Discussion I

The importance of agricultural residues as potentially useful feed materials is not in question. There are, however, other factors to be considered in assessing the extent to which this potential could be realized. One is the distribution of the residues. Could small quantities in scattered locations be transported easily or economically enough to justify their processing? It is evident that any method of treating them will have to be within the technical competence of the rural communities, but, to be accepted, it would also need to be in harmony with the social structure.

Certain residues are already being used in Indonesia, as discussed in papers that follow. Processing of residues, particularly microbial processing, can introduce problems of nutritional and toxicological acceptability. No hard and fast rules could be laid down as to how these should be dealt with. Various options are open, and the choice will depend on prevailing circumstances.

The utilization of agricultural by-products and wastes in Indonesia

M. Rangkuti and A. Djajanegara

Animal Husbandry Research Institute, Agency for Agricultural Research and Development, Ministry of Agriculture, Ciawi, Bogor, Indonesia

Introduction
The utilization of some agricultural by-products
The value of some agricultural by-products
Future research objectives
References

Introduction

Crop residues occur fairly generally in the rural areas of Indonesia, but their potential for animal feeding is often not fully exploited. This has important consequences because they form a significant part of the animals' feed. Livestock on the small farm is usually kept for draught purposes or as an investment. In either case, its value is diminished if it is not adequately fed. It is possible to increase the nutritive value of certain of these residues, thus improving livestock productivity.

Research to date has concentrated on determining biological value of residues as they occur rather than on methods of increasing this value. Attempts to improve the nutritional quality of fibrous residues have been confined mainly to physical treatments such as grinding. There is a need to explore and, where possible, apply other methods of treatment if their potential value as animal feed is to be realized more fully.

 The utilization of some agricultural by-products

On the basis of a survey carried out in Indonesia on the availability of agricultural by-products to meet the feed requirement of ruminants in particular, measurements were made in some of the islands of the amounts actually used for this purpose. Sampling was carried out at the farmer's level and the supply of any material that was included in the ration was measured. Production was measured during harvest-time at two different periods in a year and then averaged over the year.

The dry matter (DM) production of agricultural by-products that are generally fed to animals is shown in table 1. This is the average DM production of the total available by-products of the plants harvested and left in the field. The main product is not included. Replanting material is also subtracted, hence it could be regarded as the net available DM from one hectare of each agricultural by-product. Their proximate analysis was also carried out on samples taken at harvest and sent to the laboratory. Applying these figures, the total digestible nutrients were calculated and are shown in table 1.

Of the agricultural by-products, corn straw gave the higher yield of total digestible nutrients (TDN) per hectare. The average levels at which the various residues were used in feeds were determined. From these figures the total amounts used were calculated. These were compared with the total quantities produced in the different islands

Although Java is the most densely populated island and the one with the most livestock, not all of the residues produced there are used. One reason for this is that the areas of livestock production do not always coincide with those in which the residues occur. Consequently, while some areas may use all the residues produced and may need even more, other areas may not use their by-products at all.

In the islands outside Java, the distribution of animals within the agricultural system is more even, and agricultural production is also small relative to animal need. There are areas where these by-products are in excess but the animal population is small. The inefficient use of by-products in some areas could be altered to provide a potential supply to other areas where residues are already totally utilized.

TABLE 1. Production and Utilization of Agricultural By-products and Wastes in Indonesia

	Production (tons/ha)			Percentage Useda
	DMb	TDNc	Java	Sumatra	Kalimanan	Sulawesi	Other islands
Rice straw	2.31	0.96	30	40	50	50	60
Corn straw	6.02	2.74	50	75	75	75	75
Cassava leaves	1.04	0.15	50	75	75	75	75
Sweet potato leaves	1.50	0.17	40	80	100	100	100
Peanut straw	2.70	1.07	40	80	100	100	100
Soybean straw	2.67	1.03	40	80	100	100	100

a. Values indicate the percentage of the total supply on each island which is put to use.
b. DM = dry matter.
c (TDN) = total digestible nutrients.

The size of any centralized unit designed to increase the nutritive value of residues should be in line with the total availability and continuity of supply of agricultural by-products or wastes.

