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Role of crop residues as livestock feed in Ethiopian highlands

Daniel Keftasa

Pastures and Forage Crops
Ministry of Agriculture South-Eastern Zone, Ethiopia


Introduction
Current practices
Conclusion
References

Abstract

Ethiopia is known for large livestock populations of which 80% are raised in the highlands where intensive crop farming is al so undertaken using ox traction. Crop residues particularly cereal straws are the major livestock feed particularly in the dry seasons, providing 40-50% of the total annual livestock feed.

Evaluation of nutritional value of crop residues shows that they are generally low in digestibility and protein content.

Improving intake and digestibility of crop residues by physical and chemical treatments (NaOH NH3) are technically possible but they do not have practical value in Ethiopia at present. Supplementation of crop residues with molasses, oilseed meals and leguminous fodder crops have been observed to increase both intake and digestibility of crop residues, and the system is being developed.

Intercropping cereals with leguminous fodder crops and supplementation of crop residues with foliages of Leucaena, Sesbania, etc. and hays of Trifolium, alfalfa and vetch appear to have much practical value in mixed farming systems of the Ethiopian highlands.

Introduction

Ethiopia has the largest livestock population in Africa with approximately 26 million head of cattle including about six million draught oxen. About 80% of these animals are raised in the intensively cultivated highland part of the country. The Ethiopian highlands cover 490,000 km² or about 40% of the country and almost half of the total African highland area (Gryseels and Anderson, 19 8 3).

Ethiopia has unique agricultural features such as the use of teff (Eragrostis tef) as a cereal and enset (Muse ensete) as a root crop, an indigenous system of ox traction and the extensive use of equines (seven million) for transport (Jahnke, 1982).

Land use is dominated by mixed smallholder rainfed agriculture producing cereals, pulses and livestock. Crop production and livestock husbandry are commonly integrated in the mixed farming system of the medium-highland zones of Ethiopia. Oxen are important suppliers of draught power for land development, tillage, threshing and transport which means that the more crop production is increased, more and more oxen are required. This fact is even more realistic in most parts of high potential agricultural zones of Ethiopian highlands due to the uneven nature of the landscape. In Ethiopia, about six million ha of land are put under annual grain crops; mainly wheat, barley, teff, maize, sorghum and pulses.

As more and more land is put under crop production, livestock feed becomes scarce and crop residues particularly cereal straws remain the major feed source for the animals particularly during the dry period of the year (which spans the November to May period). Some estimates indicate that crop residues provide 40-50% of the annual livestock feed requirement.

This paper contains current practices of straw utilisation and reviews efforts made to improve nutritional quality of crop residues in Ethiopia.

Current practices

Straw Utilisation

From about 6 million ha of farmland about 12 million tonnes of crop residues (grain yield 10 qt/ha and 2:1 straw to grain ratio) are annually produced in Ethiopia of which about one-third is left in the field for aftermath grazing (stubbles).

Farmers use crop residues for different purposes, e.g. for fuel as firewood and minor constructions, especially maize and sorghum stovers; for roofing local houses, in the case of wheat, oat and barley straws; as binding material for walls of local houses, especially teff straw. But the major use is for livestock feed particularly for draught oxen during dry seasons.

Animals feed on crop residues mainly in two ways. The residues are piled in stacks near homesteads and animals are let to eat from the stacks or given small quantities in the morning and evening, or for working oxen, before and after work. Alternatively, the residues are left in the threshing ground and consumed by animals together with the standing straws which are left for aftermath grazing.

In some parts of the Ethiopian central highlands farms and government-owned fattening feed lots use straws with molasses and urea. There is a strong tendency towards improving the utilisation of crop residues by supplementing with molasses and/or urea at beef farms. And at some farmer cooperatives pen fattening of cull cows and old oxen is practised on straw-based diets.

Production of crop Residues From Different crops

Grain and straw yields of different crops are shown on Table 1. Yields of grain and crop residues are highly correlated. High grain yields are the result of high vegetative growth which is associated with high production of crop residues. The straw to grain ratio for wheat varieties ranges from 1.8 to 2.9 and of barley from 1.9 to 2.6. It appears that varieties of low yield potential produce the highest straw to grain ratio i.e. have the lowest harvest index.

