It seems clear that olive by-products represent a considerable but insufficiently exploited feed resource potential for the Mediterranean Basin. Whether these by-products be different forms of olive cake, olive leaves and branches, or vegetation waters, each one has a nutritive value which, although small, should certainly not be neglected.
Interesting research studies have been or are now being made to obtain better valorization of these by-products for animal feeding. Considerable results have been presented throughout the present study which enable the future to be viewed fairly optimistically. These by-products can and should be more and better used in animal feeding.
Considerable research and extension work must still be done to reach that objective. The following recommendations are proposed for that purpose:
It is recommended that harvest residues and olive by-products used in animal feeding be accurately defined in order to avoid confusion and incorrect interpretation of results.
This terminologyproblem is often the source of the failure to understand publications when they are read. The definition given in paragraph 1.4.1 should help to provide better knowledge of these feeds; they should be harmonized with those used in different international fora if necessary. These definitions should be supplemented with such data as the percentage of residue oil or ether extract and crude fibre in olive cake and the percentage of wood in olive branches so that these materials can be characterized better.
As for their use as animal feed, detailed recommendations which could apply to all countries cannot be made. However, it is possible to recommend the general use of olive by-products (leaves and olive cake in all forms) bearing in mind that these by-products should be considered as crude ligno-cellulose feeds comparable to cereal straw or a poor quality hay.
In cases of shortage periods all types of olive cake can be recommended in survival rations, although none of them can make intensive production possible. Depending on the type of olive cake, it is possible to ensure maintenance of the animals or a moderate production level. However it is preferable to incorporate 8 to 10 percent molasses to facilitate olive cake consumption (see Table 17).
It is important that olive cake be preserved in conditions preventing their degradation by using them fresh or ensiling them (in stack silos) within three or four days after they have left the oil extraction mill when they have not been dehydrated by the oil extraction process.
It is difficult at present to recommend chemical treatment to improve the nutritive value of olive cake or leaves and branches, although the anhydrous ammonia treatment seems promising.
On the other hand, partly destoning olive cake by screening or ventilation can be recommended. This is the most practical, simplest and most economic method at present, and one of the most effective for improving the feed value of olive cake. Its crude fibre content should then barely exceed 15 percent of dry matter.
In regions where furfural production is planned, it is recommended that shells be separated at each refinery rather than at the furfural plant. This, while decreasing transport costs, will improve the quality of olive cake and facilitate its availability by keeping it nearer to stockraising centres.
Olive tree leaves and branches constitute a fodder of exceptionally high quality (which is higher as the proportion of wood is lower). It is recommended that the leaves be used preferably fresh, since their nutritive value is higher than that of leaves which have been dried or preserved by ensilage.
Separation of the leaves from the wood whenever possible is also recommended.
Since experimental conditions are not always clearly defined making it often difficult and sometimes impossible to interpret results, it is recommended that an in-depth study be made based on the same initial lot of olives according to a detailed experimental protocol including various industrial processes, the phases of which will be previously described.
In each phase analyses and experiments are to be made to characterize and study each respective by-product (fatty or crude olive cake, partly destoned fatty olive cake, exhausted olive cake, partly destoned exhausted olive cake, pure pulp, vegetation waters).
This type of study requires the joint efforts of research institutes, universities, managers of the olive oil industry, and olive producers themselves. This should be possible in some countries or regions where olive production is especially important.
In view of the complex character of these by-products, laboratory or on-station studies must be made, including:
specific chemical analyses including the Van Soest analysis;
digestibility studies (in vitro, in situ, in vivo);
evolution of microbial flora;
rapidity of fermentation;
degradability of crude protein and organic matter;
voluntary intake;
feeding behaviour.
It is now well recognized, especially for this type of by-products (as it is also for straw or sugarcane bagasse, for example) that the nutritive value expressed in terms of metabolizable energy or of traditional feed units, whatever they may be, has little significance. It is therefore recommended that nutritive value be expressed in terms of production performance (e.g. daily weight increases, milk production).
It is therefore necessary to increase studies on animals, by:
using the more economically important animals (sheep or goats) and preferably the young growing animals (lambs or kids) after weaning, or adult ewes or female goats (pregnant or nursing), but including cattle in the areas where they are more numerous.
For scientific value to be acceptable, each experiment must, in particular:
include in the ration a sufficiently high proportion of the by-product to be studied (if possible as much as 60 to 80 percent of the total ration);
have a minimum duration of 90 days;
cover a sufficient number of animals (varying according to the type of control: individual or by lots respectively).
It is also recommended to increase experiments with various supplements, especially protein, energy and mineral supplements, and with a small supply of good quality fodders (berseem, lucerne, etc.)
As preliminary results are encouraging it is recommended that experiments on the use of partly destoned - by screening or ventilation - olive cake be continued.
On the other hand, experiments on chemical treatment do not seem to have priority at present due to the necessary investments, operating costs, and results in terms of improved animal production which are not always convincing.
Bearing in mind the very small number of references on the use of vegetation waters in animal feeding it is recommended that the experiments begun, especially in Italy, be continued either with vegetation waters alone or combined with olive cake to make vegetation water paste.
Concerning olive leaves and branches, observation must be continued to define characterization and quantification of pruning residues according to type of olive plantation, pruning season and method, olive tree varieties, etc.
It is also recommended that the work recently undertaken in Spain be continued, particularly on methods of collecting, handling and separating olive branches and leaves to lower the whole cost of the process of channelling these by-products from the field to the animals, especially when the latter cannot consume them on the spot.
Research similar to that recommended for the study of olive cake nutritive value should be undertaken to determine the nutritive value of olive leves and branches.
In particular, as the influence of the preservation method on nutritive value has been shown, it is recommended that work be continued on different preservation methods (sun-drying of branches, separation and drying of leaves, ensilage, etc.)
Obviously olive and animal production are complementary to some extent. Since this complementarity has not been exploited to its maximum potential, it is recommended that a complete study be made on the olive plantation ecosystem, closely associating animal and olive production to the reciprocal advantage of both. The purpose will not be necessarily to maximize animal production level, but to make better use of available resources.
