P. Talamucci, A. Pardini & G. Argenti
Department of Agronomy and Land Management
University of Florence, Italy
Mulberry is native to the temperate areas of Asia, where it was first planted for sericulture, to feed the silkworm. Its uses were however then extended to firewood, timber, windbreaks, live fences, shade for food crops and forage for cattle and sheep in specialized plantations (ICRAF, 1999).
Today, mulberry is cropped as a multipurpose tree in Europe and temperate Asia, as well as in subtropical and tropical climates, including the tropical highlands of Africa, especially the United Republic of Tanzania and Kenya (Mbuya et al., 1994; Boschini, 2000).
Mulberry is an important component of combined pastoral systems oriented towards regularization of seasonal forage availability and diversification of pastoral resources (Talamucci, Pardini and Piemontese, 1990; Talamucci et al. 1996; Talamucci and Pardini, 1999). Both these aspects are important for the variability of land use and consequently for the conservation of biodiversity, and thus for the sustainability of production. Interest in this tree species is due particularly to its plasticity of use, good palatability, chemical composition and productivity.
Early mulberry introduction in Italy was for silkworm feeding and for tutoring vines. More recently its use has been attempted in some farms with mixed cattle-sheep husbandry where it is planted under the alley cropping system, which has been known in the Mediterranean Basin since the times of the Roman Empire and is associated with grasses or sown pastures of annual legumes (Talamucci and Pardini, 1993; Talamucci, Pardini and Argenti, 1997). The cattle feed on the upper part of the branches and the sheep graze the sward and the lower leaves of the trees. These systems do not resolve completely the problems of forage availability for both species throughout the year: in winter cattle have difficulty in grazing the pasture because it is too short, and in summer sheep have difficulty in getting leaves from the tallest branches. With this system, both animal species require supplementation in the critical seasons, with hay or silage produced on farm or purchased. Furthermore, livestock numbers are being reduced in Italy due to the European Union policies, and farmers prefer to specialize in sheep. Some have even preferred to change over completely to wildlife for hunting or tourism. Sheep require a pastoral system with green forage easily available in summer. Such a system is largely used elsewhere (Nair, 1993), where leaves are made available by lopping trees weekly throughout the summer.
The aim of this research was to compare traditional and alternative management systems of mulberry (M. alba) and their effects on animal diets in Central Italy.
MATERIALS AND METHODS
Twelve hectares of M. alba cv. "Kokuso" associated with Trifolium subterraneum cv. "Woogenellup" plus T. brachycalycinum cv. "Clare" were established in a private farm in central Italy with fertile alluvial soils. Several experiments were conducted on that association and data were recorded for twelve years. The present article refers to data collected in the last trial in a mature plantation, carried out between 1996 and 1999.
Mulberry plants were micropropagated and planted in October (northern autumn) in rows 5 m apart with 3 m within rows. The mixture of subterranean clovers was sown soon after at the rate of 30 kg/ha. Reseeding was carried out every four to five years.
The following treatments were compared in the association:
All interactions were investigated, using fenced sectors in a split-plot design. Animals grazed all through the year, and were supplemented with hay when forage availability was not sufficient to satisfy their estimated needs. The sheep grazed all through the year and the cattle only browsed the upper leaves beyond the reach of sheep in summer. The cattle were kept in different pastures for the rest of the year.
Two rows of mulberry were lopped at the beginning of the week, in the sectors with the summer cutting treatment, for a period of 90 days. There were 20 rows of mulberry per treatment. Non-grazed lines were utilized for measurements.
The cattle were Chianina, a local tall and strong breed, resistant to extreme climates and well adapted for extensive grazing. The sheep were Sarda, a milking type breed very common in the area. The mean annual stocking rate was 1.0 livestock unit (one adult cow of 500 kg or six sheep of the above breed).
