Effects on growth of rabbits of supplementing a basal diet of water spinach (Ipomoea aquatica) with vegetable wastes and paddy rice

Nguyen Huu Tam, Vo Thanh Tuan, Vo Lam, Bui Phan Thu Hang and T R Preston*

Angiang University, Faculty of Agriculture and Natural Resources, Vietnam
bpthang@agu.edu.vn
* TOSOLY, AA48 Socorro, Santander, Colombia

Abstract

Thirty-two weaned crossbred rabbits (New Zealand x local female) with an initial weight between 900 and 1100 g and 6 and 7 weeks of age were used to evaluate the potential of the market wastes of Brassica species and of a supplement of paddy rice on feed intake and live weight change. The basal diet was fresh water spinach offered at 10% of live weight (DM basis). The design was a 2*4 factorial the factors being: (i) with or without paddy rice; (ii) supplements of Cabbage, Chinese cabbage, Cauliflower or no supplement. The vegetable supplements were offered ad libitum. Paddy rice was given at 50 g/day.

Rabbits had higher feed intake and live weight gain when: they were supplemented with  paddy rice and when they had access to cabbage, cauliflower and Chinese cabbage as well as water spinach.

Key words: Brassica species, cabbage, live weight gain, paddy rice

Introduction

Rabbits are herbivores and in Vietnam are usually fed by grasses and vegetables produced in farmers’ home gardens (Nguyen Quang Suc et al 1996). Water spinach (Ipomoea aquatica) has high biomass yield and is rich in crude protein content (280 g/kg DM), with low crude fibre (120 g/kgDM)  (Ly Thi Luyen 2003; Ho Bunyeth 2003) and has proved to be a valuable basal diet for rabbits (Hongthong Phimmmasan et al 2004). Vegetable wastes from the markets (Brassica species, such as cauliflower, cabbage and Chinese cabbage) are also potential feeds for rabbits

Experiments to improve the nutritional balance in diets based on water spinach by supplementing with highly digestible carbohydrate in the form of broken rice were not successful in the experiment reported by Hongthong Phimmmasan et al (2004). By contrast, providing supplements rich in fibre improved rabbit growth rate on basal water spinach diets (Khuc Thi Hue and Preston 2006; Doan Thi Gang et al 2006). 

It was hypothesised that paddy rice, which combines both fibre and starch, might be an appropriate supplement  in diets based on protein-rich vegetables such as water spinach and cabbage. 

The objectives of this study were therefore to evaluate the potential of the market wastes of Brassica species in rabbit feeding and to determine the response to supplementation with paddy rice.

Materials and methods

Location, experimental design and treatments

The experiment was done at the experimental farm of Angiang University, Chauphu district, Longxuyen city, Vietnam. Thirty-two weaned crossbred rabbits (New Zealand x local female) with an initial weight between 900 and 1100 g and ages between 6 and 7 weeks were used.  The experiment was a 2*4 factorial in a complete randomized design with 4 replications. The basal diet was fresh water spinach offered at 10% of live weight (DM basis). The factors were:

Source of supplementary forage:

CA: Cabbage;

CC: Chinese cabbage;

CL: Cauliflower;

WS: only water spinach

Supplementation with paddy rice:

WR: With paddy rice;

NR: Without paddy rice

Feeding system

Water spinach was hung in bunches above the feed trough and offered at a level of 100 g  (DM)/kg body weight. Leaves of cauliflower, cabbage and Chinese cabbage were offered ad libitum in troughs. Paddy rice was given in the feed trough at the rate of 50 g/day. Feed offered for each rabbit was weighed every morning and the animals were fed with 50% of their daily ration in the morning and 50% in the afternoon. Fresh water was freely available.  

Measurements

The experiment lasted for 8 weeks. The animals were weighed at the start of the experiment and then weekly, on the same day of the week and before feeding in the morning. Feeds offered and refusals were recorded and samples analysed for DM, crude protein (CP) and ash according to AOAC (1990).

