Potential of water hyacinth (Eicchornia crassipes) in ruminant nutrition in Tanzania

A A O Aboud, R S Kidunda and J Osarya*

Department of Animal Science and Production, Sokoine Univesity of Agriculture,
P.O. Box 3004, Morogoro, Tanzania.
*Ministry of Agriculture; Mwanza, Tanzania
aoaboud@yahoo.com   ;   aboud@suanet.ac.tz

Abstract

 

Two experiments were conducted to investigate the potential of water hyacinth (Eicchornia crassipes) in ruminant nutrition in Tanzania. In the first experiment , biomass yield, chemical composition, in vitro dry matter (IVDMD) and organic matter digestibility (IVOMD) and in-sacco degradability of water hyacinth were investigated. In the second experiment water hyacinth was ensiled using 0, 10 and 20% molasses levels as an additive, and subsequently analysed for dry matter (DM), water soluble carbohydrates (WSC), IVDMD and IVOMD.

 

Biomass yield (ton/ha/year) of water hyacinth was estimated as 322.2 tons (approx. 30.45 tons DM/ha/year at 9%-10% DM content) . Sun drying for 8 hours was adequate to wilt the fresh water hyacinth to a product of 15.35% DM, the chemical composition of which was 18%CP in leaves and in shoots. The whole plant showed significantly (P<0.001) lower DM digestibility (42.32%) compared to leaves and shoots (58.15 and 57.03%). No significant difference in dry matter digestibility was observed between leaves and shoots. Potential degradability was 68.09%, 60.82% and 52.91% for leaves, shoots and whole plant respectively. The rumen degradable fraction was 44.2%± 3.11 in the whole plant, 58.71%± 6.29 and 52.41%±1.38 in the leaves and shoots respectively.

 

Addition of 10% or 20% molasses to WH silage significantly (P<0.001) improved IVOMD from 42.15% in untreated silage to respectively 54.6 and 52.76% .Likewise the in-sacco DM degradability was improved from 48.53% in untreated silage to 54.76% and 54.55%. The Crude Protein (CP) content was significantly (P<0.001) lower for 10 and 20 % molasses treated silage (80.75 and 77.68 gkg^-1DM respectively) compared to untreated silage (97.61 gkg^-1DM.).

 

It was concluded that water hyacinth could provide large quantities of nutritious feed to ruminants in the Lake zone.

 

Keywords: biomass yield, chemical composition, molasses, silage, water hyacinth

 

Introduction

 

Water hyacinth (Eicchornia Crassipes) is one of the most prominent fresh water plants found throughout the tropical and sub-tropical areas. The plant occurs in nutrient rich aquatic environments such as lakes, reservoirs and fresh water streams. Pollutants from urban, industrial and agricultural activities provide essential nutrients for the growth of this aquatic macrophyte. In Tanzania the plant has been identified in rivers Pangani and Sisi, Lake Victoria and in the Mtera hydro-electric dam (Joyce 1990). Recently, massive proliferation has been reported in Mindu dam in Morogoro.

 

Water hyacinth belongs to the family Pontederiaceae. It is a floating biomass with long round spongy stems. Leaves are deep green, large and erect. Roots are variable in length from about 10 to 90 cm long (Reza and Khan 1981). The rhizomes are generally 1 to 25 cm long, occasionally producing internodes. The plant is luxuriant in growth and multiplies very rapidly. The average height of the plant is about 45 cm in mature stage but generally ranges from 30 to 70 cm (Reza and Khan 1981). The plant is characterized by formation of large floating mats that normally cover the water surface. When allowed to propagate, it quickly colonizes vast areas of water masses causing a number of problems. Some examples of detrimental effects include loss of fishing ground, provision of habitats for mosquito and bilharzias breeding, occlusion of waterways for navigation, interference with hydroelectric power sources and suppression of other useful aquatic life (El-Serafy et al 1981; Hentges et al 1972). In Lake Victoria the menace caused by water hyacinth has prompted East African governments action to control the spread of the plant by biological methods (Wulf and Andjelic 2000). Such measures if not carefully executed, could have more detrimental effects than the narrow advantages intended by the measures. Introduction of the Cactus Moth (Cactoblastis cactorum) in Austaralia is one example where biological control can easily get out of hand (Zimmermann et al 2004).

 

However, water hyacinth infestation in lakes and rivers, is regarded as a resource with a wide range of applications in China, India and Vietnam. The applications include source of biogas, animal feed and bio fertilizers (Bagnal et al 1974 and Shiralipour and Smith 1984). In Vietnam, water hyacinth flowers are used as vegetables for human (Nguyen 1996). In India and China water hyacinth has been part of human food and domestic animals especially pigs and poultry for centuries. In Egypt trials by El-Serafy et al (1981) have clearly shown that water hyacinth can be successfully incorporated in ruminants diets.

