Water spinach (Ipomoea aquatica)  as a low-cost feed resource
 for growing rabbits

Hongthong Phimmmasan

Xiengkhuang Province Agriculture and Forestry Office (PAFO),
 Laos
 hongthongp@yahoo.com

Abstract

Ten young rabbits averaging 416 g were allotted at random into five treatments consisting of rations based on fresh water spinach (Ipomoea aquatica) given at libitum and five levels of broken rice (0, 5, 10, 15 and 20 g/rabbit per day) to determine growth parameters and digestive indices during 30 days.

There was no significant effect of broken rice on growth performance of rabbits fed water spinach ad libitum. Although not significantly different from the other treatments, daily gains in weight of 22.1 and 22.7 g/day, were highest for animals fed 5 and 10 broken rice/day. There was no significant effect of broken rice on digestibility indices of rabbits fed water spinach ad libitum.

Water spinach as the only source of feed for growing rabbits appears to support acceptable growth rates of close to 20 g/day with a DM feed conversion of 2.7.  This simple feeding system may be attractive for small-holder farmers in the tropics, due to the possibility to raise rabbits with a local resource (water spinach) that is easy to grow and needs no processing.

Key words: Broken rice, digestibility, growth, rabbits, water spinach

Introduction

In most developing, tropical countries as Laos, Vietnam or Cambodia, farmers keep livestock like cows, buffaloes, pigs, fish and poultry for their main source of income. Small animals like chickens, ducks and rabbits are used for home consumption. However, productivity is low and there is a lack of feed resources, particularly in the dry season.

Some approaches to solve the main constraint of feed scarcity in general and protein sources in particular, have been directed toward the search of local feedstuffs. Rabbit husbandry is not an exception in this context, and there are some recent reports concerning the use of tropical foliage as source of protein for this specie (Akinfala et al 2003; Sarwatt et al 2003).

Water spinach (Ipomoea aquatica) is coming to play an important role for farmers  in rural areas, because it is easy to plant and has a very high yield of biomass, which is rich in protein. The crude protein content in the leaves and stems can be as high as 32 and 18 % in dry basis, respectively (Ly Thi Luyen 2003). Water spinach is widely used for human food, but at the same time this vegetable can be given to rabbits, pigs and poultry. For these reasons, it is considered that water spinach can be a low cost feed for rabbits at smallholder farmer level.

The objective of this communication is to report preliminary observations concerning the use of water spinach as the major ration constituent for growing rabbits, and to determine the effect of supplementing it with small amounts of broken rice as a readily digestible source of carbohydrate.

Materials and methods

Ten young rabbits averaging 416 g in live weight were allotted at random into five treatments consisting of rations based on fresh water spinach (Ipomoea aquatica) given at libitum and five levels of broken rice (0, 5, 10, 15 and 20 g/rabbit per day) to determine growth parameters and digestive indices during a 30 day trial.

The experiment was carried out from 2 to 31 August 2003 at the research station of the An Giang University. Average air temperature at the experimental area, ranged as follows: 6 am, 27.3 ± 1.55 ^oC, 12 am, 31.8 ± 2.92 ^oC, and 6 pm, 27.7 ± 2.37 ^oC.

Experimental design and treatments

The design was a randomized block with blocks being the replications (see Table1)

Feed characteristics

The broken rice used in the trial had a low content of ash and crude protein (Table 2). On the other hand, the leaves from the water spinach were rich in crude protein, nearly twice the value corresponding to the stems from this same plant. The leaves and stems from water spinach used in the experiment were the terminal branches and the crude protein (Nx6.25) ratio of leaves to stems in the dry material was 1.75:1.

Feeding and management of animals

The water spinach was bought from farmers in the neighborhood of the University. The broken rice was from the local market. The water spinach (leaves attached to stems) was hung in the cage, by tying the stem portion to a bamboo stick (Photo 1).

Photo 1: Hanging the water spinach from the roof of the cage

The foliage was offered to the animals at least two times a day beginning in the morning at 6:30 am. Observations, mainly at midday (12:00 m) and in the evening (5:30 pm), were done to ensure the permanent availability of water spinach. The broken rice was served to the animals in a small bowl every morning, when feed refusals from the previous day were recorded. The proportions of leaves and stems (fresh basis) in the water spinach were recorded daily in the feed offered and refused. The animals were weighed every five days during the trial.

Animal housing

The cages were made of bamboo strips and metal wire mesh (Photo 2), with an elevation from the floor of approximately 0.75 m. The dimensions of each cage were: width 25 cm, length 25 cm and height 25 cm.  Two batteries of five cages each were housed in an open shed at the University Campus.

