Utilization of tropical kudzu leaves (Pueraria phaseoloides) as a protein source for growing rabbits
 

Nguyen Van Hiep and Ngo Van Man

Faculty of Animal Science and Veterinary Medicine,

Nong Lam University, Vietnam

nguyenvanhiep5@yahoo.com

Abstract

This experiment was carried out to evaluate the effect of replacing soybean residue with Kudzu leaves as a supplement for growing rabbits fed a basal diet of Guinea grass ad libitum.  Thirty-two rabbits equally balanced for sex, 6 to 7 weeks of age and with an average body weight of 588 g were used. The treatments were: Guinea grass ad libitum and soybean residue at 5% of live weight (DM basis) (Control); K25 Similar to the Control  but with  Kudzu leaves offered to replace25% of the soybean residue; K50 Similar to K25 but with 50% replacement offer of soybean waste by Kudzu leaves; K75 Similar to K25 but with 75% replacement of soybean waste by Kudzu leaves.

Total DM intake, recorded dietary content of crude protein, growth rate and feed  conversion, all showed  negative curvilinear relationships with increasing offer of Kudzu leaves.  It would appear that the maximum degree of substitution of the soybean waste by kudzu foliage was about 20% with declining performance beyond that level. The observed intakes of kudzu leaves were much lower than the planned levels indicating that palatability was probably the limiting factor determining the nutritive value of Kudzu leaves.

Key words: Feed conversion, feed intake, growth rate, Guinea grass, soybean residue

Introduction

Rabbits are raised in almost all developing countries, and contribute to improving the nutrition and economy of smallholder families, both as a source of animal protein as well as a source of extra income. In recent years, rabbit production in Vietnam has developed rapidly to meet an increased demand for fresh meat for human consumption to replace the shortfall in supplies of meat of poultry as a result of avian influenza.

The basal diet of most rabbits in Vietnam is based on roadside grass and agricultural by-products that are not suitable for other live stock. The nutritive value of these feeds is low. To overcome this problem feed supplements are normally provided. Cereal-based feeds are generally too expensive for use as supplements. It is argued that a major priority is to develop livestock feeding systems which do not depend on cereal grains (Preston, 1995).

Considerable progress has been made in the use locally available forages such as water spinach (Hongthong Phimmasan  et al 2004; Nguyen Thi Kim Dong et al 2006; Doan Thi Gang et al 2006; Tran Hoang Chat et al 2005), sweet potato vines (Doan Thi Gang et al 2006), head lettuce and mimosa (Nakkitset 2007).

Tropical Kudzu (Pueraria phaseoloides) is a leguminous plant that has relatively high levels of crude protein in the range of 12 to 24 % in DM (Hiep et al 2008). In Vietnam, Kudzu has been intercropped with rubber trees to improve soil fertility (Photo 1).

According to the report of the Vietnam General Rubber Corporation (2005) in the Southeast region of the country the total newly established or replanted rubber area was 17,251 ha, of which 6,292 ha have been inter-planted with Tropical Kudzu or Mucuna (Mucuna pruriens). The report of Dongnai Rubber Company (2005) showed that biomass production of Kudzu in the rainy season was 36.7, 57.1 and 39.2 tonnes/ha fresh matter tons/ha in the first, second and third years, respectively. Only one cutting per year at the end of the rainy season is applied in the rubber companies in the region. The whole biomass of the cover-crop is used as green manure. There appear to be no reports in Vietnam of using the Kudzu as animal feed other than those of Hiep et al (2008) where the Kudzu was ensiled or fed fresh to growing cattle.

The present study aimed to determine the optimum level of Kudzu leaves as replacement for soybean waste in diets of growing rabbits fed a basal diet of Guinea grass.

 
Materials and methods

Location

The experiment was conducted in 2008 at the Experimental farm of the Faculty of Animal Science and Veterinary Medicine, Nong Lam University, Ho Chi Minh city.

