J. Sci. Dev. 2011, 9 (Eng.Iss. 1): 21 - 27 HANOI UNIVERSITY OF AGRICULTURE
EFFECTS OF GRADED LEVELS OF PADDY RICE SUPPLEMENTED TO WATER SPINACH
(
Ipomoea aquatica
) OR SWEET POTATO (
Ipomoea batatas
) VINES AS BASAL
DIETS ON FEED UTILIZATION AND GROWTH OF NEW ZEALAND WHITE RABBITS
Ảnh hưởng của mức bổ sung thóc vào khẩu phần cơ sở là rau muống (Ipomoea
aquatica) hay rau lang (Ipomoea batatas) đến hiệu quả sử dụng thức ăn
và sinh trưởng của thỏ trắng New Zealand
Nguyen Thi Duong Huyen
1
, Nguyen Hung Son
2
, Nguyen Van Dat
3
, Nguyen Xuan Trach
1

1
Hanoi University of Agriculture
2
National Institute of Animal Sciences
3
Vinh Phuc College of Economics and Technology
Correspoding author email:

Received date: 14.02.2011 Accepted date: 10.04.2011
TÓM TẮT
Một thí nghiệm được tiến hành nhằm đánh giá ảnh hưởng của mức bổ sung thóc vào khẩu phần

21
Effects of graded levels of paddy rice supplemented to water spinach (Ipomoea aquatica)
1. INTRODUCTION
Rabbits can efficiently utilize fibrous feed by
courtesy of their feeding and digestive strategies.
Among other forages, water spinach (Ipomoea
aquatica) and sweet potato (Ipomoea batatas) vines
are protein-rich vegetables (Ly Thi Luyen, 2003;
Hong, 2003), which have been commonly used as a
valuable basal diet for rabbits (Nguyen Thi Kim
Dong et al., 2006a,b), Pok Samkol et al., 2006a,b,c)
and Doan Thi Giang et al., 2006). To improve the
nutritional balance in diets based on such protein-
rich vegetables, different supplements rich in
digestible carbohydrates or fiber, or both, have
been carried out (Hongthong Phimmmasan et al.,
2004; Khuc Thi Hue and Preston, 2006; Doan Thi
Giang et al., 2006; Nguyen Huu Tam et al., 2008);
However, results obtained from those studies have
been questionable. Paddy rice seems to be an
appropriate supplement to protein-rich vegetables
fed as the basal diet for fast growing rabbits owing
to its high energy and fiber contents. The present
study was aimed to test responses of fast growing
rabbits in terms of feed intake, digestibility and
growth rate to graded levels of paddy rice
supplemented to water spinach or sweet potato
vines fed as a basal diet.
2. MATERIALS AND METHODS
A 5 x 2 factorial experiment was conducted to

gain (ADG) as the slope of the linear regression of
live weight on time. Total feed and feces
collections were made over 7 consecutive days in
the middle of the experiment. The feeds offered and
refusals were collected and weighed daily in the
morning. Representative samples of feces (10%)
were collected daily from the total feces collected
and stored at -25°C. At the end of the 7 days, the
samples were bulked according to individual
animals. Feed samples were taken over the same
period.
Feed and feces samples were analyzed for DM
according to AOAC (1990). Daily feed intake was
calculated as g DM/head/day and as percentage of
live weight. Feed conversion ratio (FCR) was
calculated as a ratio of DM intake/live weight gain.
Apparent total tract DM digestibility was computed
as DM digestibility (%) = (A-B/A)*100, where A
and B are total DM intake and total DM in feces,
respectively.
Data were subjected to analyses of variance
(ANOVA) for a 5x2 factorial model with
interactions, using the General Linear Model
(GLM) of Minitab 16 (2010). Pair-wise
comparisons of means were done using the Tukey
method. Regression analyses were made using
Microsoft Excel (2007).
3. RESULTS AND DISCUSSION
Table 1 shows relationships between levels of
paddy rice supplementation and feed intake in

b
99.90
a
5.61
a
2 52.14
c
2.93
c
98.59
a
5.53
a
3 32.64
d
1.81
d
96.31
a
5.33
a
4 31.75
d
1.70
d
104.51
a
5.60
a
SEM 3.08 0.18 3.47

supplementation and feed intake in rabbits fed a
basal diet of water spinach vinesFigure 3. Effect of actual paddy rice intake on
forage intake and total feed intake in rabbits fed
a basal diet of sweet potato vines

