Chemical composition and in vitro dry matter digestibility of some fodder trees from South-east México

F J Solorio-Sánchez , I Armendariz-Yañez  and J Ku-Vera

Facultad de Medicina Veterinaria y Zootecnia/Universidad Autónoma de Yucatán
Apdo 4-116; CP 97100. Mérida, Yucatán, México

f.j.solorio@excite.com

Abstract

An in vitro dry matter digestibility (IVDMD, %) study was conducted using rumen liquor as source of inoculum. Dry samples (leaf, stem and seed) of eight tropical trees were used as substrates. Crude protein in leaf dry matter ranged from 12.8% in Bursera simaruba to 23.4% in Sesbania grandiflora. The IVDMD was highest (74.3%) in Gliricidia sepium foliage and lowest (37.9%) in Guazuma ulmifolia. Albizia lebbeck had the highest in vitro digestibility for seeds (84.0%), while S. grandiflora had the highest value for stems (39.7%). 

The results suggest that at least four tree species (A. lebbeck, G. sepium, B. alicastrum and S. grandiflora) used in this study have high feeding value.

Key words: Tree foliage, Gliricidia sepium, Albizia lebbeck, Brosimum alicastrum, Sesbania grandiflora, digestibility, crude protein

Introduction

In Yucatan, as in various parts of the tropics, most small-scale farmers rely on grasses as a major feed input for animal maintenance. However, forage quality (low digestibility, low protein content and low mineral content) declines during the dry season. The major factor that limits animal production from these grasses is the fact that the animals lose weight due to the nutritional imbalance in the feed available (Preston and Leng, 1987; Mannetje 1982).

The fodder trees currently available in Yucatan can be considered as important sources of energy and protein to be utilised in the different animal production systems. Though local farmers traditionally utilise foliage from trees such as ramon (Brosimun alicastrum), in particular for milk production, relatively little is known in relation to their nutritive value.

The objective of the present research was to assess the in vitro dry matter digestibility (IVDMD) and the chemical composition of various fodder trees in order to obtain information on their nutritive value for ruminant animals.

Materials and Methods

The fodder trees used for this study included indigenous and naturalised trees (Table 1). Samples were collected from plants growing at the Faculty of Veterinary Medicine and Animal Production, separated into edible forage  (leaves, stems less than 5 mm in diameter and seeds), and dried in a forced-air oven at 60°C for 48 h. Each sample of plant material was analysed in duplicate for nitrogen and ash (AOAC 1990) and neutral detergent fibre (Van Soest et al 1991).

In vitro dry matter digestibility was determined according to Tilley and Terry (1963). Seven hundred ml of ruminal liquor were obtained from a rumen cannulated Zebu steer fed with hay of buffel grass (Cenchrus ciliaris, 8.8 % crude protein) ad libitum. The steer was housed in a metabolism cage and supplied with a mineralised block and fresh water continuously. The rumen liquor was strained through two layers of muslin into tubes, and CO₂ was passed into the flask to displace air from above the rumen liquor. The flask was then kept at 39°C in a water bath during 48 h.

The tubes for IVDMD (four replicates for each part of the plant) were incubated in artificial saliva (30 ml) with the sample of tree foliage (1 g) during 48 h, after which they were stirred for two hours then 2 ml of sodium carbonate and 1 ml of mercurium chloride were added. The tubes were then centrifuged, the supernatant liquid poured off and a solution of pepsin-hydrochloric acid (50 ml) added. The tubes were then incubated for another 24 h. After the 48 h of incubation, digested samples were filtered in pre-weighed sintered glass crucible,  dried at 60°C for 24 h and weighed. IVDMD was estimated by difference.

Results and Discussion

The data for chemical content (Table 2) indicate that S. grandiflora seeds had the highest levels of crude protein (34.5%) but the lowest IVDMD (69.5%), while A. lebbeck seeds had the highest IVDMD (84.0%) and moderate levels of crude protein (28.4 %).

The IVDMD of the leaves ranged from 74 to 38% and were ranked as follow: G. sepium> A. lebbeck > S.grandiflora > B. alicastrum > L. leucocephala> P. piscipula > B. simaruba > G. ulmifolia (Figure 1). These results are very similar to those reported by Mizrahi et al (1998) and Roshetko et al (1998) and are within the range reported by Benavides (1999) and Armendariz-Yañez (1998) for other fodder trees.   

Figure 1: IVDMD of seven tropical fodder trees in Yucatán, México

The leaves from G. ulmifolia leaf had the lowest IVDMD (37.9%), and the highest NDF content (57.0%), which may have been due to the fact that this was the oldest tree sampled. Roshetko et al (1998) found that G. ulmifolia had unfavourable degradation characteristics which can result in high rumen fill and therefore low DM intake. 

NDF was`poorly correlated with IVDMD (R² = 0.62) (Figure 2).

Figure 2: Relationship between IVDMD and the NDF content of the leaves 
of seven tropical fodder trees 

Conclusions

The data reported in this study indicate that the leaves and seeds from a range of trees have a good potential to supply highly digestible feed suitable for ruminants. However, strategies to assess and utilize the potential feeding value of tree foliages are still at the developmental stage.

References

AOAC 1990 Official Methods of Analysis (15th edn.). Association of Official Analytical Chemists (15^th edn.). Washington, DC.

Armendariz-Yañez I 1998 Indigenous fodder legume trees: their influence on soil fertility and animal production on tropical pastures of Yucatán, México. PhD thesis. University of London, Imperial College at Wye.

Benavides J E 1999 Research on Forage Trees. In: First FAO Electronic Conference on Tropical feeding Systems. FAO, Rome

t’ Mannetje L 1982 Problems of animal production from tropical pastures. In: Nutritional Limits to Animal Production from Pastures (Editor: J B Hacker). Proceedings of an international symposium held at St. Lucia, Queensland, Australia. Commonwealth Agricultural Bureaux. Australia.

Mizrahi A, Ramírez-Avilés L,  Castillo-Caamal J and Pool P 1998 Assessing the nutrient content of fodder trees in Yucatán, México. Agroforestry Today. 10 (4): 11-13

Preston T R and Leng R A 1987 Matching Ruminant Production Systems with Available Resources in the Tropics and Sub-tropics. Penambul Books, Armidale, Australia.

Ramirez C L 1998 Consumo, digestion ruminal y suministro de nitrogeno microbiano al duodeno en ovinos alimentados con pasto Taiwan (Pennisetum purpureum) suplementados con follaje de arboles. Merida, Yucatan. FMVZ/UADY

Roshetko J M, Lantagne D O and Gold M A 1998 In vitro digestibility and nutritive value of the leaves of native, naturalized, and recently introduced tree species in Jamaica. In: Nitrogen fixing trees for fodder production (Editors: J N Daniel and J M Roshetko).  Proceeding of an International workshop. Forest Farm and Community Tree Research Report. FACT Net. USA.

Tilley J M A and Terry R A 1963 A two-stage technique for the in vitro digestion of forage crops. Journal of the British Grassland Society 18: 104-111

Van Soest P J, Robertson J B and Lewis B A  1991 Methods for Dietary Fiber, Neutral Detergent Fiber, and Non-starch Polysaccharides in Relation to Animal Nutrition. Journal of Dairy Science 74(10): 3583-3597

 Received 12 July 2000

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