Prospects for efficient utilization of agro-industrial byproducts and crop residues for ruminant feeding in the Sudan, with emphasis on quantification, nutritional composition, constraints and research results

Mahgoub G. El Hag and Omer I. Kurdi
Department of Animal Nutrition
Institute of Animal Production, University of Khartoum
P O Box 32, Khartoum North, Sudan

Summary
Introduction
Results and discussion
Conclusion
References

Summary

Sudan possesses a huge animal wealth of about 23 million animal units. Pasture and range provide about 85% of the national feed resources; agro-industrial byproducts and crop residues contribute about 11% and cereal grains and forages about 4%.

Pasture and range resources have been seriously reduced by drought and desertification. Consequently, better use of residues and byproducts must be encouraged.

A survey indicated that more than 7 million t of residues and byproducts were produced annually over the last four years, consisting of cereal straws (sorghum and wheat), sugar-cane (molasses and bagasse), groundnut hulls and haulms, and the oilseed cakes of cotton, sesame and groundnuts. Field residues are mainly from sorghum and cotton.

Constraints on the use of residues and byproducts include: bulkiness, location in areas with lower animal population density, unsuitability for direct animal use and poor nutritive value.

Sorghum straw and groundnut hulls, each at 25% of the ration, supplemented with 20% molasses and 1.75% urea, gave excellent results for fattening beef cattle and sheep and appeared to be as good as conventional high grain rations. Cost of feeding was decreased. Both poultry manure (20% of the ration) and urea (1.5-1.75%) were effective in rectifying the nitrogen deficiency of the residues and byproducts used in this study. Physical treatment was more effective and economically feasible than treatment with sodium hydroxide.

Introduction

Agriculture is the major source of income in the Sudan. There are differences in agro-climatic zones, soil types and available water resources. Within arable farming, the major cash crops in Sudan are cotton, sesame, groundnuts, cereals (mainly sorghum, wheat and millets) and sugar-cane, which are raised under both irrigated and dry farming systems. A total of 7 million t of crop residues and agro-industrial byproducts (AIBP) are produced annually from these and other crops. Unfortunately, very little use has been made of these feed resources.

The more than 55 million head of cattle, sheep, goats and camels (over 23 million animal units) in the Sudan are raised mainly on pasture and range, which form the major livestock feed resource and provide about 85% of the total nutrient requirements of these animals. Of the remaining 15%, AIBP contribute about 11% and forages and concentrates about 4% (Kurd), 1984).

However, in recent years drought and desertification have greatly reduced the potential DM yield of pasture and range. Full and efficient use of AIBP has to be promoted for feeding animals in the Sudan.

The objectives of this study were to:

* Quantify the different types of AIBP and assess their nutritive value;
* Identify constraints facing the use of AIBP for feeding ruminants in the Sudan;
* Enhance the nutritive value of AIBP by molasses and NPN (urea and poultry excreta) supplementation as well as by chemical and physical treatments.

Results and discussion

Types, amount and use of agro-industrial byproducts in the Sudan

Agro-industrial byproducts in the Sudan consist of cereal straws (sorghum, wheat, rice and millet), sugar-cane byproducts (molasses, bagasse and sugar-cane tops), oil seed cakes (sesame, cotton and groundnut), groundnut haulms and hulls, and fruit wastes (e.g., banana). The most important ones are cottonseed cake and sorghum straw (El Hag, 1984).

The estimated 7 million t of DM of AIBP produced annually in the Sudan provide approximately 3 million t of TDN (Table 1). The greater proportion of these byproducts is wasted (burnt or allowed to rot) rather than utilized as animal feeds. Partial use is made of AIBP, mainly during the critical summer period (March to July). Burning of AIBP (as the quickest way to clear land and control pests) poses a potentially serious environmental hazard.

Only a tiny proportion of the molasses available in the Sudan has been used for alcohol production and for feed manufacturing in the newly established feed mills in Khartoum Until recently, the majority of molasses was disposed of in nearby rivers.

Problems limiting the use of agro-industrial byproducts as feeds in the Sudan

The major problems facing the use of agricultural byproducts for animal feeding in this country include:

* Bulkiness of byproducts and their availability in areas with lower animal population density;

* Poor infrastructure and the high cost of transport;

* Availability of byproducts in forms not suitable for direct animal use;

* The general lack of understanding among livestock owners about the feeding value of byproducts;

* The relatively poor nutritive value of most AIBP.