 

The regions surrounding Lake Victoria in northern Tanzania are home for the largest concentration of domestic ruminants. People living on the lakeshores and in some of its Islands survive on fishing and subsistence mixed farming. Communities such as those on Ukerewe Islands and the western shores of the lake (Bukoba) practice Zero grazing and intensive cultivation. Feed shortages for livestock is usually experienced throughout the year . Water hyacinth has not attracted the attention of farmers as a feed for livestock. Currently, there is no local use for this plant apart from few farmers raising pigs who include the fresh shoots in the diet (Kivaisi and Mtilla 1995). This is probably due to the lack of information on this plant and the fact that it was non-existent in lake Victoria until recently.

 

Water hyacinth could provide an easily accessible feed resource for livestock while at the same time its harvesting contribute to its control. At the moment the weed is harvested by mechanical means and dumped by the local people whose activities have been hampered by its infestation (Kivaisi and Mtilla 1995). This study aims to investigate the possibility of utilising water hyacinth in ruminant feeding around the Lake Victoria area of Tanzania.

 

Materials and methods

 

Site description and sampling

 

The samples for the studies were collected from lake Victoria. The lake lies between the western and eastern rift highlands in east - central Africa at an altitude of 1130 m. It covers an area of 69485 km². It is about 400 km long and 240 km wide. The greatest recorded depth is 80 m. The lake extends from 0^o 20'N to 3^o S; Latitude, from 31^o 40' to 34^o 52'E (Wulf ,and Andjelic 2000). Ensiling was carried out at Kamanga ferry point in Mwanza where a farmer provided a place for wilting and storage.

 

Harvesting , yield estimates and silage making

 

A boat was used to reach the sampling site. Potential yield was estimated using a floating wooden square of 0.25 m² at three different locations . Using a small boat the square was tossed ten times and each time plants falling in it were harvested . After harvesting the samples were weighed and dried under the sun for six days. After this period the samples were weighed again and the weights recorded for the dry matter calculation.

 

For silage making , freshly harvested plant shoots were lacerated and separated from the roots. Lacerated samples were further chopped using knives and then wilted under the shade for 48 hours on 6 x 8-m polythene sheets. The material was then weighed and mixed with molasses at levels of 10% and 20% of the weight to be ensiled. Samples with no molasses were also ensiled as control. All were replicated six times in a completely randomized design.

 

Experimental silos

 

Plastic buckets of 20 litres capacity were used as silos. Ensiling was done by rapid compaction of the materials into the buckets (silo). Predetermined quantities of molasses was sprinkled during the filling process. Sealing of the silo was effected by placing a 1 kg plastic bag of sand on top of the material before the lead was replaced.

 

Monitoring of pH changes

 

Six replicates of materials treated in the same manner as those ensiled in buckets were ensiled in twenty four plastic containers (5lt capacity) for monitoring pH changes for four weeks. Samples were drawn from individual containers once every week for pH determination .

 

Silage sampling for chemical analysis

 

Immediately after opening the silos (20 litre buckets), 400 gms of samples were taken by drawing portions from different depth of silos and mixed up to ensure homogeneity of the samples. Fresh silage samples were deep frozen for subsequent chemical analysis of fermentation products . For dry matter, organic matter, CP, NDF, ADF, and In vitro DM and OM digestibility and degradability determinations , air dried samples were used as described by AOAC (1990), Goering and Van Soest (1970) and Van Soest et al (1991). In-vitro methods of Tilley and Terry (1963) were used for the determination of IVDMD and IVOMD. Degradability of DM and OM were estimated by in-sacco methods as described by Ærskov et al (1989).

 

In sacco degradability determination

 

Degradability of water hyacinth parts and silage was done using the nylon bag technique described by Ørskov et al (1989). The nylon bags used had a pore size of 40 mM. For each sample 3 gm were weighed and the incubation periods were 6, 12, 24, 48, 72, 96, and 120 hours. The data obtained were fitted to the equation as described by Ørskov et al (1980) and Ørskov et al (1989) i.e.
 

P = a + b(1-e^-ct)

Where:

a, b, and c are constants and
P is the percentages of material degraded after time t in hours :
a = intercept of the degradation curve,
b = potential degradability,
c = rate of degradation,
t = time in hours.

 

Estimates of effective degradability were calculated using the formula:
 

Y = a+bc/(c+k)

Where:
Y = effective degradability;
a = water soluble component;
b = insoluble but potentially rumen degradable part;
c = rate of degradability of insoluble material

k = passage rate .

 

Analysis of Fatty Acids and Water soluble carbohydrates

 

Fatty acids ( Propionic, Butyric and Lactic acids ) were determined using gas - liquid chromatography (GLC) as by the procedures of AOAC (1990) whereas water soluble carbohydrates (WSC) were determined spectrophotometricaly as described by Thomas (1977) .

 

Data analysis

 

Data on comparative chemical parameters were analyzed by the GLM procedures as described by SAS (1988). A complete randomized model was adopted for analysis of variance with the means tested by least significant difference (LSD).

