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4.2 Tree Legumes as Dietary Supplements for Ruminants

B.W. Norton


Introduction
What is a Supplement?
Leguminous Trees as Supplements to Low Quality Forage
The Comparative Value of Forage Tree Legumes
Effects of Forage Tree Legumes on Animal Performance
The Use of Forage Tree Legumes in Tropical Grass Silages
Conclusions
References


Introduction

Leguminous tree leaves have traditionally been fed as supplements to housed and tethered animals in Asia, Africa and the Pacific islands. Species such as Leucaena leucocephala (leucaena) have also been grown with grasses in fodder banks to provide a source of high quality forage for ruminants raised in cut-and-carry systems. Legume tree leaves maintain higher protein and mineral contents during growth than do grasses, which decline rapidly in quality with progress to maturity. Legume tree foliage is therefore useful as a protein supplement. There is increasing interest in the use of these trees as sources of high quality feed for grazing ruminants and as supplements to improve the productivity of ruminants given low quality feeds. The use of forage tree legumes in grazing systems for cattle will be discussed later in this volume (Section 4.5).

This section reviews the use of leguminous trees as supplements to ruminants on low quality diets. The response of the different ruminant species (cattle, sheep and goats) and the comparative advantages of different tree foliage species as supplements are discussed.

What is a Supplement?

The microbial population in the ruminant fore-stomach is responsible for the digestion of both the fibrous and soluble fraction of plant material consumed. This fermentation results in the production of volatile fatty acids (VFA) which are the major source of energy for ruminants. Microbial cells and undigested plant proteins are the main sources of protein. Maximum fermentation rates are attained when all factors required by the ruminal microorganisms are available, namely - a source of energy (sugars, cellulose), nitrogen (N), sulphur (S) and minerals. As described earlier, when the rate of fermentation is restricted, feed intake decreases and nutrient availability to the animal is limited. Low quality diets (straws and mature grasses) are characterised by low animal productivity as shortage of one or more of the essential nutrients limits microbial activity. Supplements are required to correct these deficiencies, thereby increasing basal feed intake and hence animal production. The amount of leguminous tree foliage needed to provide effective supplementation will vary with the quality of the basal diet, the quality of the supplement and the level of animal production expected (maintenance or growth). Any evaluation of forage trees as supplements should therefore investigate the effects of increasing levels of supplement on animal performance so that minimum quantity-maximum effect responses can be determined.

Leguminous Trees as Supplements to Low Quality Forage

There is an extensive and diverse literature on the effects of leguminous tree supplementation on the productivity of cattle, sheep and goats. Forage tree leaves, particularly Leucaena and Gliricidia sepium (gliricidia), have been used as supplements to a wide range of forages and agricultural by-products. They have been incorporated into concentrate rations as substitutes for more expensive processed protein sources, used as supplements to sisal waste in Mexico and as the major protein source for cattle fed molasses diets. Table 4.2.1 provides information on the response of cattle, sheep and goats to supplements of tree foliage to low quality hay diets. The levels of supplementation ranged from 10 to 33% of dry matter intake, or from 0.3 to 1.1% liveweight.

Since basal feed intake usually increases with supplementation, practical recommendations for levels of supplement to be offered are better expressed in relation to liveweight of the animal than as a percentage of a diet. The studies of Bamualim et al. (1984a,b) with goats and sheep given leucaena as a supplement to spear grass (Heteropogon contortus) illustrate the common response to supplementation. These authors observed an increase in hay intake and an overall improvement in diet digestibility with supplementation. Although weight changes were not measured in these experiments, the increase in digestible dry matter intake is predictive of improved weight gain. Leucaena supplementation increased rumen ammonia concentrations, stimulated microbial protein synthesis in the rumen (from 1.6 to 2.9 g/day) and increased the amount of plant protein available for absorption. The degradability of Leucaena protein in the rumen was estimated to be 66% for fresh Leucaena and 40% for dried Leucaena The increased protein absorption from the small intestine stimulated an increased voluntary consumption of low quality straw. Other experiments generally demonstrate similar responses, although supplementation of rice straw with leucaena generally did not increase basal intake but did increase digestible nutrient intake (Table 4.2.1).

