Introduction

Deforestation is a strong environmental problems caused by anthropogenic activity. Much of the deforested areas are dedicated to the cultivation of pure pastures soon fall into a state of degradation (^{Pezo and Ibrahim, 1997}). The causes of the problem are inadequate in land management, rangeland and livestock practices, such as: uncontrolled burning of pastures, systems inappropriate tillage, lack of vegetation cover, ineffective management of soil fertility and overgrazing (Ibrahim et al., 2006). Deforestation and pasture degradation results in loss of biodiversity, compaction and soil erosion, breaking the water balance in watersheds and increasing emissions of gases that contribute to global warming (^{Harvey et al., 2008}; ^{Nair et al., 2009}; ^{Alonso, 2011}).

The use of native perennial woody species with forage potential, based on traditional animal production systems, is an alternative that offers good quality forage for animals (^{Solórzano et al., 2003}; ^{López et al., 2008}; ^{Pinto et al., 2010}). In addition, tree species can be used in the design of technologies that control erosion and improve soil fertility; additionally, they can offer other products such as firewood, timber, fruits and seeds that generate income to producers and to provide economic family production unit (Martín, 2008) stability. Thus, the incorporation of woody perennials (trees and shrubs) in livestock production systems is a strategy that helps to offset the negative environmental impacts, diversifying livestock business generates new products and revenue, and reduce dependence on inputs external, intensifying land use resource.

In the future, animal production systems should not only increase productivity to meet the demands of food security, but also must consider the rational use of resources; as well as improve efficiency to make them more competitive, so that really contribute to improving the standard of living of rural families (^{Nair et al., 2010}).

The natural resources of the mountain range of Huautla, in the State of Morelos, are degraded permanently because rural communities established in this area do not have permanent jobs, which favors the rent of their land for grazing livestock (^{Uribe et al., 2015}). In addition, poor distribution of rainfall during limited forage production, causing a long season of drought in the cattle pasture does not have enough for food. Consequently, more and more trees are felled natural vegetation for the establishment of improved pastures, causing several species of wild plants and animals are at risk of disappearing due to habitat deterioration.

The optimal and sustainable utilization of tree species of tropical dry forest of the mountain range of Huautla is of utmost importance for traditional livestock production of marginalized groups living in the region. Therefore, this research aims to identify tree species with forage potential of the mountain range of Huautla, by rescuing traditional knowledge of producers to propose agroforestry technologies that promote sustainability of livestock.

Materials and methods

The research was conducted in the municipality of Tepalcingo in communities Huitchila, Los Sauces and El Limon, located south of the state of Morelos (Figure 1).

Figure 1 Location map of the Reserva de la Biósfera de la Sierra de Huautla, Morelos. Mexico (^{CONANP, 2005}). 

The area of the Reserva de la Biósfera de la Montaña de Huautla (REBIOSH) covers an area of 59 030 hectares and has an altitudinal range from 700 to 2 200 m (^{CONANP, 2005}). The natural boundary southwest is the Río Amacuzac and the most important hills are: Temazcal, Los Chivos, Pericón, El Jumilar, Cerro frío, Potrero los Burros and El Cuacle and mountain range of Huautla. The municipalities involved are: Amacuzac, Ayala, bridge of Ixtla, Jojutla, Tlaquiltenango and Tepalcingo, and the main towns are: Huautla, Huaxtla, Rancho Viejo, Xantiopa, Ajuchitlán, El Limón, Huixastla, Pueblo Viejo, Xochipala, Coaxintlán, El Salto and El Zapote (^{CONANP, 2005}).

The territory of the REBIOSH is comprised of two physiographic provinces. The first includes part of Neovolcanic and consists of a variety of volcanic rocks and continental sediments of lacustrine deposits Miocene gypsum; the second province is located in the Sierra Madre del Sur, where intricate hills and plateaux with altitudes from 900 to 1 400 m (^{INEGI, 1981}) can be seen. The topography is essentially rugged, presents a series of hills and mountains with altitudinal gradient between 1 000 and 1 700 meters (^{CETENAL, 1976}).

This research was conducted in three stages: the first was the identification of tree species with for age potential, the second consisted of agronomic characterization of forage species, and the third in the design of agroforestry technologies.

Results and discussion

According to information collected in surveys to producers the five species that were most frequently use were chosen: Guazuma ulmifolia 90% (27/30 respondents), Acacia cochliacanta 90% (27/30 respondents), Leucaena leucocephala 80% (24/30 respondents), Leucaena macrophylla 73.3% (22/30 respondents) and Leucaena esculenta 66.6% (20/30 respondents).

The germination percentages were 84% for Leucaena esculenta, Guazuma ulmifolia for 73% and 61% for Acacia cochliacantha considered acceptable for pre-germination treatment.

The tree species with higher protein content in the foliage was Leucaena macrophylla, which is higher by 18% and 30% protein content Guazuma ulmifolia and Leucaena leucocephala, respectively (Table 1).

Table 1 Chemical composition (%) of three forage tree foliage in the mountain range of Huautla, Morelos. 

MO= materia orgánica; CEN= cenizas; PC= proteína cruda; FC= fibra cruda; EE= extracto etéreo; FDN= fibra detergente neutro.

