Growth performance of rabbits fed components of paddy rice as supplements to Operculina turpethum foliage or Operculina turpethum mixed with water spinach

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

Angiang University, Faculty of Agriculture and Natural Resources, Vietnam
bpthang@agu.edu.vn
* TOSOLY, AA #48 Socorro, Santander, Colombia

Abstract

Thirty- two weaned crossbred rabbits were used in a study to identify the components in paddy rice that supported best growth rates when fed as supplements to either Operculina turpethum alone or combined  with water spinach.    The design was a 2*4 factorial arrangement with 4 replications. The factors were: (i) Operculina turpethum (OT) alone or mixed 50:50 with water spinach (OW); (ii) components of paddy rice (paddy rice, rice grain+bran, rice grain+bran+husk, rice grain) at levels (g/day) of: 20, 14+2, 14+2+4 and 14, respectively. The study lasted 8 weeks.

When the rabbits had access to rice bran, as well as rice grain, growth rates were improved compared with rice grain fed as the only supplement, and were similar to the results with paddy rice. Growth rates were improved when water spinach replaced 50% of the Operculina foliage; however, the relative effects of the rice supplements were similar for both sources of foliage. These results indicate that it is the bran in the paddy rice that explains the better growth rate on paddy rice compared with rice grain. The fact that the rabbits did not eat the husk when it was offered as a separate feed, shows that it plays no positive role in a diet composed mainly of water spinach.

Key words: bran, fiber, grain, husk, intake

Introduction

Many studies have shown that rabbits can achieve acceptable levels of performance (ie: growth rates of 15 to 20 g/day) when fed diets composed exclusively of tropical forages. Most of these studies have been with water spinach (Ipomoea aquatica)  (eg: Hongthong Phimmasan et al 2004; Pok Samkol et al 2006; Tam et al 2009; Hang et al 2011, 2012) or sweet potato vines (Inthapanya and Preston 2009; Luyen and Preston 2012). Both these forages contain crude protein in proportions that exceed the growth requirements of rabbits. However, attempts to improve performance on these forages with supplements rich in digestible carbohydrates have only been consistently successful when paddy rice was the carbohydrate source (Inthapanya and Preston 2009; Tam et al 2009; Luyen and Preston 2012). Supplementing these foliages with broken rice grain almost never resulted in better performance (Hongthong Phimmasan et al 2004; Pok Samkol et al 2006).  As paddy rice is the source of rice grain for human consumption, it is important to determine which parts of paddy rice contribute most to the growth performance of rabbits.

The processing of paddy rice in the commercial rice mill produces, on average,  the following proportions (%) of end products: rice grain 70, rice bran 10 and rice husk 20.

The experiment we report in this paper was planned to determine which of these components of paddy rice had the greatest effect on rabbit growth rate. Opportunity was also taken to evaluate a source of high protein foliage not previously studied as the basal diet of rabbits, namely Operculina turpethum) (Photo 1). Operculina is a perennial herbaceous, hairy vine growing 4 to 5 m in length (http://en.wikipedia.org/wiki/Operculina_turpethum).  It has been reported to contain 16% crude protein in DM (Nguyen Kim Dong, personal communication).

Photo 1. Leaves and flowers of Operculina turpethum (from http://en.wikipedia.org/wiki/Operculina_turpethum)

Materials and Methods

Location

The experiment was done in the animal farm of Angiang University, Chauphu district, Longxuyen city, Vietnam.

Experimental design

The experiment was arranged as a 2*4 factorial in a complete randomized design with 4 replications. One rabbit housed in a wire mesh and wood cage, was the experimental unit. The experiment lasted for 8 weeks. The factors were:

Carbohydrate supplementation

·      Paddy rice (PR: 20 g/day), rice grain+bran (RGB: 14+2 g/day), rice grain+bran+husk (RGBH: 14+2+4 g/day) and rice grain (RG: 14 g/day).

Type of forage

·         Operculina turpethum or Operculina turpethum offered together with water spinach

Feeding and management

Operculina turpethum and water spinach were hung in bunches above the feed trough. The components of the paddy rice were fed in separate troughs. Feed offered for each rabbit was weighed every morning and the animals were offered fresh feed three times a day at 8 am, 2 pm and 6 pm.  The refusals and spillage were collected and weighed daily in the morning before feeding to calculate the feed intake. Fresh water was freely available. The animals were vaccinated to control hemorrhagic diarrhea.

Measurements

Feeds offered and refusals were analysed for DM, N and ash according to AOAC (1990). NDF and ADF were according to Van Soest and Robertson (1985).

Statistical analysis

The data from the experiment were subjected to analysis of variance using the General Linear Model (GLM) procedure of  the Minitab Software Release  (Minitab 2007). Sources of variation were: Forage source, supplement, interaction forage*supplement and error.

Results and Discussion

The DM content and cell wall fractions of Operculina turpethum forage were higher than for water spinach (Table 1). The  CP content of water spinach was nearly double that in Operculina turpethum.

