Adoption of silage as a methodology to improve domestic goat productivity for marginal farmers of the Tehuacán Valley in México

E Baraza, S Ángeles,* A García** and A Valiente-Banuet**

Departamento de Biología, Universidad de las Islas Baleares, Palma de Mallorca C.P. 07122. España
elena.baraza@uib.es
* Laboratorio de Bromatología del Departamento de Nutrición Animal y Bioquímica, Facultad de Medicina Veterinaria y Zootecnia, UNAM, México D.F., C.P.04510. México
** Laboratorio Ecología de Comunidades, Instituto de Ecología, UNAM, México D.F., C.P.04510. México

Abstract

In arid and semiarid subtropical areas, goat productivity is very low due to the long and pronounced dry season which often causes serious food shortages for the livestock, leading to diseases and increased mortality. During periods of forage scarcity, goats typically increase search effort as their nutrient intake decreases, moreover, the increase of the use of woody species increases the grazing pressure on local vegetation. One possible solution to this problem is to feed the animals while keeping them enclosed during this period. In this study, we evaluated how farmers traditionally meet the nutritional requirements of their domestic goat herds during times of drought, while collaborative experiences with various farmers were used to assess the utility of silage as a method of ensuring adequate food supply. In addition, we assessed the viability of maintaining an enclosed herd throughout the dry season and feeding it with natural local resources and silage of agricultural residues.

Our data demonstrate the need for the implementation of new management measures to allow improvement in livestock production. Corn silage, mixed with other local materials, is a viable and effective method of conserving and improving the nutritional value of fodder. We demonstrate that maintaining a small herd using local resources and corn silage can be a viable management strategy for marginal farmers during the dry season. The use of a participatory approach in this study resulted in increased participation and assimilation of the new approach by the farmers.

Key words: Dry season, natural resources, participatory approach, rural development

Introduction

The domestic goat (Capra hircus L.) typically displays opportunistic and flexible foraging behavior (Lu 1988), which confers adaptability in the face of variable ecological conditions (Genin and Pijoan 1993). Domestic goats are the most commonly reared animals in areas where the characteristics of the available forage are unsuitable for the production of other livestock (Lu 1988). This is the case in many arid and semiarid subtropical areas of the world (Devendra 1981; Shankarnarayan et al 1985; Oba and Post 1999), in which the quantity and quality of the natural forage undergoes drastic reduction during the dry season (Echavarría et al 2006). Although domestic goats are able to survive this decrease in natural forage, such conditions impose a significant restriction in productivity (Pfister and Malechek 1986; Kronberg and Malechek 1997). During the dry season, grasses disappear and most of the trees and shrubs lose their leaves, and the consequent scarcity of forage obliges the animals to consume a higher quantity of less palatable species (Dumont et al 1995; Posse et al 1996). This diet reduces their live weight and increases mortality during the dry season. Higher mortality occurs not only because of the lack of forage, but also due to increased ingestion of toxins (Pfister and Malechek 1986; Papachristou and Nastis 1993; Kronberg and Malechek 1997). Furthermore, goats need to expend more time and energy in the search for food during the dry season (Cisse et al 2002).

Dietary supplementation during the period of scarcity can help farmers to improve goat productivity (Galina et al 1998; Morales et al 2000). However, the critical economic situation of marginal farmers in developing countries often makes it impossible for them to afford commercial supplementation, necessitating the use of local natural resources instead (Baraza et al 2008). Many studies have evaluated the use of different plants, fresh or as silage, for the supplementation of animals ('t Mannetje 1999; Degen et al 2000; Çürek and Özen 2004; Mahgoub et al 2005; Pinos-Rodríguez et al 2006; 2009). The majority of these studies focused on the evaluation of the quality of the natural resource as fodder for the domestic animals, and concluded that the study resource would represent a suitable food supplement in terms of livestock productivity (Degen et al 2000; Çürek and Özen 2004; Mahgoub et al 2005; Pinos-Rodríguez et al 2006; 2009). However, studies of how farmers assimilate the use of these new elements into their livestock production are scarce. The adoption, by marginal farmers, of technologies developed by livestock and forage researchers is complex: this is due in part to the cultural distance between researchers and farmers, but also because of the economic investment typically required. A participatory approach to technology development may help to ensure that new technologies are more appropriate to the needs and circumstances of marginal farmers, while the use of locally available resources can enhance the likelihood of adoption (Conroy et al 2002).

