Performance of West African Dwarf goats fed graded levels of sun-cured water hyacinth (Eichhornia crassipes Mart. Solms-Laubach) replacing Guinea grass

Adejoke Adeneye Mako

Department of Agricultural Production and Management Sciences
Tai Solarin University of Education, Ijagun.Ijebu-Ode
PMB, 2118, Ijebu-Ode.Ogun State, Nigeria.
Jokemako2006@gmail.com

Abstract

The objective of this study was to evaluate the performance of goats fed water hyacinth (WH) based diets. The chemical composition of sun-cured WH, Guinea grass (GG) and concentrate was determined. Quantitative analysis of tannins, saponins and phenols present in WH and GG were also determined. Thirty (30) female WAD goats between the ages of 6 and 7 months weighing 8.40 - 9.60 kg were used for a feeding trial.. Six animals were allotted to each of 5 treatments in a completely randomized design. Parameters measured included feed intake and weight gain.

WH and GG contained tannins, saponins and phenols, but the concentrations were below toxic levels. The feed intake and weight gain had a negative curvilinear relationship with increasing level of WH in the diets. It is concluded that in diets based on Guinea grass the maximum level of sun-cured water hyacinth in diets for growing goats is 30%.

Key words: bypass protein, heavy metals, non-nutritional compounds, ruminants, secondary metabolites

Introduction

The major constraint of livestock in Nigeria is the inadequate and fluctuating year round supply of feed. Population explosion coupled with competition between people and livestock further compounds the problem, resulting in rising costs of the conventional feedstuffs and reduction in the available land for forage production.

In Nigeria, ruminants obtain most of their nutrients from herbages growing on poor soils and crop residues. The crop residues and roughages are bulky with high fiber, low protein and often poorly degraded.  Therefore sustainability of livestock on grasses, crop residues alone becomes difficult. To ameliorate this deficiency, cheap, readily available, easy and safe to handle feed alternatives need to be sought.

This therefore is calling for renewed investigative studies that will establish the sustainability of some less frequently utilized forages such as water hyacinth , which do not compete outrightly with other agriculturally useful vegetation for growing space. With protein content of 11.6 %, the foliage may be nutritious to ruminants and could make a useful feed supplement (Dada 2002). The yield is high during the dry season. Water hyacinth has been shown to be degradable and digestible by goats (Dada 2002). 

This study was therefore designed to evaluate the effects of sun-cured water hyacinth with Guinea grass and concentrates on the growth of  WAD goats.

Materials and methods

Experimental site

The experiment was carried out at the goat unit of the Teaching and Research Farm Tai Solarin University of Education, Ijagun, Ijebu-Ode (7⁰ 15¹ N to 7⁰ 40¹ E) between December 2007 and March 2008. 

Experimental animals

Thirty (30) weaned female West African dwarf goats of 6-7 months of age weighing 8.40 - 9.60 kg were used for the experiment. They were purchased from Oyo town in Oyo state. On arrival, the goats were given prophylactic treatments, which consisted of intramuscular application of oxytetracycline and vitamin B complex, at the dosage of 1 ml/10 kg body weight of the animal. They were also drenched with albendazole to control endoparasites and treated for mange and other ectoparasites using ivomec^R. They were later vaccinated against Pestes des Petits ruminante (PPR) using a Tissue Culture Rinderpest Vaccine at the dosage of 1 ml per animal.

During the adaptation period for six weeks, the goats were offered the feeds they were consuming where they were purchased (cowpea husk and Guinea grass).

Collection of water hyacinth and Guinea grass

Water hyacinth was collected from river Ogun (Odogbolu Local Government area in Ogun State), between December 2006 and February 2007, the roots were discarded and the foliage was sun dried and bagged until needed. A six week regrowth Guinea grass was harvested from a pasture land of the Teaching and Research Farm, Tai Solarin University of Education, Ijagun, Ijebu-Ode. Nigeria. Known weights of sun-cured water hyacinth and Guinea grass were oven dried at 105 ⁰C  for dry matter determination.

Management

On arrival, the goats were allowed six weeks to become acclimatized to the experimental diets with gradual withdrawal of the usual diets which they ate from where they were purchased. The thirty (30) female WAD goats were weighed and randomly allotted to five treatments in a completely randomized design.