Table 1. Mean yields of grain, residues, harvest indices, CP and CF (% of DM) of different crops in Arsi Region, Ethiopia.

Crop varieties

Grain yield kg/ha

Residue kg/ha

Total kg/ha

Residue to grain ratio

Harvest index %c

% CP

of DM
CF

Wheat

Enkoy

4585

9808

14393

2.1

32

4.99

38.0

Romany

4000

10872

14872

2.7

27

5.04

40.0

K6295-4A

2890

7969

10859

2.7

27

4.85

35.5

Bulk

3822

9400

13222

2.5

29

5.28

36.5

Dashen

5156

9138

14294

1.8

36

4.36

37.5

Gara

4448

9813

14261

2.2

31

5.28

35.0

Batu

3953

8590

12543

2.2

32

5.72

31.3

Local

2392

6862

9254

2.9

26

4.70

40.0

Barley

Improved (food)a

2737

7004

9741

2.6

28

4.4

36.6


Improved (malt)b

2918

5972

8890

2.0

33

5.7

36.2

Arusso

3180

5900

9080

1.9

35

4.30

39.0

Local

1982

4665

6647

2.4

30

5.76

35.0

Tef

DZ-354

2100

7100

9200

3.4

23

3.83

29.0

Horsebeans


2200

3900

6100

1.8

36

7.67

48.0

Fieldpeas


2340

12000

14340

5.1

16

13.8

41.0

a IAR 485, A-HOR.
b HB37, HB42, Holker.
c Harvest index = Grain yield (kg)/Total above-ground weight (kg)

Samples were collected from trial plots and the Seed Multiplication Farm, so that the yield figures for different crops might deviate from what is normally expected. However, the figures shown for residue to grain ratio, harvest index and contents of crude protein and crude fibre can safely be used for rough estimation.

Reed et al. (1986) have also demonstrated that high grain yielding varieties of sorghum (in Ethiopia) can also yield reasonably high amounts of crop residue with high nutritive value.

Nutritional Quality

As shown in Table 1 there are considerable variations in the contents of crude protein and crude fibre among different crop residues and varieties of the same crop.

Nutritional values of different crop residues and some forages are shown in Table 2. Chemical composition of the cereal crop residues contain a large proportion of lignocellulosic cell wall constituents and have low crude protein contents. Thus one could expect both voluntary intake and digestibility of the crop residues to be low. Generally, cereal crop residues have an energy content of less than 7.0 MJ/kg dm. As shown in Table 2 the digestible protein content of cereals is below 20 mg/kg which is only about 25% of that from grazing grasses. Legume straws contained less crude fibre, higher digestible protein and calcium than cereal straws.

Quite a remarkable difference between the crude protein contents of cereal and legume straws was observed. Comparing Tables 2 and 3 it can be estimated that the digestible protein contents of wheat and barley straws is about 40 and that of pulses is about 45% of the total crude protein contents which implies that figures of crude protein contents are not the best measurement of quality but that digestibility is more important.

Table 2. Nutritional values of some straws and fodder crops.



Fibre

Digestible protein

Ca

P

Energy

% of DM

g/kg

g/kg DM

g/kg DM

MJ/kg DM

Barley straw

39.5

18

3.0

0.8

6.8

Wheat straw

41.0

14

2.4

0.7

6.2

Tef straw

35.9

19

4.1

0.5

6.8

Pea straw

26.0

40

13.2

0.6

7.1

Bean straw

40.1

20

5.2

0.5

6.8

Native grasses1

28.9

87

3.9

1.6

8.9

Improved grasses


(tropical)1

28.2

79

4.3

1.4

8.7


(temperate)1

25.4

119

4.8

1.9

9.1

Vicia1

33.2

146

12.0

1.4

9.1

Alfalfa1

22.2

186

28.0

2.4

10.4

1 Included for comparison.
Source: Evaldson (1970).

Table 3. Chemical analyses of different straws at Chilalo, Ethiopia.

