Effect of offering leaves or stems of water spinach on patterns of eating, consumption of caecotrophes and excretion of faeces by growing rabbits

Pok Samkol, T R Preston* and R A Leng**

Center for Livestock and Agriculture Development, (CelAgrid-UTA Cambodia), Cambodia
samkolpok@yahoo.com
* UTA (Colombia), Socorro, Santander, Colombia
trpreston@mekarn.org
** PO Box 361, Coolum Beach, Qld 4561, Australia
rleng@ozemail.com.au

Abstract

Two experiments were done with crossbred rabbits (Local x New Zealand White) (range of live weight from 1600 to 1800 g), fed either stems or leaves of water spinach as sole diets. In the first study, observations were made of time spent eating, times spent consuming caecotrophes and voiding faeces. In the second experiment the effect on feed intake of depriving the rabbits of having access to the caecotrophes was monitored. The third experiment examined the composition of stomach contents of 2 rabbits on each diet slaughtered at 4 hour intervals over a 24 hour period.

The rabbits consumed  feed throughout the 24 hours. However, the consumption of caecotrophes was mainly during the day while faeces were voided only at night time. There were no differences between the two diets in the diurnal pattern of eating, consuming  caecotrophes or voiding of faeces. However, total DM intake was higher when leaves were fed compared with feeding only the stems. The composition of the stomach contents, which included the caecotrophes, mirrored those of the diet with higher protein and lower crude fiber contents when the diet was water spinach leaves compared with stems. There were marked diurnal trends in the composition of the stomach contents during the 24 hours for the rabbits fed water spinach stems, with maximum values at midnight for DM and crude protein and minimum values for crude fiber. These trends were less marked on the diet of water spinach leaves

It was concluded that feeding water spinach leaves rather than stems resulted in a lower production of caecotrophes. It is suggested that the lower level of caecotrophs consumed on the leaves only diet may have reduced overall supply of protein and B vitamins (from caecal  microbes). .Lower levels of caecal-produced nutrients of microbial origin  could  explain  the poorer growth performance of rabbits observed in earlier trials when high offer levels of the water spinach led to increased selection of leaves at the expense of the stems.

Key words: Caecotrophes, diurnal patters of behaviour, faeces, leaves, rabbits, stems, water spinach

Introduction

Water spinach (Ipomoea aquatica) is a valuable feed resource for rabbits, apparently providing adequate protein and energy and other essential  nutrients for growth. It also provides sufficient  water (Hongthong Phimmasan et al 2004; Pok Samkol et al 2006a). When used to replace grass in a diet, in which 50% of the DM came from concentrates, rates of growth and feed conversion of rabbits were improved by more than 25% (Tran Hoang Chat et al. 2005).  Pok Samkol et al (2006b) showed that  increasing the proportion of stem to leaf and thus the fiber content in a water spinach diet  improved  live weight gain and feed conversion. This was possibly mediated by stimulation of feed intake since DM intake was increased by 50% when rabbits had access to other sources of high-fiber feeds (grass and rice straw) in addition to water spinach (Pok Samkol, Unpublished data). The present experiment was aimed at investigating the interaction of dietary fiber and growth rate, through further study of  caecotrophes produced and the content of the stomach in rabbits given either high fiber "stem" or low fiber "leaves" of water spinach.

Hypotheses

It was hypothesized that:

• Offering the stems (high fiber) and leaves (low fiber) of water spinach as separate feeds will influence the composition of the caecotrophes and the pattern of recycling and thus help to explain the differences in growth rate of rabbits fed varying proportions of leaves and stems as the sole diet.

Materials and methods

Three experiments were conducted at the Center for Livestock and Agriculture Development (CelAgrid-UTA Cambodia) located in Pratheat village, Rolous commune, Kandal Stroeung district, Kandal province, Cambodia which is 26 km from Phnom Penh city.

