

13.44 19.14

51.34 65.01

0.0410 0.0466

64.77 84.15

5.23 4.02

Stem Leaf

21.06 35.63

42.14 47.04

0.0868 0.088 1

63.20 82.67

0.77 2.26

MAA

Stem Leaf

18.17 35.89

46.36 51.11

0.0609 0.0768

64.53 87.00

3.58 2.48

MAS

Stem Leaf

24.73 40.36

38.06 35.33

0.0536 0.133

62.79 75.69

2.07 2.42

sss

Stem Leaf

13.08 35.25

42.45 52.77

0.0745 0.0974

55.53 88.02

2.85 1.15

Total

Stem Leaf

19.24 36.97

42.33 46.57

0.0699 0.0920

61.57 83.54

3.86 3.90

Speciese Grasses CGM

Lkgumes NWM

dData sets combined over replicates (species) or species (Total): n = 28. eFor abbreviations see Table 1. fResidual standard deviation from regression.

Table 2 it can be seen that the a-values were higher in leaves than stems, particularly in the legumes. The only exception was found in the grasses where the values for PCB were similar. Values for b were also highest in leaves particularly in the grasses. In the legumes, this was also generally true, except in MAS where this was reversed. For the combined values of a + b, equal to potential OM degradability, the differences between leaves and stems were, on average, 20 units in both legumes and grasses. Table 3 shows replicate averages for rate, 48 h and potential degradation. In grasses, the degradation rates varied significantly between species (P < 0.0251, while the differences between leaves and stems were not significant (P > 0.05) (Table 3). Table 3 also shows that CCB had a higher degradation rate than at least PCB and CGM (p < 0.05). As for legumes, the rate differences among species were not significant, whereas leaves had significantly higher (P < 0.05) degradation rates compared with

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(a) 9O~i 80

-

.

204 . 10, 0

_ 20

40

d0

80

100

Time (h)

(b) 90 , 801

._ Time(h)

--

Fig. I In sacco organic matter loss from leaves (0) and stems ( W) of four legumes (a) and four grasses (b). Parameter values for curves fitted to the data, see Table 2.

stems. The 48-h and potential degradability (a + b) for grasses varied significantly (P < 0.006) with species and PCB and CCB (not 48 h) were lower than CCG and CGM (p < 0.05). Species differences among legumes. however, were not significant (P > 0.05). The potential and 48-h OM degradability were significantly higher (P < 0.001) for leaves than stems in both grasses and legumes (Table 3). Effective OM degradabilities at different outflow rates are shown in Table 4 and was higher in leaves than stems of both grasses and legumes. The differences were approximately 15 percentage units in grasses and 23 in legumes. Increasing outflow rate (kl from the rumen decreased EOMD in the grasses by approximately 14 percentage units from the lowest to the highest outflow rate compared with approximately IO for the legumes.

Stem Leaf Leaf + stem

stem

MAA

MAS

Leaf Leaf + stem

Stem Leaf Leaf + stem

Legumes

NWM

stem Leaf stem + leaf

0.060 0.145 0.103’

0.068 0.086 0.077a

0.088 0.114 0.101=

0.045A 0.050A 0.048

0.029 0.036 0.033a

Stem Leaf Stem + leaf

Total

0.058 0.066 0.062b

Stem Leaf Stem + leaf

CCB

0.059 0.053 0.056ah

0.033 0.045 0.039=

Rate

stem Leaf Stem + leaf

Leaf Stem + leaf f

potential

Degradation

rate (h-l),

CCG

CGM

stem

Fraction

Species”

Grasses

for degradation

Table 3 Analysis of variance

59.76 75.84 67.80=

61.59 85.41 73.50=

62.37 79.00 70.69a

56.76A 77.770 67.27

51.33 73.88 62.60k

53.90 79.88 66.89ah

64.50 78.64 71.57=

57.31 78.69 68.00a

48 h

and 48-h organic

degradability

62.51 75.52 69.02=

64.01 85.40 74.71a

63.20 83.27 73.24”

66.53A 85.11B 75.82

63.83 83.99 73.918

61.97 85.01 73.49a

70.44 85.78 78.11b

69.88 85.66 77.77b

Potentiale

matter

of leaves

and stems from ruminal

in sacco organic

matter incubations

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Feed Science Technology 69 (1997) 341-352

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R.N. Mere, P. Ud&/Animal

Feed Science Technology 69 (1997) 341-3.52

Table 4 Effective

organic matter degradability

(a + be/c

Fractional

+ k) at different

outflow rate (k) h-

fractional

outflow rates (%)

