The potential of crop residues, particularly wheat straw, as livestock feed in Ethiopia

Lulseged Gebrehiwot and Jamal Mohammed
Institute of Agricultural Research
P.O. Box 2003, Addis Ababa, Ethiopia

Abstract
Introduction
Conclusion
Acknowledgements
References

Abstract

Crop and livestock production are important activities in the smallholder mixed farming systems in Ethiopia. Feed resources for livestock are natural herbage and crop residues. Cereal straws of teff (Eragrostis tef), barley, wheat and pulse crop residues are very important particularly during the dry season. Currently crop residues are used as is with no treatment to improve intake and digestibility. The quality and quantity of residues produced is also very low in relation to the total area of cropped land.

Results of experiments clearly indicate that the yield and quality of crop residues could be tremendously improved through agronomic practices and varietal selection. Undersowing of wheat with forage crops did not reduce grain yield but resulted in reasonable production of straw and undersown forages which could improve intake and digestibility of the residue. In the wheat improvement programme, significant variations were found among the varieties with respect to grain yield, straw yield and quality. There seems to be a wide range of possibilities to improve the production and utilisation of wheat straws, and crop residues in general. Breeders and agronomists need to consider the residue aspect as part of the overall crop improvement programme.

Introduction

Ethiopia is an agricultural country with a diverse climate varying from cool tropical highlands to arid lowlands. Though low in productivity it has the highest number of livestock in sub-Saharan Africa. Among other factors, feed shortage, both in quantity and quality, is a major constraint for the development of the livestock industry in Ethiopia.

At present two broad categories of livestock production systems are recognised in the country. In the pastoral areas, which are characterised by low and erratic rainfall, livestock are mainly kept for milk and to some extent for meat. They provide the sole means of subsistence for the nomadic pastoralists. It is estimated that some 25% of the total Ethiopian livestock population is found in this region. These animals depend entirely on the natural vegetation to satisfy their nutritional requirements.

The highlands of Ethiopia have more favourable climate; both for crop and livestock production. Over 70% of the human as well as the livestock population reside in this region. Small holder mixed farming is the dominant mode of production in the Ethiopian highlands. Major food crops grown are teff (Eragrostis tef), barley, wheat and pulses; and in the warmer regions maize and sorghum. The most important contribution of livestock to agricultural production in the Ethiopian highlands is the use of oxen for cultivation. Crops and livestock are closely integrated throughout the highlands in a complex of competitive and complementary ways (Gryseels and Anderson, 1983).

Livestock in the highland peasant farming system get their feed from natural herbage and crop residues. Cereal straws of teff, barley, wheat and pulse crop residues are stacked after threshing and fed to selected group of animals during the dry season. Livestock also have access to crop stubbles and weedy fallows. It is estimated that crop residues and aftermath grazing contribute 10% of the annual feed demand (FAO, 1981).

Crop residues have long been important as a maintenance feed for ruminants. However, when used alone, they are of very low feeding value with poor metabolisable energy, negligible available protein, and seriously deficient in mineral and vitamins (Staniforth, 1979). On the other hand, crop residues vary greatly in chemical composition and digestibility depending on varietal differences (Reed et al, 1986) and agronomic practices (Staniforth, 1979). Their feeding value and intake can also be greatly improved through treatments and supplementation with protein and energy-rich feeds (Butterworth et al, 1986, Olayiwole et al, 1986).

Developing countries like Ethiopia need to seriously consider improving the quantity and quality of crop residues produced by the smallholders. Varietal effects on the quantity and nutritive value of cereal and pulse crop residues have not received enough attention. Understandably because the major efforts have been on increasing food production only. These programmes should consider the residues as part of the overall improvement programmes.

This paper attempts to review the extent and use of crop residues in Ethiopia; mainly in the highlands. It places special emphasis on wheat with respect to varietal differences and agronomic practices to enhance the utilisation of the straws.

