- Email: [email protected]
Effect of summer grazing on forage quality of woody and herbaceous species in a silvopastoral system in northern Greece
ARTICLE IN PRESS Journal of Arid Environments
Journal of Arid Environments 67 (2006) 90–99 www.elsevier.com/locate/jnlabr/yjare
Effect of summer grazing on forage quality of woody and herbaceous species in a silvopastoral system in northern Greece A.B. Ainalisa,, C.N. Tsiouvarasb, A.S. Nastisb a
Forest Service, Region of Central Macedonia, 46th Agriculture School St., 551 34-Thessaloniki, Greece b Range Science Laboratory, Aristotle University, 54124 Thessaloniki, Greece Received 18 April 2005; received in revised form 9 January 2006; accepted 19 January 2006 Available online 20 March 2006
Abstract The forage quality of black locust (Robinia pseudoacacia L.), honey locust (Gleditsia triacanthos L.), bastard indigo (Amorpha fruticosa L.) and white mulberry (Morus alba L.), as well as of the associated herbaceous vegetation, was studied in a silvopastoral system. The study was conducted in a semi-arid grassland with poor sandy soil in northern Greece. Short-duration grazing (28 sheep/ha for 7 days) was repeated twice during the summer period (early July and late August) of 1992, 1993 and 1994. Crude protein content of foliage was maintained at relatively higher levels when plants were grazed compared to control, while neutral and acid detergent fibre content decreased significantly. Crude protein content of black locust and bastard indigo foliage was significantly higher compared to that of honey locust and white mulberry. However, white mulberry presented the highest in vitro digestibility among the four species tested. There was a tendency towards increased in vitro digestibility of the grazed plants’ foliage, compared to that of the control (56% and 53.1%, respectively). In addition, short-duration summer grazing resulted in a small increase in the nutritive value and the in vitro digestibility of the associated herbaceous vegetation. r 2006 Elsevier Ltd. All rights reserved. Keywords: Black locust; Bastard indigo; Honey locust; White mulberry; Mediterranean grassland; Silvopastoralism
Corresponding author. Tel.: +30 2310 409347; fax: +30 2310 475656.
E-mail addresses: [email protected], [email protected] (A.B. Ainalis). 0140-1963/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2006.01.017
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
91
1. Introduction Grasslands in the low semi-mountainous zone of Greece occupy 4.2% of the total surface area and much more in the Mediterranean region. The climate is characterized by long dry summers and cold rainy winters. The quantity and quality of herbage production in these grasslands are below the potential, owing to heavy, uncontrolled grazing for many years. After early summer, herbage quality is drastically reduced with plant maturation, because of climatic conditions, leading to malnutrition of the livestock grazing in these grasslands (Nastis, 1982). Many researchers have demonstrated the potential of woody species to produce palatable and nutritious foliage even during the dry season. Many woody species are able to provide green and nutritious forage in summer exceeding qualitatively that of the herbaceous species. They develop long roots reaching deeper soil layers than the herbaceous vegetation, and are able to maintain green phytomass late in the season when the herbaceous layer is dry (Le Houerou, 1987; Olea et al., 1992). The establishment of a silvopastoral system by introducing woody and especially leguminous species into these grasslands could be an effective means of improving the overall forage quality, while ameliorating the supply demand ratio. Several studies have been carried out involving locust species (Robinia sp., hybrid and Gleditsia triacanthos), bastard indigo (Amorpha fruticosa) and bladder senna (Colutea arborescens) (Tsiouvaras and Nastis, 1990; Papachristou and Papanastasis, 1994), alfalfa (Medicago arborea) and blue wattle (Acacia cyanophylla) (Stringi et al., 1987), saltbush (Atriplex halimus), oldman saltbush (A. nummularia), thinleaf fourwing saltbush (A. linearis) and grey desert senna (Cassia sturtii) (Corleto et al., 1992). It is well documented also that woody species significantly help to decrease the risk of soil erosion, improve wildlife habitat, improve the aesthetics of the landscape and enrich the upper soil layer with nutrients (Le Herou, 1993). The objective of this study was to assess the nutritive value of four woody species introduced into a semi-arid grassland at three planting spacings, and of the associated native herbaceous vegetation, as affected by short-duration summer grazing. 2. Materials and methods 2.1. Study area The research was conducted at Scholari village, 43 km east of Thessaloniki, Macedonia, Greece, at an elevation of 90 m and at 401410 north latitude, 231140 east longitude. The long-term average annual rainfall in the area is 512 mm and the mean air temperature 14 1C (Ainalis, 1996). During the dry season (June–September), mean air temperature ranges from 20.9+1.6 to 25.1+1.5 1C and rainfall from 22+22 to 38+40 mm. The climate of the area is characterized as semi-arid with cold winters. The soil texture is sandy to sandy silt, derived from conglomerates of the tertiary period and colluvials from river or torrent bank deposits. The organic matter content (0.97%) and the pH (5.5) are both considered low (Ainalis, 1996). 2.2. Woody species tested The woody species introduced into the grassland were black locust (Robinia pseudoacacia L.), honey locust (G. triacanthos L.), bastard indigo (A. fruticosa L.) and
ARTICLE IN PRESS 92
A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
