CHAPTER III: OLIVE LEAVES AND BRANCHES

The use of olive tree leaves and branches in animal feeding can encounter a number of problems which Alibes and Berge (1983) summed up as follows:

1. leaves and branches are scattered over the land
2. cattle are not always near olive plantations
3. for reasons of plant pathology, it may be necessary to eliminate branches from the olive plantations quickly
4. transport costs increase the final cost
5. preservation of leaves presents problems
6. the feeding value of the final product is low

However, leaves and branches are traditionally used fresh in many countries and can be a substantial fodder resource.

3.1 Physical characteristics

There is no specific identification of olive tree branches distributed for feeding ruminants. However in the specialized literature they usually seem to be referred to as branches of less than 3–4 cm in diameter.

However, one must distinguish between leaves collected at the oil mill (para. 1.4.1) which have a small proportion of wood, and branches on which the proportion of wood can be considerable. According to Civantos (1981 a and b), on branches less than 4 cm in diameter the proportion of leaves is about 50 percent.

In most countries pruning wood is given freely to animals who obviously prefer to eat leaves and small twigs in proportions which are hard to determine. In Spain large scale work has been conducted for collecting and conditioning pruning wood with special machines (Civantos, 1981 b and 1982; Parellada et al, 1982) which also allow separation of the leaves from the wood.

3.2 Preservation

Since harvesting and pruning are seasonal, it may be useful to consider preservation of leaves and branches so as to spread consumption over a longer period. Two methods can be used, i.e. drying or ensilage.

For leaves collected at the oil mill, Nigh (1977) compared preservation by air drying and by ensilage. Manual air drying decreases the bitterness of the leaves and produces an odour like that of fresh hay. However leaves should not be dried too much because then they lose their palatability. However this method requires a great deal of attention and work and is difficult to apply. Ensilage in vertical silos without preservants also removes the bitter taste but the quality of the product has proved to vary considerably depending on conditions of execution. Nevertheless the ensilage method has seemed preferable to drying. It should be pointed out, however, that a simple stock silo would certainly afford as good a preservation as a costly vertical silo.

Maymone et al (1950) obtained a satisfactory silage (PH = 4.2 for 23 percent DM); nevertheless leaf and branch ensilage tests made in Spain by Vera and Vega and Galan Redondo (1978), even using preserving substances, has apparently produced poor results. Parellada et al (1982) have also described different forms of ensilage (some of them including moist materials); however the available data are incomplete. According to Alibes and Berge (1983) doubts are raised as to the feasibility and usefulness of ensiling this type of harvest residues due to the following factors:

1. their high dry matter content;
2. their low density and the difficulty of eliminating oxygen sufficiently by stacking them;
3. insufficient fermentable sugars;
4. the structure of the product (since the wood pierces the plastic sheeting covering them).

Lastly, the fact must be seriously considered that Mediterranean olive plantations are located in dry climates and consequently natural drying would seem to be the most logical method.

As has been mentioned previously, large-scale work has been undertaken in Spain for collection and separation of leaves in dry form. This mechanized method is still costly but deserves further study.

The branch-lopping operation should not be delayed more than 8 days after pruning in order to prevent loss of the leaves. In normal conditions (absence of rain), between time of cutting (when leaves contain 50 percent dry matter), piling, lopping of branches, transport and separation of leaves from branches by ventilation, a dried state can easily be obtained sufficient for good preservation (87–92 percent DM). The leaves can then be conditioned to obtain higher densities and decrease transport costs (Parellada and Gomez-Cabrera, 1983).

3.3 Chemical composition

The chemical composition of leaves and branches depends on many factors (olive tree variety, agro-climatic conditions, season when the sample was taken, and lastly, the different treatment applied).

Source: Adapted from Alibes and Berge, 1983; many sources cited.

In general these different by-products have relatively homogeneous and well-defined characteristics:

• the dry matter in green leaves comes to about 50 percent, that in dry leaves about 90 percent;

• their total crude protein content is low, i.e. 7 to 8 percent in dry or ensiled leaves, slightly higher in green leaves;

• their ether extract content of about 6 percent is higher than that of traditional fodders;

• their crude fibre content is variable and relatively small;

• their cell wall constituents increase considerably with wood percentage, especially lignecellulose contents lignin level seems to be stable at 18 to 19 percent.

The crude protein content seems to be less in branches than in green leaves and is comparable to that of dry leaves. Naturally the crude fibre content is markedly higher than that of leaves.

3.4 Nutritive value of leaves and branches

3.4.1 Digestibility

The first tests made in Italy (Maymone et al, 1950) showed that drying and ensilage of olive tree leaves caused a considerable decrease in the digestibility of dry matter, organic matter and crude protein (Table 19)

More recent studies conducted mostly in Spain to measure digestibility of different types of leaves and branches are summarized in the following table:

* In vitro digestibility; in other cases: in vivodigestibility.

Source: Adapted from Alibes and Berge, 1983; many sources cited.

The digestibility of dried branches compared to green branches seems slightly lower for dry matter and organic matter and much lower for crude protein.

The results obtained in vitro on green or dried leaves may have been distorted by the fact that the green leaves should have been oven-dried before evaluation since the substantial differences obtained by Maymone et al (1950) were not found in them. On the other hand, the influence of the proportion of wood combined with the leaves was reflected by a marked decrease of digestibility. This is shown clearly in Figure 6. Moreover, in vivo digestibilities of crude protein are very low and even negative.

Figure 6: Evolution of in vitro digestibility of olive branch dry matter according to wood percentage (Alibes et al, 1982)

3.4.2 Intake

Olive tree leaves distributed fresh during the winter season are usually consumed willingly by animals without any problem of adaptation, even over a long period.

