A study of water hyacinth (Eichhornia crassipes) as a feed resource for feeding growing rabbits

Nguyen Van Thu and Nguyen Thi Kim Dong

Faculty. of Agriculture and Applied Biology, Cantho University
Cantho, Vietnam
nvthu@ctu.edu.vn

Abstract

A study consisting of two experiments for evaluating the effect of different water hyacinth levels replacing para grass in the diet on nutrient digestibility, daily weight gain and economic returns of crossbred rabbits was conducted at Cantho University. In the feeding experiment, seventy two rabbits at 8 weeks of age were arranged in a completely randomized design with 6 treatments and 3 replications. The treatments were water hyacinth (WH) replacement to para grass (DM basis) at levels of 0 (WH0), 20 (WH20), 40 (WH40), 60 (WH60), 80 (WH80) and 100% (WH100). In the digestibility experiment, the similar experimental design was done with 72 rabbits at 14 weeks of age for evaluating nutrient digestibility and nitrogen retention. The results indicated daily weight gain and feed conversion ratio were significantly different among the diets (P<0.001). The daily weight gain was 18.9, 19.3, 19.6, 19.0, 16.2 and 14.0 g/rabbit/day for WH0, WH20, WH40, WH60, WH80 and WH100 diet, respectively. The apparent digestibility of DM, OM, CP, NDF and nitrogen retention tended to increase proportionally to the increasing levels of water hyacinth replacement in the diets up to 60%. The statistically significant differences were found in NDF digestibility and nitrogen retention (P<0.05). It was concluded that water hyacinth could be used for feeding growing rabbits for improving nutrient digestibility, nitrogen retention, growth rate and profit with the level from 40 to 60% (DM basis) in the diet.

Key words: water hyacinth, crossbred rabbits, para grass, digestibility, economic return

Introduction

Rabbit production has been recommended for development to satisfy meat demand of society, because the rabbit can produce meat quickly by efficient reproduction. Rabbit meat has been also considered as good meat for high protein of 21.3%, low fat content of 6.80% and low cholesterol of 45mg/kg. The cost for rabbit production is lower than the other animal species ones, and especially feed sources for rabbits such as grasses, wild and planted vegetables and local energy and protein feed supplementation, which do not compete with human beings. In the Mekong delta of Vietnam water hyacinth grows well in canals, ponds and rivers, and in many cases it causes the environmental problems. It has been also under-utilized for animal production. Therefore this study aimed to evaluate the possibility of using water hyacinth for meat rabbit production.

Materials and methods

The experiment was carried out at the Cantho University from December in 2008 to April in 2009. Seventy two rabbits at 8 weeks of age were arranged in a completely randomized design of a feeding trial with 6 treatments and 3 replications. Four rabbits with balance of sex was in a experimental unit. The treatments were water hyacinth (WH) replacement to para grass (PG) based on DM basis at levels of 0 (WH0), 20 (WH20), 40 (WH40), 60 (WH60), 80 (WH80) and 100% (WH100) water hyacinth. In the digestibility experiment, the similar experimental design was done with 72 rabbits at 14 weeks of age for evaluating nutrient digestibility and nitrogen retention. Dry cassava root was supplemented of 25-30g/day/animal and soya waste was fed 15-30g/day/animal  based on the ages for the energy and protein requirement of the rabbits.

The measurements taken were feed and intake of dry matter (DM), organic matter (OM), ash, neutral detergent fiber (NDF), daily weight gain, feed conversion ratio, economic returns, nutrient digestibility and nitrogen retention..

The feeds and refusals were taken for analyses of DM, OM, CP, NFE, Ash, NDF and Ash following procedure of AOAC (1990) and Van Soest et al. (1991). Data were analyzed by General Linear Model (GLM) of Minitab program 13 (Minitab, 2000) and the comparison of significant difference between two treatments was done by Tukey method of Minitab program.

Results and discussion

Exp 1 Feeding trial

Feed chemical composition is shown in Table 1.