Leucaena supplements at a rate of 0.6% liveweight (16% in dry matter) were effective in converting a weight loss to a significant weight gain in both sheep and cattle. Higher levels of gliricidia (1.1% liveweight) were needed to convert a substantial weight loss in cattle to maintenance. It is not possible to decide from the information available whether gliricidia is less effective than leucaena as a supplement, since there are no comparable studies where the weight changes of cattle given leucaena and rice straw were recorded.

Table 4.2.1. The effects of supplementation with tree legume foliage on the intake of low quality forages and productivity of cattle, sheep and goats.

Browse


Animal


Basal diet


Voluntary intake
(g/kg/d)

Dietary DMD (%)


Liveweight gain (g/day)


Ref.*


Tree leaves

Basal diet

Leucaena leucocephala














goats

spear

-

10.8

47.3


1


grass

4.3F

15.3

55.5



goats

maize

-

10.3

46.0


2


stover

5.5D

10.3

51.0



sheep

spear

-

12.2

50.5


3


grass

3.2F

12.3

49.3



sheep

sorghum

-

24.6

41.7

-44

4


stover

5.9D

32.8

46.7

85


cattle

rice

-

18.3

37.6


5


straw

6.8D

15.9

40.3



cattle

natural

-

20.2

42.0

-20

6


grass

5.2D

26.1

44.0

290


buffalo

rice

-

18.4

36.6


5


straw

7.4

17.1

38.6



Gliricidia sepium







goats

-

34.6F

-


I

7

sheep

-

33.9F

-


39


goats

-

32.6F

-

56.3

60-75

8

sheep

barley

6.8F

13.1

42.3


9


straw

6.8D

22.6

60.5



cattle

rice

-

27.0

47.0

-113

10


straw

11.0D

22.0

55.0

10


Calliandra calothyrsus


sheep

barley

6.8F

145

36.3


9


straw

6.8D

22.9

59.0



D = dried F = fresh
DMD = dry matter digestibility

* References: 1. Bamualim et al. (1984b); 2. Banda and Ayoade (1986); 3. Bamualin et al. (1984a); 4. Goodchild (1990), 5. Moran et al. (1983); 6. Wahyuni et al. (1982) 7. Carew (1983); 8. Murugan et al. (1985); 9. Ahn (1990); 10. Doyle et al. (1986)

The form in which the browse is fed appears to be an important determinant of the response obtained. Ahn (1990) found significant increases in intake and digestibility of barley straw fed to sheep when dried gliricidia and Calliandra calothyrsus (calliandra) were offered as supplements. For both legumes, drying decreased feed N degradability (calliandra 62-47%, gliricidia 89-71%), increased protein absorbed and increased N retention. The high degradability of both fresh and dried gliricidia in this study suggests that the poor responses of cattle fed rice straw may be due to the insignificant amount of bypass protein. In the ideal tree supplement, sufficient protein should be degraded in the rumen to provide ammonia for the basal activities of the microbes yet there should be significant amounts of bypass protein for absorption in the small intestine. A plant protein degradability of 30% would meet this ideal requirement.

The Comparative Value of Forage Tree Legumes

Table 4.2.2 shows the results of experiments in which various species of forage tree legumes were evaluated as supplements for goats. The basal diet of Napier grass (Pennisetum purpureum) used by van Eys et al. (1986) was sufficient for maintenance, and all three fodder tree species increased weight gain to the same extent. However, weight gains were further increased when a source of bypass protein (formaldehyde treated soybean meal) was provided, suggesting that the growth of goats was limited by insufficient protein available for absorption in the small intestine. High levels of foliage supplements are indicated here. The effects of drying of tree foliage on response to supplementation is clearly shown in the studies of Robertson (1988). Dried foliage promoted higher weight gains than fresh foliage for all species, with no species being superior. The poor performance of goats fed leucaena is possibly due to acute (DHP) toxicity, although some of this effect was removed by drying.