white mulberry (Morus alba L.). White mulberry is an indigenous species, covering large areas of cultivated land in the past as an important component of silvopastoral systems. Shepherds used to prune young branches to feed livestock. Black locust and honey locust are deciduous leguminous trees, with moderate to high nutritive value foliage and well adapted to semi-arid conditions with cold winters (Le Houerou, 1978; Bonciarelli, 1980). Bastard indigo is a deciduous leguminous shrub, with moderate to high nutritive value and palatability of the foliage and facility of propagation (Stringi et al., 1987). 2.3. Experimental procedure 2.3.1. Experimental layout The experiment was established on a 1.7 ha area of a large mismanaged grassland. The experimental area was fenced and divided into six equally sized plots. Three of the plots were randomly assigned to grazing treatment, while the others were ungrazed (control). Each plot was subdivided into four equally sized subplots, which were assigned at random for planting with one of the four woody species tested. Each subplots was further subdivided into three sub-subplots and randomly assigned to three planting spacings (1.5 1.5 m, 2.5 2.5 m and 3.5 3.5 m, corresponding to: 4440, 1,600 and 810 plants/ha). Plants were one-year old at the time of planting in February 1991. Every year, all plants were topped to a height of 50 cm in December, in order to retain the shrubby form. Cutting annually in winter followed by summer grazing maintains shrubby growth and prevents the plants from spreading beyond the silvopastoral system. Even without this management, the expansion of the above species in natural habitats does not seem to be a problem. They were introduced many centuries ago and they exist in many areas where the seeds are obtained. The system has been employed to ensure sustainable foliage production for grazing (Nehra et al., 1987). The grazing treatment was implemented by introducing 28 sheep/ha for 7 days in early July and for another 7 days in late August. Grazing was repeated for three consecutive years (1992–1994). The grazing system applied was short-duration grazing repeated in time. The sheep flock used in the experiment grazed all day long on the surrounding hills for the rest of the year. The hills are dominated by Quercus coccifera growing in patches associated with herbaceous species in the clearings. 2.4. Nutritive value of browse and herbage Browse samples were taken by hand plugging shoots of o5 mm diameter (Ainalis and Tsiouvaras, 1998). Foliage and herbage production are reported by Ainalis and Tsiouvaras (1998). Samples were collected separately from four grazed and four ungrazed plants of each species, per spacing treatment and per replication. A total of 72 samples of every plant species were collected at each sampling time. In the grazed plots samples were collected: (1) in early July, just before grazing, in order to evaluate whether the previous year’s grazing affected the nutritive value of spring growth foliage; (2) in late August, to evaluate the nutritive value of regrowth after July grazing; and (3) in early October, to evaluate the nutritive value of regrowth after August grazing. In the ungrazed plots samples were collected on the same sampling dates and consisted of fully developed shoots of o5 mm diameter. On every sampling date, samples were collected from unsampled plants.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
93
Herbage samples were collected in late May each year, when most of the herbaceous plants in the area were mature. They were collected by clipping the above-ground biomass at a height of 2 cm above-ground level from three 0.5 0.5 m quadrats per spacing treatment and per replication. The quadrats were randomly placed on permanent transects used for vegetation composition measurements. Composition was determined for three consecutive years by using the ten-point frame method (Heady and Reader, 1958). All samples were oven-dried to 60 1C for 48 h, ground and analysed for crude protein (AOAC, 1990), neutral detergent fibre (NDF) with sodium sulphite and residual ash, acid detergent fibre (ADF) with residual ash, acid detergent lignin (ADL) (Van Soest et al., 1991) and in vitro organic matter digestibility (IVOMD) (Moore’s modification of the Tilley and Terry technique, Harris, 1970). 2.5. Statistical analyses The experimental layout (Steel and Torrie, 1980) was a split–split plot design with three replications (grazing split on woody species; woody species split on spacings). Browse and herbage quality data were subjected to analysis of variance. The least significant difference (LSD) was used for detecting differences (pp0:05) between treatments. 3. Results 3.1. Chemical composition and IVOMD of foliage Average crude protein content of foliage of all tested species was not affected by grazing (Table 1), while neutral and ADF and lignin content decreased significantly (pp0:05) by 12.4%, 13.8% and 18.6%, respectively, compared to the control. By contrast, IVOMD of grazed plants (Table 1) increased significantly (pp0:05) by 10.5% compared to the control. Crude protein and ADF content of black locust foliage was not significantly different (pp0:05) from that of bastard indigo, while that of honey locust was significantly lower than that of the previous two species and that of white mulberry significantly lower than that of all tested species (Table 2). Content of NDF and lignin (Table 2) presented a similar pattern in all tested species, with white mulberry foliage having a significantly lower content than the other species and black locust the highest, while bastard indigo foliage was not significantly different from that of honey locust. By contrast IVOMD (Table 2) of white mulberry was significantly higher than all tested species followed by honey locust, which yielded significantly higher values than both black locust and bastard indigo. No significant differences (pX0:05) were detected in crude protein content of foliage between early July, late August and early October (Table 3). Percentages of ADF and Table 1 Effects of grazing on average chemical composition and IVOMD of foliage of four woody species Grazing treatment
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
Grazing No grazing
17.3 aa 17.0 a
36.7 b 41.9 a
21.8 b 25.3 a
9.6 b 11.8 a
58.7 a 53.1 b
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
94
Table 2 Chemical composition of foliage of four woody species Plant species
Crude protein (%)
Black locust Honey locust Bastard indigo White mulberry
19.3 16.7 18.5 13.8
a
aa b a c
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
45.3 41.3 42.5 31.3
27.2 23.6 26.5 18.3
15.3 a 11.9 b 12.1 b 4.9 c
42.2 56.6 44.8 75.6
a b b c
a b a c
c b c a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
Table 3 Effect of sampling period on average chemical composition and IVOMD of foliage of four woody species Phenological stage
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
Early July Late August Early October
17.1 aa 17.0 a 17.4 a
41.5 a 37.7 b 35.0 b
24.2 a 23.4 a 20.6 b
10.5 a 10.9 a 9.6 b
52.8 c 56.3 b 64.3 a
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
Table 4 Crude protein and IVOMD of foliage of four woody species in the grazing treatments Plant species
Crude protein (%) Grazed
Black locust Honey locust Bastard indigo White mulberry
19.5 16.3 18.7 14.3
a
a a a a
IVOMD (%) Ungrazed
Grazed
Ungrazed
19.2 17.1 18.3 13.4
44.3 a 63.2 a 46.9 a 76.7a
40.2 50.0 42.7 74.5
a a a a
a b a a
a Means of the same category of chemical composition for the same species followed by the same letters are not significantly different at the 0.05 level.