Feed intake was lowest when only rice grain was fed (Table 2). .The rabbits did not eat the rice husk when it was offered separately from the grain and the bran.

When the rabbits had access to rice bran, as well as rice grain (treatments RGB and RGBH), growth rates were improved compared with rice grain fed as the only supplement, and were similar to the results with paddy rice (PR) (Table 3; Figure 1). Growth rates were improved when water spinach replaced 50% of the Operculina foliage (Figure 2); however, the relative effects of the rice supplements were similar for both sources of foliage. These results indicate that it is the bran in the paddy rice that explains the better growth rate on paddy rice compared with rice grain. The fact that the rabbits did not eat the husk when it was offered as a separate feed, shows that it plays no positive role in a diet composed mainly of water spinach.

Huyen et al (2013) carried out a similar experiment but reported no differences in rabbit growth rates between rice grain and paddy rice given as supplements to sweet potato vines.  There is no obvious explanation for these contrasting effects, other than possible differences in the relative balance of nutrients offered by sweet potato vines compared with water spinach or Operculina.

Figure 1. Main effects of different components of paddy rice (RG rice grain, RG+B rice grain and bran, RG+B+H rice grain+bran+husk, PR paddy rice) on growth rate of rabbits fed foliage of Operculina or Operculina with water spinach	Figure 2. Main effects  of source of forage on growth rate of rabbits supplemented with different components of paddy rice

Conclusions

• Rabbits fed Operculina foliage or Operculina and waster spinach grew faster when supplemented with paddy rice or rice grain plus rice bran, compared with rice grain.

• The advantages of paddy rice compared with rice grain as a supplement for growing rabbits fed water spinach or Operculina foliages thus appear to be associated with the bran fraction.

• Growth rates were improved by 19% when water spinach was combined with Operculina as compared with Operculina fed as the sole foliage.

Acknowledgements

The authors are very grateful to the Swedish International Development Agency, through the regional MEKARN Project, for the financial support of this study. 

References

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

Hang B P T, Lam V and Preston T R 2011 Effect of different sources of carbohydrate as supplements to basal diets of water spinach and cabbage leaves on the growth rate in rabbits. Livestock Research for Rural Development. Volume 23, Article #227. http://www.lrrd.org/lrrd23/11/hang23227.htm

Hang B P T, Lam V and Preston T R 2013 Effect of paddy rice on growth performance of rabbits fed water spinach as the sole forage or combined with leaves of water hyacinth. Livestock Research for Rural Development. Volume 25, Article #45. Retrieved , from http://www.lrrd.org/lrrd25/3/hang25045.htm  

Hongthong Phimmasan, Siton Kongvongsay, Chhay Ty and Preston,T R 2004 Water spinach (Ipomoea aquatica) and Stylo 184 (Stylosanthes guianensis CIAT 184) as basal diet for growing rabbits. Livestock Research for Rural Development. Vol. 16, Art. # 34. Retrieved from http://www.lrrd.org/lrrd16/5/hong16034.htm.

Huyen N T D, Trach N X and Preston T R 2012  Effects of supplementation of paddy rice and/or rice grain and/or rice husk to sweet potato (Ipomoea batatas) vines as basal diet on growth performance and diet digestibility in rabbits. Livestock Research for Rural Development. Volume 25, Article #19. http://www.lrrd.org/lrrd25/1/huye25019.htm

Inthapanya S and Preston T R 2009 Effect of supplementation with sweet potato root and paddy rice on growth performance of local rabbits fed water spinach (Ipomoea aquatic) and paper mulberry (Broussonetia papyrifera) as basal diets. Livestock Research for Rural Development. Volume 21, Article #176. http://www.lrrd.org/lrrd21/10/sang21176.htm

Luyen L T and Preston T R 2012 Growth performance of New Zealand White rabbits fed sweet potato (Ipomoea batatas) vines supplemented with paddy rice or Guinea grass supplemented with commercial concentrate. Livestock Research for Rural Development. Volume 24, Article #127. http://www.lrrd.org/lrrd24/7/luye24127.htm

Minitab 2007 Minitab Reference Manual, Release 15 for Windows. Minitab Inc, USA.

Pok Samkol, Preston T R and Ly J 2006  Effect of increasing offer level of water spinach (Ipomoea aquatica) on intake, growth and digestibility coefficients of rabbits. Livestock Research for Rural Development. Volume 18, Article No. 25. http://www.lrrd.org/lrrd18/2/samk18025.htm

Tam N H, Tuan V T, Lam V, Hang B P T and Preston T R 2009  Effects on growth of rabbits of supplementing a basal diet of water spinach (Ipomoea aquatica) with vegetable wastes and paddy rice. Livestock Research for Rural Development. Volume 21, Article #174. http://www.lrrd.org/lrrd21/10/hang21174.htm

Van Soest, P J and Robertson, J B 1985 Analysis of forages and fibre foods. Ithaca, New York: A Laboratory Manual for Animal Science 613 Department of Animal Science, Cornell University.

Received 1 July 2012; Accepted 11 February 2013; Published 1 March 2013

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