Utilization of rice straw on small farms in Egypt

A. M. Nour
Department of Animal Production
Faculty of Agriculture, Alexandria University, Egypt

Summary
Introduction
Materials and methods
Results and discussion
References

Summary

This study was undertaken to improve the feeding value and quality of rice straw by adding molasses or molasses and urea, or ensiling with urea or sodium hydroxide (5% NaOH) with or without supplementation using a concentrate mixture. Four rams were used in the digestibility trials.

The results show that the feed intake of rice straw when fed alone was very poor but it increased significantly with the addition of 5% molasses. Addition of urea and molasses enhanced feed intake more than the addition of molasses alone. The values were 2.17, 1.43 and 1.13% of the bodyweight of the animals respectively.

The digestion coefficients of DM, OM, CP, EE and NFE were also significantly increased by addition of molasses and urea. An even better improvement in the digestion coefficients was achieved by ensiling rice straw with either urea (5%) or NaOH (5%).

The feeding values (on DM basis) in terms of TDN % were respectively 38.7, 39.7, 44.3, 56.3, 60.2, 49.0 and 55.9 for straw (untreated), treated with molasses, treated with molasses and urea, ensiled with urea, ensiled with urea and mixed with concentrate mixture, ensiled with NaOH, or ensiled with NaOH and mixed with concentrate mixture. DCP was very low with rice straw, with or without molasses (0.07%), and was improved by the addition of 2% to 3.77% urea and greatly improved if ensiled with or without supplementation with a concentrate mixture. The percentage improvements in the TDN % over the control (rice straw alone) were 2.6, 14.5, 45.5, 55.7, 26.7, 44.6% for straw (untreated) with molasses, molasses and urea, ensiled with urea, ensiled with urea and supplemented with concentrates, ensiled with NaOH and ensiled with NaOH and supplemented with concentrates respectively. The cost of one tonne of TDN from rice straw alone was about LE 97.25 and for the different treatments costs were LE 96.65, 92.32, 79.36, 85.29, 107.96 and 102.43 LE, respectively. This indicates that ensiling rice straw with urea greatly increases its feeding value and decreases the cost of one tonne of TDN, even compared with rice straw alone.

Ensiling rice straw with urea can be recommended as a suitable method for the treatment of rice straw on small-scale farms in Egypt.

Introduction

Millions of tonnes of lignocellosic material are going to waste every year in Egypt. Most of it collects as unavoidable byproducts around industrial sites (sugar mills, wineries, canning factories, etc) or comes from cereal production and foliage residues. These materials are of low digestibility to ruminants and have a low nitrogen content. Consequently, they have a low animal production potential. Straws are a poor livestock feed. Rice straw is no exception. It contains about 80% potentially digestible substances and is therefore a source of energy. However, its actual digestibility by ruminants is only 45 to 50%. Furthermore, the amount the animal can eat is limited to less than 2% of bodyweight because of the slow rate at which it is fermented in the rumen (Jackson, 1978). Methods for chemically treating straw have been known for a long time (Jackson, 1978). Of the chemicals used, sodium hydroxide is neither cheap nor easy to obtain in Egypt at the present time. Known methods of ammonia application are technically not feasible under small farm conditions owing to poor roads and the difficulty of obtaining polyethylene.

Oji and Mowat (1979, personal communication) have found that urea can be broken down to ammonia in maize stover containing 55 to 65% dry matter. Gadre (1979) showed a 71% increase in the intake of digestible dry matter in wheat straw treated with 4% urea for 1 month in a small cement silo when fed to growing crossbred heifers. In Egypt, urea is available to all farmers and is used as a fertilizer. It is cheaper than sodium hydroxide (126 and 250 LE/t respectively).

The present work was carried out to study the effect that rice straw ensiled with urea or sodim hydroxide would have on the feeding value of straw-containing diets for sheep.