lignin content were significantly lower in early October than in the other two periods (Table 3). Only NDF content was significantly (pp0:05) higher in early July than in late August and early October. By contrast IVOMD was significantly higher in early October than in early July and late August and in late August than in early July (Table 3). Grazing (Table 4) did not affect crude protein content of any of the species tested, but it favoured IVOMD. Honey locust had significantly higher IVOMD than the control (pp0:05). There was a small but non-significant (pX0:05) difference for IVOMD compared with the other tested species (Table 4). A significant interaction (pp0:05) was detected between the sampling time periods and tested species for crude protein content, which, apart from honey locust, maintained an increasing trend towards the end of the growing season (Table 5). IVOMD of honey locust and bastard indigo foliage collected in early October was significantly higher (pp0:05) than in the other periods, while IVOMD of foliage collected
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
95
in late August was significantly higher than in early July (Table 5). Also, IVOMD of black locust and white mulberry foliage collected in early October was significantly higher (pp0:05) than in early July and late August (Table 5). 3.2. Native vegetation composition (%) in the grazing treatments during the 3 years of the experiment In protected plots, there was a tendency over the years for annuals (Fig. 1) to be favoured over perennials. There was a significant increase in both annual grasses and legumes while there was a proportional decrease in perennial grasses and forbs (Fig. 1). 3.3. Chemical composition and IVOMD of herbage Crude protein content of herbage (Table 6), regardless of grazing, increased progressively with the years. During 1993 IVOMD significantly increased and NDF significantly (po0:05) decreased compared to other years (Table 6). Crude protein and Table 5 Crude protein and IVOMD of foliage of four woody species in the three sampling periods Plant species
Crude protein (%) Early July
Black locust Honey locust Bastard indigo White mulberry
19.3 17.4 19.2 12.3
ba a a b
IVOMD (%)
Late August
Early October
Early July
19.0 16.5 18.0 15.0
20.4 15.0 19.0 15.5
40.4 55.6 39.4 75.1
b b b a
a c a a
ba c c b
Late August
Early October
43.3 59.8 48.3 74.0
49.2 74.1 53.0 81.0
b b b b
a a a a
a Means of the same category of chemical composition for the same species followed by the same letters are not significantly different at the 0.05 level.
60.0 Vegetation composition (%)
1992 50.0
1993 1994
40.0 30.0 20.0 10.0 0.0 Annual grasses
Perennial Annual legumes grasses
Forbs
Half- shrubs
Fig. 1. Mean species composition of a silvopastoral system during the 3 years of the experiment.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
96
Table 6 Chemical composition and IVOMD of herbage in a silvopastoral system Years
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
1992 1993 1994
12.2 ca 13.8 b 16.6 a
64.4 a 50.5 c 56.5 b
49.2 a 35.9 c 38.9 b
13.3 a 6.5 c 9.7 b
43.1 c 59.0 a 45.8 b
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
Table 7 Effects of moderate grazing on chemical composition and IVOMD of herbage in a silvopastoral system Grazing treatment
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
Grazing No grazing
13.1 aa 13.2 a
56.2 b 57.5 a
40.6 b 42.6 a
9.6 b 10.1 a
50.7 a 51.1 a
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
IVOMD of herbage were not affected by short-duration grazing, which significantly reduced ADF and lignin content in comparison with the control (Table 7). 4. Discussion 4.1. Chemical composition and IVOMD of foliage There was no evidence that short-duration grazing of woody plants in summer modified crude protein content of foliage, as has been reported by Tiago (1987). This probably occurred because of the high rate of lignification in leaf and shoot cells during summer, even when they develop as regrowth after grazing, because at that time cell walls lignify rapidly so that plants can resist and survive the dry summer period (Benevises et al., 1989; Ainalis, 1996). In contrast, crude protein content increased in early autumn, because the tested species adapted to the lower temperatures and high soil moisture; with corresponding decrease of ADF and lignin content (Papachristou, 1997). The content of ADF and lignin was high in summer as has been reported for many woody species (Tsiouvaras, 1984; Papachristou et al., 1999). Of the tested species, black locust and bastard indigo presented higher crude protein content than the other two species, results similar to those reported by Corleto et al. (1992). The tendency for IVOMD to increase, although not significantly except for honey locust, indicated the high potential of woody fodder plants for summer grazing (Le Houerou, 1978). The very low lignin content as well as the low level of phenolics in white mulberry compared to the three leguminous species (Makkar et al., 1998) probably contributed to the high IVOMD. The phenolics content of the three leguminous woody species is probably high. The foliage of the control plants had higher NDF content than that of the grazed ones, probably owing to the lack of regrowth. Grazed black locust presented high IVOMD, but in any case it was lower than that of white mulberry, probably because of the higher tannin concentration in black locust foliage, which inhibits digestion,
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
97
causing the formation of indigestible tannin–protein complexes (Koukoura and Nastis, 1992; Makkar and Becker, 1998). All tested species, when grazed, had higher IVOMD in early autumn due to regrowth. The relatively high browse quality of the shrubs’ foliage and especially of the regrowth during early autumn was sufficient to meet the animals’ requirements for maintenance and production in the Mediterranean-type environment (Tsiouvaras, 1984; Papachristou and Papanastasis, 1994). 4.2. Chemical composition and IVOMD of herbage Variation of crude protein content of herbage between years was attributed to the modification of the herbaceous species’ composition due to the variation of annual grasses and legumes over the years. When rain coincided with high temperatures in early autumn it was beneficial for legumes (year 1994). However, the significant increase of IVOMD observed in 1993, was mainly attributed to the higher May rainfall (102 mm) than in the other years, which lengthened the growing period of the herbaceous layer up to mid-June (Ainalis, 1996). Mature and dry herbage yield in early June contained high levels of NDF (Donkor et al., 2003). Generally, the nutritive value and the IVOMD of herbage were slightly increased by repeated short-duration summer grazing. 5. Practical implications The four woody species tested in the silvopastoral system yielded green and fresh foliage, compared to mature and dry herbage, during summer. Although, IVOMD of the legumes black locust and bastard indigo was lower, probably owing to phenolics content, than in herbage for the years 1992 and 1994, the difference was not significant. In contrast, IVOMD of honey locust and white mulberry was superior to that of herbage. Short-duration summer grazing repeated in time is recommended in order for the woody species to produce sufficient regrowth for the grazing animals. Black locust can be considered as the species of choice for an agrosilvopastoral system, owing to its very high production (Ainalis and Tsiouvaras, 1998), although its digestibility is relatively low. On the other hand, although white mulberry does not produce as much forage as black locust (Ainalis and Tsiouvaras, 1998), it is highly recommended for such systems, owing to the high nutritive value and IVOMD of the foliage. 6. Conclusions Short-duration summer grazing with sheep repeated in time stimulated a tendency for an increased IVOMD and reduced fibre and lignin content of black locust, honey locust, bastard indigo and white mulberry. Black locust and bastard indigo produced forage containing higher proportions of crude protein than honey locust and white mulberry, while white mulberry foliage presented the highest IVOMD. IVOMD of the four woody species increased in early autumn and in any case it was higher than that of herbage in summer.