The general objective of the present study is to introduce simple technology to marginal farmers from an underdeveloped area of Mexico, in order to improve the nutrition of their livestock during the dry season. Our objective was to improve domestic goat productivity by using a local resource-based silage as fodder for livestock maintenance during the dry season. Initially, semi-structured interviews were conducted with farmers, in which they were asked about how they traditionally meet the nutritional needs of their herds during times of drought. Silage techniques were then explained and demonstrated to the farmers, involving their direct participation in the preparation of small batches of silage made from agricultural residues and natural plants. One family subsequently participated in an evaluation of the maintenance of a domestic goat herd, which was enclosed for the dry season and fed with local natural resources and agricultural residue silage.

Materials and methods 

Study area description

The Biosphere Reserve of the Tehuacán-Cuicatlán Valley, located in southern-central Mexico, is one of the semiarid zones of greatest biological diversity in the world (Dávila et al 2002). Since the colonial period, extensive herding of goats has become the most important productive activity of subsistence for farmers in this area (Hernández 2000; Hernández et al 2001). The study was focused on San Juan Raya community (Zapotitlan Salinas Municipality) (18°11´ N 97°23´ W, 1750 m.a.s.l.), located in the river basin of Zapotitlán, within the Tehuacán-Cuicatlán Valley in the state of Puebla, Mexico. It has an annual mean rainfall of 380 mm, most of which occurs during the months of June to September, and a mean annual temperature of 21º C with infrequent frosts.  The soils are calcareous, shallow and rocky. The main vegetation type is arid tropical scrub (Valiente-Banuet et al 2000). Domestic goat farming is an important economic practice at San Juan Raya, involving 37.5 % of the families (Osorno-Sánchez 2005). Domestic goat production is a key resource for such marginal farming communities, providing an important source of dietary protein and serving as a financial asset for the family: money may be “invested” by purchasing a number of goats which can be sold off in the future to pay for medical expenses or festive events (Lee 2006).

Interviews

To learn about the nature and quantity of supplements traditionally given to domestic goats during the dry season, a period of natural forage scarcity, we conducted interviews with the farmers. We consulted 15 different families with herds of various sizes (between 20-150), but who all shared a similar economic situation. The questions concerned the systems used to feed their herds during the dry season and the possible health problems that the animals suffer during this period.

Silage of agricultural residues and native species

We explored the use of silage made from agricultural residues (maize stubble and dry shelled bean pods) and local species, such as Opuntia ficus-indica (Cactaceae) and Agave salmiana (Agavaceae), as a method for obtaining a low-cost feed resource for the goats. The common prickly-pear plant, Opuntia ficus-indica, is a horticultural plant whose domestication began 8000-9000 years ago (Kiesling 1998), and which is very common in domestic orchards all over Mexico. Agave salmiana is often cultivated to produce “pulque”, a traditional alcoholic beverage. For the silage, we used the internal part of the plant which is left over after the farmer cuts the plant to obtain the sap for the production of the “pulque”. This efficiently utilized an existing by-product and thereby avoided the need to damage healthy plants. Both Opuntia ficus-indica and Agave salmiana display high water use efficiency and chemical characteristics that make them suitable elements for livestock feed during dry periods (Baraza et al 2008 and references therein).

A meeting was held in order to find farmers interested in participating in the project. Half of the local livestock owners (14 people) attended the meeting, which featured a presentation of the project. A basic explanation of the nature and benefits of silage was given. Four families expressed their wish to actively participate in the project.

Six different micro-productions of silage were carried out in plastic bags, with individual compositions shown in Table 1.

Two families participated in the production of silage A1 and B1, and A2 and B2 respectively. The third family prepared silage A3 while the fourth family produced silage B3. All silages were produced mainly by the farmers themselves, but with advice and input from the researchers. Chopping of each ingredient was carried out manually with machetes. Molasses, an ingredient not normally available on these farms, was used in silages 1B and 3B only. Molasses is considered a good source of the carbohydrates necessary for the correct fermentation of the silage. However, it is difficult to obtain because normally it is exclusively used in factories for transformation to alcohol. For the preparation of the other silages, we used other carbohydrate sources such as sugar cane, as these were easier for the farmers to acquire. All silage components were selected for their availability and potential as goat fodder, while taking their chemical characteristics (Crude protein, total digestible nutrients metabolizable energy, calcium and phosphorus) into consideration (see Baraza et al 2008 for more details).

