(1) Department of Animal Husbandry, College of
Agriculture, Cantho University
(2) Department of Animal Nutrition and Management,
Box 7024 Swedish University of Agricultural Sciences, S-750 07
Uppsala Sweden
Abstract
A total of 402 local breed chicks (Tau Vang) at 1 day of age
were allocated in a completely randomized design to 6 treatments,
with 3 levels of crude protein (CP): 18 (CP18), 20 (CP20) and 22%
(CP22) crude protein, with or without fresh duckweed (DW) (Lemna
minor) ad-libitum. Total daily dry matter (DM) intakes
were slightly higher on the CP20 and CP22 diets (12.0 g and 11.7g,
respectively) compared with the CP18 diet (11.1g) and when DW was
supplied (12.4 g compared to 11.5g), but between treatment
differences were not significant (P>0.05). CP from duckweed
decreased with increasing levels of protein in the diets and
supplied 14.2, 12.0 and 10.3 % of the total CP intake in the CP18,
CP20 and CP22 dietary treatments, respectively (P<0.05). Chicks
fed DW had somewhat higher weight gains (8.3 g/day) compared with
chicks fed the diets without DW (7.8 g/day) (P=0.09) and there were
no differences between diets with different CP levels. Wing and
tail feathers appeared first in chicks on the CP20 and CP22 diets
and tended to develop more rapidly on the diets with
duckweed.
Key words: local chicks, duckweed, dietary protein
content, daily gains.
1. Introduction
Poultry production is an essential element of agricultural
production throughout Vietnam, especially chicken production in the
Mekong River Delta, which accounts for 16% of the chicken meat and
28% of the total chicken products in the country. Feed supply is a
concern because it accounts for 60 - 70% of total production costs.
In particular protein is an important cost component in the diets
of chicks, and also has a major effect on the performance.
Therefore there have been many investigations into the use of
cheap, local protein feeds such as water plants, kitchen waste,
agro-industrial by products, etc., which reduce feed costs and thus
the price of the products and can increase the economic benefits to
the farmers. These alternative feeds, especially water plants,
should where possible meet the chick's nutrient requirements for
normal growth rate.
Duckweed protein has a better array of essential amino acids
than most vegetable proteins and more closely resembles animal
protein (Hillman and Culley, 1978). It is, therefore, a source of
high quality protein to be exploited for domestic animal production
(Haustein et al., 1987), in particular for pigs (Men, Le
Thi., 1997; Hang, Du Thanh, 1998) and chickens (Samnang,
1997) and has also been shown to be a good source of vitamins and
minerals for growing ducks (Becerra et al., 1997, Men et
al., 2001). Very little research has been done to determine the
protein requirements of local chicken breeds in Vietnam, such as
the Tau Vang, Ta and Ri chickens, even though many studies have
been carried out to determine the nutrient requirements of hybrid
and commercial breed chicks, especially for protein. Therefore,
this study was carried out to determine the optimum level of
dietary protein for starter local breed chicks, and also the effect
of supplementing duckweed for local chicks, and to determine the
economic benefit for small farmers. The objectives of this study
thus were:
2. Materials and methods
2.1. Location
The experiment was carried out in the experimental farm of Can
Tho University in South Vietnam, using local breed chicks from 1
day to 4 weeks of age.
A total of 402 local birds (Tau Vang) at 1 day of age were
allocated in a completely randomized design to 6 treatments with 3
replications (pens).
The chicks were given complete mixed diets ad-libitum
from 1day to 4 weeks of age that contained 3 levels of crude
protein (18, 20 and 22% CP), with or without fresh duckweed
supplied ad-libitum.
There were 18 pens of 1 m x 1 m built from local materials
(bamboo, thatch, etc.). The chicks were not sexed and were confined
in the pens, with 22 birds per pen. Light was used all the time
from electric bulbs. At this stage, the birds received the full
complement of routine vaccinations against Newcastle, Cholera,
Gumboro and Fowl pox diseases. The feed and duckweed were offered
in separate feeders, and drinking water was supplied ad
libitum. Duckweed was harvested every morning and supplied to
the chicks 2 times per day in the morning (08.00h) and in the
afternoon (14.00h). The bird's beaks were trimmed at eight days
using a hot blade debeaker.