ARTICLE IN PRESS 98
A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
Short-duration summer grazing slightly improved the nutritive value of herbage over the years. The introduced woody species altered the animals’ feed quality in the silvopastoral system during summer, which is highly desirable in the semi-arid Mediterranean zone. Acknowledgements Our research was part of the project ‘Selection and Utilization of Cultivated Fodder Trees and Shrubs in the Mediterranean Extensive Livestock Production Systems’, financed by the European Union’s CAMAR programme. References Ainalis, A.B., 1996. Growth dynamic, production and nutritive value of some shrubby form species in relation to spacing and grazing. Ph.D. Dissertation, Aristotle University of Thessaloniki, Greece, p. 33, 98, 101. Ainalis, A.B., Tsiouvaras, C.N., 1998. Forage production of woody fodder species and herbaceous vegetation in a silvopastoral system in northern Greece. Agroforestry Systems 42, 1–11. AOAC, 1990. Official Methods of Analysis, 15th ed. Association of Official Analytical Chemists, Washington, DC, p. 746. Benevises, J.E., Rodriguez, R.A., Borel, R., 1989. Produccio´n y calidad del forraje de pasto king grass (Pennisetum purpureum x P. typhoides) y poro´ (Erythrina poeppigiana) sembrados en associacio´n. In: Xande, A., Alexandre, G. (Eds.), Paturages et Alimentation en Zone Tropicale Humide. Institut National de la Recherche Agronomique (INRA), Paris. Bonciarelli, F., 1980. Arbusti da foraggio. Uno risorsa da valorizzare. L’Italia agncola 117 (4), 130–137. Corleto, A., Cazzato, E., Laudatio, V., 1992. Quantitative and qualitative evaluation of tree and shrubby pasture species in Southern Italy. In: Proceedings of the CIHEAM, Cahiers Options Mediterraneennes, Fodder Trees and Shrubs, Palermo, Italy, pp. 129–134. Donkor, N.T., Bork, E.W., Hudson, R.J., 2003. Defoliation regime effects on accumulated season-long herbage yield and quality in boreal grassland. Journal of Agronomy and Crop Science 189 (1), 39. Harris, L.E., 1970. Nutrition Research Techniques for Domestic and Wild Animals, vol. I. Logan, Utah, 182pp. Heady, H.F., Reader, L., 1958. Modifications of the point frame. Journal of Range Management 10, 95–96. Koukoura, Z.S., Nastis, A.S., 1992. Tannin content of selected fodder trees and shrubs and their effect on in vitro digestibility. In: Proceedings of the CIHEAM, Cahiers Options Mediterraneennes, Fodder Trees and Shrubs, Palermo, Italy, pp. 117–127. Le Houerou, H.N., 1978. The role of browse in the management of natural grazing lands. Item No. 10, 8 the World Forest Congress, Jakarta, Indonesia, pp. 329–338. Le Houerou, H.N., 1987. Indigenous shrubs and trees in the silvopastoral systems of Africa. In: Steppler, H.A., Nair, P.K.R. (Eds.), Agroforestry, a Decade of Development, ICRAF, Nairobi, pp. 139–156 (Chapter 9). Le Houerou H.N., 1993. Environmental aspects of fodder trees and shrubs plantation in the Mediterranean basin. In: Papanastasis, V.P. (Ed.), Fodder Trees and Shrubs in the Mediterranean Production Systems: Objectives and Expected Results of the EC Research Contract. Agriculture, Agrimed Research Programme, Commission of the European Communities, EUR 14459 EN, pp. 11–33. Makkar, H.P.S., Becker, K., 1998. Do tannins in leaves of trees and shrubs from African and Himalayan region differ in level and activity? Agroforestry Systems 40 (1), 59–68. Makkar, H.P.S., Singh, B., Negi, S.S., 1998. Relationship of rumen degradability with microbial colonization, cell wall constituents and tannin levels in some tree leaves. Animal Production 49, 299–303. Nastis, A.S., 1982. Nutritive value of oak browse (Quercus coccifera L.) forage for goats at various phenological stages. Department of Forestry and Natural Environment, Aristotle University of Thessaloniki, Greece, p. 17. Nehra, O.P., Oswal, M.C., Faroda, A.S., 1987. Management of fodder trees in Haryana. Indian Farming 37 (3), 31–33. Olea, L., Paredes J., Verdasco P., 1992. Evaluation, selection techniques and utilization of the shrubs and fodder trees on the semiarid conditions of the S.W. of Iberian Peninsula. In: Proceedings of the ECC-CAMAR 8001CT90-0030. Research Project Meeting held at Palermo, Italy, pp. 93–100.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
99
Papachristou, T.G., 1997. Foraging behavior of goats and sheep on Mediterranean kermes oak shrublands. Small Ruminant Research 24, 85–93. Papachristou, T.G., Papanastasis, V.P., 1994. Forage value of Mediterranean deciduous woody fodder species and its implication to management of silvo-pastoral systems for goats. Agroforestry Systems 27, 269–282. Papachristou, T.G., Platis, P.D., Papanastasis, V.P., Tsiouvaras, C.N., 1999. Use of deciduous woody species as a diet supplement for goats grazing Mediterranean shrublands during the dry season. Animal Feed Science and Technology 80, 267–279. Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of Statistics, second ed. McGraw-Hill Book Co. Inc., New York, p. 633. Stringi, L., Sarno, R., Amato, G., Leto, G., Gristima, L., Corrao, A., 1987. Shrubs utilization in semiarid environment: bio-agronomic aspects and their use in sheep husbandry. World Review of Animal Production 23 (2), 79–90. Tiago A., 1987. Pastos arboreos-fautor para a valorizacao da pecua´ ria em Tra´ s-os-Montes. In: Rego, F. (Ed.), Trees and Shrubs as food and grazing Animals in Portugal, Fodder Trees and Shrubs in the Mediterranean Production Systems: Objectives and Expected Results of the EC Research Contract. Agriculture, Agrimed Research Programme, Commission of the European Communities, EUR 14459 EN, pp. 45–51. Tsiouvaras, C.N., 1984. Effects of various clipping intensities on browse production and nutritive value of Kermes Oak (Quercus coccifera L.). Ph.D. Dissertation, Aristotle University of Thessaloniki, Greece, pp. 74–85. Tsiouvaras, C.N., Nastis, A.S., 1990. Browse production and nutritive value of some fodder shrubs and trees in a semi-arid environment in Greece. In: Proceedings of the Sixth Meeting of FAO on Mediterranean Pastures and Fodder Crops, Bari, Italy, pp. 169–172. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583–3597.