Measurements:
RESULTS AND DISCUSSION
Dry matter production (Table 1)
Mulberry
On average, sheep and sheep plus cattle allowed higher leaf yields (9.5 and 9.3 tonnes/ha-1 respectively) than cattle alone (8.5). There was probably more than one reason for this. Sheep caused less stress to mulberry shrubs because they are shorter and ingest fewer leaves than cattle. They also competed with cattle and reduced their intake when grazing together. Moreover, sheep consumed more clover than cattle due to their grazing habits. This higher clover intake reduced competition with the shrubs. Spaced rows and good soil fertility suggest that the strongest competition was for water.
Mulberry yields in plots browsed by cattle were significantly higher with the winter cutting than with the summer cutting. This difference was probably due to the complete removal of leaves and branches in the summer. Mulberry shrubs might have mobilised root reserves to overcome this damage to allow regrowth during the autumn. Reserves were then not available for the early growth in the spring.
After the winter cut, root reserves are utilized for early spring growth. They are replenished by the summer and can maintain vegetative activity in autumn. The autumnal vegetation is maintained by using only part of the root reserves and remain available for regrowth after the winter cut.
Sheep had the same positive effect on the mulberry cut in winter. This was probably because the shrub regrows well after the winter cut and sheep are able to consume only the leaves in the lower part; this happens especially in summer when the animals are hungry but most of the leaves are too high. Thus, stress is reduced to winter only and nutrients are stocked again in the roots during the following spring. On the contrary, nutrients are not stocked in the root system if mulberry is cut in summer and the trees have a late and slow regrowth in spring.
Grazing with mixed species does not result in forage production that is significantly different from only sheep grazing. In fact the cattle do not care much for tree leaves while there is abundant and green pasture.
On average, the winter cut gave higher yields of mulberry leaves compared to the summer cut. This was probably due to the longer period left for the plants to form new reserves after the last stress. Summer harvesting can reduce plant survival. The cutting season did not significantly affect clover yield.
The results of the interaction between the two analysed parameters (cutting season and grazing species) given here.
TABLE 1
Mean dry matter production (tonnes/ha) of mulberry and clovers
|
|
Mulberry |
Clovers |
Total |
|
Cattle Winter cutting |
9.5b |
5.5c |
15.0c |
|
Cattle Summer cutting |
7.5c |
4.5c |
12.0d |
|
Sheep Winter cutting |
10.5a |
7.5b |
18.0a |
|
Sheep Summer cutting |
8.5b |
8.5a |
17.0ab |
|
Cattle+sheep - Winter cutting |
10.3a |
6.3b |
16.6b |
|
Cattle+sheep - Summer cutting |
8.2bc |
7.9a |
16.1b |
Values having different letters are significantly different (P < 0.05).Subterranean clover
Clover yields were higher when mulberry shrubs were cut in winter than in summer since the availability of green leaves due to the summer cut reduces the ingestion of clover seed and allows the plant to last longer.
Subterranean clover yields were small when cattle grazed because cattle only graze this plant efficiently when it tall enough. The cattle return to the area already grazed after a minimum period of two weeks, when the clover grown back. This sort of self-controlled rotational grazing causes senescence of the green tissues in the lower layers of the sward canopy and, in turn, reduces photosynthetic efficiency.
Sheep stimulated higher pasture production than cattle; the intensive grazing favoured the young and more efficient plant tissues. Sheep also favoured seed production, crop persistency and productivity in the following years. Clover productivity was higher with the summer cut.
The combination of cattle and sheep allowed yields very similar to those with sheep only. This suggests that the impact of sheep on the shrubs was stronger than that of cattle under the experimental conditions.
Total dry matter production
Total yield was favoured by the presence of sheep that grazed the clover intensely and did not cause stress to the shrubs.
Forage availability (Table 2)
Forage availability in the critical season was differed according to cutting season and plant species. Mulberry availability was zero in winter and maximum in summer. Clover was available in good quantity in winter and a minimum was also present in summer as stalks and seeds. Forage availability of the association was more balanced than the two separately.