 

Results and discussion

 

Yield and chemical composition

 

Table 1 shows the dry matter yield and chemical composition of water hyacinth and its botanical fractions. Biomass yield (ton/ha/year) of water hyacinth was estimated as 322.2 tons (approx. 30.45 tons DM/ha/year at 9%-10% DM content) .This estimate is substantially lower than most estimates in the literature (El-Serafy et al 1981; Nguyen 1996). Sampling was done on floating masses which were subject to changes in tidal waves. This may have affected the sampling field. However, since readings were taken from various sites it can be stated that the estimates were a fair indication of the yield at those particular sites. It was also notable that sampling made near the wharf gave lower values than those taken far offshore. The biomass yield recorded here is substantially higher than most of the conventional pastures in East Africa (Kidunda 1988). At an estimated daily dry matter requirement of 6-10 kg by a Tropical Livestock Unit (TLU) (Pratt and Gwynne 1978), 1 hectare water hyacinth should be able to support 8 - 15 TLU per annum. 

The range of values recorded for all chemical constituents fall within ranges reported in the literature (Nguyen 1996). The high CP content of leaves and shoots can be considered as favourable for feeding to ruminants. This level is comparable to common leguminous fodder available in Tanzania (Shayo,1992) and may be considered as a valuable supplement for animals fed on low quality crop residues along the Lake shores. Water hyacinth is widely used in pig and donkey feeding in the far east ( MacMillan 1956). This suggests that its digestibility is not a limiting factor and that when used in ruminants the high protein content could be of benefit even for the young or lactating ruminants. Similar suggestions have been given by Reza and Khan (1981) and El-Serafy et al (1981). The ash content of the entire plant was high which is a common characteristic of aquatic plants (Nguyen 1996). Studies by MacMillan (1956) had shown that water hyacinth is rich in potash. This characteristic could make water hyacinth a potential source of fertlizer both in its fresh form and when voided by livestock as manure.

 

In vitrodry matter digestibility and in-sacco dry matter degradability of water hyacinth

 

The mean DM digestibility and degradability values of water hyacinth parts obtained by two stage in vitro rumen liquor and nylon bag incubation techniques are shown in Table 2. 

Significantly lower (P<0.001) digestibility and degradability values were shown for the entire plant (WHE). No significant (p>0.05) differences were shown between leaves (WHL) and stems (WHS). The values for digestibility and degradability were substantially higher than values reported for forages available around Lake Victoria ( Kakengi et al 1999). Tables 2-4 show that with or without molasses the rumen DM degradability of water hyacinth compares favourably with most of the conventional tropical forages (Mgheni et al 1993). This further supports the need for inclusion of water hyacinth into potential feed resources in Eastern Africa and could form an important feed base for smallholder farmers.

 

Silage quality and effects of addition of molasses:

 

Table 3 and 4 show the chemical composition of pre and post ensiled water hyacinth and the effects of addition of molasses on the quality of silage from water hyacinth. Addition of molasses at 10 and 20 % improved the DM by 6.12 and 9.98 units respectively. This was expected since molasses added to the material some DM which mainly comprised of soluble sugars. The CP content of molasses treated material was significantly (P>0.005) lower than that in untreated material. However, this was largely attributed to the dilution resulting from the addition of molasses which had about 3% crude protein. It was notable that, the CP value of post-ensiled untreated material decreased significantly (p>0.005), while that of molasses treated material remained the same (Table 3).

This suggests that addition of molasses had positive effect on preservation of water hyacinth. It can be noted that without molasses treatment, the pH , NH₃N and the butyric acid values for WH silage were above the accepted limits for good quality silage (Crowder and Chheda 1982). Molasses improved the acidity as noted in the treated materials (Table 4).

In a study on potentials of water hyacinth as feed for ruminants, El-Serafy et al (1981) showed that water hyacinth leaves and stem contain as much as 18% crude protein, a value close to findings in the present study (Table 1) . Such high protein values may cause problems of rapid proteolysis during silage making especially where rapidly fermenting additives are not used (Carpintero et al 1969; El-Serafy et al 1981; McDonald et al 1991).

 

Addition of molasses had inconsistent effect on the content of WSC in post-ensiled material, apart from the increase in value which is a direct consequence of molasses inclusion. Similarly, the seemingly high values of in vitro DMD and OMD (Table 3) could also be attributed to the addition of molasses (McDonald et al 1973; Van Soest et al 1991).

 

Conclusion

 

This study has demonstrated the potential feed value of water hyacinth. Deliberate production of water hyacinth is not suggested. This is because without extreme care , water hyacinth can easily turn into a serious environmental hazard. However, since massive amounts already exist, it would be prudent to suggest additional form of utilisation which may compliment the current efforts of controlling the plant. At an extraction rate of just 6 ton DM/TLU/year, it should be possible to substantially reduce the current proliferation of water hyacinth in Lake Victoria. Because of its high moisture content, pre -wilting and addition of molasses during ensiling appear to be the most practical way of improving the utilisation of the plant, a form that would be a significant contribution to dry -season feeding along the Lake shores.

 

Acknowledgement

 

The authors wish to thank the department of Animal science of Sokoine University for the financial support during the course of the study. We also wish to thank NORAD for sponsoring the data collection exercise.

 

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