Journal of Arid Environments 67 (2006) 90–99 www.elsevier.com/locate/jnlabr/yjare
Effect of summer grazing on forage quality of woody and herbaceous species in a silvopastoral system in northern Greece A.B. Ainalisa,, C.N. Tsiouvarasb, A.S. Nastisb a
Forest Service, Region of Central Macedonia, 46th Agriculture School St., 551 34-Thessaloniki, Greece b Range Science Laboratory, Aristotle University, 54124 Thessaloniki, Greece Received 18 April 2005; received in revised form 9 January 2006; accepted 19 January 2006 Available online 20 March 2006
Abstract The forage quality of black locust (Robinia pseudoacacia L.), honey locust (Gleditsia triacanthos L.), bastard indigo (Amorpha fruticosa L.) and white mulberry (Morus alba L.), as well as of the associated herbaceous vegetation, was studied in a silvopastoral system. The study was conducted in a semi-arid grassland with poor sandy soil in northern Greece. Short-duration grazing (28 sheep/ha for 7 days) was repeated twice during the summer period (early July and late August) of 1992, 1993 and 1994. Crude protein content of foliage was maintained at relatively higher levels when plants were grazed compared to control, while neutral and acid detergent fibre content decreased significantly. Crude protein content of black locust and bastard indigo foliage was significantly higher compared to that of honey locust and white mulberry. However, white mulberry presented the highest in vitro digestibility among the four species tested. There was a tendency towards increased in vitro digestibility of the grazed plants’ foliage, compared to that of the control (56% and 53.1%, respectively). In addition, short-duration summer grazing resulted in a small increase in the nutritive value and the in vitro digestibility of the associated herbaceous vegetation. r 2006 Elsevier Ltd. All rights reserved. Keywords: Black locust; Bastard indigo; Honey locust; White mulberry; Mediterranean grassland; Silvopastoralism
Corresponding author. Tel.: +30 2310 409347; fax: +30 2310 475656.
E-mail addresses: [email protected], [email protected] (A.B. Ainalis). 0140-1963/$ - see front matter r 2006 Elsevier Ltd. All rights reserved. doi:10.1016/j.jaridenv.2006.01.017
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
91
1. Introduction Grasslands in the low semi-mountainous zone of Greece occupy 4.2% of the total surface area and much more in the Mediterranean region. The climate is characterized by long dry summers and cold rainy winters. The quantity and quality of herbage production in these grasslands are below the potential, owing to heavy, uncontrolled grazing for many years. After early summer, herbage quality is drastically reduced with plant maturation, because of climatic conditions, leading to malnutrition of the livestock grazing in these grasslands (Nastis, 1982). Many researchers have demonstrated the potential of woody species to produce palatable and nutritious foliage even during the dry season. Many woody species are able to provide green and nutritious forage in summer exceeding qualitatively that of the herbaceous species. They develop long roots reaching deeper soil layers than the herbaceous vegetation, and are able to maintain green phytomass late in the season when the herbaceous layer is dry (Le Houerou, 1987; Olea et al., 1992). The establishment of a silvopastoral system by introducing woody and especially leguminous species into these grasslands could be an effective means of improving the overall forage quality, while ameliorating the supply demand ratio. Several studies have been carried out involving locust species (Robinia sp., hybrid and Gleditsia triacanthos), bastard indigo (Amorpha fruticosa) and bladder senna (Colutea arborescens) (Tsiouvaras and Nastis, 1990; Papachristou and Papanastasis, 1994), alfalfa (Medicago arborea) and blue wattle (Acacia cyanophylla) (Stringi et al., 1987), saltbush (Atriplex halimus), oldman saltbush (A. nummularia), thinleaf fourwing saltbush (A. linearis) and grey desert senna (Cassia sturtii) (Corleto et al., 1992). It is well documented also that woody species significantly help to decrease the risk of soil erosion, improve wildlife habitat, improve the aesthetics of the landscape and enrich the upper soil layer with nutrients (Le Herou, 1993). The objective of this study was to assess the nutritive value of four woody species introduced into a semi-arid grassland at three planting spacings, and of the associated native herbaceous vegetation, as affected by short-duration summer grazing. 2. Materials and methods 2.1. Study area The research was conducted at Scholari village, 43 km east of Thessaloniki, Macedonia, Greece, at an elevation of 90 m and at 401410 north latitude, 231140 east longitude. The long-term average annual rainfall in the area is 512 mm and the mean air temperature 14 1C (Ainalis, 1996). During the dry season (June–September), mean air temperature ranges from 20.9+1.6 to 25.1+1.5 1C and rainfall from 22+22 to 38+40 mm. The climate of the area is characterized as semi-arid with cold winters. The soil texture is sandy to sandy silt, derived from conglomerates of the tertiary period and colluvials from river or torrent bank deposits. The organic matter content (0.97%) and the pH (5.5) are both considered low (Ainalis, 1996). 2.2. Woody species tested The woody species introduced into the grassland were black locust (Robinia pseudoacacia L.), honey locust (G. triacanthos L.), bastard indigo (A. fruticosa L.) and
ARTICLE IN PRESS 92
A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
white mulberry (Morus alba L.). White mulberry is an indigenous species, covering large areas of cultivated land in the past as an important component of silvopastoral systems. Shepherds used to prune young branches to feed livestock. Black locust and honey locust are deciduous leguminous trees, with moderate to high nutritive value foliage and well adapted to semi-arid conditions with cold winters (Le Houerou, 1978; Bonciarelli, 1980). Bastard indigo is a deciduous leguminous shrub, with moderate to high nutritive value and palatability of the foliage and facility of propagation (Stringi et al., 1987). 2.3. Experimental procedure 2.3.1. Experimental layout The experiment was established on a 1.7 ha area of a large mismanaged grassland. The experimental area was fenced and divided into six equally sized plots. Three of the plots were randomly assigned to grazing treatment, while the others were ungrazed (control). Each plot was subdivided into four equally sized subplots, which were assigned at random for planting with one of the four woody species tested. Each subplots was further subdivided into three sub-subplots and randomly assigned to three planting spacings (1.5 1.5 m, 2.5 2.5 m and 3.5 3.5 m, corresponding to: 4440, 1,600 and 810 plants/ha). Plants were one-year old at the time of planting in February 1991. Every year, all plants were topped to a height of 50 cm in December, in order to retain the shrubby form. Cutting annually in winter followed by summer grazing maintains shrubby growth and prevents the plants from spreading beyond the silvopastoral system. Even without this management, the expansion of the above species in natural habitats does not seem to be a problem. They were introduced many centuries ago and they exist in many areas where the seeds are obtained. The system has been employed to ensure sustainable foliage production for grazing (Nehra et al., 1987). The grazing treatment was implemented by introducing 28 sheep/ha for 7 days in early July and for another 7 days in late August. Grazing was repeated for three consecutive years (1992–1994). The grazing system applied was short-duration grazing repeated in time. The sheep flock used in the experiment grazed all day long on the surrounding hills for the rest of the year. The hills are dominated by Quercus coccifera growing in patches associated with herbaceous species in the clearings. 2.4. Nutritive value of browse and herbage Browse samples were taken by hand plugging shoots of o5 mm diameter (Ainalis and Tsiouvaras, 1998). Foliage and herbage production are reported by Ainalis and Tsiouvaras (1998). Samples were collected separately from four grazed and four ungrazed plants of each species, per spacing treatment and per replication. A total of 72 samples of every plant species were collected at each sampling time. In the grazed plots samples were collected: (1) in early July, just before grazing, in order to evaluate whether the previous year’s grazing affected the nutritive value of spring growth foliage; (2) in late August, to evaluate the nutritive value of regrowth after July grazing; and (3) in early October, to evaluate the nutritive value of regrowth after August grazing. In the ungrazed plots samples were collected on the same sampling dates and consisted of fully developed shoots of o5 mm diameter. On every sampling date, samples were collected from unsampled plants.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