Biomass intake (Table 3)
Mulberry
Mulberry intake leaves only was higher with cattle (6 tonnes/ha, average of cutting season) and sheep + cattle (5.5 tonnes/ha) than with sheep only (4.7 tonnes/ha). Animal height made the difference. Differences in mulberry intake were not significant throughout. Only sheep on shrubs cut in winter had lower intakes (2.3 tonnes/ha). Mulberry intake was influenced by cutting season and animal species.
TABLE 2
Forage availability in winter and summer (percentage of total production)
|
|
Mulberry |
Clover |
Total |
|||
|
Winter |
Sum. |
Winter |
Sum. |
Winter |
Sum. |
|
|
Cattle - Winter cutting |
0 |
25 |
10 |
4 |
10 |
29 |
|
Cattle - Summer cutting |
0 |
20 |
11 |
3 |
11 |
23 |
|
Sheep - Winter cutting |
0 |
74 |
14 |
2 |
14 |
76 |
|
Sheep - Summer cutting |
0 |
60 |
12 |
1 |
12 |
61 |
|
Cattle+sheep - Winter cut |
0 |
13 |
13 |
1 |
13 |
14 |
|
Cattle+sheep - Summer cut |
0 |
14 |
10 |
1 |
14 |
15 |
TABLE 3
Total, mulberry and subterranean clover intake (tonnes). Percentage of ingested biomass on total production
|
|
Mulberry |
Sub-clovers |
Total Intake |
% intake |
|
Cattle - Winter cutting |
6.5a |
2.5c |
9b |
60b |
|
Cattle - Summer cutting |
5.5a |
2.2c |
7.7c |
64b |
|
Sheep - Winter cutting |
2.3b |
6.5b |
8.8bc |
49c |
|
Sheep - Summer cutting |
7.0a |
7.6a |
14.6a |
86a |
|
Cattle+sheep- Winter cut |
4.5a |
5.3b |
9.8b |
59b |
|
Cattle+sheep-Summer cut |
6.5a |
6.7a |
13.2a |
82a |
Values having different letters are significantly different (P < 0.05). The statistical analysis of values expressed in percentages was preceded by angular transformation according to Bliss.Subterranean clover
Clover intake was proportional to leaf yields. Intake was influenced by animal species, but not correlated with the mulberry cutting season.
Total intake
Total intake was higher with branches cut in summer with sheep (86 percent) and with cattle + sheep (82.0 percent). Maximum waste of leaf forage was on shrubs cut in winter with sheep (48.9 percent).
CONCLUSIONS
Larger variability of climatic parameters caused by global climate changes will influence the reliability of yields. Increased diversification of resources will become more important, especially in forages, because of their higher sensitivity to climatic variations compared with other crops.
Higher diversification will imply more complex management of pastoral systems. The simplest grazing technique should be defined for each resource in order to simplify management. For the same reason, the number of species reared in each farm should be reduced.
Mulberry might be interesting as a strategic resource for dry summer periods while subterranean clover could be used for the winter. The results of this trial show that simplifications in management can be achieved by summer cutting and, contemporarily, by sheep grazing only.
The cutting season may influence mulberry growth, thus leaf yield and, in turn, subterranean clover yields. The winter cut increased mulberry production and reduced subterranean clover. Cutting season will be less important in farms where both cattle and sheep are kept. Winter cutting should be chosen when plantation survival is of primary importance and summer cutting when higher forage is sought.
Cattle benefit if shrubs are cut in winter. However, sheep have greater intake if shrub branches are lopped in summer. Mixed herds are the best users, but imply a more complicated management.
Further investigations could contribute to resolving questions such as plantation persistence. Since yields were reduced with summer cutting this could suggest higher plant stress and possible reductions in shrub life.
BIBLIOGRAPHY
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