Materials and methods

Preparation of the ensiled rice straw

Rice straw was chopped with a J.F. machine to a length of 5-10 cm and then divided into three equal portions. The first was kept in dry form and the second ensiled, after the addition of 5% urea in water, with the moisture content being raised to 65%. The third portion was sprayed with 5% caustic soda and ensiled after adding water to raise the moisture content of the silage to 65%. Plastic sheets were used to cover the bottom and the top of the trench cement silos. After one month the silage was mixed with 5% molasses if the rice straw had been ensiled with urea, or with 5% molasses and 2% urea if the rice straw had been ensiled with NaOH or left without treatment.

Digestibility trials

Four mature cross-bred Rahmany rams of c. 60 kg liveweight were used in the digestibility trials. The animals were fed the following diets:

1. Rice straw alone;

2. Rice straw plus 5% molasses;

3. Rice straw plus 5% molasses and 2% urea;

4. Rice straw ensiled with 5% urea and supplemented with 5% molasses before feeding;

5. Rice straw ensiled with 5% urea and supplemented with 5% molasses plus a limited amount of concentrate mixture (0.380 kg/head/day) before feeding;

6. Rice straw ensiled with 5% sodium hydroxide and supplemented with 5% molasses and 2% urea before feeding;

7. Rice straw ensiled with 5% sodium hydroxide and supplemented with 5% molasses and 2% urea plus a limited amount of concentrate mixture (0.380 kg/head/day) before feeding.

All the feeds were mixed with 1% calcium carbonate, 1% common salt, 0.1% trace elements and 0.1% vitamin mixture before feeding. The animals were kept in individual pens and were fed the treated or untreated rice straw ad libitum. Water was available at all times. Each digestibility trial consisted of a 21-day preliminary period followed by a 7-day collection of total faeces and urine. Samples of feeds and faeces were analysed for the proximate composition using the AOAC (1970) method. Statistical analysis was made according to Snedecor (1956).

Results and discussion

The chemical analysis of the food ingredients used in the present experiment is shown in Table 1. Rice straw alone contained 3.98% crude protein and the addition of molasses did not increase the protein content. However, the addition of 2% urea increased the protein content to more than 8%. Ensiling rice straw with either urea or sodium hydroxide decreased the crude fibre content relative to that in the untreated rice straw.

Table 1. Chemical analysis of feed ingredients used in the digestibility trials.

	Dry matter %	% of DM
		CP	EE	Ash	CF	NFE
Rice straw	91.08	3.98	1.36	16.42	34.89	43.35
Rice straw treated with 5% molasses	90.77	3.84	1.09	16.71	32.42	45.94
Rice straw treated with 5% molasses and 2% urea	90	8.62	1.23	16.57	36.37	36.63
Rice straw ensiled with 5% urea plus 5% molasses	68	9.05	1.52	17.73	29.08	42.62
Rice straw ensiled with 5% NaOH plus 5% molasses and 2% urea	72	8.82	0.88	21.60	28.85	39.85
Concentrate mixture	91.40	17.40	3.72	6.95	16.58	55.35

Table 2 shows the effect of the different additives (molasses and/or urea) and treatments (ensiling with urea or NaOH) and supplementation with concentrate mixture on the feed intake, digestibility coefficient and nutritive value of the rice straw. The results show that the intake of rice straw when fed alone was very poor but the addition of 5% molasses significantly increased the feed intake. Addition of urea and molasses enhanced feed intake more than the addition of molasses alone.

The addition of molasses to the rice straw slightly increased the digestibility coefficients for DM, OM, EE and NFE, though the differences were not significant (Table 2). The content of TDN was not improved by the addition of molasses. On the other hand, urea addition significantly increased the digestibility of DM, OM, CP and EE and also improved the nutritive value (DCP % and TDN %). A diet of unsupplemented rice straw is not adequate to maintain animals. They lose weight if no supplementary protein is given (Jackson, 1978) because this material contains less than 4% crude protein and a level of approximately 6% is needed to prevent weight losses. It has been reported that urea treatment of straw increased its digestibility and nitrogen balance (Dolberg et al, 1981). Ensiling the rice straw with either urea or sodium hydroxide in the present study slightly decreased the intake of straw relative to the intake of unensiled supplemented material. However, the differences were not significant. On the other hand, it was found that ensiling the straw significantly increased the digestibility of DM, OM, CP, CF and NFE relative to untreated straw. The nutritive value was greatly improved by ensiling, and ensiling with urea significantly increased the TDN relative to that for straw ensiled with NaOH. Addition of the concentrate mixture to diets containing ensiled rice straw increased the values for DCP % and TDN %.