Experiment 1: Observations of time spent eating and defecating of rabbits fed  either stems or leaves of water spinach

Experimental design and treatments

Four crossbred (Local x New Zealand White) rabbits with average live weight of 1625 ± 119 g were allocated to two treatments:

• WST: Stems of water spinach

• WSL: Leaves of water spinach

The design was a  randomized block arrangement with two replications of each treatment. The diets were fed ad libitum (about 120% of recorded intakes). The rabbits were housed in individual cages constructed from wood and wire mesh. The dimensions of the cages were: width 0.5 m, length 0.7 m and height 0.5 m.

Feeding and management

Water spinach was bought from traders near the lake of Cheung Ek, Phnom Penh City. The foliage was separated into stems and leaves and the proportions recorded.  The feeds were offered in a trough, three times per day in the morning at 7:00 am, at 12:00 and at 4:00 pm.  Water was not supplied as earlier observations (Miech Phalla, personal communication) indicated that rabbits were able to satisfy their needs for water from that contained in the water spinach which has about 90% of moisture.

Data collection

Feed intake was recorded from weights of fresh materials offered minus residue taken the next morning. Observations were started at 7:00 am by two people to record minutes spent eating, in consumption of caecotrophes and excretion of faeces.  Samples of feeds offered and refused were analysed for DM,

Experiment 2: Quantities of feed DM ingested, caecotrophes produced and faeces excreted by rabbits fed water spinach stems or leaves

Experimental design and treatments

Four crossbred (Local x New Zealand White) rabbits with average live weight of 1813 ± 136 g were allocated to the same treatments, housing and feeding method as in Experiment 1. Plastic collars were out around the necks (Photo 1) to prevent the rabbits consuming the caecotrophes. 

Data collection

Feed intake and production of caecotrophes and faeces were recorded every hour. Caecotrophes were not fed back to the rabbits. The measurements were started at 8:00 am by two people. Samples of feed offered and refused and of caecotrophes and faeces were taken for analysis of DM.

Statistical analysis

This was the same as in Experiment 1.

Experiment 3: Composition of stomach contents in rabbits fed leaves or stems of water spinach.

Experimental design and treatments

24 crossbred (Local x New Zealand White) rabbits with average live weight of 1811 ± 301 g were allocated to the same treatments as in Experiment 1. Housing and feeding arrangements were the same as in Experiment 1. 

Data collection

Feed intake was recorded from 7.00 am until the time of slaughter, which began at 12:00 am with 2 animals being slaughtered every 4 hours.  Samples of feed offered and refused, of caecotrophes and faeces and of stomach contents, were taken for analysis of  DM. N, ash and crude fiber.

Chemical and statistical analyses in the three experiments

Chemical analyses

Chemical analyses of samples for for ash, N, and crude fiber were by the methods proposed by AOAC (1990). DM content was determined using the micro-wave method of Undersander et al (1993).

Statistical analysis

The data were analysed using the GLM option of the Minitab (version 13.31, 2000) ANOVA software. The sources of variation were treatments and error.

Results and discussion

Chemical composition of feed

Water spinach leaves had higher contents of dry matter, crude protein and organic matter and much less crude fiber than the stems (Table 1).

Diurnal activities

Eating took place throughout the 24 hours (Figure 1), but intake of caecotrophes was mainly during the day (7.00 to 17.00 hours; Figure 2), while faeces were voided only at night (Figure 3). These observations are different to those of Lebas et al (1997) who reported that caecotrophes are  produced in the night time and the faeces during the day.  However, McNitt et al (1996) indicated that caecotrophes may also be produced by rabbits in the day time. Differences in environmental temperatures between temperate and tropical latitudes may have been the reason for the observed differences.