The DM and CP contents of WH were 7.63 and 11.7%, respectively.  The results in this study were higher than those indicated by Huynh Van Thuan (2009). The CP content of soyabean waste was 19.1%. It was used as a protein supplemental source in the diet. The NDF content of WH was lower than that of para grass.

The WH intake was gradually increased from the WH0 to WH80, but reduced in WH100 treatment (P<0.001) (Table 2). The higher DM intakes were found in the WH0 to WH80 diets, and considerably lower value when the rabbits fed WH only. These values were similar to those of study indicated by Nguyen Thi Kim Dong and Nguyen Truong Giang (2008). The crude protein intakes were significantly different (P<0.05) among the treatments with the higher values in the treatments of WH40, WH60 and WH80. The range of CP content in the present study was from 6.81 to 8.53g, and this value was lower than that stated by Dao Hung (2006). The NDF intake was significantly reduced from WH0 to WH100 (P<0.05). The explanation was water hyacinth had lower NDF content than that of para grass. Metabolizable energy intakes were significantly different among the treatments with the highest value of the WH60 diet (0.61 MJ/rabbit/day).

Table 3 shows that the daily weight gain of the WH0, WH20, WH40 and WH60 treatments was significantly higher than that of the WH80 and WH100 (P<0.05). The WH40 treatment gave highest value (19.6g/day). The final live weights were also significantly different (P<0.05) among the treatments and corresponding with daily weight gain. The feed conversion ratio ranged in 3.63 - 4.37, and being better than that reported by Nguyen Van Thu and Nguyen Thi Kim Dong (2008). The economic 8returns were similar to the pattern of the daily weight gain, with the highest value of the WH40 treatment.

Expiment 2. Digestibility trial

The results of the digestibility trial are shown in Tables 4, 5 and 6.

The chemical compositions of feeds used in the digestibility trial were similar to those of the feeding experiment.

The DM intake of the WH60 diet was the highest value (75.6g/rabbit/day) while the value of WH100 was the lowest (61.5 g/rabbit/day). The range of DM intake in this study was similar to the report of Nguyen Van Thu and Nguyen Thi Kim Dong (2005) (63.8 - 76.9gDM/rabbit/day), but being lower than the value of  72.3 - 80.5gDM/ rabbit/day stated by Cuong (2008). The CP intakes slightly increased when increasing WH in the WH20 to WH60 diets (8.30 -  8.73g/rabbit/day). However, the CP intake significantly reduced (P<0.01) when rising water hyacinth up to100 % in the diet.

In present study daily intake of NDF ranged in 19.6 - 32.6gNDF/rabbit. These results were considerably higher than the values of 21.5 - 26.3g/rabbit of the previous study reported by Truong Thi Anh Thu (2008). Metabolizable energy intakes were significantly different among the treatments, and the highest value was found in the WH60 diet (0.70MJ/rabbit/day).

Apparent nutrient digestibility (%) and nitrogen retention (g/kg W^0.75) of rabbits are shown in Table 6. There was no significant difference in the pattern of apparent digestibility of DM, OM, CP, except for NDF digestibility. The digestibility coefficient was higher in the diet included 60 % of water hyacinth. The CP digestibility ranged in 58.8 - 70.1% that was lower than those reported by Dong (2006) being from 82.0 to 84.5% and Khuc Thi Hue and Preston (2006) being from 83.9 to 90.8%. There was significant increase of NDF digestibility among the treatments (P<0.05). The higher values were found when rabbits were fed the diets contained 40% and 60% water hyacinth (45.7% and 49.9%, respectively) as compared to the remains. The results were consistent with the values from 42.0 to 51.6% in findings reported by Dang Hung Cuong (2008). Nitrogen intake and nitrogen retention slightly increased with increasing water hyainth level from 0 to 60%, while these values significantly decreased (P<0.05) when rising water hyacinth in the diets up to 80 -100%.

Conclusions

The conclusion was that water hyacinth could be used for feeding growing rabbits for improving nutrient digestibility and nitrogen retention. The replacement of water hyacinth from 40 to 60% (DM basis) to para grass improved the feed utilization, growth performance and economic returns.
 

References

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