It is possible that drying may have a number of different effects. It may increase the amount of protein bypassing the rumen and decrease the content of anti-nutritive factors. Drying has been reported to improve palatability in some species. Robertson (1988) found that all leaf supplements were avidly consumed, so differential palatability was not the cause. The experiment was conducted over 5 weeks, and it is possible that over a longer period, goats may have adapted to the fresh supplements. The experiment of Ash (1990) was short-term, and no weight change results were reported. However, the low levels of supplementation suggested that growth responses would have been be minimal.

Table 4.2.3 shows some comparisons of the nutritive value of forage tree legume supplements for sheep. From the limited data available, levels of supplementation greater than 0.3% liveweight (12% dry matter) are needed to maintain the body weight of sheep given rice straw. Leucaena leucocephala cultivars promoted lower weight gains in grazing sheep than calliandra and gliricidia. Paraserianthes falcataria was superior to other species tested, and seems worthy of further study. No comparable data are available for cattle.

Table 4.2.2. Some comparisons of the nutritive value of forage tree legumes as supplements for goats.

Browse species


Voluntary intake
(g/kg DM/d)

Dietary DMD (%)


Liveweight change (g/day)


Ref.**


Tree foliage supplement

Basal diet

(a) Basal diet of Napier grass

Napier grass

-

33.4

58.1

-1

1


Gliricidia sepium

4.1D*

29.4

57.3

20



Leucaena leucocephala

4.2D

29.1

62.0

22



L. leucocephala + 2.7 g/kg F-SBM*

3.9D

26.1


45



Sesbania grandiflora

4.1D

30.2

55.9

20



S. grandiflora + 2.7 g/kg F-SBM

3.8D

33.6


52


(b) Basal diet of rice straw


Albizia chinensis


7.5F*

18.5

51.0

0

2


7.5D

16.5

44.0

54



Calliandra calothyrsus


7.5F

18.5

47.3

24



7.5D

18.5

43.6

48



Gliricidia sepium


7.5F

18.5

56.0

12



7.5D

15.5

46.9

42



Leucaena leucocephala


7.5F

15.5

48.6

-18



7.5D

18.5

47.2

0



Sesbania sesban


7.5F

14.5

53.7

0



7.5D

17.5

52.2

54


© Basal diet of Guinea grass


Guinea grass

-

19.5

51.6


3


Albizia chinensis

3.8F

17.3

53.0




Gliricidia sepium

3.9F

19.5

52.5




Sesbania grandiflora

3.8F

20.8

55.9



* F-SBM = formaldehyde treated soybean meal. D = dried, F = fresh
** References: 1. van Eys et al. (1986); 2. Robertson (1988); 3. Ash (1990)

Table 4.2.3. Some comparisons of the nutritive value of forage tree legumes for sheep.

Fodder tree legumes


Voluntary intake (g/kg/d)

Dietary DMD (%)


Liveweight change (g/day)


Reference


Tree leaves

Basal diet

Leucaena leucocephala

2.9D*

22.0

58.0

-13

1

Gliricidia sepium

2.4D

20.5

51.0

-16


Leucaena leucocephala
cv. Salvador

Sheep grazing native pasture and given concentrate supplements





12

2

Leucaena leucocephala
cv. Cunningham

15


Calliandra calothyrsus

33


Gliricidia sepium

34


Paraserianthes falcataria

57


* D = dried DMD = dry matter digestibility
* References: 1. Vearasilp (1981) (rice straw); 2. Ibrahim et al. (1988)