Statistical analysis

The data of the experiment were subjected to  analysis of variance using the General Linear option of the ANOVA program in the Minitab Software Release version 13.1 (2000). Sources of variation were: forages, paddy rice, interaction forage*paddy rice and error.

Results and discussion

The DM contents of cabbage, cauliflower, chinese cabbage and water spinach were low, but their CP content was high (Table 1.)

Intakes of DM and crude protein, and rates of live weight gain,  were increased when leaves of cauliflower, cabbage or Chinese cabbage were offered in addition to the basal diet of water spinach (Tables 2 and 3; Figure 1). The supplement of paddy rice also supported higher DM intakes and live weight gains, even though CP intake was decreased.

Figure 1. Effect of a supplement of paddy rice on growth rates of rabbits fed water spinach alone (WS) or water spinach with leaves of Cabbage (CA+WS), Chinese cabbage (CC+WS) or Cauliflower (CF+WS)

There is no obvious explanation for the stimulating effect on feed intake and growth rate when the water spinach basal diet was supplemented with leaves of cauliflower, cabbage or Chinese cabbage, other than the access to a greater variety of feeds. The positive effect on DM intake and growth of the paddy rice supplement is even more difficult to explain.  A higher energy density does not seem to be the explanation as in several experiments with water spinach basal diets, there have been no responses to supplements of even higher energy density such as broken rice (see: Hongthong Phimmmasan et al 2004;  Pok Samkol et al 2006).  Leng (2006) considered that the rabbit was poorly adapted to digest starch in view of the short small intestine and the rapid transit time. By contrast, supplements rich in fibre have given positive results with rabbits fed diets based on water spinach (Khuc Thi Hue and Preston 2006; Doan Thi Gang et al 2006) thus there may have been some benefit in this respect from the fibrous husk of the paddy rice.

Conclusions

• Feed intakes and growth rates of rabbits fed a basal diet of water spinach were increased when they also had access to leaves of cauliflower, cabbage or Chinese cabbage.
  
  
• A supplement of paddy rice stimulated feed intake and growth rate on all the diets.

Acknowledgements

The authors are grateful for the support from the MEKARN project, financed by the Sida-SAREC agency. The authors would also like to thank the Department of Animal Husbandry and Veterinary, Faculty of Agriculture and Natural Resources of An Giang University for infrastructure support.

References

AOAC 1990 Official Methods of Analysis, 15th edition. Association of the Official Analytical Chemists. Washington D.C.

Chiv Phiny and Lampheuy Kaensombath 2006 Effect on feed intake and growth of depriving rabbits access to caecotrophes. Livestock Research for Rural Development. Volume 18, Article No. 34. http://www.lrrd.org/lrrd18/3/phin18034.htm

Doan Thi Gang, Khuc Thi Hue, Dinh Van Binh and Nguyen Thi Mui 2006 Effect of Guinea grass on feed intake, digestibility and growth performance of rabbits fed a molasses block and either water spinach (Ipomoea aquatica) or sweet potato (Ipomoea batatas L) vines. Workshop-seminar "Forages for Pigs and Rabbits" MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August,  2006. Article #23. http://www.mekarn.org/proprf/gang.htm

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Leng R A 2006 Digestion in the rabbit -a new look at the effects of their feeding and digestive strategies.  Workshop-seminar "Forages for Pigs and Rabbits" MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August,  2006. Article # 18. http://www.mekarn.org/proprf/leng.htm

Ly Thi Luyen 2003 Effect of the urea level on biomass production of water spinach (Ipomoea aquatica) grown in soil and in water; Retrieved, from MEKARN Mini-projects. http://www.mekarn.org/msc2003-05/miniprojects/webpage/luyen.htm

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Pok Samkol, Preston T R and Ly J 2006 Digestibility indices and N balance in growing rabbits fed a basal diet of water spinach (Ipomoea aquatica) supplemented with broken rice. Livestock Research for Rural Development. Volume 18, Article # 22. http://www.lrrd.org/lrrd18/2/samk18022.htm

Received 6 September 2009; Accepted 25 September 2009; Published 1 October 2009

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