Extent of crop production and available residue

Estimates of the Ethiopian Central Statistics Office show that during the period of 1975 to 1978, on the average, annually about 5 million hectares of land were put under cereals and pulses. Mean grain yield for the same period was 970 kg and 810 kg/ha for creels and pulses respectively. However, during the period 1979 to 1982, the total area cultivated for cereals and pulses increased to 5.6 million hectares (Central Statistical Office, 1984). Respective grain yields also increased to 1240 kg 1140 kg/ha (Table 1).

As the area of crop production is increased, the size of grazing areas dwindles, exacerbating the problem of feed shortage. In this situation one could only cope with the problem by improving the quantity and quality of crop residues produced. FAO estimates indicate that in 1979/80, Ethiopia as a whole produced about 6.3 million tonnes of cereal straws, stovers and pulse residues (FAO, 1981). The figure seems to be low when compared with the total acreage under production. However, there are still wide options to improve total production .

Table 1. Estimated area and yield of major crops in Ethiopia.

Major Crops	1975/76 to 78/79 (4 years mean)		1979/80 to 82/83 (4 years mean)
	hectares	kg/ha	hectares	kg/ha
Teff	1,368,500	750	1,401,600	920
Barley	722,800	980	864,800	1220
Wheat	522,300	960	605,400	1140
Maize	791,200	1360	769,600	1700
Sorghum	753,500	1000	1,013,800	1490
Faba bean	277,900	1020	340,600	1490
Field peas	121,900	650	176,300	950
Haricot beans	33,300	780	26,900	910
Cereals total	4,420,300	970	4,848,300	1240
Pulses total	643,000	810	795,300	1140

Source: Central Statistical Office (1975 to 1983).

Variability of crop residues in yield and quality

The quantity and quality of residues produced by various crops vary greatly depending on crop species. Wheat and barley usually give high straw yields but of inferior quality. Among the cereals teff straw is relatively the best and is comparable to a good natural pasture hay. Pulses residues, though low in yield, are of high quality (Table 2). The quality and yield of the various crop residues shown in Table 2 could vary depending on agronomic practices and environmental conditions. However, the figures give good indications of the relative importance of the various crop residues.

Table 2. Yield and chemical composition of various crop residues on dry-matter basis.

Residue type	Percent
	Yield kg/ha	DM	EE	Ash	CP	NDF
Barley straw	10,000	92.6	2.3	8.4	4.7	71.5
Teff straw	5000	92.6	1.9	8.4	5.2	72.6
Wheat straw	9000	93.1	1.2	9.0	3.9	79.8
Faba bean residue	3800	91.7	0.8	10.4	7.2	74.3
Field peas residue	5000	91.9	1.2	6.1	6.7	73.6
Natural pasture hay	4100	92.2	1.5	9.5	6.6	73.8

DM = dry matter; CP = crude protein;
EE = ether extract; NDF = neutral-detergent fiber.

The performance of animals on residue diets is also known to vary depending on crop species. Table 3 shows the weight gains of steers fed for 116 days a ration composed of 50% residue, 20% molasses, 25% noug cake (Guizotia abyssinica), 4% bone meal and 1% salt (JAR, 1976). As shown in Table 3 wheat straw was the poorest roughage and teff straw the best. Dry-matter intake and daily weight gain were lowest for wheat straw, 5.0 kg and 352 gm/head respectively.

Table 3. Weight gains of steers fed crop residue based diets * at Holetta (1974/75) for 116 days.

Parameters considered	Roughage source
	Teff straw	Whea straw	Oats hay	Native hay
Initial weight (kg)	186	185	182	184.3
Final weight (kg)	258.8	225.9	231.9	239.6
Daily gain (g)	628	352	430	477
Daily feed intake (kg)	6.9	5	5.5	5.9
Feed/kg liveweight gain (kg)	11	14.2	12.8	12.4

* Rations consisted of 50% crop residue, 20% molasses, 25% noug cake, 4% bone meal and 1% salt. Source: IAR (1976).