’

Speciesd

Fraction

0.02

0.03

0.04

0.05

0.06

CGM

Stem Leaf

45.7 63.6

39.7 57.0

35.4 52.0

32.2 48.1

29.6 44.9

CCG

Stem Leaf

55.5 67.6

50.9 62.0

47.2 57.6

44.3 54.0

41.8 51.1

CCB

Stem Leaf

47.0 67.0

42.6 61.4

39.2 57.1

36.5 53.5

34.3 50.6

PCB

Stem Leaf

44.1 60.8

39.6 54.6

36.5 50.0

34.1 46.5

32.3 43.7

Mean

Stem Leaf

48.1 64.8

43.2 58.8

39.6 54.2

36.8 50.5

34.5 41.6

Stem Leaf

55.3 74.0

52.4 70.7

49.9 68.0

47.8 65.6

46.0 63.6

Stem Leaf

53.1 76.4

49.2 72.6

46.2 69.5

43.6 66.8

41.5 64.6

Mean

40.4 55.2

Legumes

MAA

MAS

Stem

52.4

49.1

46.5

44.4

42.7

Leaf

71.0

69.2

67.5

66.0

64.7

sss

Stem Leaf

46.5 79.0

43.3 75.6

40.7 72.7

38.5 70.1

36.7 67.9

Mean

Stem Leaf

51.8 75.1

48.5 72.0

45.8 69.4

43.6 67.1

41.7 65.2

dFor abbreviations

46.3 69.8

see Table 1

The mean differences between legumes and grasses were lowest for the stems at 2% outflow rate (3 percentage units) and highest at 6% outflow rate for the leaves (18 percentage units).

5. Discussion The present experiment, with the aim of studying in sacco rumen degradation of OM of grasses and legumes selected on agronomic performance criteria, showed that the leaves of these grasses had similar rates of degradation, but higher 48 h and potential degradability in the rumen compared to stems (Tables 2 and 3). Nylon bag studies of five tropical grasses by Poppi et al. (1981) also showed that the potential digestibility of NDF was higher for leaf than stem fractions, but rates of digestion of leaf and stem were similar, as in this study. ln legumes, however, leaf-stem

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differences were noticed in all species and particularly in MAS. Also, 48 h and potential degradation differed and was largest in SSS, which has a very woody stem, small leaves and a tree-like appearance. The higher degradation rates of OM for leaves in legumes than corresponding stems in the present experiment are probably due to their superior fibre quality associated with higher cation exchange capacity, more rapid particle size reduction and rate of hydration (Van Soest, 1988). The higher lignin content found in stems compared with leaves of tropical grasses (Laredo and Minson, 1973; Poppi et al., 1980) and also of tropical legumes (Norton, 1982; Mero and UdCn, 1997~) is probably the reason for the higher 48-h degradability of leaves compared to stems. The association of lignin with cell walls is well known to limit their degradation by rumen microorganisms (Akin, 1982). Lignin by bonding to plant cell wall carbohydrates prevents swelling and consequently depresses fibre digestibility (Norton, 1982). Grasses had generally lower rates of degradation than legumes, but somewhat higher potential digestibility (Table 3), something which also has been shown for temperate forages (Smith et al., 1972). These family differences manifested themselves very clearly in the calculated values for EOMD, showing a superiority for the legumes (Table 4). From the rumen degradation characteristics of the forages studied, we can conclude that leafiness should be of great importance in both grasses and legumes, as high values should increase values for total plant EOMD as a result of higher potential degradability in the leaves, and in spite of similar degradation rates in the case of grasses. Leafiness would be especially important for the legumes and in SSS > 30 percentage units differences were noted between leaves and stems. It is recommended, therefore, to breed or select for higher leaf content, manage the crops to obtain more leaf, and allow the animals to feed selectively for higher leaf intake.

Acknowledgements We would like to thank the Swedish Agency for Research Cooperation with developing countries (SAREC) for their material and financial support of the study. Thanks are due to V. Mwiwula, A. Seif and F. Msaka of LPRI Mpwapwa for their assistance when conducting this experiment. The assistance in word processing offered by S. Kahonga of LITI, Tengeru is appreciated.