Table 1. Production of agro-industrial by-products in the Sudan (1980-84) and their TDN (in 1000 tonnes).

Item	Seasons				Ave. prod. in 4 yrs.	TDN*
	80/81	81/82	82/83	83/84
Sorghum straw	2481.6	3932.4	2325.6	2182.8	2730.6	1447.2
Ground nut hulls	282.8	335.2	196.8	183.2	249.5	84.8
Ground nut residues	424.2	502.8	295.2	274.8	374.3	228.3
Cotton residues	229.6	372	466.4	530.4	399.6	195.8
Cotton gin trash	401.8	651	816.2	928.2	699.3	293
Millit stalks	392.8	407.2	272.8	251.2	331	140.7
Wheat straw	174.4	97.6	112.8	129.6	128.6	52.2
Wheat bran	32.7	18.3	21.2	24.3	24.1	14.9
Bagasse	1046.3	1184.8	1662.3	1836.6	1433	415.6
Molasses	86.1	119.5	141.3	164.2	128.5	82.2
Sugar-cane tops	189.6	139.9	219	254.1	200.7	80.3
Totals	6186.9	8244.7	6855.6	7167.4	7113.7	3200.8

* Values were calculated according to N.R.C. (1975).
Source: Ministry of Agriculture and Irrigation, Department of Statistics (1984).

Nutritive value and nutritional deficiencies of agro-industrial byproducts in the Sudan

Samples of the important and most abundant AIBP in the Sudan were collected from different locations and analysed for proximate composition (AOAC, 1965), cell wall constituents (Goering and Van Soest, 1970), and in vitro dry matter disappearance (IVDMD) (Tilley and Terry, 1963).

Chemical analyses show that AIBP were deficient in CP, high in CF and lignin and poor in IVDMD. Since most of the AIBP were poor in CP and readily fermentable carbohydrates, most of our research focussed on the following:

* Supplementation of AIBP with molasses and NPN (urea and poultry excreta) for sheep and beef cattle used in growth trials;

* Chemical (NaOH) and physical (grinding and pelleting) methods for improving the nutritive value of some selected AIBP.

It is well documented that utilization of NPN is enhanced by molasses supplementation. Molasses is one of the cheapest sources of energy and is available in relatively huge quantities (Table 1).

The usefulness of supplementing low quality AIBP (groundnut hulls, bagasse and sorghum straw) with both NPN (urea and dried poultry excreta) and molasses was demonstrated in studies with both sheep and cattle (Table 2).

The data show that AIBP, particularly sorghum straw and groundnut hulls, when used as basal diets and supplemented with urea and molasses, can give animal performances comparable to conventional (high grain) rations, and that molasses can be used effectively at up to 20% of the ration and urea at up to 1.75% (as fed basis). Bagasse seemed to be a rather poor byproduct and its level should probably not exceed 30% of the ration. At higher levels, such as 50%, bagasse was just adequate for maintenance purposes. The cost of feeding decreased by more than a third with the incorporation of byproducts and urea-molasses supplementation.

From these results it could be concluded that for fattening of both sheep and cattle in the Sudan, byproducts should not exceed 30% of the ration. Urea and molasses can be used effectively up to 1.75% and 20% of the ration respectively.

The results of another study (Table 3) showed that dried poultry excreta (DPE) was very effective as a source of NPN, was used successfully in replacing cotton seed cake (CSC) protein, and even improved animal performance compared to (CSC). The cost of feeding decreased by about 50% by using DPE. However the overall performance of sheep on both DPE and CSC-supplemented rations was relatively poor and was due to the low TDN content of both rations. The poor TDN value was ascribed to the high level of groundnut hulls (GNH) in both rations. This again supports our belief that agricultural byproducts in fattening rations should not exceed 30%.

Table 2. Performance of Sudan desert sheep and beef cattle on rations containing variable levels of AIBP supplemented with urea and molasses.