Effects of Forage Tree Legumes on Animal Performance

Experiments investigating the effects of increasing levels of supplementation of Leucaena and gliricidia for cattle, sheep and goats are summarised in Table 4.2.4. There are no comparable data available for other species. This information is needed if new species are to be recommended. Two supplementation strategies are indicated, viz. supplementation to prevent weight loss and supplementation which maximises liveweight gains. The first strategy provides a conservative use of tree foliage and the second a production oriented approach. The level of supplement required will depend on the quality of the basal feed. For example, high levels of forage tree supplementation (1.1% LWt or 33% DM) of rice straw are required to just maintain cattle (e.g. gliricidia (Doyle et al. 1986), leucaena (Moran et al. 1983)). Where basal diet quality is higher, lower levels (0.5% LWt or 15% DM) are probably sufficient for weight maintenance. Maximum gains are achieved when supplements are provided at 1.0-1.5% LWt (40-60% DM). Higher levels often decrease performance.

There is a need to develop standard methods for evaluating forage tree legumes both as a minimum supplement (prevention of weight loss) and as a production feed (optimising weight gain). It is recommended that four treatments be tested, viz. the basal diet fed ad libitum, tree foliage supplement provided at a rate of 0.5 and 1.5% liveweight and ad libitum. In this way, information may be gained on the supplemental value for production and the possible toxicities that might arise when animals consume the herbage as a sole feed. The feeding period should be for at least 10 weeks, and weight change and diet digestibility measured. This experimental format is presently being used to evaluate new tree legume feeds at the University of Queensland.

Table 4.2.4. The effect of increasing levels of forage tree legume supplementation on productivity of cattle, sheep and goats.

Browse species

Animal species

Basal diet

Supplemental level (%DM)

Voluntary intake (g/kg/day)

Dietary DMD %

Weight change (g/day)

Reference*

L. leucocephala





cattle

natural

0

20.2

42.0

-20

1

grass


20

26.1

44.0

290




40

28.8

46.0

540




60

28.8

44.0

590




100

22.0

51.0

310


L. leucocephala





sheep

poor

0



-9

2


hay

15



15




27



37




45



53




59



65


L. leucocephala




goats

maize

0

10.3

46.0


3


stover

35

15 8

51.0





51

20.8

48.0





59

21.5

54.0



L. leucocephala




goats

barley

0+

17.9

48.4

51

4


straw

33

29.5

60.5

71




65

30.9

57.2

66




100

27.0

62.1

46


Gliricidia




came rice

0

27.0

47.0

-113

5



straw

10

31.0

46.0

-54




20

31.0

49.0

-94




33

33.0

55.0

10


G. sepium




sheep

Brachiaria

0

weight gains of ewes

-7

6


milliformis

25

from joining to lambing

5




47

at (40 weeks)

9




72



8


G. sepium




goats

poor

0

21.8

45.0


7


hay

22

25.9

45.0





36

29.5

51.0





46

30.0

55.0



Albizia chinensis




goats

barley

0+

18.9

45.9


4


straw

27

27.8

56.4





61

27.4

48.8





100

24.6

48.0



Sesbania sesban




goats

barley

0+

17.7

48.3

41

4


straw

33

28.7

60.9

47




66

31.7

64.1

63




100

27.8

63.9

9


DM = dry manor
DMD = dry matter digestibility
0+ Supplemented with 70 g molasses + 30 g urea

* References: 1. Wahyuni et al. (1982) (Indonesia); 2. ILCA (1987) (Ethiopia); 3. Banda and Ayoade (1986) (Malawi); 4. Norton et al. (1992) (Australia); 5. Doyle et al. (1986) (Thailand); 6. Chadhokar and Kantharaju (1980) (Sri Lanka); 7. Smith and van Houtert (1986) (Nigeria)

The Use of Forage Tree Legumes in Tropical Grass Silages

In many parts of the wet tropics, the conservation of grass for hay is a problem due to slow rates of drying which reduce the quality of the hay. In temperate areas, where slow rates of drying are experienced, silage is a common form of grass conservation. A major reason for poor quality silage is loss of protein which is degraded to ammonia during the anaerobic fermentation that produces lactic acid. Effective fermentation requires a source of soluble carbohydrate which is usually present in high quality temperate grasses.