Possibilities for improving the yield, quality and utilisation of wheat straw

a) Agronomic practices

The grain yield of cereals and pulses is highly influenced by various agronomic practices. Since high grain yield is usually a function of active vegetative growth, agronomic practices which aim at increasing grain yields, do result in higher yields of residue.

A fertiliser trial was carried out on irrigated wheat in the Awash Valley, a fertile alluvial soil. Though the various rates of nitrogen fertilisation had very little effect on grain production (Table 4), straw yield and quality were significantly improved. Applying 46 kg N/ha improved leaf-to-stem ratio, and % N in the leaves and stems by 20, 47 and 21% respectively over the control. With more N application there was more influence on leaf-to-stem ratio and N composition of the plant. In Ethiopia, farmers who harvest good grain crops usually have more residues to feed their cattle during the dry season. Nowadays farmers are encouraged to use fertilisers, especially in areas where rainfall is more reliable. This practice will hopefully result in more crop residues and grain yields.

b) Undersowing of forage crops to wheat

Studies by the Institute of Agricultural Research in Ethiopia show that forage crops could be successfully established under cereals. The effect of the undersown forage crops on the grain yield of the cereals varied depending on crop species and the level of weed management. When maize was undersown after second weeding (about six weeks after planting) the grain yield was not affected at all. But in the case of wheat, where the forage crops were sown at the same time with the wheat the grain yield was reduced by about 20% (Lulseged et al, 1987).

Table 4. Effect of N fertilization on grain yield and on quantity and quality of wheat straw in the Awash Valley.

Fertilizer rate	Mean for 1985 and 1986
	Grain yield	Straw yield	Leaf/stem ratio	%N leaves	%N stems
N kg/ha	kg/ha
0	3500	7900	0.83	0.38	0.17
46	3800	8600	1.00	0.46	0.25
69	3800	9100	1.02	0.57	0.30
92	4200	9200	1.07	0.63	0.34
115	4300	10400	1.16	0.65	0.34

LSD (0.05); NS 1.0 t/ha

The practice of undersowing cereals with forages has particular relevance in the highlands of Ethiopia where fallowing of cropped-land is common and feed shortage is a serious problem. Table 5 shows results of an experiment at Holetta where wheat was undersown with various forage crops. The difference in grain yield of the wheat for the various treatments was non-significant. The yield on the control plot (sole crop of wheat) should probably have been higher than the undersown plots. But because of excessive lodging the yield was even lower than the other treatments.

Table 5. The performance of wheat and undersown forage crops at Holetta (1982/83).

Undersown forage species	Wheat grain yield	Wheat straw yield (air dry)	Forage yield (dry matter)
	kg/ha	kg/ha
Control (wheat only)	2040	7900
Phalaris tuberosa cv Sirocco	2630	9800	3100
Lolium perenne cv Kangaroo Valley	3410	11400	3500
Lolium perenne cv Mt. Alma	2330	8200	7000
Lolium perenne cv Barspectra	2760	7600	4000
Festuca arundinacea	3100	11500	1300
Setaria sphacelata cv Narok	2560	9000	1900
CV%	17.8	19.8	15
LSD (0.05)	NS	NS	800 kg/ha

The most interesting part of this experiment was that on the average 9400 kg/ha of wheat straw and 3400 kg/ha of improved forages could be harvested from the same piece of land. Similar experiments in Ginchi area (Vertisol, 2200 m elevation) also showed various grasses and legumes could be successfully established under wheat (Table 6) (JAR, 1982).

ILCA's investigations on farmers' fields at Holetta indicated that undersowing native clovers namely Trifolium tembense and T. rueppellianum with 30 kg P/ha significantly improved both wheat grain and straw yields. The increase over the control (wheat alone) was 22 and 29% for grain and straw yields respectively (Abate and Jutzi, 1985). Undoubtedly the quality of the straw would be improved tremendously due to the presence of the forage species, particularly the legumes. Various investigators have reported that the digestibility and intake of crop residues alone are very low and weight gains of animals are minimal (O'Donovan, 1979; Reed et al, 1986). However, when supplemented with improved forages, particularly legumes, intake, digestibility and weight gains improved. Hence, wherever the environmental and farming system conditions permit, undersowing should be encouraged.