Ingredients (%) (as fed)		Conventional high energy rations		Byproducts based rations
				C	D3	E	F
Sorghum grains		50	50	15	15	20	20
Cotton seed cake		15	49	-	-	20	15
Wheat bran		19	-	30	30	20	5
Alfalfa hay		-	-	7.5	7.5	-	-
Sorghum straw		-	-	24.75	-	-	-
Groundnut hulls (GNH)		-	-	-	24.75	-
Bagasse		-	-	-		30	50
Molasses		-	-	20	20	8	8
Urea		-	-	1.75	1.75	1.5	1.5
Common salt		1.0	1.0	1.0	1.0	0.5	0.5
Total		100	100	100	100	100	100
Nutritive value (DM basis)
	% CP	15	16	14.8	12.7	13.7	9.5
	% TDN	82	80	75	71.5	54	47.0
Animal performance (sheep)
	Days on test	75	-	-	75	75	75
	Feed intake (DM) g	1280.8	-	-	1314.6	1175	948
	Daily gain (g)	160.8	-	-	148.5	55	1.1
	Feed/gain	7.97	-	-	8.85	21.0	862
Animal performance (beef)
	Days on test	-	67	67	67	-	-
	Feed intake (DM) kg	-	9.83	8.74	8.58	-	-
	Daily gain (kg)	-	1.22	1.12	0.66	-
	Feed/gain	-	8.06	7.8	13.0	-	-
	Cost/kg of the ration (LS)	0.16	0.21	0.12	0.12	0.13	0.10

Rations A and B are high energy rations based on 50% sorghum grains.
Ration C was based on 24.75% GNH.
Ration D was based on 24.75% sorghum straw.
Ration E was based on 30 % bagasse.
Ration F was based on 50 % bagasse.

Table 3. Performance of Sudan desert sheep on variable levels of AIBP supplemented with dried poultry excreta (DPE) and molasses.

Ingredients %		Cotton seed cake supplemented ration (% DM)	Dried poultry excreta supplemented ration (% DM)
Wheat bran		29.0	29.0
Dried poultry excreta		-	20.0
Cotton seed cake		20.0	-
Groundnut hulls		40.0	40.0
Molasses		10.0	10.0
Salt		1.0	1.0
Total		100	100
Nutritive value
	% CP	15.0	16.2
	% DCP	9.5	10.6
	% TDN	57.5	56.6
Sheep performance
	Feed intake (DM) g	1054.6	1295.6
	Daily gain (g)	46.6	65.3
	Feed/gain	24.2	19.8
	Cost/kg gain (LS)	1.10	0.53

Research results with NPN and molasses-supplementation demonstrated the effectiveness of urea and DPE, and molasses in rectifying CP and energy deficiencies respectively. The cost of feeding decreased by more than a third.

Improvement of the feeding value of agricultural byproducts by chemical and physical methods

1. Chemical treatment (NaOH)

The effects of NaOH were studied using both wet (soaking) and spray methods with variable levels of the alkali. It was found that spray method at levels of 7-11% of the substrate (w/w) were the best. With the soaking method there was a very high DM loss (9-25%) in the treated byproduct.

Kurkedi (Hiscus sabdrifa) a local malvaceous plant, used as a beverage in the Sudan, was found to have a very acidic pH (2.4) at 1% cone (w/v). Owing to its low pH, kurkedi was evaluated as a neutralizing agent for the NaOH-treated byproducts for both laboratory and field trials. By-products were sprayed with a 1% solution of Kurkedi.

Feeding trials were carried out using NaOH-treated byproducts.

a) Groundnut haulms

In this study, three rations based on 55% (DM basis) groundnut haulms (GNH) were compared with a standard high grain ration in a feeding trial using growing sheep. One of the GNH rations was treated with 11% NaOH; the second treated with 11% NaOH and then sprayed with kurkedi solution at 1% (w/v), and the third was fed without any treatment (control). There were five sheep per treatment and the trial lasted for 90 days.

The composition, nutritive value, digestibility and animal performance are summarized in Table 4. Animal performance was depressed due to NaOH and kurkedi treatments. Chemical treatment depressed the DM intake dramatically (36%) in relation to the control. However NaOH treatment slightly enhanced both DM and CF digestibilities. The NaOH treatment increased the total ash content of the ration and consequently decreased the OM content and this has been reflected in a low DM intake and poor animal performance on the NaOH-treated GNH. Therefore there was no benefit due to NaOH or NaOH-kurkedi treatment of the GNH.

Table 4. Effects of NaOH and kurkedi on feeding value of GNH-based rations.