Photo 2: One of the battery of 5 cages used to house the rabbits

 

Digestibility studies

Faeces were collected on days 10 to 15 to determine digestibility indices by the acid-insoluble ash technique (Van Keulen and Young 1977). Feed refusals were collected every day and kept frozen in plastic bags until analysis.  At the end of the collection  period, feed refusals and faeces were mixed thoroughly by hand and pooled, ground in a coffee grinder in the fresh state and, thereafter, representative samples were used for chemical analysis.

Chemical analyses

Chemical analyses of the diets and faeces were undertaken following the methods of AOAC (1990) for ash and N. The DM content was determined using the microwave method of Undersander et al (1993). pH (glass electrode) was measured on the fresh faeces, which were also analyzed for total short chain fatty acids (SCFA) by steam distillation in a Markham apparatus followed by titration of the distillate with NaOH 0.01 N. Water extractability was determined by the methods described by Ly and Preston (2001). Ash from feed and faeces was treated with HCl 2 N, then combusted again in a muffle furnace  for the estimation of acid insoluble ash, following the method of Van Keulen and Young (1977) as outlined by Ly et al (2002).

Digestibility indices were calculated by standard procedures using acid insoluble ash as inert marker.

Statistical analysis

The data were subjected to analysis of variance (Steel and Torrie 1980) using the General Linear Model (GLM) option of the MINITAB software (Release 13.31, 2000). Sources of variation were treatments and error.

Results and discussion

Feed intake

The rabbits offered the higher amounts of broken rice did not eat all that was offered  (Table 3), and this was especially evident (P<0.001) when broken rice was given at levels of 15 and 20 g/day per animal. Intake of water spinach was reduced at offer levels of broken rice above 5 g/day (Figure 1). The rabbits selected more of the leaves than the stems (Figure 2) but the proportion was not affected by the level of broken rice.  The total DM intake was reduced at the highest level of broken rice supplementation. Total crude protein intake was lower with broken rice offer levels of 15 and 20 g/day, compared with levels of 5 and 10 g/day (Table 3 and Figure 3).

 

Figure 1: DM intake of WS leaves, WS stems and broken rice according to levels of broken rice offered

Figure 2: Proportions of leaves and stems (DM basis) in the water spinach offered and consumed according
to offer level of supplementary broken rice

 

Figure 3: Quantities of crude protein consumed as leaves and stems of water spinach and as broken rice

Growth and feed conversion

Neither final weight (Table 5) nor mean daily gain (Figure 4) was significantly influenced by the inclusion of graded levels of broken rice in the offered feed. Feed conversion was similarly unaffected by supplementation. Values for both growth and feed conversion were at an acceptable level, and were superior to reported performance data for rabbits in Nigeria (9 to 11 g/day and 4.9 to 6.0 DM conversion; Akinfala et al 2003), Tanzania  (13 to 19 g/day and 3.8 to 4.2 DM conversion; Sarwatt et al 2003) and Vietnam (10.0 g/day and 7.0 DM conversion; Nguyen Quang Suc et al 1996; 16 to 22 g/day and 4.1 to 4.7 DM conversion; Dinh Van Binh et al 1991).

 

Figure 4. Growth rate of rabbits fed water spinach ad libitum and graded levels of broken rice

Digestibility studies

Increasing the level of broken rice in the diet appeared to result in a lower pH  (Table 6) and a significant increase in the concentration of SCFA in the faeces (Figure 4). The implication from these observations is that the SCFA must have arisen from fermentation of the starch in the broken rice.  On the other hand, none of the digestibility indices examined in the current study appeared to be affected by the level of broken rice consumed by the rabbits.

 

Figure 4: Relationship between intakes of supplementary broken rice and concentration
of short chain fatty acids in the faeces of rabbits fed ad libitum water spinach

Mortality

One rabbit on the 20 g/day broken rice level developed severe diarrhoea and died after 2 weeks on the experiment. The symptoms and observations of highest levels of SFCA in faeces on this diet suggest that the cause may have been undigested starch reaching the large intestine, providing a substrate for bacterial fermentation.

Conclusions

• Fresh water spinach as the only source of feed for growing rabbits appears to support acceptable growth rates of close to 20 g/day and an excellent feed conversion of 2.7 g  DM per g live weight gain.
• This simple feeding system may be attractive for small-holder farmers in the tropics, due to the possibility to raise rabbits with a local resource (water spinach) that is easy to grow and needs no processing.

Acknowledgments

First of all I would like to express my gratitude to the MEKARN program under the SIDA-SAREC Project for providing us an opportunity and budget to learn and conduct a mini-project, which helped me to understand more about steps in planning and conducting an experiment. Special thanks are given to Dr T R Preston and to Dr J Ly for their supervision and support. The mini-project activities were very well organized and provided valuable suggestions and comments. Thanks are also given to Mr Chay Ty and Mr San Thy, as facilitators for providing practical support and laboratory assistance. Without this support, I do not believe I would have been able to carry out this experiment.

References

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