Figure 4. Effect of actual paddy rice intake on
forage intake and total feed intake in rabbits fed a
basal diet of water spinach vines

23
Effects of graded levels of paddy rice supplemented to water spinach (Ipomoea aquatica)
As can be seen in Figures 1 and 2, the more
paddy rice was supplemented, the more it was
consumed; however, at the same time, intake of the
basal diet was reduced accordingly. The responses
followed nonlinear curves with high determination
coefficients (R²). As a result, the total feed intake
remained almost unaffected (Figures 3 and 4).
Figures 3 and 4 also show strong relationships
between actual paddy rice intake, as a result of
level of supplementation, on intake of the basal diet
of sweet potato vines (R² = 0.971) or water spinach
vines (R² = 0.981). However, paddy rice intake
explained not much variation in total feed intake
whether the basal diet was sweet potato vines (R² =
0.296) or water spinach vines (R² = 0.076). That
was because there was a substitution rate (the

supplementation with highly digestible
carbohydrate (high energy density) in the form of
broken rice was not successful. So, the positive
effect found in the present study might be due to
the fibrous husk of paddy, as in other experiments
(Khuc Thi Hue and Preston, 2006; Doan Thi Giang
et al., 2006), supplements rich in fibre gave positive
results with rabbits fed diets based on water
spinach. It might also be due to combined effects of
both fibre (from the husk) and starch of paddy rice
supplemented to diets based on protein-rich
vegetables. The results of this study confirmed the
results from the experiment by Nguyen Huu Tam et
al. (2008) that rabbits fed on water spinach had
higher feed intake and live weight gain when they
were supplemented with paddy rice.
From tables 2 and 3, it can also be seen that
the rabbits had higher ADGs for the first 5 weeks
compared to those calculated for the whole 10
weeks of experiment. It was definitely due to the
unfavorable changes in the weather conditions. It
was getting hotter and wetter, and, as a result, the
ADG was becoming lower and lower toward the
end of the experiment. It might be too hot for the
exotic rabbits during the last weeks of the
experiment.
To find the mechanism behind the positive
effect of paddy rice supplementation on live weight
gain of rabbits fed a basal diet of protein-rich
vegetables, improvement in digestibility might have

Average daily gain (g/head/day)

First 5 weeks Total 10 weeks
Level of paddy rice supplementation (% LW)
0 21.79
b
14.15
c
1 22.24
b
15.35
bc
2 25.61
ab
17.26
ab
3 27.31
a
17.94
a
4 28.58
a
18.37
a
SEM 1.07 0.56
P <0.001 <0.001
Type of forage
Sweet potato vines 25.39
a
16.60

ab
Sweet potato vines
4 28.94
b
19.36
a
0 20.70
a
14.82
bcd
1 22.19
ab
16.25
abcd
2 25.17
ab
16.77
abcd
3 27.82
ab
17.48
abc
Water spinach
4 28.22
b
17.39
abc
SEM

1.51 0.79

abc
3 75.02
c
3.55
c
4 75.83
bc
3.73
bc
SEM 1.24 0.19
P <0.01 <0.01
Type of forage
Sweet potato vines 77.32
a
4.24
a
Water spinach 78.55
a
3.78
b
SEM 0.79 0.12
P >0.05 <0.05
N.B.: Means that do not share a letter are significantly different.

Figure 7. Relationship between proportion of
paddy rice in the diet and DM digestibility in
rabbits fed a basal diet of sweet potato vines
Figure 8. Relationship between proportion of paddy
rice in the diet and DM digestibility in rabbits fed a
basal diet of water spinach vines

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