Item		High grain ration	GNH treated with NaOH	GNH treated with NaOH + kurkedi	Control untreated GNH
GNH (% DM)		-	55	55	55
Sorghum grain		55	15	15	15
Wheat bran		15	-	-	-
Alfalfa hay		14	-	-	-
Cottonseed cake		15	12	12	12
Molasses		-	15	15	15
Urea		-	2	2	2
Salt (Nael)		1	1	1	1
Total		100	100	100	100
Proximate composition
(DM basis, %)
	OM	91.0	85.4	85.4	92.2
	CP	15.5	15.4	16.4	14.4
	CF	11.4	23.6	25.8	25.3
	Ash	9.1	14.7	14.6	7.85
	TDN	75.5	44.8	45.1	47.4
Digestibility (%)
	OM	76.9	48.5	48.0	46.2
	CP	79.5	74.0	79.4	79.8
	CF*	50.3	33.4	35.4	22.0
Animal performance
	DM intake (g)	1212	860.6	859.0	1353
	Daily gain (g)	137.0	-30.0	-35.3	28.5
	Feed/gain	8.8	-	-	47.5
	Price/kg (LS)	0.2	0.13	0.13	0.10

* Significant improvement in CF digestibility (P<0.05) due to NaOH and kurkedi treatments.

b) Sorghum straw

The poor performance of sheep on the NaOH-treated GNH was due to the high level of NaOH (11%) and the originally poor quality of the GNH (high content of lignin and crude fibre). Accordingly, sorghum straw was chosen as a substrate for NaOH treatment and the level of the alkali reduced to 7% from 11%.

In this trial three rations were based on 50% (DM basis) of sorghum straw. One ration was fed as a control without any treatment, the second was treated with 7% NaOH (w/w) and the third treated with 7% NaOH and then sprayed with kurkedi solution 1% (w/v). The three rations were fed to three groups of growing

Sudan Desert sheep, with eight animals per treatment. The experiment lasted 75 days. Digestibility and animal performance data are summarized in Table 5.

Table 5. Effects of NaOH and kurkedi treatment of sorghum straw on nutrient digestibility and sheep performance.

Item		Control ration 50% sorghum straw	50% sorghum straw treated with 7% NaOH	50% sorghum straw treated with 7% NaOH + kurkedi
Composition of the rations (% DM basis)
	Sorghum straw	50	50	50
	Molasses	15	15	15
	Sorghum grains	20	20	20
	Cotton seed cake	12	12	12
	Urea	2	2	2
	Common salt	1	1	1
	Total	100	100	100
Proximate composition (% DM basis)
	OM	88.5	86.8	85
	CP	11.2	11.1	11.0
	CF	16.3	15.3	15.0
	Ash	11.5	13.2	14.96
Digestibility (coefficients %)
	OM	65.5	69.5	66.9
	CP	67.9	71.0	67.0
	CF*	42.4	51.8	44.5
	TDN %	59.2	61.7	59.4
Animal performance
	DM intake (g)	860.5	995.9	890.5
	Daily gain (g)	7.2	36.75	20.5
	Feed/gain (g)	119.5	27.0	43.4
	Cost/kg (LS)	0.12	0.145	0.146

* Significant effect due to treatment (P<0.05).

There were no observed differences in the chemical composition of the rations due to the treatment. However, the ash contents of the treated rations were slightly higher than those of the control.

NaOH treatment significantly (<0.05) improved CF digestibility, unlike kurkedi which had no effect. However, in general, NaOH treatment tended to improve the digestibility of all the proximate components. This resulted in an increased TDN content of the NaOH-treated straw. Both NaOH and kurkedi rations increased feed intake, gain and efficiency of feed conversion. NaOH and kurkedi treatments had no effects on palatability of the rations. In conclusion, both NaOH and kurkedi improved animal performance beyond that obtained from untreated sorghum straw, which provided only sheep maintenance requirements.

2. Physical treatment (grinding and pelleting)

The grinding of fibrous materials increases the surface area exposed to microbial attack and accelerates the rate of flow of digesta through the gastro-intestinal tract. This results in a higher intake, up to 30% more (Kay, 1972). Pelleting increases feed intake and improves feed/gain, although the actual mode of action is not fully understood.