In Eastern Europe, urea was used in industrial plants for the production of straw pellets about 10 years ago (Bergner et al, 1974). In Bangladesh, Dolberg et al (1981) treated rice straw with 5% urea and ensiled the material for 10-20 days. They found an increase of 8-12 percentage units in organic matter digestibility in vitro. In the present work, the urea treatment increased organic matter digestibility by about 13 percentage units in vivo. These results show a highly significant difference in feed intake of more than 79% between ensiled and untreated rice straw. Gadre (1979) showed a 71% increase in digestible dry matter intake in wheat straw, when the straw was treated with 4% urea for 1 month in a small cement silo and fed to growing crossbred heifers.

The results show that the addition of a limited amount of concentrates (0.380 kg/head/day) improved digestibility coefficients and the nutritive value of the diets. However, the differences were not significant. Rice straw ensiled either with urea or NaOH showed significant improvement in nutritive value relative to the untreated rice straw, but there were no significant differences between rice straw ensiled with urea or with NaOH for this parameter.

Oji and Mowat (1979, personal communication) reported that urea can be broken down to ammonia in maize stover containing 55 to 65% dry matter. Abou-Raya et al (1983) reported that boiling rice straw in water or in 0.1, 0.2 or 1% Ca(OH)2, or spraying the straw with 16% NaOH, significantly increased its nutritive value.

Table 2. Effect of different additions and treatments on the intake. coefficients of digestibility and nutritive value of rice stray.

		Feed No.*
		1	2	3	4	5	6	7
Feed intake (kg DM/day)
	Rice straw	0.68+.03c	0.86+.05b	1.30+.15a	1.22+.16a	1.07+.13a	1.16+.14a	1.30+.18a
	Concentrate mixture	-	-	-	-	0.38+.00	-	0.38+0.0
Digestibility coefficients (%)
	Dry matter	40.88+8.71c	43.52+6.52c	56.81+2.5b	69.17+3.93a	71.64+4.93a	69.97+6.68a	72.55+5.6a
	Organic matter	45.05+7.93c	47.63+6.0c	63.44+2.21b	71.80+3.86a	74.72+4.88a	71.43+6.11a	73.99+5.3a
	Crude protein	0.29+.12c	0.22+.05d	33.60+7.55b	70.94+6.60a	66.51+6.96a	65.39+6.9a	64.86+4.5a
	Ether extract	13.26+3.45d	32.32+3.60c	75.84+5.82b	75.52+3.31b	80.18+3.49ab	84.15+3.0a	80.02+8.87ab
	Crude fibre	48.07+3.82c	42.38+2.41d	48.93+9.4c	63.34+4.24b	70.36+5.04a	49.64+7.3c	61.34+8.4b
	Nitrogen free extract	49.53+5.1c	54.75+7.0bc	58.63+4.2b	69.58+4.28a	73.30+5.34a	68.31+8.0a	70.20+5.77a
Nutritive value (X)
	Digestible crude protein	.07+.08d	.07+.05d	3.77+.69c	7.83+.59b	10.84+.78a	6.70+.62b	11.56+.56a
	Total digestible nutrients	38.66+5.3c	39.68+4.85c	44.28+2.64bc	56.25+2.98a	60.18+4.61a	48.98+4.90b	55.91+4.55ab
% improvement in TDN		-	2.6	14.53	45.50	55.66	26.69	44.62

* See text.