In anticipation of low levels of soluble carbohydrate in tropical grasses, molasses is often added. However, with a high quality hay such as pangola grass (Digitaria decumbens), there was no advantage gained by adding molasses (Tjandraatmadja et al. 1993). Table 4.2.5 shows results from studies where tropical grasses and tree leaves were used to make silage for feeding to sheep. The inclusion of both gliricidia and leucaena produced highly palatable silages which promoted weight gain. When compared with sorghum silage, which is usually recommended for tropical areas, the tree-pangola grass silages were superior. When lower quality grasses were used (Setaria sphacelata) molasses was necessary to produce silages which promoted weight gain. In other studies with these silages, feed protein degradabilities were determined as 78% for pangola silage, 65% for leucaena + pangola silage and 75% for gliricidia + pangola silage. These values suggest that, unlike other silages, a significant component of the original bypass protein in the browse was retained after fermentation. As found previously, gliricidia protein was more degradable in the rumen than leucaena proteins. These studies suggest that tree legume leaves may be a useful protein addition to tropical silages.

Conclusions

This review suggests that forage tree legumes have considerable potential as supplements to low quality diets and that their use as supplements merits further investigation. However, whilst there is considerable information available on the supplementation value of leucaena and gliricidia, less is known about other forage tree legumes. Forage tree legumes are a costly resource to establish and their judicious use is required if maximum benefit is to be obtained from them. A knowledge of their comparative nutritive value and the levels of supplementation required for particular purposes is needed if these trees are to become an important part of the feed resources available to livestock producers.

Table 4.2.5. The use of leucaena and gliricidia leaves in silage for sheep (Tjandraatmadja 1989).

Grass

Forage tree

Molasses

Intake (g/kg/day)

DMD (%)

Weight change

Nitrogen balance
(% intake)

Rumen ammonia
(mg N/L)

Pangola hay

-

-

23.9

64.7

+

16.6

134

Pangola grass





-

+

16.1

60.6

-

6.8

100

L. leucocephala

-

22.9

54.9

+

28.8

88

L. leucocephala

+

22.7

56.4

+

33.6

77

G. sepium

-

23.1

53.3

+

36.4

77

G. sepium

+

25.4

55.8

+

40.3

88

Setaria hay

-

-

16.7

40.6

-

< 0

31

Setaria grass





-

+

19.0

56.5

-

6.7

54

L. leucocephala

-

22.1

53.6

0

31.0

77

L. leucocephala

+

21.1

57.4

+

35.5

105

G. sepium

-

17.1

54.4

-

33.3

80

G. sepium

+

21.8

60.4

+

36.2

114

Sorghum silage

-

-

15.9

57.1

-

< 0

46

References

Ahn, J.H. (1990) Quality assessment of tropical browse legumes: tannin content and nitrogen digestibility. PhD thesis, The University of Queensland.

Ash, A.J. (1990) The effect of supplementation with leaves from the leguminous trees Sesbania grandiflora, Albizia chinensis and Gliricidia sepium on the intake and digestibility of Guinea grass hay by goats. Animal Feed Science and Technology 28, 225-232.

Bamualim, A., Weston, R.H., Hogan, J.P. and Murray, R.M. (1984a) The contributions of Leucaena leucocephala to post-ruminal digestible protein for sheep fed tropical pasture hay supplemented with urea and minerals. Proceedings of the Australian Society of Animal Production 15, 255-258.

Bamualim, A., Stachiw, S., Jones, R.J. and Murray, R.M. (1984b) The effect of fresh Leucaena leucocephala as a supplement on the utilisation of pasture hays by goats. Proceedings of the Australian Society of Animal Production 15, 259-262.