Table 6. Forage crops undersown to wheat, Ginchi, 1980/81.

Treatment	Wheat yield (kg/ha)	Forage establishment Score 0-5	Forage yield (kg/ha)
Sole crop (control)	2930	-	-
Alfalfa	2850	2	700
Barrel medic	3090	4	3200
Snail medic	2840	3	2100
Phalaris	3060	2	200
Llolium	1960	5	2600
Tall fescue	2900	2	700
Setaria	2790	2	400
CV	19%		0 = poor
LSD (0.05)	NS		5 = Excellent

c) The need to select for better grain and straw yielding varieties

Classically, the objective of any crop improvement programme is to raise the level of grain yields, with no consideration to straw yield and quality. Under small peasant holding, however, both the grains and straws are important. In Ethiopia over 90% of the agricultural produce comes from the peasant sector. Therefore in order to improve overall farm productivity and income of the smallholders, development of crop varieties with improved grain as well as straw yields is of paramount importance.

In the wheat improvement programme for irrigated lowlands, the selected varieties have been examined for grain yield as well as straw yield and quality. Fourteen varieties have been tested for three years in the Awash Valley. Of these, eight gave grain yields of over 4000 kg/ha. Some of the high-yielding varieties had low straw yields. Considering both grain and straw yields the varieties PAI 4, Dashen, Gara and Chenab 70 were the best with straw yields of 6300 to 7500 kg/ha (Table 7). Though there were other varieties with straw yields of nearly 8000 kg/ha, their grain yield was very low. The varieties also showed great variability with respect to leaf-stem ratio and % N in the leaves. Considering all these factors together, Chenab 70 and Dashen seem to be the best in terms of both grain and straw yield and quality.

Conclusion

In the Ethiopian highlands crop and livestock production are complementary. Since most of the livestock in the highlands are mainly kept for draught, the cultivation of more land results in more crop residues to feed the work oxen and selected group of animals. However, currently the quantity and quality of residues produced are very low.

Therefore inorder to compensate for the grazing land, which has been converted into crop land, agronomic practices and crop improvement programmes need to consider the improvement of both grain and straw yields and quality. Since there are strong crop improvement programmes of the major cereals and pulses in Ethiopia, there is a great chance of achieving success. The utilisation of crop residues also needs to be enhanced through the use of forage legumes and protein/energy-rich industrial by-products.

Table 7. Grain yield, straw yield and quality of wheat varieties tested in the Awash Valley (1985 to 1987).

	Grain yield (3 yrs mean)	Straw yield (2 yrs mean)	Leaf-to-stem ratio	% N leaves	% N stems
	kg/ha
MLKS 11	4300	5700	0.83	0.68	0.29
PAI 4	4200	6300	0.78	0.56	0.22
Dashen	4000	6900	1.08	0.79	0.32
Blue Jay 'S'	4200	5400	0.79	0.54	0.25
CM 5287-N-2M	3600	5300	0.61	0.74	0.33
CM 30136-3Y-1Y	3500	5300	0.78	0.68	-
Gara	4200	7500	0.91	0.57	0.32
Quimori	3800	6100	0.65	0.65	0.24
Chenab 70	4400	7200	0.77	0.83	0.28
Galld-4R-Resel (B)	4200	5900	0.85	0.64	0.30
Monco x WW x LEE	4100	5600	0.96	0.66	0.29
Gall-YR-Resel (B)	3700	7800	0.95	0.61	0.24
Enkoy	3700	7800	0.68	0.58	0.35
Ani 'S' Cm 26346	3600	5800	0.50	0.59	0.24
CV%	15	20
LSD (0.05)	0.7	1.5

Acknowledgements

We are very grateful to Ato Addisse Nuramo and Ato Seyoum Bediye for running the chemical analysis of the feed samples.

References

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