Abstract
Eighty local (Tau Vang) laying hens at 19 weeks of age were
allocated to 5 dietary treatments and 3 replicates. The control
diet was a mixture of broken rice and soybean meal (SB100) with no
duckweed supplied. For the other four diets duckweed was available
ad libitum, giving 5 treatments, with soybean meal at levels
of 0, 25, 50, 75 and 100% (SB0DW, SB25 DW, SB50DW, SB75DW and SB100
respectively). Total feed consumption, and concentrate intake were
not significantly different among treatments (P>0.05). Duckweed
intake on the SB0DW (5.2 g) was significantly higher than of the
hens in the SB25DW, SB75DW and SB50DW treatments (3.6, 2.6 and 2.3
g, respectively). The proportion of the total crude protein intake
from duckweed was highest on the SB0DW diet (28.67% CP) and
decreased on the SB25DW, SB50DW diets, which were higher than on
the SB75DW diet (P<0.05). There were no significant differences
in daily CP and ME intakes and feed conversion ratio (P>0.05)
among treatments. Age at first egg was not significantly different
among treatments, although it was somewhat longer on the SB100 diet
compared to other treatments (P>0.05). There were no significant
differences among treatments for egg production, egg weight,
fertility, hatchability or egg quality parameters (P>0.05).
However yolk pigmentation was significantly better (P<0.05) for
all treatments with duckweed compared to the control
diet
Key words:Laying hens, duckweed, egg production, yolk
pigmentation
1. Introduction
Duckweed is a tiny water plant that grows very well on sewage
ponds all year round in the Mekong Delta. The nutritive value of
duckweed, which contains 40% crude protein, compares well to
soybean as a source of plant protein. More recently it has been
shown that duckweed can replace conventional protein in egg laying
bird diets up to 25% of total dry matter (Leng, 1999). In earlier
studies (Paper II) duckweed was provided ad-libitum for
growing Tau Vang chickens on diets where broken rice, successively
replaced up to 75% soybean meal without reduction in growth
performance. Therefore, the objectives of the experiment
were:
2. Materials and methods
2.1. Experimental design
Eighty local (Tau Vang) laying hens at 19 weeks of age were
allocated to 5 dietary treatments and 3 replicates. The hens were
selected on the basis of growth rate and appearance from the
remaining chickens used in a previous growth trial (Paper II), and
continued on the same treatment as in the growth trial. The dietary
treatments were:
SB100: broken rice + soybean meal (100%) mixed diet,
ad-libitum with no duckweed (control)
SB75DW: broken rice + soybean meal (75% of SB100) mixed
diet offered ad-libitum plus fresh duckweed
ad-libitum
SB50DW: broken rice + soybean meal (50% of SB100) mixed
diet offered ad-libitum plus duckweed
ad-libitum
SB25DW: broken rice + soybean meal (25% of SB100) mixed
diet offered ad-libitum plus duckweed
ad-libitum
SB0DW: broken rice + no soybean meal (0%) offered
ad-libitum plus duckweed ad-libitum
A vitamin - mineral premix was included in all diets. The
control diet contained broken rice and soybean meal with 16 % crude
protein. Lysine and methionine were added to the diet to meet
recommended requirements (NRC, 1994).
2.2. Feeding and management
The laying hens were confined in pens with 5 or 6 hens and one
cockerel. The amount of diet offered was estimated according to the
consumption level, which was daily about 10% in dry matter of body
weight. Feed was weighed daily in the morning. Feed residues were
taken every morning and afternoon before feeding. The dried samples
were bulked at weekly intervals and analyzed. The duckweed was
grown on ponds fertilized with effluent from biodigesters on the
experimental pig farm of Cantho University and harvested every day
during the experimental period. The fresh duckweed was offered
ad-libitum in separate feeders and given 2 times per day. The feed
was given with increased frequency according to the increased
production of the birds to ensure there was minimum wastage of
duckweed. The refusals were collected and weighed every morning and
afternoon before feeding to calculate the actual feed and duckweed
intakes. As there were considerable differences between treatments
in age at first egg, data were collected and analyzed for eight
weeks after the first egg for each treatment.
Parameters recorded:
Feed and duckweed intake
Egg number and egg weight
Quality of eggs and yolk pigment
Proportion of fertile eggs and hatchability of eggs*
*Egg weighing 38 g laid from around 25 days after first egg and
onwards were collected and tested for fertility (by candling) and
hatchability.
2.3. Analytical procedures and
calculations
Samples of feed and duckweed were analyzed for CP, DM, EE and CF
using standard AOAC methods (AOAC, 1994) at the laboratories of
Cantho University, and amino acids were analyzed by using HPLC
(High-performance liquid chromatography) according to Spackman
et al. (1958) at the Center of Analysis Service Experiment
(CASE), Ho Chi Minh City.