Crops/varieties

% Dry matter

% Crude protein

% Crude fibre

% Ash

Barley improved (varieties)

92.7

4.6

41.4

10.6

Barley local (varieties)

93.5

5.4

43.5

11.8

Wheat improved (varieties)

92.5

3.7

43.0

9.9

Wheat local (varieties)

93.0

4.8

45.4

10.8

Triticale

91.0

2.4

41.5

10.4

Tef

91.3

4.2

38.8

6.7

Maize (cobs, stalks)

92

3.5

33.6

4.6

Sorghum

91.5

1.7

40.0

4.9

Horsebeans

92.2

4.0

43.4

10.3

Fieldpea

93.5

9.7

47.3

9.6

Lentiles

91.5

5.1

52.5

4.4

Flax

90.5

4.9

49.5

4.2

Chickpea

93.0

9.2

49.8

4.3

Vicia dasycarpa

93.5

9.8

41.2

11.2

Improvement in Nutritional Quality of Crop Residues

Straws are poor quality feed because they have a low ME content (often less than 7.5 MJ/kg/DM). Variations are caused by varietal differences, season of planting, harvesting conditions and height of cut.

The feeding value of straw depends on intake and digestibility. To achieve maximum intake of straw a crude protein content of 66-85 g/kg DM is necessary. Maximum intake of DM has been observed when crop residues form 16-35% of the diet.

From studies at ILCA in Ethiopia (Most and Butterworth, 1985) showed that cereal crop residues are often less than 50% digestible and intake is usually 50 g/kg LW 0.75 or less.

Preston and Leng (1987) reported that straws from various species of grain crops appear to be highly variable in in vitro digestibility and the crude protein content is always low (Table 4).

Table 4. In vitro OM digestibility and N content of straws from different crops.


In vitro OM dig. %

N content % DM

Wheat straw

28-58

0.4-1.0

Oat straw

34-68

0.4-1.0

ice straw

40-52

0.5-1.0

Barley straw

34-61

0.4-1.0

Maize

31-50

0.5-1.2

Sorghum leaves

65-78

0.5-0.8

Generally, crop residues are poor quality feed so that their digestibility is low, and also they contain low N which limits voluntary intake and nutritional value.

Straw Treatments

Physical treatments

The most commonly used physical treatment has been grinding. It reduces particle size and increases the surface area of the straws exposed to rumen microbial action. Straws have the disadvantage of being extremely bulky, making costs of transportation high per unit of nutritive value. One advantage of grinding or fine chopping is to reduce the bulk of the materials.

Soaking straw in water just before feeding has also been practised to increase dry-matter intake and hence digestible organic-matter consumption (Chaturvedi et al., 1973; Holzer et al., 1975).

Sundstol (1981) and Nicholson (1981) have reported that high pressure steam, high temperature treatment and irradiation of straws are effective in increasing the digestibility under laboratory conditions. This practice appears to be costly and might not be used in the foreseeable future at small-scale livestock husbandry systems such as those in Ethiopia.

Chemical treatments

The most widely used chemicals to treat straws have been sodium hydroxide (NaOH) and ammonia (NH3). It has long been known that soaking in lime (alkaline solution) improves intake and digestibility of straw. Butterworth and Mosi (1986) (quoting Jaasuriya) reported that treating roughages with sodium hydroxide can increase their digestibility by 10-20 percentage points and increase intake by 30-50%. Studies conducted in U.K. (FAO, 1977) show that inclusion of up to 30% treated straw (with 5-6% NaOH) in complete diets has not depressed production of milk or beef.

Ammoniation of crop residues using gaseous ammonia or through wet ensiling (for 10-30 days) with urea (4-5%) has been found applicable for practical use at present.

Preston and Leng (1987) reported that this practice increases digestibility by 5-10% units, nitrogen content of the straw, and acceptability and voluntary intake of the treated straw by 25-50% as compared to untreated straw.

In Ethiopia, urea (46% N) is dissolved in water and sprinkled over the residues and fed at the rate of 75-100 g in/day/animal in some beef production feedlots.