However station experiments made sometimes had very different results. For example Boza et al (personal communication) working with goats in metabolic cages obtained voluntary intakes of:

• 80 g DM/kg^0.75with fresh leaves

• 71 g DM/kg^0.75with dried leaves

Whereas Alibes et al (1982) and Gomez-Cabrera et al (1982), using dried leaves (more or less contaminated) on sheep obtained intakes of 42 g and 23 g DM/kg^0.75 respectively

Some authors (Gomez-Cabrera et al, 1982) reported problems of twig accumulation with unseparated dried leaves in the third stomach of cattle. However no such problem was observed with separated leaves.

Distributing dried leaves ad libitum Gomez-Cabrera et al (1982) increased the intake from 23 g to 45 g/DM/kg 0.75 when they added a sunflower meal supplement. Alibes et al (1982) also observed increased intake when olive leaves distributed to sheep were supplemented with 18 percent barley and 1.5 percent urea in the ration.

3.5 Treatment to improve nutritive value of leaves and branches

3.5.1 Mechanical treatment

In the light of the results shown in Figure 6 it seems clear that separating the leaves from the wood constitutes a very effective treatment for improving digestibility of olive tree branches. Work now being done in Spain should lead to development of practical methods that can be applied on the farm.

3.5.2 Alkali treatment

Tests of alkali treatment of dried leaves by Alibes et al (1982) have mostly been disappointing (Table 21). In the case of soda treatment the effect on digestibility has even proved negative. These authors believe that with this type of fodder, containing less than 50 percent of cell wall constituents and about 20 percent lignin, the action of the soda could not be as effective as on cereal straw (containing 80 percent cell wall constituents and less than 10 percent lignin).

With anhydrous ammonia treatment, in spite of an increase of about 10 percent in crude protein, the effect was not more noticeable either on digestibility or on the sheep intake level.

In Italy, Martilotti and Danese (1983) also compared the effect of alkali treatments on olive branches crushed and preserved during 60 days in 25-litre plastic recepticles. The results shown below are somewhat more promising.

The effect on in vitro digestibility of treated crushed olive branches was very positive, especially when ammonia and soda were used together, as the effect of ammonia seemed to be greater besides considerably increasing the digestible crude protein content.

The same authors repeated this experience, treating 5–6 ton stacks of crushed branches enclosed under a polyethylene sheet with two doses of anhydrous ammonia during 40 days.

The results are summed up in the table below:

These results obtained in conditions which can be reproduced on the farm seem highly positive and comparable to those obtained previously in the laboratory.

3.6 Use of leaves and branches in animal feeding

As has been mentioned previously leaves and branches are traditionally distributed to animals either at the trough or in the field in olive-producing regions. It is difficult to estimate the percentage reserved for this use and it varies considerably from one country to another. In any case, ad libitum distribution ro ruminants presents no special problems except that of the low nutritive value of this fodder.

Very few real experiments have been conducted in this field. Nigh (1981) reported that at the Kolymberi Centre in Crete olive leaves collected at the oil mill were distributed fresh (less than 2 days old) at a rate of 15 kg/day to Holstein cows. Zoiopoulos (1983a) observed that the distribution rate of such fresh leaves now comes to 30 kg/d in two meals. Similar quantities are distributed in silage form after the harvesting season. Although specific scientific control trials were not made, the author mentioned that there was a positive effect on milk production. Fresh leaves are also distributed sometimes to sows.

Fresh leaves and twigs were distributed to sheep and goats in Greece at rates of 6 percent of liveweight as the only fodder, and up to 10 percent to rabbits (Kalaisakis, 1975). However Zoiopoulos (1983a) suggests that for ruminants the optimum level would be 2.5 percent of liveweight.

In Spain Muñoz et al (1983), studying ad libitum rations of dried leaves distributed to lambs weighing 36 kg, with a supplement of barley and added fishmeal protein (230 g/lamb-day), obtained weight gains of 77 g/d compared to only 40 g with urea, while the control lot receiving lucerne hay and 200 g barley obtained a weight increase of 154 g/d in a period of 90 days.

For dried leaves, Alibes et al (1982) recommend utilization comparable to that of poor/ quality roughage such as straw, that is, with a protein supplement, a small readily fermentable energy supply, and a mineral supplement.

The situation would be more advantageous with fresh leaves, especially for goats (Boza et al, personal communication).

3.7 Conclusions

To sum up, it can be assumed that digestibility of organic matter is acceptable with fresh olive leaves compared to average quality fodders. However, with dried leaves the quality decreases and becomes comparable to that of cereal straw. When the wood percentage is relatively high the value decreases even further becoming lower than that of ordinary cereal straw.

The protein value of fresh leaves is very low and of dried leaves practically none.

Intake levels remain relatively low but can be improved by a small addition of protein and energy supplement.

Mechanical treatment allowing separation of leaves from wood markedly improves their use as feed.

The few experiments with alkali-treated dried leaves have had no significant effect, whereas with olive tree branches collected fresh and alkali-preserved a marked improvement of in vitro digestibility has been observed.

Unfortunately, few animal feeding trials have been made to be able to judge statistically the effects of incorporation of olive leaves and branches in rations on animal production (milk or meat). But their use presents no practical problem.

In any case, to achieve production levels, it would seem that a rational use of olive leaves and branches according to their location and nutritive value would be to make up rations where they are freely distributed to animals supplemented with grazing fodders or other locally available fodder resources.

Animal and olive production should therefore be integrated as has been done traditionally in many regions of the Mediterranean Basin. Such integration would be profitable to both the animal and plant sectors. The animals would valorize by-products which constitute a low-cost feed but which would otherwise be wasted, while olive plantations in turn would receive the benefits of an organic fertilizer of which their soils are often badly in need.