The  treatments consisted of ratios (% DM basis) of Guinea grass (GG), sun-cured water hyacinth foliage (WH) and concentrate supplement (CS; Table 1) as follows:

• WH0: 0 WH,  90 GG and 10 CS

• WH30: 30 WH, 60 GG and 10 CS

• WH45: 45 WH, 45 GG, 10 CS

• WH60: 60 WH, 30 GG, 10 CS

• WH90: 90 WH, 10 CS

Water hyacinth was fed at 0800 h,  Guinea grass at 1600 h and concentrate supplement at 1800 h each day. Refusals were weighed the following morning. The offer level was approximately 5 % (as DM) of LW and was frequently adjusted to ensure that each animal received about 20 % of feed above its previous days consumption. Samples from refusals were taken for proximate composition. Fresh water was served each day; salt lick was placed permanently in each pen. Weights of the goats were taken before the commencement of the experiment and subsequently once weekly. The goats were weighed in the morning before feeding.

Chemical analysis of feed ingredients

Representative subsamples were dried in a forced drought oven at 105-110 ^o C to a constant weight for DM determination. Crude protein, crude fibre, ether extract, and total ash were analyzed in triplicate according to AOAC (1995) procedures. The neutral detergent fibre (NDF), acid detergent fibre (ADF) and acid detergent lignin (ADL) contents were determined as prescribed by Van Soest et al (1991).

Quantitative determination of tannin, phenol and saponin

Tannin content was determined as described by Swain (1979);  0.20g of sample was measured into a 50ml beaker, 20ml of 50% methanol was added and covered with paraffin and placed in a water bath at 77-80^oC for 1 hour. It was shaken thoroughly to ensure a uniform mixing. The extract was quantitatively filtered using a double layered Whatman No 41 filter paper into a 100ml volumetric flask, 20ml water added, 2.5ml folin-Denis reagent and 10ml of 17% Na₂CO₃ were added and mixed properly. The mixture was made up to mark with water mixed well and allow to stand for 20 min. The absorbance of the Tannic acid standard solution as well as the samples was read after color development on a spectronic 21D spectrophotometer at a wavelength of 760nm.

Phenols were determined as described by AOAC (1984): 0.20g of sample was weighed into a 50ml beaker, 20ml of acetone was added and homogenized for 1hr to prevent lumping. The mixture was filtered through a Whatman No.1 filter paper into a 100ml Volumetric Flask using acetone to rinse and made up to mark with distilled water with thorough  mixing. 1ml of sample extract was pipetted into 50ml Volumetric flask, 20ml water added,  3ml of phosphomolybdic acid added followed by the addition of 5ml of 23% NaCO₃, mixed thoroughly, made up to mark with distilled water and allowed to stand for 10min to develop bluish-green colour. A standard phenol (concentration range 0-10mg/ml) was prepared from 100mg/liter stock phenol solution (Sigma-Aldrich chemicals, USA). The absorbance of samples as well as that of standard concentrations of Phenol was read on a Digital Spectrophotometer at a wavelength of 510nm.

The spectrophotometric method of Brunner (1984) was used for saponin analysis: 1g of finely ground sample was weighed into a 250ml beaker and 100ml of isobutyl alcohol was added. The mixture was shaken on a UDY shaker for 5 hours to ensure uniform mixing . Thereafter the mixture was filtered through a Whatman No1 filter paper into a 100ml beaker and 20ml of 40% saturated solution of magnesium carbonate was added. The mixture obtained with saturated MgCO₃ was again filtered through a Whatman No1 filter paper to obtain a clear colorless solution. 1ml of the colorless solution was pipetted into 50ml volumetric flask and 2ml of 5% FeCl₃ solution was added and made up to mark with distilled water. It was allowed to stand for 30min for blood red color to develop. 0-10ppm standard saponin solutions were prepared from saponin stock solution. The standard solutions were treated similarly with 2ml of 5% FeCL3 solution as done for 1ml sample above. The absorbance of the sample as well as standard saponin solution was read after color development in a Jenway V6300 Spectrophotometer at a wavelength of 380nm.