Guazuma ulmifolia showed a lower ratio CEN:MO compared to Leucaena leucocephala and Leucaena macrophylla (1:7 vs 1:8.6 and 1:10, respectively), making greater contribution inferred mineral in the diet of animals when ingested foliage G. ulmifolia. Leucaena macrophylla also had higher content of FC because the foliage of the tree contains more cell wall (FND) than Leucaena leucocephala and Guazuma ulmifolia. The foliage of the three trees in free growth contain high levels of fiber, which allows us to infer moderate rates low ruminal digestibility.

In the Table 2 shows presented the nutritional composition of fruits and Guazuma ulmifolia and Acacia cochliacantha.

Table 2 Chemical composition (%) of the fruits of two fodder tree in the mountain range of Huautla, Morelos. 

MO= materia orgánica; CEN= cenizas; PC= proteína cruda; EE = extracto etéreo; FC= fibra cruda; FDN = fibra detergente neutro.

The total protein content of the fruit of the Guazuma ulmifolia was less than Acacia cochliacantha, although both tree species nitrogen input from the fruits is low. The relationship CEN:MO was similar to the Guazuma ulmifolia and the Acacia cochliacantha (1:19 and 1:17, respectively), indicating that the fruits of both trees have low mineral content. In addition, the lipid content (EE) in the fruits of the tree was low, providing a bit more Guazuma ulmifolia that the Acacia cochliacantha. Acacia cochliacantha is superior. The percentage of fiber (FC and FDN) was moderate.

As a result of the survey of 18 livestock producers located in the study area, were identified ten native tree species with forage potential: Guazuma ulmifolia, Acacia cochliacanta, Leucaena leucocephala, Leucaena macrophylla, Leucaena esculenta, Spondias mombin, Spondias purpurea, Erythrina americana, Pithecellobium dulce, and Gliricidia sepium. The local knowledge on the use and management of trees and shrubs multipurpose was considered to build the proposed alternative intervention for the sustainable management of livestock systems in rural communities of the mountain range of Huautla, in order to improve processes food production locally. It is well known that empirical knowledge is useful to promote use more efficient forage from trees and shrubs in livestock production (^{Vessuri, 2004}).

The silvopastoral designs most commonly used in Mexico are scattered trees in pastures, hedgerows, fodder banks, windbreak barriers, grazing pastures in alleys and in natural forests. scattered trees in pastures is a silvopastoral technology in which trees and shrubs are distributed randomly within the grazing areas to provide shade to the animals on hot days or shelter on rainy days and generate other products with fodder, firewood , wood, fruits, seeds, nitrogen fixation, input of organic matter and soil protection (^{FIDAR, 2003}). The hedgerows are rows of trees, complemented by the use of barbed wire, they serve to define paddocks, although its potential not only allows delimit boundaries but also provides fodder, firewood, timber, poles, food, soil protection and animals, and promotes biodiversity.

Fodder banks are pasture, trees and shrubs grown at high density (more than 10 000 plants ha-1) increase production and quality of forage per unit of land and contribute in animal feed, especially during dry seasons (^{FIDAR, 2003}). The windbreak barriers are rows of trees and shrubs of different heights, set perpendicular to the wind direction. Its main function is to protect crops and animals wind mechanical action to reduce your speed, avoid loss of soil fertility, reduce wind erosion and regulate micro-climatic conditions of the cattle farm (^{FIDAR, 2003}).

Pastures in alleys are arranged in parallel lines of trees or shrubs, along with pastures planted between the rows of trees. This silvopastoral design favors the recycling of nutrients in the soil, prevents erosion and reduce the negative effect of trampling on the ground; its main purpose is to intensify land use by providing timber, fruits, fodder and animal products, and improve soil fertility and reduce erosion processes (^{FIDAR, 2003}). Grazing on natural forest is perhaps the oldest practice in livestock.

This silvopastoral system allows the forage potential of forests, jungles and thickets and helps in controlling undesirable plants in natural rangelands of the various agricultural regions of Mexico. In the mountain range of Huautla, the contribution of herbaceous, shrub and tree layer of the tropical dry forest is critical to conducting extensive livestock farming families in the region. The animals supplemented their diet with foliage, pods and fruits of trees and shrubs that grow in tropical dry forest, while rural families get firewood, timber, fruits, medicinal, ornamental and ceremonial plants and food from wildlife (^{FIDAR, 2003}).

Conclusions

In the mountain range of Huautla there are woody plants with high forage potential that can be used for the design of silvopastoral technologies, which will improve traditional livestock production system. From the perspective of producers, most tree species forage potential are: Guazuma ulmifolia, Acacia cochliacantha, Leucaena leucocephala, Leucaena sculenta, Leucaena macrophylla, Erythrina americana, Spondias purpurea, Erythrina americana, Pithecellobium dulce and Gliricidia sepium. The results of the compositional analysis of foliage and fruit of the tree selected by farmers confirm the importance of local knowledge in the use and conservation of native trees, as they are high in protein and moderate digestibility of dry matter.

The traditional knowledge of producers, enriched with agronomic information generated in this investigation, allow proper management of tree species with high potential forage in the study region. The silvopastoral technologies: scattered trees in pastures, hedgerows, fodder banks, windbreak barriers, pastures in alleys and grazing in natural forests may be options to reduce the negative impacts of ranching, loss of natural vegetation and degradation soil, in the mountain range of Huautla.