93
Herbage samples were collected in late May each year, when most of the herbaceous plants in the area were mature. They were collected by clipping the above-ground biomass at a height of 2 cm above-ground level from three 0.5 0.5 m quadrats per spacing treatment and per replication. The quadrats were randomly placed on permanent transects used for vegetation composition measurements. Composition was determined for three consecutive years by using the ten-point frame method (Heady and Reader, 1958). All samples were oven-dried to 60 1C for 48 h, ground and analysed for crude protein (AOAC, 1990), neutral detergent fibre (NDF) with sodium sulphite and residual ash, acid detergent fibre (ADF) with residual ash, acid detergent lignin (ADL) (Van Soest et al., 1991) and in vitro organic matter digestibility (IVOMD) (Moore’s modification of the Tilley and Terry technique, Harris, 1970). 2.5. Statistical analyses The experimental layout (Steel and Torrie, 1980) was a split–split plot design with three replications (grazing split on woody species; woody species split on spacings). Browse and herbage quality data were subjected to analysis of variance. The least significant difference (LSD) was used for detecting differences (pp0:05) between treatments. 3. Results 3.1. Chemical composition and IVOMD of foliage Average crude protein content of foliage of all tested species was not affected by grazing (Table 1), while neutral and ADF and lignin content decreased significantly (pp0:05) by 12.4%, 13.8% and 18.6%, respectively, compared to the control. By contrast, IVOMD of grazed plants (Table 1) increased significantly (pp0:05) by 10.5% compared to the control. Crude protein and ADF content of black locust foliage was not significantly different (pp0:05) from that of bastard indigo, while that of honey locust was significantly lower than that of the previous two species and that of white mulberry significantly lower than that of all tested species (Table 2). Content of NDF and lignin (Table 2) presented a similar pattern in all tested species, with white mulberry foliage having a significantly lower content than the other species and black locust the highest, while bastard indigo foliage was not significantly different from that of honey locust. By contrast IVOMD (Table 2) of white mulberry was significantly higher than all tested species followed by honey locust, which yielded significantly higher values than both black locust and bastard indigo. No significant differences (pX0:05) were detected in crude protein content of foliage between early July, late August and early October (Table 3). Percentages of ADF and Table 1 Effects of grazing on average chemical composition and IVOMD of foliage of four woody species Grazing treatment
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
Grazing No grazing
17.3 aa 17.0 a
36.7 b 41.9 a
21.8 b 25.3 a
9.6 b 11.8 a
58.7 a 53.1 b
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
94
Table 2 Chemical composition of foliage of four woody species Plant species
Crude protein (%)
Black locust Honey locust Bastard indigo White mulberry
19.3 16.7 18.5 13.8
a
aa b a c
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
45.3 41.3 42.5 31.3
27.2 23.6 26.5 18.3
15.3 a 11.9 b 12.1 b 4.9 c
42.2 56.6 44.8 75.6
a b b c
a b a c
c b c a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
Table 3 Effect of sampling period on average chemical composition and IVOMD of foliage of four woody species Phenological stage
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
Early July Late August Early October
17.1 aa 17.0 a 17.4 a
41.5 a 37.7 b 35.0 b
24.2 a 23.4 a 20.6 b
10.5 a 10.9 a 9.6 b
52.8 c 56.3 b 64.3 a
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
Table 4 Crude protein and IVOMD of foliage of four woody species in the grazing treatments Plant species
Crude protein (%) Grazed
Black locust Honey locust Bastard indigo White mulberry
19.5 16.3 18.7 14.3
a
a a a a
IVOMD (%) Ungrazed
Grazed
Ungrazed
19.2 17.1 18.3 13.4
44.3 a 63.2 a 46.9 a 76.7a
40.2 50.0 42.7 74.5
a a a a
a b a a
a Means of the same category of chemical composition for the same species followed by the same letters are not significantly different at the 0.05 level.
lignin content were significantly lower in early October than in the other two periods (Table 3). Only NDF content was significantly (pp0:05) higher in early July than in late August and early October. By contrast IVOMD was significantly higher in early October than in early July and late August and in late August than in early July (Table 3). Grazing (Table 4) did not affect crude protein content of any of the species tested, but it favoured IVOMD. Honey locust had significantly higher IVOMD than the control (pp0:05). There was a small but non-significant (pX0:05) difference for IVOMD compared with the other tested species (Table 4). A significant interaction (pp0:05) was detected between the sampling time periods and tested species for crude protein content, which, apart from honey locust, maintained an increasing trend towards the end of the growing season (Table 5). IVOMD of honey locust and bastard indigo foliage collected in early October was significantly higher (pp0:05) than in the other periods, while IVOMD of foliage collected
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
95
in late August was significantly higher than in early July (Table 5). Also, IVOMD of black locust and white mulberry foliage collected in early October was significantly higher (pp0:05) than in early July and late August (Table 5). 3.2. Native vegetation composition (%) in the grazing treatments during the 3 years of the experiment In protected plots, there was a tendency over the years for annuals (Fig. 1) to be favoured over perennials. There was a significant increase in both annual grasses and legumes while there was a proportional decrease in perennial grasses and forbs (Fig. 1). 3.3. Chemical composition and IVOMD of herbage Crude protein content of herbage (Table 6), regardless of grazing, increased progressively with the years. During 1993 IVOMD significantly increased and NDF significantly (po0:05) decreased compared to other years (Table 6). Crude protein and Table 5 Crude protein and IVOMD of foliage of four woody species in the three sampling periods Plant species
Crude protein (%) Early July
Black locust Honey locust Bastard indigo White mulberry
19.3 17.4 19.2 12.3
ba a a b
IVOMD (%)
Late August
Early October
Early July
19.0 16.5 18.0 15.0
20.4 15.0 19.0 15.5
40.4 55.6 39.4 75.1
b b b a
a c a a
ba c c b
Late August
Early October
43.3 59.8 48.3 74.0
49.2 74.1 53.0 81.0
b b b b
a a a a
a Means of the same category of chemical composition for the same species followed by the same letters are not significantly different at the 0.05 level.