Banda, J.L.L. and Ayoade, J.A. (1986) Leucaena leaf hay (Leucaena leucocephala cv Peru) as protein supplement for malawian goats fed chopped maize stover. In: Preston, T.R. and Nuwanyakpa, M.Y. (eds), Towards Optimal Feeding of Agricultural By-products to Livestock in Africa, ILCA, Addis Ababa Ethiopia

Carew, B.A.R. (1983) Gliricidia sepium as a sole feed for small ruminants. Tropical Grasslands 17, 181-184.

Chadhokar, P.A. and Kantharaju, H.R. (1980) Effect of Gliricidia maculata on growth and breeding of Bannur ewes. Tropical Grasslands 14, 78-82.

Doyle, P.T., Devendra, C. and Pearce, G.R. (1986) Rice Straw as a Feed for Ruminants. International Development Programme, Canberra, pp. 101-102.

Goodchild, A.V. (1990) Use of leguminous browse foliage to supplement low quality roughages for ruminants. PhD thesis, The University of Queensland.

Ibrahim, T.M., Palmer, B., Boer, M. and Sanchez, M. (1988) Shrub legume potential for integrated farming systems in northern Sumatra - nutritional constraints and palatability. Proceedings of the Malaysian Society of Animal Production 11, 128-132.

ILCA (1987) Leucaena feeding trials. In: International Livestock Centre for Africa Annual Report for 198617. Addis Ababa, Ethiopia pp. 39-40.

Moran, J.B., Satoto, K.B. and Dawson, J.E. (1983) The utilisation of rice straw fed to Zebu cattle and swamp buffalo as influenced by alkali treatment and leucaena supplementation. Australian Journal of Agricultural Research 34, 73-84.

Murugan, M., Kathaperumal, V. and Jothiraj, S. (1985) Preliminary studies on the proximate composition and nutritive value of Gliricidia maculata leaves. Cheiron 14, 218-20.

Norton, B.W., Kamau, F.K. and Rosevear, R. (1992) The nutritive value of some tree legumes as supplements and sole feed for goats. In: Reodecha, C., Sangid, S. and Bunyavetchewin, P. (eds), Recent advances in animal production, Proceedings of the Sixth AAAP Animal Science Congress, 23-28 November 1992. Sukothai Thammathirat Open University, Nonthaburi, Thailand, Volume III, p. 151.

Robertson, B.M. (1988) The nutritive value of five browse legumes fed as supplements to goats offered a basal rice straw diet. Master of Agricultural Studies thesis, The University of Queensland.

Smith, O.B. and Van Houtert, M.F.J. (1987) The feeding value of Gliricidia sepium. A review. World Animal Review 62, 57-62.

Tjandraatmadja, M. (1989) The microbiology and nutritive value of tropical silages. PhD thesis, The University of Queensland.

Tjandraatmadja, M., Norton, B.W. and MacRae, I.C. (1993) Ensilage characteristics of three tropical grasses as influenced by stage of growth and addition of molasses. World Journal of Microbiology and Biotechnology. (In press.)

van Eys, J.E., Mathius, I.W., Pongsapan, P. and Johnson, W.L. (1986) Foliage of the trees gliricidia, leucaena, and sesbania as a supplement to napier grass for growing goats. Journal of Agricultural Science (Cambridge) 107, 227-233.

Vearasilp, T. (1981) Digestibility of rice straw rations supplemented with Leucaena leucocephala and Gliricidia maculata. Thai Journal of Agricultural Science 14, 259-264.

Wahyuni, S., Yulianti, E.S., Komara, W., Yates, N.G., Obst, J.M. and Lowry, J.B. (1982) The performance of ongole cattle offered either grass, sun-dried Leucaena leucocephala or varying proportions of each. Tropical Animal Production 7, 275-283.


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