After 40-50 days, the silage bags were opened for sampling. Samples were weighed immediately and taken to the Laboratorio de Bromatología, Departamento de Nutrición Animal y Bioquímica, Facultad de Medicina Veterinaria y Zootecnia, UNAM, to determine their nutritional value. In the laboratory, samples were oven-dried to constant weight at 55°C, and dry mass was measured to calculate the original water content. We analyzed the following chemical characteristics: Crude protein (total nitrogen x 6.25), cellular content, hemicellulose, cellulose, lignin, total digestible nutrients (TDN), digestible energy (DE) and metabolizable energy (ME), calcium, phosphorus and minerals (Mg, Fe, Cu, Zn, Co). In all the cases AOAC methodologies were followed (1990). Two replications were made for the analysis of each characteristic and the results given are the means of each replicated analysis.

Maintenance of a small herd for 45 days during the dry season

In order to demonstrate the possibility of maintaining enclosed livestock during the dry season with a minimal economic investment, a small herd was kept enclosed for 45 days from February 11^th to March 27^th. This herd belonged to a family which had participated in the production of silage in plastic bags in the previous year and, as a result of this experience, they were keen to participate in this study.

Sixteen animals (ten female adults and six kids of less than one year in age) were enclosed and fed for 45 days with; corn silage, mature fruits of Yucca periculosa, dry pods of Prosopis laevigata, and also cladodes of wild pear (Opuntia pilifera), which had been collected on the day of consumption. All these natural food resources are abundant in the area and their chemical characteristics allow their combination in the composition of a suitable diet (see Baraza et al 2008 for more details). Silage was prepared at the farm in a hole in the ground with freshly chopped corn stubble and salt (see Table 2 for chemical characteristics).

Farmers were advised regarding appropriate proportions of each of these various resources in the diet, based on the minimum requirements for the maintenance of an adult animal and taking into account their body weight (NRC 2006), and the nutritional characteristics and availability of each component of the diet. Although supervision by the researchers was continuous, farmers were allowed to take decisions regarding the timing and quantity of food given to their animals. At the conclusion of the experiment, interviews were conducted with the families (both men and women) in order to assess their satisfaction with the participatory experience.

Goats were weighed at the beginning of the administration of the diet and again at the end, after 45 days. The variation in weight was analyzed by repeated measured ANOVA with no between subject factor and time as within subject factor.

Results 

Interviews

During the dry season, 58.4% of the farmers traditionally supplement the diets of their herds. Of these, 25% only feed the animals which they consider to be thin and 16.6% only feed the thin and young animals. 50% feed their animals every day, 33.3% 3-4 days a week and 16.7% occasionally. 83.3% fed the animals with dry maize stubble, 66.7% also used dry acahuale (Sanvitalia fruticosa, a maize field weed), 66.7% occasionally use alfalfa, 25% use corn, 8.3% use dried shelled bean pods, while only 8.3% occasionally give the goats a commercial animal feed. Most of the farmers cultivated corn and beans, but reduced harvests in dry years mean that they often need to buy these, further reducing the availability of supplementary feed material for the livestock. Despite this traditional supplementation, 83.4% of farmers reported livestock deaths during the dry season due to lack of food and related diseases.

Silage of agricultural residues and native species

All silages were successful with the exception of A2, where a major fungal contamination occurred in the layer closest to the plastic. In the remaining five silages, lactic fermentation occurred, resulting in greenish brown silage with a pleasant odor. The different silage types resulted in different nutritional characteristics: the corn silage and acahuale provided a protein-rich food, while in that of Agave marmorata and Opuntia ficus-indica, the calcium content was higher (Table 2). The use of acahuale decrease the levels of phosphorous and protein, which are scarce in the typical dry-season diet (Baraza et al 2008). The high moisture content of Agave and Opuntia was offset by the use of the bean pods, which were very dry (Table 2). The inclusion of crushed eggshells increased the proportion of calcium and phosphorus (Table 2), improving the silage quality. The palatability of the silage obtained was high, with the exception of silage made with Agave marmorata, the consumption of which required an adaptation period of 3-4 days.    