The pattern of DM intake expressed as quantities consumed (Figure 4) was similar to the observations for times spent eating (Figure 1), indicating that the rate of eating was more or less continuous during the 24-hour period of measurement. However, there were major differences in the pattern of production of caecotrophes (Figures 2 and 5), which were consistent for leaves and stems and took place during the day in rabbits used in experiment 1 but was irregular in rabbits used in experiment 2, with peaks of production during both day and night and no consistent pattern for the two diets. In experiment 2, the rabbits were fitted with plastic collars to prevent them consuming the caecotrophes, which  were not fed back to the rabbits. The pattern of production of faeces also differed between the two experiments, with similar quantities being produced during the night as during the day in experiment 2 (Figure 6), whereas, in experiment 1, faeces were produced only during the day (Figure 3).

Providing  rabbits with water spinach stems rather than leaves resulted in a slightly greater production of caecotrophes. However, as well as having more fiber, the stems also have less protein and  Cheeke (1994) indicated that the lower the crude protein concentration in the diet the greater is the consumption of the caecotrophes.

The amounts of caecotrophes produced on the water spinach diets in this study were similar to the results of Colin and Lebas (1995), lower than reported for Paprika meal and Olive leaves (Garcia et al 2000), but higher than for diets of  alfalfa hay, citrus pulp, beet pulp and rice hulls (Fragaet al 1990) (Figure 7).

Effect of diet and of access to caecotrophes on DM intake

There were no apparent differences between the two diets (leaves or stems of water spinach) in the diurnal pattern of eating, consumption pattern of caecotrophes or voiding of hard faeces by rabbits. However, total DM intake was higher when leaves were fed compared with feeding only the stems, in rabbits in both experiments 1 and 2 (Figure 8). Although not strictly comparable, as the observations relate to two separate experiments with different rabbits, there was a clear indication of lower DM intake when the rabbits were prevented from consuming the caecotrophes  (Experiment 2), which is contrary to the findings of Chiv Phiny and Lampheuy Kaensombath (2006) that DM intake was the same when rabbits fed water spinach had, or did not have, access to the caecotrophes. However, growth rates in the latter experiment  were considerably less for rabbits deprived of the caecotrophes.  It would appear that the physical disruption of the normal pattern of behaviour (by fitting the plastic collars) affected the physiological processes of digestion, even though the basal diet was highly digestible (80.5%; Pok Samkol et al 2006a). This result is similar to that reported by Irlbeck (2001) who also used a diet of high digestibility.

Composition of caecotrophes, faeces and stomach contents

The composition of the stomach contents, which included the caecotrophes, mirrored those of the diet with higher protein and lower crude fiber contents when the diet was water spinach leaves compared with stems (Table 2 and Figures 9, 10 and 11). The dry matter content of caecotrophes on the two diets was similar, but crude protein was higher and crude fiber lower for the diet of water spinach leaves (Table 2). The contents of dry matter and crude protein in the faeces was higher  for the diet of water spinach leaves than for stems.  The chemical composition of both caecotrophes and faeces was similar to the result of Chiv Phiny and Lampheuy Kaensombath (2006). Irlbeck (2001) indicated that as dietary fiber concentration increased the fiber composition of the faeces also increased.   

There were marked diurnal trends in the composition of the stomach contents during the 24 hours for the rabbits fed water spinach stems, with maximum values at midnight for DM and crude protein (Figures 9 and 10) and minimum values for crude fiber (Figure 11). These trends were less marked on the diet of water spinach leaves.

Stomach contents as percentage of live weight (DM basis) tended to be higher when the rabbits were fed water spinach stems compared with the leaves (Figure 12). The present finding was much lower than the 2.44% reported by Fraga et al (1990) for rabbits fed a diet in which the fiber was from alfalfa hay. The difference can probably be explained on the basis of the higher fiber content of the alfalfa hay compared with water spinach

Conclusions

• Feeding rabbits sole diets of water spinach leaves compared to only stems resulted in a lower production of caecotrophes.
   
• The enrichment of nutrients by microbial action in the caecum and their availability after consumption could be the explanation for the greater growth performance observed in earlier trials when restricted offer levels of the water spinach led to increased consumption of stems  relative to leaves. It can be speculated that under such conditions the caecal microbes were producing higher amounts of essential amino acids or growth factors such as B vitamins.

References