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Kibon, A., 0rskov, E.R., 1993. The use of degradation characteristics of browse plants to predict intake and digestibility by goats. Anim. Prod. 57, 247-25 1. Laredo, M.A., Minson, D.J., 1973. The voluntary intake, digestibility, and retention time by sheep of leaf and stem fractions of five grasses. Aust. J. Agric Res. 24, 875-888. LeDu, Y.L.P., Penning, P.D., 1982. Animal-based techniques for estimating herbage intake. In: Leaver, J.D. (Ed.), Herbage Intake Handbook. The British Grassland Sot., pp. 37-75. Mero, R.N., Masaoa, A.P., 1991. The use of improved pasture as feed resources for ruminants in central Tanzania: a review. In: Milk Production from Smallholder Systems with Emphasis on Feeding Strategies in Semiarid Areas. Proc. of a Seminar held at Sokoine Univ. of Agriculture, Morogoro, Tanzania. Mero, R.N., UdCn, P., 1997a. Promising tropical grasses and legumes as feed resources in Central Tanzania: I. Effect of applying different cutting patterns on dry matter production and nutritive value of six grasses and forage legumes. Tropical Grasslands (In press). Mero, R.N., Udtn, P., 1997b. Promising tropical grasses and legumes as feed resources in Central Tanzania: III. Effect of feeding level on digestibility and voluntary intake of four grasses by sheep. Anim. Feed. Sci. Technol., in press. Mero, R.N., UdCn, P., 1997~. Promising tropical grasses and legumes as feed resources in Central Tanzania: IV. Effect of feeding level on digestibility and voluntary intake of four forage legumes by sheep. Anim. Feed. Sci. Technol., in press. Mero, R.N., Shayo, C.M., UdCn, P., 1996. Promising tropical grasses and legumes as feed resources in Central Tanzania: I. Effect of applying different cutting patterns on dry matter production and nutritive value of six grasses and forage legumes. Tropical Grasslands, submitted. Norton, B.W., 1982. Differences between species in forage quality. In: Hacker, J.B. (Ed.), Nutritional Limits to Animal Production from Pasture. Proc. of the Int. Symposia held at St Lucia, Queensland, Australia, pp. 89-l 10. 0rskov. E.R., DeB Hovell, F.D., Mould, F., 1980. The use of the nylon bag technique for the evaluation of feedstuffs. Tropical Animal Production 5, 195-213. 0rskov. E.R., Hughes-Jones, M., McDonald. I., 1981. Degradability of protein supplements and utilization of undegradable protein by high-producing dairy cows. In: Haresign, W., Cole, D.J.A. (Eds.), Recent Developments in Ruminant Nutrition, pp. 17-30. Poppi, D.P., Minson, D.J., Temouth, J.H., 1980. Studies of cattle and sheep eating leaf and stem fractions of grasses: I. The voluntary intake, digestibility and retention time in the reticula-rumen. Aust. J. Agric. Res. 32, 99-108. Poppi, D.P., Minson, D.J., Ternouth, J.H., 1981. Studies of cattle and sheep eating leaf and stem fractions of grasses: II. Factors controlling the retention of feed in the reticula-rumen. Aust. J. Agric. Res. 32, 109-121. Reed, J.D., Horvath, P.J., Allen, MS., Van Soest, P.J., 1985. Gravimetric determination of soluble phenolics including tannins from leaves by precipitation with trivalent ytterbium. J. Sci. Food Agr. 36, 255-261. Shem, M.N., 0rskov, E.R., Kimambo, A.E., 1995. Prediction of voluntary dry-matter intake, digestible dry-matter intake and growth rate of cattle from the degradation characteristics of tropical foods. Anim. Sci. 60, 65-74. Smith, L.W., Goering, H.K., Gordon, C.H., 1972. Relationships of forage composition with rate of cell wall digestion and indigestibility of cell walls. J. Dairy Sci. 55, 1140-I 147. Snedecor, G.W., Cochran, W.G., 1980. Statistical Methods, 7th edn. Iowa State Univ. Press, Ames, IA. Van Soest, P.J., 1988. Effect of environment and quality of libre on the nutritive value of crop residues. In: Reed, J.D., Capper, B.S., Neate, P.J.H. (Eds.), Plant Breeding and Nutritive Value of Crop Residues. Proc. of a Workshop held at ILCA, Addis Ababa, Ethiopia, 7-10 December 1987. ILCA, Addis Ababa. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fibre, neutral detergent fibre and nonstructural polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583-3597. Wigg, P.M., 1973. The role of sown pasture in semiarid central Tanzania. E. Afr. For. J. 38, 375-381.