Due to the difficulties encountered in chemical treatment of byproducts (high cost of chemical, manual-labour and hazards), and the lack of pronounced animal response, grinding and pelleting (physical treatment) were tried as possible means of improving the feeding value of agricultural byproducts in the Sudan. Bagasse was selected for pelleting and was fed as the basal diet at three levels: 30%, 40% and 50% of the ration DM (rations also contained urea and molasses). Bagasse was fed either as pellets or in ground (unpelleted) form. The main objective was to study the effects of pelleting on digestibility and performance and assess the optimal level of bagasse for fattening sheep. Ration composition, digestibility and animal performance are summarized in Table 6. Pelleting improved palatability, DM intake and digestibility of all proximate components (except CF) at all levels of bagasse. Pelleting also remarkably improved daily gain and the efficiency of feed conversion. The daily gain in sheep fed pelleted bagasse at 50% was as good as the gain among those fed unpelleted bagasse at 30%. Without pelleting, bagasse at 50% provided only maintenance requirements. The overall improvement in feed efficiency at all levels of bagasse ranged from 45% to 100%. Pelleting improved feed intake by more than 20% at all levels of bagasse. Pelleting was more effective than NaOH (previous trial) in improving the nutritive value of agricultural byproducts.

Table 6. Effects of variable levels of bagasse and pelleting on nutrient digestibility and animal performance.

Ingredient % DM basis	Bagasse 30%	Bagasse 40%	Bagasse 50%
Bagasse	30	40	50
Molasses	8	8	8
Sorghum grains	20	20	20
Cotton seed cake	20	15	15
Wheat bran	20	15	5
Urea	1.5	1.5	1.5
Common salt	0.5	0.5	0 5
Total	100	100	100

Physical treatment:		Level of bagasse (% DM basis)
		30		40		50
		Pelleted	Unpelleted	Pelleted	Unpelleted	Pelleted	Unpelleted
Proximate analysis (% DM)
	OM	91.5	91.9	91.0	90.0	90.0	88.5
	CP	13.9	13.7	11.3	11.0	9.7	9.5
	CF	19.0	21.1	21.2	21.8	21.8	25.3
	Ash	8.55	8.02	9	9.59	10	11.5
Digestibility coefficients (%)
	OM	62.4	57	55.4	54.1	53.0	52.5
	CP	69.5	66.6	73.6	59	61.7	67.4
	CF*	31	43.7	26.8	40.9	27.5	41.6
	% TDN	60.6	55.6	53.2	51.1	45.7	48.3
Animal performance
	DM intake (g/day)	1412.3	1175.1	1204.8	1012.8	1261.5	948.1
	Daily gain (g)	122.68	54.8	78.22	46.54	71.23	1.1
	Feed/gain	11.5	21.4	15.4	21.7	17.7	861.9
	Cost/kg (LS)	0.22	0.17	0.2	0.15	0.19	0.14

* Significant reduction in CF-digestibility due to pelleting.

Conclusion

Constraints on the use of AIBP as ruminant feeds in the Sudan include transportation, bulkiness and poor nutritive value. This research has clearly demonstrated that supplementation of AIBP by NPN (urea and poultry manure) and energy (molasses) may successfully rectify protein and energy deficiencies.

The optimum level of byproduct incorporation in fattening rations of sheep and beef in the Sudan should not exceed 30%.

However, for maintenance purposes AIBP can form up to 50% of the ration.

Physical treatment of AIBP proved to be more useful in improving the nutritive value of AIBP and was economically more feasible than chemical treatment.

References

AOAC, 1965. Association of official chemists. Official method of analysis. Washington DC.

El Hag M G. 1984. Use of agro-industrial by-products and crop residues in the Sudan. In: Proceedings of FAO/ILCA Expert consultation 5-9 March 1984. Addis Ababa, Ethiopia.

Goering H K and van Soest P J. 1970. Forage fibre analysis. Agricultural Handbook No 379. Washington DC, USA.

Kay M, 1972. Processed roughage in diets containing cereals for ruminants. Cereal processing and digestion. US Feed Grains Council. London.

Kurdi O I, 1984. Chemical and physical methods for improving the nutritive value of selected agricultural by-products in the Sudan. PhD Thesis. University of Khartoum, Sudan.

Tilley J M and Terry R A, 1963. Two stage technique for the in vitro digestion of forage crops. Journal of British Grassland Society 18:104.