60.0 Vegetation composition (%)
1992 50.0
1993 1994
40.0 30.0 20.0 10.0 0.0 Annual grasses
Perennial Annual legumes grasses
Forbs
Half- shrubs
Fig. 1. Mean species composition of a silvopastoral system during the 3 years of the experiment.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
96
Table 6 Chemical composition and IVOMD of herbage in a silvopastoral system Years
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
1992 1993 1994
12.2 ca 13.8 b 16.6 a
64.4 a 50.5 c 56.5 b
49.2 a 35.9 c 38.9 b
13.3 a 6.5 c 9.7 b
43.1 c 59.0 a 45.8 b
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
Table 7 Effects of moderate grazing on chemical composition and IVOMD of herbage in a silvopastoral system Grazing treatment
Crude protein (%)
NDF (%)
ADF (%)
ADL (%)
IVOMD (%)
Grazing No grazing
13.1 aa 13.2 a
56.2 b 57.5 a
40.6 b 42.6 a
9.6 b 10.1 a
50.7 a 51.1 a
a
Means in the same column followed by the same letters are not significantly different at the 0.05 level.
IVOMD of herbage were not affected by short-duration grazing, which significantly reduced ADF and lignin content in comparison with the control (Table 7). 4. Discussion 4.1. Chemical composition and IVOMD of foliage There was no evidence that short-duration grazing of woody plants in summer modified crude protein content of foliage, as has been reported by Tiago (1987). This probably occurred because of the high rate of lignification in leaf and shoot cells during summer, even when they develop as regrowth after grazing, because at that time cell walls lignify rapidly so that plants can resist and survive the dry summer period (Benevises et al., 1989; Ainalis, 1996). In contrast, crude protein content increased in early autumn, because the tested species adapted to the lower temperatures and high soil moisture; with corresponding decrease of ADF and lignin content (Papachristou, 1997). The content of ADF and lignin was high in summer as has been reported for many woody species (Tsiouvaras, 1984; Papachristou et al., 1999). Of the tested species, black locust and bastard indigo presented higher crude protein content than the other two species, results similar to those reported by Corleto et al. (1992). The tendency for IVOMD to increase, although not significantly except for honey locust, indicated the high potential of woody fodder plants for summer grazing (Le Houerou, 1978). The very low lignin content as well as the low level of phenolics in white mulberry compared to the three leguminous species (Makkar et al., 1998) probably contributed to the high IVOMD. The phenolics content of the three leguminous woody species is probably high. The foliage of the control plants had higher NDF content than that of the grazed ones, probably owing to the lack of regrowth. Grazed black locust presented high IVOMD, but in any case it was lower than that of white mulberry, probably because of the higher tannin concentration in black locust foliage, which inhibits digestion,
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
97
causing the formation of indigestible tannin–protein complexes (Koukoura and Nastis, 1992; Makkar and Becker, 1998). All tested species, when grazed, had higher IVOMD in early autumn due to regrowth. The relatively high browse quality of the shrubs’ foliage and especially of the regrowth during early autumn was sufficient to meet the animals’ requirements for maintenance and production in the Mediterranean-type environment (Tsiouvaras, 1984; Papachristou and Papanastasis, 1994). 4.2. Chemical composition and IVOMD of herbage Variation of crude protein content of herbage between years was attributed to the modification of the herbaceous species’ composition due to the variation of annual grasses and legumes over the years. When rain coincided with high temperatures in early autumn it was beneficial for legumes (year 1994). However, the significant increase of IVOMD observed in 1993, was mainly attributed to the higher May rainfall (102 mm) than in the other years, which lengthened the growing period of the herbaceous layer up to mid-June (Ainalis, 1996). Mature and dry herbage yield in early June contained high levels of NDF (Donkor et al., 2003). Generally, the nutritive value and the IVOMD of herbage were slightly increased by repeated short-duration summer grazing. 5. Practical implications The four woody species tested in the silvopastoral system yielded green and fresh foliage, compared to mature and dry herbage, during summer. Although, IVOMD of the legumes black locust and bastard indigo was lower, probably owing to phenolics content, than in herbage for the years 1992 and 1994, the difference was not significant. In contrast, IVOMD of honey locust and white mulberry was superior to that of herbage. Short-duration summer grazing repeated in time is recommended in order for the woody species to produce sufficient regrowth for the grazing animals. Black locust can be considered as the species of choice for an agrosilvopastoral system, owing to its very high production (Ainalis and Tsiouvaras, 1998), although its digestibility is relatively low. On the other hand, although white mulberry does not produce as much forage as black locust (Ainalis and Tsiouvaras, 1998), it is highly recommended for such systems, owing to the high nutritive value and IVOMD of the foliage. 6. Conclusions Short-duration summer grazing with sheep repeated in time stimulated a tendency for an increased IVOMD and reduced fibre and lignin content of black locust, honey locust, bastard indigo and white mulberry. Black locust and bastard indigo produced forage containing higher proportions of crude protein than honey locust and white mulberry, while white mulberry foliage presented the highest IVOMD. IVOMD of the four woody species increased in early autumn and in any case it was higher than that of herbage in summer.