Supplementation

With molasses

In Ethiopia, over 50,000 tonnes of molasses is produced annually of which about 55% is exported (Alemaychu Mengistu, 1985). The practice of using molasses as a supplementary feed for livestock has not been well understood at present. Due to the drought problem in 1984/85, the Ministry of Agriculture and ILCA jointly conducted some studies and as a result of this work molasses/urea mixtures are being used as a strategic feed reserve in the drought stricken areas and as a routine feed in cattle fattening farms. Molasses is used as a palatable carrier for urea and minerals for improving the utilisation of crop residues. Molasses/urea mixtures are used also as the basis of a supplement to crop residues for routine feeding during the dry season. In cattle fattening enterprises, Preston (1985) recommended that molasses (at free choice) should be supplemented with 2.5% urea, cereal straw (0.8% liveweight on dry-matter basis) and protein meal about 0.25% of liveweight basis.

With oil cakes

Most of the oil seed plants such as noug (Guizotia abyssinica), linseed, groundnuts, rapeseed, sesame and sunflower are widely grown in Ethiopia. The cakes of these crops are widely used as a protein supplement to low quality hays and crop residues.

With leguminous folders

Leguminous forage crops which are rich in protein and usually high in digestibility have been found beneficial as a supplement to improve intake and digestibility of crop residues. From studies conducted in Ethiopia, Mosi and Butterworth (1985) found that addition of 20-25% Trifolium tembense hay to teff straw increased feed intake of sheep by 20-30%. In another study Butterworth and Mosi (1986) reported that where hay from Trifolium is supplemented to residues of teff, oat, wheat and maize at the rate of 30% by weight, dry-matter digestibility was increased by about 10 percent units as compared to straws alone (Figure 1).

Olayiwole et al. (1986) have also obtained satisfactory growth rates of crossbred dairy heifers by feeding cereal crop residues supplemented with small amounts of maize and urea and additional protein from Trifolium hay and noug meal (Table 5).

Improving cereal crop residues by supplementing with green forage legumes such as foliage from Leucaena, Sesbania, pigeon pea or hays from Trifolium, alfalfa and vetch, is the most practical method which can be adopted locally by small-scale farmers. Growing forage legumes on land that could otherwise be fallowed has the additional benefit of increasing the yield of subsequent crops through the nitrogen fixed by the legume.

Table 5. Pooled mean values of total dry-matter intake (g/kg LW0.75) and weight gain (g/day) by animals fed different combinations of cereal crop residues (teff and wheat), Trifolium hay, urea and noug meal.


-Trif

+Trif

No urea or no noug

Urea

Noug

DM intake (gm/kg LW.75)

76.5

80.7

72.2

71.7

86.8

Wt gain g/day

133

227

72

179

289

Source: Olayiwole et al. (1986).

Intercropping cereals with legumes such as Dolichos with maize or sorghum (Haque, ILCA, Addis Ababa, Ethiopia, unpublished data) can improve the nutritional value of the residues. This practice appears more appropriate and a cost-effective way as compared to other methods of improving the nutritional value of crop residues.

Figure 1. Effect of addition of Trifolium hay on dry-matter digestibility of cereal straws.

Source: Butterworth and Mosi (1986).

Conclusion

In high potential agricultural zones of the Ethiopian highlands more and more land is being cultivated for crop production every year to satisfy the increasing human demand for food. Consequently, the grazing lands are becoming scarce and crop residues remain the main feed source for livestock. The limiting factors with the utilisation of crop residues as livestock feed are low voluntary intake and poor digestibility. Emphasis is being given to assess implications of a more widespread use of crop residues as livestock feed and possibilities of improving nutritional value.

Various methods of physical and chemical treatments of straws have been developed. Both treatment methods have been found to require heavy investment on machinery followed by regular availability or supply of replacement parts and chemicals which would not be feasible for small-farmer level at present in Ethiopia. Growing fodder legumes and use of these fodders as supplement to crop residue is the most practical and cost-effective method of improving nutritional value of crop residues. This creates an opportunity for crop residues to play a useful role in reducing weight losses of animals particularly during dry periods.

