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Live stock production, climate change and resource depletion |
An experiment was carried out to evaluate supplements of paddy rice or sweet potato root in basal diets of water spinach and cabbage leaves for growing rabbits on feed intake, growth performance. Twenty-four weaned crossbred rabbits (New Zealand x local female) 8 weeks of age were used. The design was a 2*3 factorial the factors being: (i) Water spinach (WS) or Cabbage (CAB); (ii) Supplements of Sweet potato root (SPR), paddy rice (PR) or no supplement (NS).
Paddy rice, and to a lesser extent sweet potato roots, improved growth date and feed conversion when the basal forage component of the diet was water spinach. There were no benefits from these supplements when the basal diet was cabbage. There were no apparent relationships between the protein, ash and cell wall constituents of the diets and growth performance.
In the Mekong delta of Vietnam, smallholder farmers keep rabbits (Oryctotagus cuniculus) for family consumption and as an income source. According to Nguyen Quang Suc et al (1996), rabbits can be fed by grasses and vegetables in farmers’ home gardens. Water spinach (Ipomoea aquatica) has high biomass yield (Kean Sophea and Preston 2001) and crude protein content above 20% in DM (Ly Thi Luyen 2003; Ho Bunyeth 2003). The foliage has been fed successfully as the only component of diets for growing rabbits (Hongthong Phimmasan et al 2004). Cabbage wastes from the markets are available all the year round and are a potential feed for rabbits (Tam et al 2009).
There are varying results for supplementation of water spinach with carbohydrate-rich supplements. Broken rice gave no benefit in experiments done by Pok Samkol et al. (2005). By contrast, supplementation with paddy rice increased growth rate in trials done by Tam et al. (2009). There are no reports of the use of root vegetables as supplements for forages in diets for rabbits. Sweet potato root is rich in both starch and sugar and would appear to be a logical supplement to balance the high protein content of water spinach.
The objective of this study was to evaluate supplements of paddy rice and sweet potato root in diets based on water spinach and cabbage leaves.
The study was done in the animal farm of Angiang University, Chauphu district, Longxuyen city, Vietnam with 24 weaned crossbred rabbits (New Zealand male x local female). The rabbits had an initial weight of 900 - 1100 g and were between 7 and 8 weeks of age.
The experiment was arranged as a 2*3 factorial in a completely 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:
Sweet potato root (SPR),
Paddy rice (PR), No supplement (NS)
Source of foliage:
Water
spinach (WS), Cabbage (C)
Water spinach was hung in bunches above the feed trough. Leaves of cabbage, sweet potato root and paddy rice were fed in troughs for rabbits to choose freely. Feed offered for each rabbit was weighed every morning and the animals were offered fresh feed three times a day at 8 a.m., 2 p.m. and 6 p.m. 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.
Feeds offered and refusals were analysed for DM, N and ash according to AOAC (1990).
The data from the experiment were subjected to analysis of variance using the General Linear Model (GLM) procedure of Minitab Software Release version 13.1 (2000). Sources of variation were: Forage source, supplement, interaction forage*supplement and error.
The DM content and the crude protein in the DM were lower in the cabbage leaves than in water spinach (Table 1). The mineral content was much higher in the foliages than in the carbohydrate supplements.
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Table 1: Chemical composition of the experimental feeds (g/kg) |
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Cabbage |
Water spinach |
Paddy rice |
Sweet potato root |
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DM |
68 |
95 |
823 |
239 |
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DM basis |
|
|
|
CP |
234 |
270 |
73 |
42 |
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Ash |
129 |
159 |
56 |
37 |
|
OM |
873 |
841 |
944 |
963 |
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NDF |
234 |
349 |
210 |
318 |
|
ADF |
220 |
262 |
125 |
77 |
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Table 1: Chemical composition of the experimental feeds (g/kg) |
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Item |
Cabbage |
Water spinach |
Paddy rice |
Sweet potato root |
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DM |
68 |
95 |
823 |
239 |
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|
|
DM basis |
|
|
|
CP |
234 |
270 |
73 |
42 |
|
Ash |
129 |
159 |
56 |
37 |
There was an interaction between forage source and the carbohydrate supplement on the growth rate of the rabbits (Table 2; Figures 1 and 2). When water spinach was the basal diet, supplementation with paddy rice increased growth rate by 75% compared with no supplement; while sweet potato root increased growth by some 25% compared with no supplement. On the cabbage basal diet there were no differences in growth rate among the three supplements. DM feed conversion was better for the diets based on water spinach than on cabbage. On the water spinach diets, the carbohydrate supplments tended to improve feed conversion. However, on the cabbage diets supplementation with carabohydrate resulted in poorer feed coinversion..
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Table 2. Mean values for change in live weight of rabbits fed basal diets od water spinach (WS) or cabbage leaves with supplements of sweet potato root, or paddy rice, or none |
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Cabbage |
Water spinach |
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NS |
PR |
SPR |
NS |
PR |
SPR |
SEM |
P |
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Live weight, g |
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Initial |
895 |
843 |
933 |
1050 |
908 |
993 |
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Final |
1778 |
1733 |
1778 |
1773 |
2073 |
1925 |
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|
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Daily gain |
15.0 |
15.2 |
13.7 |
12.7 |
21.1 |
16.1 |
1.2 |
0.011 |
| Feed intake, g/d | ||||||||
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DM |
66 |
94 |
72 |
50 |
64 |
48 |
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| NDF | 24.8a | 20.2b | 21.6b | 11.1d | 4.0e | 13.1c | 0.4 | |
| ADF | 17.0a | 12.1b | 8.7d | 10.0c | 1.6f | 6.4e | 0.3 | |
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DM conv. |
4.39 |
6.20 |
5.25 |
3.94 |
3.03 |
2.97 |
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CP in DM, % |
28.1 |
16.5 |
15.6 |
24.0 |
14.1 |
14.0 |
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abc Means in the same row without common letter are different at P<0.05 |
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| Figure 1. Effects on growth rate of the rabbits of supplementing basal diets of cabbage or water spinach with paddy rice or sweet potato roots | Figure 2. Effects on growth rate of the rabbits of source of forage in diets with different carbohydrate supplements |
The contrasting effects of carbohydrate supplementation on growth and feed conversion on the two basal diets of water spinach and cabbage are difficult to explain. Pok Samkol (2---) reported no benefits when broken rice was added to a basal diet of water spinach. By contrast, paddy rice had positive effects in a basal diet of water spinach in the research reported by Inthapanya and Preston (2009) and Tam et al (2009). Results of unpublished research in our laboratory (Bui Phan Thu Hang, unpublished data) indicated that the beneficial effects of the paddy rice in basal diet of water spinach appeared to be related to the 'bran" fraction, which is the component of the rice grain rich in lipids and B vitamins. The crude protein of the diets differed markedly with ranges from 14 to 16.5% in DM for the diets with carbohydrate supplement compared with 24 to 28% on the unsupplemented forage diets. There was also no apparent relationship between the cell wall components of the diet ingredients (NDF and ADF) and performance criteria.
Conclusions
Paddy rice, and to a lesser extent sweet potato roots, improved growth date and feed conversion when the basal forage component of the diet was water spinach.
There were no benefits from these supplements when the basal diet was cabbage.
There were no apparent relationships between the protein, ash and cell wall constituents of the diets and growth performance.
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.
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