Evaluation of Chipilín (Crotalaria longirostrata) as a forage resource for ruminant feeding in the tropical areas of Mexico

 

L Arias , H Losada, A Rendón, D Grande, J Vieyra, R Soriano, J Rivera and J Cortés

 

Sustainable Agricultural Development Research Area. Department of Biology of Reproduction,
Division of Biological and Health Sciences, Autonomous Metropolitan University-Iztapalapa,
Av. San Rafael Atlixco No. 186. Col. Vicentina. Iztapalapa. CP 09340. Mexico D.F.

hrlc@xanum.uam.mx

 

 

Abstract

 

Samples of stalks-with-leaves, leaves-with-petiole and leaves of chipilín (Crotalaria longirostrata) were collected in five tropical communities of the state of Veracruz, Mexico, to analyse their chemical composition and in vitro dry matter digestibility (IVDMD).

 

Crude protein contents were 30.6, 36.3 and 38.3 % in DM for the stalks-with-leaves, leaves-with-petiole and leaves, while crude fibre presented values of 22.8, 13.1 and 11.8 % DM in the same order. IVDMD was highest for the stalks-with-leaves (41.8%) and lowest for the leaves-with-petiole (32.1 %), whilst leaves presented intermediate values (35.3 %). The highest contents for neutral detergent fibre and cellulose corresponded to the stalks-with-leaves (33.8 and 21.5 %), followed by the leaves-with-petiole (28.4 and 13.0 %) and leaves (22.5 and 11.1 % DM respectively).

 

The productive potential of the plant for ruminant feeding is discussed in function of its high protein content.

 

Key words: Chemical composition, Crotalaria longirostrate, dry matter digestibility, leguminous, protein

 

 

Introduction 

 

The chipilín (Crotalaria longirostrata) is a tropical legume domesticated since pre-Hispanic times (Hernández and León 1994) maintaining the anthropocentric characteristics reported for other plants of the country (Vieyra et al 2002). It covers a wide range of uses such as: food and refreshing drink for humans (Centurión et al 2000), cover crop or green manure (by fixing atmospheric nitrogen), improvement of fallows (Desaeger and Rao 1999), paper elaboration, medicinal plant and melliferous species (Fischler and Wortman 1999). An alternate possibility for its use would be as a forage for animal feeding, as has been reported in Mexico and other countries. Notwithstanding that Crotalaria longirostrata is considered at world level as one of the 16 most important species of edible leaf, literature reports on it's chemical composition and/or its nutritional value in Mexico are scarce. The present study describes the nutritional value of the plant evaluated by means of its chemical composition and in vitro digestibility. 

 

Materials and Methods 

 

Collection and processing of the plant 

 

Plants of the species Crotalaria longirostrata were collected in 5 communities of the state of Veracruz (Acayucan, Jáltipan, Cosoleacaque, Oteapan and Coacotla) characterized for their humid warm tropical climate (Am) or warm sub humid (Aw) with a rainfall regime concentrated in the summer (García 1987). The sampling was carried out at random once the plants were detected and it included: stalks-with-leaves, leaves-with-petiole and leaves. About 1 kg of each component was collected per community. Later the samples of each component were pooled and a sub-sample of 1 kg of each  was obtained. The samples were dried in a forced air oven (Felisa FE144A) at a temperature of 40 to 55^ºC during 48 h, and  were then milled in a Willey mill using a 1 mm mesh and stored for analysis.  

 

Chemical analysis 

 

All the samples were analysed  for content of dry matter (DM), total nitrogen and non-protein fraction, crude fibre (CF), ether extract (EE), ash and nitrogen free extract (NFE) following the procedures described by the AOAC (1990). The cellular walls and cellular contents were determined following the procedures described by Van Soest et al (1991) and Doane et al (1997). Determination of  in vitro dry matter digestibility (IVDMD)) was carried out according to procedures described by Ruiz (1997) and Arias et al (2002) while the Tejada tests (1992) were applied for protein solubility. 

 

Statistical analysis  

 

The data for DM digestibility were statistically analyzed to obtain the mean and standard errors, using the statistical package Number Cruncher Statistical System 2001 (NCSS Statistical Software). 

 
 

Results and Discussion 

 

The chemical composition of the different portions of the plant is presented in Table 1. 

DM contents were higher for the stalks-with-leaves in contrast with the leaves-with-petiole or leaves alone. In contrast, CP content showed superior values in the leaves and inferior measures in the stalks-with-leaves while the leaf-with-petiole presented intermediate values. The soluble fraction of the protein was similar in the stalks-with-leaves and leaves-with-petiole(13.2 ± 0.50 and 13.8 ± 0.36) and higher for the leaves (16.0 ± 0.40). As expected the percentages of crude fibre were higher in the stalks-with-leaves and the leaves-with-petiole. EE contents were low, independent of the portion of the plant, which agrees with the reports of the literature for tropical grasses (Jiménez 1982), while the differences observed for ash and NFE contents were lower in the different samples of the plant. The values reported for IVDMD in the different portions of the plant  were higher for the stalks-with-leaves and lower for the leaves-with-petiole, whilst leaves showed intermediate values (see Table 2). 

Cell wall components, other than hemicellulose,  were highest in the portion of the plant including the stalk. Hemicellulose content was highest  for the leaves with petiole (Table 3).                     

 The results  confirm the importance of the plant as a source of N, with a mean CP value of 31 % in DM. Due to the fact that most of the protein is insoluble, it is possible that inclusion of the chipilín  may serve as a partial source of bypass protein (Leng 1995) in ruminant diets. A factor that could be considered as restrictive of its use, is the low value for in vitro DM digestibility, independently of the fraction of the plant. This might be related to the presence of secondary plant compounds such as tannins, commonly found in tropical shrub and tree legume species (Van Soest 1982), and which in high concentrations can reduce substantially the digestibility (Barry and McNabb 1999). The demonstration of this hypothesis would be a topic of interest to investigate in the future.  
 

 

Acknowledgements 

 

The authors thank the authorities of UAM for the facilities granted to carry out the research.  We are grateful to Adrián Rendón Flores, for support to carry out the laboratory analysis.     

 

References

 

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