Determination of heavy metal constituents

Mineral constituents As, Cd, Hg and Pb were determined from samples upon digestion with a mixture of concentrated HNO₃, H₂SO₄ and HClO₄ in the ratio (10:05:2) (v/v) and the digest obtained was aspirated into a Buck 211 VGP Atomic Absorption Spectrophotometer at known wavelength and with hollow Cathode lamp specific to each mineral element. 1 ppm standard solution of each metal was prepared and read on the AAS before the reading of the sample digest to standardize the instrument to ensure accuracy of reading. The reading for each sample as well as standard solutions was obtained from the read-out unit of the Atomic Absorption Spectrophotometer (AAS).

Statistical analysis

Relationships between water hyacinth level and DM intake and live weight gain were analysed by regression, with proportion of water hyacinth in diet DM as the independent variable and DM intake and live weight gain as independent variables.

Results

Chemical composition

The content of phenols and saponins were much higher in the water hyacinth than in Guinea grass (Table 2), whereas tannins were present in higher amounts in the Guinea grass.

The concentrations of potentially toxic heavy metals (Table 3) were all below the recommended maximum values according to the EC (2008).

 DM intake and live weight gain decreased with a curvilinear trend as water hyacinth replaced guinea grass (Table 5; Figures 1 and 2).

Figure 1. Trend in DM intake as water hyacinth replaced guinea grass	Figure 2. Trend in live weight gain as water hyacinth replaced guinea grass

Discussion

It appears that the maximum level of sun-cured water hyacinth as replacement for Guinea grass is about 30% of the diet DM, after which there was a rapid and marked reduction in feed intake and live weight gain as water hyacinth replaced Guinea grass. Most reports in the literature indicate that water hyacinth should not be fed as the sole or major part of the diet. Thus Hentges (1970) found that cattle could not eat enough fresh water hyacinth to cover their maintenance requirement. Kahn et al (2002) also reported that green water hyacinth alone was insufficient for the maintenance of bullocks as the animals lost 23 g/day of live weight during a period of 60 days. However, when rice straw was given together with the water hyacinth (1:1 ratio) the bullocks increased their DM intake by 67% and gained 68g/day of live weight. Ho Thanh Tham (2012) reported that above 30% in the diet rumen distention became a limiting factor in cattle fed water hyacinth.

In looking for an explanation for these negative results of high levels of water hyacinth in the diet, it has to be emphasized that in the present study the nutritive value of water hyacinth appeared to be higher than that of Guinea grass, as assessed by higher crude protein and lower cell wall contents. An earlier study also predicted a relatively high nutritive value for water hyacinth as indicated by in vitro digestibility data (Mako et al 2011). 

The most dramatic response in growth of cattle fed a basal diet of water hyacinth leaves was when they were supplemented with sun-dried cassava foliage (Sophal et al 2010). The major degree of improvement in growth rate (from -17g/day to +243 g/day) was ascribed by Sophal et al (2010) to be due to the rumen bypass characteristics in cassava foliage as first reported by Ffoulkes and Preston (1978). This finding of the benefits of supplementing a diet of water hyacinth with a supplement rich in bypass protein merits further investigation. Major benefits from supplementing water hyacinth leaves with protein-rich foliages were demonstrated by Thu Hang et al (2013). The growth rates of goats were doubled (from 35 to 66 g/day) when fresh water hyacinth leaves were supplemented with foliage of Sebania sesban, a leguminous tree the foliage of which is considered to be rich in bypass protein (Thu Hang et al 2013).  These authors also reported similar growth rate increases when water spinach or sweet potato vines were fed replacing Guinea grass. Both sweet potato vines and water spinach are rich in protein (>20% in DM). Another important observation from these authors was that feed intake was some 50% greater and N retention doubled when only the leaves of water hyacinth were fed, rather than leaves plus stems.

Conclusion

• The maximum level of sun-dried water hyacinth as replacement for Guinea grass in the diet of goats appears to about 30%. Complete replacement of Guinea grass by water hyacinth barely supported maintenance even with a supplement of 10% of concentrates. 

• Future research with water hyacinth for ruminants should be based on feeding of the leaves only, not leaves and stems, and that the appropriate supplements will be protein-rich foliages, especially those considered to be good sources of bypass protein.

References

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Received 26 June 2012; Accepted 22 May 2013; Published 1 July 2013

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