 The value of some agricultural by-products

The nutritive value of agricultural by-products has been measured by various workers. Little or no work has been done to increase their nutritive value by chemical treatment. Chemical composition varied among laboratories and samples. Biological evaluation has been carried out by feeding these materials to animals, usually with the addition of a concentrate supplement. These materials are regarded as low nutritive value feedstuffs, hence the need for the supplementary ration so as to meet the animals' nutritional requirements.

Rice Straw

Rice straw is the main agricultural by-product because rice is the principal staple crop in Indonesia. Rice straw is always available and could be increased in quantity or used more efficiently. The DM and energy content of rice straw is shown in table 1. Its chemical composition varies among samples (table 2), but it is a low-protein, high-fibre material. Sudomo et al. (1) have shown the digestibility of the crude protein of rice straw to be around 30.7 per cent.

The amount of rice straw used in animal rations varies among regions, and Mas Datta et al. (2) have reported up to 58.5 per cent rice straw in daily rations for cattle in the village of Situraja (SumedangWest Java), whereas Sukanto et al. (3) reported the inclusion of the straw at a level of about 37.5 per cent in cattle rations in Playen (Yogjakarta). In Bali rice straw is not generally included in cattle rations. In the rainy season the amount used in feed was only about 2 per cent (4), and even in the dry season its use was not increased. Tahyan et al. have suggested that rice straw could replace up to 25 per cent of "native grass" in feed for sheep (5).

Our results show that buffaloes of 200 kg live weight would consume 15 kg rice straw per day if given ad libitum, but this is not a sufficient intake to meet requirements.

Corn Straw

Corn straw is the second agricultural by-product obtained in rural areas. The yield in DM and (TDN) and the percentage used are shown in table 1. The yields of various components of maize are: grains, 35 per cent; husk and skins, 30 per cent; cobs, 30 per cent; and skin trimmings, 5 per cent. About 6.2 tons of DM per hectare from corn straw are produced during harvest-time. The soft stalks are generally fed to animals, while the tougher parts are composted or burned. The ash is then ploughed into the land. The chemical constituents of corn straw are: cellulose, 40 per cent; pentosans, 25 per cent; and lignin, 35 per cent. It has been used for paper production or to make various types of board.

TABLE 2. Proximate Analysis of Some Agricultural BY-products (Percentage Dry Matter)

	Source	Dry Matter	Crude Protein	Crude Fibre	Ether Extract	Nitrogen-Free Extract	Ash	Calcium	Phosphorus
Rice straw	LPP	-	3.93	33.00	0.87	39.77	22.44	-	-
	Sv	-	3.92	26.51	1.95	40.03	22.01	0.42	0.40
	Toha	-	2.51	46.50	0.55	34.20	18.20	-	-
Corn straw	Sv	-	10.51	29.48	2.94	36.62	13.34	0.38	0.50
	Lubis	-	3.3	20.20	0.70	31.40	4.4	0.18	0.36
Cassava leaves	20.35	8.95	30.92	1.46	47.93	10.74	0.67	0.36	-
Peanut straw	Sv	-	13.10	-	2.62	-	20.54	-	-
Sugar cane tops	27.92	5.65	35.83	1.44	49.32	7.77	-	-	-

Corn cobs have short fibres and might be a good feed for ruminants. When cobs are used for fattening cattle, the addition of a suitable concentrate mixture is necessary. With a concentrate mixture of approximately 16.6 per cent crude protein (consisting of fish meal and soybean meal as major protein sources), an average daily gain of 813 9 per head for Onggole cross-breeds and 648 9 per head for Madura cattle was obtained (6). Corn straw fed to cattle with a mixture of urea and molasses could only supply enough nutrients for maintenance.

Cassava Leaves

Few studies on cassava leaves have been made. The young leaves are collected and sold for human consumption, and some are also fed to animals. The stems are generally used as replanting material or, when in excess, as an energy source.

Rice Bran

Large quantities of rice bran are used for livestock feed in all locally produced concentrates at a level of up to 20-25 per cent. Up to 5 kg rice bran per day are also fed to dairy cows, and it is often used for pig and poultry feed. It is estimated that 80 per cent of the total rice bran production is used for animal feeding, leaving 20 per cent for human use.

Sugar Cane

In sugar cane plantation regions, cane tops represent a potential source of forage for ruminants. Such feed has 6 per cent crude protein, 37.4 per cent crude fibre, 41.9 per cent nitrogen-free extract, and 2.4 per cent ether extract with a dry matter content of 29.3 per cent.