Ensiling straw with 5% urea was not very successful under Norwegian conditions, but when a small amount of soybean meal was added to the treatment as a source of urease, the digestibility of urea treated straw increased. Low temperature (10-15°C) was found to be a limiting factor (Sundstol, 1983). In Egypt, it has been found that the coefficients of digestibility for rice straw treated either by ensiling or with alkali were rather higher than those of untreated material. Furthermore, ensiling rice straw, treated or untreated, caused a clear improvement in its nutritive value (Nabawia et al, 1983). The present results also show that ensiling rice straw greatly improves its nutritive value.

Table 3 shows the cost of the test treatment for rice straw and the governmental concentrate mixture. The results show that ensiling rice straw with urea greatly decreases the cost of one tonne of TDN even when some 25% of the diet was provided in a concentrate mixture (diets 4 and 5).

Table 3. Cost of the tested treatments of rice straw.

Diet No.	Cost of feed ingredients (LE)*						Total cost LE/tonne	TDN %	Cost of 1 t TDN
	Rice straw	Concentrate mixture	Molasses	Urea	NaOH	Minerals & vitamins
1	35	-	-	-	-	2.6	37.60	38.66	97.25
2	35	-	0.75	-	-	2.6	38.35	39.68	96.65
3	35	-	0.75	2.53	-	2.6	40.88	44.28	92.32
4	35	-	0.75	6.30	-	2.6	44.65	56.26	79.36
5	25.90	17.42	0.75	4.66	-	2.6	51.33	60.18	85.29
6	35.0	-	0.75	2.53	12.0	2.6	52.88	48.98	107.96
7	26.95	15.41	0.75	1.94	9.62	2.6	57.27	55.91	102.43
Concentrate mixture

Calculated on the basis of the following prices (LE/ton):

1. Rice straw	35 (including 5 LE/t for chopping)
2. Concentrate mixture	67
3. Molasses	15
4. Urea	126
5. Sodium hydroxide	250
6. Minerals and vitamins	(limestone 15; common salt 15; vitamins 2000; minerals 30.)

Finally, the ensilage of rice straw with urea (5%) can be recommended as a suitable method for improving the nutritive value of this material on small scale farms in Egypt. The suggested method uses urea, which is available on all farms, is cheaper and safer to apply than NaOH and increases the N and TDN content of the straw.

References

Abou-Raya A K, Abou-Hussein R R. Shalaby A S and Salem O A, 1983. Nutritional and physiological studies with short time alkali-treated roughages. Second African workshop on Utilization of low quality roughages with special reference to developing countries. University of Alexandria, Egypt.

AOAC, 1970. Association of Official Analytical Chemists. Official methods of analysis. 11th edition. Washington DC.

Bergner H. Zimmer H J and Garmo J. 1974. Ontersuchungen zur charakteristerung von strohpellets G. verdaulich-keitsuntersuchungen an weizenstrohpellets. Archiv. Tierernahr. 24:689-700.

Dolberg F. Saadullah M, Haque M and Ahmed R. 1981. Storage of urea-treated straw using indigenous material. World Animal Review: 37-41. FAO, Rome.

Gadre L R. 1979. A study of urea as a source of ammonia for treating straw to increase its digestibility. Thesis, University of Agriculture and Technology, Patnagar.

Jackson M G. 1978. Rice straw as livestock feed. In: Ruminant nutrition, World Animal Review: 34-40. FAO, Rome.

Nabawia Esmaile, Abaza M A, El-Shazly N and Naga M A, 1983. The nutritive value of ensiled alkali treated rice straw for fattening rams. Second African workshop on Utilization of low quality roughages with special reference to developing countries. University of Alexandria, Egypt.

Snedecor G M, 1956. Statistical methods applied to experiments in agriculture and biology. 5th edition. Iowa State College of Agriculture, Ames, Iowa.

Sundstol F. 1983. Ammonia treated straws as feed for ruminants. OECD workshop, Grasslands Research Station, Hurley, UK, 16-17 February, 1983.