The birds were weighed initially and then every week, with all
birds in the pen weighed together in a tared basket. Daily feed
intakes were calculated according to the total feed consumption of
the group in each pen. Feed and duckweed offered and refused were
recorded every morning. Daily live weight gains of chicks were
calculated on a weekly basis. Mortality was recorded by counting
the initial number of birds and number remaining at the end of each
week, and at the end of the trial. Appearance of wing and tail
feathers of chicks was recorded as the time when wing or tail
feathers had appeared in half of the chicks.
Representative samples of feed and duckweed and residues were
collected and stored in a refrigerator for determination of
proximate components by using standard AOAC methods (AOAC, 1994).
The DM content was determined by drying to constant weight at
105oC. Nitrogen was determined by the Kjeldahl technique
and CP as N x 6.25. EE was determined using anhydrous ethyl ether
in Soxhlet apparatus. Calcium and phosphorus were determined by
AOAC procedures (AOAC, 1994) (CAS-7440-70-2 for calcium and
CAS-7723-14-0 for phosphorus). These analyses were done at the
laboratories of Cantho University. Amino acids were analyzed by
using HPLC according to Spackman et al. (1994) at CASE
(Center of Analysis Service of Experiments) in HoChiMinh City.
Metabolizable energy (ME) content of the diets was calculated by
the formula
ME (Kcal/kg) = 4.26 X1 + 9.5 X2 + 4.23 X3 + 4.2
X4
(Nehring and Haenlein, 1973)
Where X1 through X4 are digestible protein, digestible fat,
digestible fiber and digestible nitrogen-free extract. Estimated
digestibility coefficients are according to NIAH (1992). The
ingredient and chemical composition of the experimental diets are
shown in Tables 1 and 2, respectively.
The data were analyzed by analysis of variance using the General
Linear Models procedure of Minitab version 13.31 (Minitab, 2000).
Comparisons between the various levels of protein, and the diets
with or without duckweed were tested. Crude protein level*duckweed
interactions were also tested and were found to be non-significant.
The temperature and humidity were recorded in the early morning and
at midday and were analyzed by descriptive statistics as mean,
ranges, minima, maxima and standard deviations.
3. Results
3.1. Effect of level of dietary
protein
3.1.1. Feed and nutrient intake
Feed and nutrient intakes are presented in Table 3. Concentrate
feed DM intakes were higher on the CP20 and CP22 diets (12.0 g and
11.7g) compared with the CP18 diet (11.1g) thus producing a net
rise in total feed intake even though there were no significant
differences for feed intake among treatments (P>0.05). However,
duckweed intake was higher in the CP18 and CP20 diets (0.79 and
0.78g, respectively) compared to the CP22 diet (0.70g) (P=0.09).
Therefore, the percent of the total crude protein intake which the
chicks got from duckweed, was significantly different (P<0.05)
between the CP18 and CP22 diets (14.2 and 10.3%, respectively).
There were no significant differences for lysine, methionine,
threonine, and metabolically energy intakes among treatments. The
ratio of calcium to phosphorus was higher (P=0.02) on the CP22 diet
(1.2%) than on the CP18 and CP20 treatments (1.0 %).
3.1.2. Daily live weight gains and feed
conversion
Final live weights and live weight gains are summarized in Table
4, and were lowest on the CP18 diet (251g and 7.9g, respectively),
and highest on the CP20 treatment (261g and 12g, respectively) but
there were no significant differences among treatments. DM feed
conversion, CP/gain and ME/gain were not significantly different
among treatments (P>0.05).
3.2. Effect of duckweed supplement
3.2.1. Feed and nutrient intake
The data in Table 3 show that even though the chicks consumed
only small amounts of duckweed (0.76g / day DM) there was still a
tendency towards higher total feed intakes (12.4g) than for the
diets without duckweed (11.5g). The intakes of amino acids such as
lysine and methionine, and also of calcium and phosphorus were
slightly lower in the treatments without the duckweed supplement
than in the diets with duckweed, but there were no significant
differences between the diets.
3.2.2. Daily weight gains and conversion
ratios
Mean daily weight gain on the diets with duckweed (8.3g) was
somewhat higher (P=0.09) compared with chicks fed the diets without
duckweed (7.8g). There were no differences between the diets, with
or without duckweed, in DM, ME or CP conversion ratios.
Rate of feathering and survival percentage of
chicks
Wing feathers first appeared on day 3 and tail feathers on day
18, and there was a tendency for the rate of feathering to be
faster on the higher protein diets (CP20 and CP22) and on the
treatments where duckweed was supplemented.