Better use of crop residues ought to be stressed, and research efforts must be directed to develop methodologies by which the utilisation of this resource could be increased. Plant breeders seldom consider the fact that crop residues are the most, often the only, available livestock feed resource when selecting crop varieties for high grain yields. Straw yield and nutritional quality might have to be considered when new varieties are developed.

Possibilities of sowing legumes under cereals and improvement of the nutritional qualities of crop residues by supplementations with leguminous fodders should be emphasised in the future.

References

Alemayehu Mengistu. 1985. Feed resources in Ethiopia. A paper presented at the Workshop on Animal Feed Resources for Small Scale livestock Producers, 11-15 November 1985, Nairobi, Kenya. 12 pp.

Butterworth, M.H. and Mosi, A.K. 1986. The voluntary intake and digestibility of combinations of cereal crop residues and legume hay for sheep. ILCA Bulletin 24:14-17.

Chaturvedi, M.L., Singh, U.B. and Ranjhan, S.K. 1973. Effect of feeding water soaked and dry wheat straw on feed intake digestibility of nutrients and VFA production on growing zebu and buffalo calves. J. Agric. Sci. (Cambridge) 80:393-397.

Evaldson, O. 1970. An inventory of feeding system and feed stuffs, Chilalo Awraja, Ethiopia. Minor Research Task at CADU No. 5. CADU (Chilalo Agricultural Development Unit), Asella, Ethiopia.

FAO. 1977. New feed resources. Proceedings of a technical consultation held in Rome, 22-24 November 1976. FAO Animal Production and Health Paper No. 4. FAO, Rome. 300 pp.

Gryseels, G. and Anderson, F.M. 1983. Research on farm and livestock productivity in the central Ethiopian highlands, 1977-1980. Research Report No. 4. ILCA, Addis Ababa.

Holzer, Z., Levy, D., Tagari, H. and Volcani, R. 1975. Soaking of complete fattening rations high in poor roughage. I. The effect of moisture content and spontaneous fermentation on nutritional value. Anim. Prod. 21:323-335.

Jahnke, H.E. 1982. Livestock production systems and livestock development in tropical Africa. Kieler Wissenschaftsverlag Vauk, Kiel, Germany. 253 pp.

Mosi, A.K. and Butterworth, M.H. The voluntary intake and digestibility of diets containing different proportions of Teff (Eragrostis tef), straw and Trifolium tembense hay when fed to sheep. Tropical Animal Production. 10(1):19-22.

Nicholson, J.W.G. 1981. Nutritional and feeding aspects of the utilization of processed lignocellulosic waste materials by animals. Agric. Environ. 6:205-228.

Nuwanyakpa, M., Preston, T.R. and Sayers, R. 1986. Effects of watering frequency on the response of sheep to supplementation with molasses/urea and noug cake (Guizotia abyssinica). In: T.R. Preston and M.Y. Nuwanyakpa (eds), Towards optimal feeding of agricultural by products to livestock in Africa. ILCA, Addis Ababa. pp. 93-101.

Olayiwole, M., Butterworth, M.H., Sayers, A.R. and Olorunju, S.A.S. 1986. The effect of supplementing cereal straws with urea, Trifolium hay and noug meal on feed intake and liveweight gain of growing crossbred heifers. ILCA Bulletin 24:18-19.

Preston, T.R. 1985. Molasses as animal feed supplement with particular references to Ethiopia. Forage Network Newsletter No. 7, ILCA, Addis Ababa.

Preston, T.R. and Leng, R.A. 1987. Matching ruminant production systems with available resources in the tropics and subtropics. Penambul Books, Armidale, Australia. 245 pp.

Reed, J.D., Tedla, A. and Jutzi, S. 1986. Large differences in digestibility of crop residues from sorghum varieties. ILCA, Addis Ababa.

Sundstol, F. 1981. Methods for treatment of low quality roughages. In: J.A. Kategile, A.N. Said and F. Sundstol (ed), Utilization of low quality roughages in Africa. AUN-Agri. Dev. Report 1, Aas, Norway. pp. 61-80.


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