Sugar cane tops have been fed to cattle in or near sugar cane regions in Central and East Java, although their biological value was not determined before use. Cane tops increased the feed intake and growth rate of weaned Bali cattle to a greater degree than when the animals were fed elephant grass (Pennisetum purpureum). Feed conversion efficiency was improved in the ration with sugar cane tops (table 3).

Poultry Litter

Until recently, poultry litter has been used in Indonesia as a fertilizer, not as a feed ingredient, though its use in feeds has now started. The litter is composed of poultry manure mixed with feathers, spilt feed, and bedding material that may be chaff, sawdust, chopped straw, or hay. It has the following average compostion: dry matter, 88.3 per cent; crude protein, 14.2 per cent; crude fibre, 20.2 per cent; ether extract, 0:8 per cent; calcium, 11.5 per cent; and phosphorus, 0.54 per cent.

At one time it was feared that the drugs used in poultry feed would inhibit the activity of rumen micro organisms if the litter were fed to cattle, but this does not seem to be so. It has been shown that up to 60 per cent of the concentrate ration of dairy heifers can be replaced by a mixture of poultry litter and rice bran without adverse effects on rate of growth or state of health.

For lactating dairy cows, rice bran could be replaced by poultry litter in an amount equal to 45 per cent of the total intake. This had no adverse effect on the average daily milk yield; however, there was a tendency for milk output to decrease when higher replacement levels were used.

Remarks

By-products from agriculture are generally used in Indonesia in the state in which they occur, there being little or no attempt made to increase their nutritive value by applying the knowledge already available to do so.

There is a need for more research on the nutritive value of a number of agricultural residues and on methods of increasing the efficiency with which they are used by various types of livestock.

The problem remains in certain areas that the localities in which crops are produced do not coincide with those in which livestock are raised.

TABLE 3. Feed Intake, Feed Conversion Efficiency, and Live-Weight Gain of Weaned Bali Cattle Fed Rations Containing Elephant Grass or Sugar Cane Tops for Four Weeks

	Elephant Grass	Sugar Cane Tops
Feed intake (kg/day)
dry matter (DM)	2.6	3.4
organic master (OM)	2.3	2.9
Feed conversion efficiency
DM required/leg gain	13.1	11.2
OM required/kg gain	11.4	9.8
Live-weight gain, 4-week total (kg)	4.7	7.1

Source: Lembaga Penelitian Peternakan, Bogor, Indonesia. 

Future research objectives

1. A more detailed knowledge of the composition of organic residues is needed.
2. The most appropriate methods for increasing their nutritive value for different classes of livestock should be investigated. These may involve physical, chemical, or microbial treatments either singly or in combination.
3. The methods adopted must be suitable for use by rural communities or individual farmers.
4. Their effectiveness and limitations must be determined and demonstrated to those who will use them.
5. If no appropriate method for producing a feed material emerges for a particular residue, consideration should be given to its potential as a substrate for biogas production.
6. The technologies developed must be transferred to the villages and to the farmer, due regard being paid to the socio-economic problems that will be encountered in doing so.

References

1. Sudomo et al., "Nilai makanan limbah pertanian untuk ruminansia," Seminar penelitian den hasil penelitian penunjang pengembangan peternakan tradisional (1979).

2. Mas Datta et al., "Kualitas den juantitas ransum tradisional pada peternakan sapi potong," Seminar penelitian den hasil penelitian penunjang pengembangan peternakan tradisional (1979).

3. Sukanto et al., "Status gizi sapi-sapi induk di Playen den Cangkringan, Jogyakarta," Seminar penelitian den hasil penelitian penunjang pengembangan peternakan tradisional (1979).

4. Sudana et al., "Makanan sapi Bali waktu musim hujan," Seminar penelitian den hasil penelitian penunjang pengembangan peternakan tradisional (1979).

5. Tahyan, U., et al., "Pengaruh penggantian rumpus lapangan segar dengan jerami padi kering dalam ransum terhadap pertumbuhan domba," Seminar penelitian den hasil penelitian penunjang pengembangan peternakan tradisional (1979).

6. Rangkuti et al., Bulletin Lembaga Penelitian Peternakan (1973).

7. Toha Sutardi, "Intensitas pencernaan pada kerbau," Proceedings Seminar Ruminansia, Bogor, Indonesia (1978