The highest mortality occurred for diet CP20 plus duckweed and
lowest in CP20, but the differences were not statistically
significant (P >0.05). Chicks on the CP20 DW diet had a high
mortality in the fourth week (in the 1st replication) as
a result of Gumboro disease.
Temperature and humidity
Temperature and humidity can have had an effect on chick
performance and are presented in Table 6. However, it is clear from
these data that the temperature was the highest at the same time as
the humidity was the lowest, and vice versa.
4. Discussion
Total feed and concentrate intakes of the dietary treatments
CP18, CP20 and CP22 with duckweed were somewhat higher than of the
diets without duckweed. This implies that duckweed could have
improved the birds' appetite or the overall palatability of the
diets. This result is similar to that of Men (2001), who reported
that ducks given a supplement of duckweed had higher concentrate as
well as total DM intakes. On the CP22 diet, the chicks still
consumed high (intake was lower than on the CP20 diet) amounts of
concentrate, even though they were probably supplied excess
nutrients. Chicks offered duckweed on the CP18 treatment consumed
more duckweed than on the CP20 and CP22 diets, which implies that
the CP18 diet could have been deficient in protein and one or more
essential amino acids, and therefore the chicks would have consumed
more feed in order to restore their intake of the essential amino
acids to an adequate level (Smith, 2001). Maximum growth was
achieved by chicks on the CP20 diets and it was observed the birds
on the CP22 diets showed signs of diarrhea and therefore, their
growth rate tended to decrease. Excessive nutrients, according to
Klasing (1998) and Kirchgessner (1978)(cited by Liem et al.,
2003), are above the bird's requirements, therefore resulting in
decreased absorption or increased catabolism or excretion.
Results for daily gain indicate that protein and essential amino
acid intakes on the CP20 plus duckweed and CP22 without duckweed
treatments met the chicks' requirements. This agrees with the study
of Man et al., (2001) who reported that 22%CP in the diets
of local chicks was optimum for growth rate. Duckweed had a
generally positive effect on daily gains, and even on the 22CP plus
duckweed treatment daily gains were somewhat higher than on the
corresponding CP diet without duckweed. A possible explanation for
this is that even though all diets contained a vitamin-premix,
vitamin A is often destroyed quite rapidly in hot and humid
conditions, so the treatments without duckweed could have been
deficient in vitamin A, which is essential for growth and
reproduction and would have been supplied by the duckweed, which is
rich in carotenoids (Landolt et al., 1987; and Solomons,
1996). Therefore, chicks fed the CP18 diet could have been
deficient not only in protein but also in vitamin A that resulted
in poorer growth and reduced weight gain. This could explain why
the chicks on the 18CP diet consumed more duckweed than on the
other diets and why birds on the 22 CP diet still ate quite large
amounts of duckweed. This result is in agreement with Haustein
et al. (1994) and Samnang (1999), who showed that the
intakes and growth rates of birds was improved when offered
duckweed.
Comparisons with previous studies carried out on the Tau Vang at
Cantho University, show that the chicks in this study had a mean
average body weight (257 g at 4 weeks of age) that was heavier than
previous generations. For example, Nguyen Hong Quang (1998) and
Nguyen Thi Dao (1999) showed that chicks weighed 238g and 240g at 4
weeks of age, respectively, when fed a 20%CP commercial diet. The
increase in mean live weight at 4 weeks could have been due to the
effects of selection of Tau Vang in the last few years, and
possibly also due to the positive effect of duckweed.
Duckweed is considered to be fresh mineral supplement, in
particular providing calcium (Landolt and Kandeler, 1987) and
phosphorus (Nguyen Duc Anh et al., 1997) therefore
increasing total mineral intakes in the diets with
duckweed.
Sulphur-amino acids play an important role for feather
development (Liem et al., 2003), and this could explain why
the rate of feathering was faster on the higher protein diets (CP22
and CP20) compared with the lower protein diet (CP18), and on the
treatments with duckweed, which is rich in methionine and cystine.
Also leucine and threonine, and minerals such as selenium (Landolt
and Kandeler, 1987) are found in duckweed and have positive effects
on feather development. According to Choct (2000) improved feather
cover might direct metabolic energy towards increasing body weight
gain instead of maintaining body temperature.
