Reports of working groups

Group 1

Topic: The effects of crop improvement programmes on the nutritive value and utilisation of crop residues for feeding ruminants.
(a) Quality

1. Effects of crop improvement programmes on residue quality are probably random. Plant breeders have not, in the past, placed any emphasis on straw and stover quality. This probably applies to all CG Centre programmes and to the NARSs.More examples can be found of crop residue quality being reduced than examples of improved residue quality. However, this is probably only because non-adoption of a new variety due to poor crop residue quality is more noticeable than increased adoption because of better stover or straw quality.
Examples of "improved" varieties with poorer residue quality than locally grown varieties include Beecher barley in the ICARDA region, improved wheats from the Egyptian natural program, and maizes in Mexico.
The only case of a non-random effect on crop residue quality is that of selecting for bird-resistance in sorghum.

2. The following points were considered to be notable by the group:

2.1 In most crop species there is a large range of digestibility and proportions of plant components.2.2 Voluntary intake is an important aspect of crop residue quality and must be considered by crop improvement programmes.
2.3 Chemical treatment of crop residues to improve their nutritive value has not been well accepted because of costs, labour requirements, the need to handle toxic chemicals, and unreliable results.

(b) Quantity
In several major cereals the introduction of dwarfing genes has reduced straw quantity, but this effect may be offset by the greater use of fertilizer on dwarf varieties, which increases biomass yield. However, economic factors will not always allow the use of higher inputs, particularly with lower-value crops on resource-poor farms.
It is only desirable to increase the quantity of residues produced in mixed farming areas. In developed countries, where livestock production tends to be concentrated in regions away from crop production, large quantities of crop residues are undesirable.

Group 2

Topic: Factors that limit the nutritive value of crop residues and research that is needed to define and overcome the limitations in nutritive value
Factors affecting the nutritive value of crop residues

· Level of voluntary intake
· Digestibility
· Animal ability to select leaf material
· Amount on offer
· Anti-nutritional factors

Factors affecting voluntary intake

· Fibre content
· Degradation rate
· Crude-protein content
· Palatability factors

Areas needing research

· Effect of time of harvest on voluntary intake and digestibility of straw· Effects of storage, particularly with respect to termites, rain damage, use of NaHCO₃ under stacks
· Effects of stack construction
· Effects on nutritive value of stress, particularly low soil fertility and drought, and their relationships with phenolics.
· Effect of level of feeding, i.e. what production level represents optimal utilisation of feed resources
· Effect of supplementation with legumes and forages
· Methods for assessing the volume and density of stacks so that the farmer can plan feeding strategies and does not run out of higher quality crop residues because of their higher consumption.
· Evaluation of near-infrared-reflectance techniques, including determination of phenolics and crude protein
· Studies of feed preference and intake
· The NaOH/back titration test for measuring the extent of carbohydrate/lignin bonding needs to be evaluated for different crop species o Investigation of Maillard reactions in rice straw

Group 3

Topic: The effects of increased utilisation of crop residues for feeding ruminants on productivity, income and stability of smallholder farming systems.
Crop residues are very important in smallholder systems but in many cases the existing resources are used to the maximum extent. Therefore emphasis needs to be put on increased yield and quality of crop residues and the use of supplements. The trade-offs between use of crop residues as feed or as fuel and construction materials need examination. The increased use of dung as a fuel and its impact on soil fertility should be examined in relation to other sources of fuel, such as multipurpose leguminous trees. The effects of practices such as leaf stripping on fodder and grain yields need studying.