ARTICLE IN PRESS 98
A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
Short-duration summer grazing slightly improved the nutritive value of herbage over the years. The introduced woody species altered the animals’ feed quality in the silvopastoral system during summer, which is highly desirable in the semi-arid Mediterranean zone. Acknowledgements Our research was part of the project ‘Selection and Utilization of Cultivated Fodder Trees and Shrubs in the Mediterranean Extensive Livestock Production Systems’, financed by the European Union’s CAMAR programme. References Ainalis, A.B., 1996. Growth dynamic, production and nutritive value of some shrubby form species in relation to spacing and grazing. Ph.D. Dissertation, Aristotle University of Thessaloniki, Greece, p. 33, 98, 101. Ainalis, A.B., Tsiouvaras, C.N., 1998. Forage production of woody fodder species and herbaceous vegetation in a silvopastoral system in northern Greece. Agroforestry Systems 42, 1–11. AOAC, 1990. Official Methods of Analysis, 15th ed. Association of Official Analytical Chemists, Washington, DC, p. 746. Benevises, J.E., Rodriguez, R.A., Borel, R., 1989. Produccio´n y calidad del forraje de pasto king grass (Pennisetum purpureum x P. typhoides) y poro´ (Erythrina poeppigiana) sembrados en associacio´n. In: Xande, A., Alexandre, G. (Eds.), Paturages et Alimentation en Zone Tropicale Humide. Institut National de la Recherche Agronomique (INRA), Paris. Bonciarelli, F., 1980. Arbusti da foraggio. Uno risorsa da valorizzare. L’Italia agncola 117 (4), 130–137. Corleto, A., Cazzato, E., Laudatio, V., 1992. Quantitative and qualitative evaluation of tree and shrubby pasture species in Southern Italy. In: Proceedings of the CIHEAM, Cahiers Options Mediterraneennes, Fodder Trees and Shrubs, Palermo, Italy, pp. 129–134. Donkor, N.T., Bork, E.W., Hudson, R.J., 2003. Defoliation regime effects on accumulated season-long herbage yield and quality in boreal grassland. Journal of Agronomy and Crop Science 189 (1), 39. Harris, L.E., 1970. Nutrition Research Techniques for Domestic and Wild Animals, vol. I. Logan, Utah, 182pp. Heady, H.F., Reader, L., 1958. Modifications of the point frame. Journal of Range Management 10, 95–96. Koukoura, Z.S., Nastis, A.S., 1992. Tannin content of selected fodder trees and shrubs and their effect on in vitro digestibility. In: Proceedings of the CIHEAM, Cahiers Options Mediterraneennes, Fodder Trees and Shrubs, Palermo, Italy, pp. 117–127. Le Houerou, H.N., 1978. The role of browse in the management of natural grazing lands. Item No. 10, 8 the World Forest Congress, Jakarta, Indonesia, pp. 329–338. Le Houerou, H.N., 1987. Indigenous shrubs and trees in the silvopastoral systems of Africa. In: Steppler, H.A., Nair, P.K.R. (Eds.), Agroforestry, a Decade of Development, ICRAF, Nairobi, pp. 139–156 (Chapter 9). Le Houerou H.N., 1993. Environmental aspects of fodder trees and shrubs plantation in the Mediterranean basin. In: Papanastasis, V.P. (Ed.), Fodder Trees and Shrubs in the Mediterranean Production Systems: Objectives and Expected Results of the EC Research Contract. Agriculture, Agrimed Research Programme, Commission of the European Communities, EUR 14459 EN, pp. 11–33. Makkar, H.P.S., Becker, K., 1998. Do tannins in leaves of trees and shrubs from African and Himalayan region differ in level and activity? Agroforestry Systems 40 (1), 59–68. Makkar, H.P.S., Singh, B., Negi, S.S., 1998. Relationship of rumen degradability with microbial colonization, cell wall constituents and tannin levels in some tree leaves. Animal Production 49, 299–303. Nastis, A.S., 1982. Nutritive value of oak browse (Quercus coccifera L.) forage for goats at various phenological stages. Department of Forestry and Natural Environment, Aristotle University of Thessaloniki, Greece, p. 17. Nehra, O.P., Oswal, M.C., Faroda, A.S., 1987. Management of fodder trees in Haryana. Indian Farming 37 (3), 31–33. Olea, L., Paredes J., Verdasco P., 1992. Evaluation, selection techniques and utilization of the shrubs and fodder trees on the semiarid conditions of the S.W. of Iberian Peninsula. In: Proceedings of the ECC-CAMAR 8001CT90-0030. Research Project Meeting held at Palermo, Italy, pp. 93–100.
ARTICLE IN PRESS A.B. Ainalis et al. / Journal of Arid Environments 67 (2006) 90–99
99
Papachristou, T.G., 1997. Foraging behavior of goats and sheep on Mediterranean kermes oak shrublands. Small Ruminant Research 24, 85–93. Papachristou, T.G., Papanastasis, V.P., 1994. Forage value of Mediterranean deciduous woody fodder species and its implication to management of silvo-pastoral systems for goats. Agroforestry Systems 27, 269–282. Papachristou, T.G., Platis, P.D., Papanastasis, V.P., Tsiouvaras, C.N., 1999. Use of deciduous woody species as a diet supplement for goats grazing Mediterranean shrublands during the dry season. Animal Feed Science and Technology 80, 267–279. Steel, R.G.D., Torrie, J.H., 1980. Principles and Procedures of Statistics, second ed. McGraw-Hill Book Co. Inc., New York, p. 633. Stringi, L., Sarno, R., Amato, G., Leto, G., Gristima, L., Corrao, A., 1987. Shrubs utilization in semiarid environment: bio-agronomic aspects and their use in sheep husbandry. World Review of Animal Production 23 (2), 79–90. Tiago A., 1987. Pastos arboreos-fautor para a valorizacao da pecua´ ria em Tra´ s-os-Montes. In: Rego, F. (Ed.), Trees and Shrubs as food and grazing Animals in Portugal, Fodder Trees and Shrubs in the Mediterranean Production Systems: Objectives and Expected Results of the EC Research Contract. Agriculture, Agrimed Research Programme, Commission of the European Communities, EUR 14459 EN, pp. 45–51. Tsiouvaras, C.N., 1984. Effects of various clipping intensities on browse production and nutritive value of Kermes Oak (Quercus coccifera L.). Ph.D. Dissertation, Aristotle University of Thessaloniki, Greece, pp. 74–85. Tsiouvaras, C.N., Nastis, A.S., 1990. Browse production and nutritive value of some fodder shrubs and trees in a semi-arid environment in Greece. In: Proceedings of the Sixth Meeting of FAO on Mediterranean Pastures and Fodder Crops, Bari, Italy, pp. 169–172. Van Soest, P.J., Robertson, J.B., Lewis, B.A., 1991. Methods for dietary fiber, neutral detergent fiber and nonstarch polysaccharides in relation to animal nutrition. J. Dairy Sci. 74, 3583–3597.