High temperature and humidity could have depressed the intakes
of chicks. Increasing ambient temperature is accompanied by reduced
feed intake (Leclercq et al., 1987) and also by reduced
growth rates (Smith, 2001) when temperatures are over
25oC. Therefore, with temperatures over 30oC
chicks feel uncomfortable and open their beaks, increasing
respiration, and reduce their feed intakes. However, according to
Minh (1998), the temperature and humidity suitable for normal local
chick growth is from 31- 35oC for the first 2 weeks and
23 - 25oC for the next 2 weeks, and with 60 - 70%
humidity (Long et al., 1995). Cowan and Michie (1978) showed
that the growth rate of chicks was not depressed at temperatures
between 26 - 31oC. In comparison the data in Table 7
thus show that the temperature and humidity were suitable for
normal chick growth, although some signs of heat stress could be
observed in the middle of the day. However, this probably did not
reduce overall feed intakes, as the chicks would have compensated
by eating at other times of the day and night.
Survivability did not differ significantly among the treatments,
and Rahman et al. (2002) reported that the dietary protein
level and feed intake had no effect on mortality.
5. Conclusions
From these results, it is concluded that:
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|
Table 1. Ingredient composition of the experimental diets (as
fed) |
|||
|
|
CP 18 |
CP 20 |
CP 22 |
|
Yellow maize |
27.0 |
25.0 |
23.0 |
|
Broken rice |
36.7 |
35.7 |
31.7 |
|
Rice bran |
7.0 |
7.0 |
7.0 |
|
Soya bean meal |
18.0 |
20.0 |
25.0 |
|
Fish meal |
8.0 |
9.0 |
10.0 |
|
Shell meal |
1.0 |
1.0 |
1.0 |
|
Bone meal |
2.0 |
2.0 |
2.0 |
|
Vitamin Premix |
0.3 |
0.3 |
0.3 |
|
Total |
100 |
100 |
100 |
|
Cost (VND/kg) |
3050 |
3230 |
3270 |
|
Table 2. Analyzed nutrient composition (% in DM) of the
experimental diets and duckweed (DW) |
||||
|
|
Diet |
|||
|
CP18 |
CP20 |
CP22 |
DW |
|
|
Dry matter |
90.0 |
90.6 |
90.7 |
6.2 |
|
Crude protein |
18.4 |
20.7 |
22.4 |
37.0 |
|
Amino acids |
|
|
|
|
|
Lysine |
0.7 |
0.8 |
0.8 |
1.6 |
|
Methionine |
0.3 |
0.3 |
0.3 |
1.0 |
|
Meth. + Cystine |
0.3 |
0.3 |
0.3 |
1.2 |
|
Threonine |
0.6 |
0.6 |
0.6 |
1.5 |
|
Crude fibre |
4.4 |
4.7 |
5.2 |
7.7 |
|
Ether extract |
6.1 |
6.5 |
6.8 |
6.7 |
|
Calcium |
0.9 |
0.9 |
1.2 |
1.3 |
|
Phosphorus |
0.9 |
0.9 |
0.9 |
1.8 |
|
ME, MJ/kg (Calculated) |
12.1 |
12.7 |
13.2 |
9.8 |
|
Table 3. Effect of level of dietary protein and duckweed on
daily feed and nutrient intakes of growing chicks |
|||||||||
|
Item |
CP level |
DW- |
DW+ |
SE |
P- value |
||||
|
|
18 |
20 |
22 |
|
|
CP |
DW |
CP |
DW |
|
level |
Level |
||||||||
|
Total DM feed intake,g |
11.5 |
12.3 |
12.1 |
11.5 |
12.4 |
0.96 |
0.78 |
0.81 |
0.45 |
|