Group 4

Topic: The influence of the amount and value of crop residues on farmers' decisions to grow improved crop varieties.
These considerations mainly affect integrated crop/livestock systems. The relative importance of crop residues increases with the aridity of the environment. Farmers in higher rainfall areas tend to concentrate on crop production, planting higher-yielding varieties and using more intensive management. Farmers in drier areas tend to derive a greater proportion of their income from livestock and are often adjacent to range areas with substantial livestock populations which may utilise crop residues on a seasonal basis. These generalisations interact with the availability of alternative feed resources and the overall balance of feed resources and livestock numbers.
Crop residues are generally inadequate feed materials and their use in intercropping systems and with supplements needs consideration. However, the adequacy of crop residues as feed depends on the level of production desired, e.g. they may be adequate for non-pregnant, non-lactating animals but unsuitable for production.
Better data are needed on the availability and use of crop residues.
The major aim of crop selection programmes. has been to increase grain yield. More experimental work is needed to determine the effect of this on residue quality. Work to date indicates a weakly negative association between grain yield and residue quality in some crops but the poor correlations indicate the possibility of selecting varieties with both higher grain yield and good residue quality.
Ideally, the digestibility of crop residues should be at least 50% but this may not be practicable for some crops. It would also simplify the task of the plant breeder if dual-purpose varieties could be identified i.e. those with good grain yields under favourable conditions but adequate residue quality in all locations. If this cannot be achieved, separate grain and fodder varieties should be identified.
Digestibility and intake may be affected by particular chemicals, such as phenolics, and these need to be characterised. Chemical and biological indicators of crop residue value need to be improved and refined.

Group 5

Topic: Advantages and disadvantages of using crop residues for feeding ruminants in smallholder farming systems.
Advantages

· Higher whole-farm income
· Higher return to cash and non-cash inputs
· Provides an alternative source of feed to pastures and concentrates
· Allows the maintenance of animals which would otherwise die reducing the farmers assets

However, these advantages accrue only if feed resources are limiting.
Disadvantages

· Do not generally allow the use of genetically improved animals· Mineral deficiencies
· Variable intake and digestibility
· Harvesting, transport and storage problems
· Legumes and/or chemical treatment may be necessary to make adequate use of crop residues. This may affect the availability of land and other resources necessary for food crops.
· Alternative end uses of crop residues, including maintenance of soil organic matter, are important. Increased use of crop residues as feed could increase soil erosion or deforestation.

Recommendations

General statement
The international agricultural research centres (IARCs) and the national agricultural research systems (NARS) should recognise that farmers grow crops not only to feed themselves and their families but also to feed their animals. The rejection by farmers of high-yielding varieties because of their low straw yield or poor quality of straw or stover shows that attention must be paid to residue yield and quality in cereal crops.
Specific recommendations

1. Survey data are needed on crop residue use by farmers. Such surveys should involve both agricultural economists and animal nutritionists and aim particularly at understanding farmer perceptions.2. Collaborative research should study the effects on stability of the farming system of alternative uses of crop residues and manure produced by ruminants fed on crop residues. This should involve crop and animal research institutes and include agroforestry input.
3. Chemical treatment of crop residues has limited applicability to animal production in tropical and sub-tropical countries. Emphasis should be transferred to exploiting genetic variation in crop residue quality.
4. The residues of existing varieties should be ranked in order of nutritive value, such rankings to include comparisons between years and seasons from crops grown at a range of locations.
5. In ranking crop residues, emphasis should be placed on biological methods, either in vitro or in sacco. This should be followed by voluntary intake and in vivo digestibility measurements and production trials. If near-infra-red reflectance is used to rapidly evaluate larger numbers of samples, it should be linked to biological measurements.
6. Chemical and biological methods of selecting crop residues with higher nutritive value need to be improved and refined. The methods chosen need to be compatible with the objectives of the selection process and the type of crop residue.
7. Variation in the nutritive value of crop residues arises from differences in morphological proportions, variation in cell wall digestibilities, differences in residual cell contents (particularly storage carbohydrates) and anti-nutritional factors, including phenolics. Research should be conducted to determine the relative importance of these variables in different crop species.
8. Intake and digestibility of crop residues is affected by anti-nutritional factors, including phenolics, which need to be characterised using techniques such as high-performance liquid chromatography.
9. The existence of a negative correlation between grain yield and crop residue value has not been proved. Further studies are needed on this subject.
10. IARCs should evaluate the nutritive value of crop residues in advanced breeding lines or populations for all their major mandate crops.
11. IARCs should document the nutritive values of crop residues and forward this information along with information on grain yields to the NARSs.
12. NARSs should test the improved lines for their feeding values and supply data on performance to the relevant IARC for adjustment of lines, where feasible, by plant breeders.
13. A link should be established, in countries where it does not exist, to rapidly pass the crops with improved feeding value to the small-scale farmers through extension staff.
14. Methods of storing crop residues need to be examined to prevent the effects of spoilage on deterioration of feeding value. With improved residues, which may be consumed in higher amounts, methods of assessing the quantities present in stacks would aid farmers in developing feeding strategies.

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