Animals and management

Thirty-two rabbits equally balanced for sex, 6 to 7 weeks of age and with an average body weight of 588 g were used. They were allocated in pairs (one male and one female) to each of 16 cages. They were dewormed before the start of the experiment by Ivermectin injection.

Experimental design

The experimental design was a randomized complete block (RCBD) with 4 treatments and 4 blocks. The experimental period lasted 8 weeks: The treatments were:

• Control: Guinea grass ad libitum and soybean residue at 5% of live weight (DM basis)

• K25: Similar to the control but with Kudzu leaves offered to replace 25% of the soybean residue

• K50: Similar to K25 but with 50% replacement offer of soybean waste by Kudzu leaves

• K75: Similar to K25 but with 75% replacement offer of soybean waste by Kudzu leaves

Feeds and feeding systems

Soybean residue (Photo 2) was bought from households that process soybean cake every day and was dried in an oven for 4 hours at 900C. Kudzu was planted in the farm area and the leaves harvested after 4 months of growth. Quantities of soybean residue and Kudzu leaves were adjusted every week according to the body weight of the rabbits. Guinea grass (Panicum maximum cv.280) was planted in the farm area and was harvested at 4 weeks of age to be used as the basal feed (offered at 120% of the average intake the previous week).  

 Data collection and analysis

The rabbits were weighed at the beginning of the experiment and then every week always in the morning before feeding. Feeds offered and refused were weighed every day to calculate feed intake and determine feed conversion ratio. The samples of feed and feed residues were analysed for DM, organic matter (OM), Ether extract and crude fiber by AOAC (2000) procedures.

Statistical analysis

The data were analyzed using the GLM option in the ANOVA program of the Minitab (version 13.3) software (Minitab 2000). Sources of variation were: block, treatment and error. The means were compared using Tukey’s pairwise comparison test in the same Minitab software.
 

Results and discussion

Kudzu leaves were lower in organic matter and crude protein and higher in fibre compared to soybean residue (Table 1). The DM percentage was similar in Kudzu leaves and soybean residue.

Total DM intake, recorded dietary content of crude protein and crude fiber, growth rate and feed  conversion, all showed  curvilinear relationships with increasing offer of Kudzu leaves (Table 2: Figures 1-5) .  It would appear that the maximum degree of substitution of the soybean waste by kudzu foliage was about 20% with declining performance beyond that level. The observed intakes of kudzu leaves were much lower than the planned levels indicating that palatability was probably the limiting factor determining intake. Recorded levels of diet crude protein decreased and those of crude fiber increased with increasing replacement of soybean waste by kudzu leaves. However, crude protein levels on all diets were higher than those reported to sustain normal growth of rabbits on forage-based diets (Pok Samkol et al ; Chat et al ). Crude fiber levels were higher than in the diets used by Pok Samkol et al ) but increased only slightly with increase in kudzu in the diet. A lower digestibility of the protein in the kudzu leaves is a possible explanation for the lower intakes, but this was not measured in the present experiment.

Figure 1. Effect on DM intake of growing rabbits of replacing soybean waste with kudzu foliage

Figure 2. Effect on diet crude protein content of replacing soybean waste with kudzu foliage	Figure 3. Effect on diet crude fiber content of replacing soybean waste with kudzu foliage

The growth curves of the rabbits (Figure 6) show conclusively that growth rates were depressed when the Kudzu leaves replaced more than 29% of the soybean waste.

Conclusions

• There would appear to little potential to incorporate Kudzu leaves in the diet of growing rabbits. The maximum 28% replacement of the soybean waste by \Kudzu leaves was equivalent to only 15% of the total diet.

Acknowledgements

The authors wish to acknowledge the MEKARN project, financed by SIDA/SAREC, for supporting this experiment. We also wish to thank the Faculty of Animal Science and Veterinary Medicine, Nong Lam University of Vietnam, for providing part of the facilities to carry out the experiment.

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