Conc. intake, g |
11.1 |
12 |
11.7 |
11.5 |
11.6 |
0.93 |
0.76 |
0.73 |
- |
|
DW intake, g DM |
0.79 |
0.78 |
0.7 |
- |
0.76 |
- |
0.09 |
0.74 |
0.92 |
|
CP intake, g |
2.21 |
2.62 |
2.74 |
2.38 |
2.67 |
0.20 |
0.16 |
0.17 |
0.22 |
|
CP from DW, g |
0.29 |
0.28 |
0.25 |
- |
0.27 |
- |
0.03 |
0.72 |
0.00 |
|
% CP from DW |
14.2a |
12.0ab |
10.3b |
- |
12.16 |
- |
0.79 |
- |
0.04 |
|
Ether extract, g |
0.7 |
0.76 |
0.87 |
0.70 |
0.76 |
0.05 |
0.04 |
0.1 |
0.24 |
|
Phosphorous, g |
0.10 |
0.12 |
0.11 |
0.10 |
0.12 |
0.01 |
0.01 |
0.63 |
0.14 |
|
Calcium, g |
0.10 |
0.12 |
0.15 |
0.12 |
0.13 |
0.01 |
0.01 |
0.02 |
0.35 |
|
Lysine, g |
0.08 |
0.10 |
0.10 |
0.09 |
0.10 |
0.01 |
0.01 |
0.15 |
0.14 |
|
Methionine, g |
0.04 |
0.04 |
0.04 |
0.03 |
0.04 |
0.00 |
0.00 |
0.91 |
0.08 |
|
Threonine, g |
0.08 |
0.08 |
0.08 |
0.07 |
0.08 |
0.01 |
0.01 |
0.98 |
0.12 |
|
Ca:P |
1.0b |
1.0b |
1.2a |
1.10a |
1.06b |
0.00 |
0.00 |
0.00 |
0.00 |
|
ME, MJ |
0.13 |
0.14 |
0.14 |
0.13 |
0.14 |
0.01 |
0.01 |
0.81 |
0.51 |
a,b means in rows with
different superscript letters are significantly different
(P<0.05)
|
Table 4. Effect of level of dietary protein and duckweed on
daily weight gains and feed conversion ratio |
|||||||||
|
Item |
CP level |
DW- |
DW+ |
SE |
P- value |
||||
|
|
18 |
20 |
22 |
|
|
CP level |
DW |
CP level |
DW |
|
Live weight,g |
|
|
|
|
|
|
|
|
|
|
Initial |
32.8 |
31.8 |
31.4 |
32.1 |
31.9 |
0.54 |
0.44 |
0.18 |
0.81 |
|
Final |
251 |
261 |
257 |
251 |
262 |
5.99 |
4.89 |
0.49 |
0.12 |
|
ADG,g |
7.9 |
8.3 |
8.1 |
7.8 |
8.3 |
0.23 |
0.18 |
0.46 |
0.09 |
|
FCR, kgDM/kg gain |
1.51 |
1.56 |
1.53 |
1.51 |
1.55 |
0.10 |
0.08 |
0.93 |
0.73 |
|
CP/gain, g/ g |
0.28 |
0.32 |
0.34 |
0.3 |
0.32 |
0.02 |
0.02 |
0.22 |
0.55 |
|
ME/gain,MJ/g * |
16.84 |
17.45 |
17.36 |
17.23 |
17.2 |
1.31 |
1.07 |
0.94 |
0.98 |
*Note: these figures are MJ/ kg. Divide by 1,000 for
MJ/g
|
Table 5. Effect of level of protein and duckweed supplement on
feather growth |
||||||||
|
Days |
CP18 |
CP18DW |
CP20 |
CP20DW |
CP22 |
CP22DW |
SE |
P |
|
Appearance of first: |
|
|
|
|
|
|
|
|
|
Wing feather |
3.0 |
2.0 |
2.7 |
2.3 |
2.0 |
2.0 |
0.2 |
0.06 |
|
Tail feather |
18.7 |
17.3 |
17.3 |
16.3 |
16.3 |
17.3 |
1.0 |
0.47 |
|
Table 6. Chick mortality during the experiment |
||||||
|
Week of age |
CP18 |
CP18DW |
CP20 |
CP20DW |
CP22 |
CP22DW |
|
No. dead |
No. dead |
No. dead |
No. dead |
No. dead |
No. dead |
|
|
1 |
- |
- |
- |
- |
- |
- |
|
2 |
- |
- |
- |
- |
- |
- |
|
3 |
- |
1 |
1 |
1 |
- |
- |
|
4 |
3 |
3 |
2 |
3 |
1 |
3 |
|
Total |
3 |
4 |
3 |
4 |
1 |
3 |
Table 7. Mean, minimum and maximum humidity and
temperatures
|
Item |
Mean, *06:00h |
Mean, 13:00h |
|
Temperature, oC |
25.5 ± 0.3 |
31.0 ± 0.3 |
|
Humidity, % |
65.3* ± 0.5 |
49.3 ± 0.7 |
* This is maximum for humidity