Maintenance of a small herd for 45 days during the dry season

The live weight of the goats increased significantly (P = 0.01) during the enclosed period. Farmers considered that the reduction of time required for maintenance of the herd was worth the economic investment. Moreover, they judged that the goats were in better physical condition than in other years when goats had foraged in the thornscrub. The women, who normally take the herds to forage, were happy not to go outside during the dry season when it is hot and windy, and when both goats and herders must walk further and faster in order to find the scarce forage (Cisse et al 2002).

Discussion 

The interviews revealed a clear need for improvement of dry season livestock feeding systems in order to reduce livestock mortality. Extreme poverty makes it impossible for farmers to purchase feed, so many must restrict aid to young or weak animals only, leaving the majority of the herd to suffer significant weight loss (Baraza et al unpublished data). During dry years, the difficulty of supplying adequate food increases. Farmers generally have insufficient financial resources to supply their animals and what little money they have is required to feed their families.

The production of silage is an alternative method to conserve fresh forage for use during future periods of feed shortages. Moreover, it has potential as a way to obtain low-cost food resources appropriate to the maintenance of livestock in tropical areas ('t Mannetje 1999). Our results show that, in adequate amounts, the combination of corn and acahuale silage with that produced from Opuntia or Agave can be an appropriate dietary supplement during the dry season because the former can provide protein and phosphorus, while the latter provides calcium and minerals. The nopal (various species of genus Opuntia) is considered a good food (fresh or as silage) for livestock when it is combined with other foodstuffs rich in protein and dry matter (Çürek and Özen 2004). In the case of Agave, a much less studied resource, the silage had a similar nutritional quality that of Opuntia, but its palatability was lower (personal observations; Zamudio et al 2009). While the chemical characteristics of Agave make silage production an ideal practice for its preservation and nutritional improvement (Pinos-Rodríguez et al 2009), its high fiber content requires a greater investment of energy to chop it. Nevertheless, in times of forage scarcity, the core of Agave, cut for the production of “pulque” and normally discarded, could be used fresh as an animal feed (Pinos-Rodríguez et al 2006).

Scientists have acquired a large quantity of knowledge regarding silage methodology in developing countries (for example, 't Mannetje 1999). Despite this, adoption of the technology is not always possible. In our case, although the farmers could see that the silage was readily consumed by the animals, and chemical analysis showed them that silage was a suitable food, they considered that the manual effort required to produce the silage did not justify the results. The need to manually chop the material made it difficult to produce sufficient quantities to sustain the animals throughout the dry period. However, they were interested in the method: they organize themselves to submit a request to the agrarian authorities for a communal mechanical chopper.

Our work was based primarily on a collaborative relationship with the farmers, where the researchers and farmers were approximately equal partners in the research process and collaborated continuously in the activities (Conroy et al 2002). In this context, it was important that the farmers learn about both food production and decision-making with regard to their livestock. We consider that the test was successful, since the goats maintained an adequate weight, and the level of economic investment required was viable. Furthermore, in the dry period following the experiment, the family adopted the method by themselves, and made silage to maintain their enclosed animals in a similar way as they had done during the experiment.

With this management strategy, the farmers have more time at their disposal, since they do not have to herd their animals for eight-nine hours per day. This allowed the owners of small herds of livestock to use their time for other activities, in some cases paid work, enabling them to increase their incomes. In addition, our results demonstrate that the use of Opuntia, mature fruits of yucca and mesquite pods not only improves the diet of the herd, but reduces the dependence on maize stubble as the only dietary supplement used by the majority of farmers (Baraza et al 2008). This is extremely important in dry years, since the lack of maize productivity not only reduces the availability of stubble but also puts additional pressure on the economic resources of each family.

Acknowledgements 

Thanks to Don Silvano, Doña Diega, Don Juventino, Don Cipriano and especially to Don Primitivo and Doña Engracia for their collaboration. Thanks to the inhabitants of San Cayetano ranch who provided us with mesquite pods, and to O.D. Delgado who helped with the field work. Financial support was provided by DGAPA (Project IN-227605) to A. Valiente-Banuet and a postdoctoral grant from Fundación Ramón Areces (Spain) to E.B. Thanks to Keith MacMillan for revision of the English version of the manuscript.

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Received 21 September 2009; Accepted 15 October 2009; Published 3 December 2009

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