Egg weight: eggs were collected daily and the number laid was
recorded for the entire replicate group throughout the experimental
period. Eggs laid during 7 days were kept together and weighed on a
replicate basis. Average hen production was calculated from the
total number of eggs actually collected divided by the total number
of hens present in each group at the end of each week. The records
of feed consumption were thus for each week for each
replicate.
Shell thickness was measured using a micrometer and albumen
height was measured using a micrometer, taken halfway between its
outer edge and the outer edge of the yolk.
|
Albumin Index = |
Albumen height |
|
Average short and long diameter of albumen |
|
Yolk Index = |
Yolk height |
|
Yolk width |
|
Egg shape = |
|
|
|
Length of egg |
(Bao, 1978; Smith, 2001)
Yolk pigmentation was measured by using the Roche color pan with
1- 14 color score. Yolks numbered 1 - 6 are light yellow, 7 - 10,
medium yellow and from 11 to 14 are dark yellow.
2.4. Statistical analysis
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 soybean meal in diets
were tested. Pairwise comparisons between treatment means were made
using Tukey's procedure.
3. Results
3.1. Feed and nutrient intakes
The data in Table 3 show that total feed consumption and
concentrate intakes were not significantly different among
treatments (P>0.05). However, daily duckweed DM intake on the
SB0DW diet (5.2 g) was significantly higher than of the hens in the
SB25DW, SB75DW and SB50DW treatments (3.6, 2.6 and 2.3 g,
respectively). Daily CP intake from concentrate feed decreased as
the soybean meal in the diet was decreased, and consequently CP as
proportion of DM intake decreased significantly from 16.8% on the
SB100 diet to 12.5% on the SB0DW diet (P<0.05). The proportion
of the total crude protein intake from duckweed was highest on the
SB0DW diet (28.7% CP) and decreased on the SB25DW, and SB50DW
diets, which were higher than on the SB75DW diet (P<0.05). There
were no significant differences in daily CP and ME intakes and feed
conversion ratio (P>0.05) among treatments.
3.2. Reproductive performance
The reproductive performances of hens for the 8 weeks of the
experiment are shown in Table 4 and 5. Age at first egg was not
significantly different among treatments, although it was somewhat
longer on the SB100 diet compared to the other treatments
(P>0.05). There were no significant differences among treatments
for egg production (P>0.05), but the total for the period of the
experiment was highest for the SB25DW and SB0DW treatments (16
eggs/hen). The differences for mean egg weight and percent of eggs
> 38 g were not significant among treatments (P>0.05). The
average laying rate, fertile egg rate and the hatchability did not
differ significantly among treatments (P>0.05). However, a
numerically lower number of eggs, fertile eggs and hatched eggs
were produced in the SB100 diet than on the other
treatments.
3.3. Egg quality
The differences among treatments were significant for yolk
pigmentation (P<0.05) and the darkest yellow yolks were found on
the SB0 and SB25 treatments (12.2) and pigment color was
significantly darker for the hens fed duckweed compared to the
control treatment (5.5). Albumen index, yolk index and shell
thickness were not significantly different among treatments
(P>0.05). However, the yolk index of eggs from hens on the SB100
diet was lower (0.38) than the recommended standard (0.4) (Bao,
1978).
3.4. Economic analysis
A summary of the economic effects of the different levels of
soybean meal is presented in Table 7. The SB50DW diet had the
lowest cost (5,640 VND/kg) compared to the other treatments.
However, the highest profit was on the SB25 diet (27,553 VND) and
the lowest benefit was on the SB100 diet (2,390 VND). This was
followed by the diet in which broken rice and duckweed completely
replaced 75% of the soybean meal.
4. Discussion
The duckweed was of good quality, with a crude protein content
of 37.3%, probably because the ponds on which it was grown were
fertilized with pig effluent. However the DM content was only 4.7%,
and the high moisture content of duckweed (95 %) has been reported
as the major significant limitation of including it at high levels
in the diets of chickens (Haustein et al., 1988). However,
duckweed is very palatable and can stimulate appetite, and the hens
in the SB0DW treatment consumed more total feed DM, more of the
concentrate and more duckweed than for the other treatments,
possibly in an attempt to meet their requirement for protein (Leng,
1992). Besides, mean intake per hen will also be influenced by
mortality within the pen as the effect of the cockerel will be
greater. The intake of duckweed thus increased as the soybean meal
in the diets was reduced and Becerra (1994) and Men (2001) reported
similar findings for ducks. The amount of duckweed in the total
diet thus increased the total protein intake. According to Kakuk
(1988, cited by Liem et al., 2003), the daily protein
requirement intake to satisfy hens' reproduction is 5.6 g CP (this
applies to hens with a body weight of 1.6 kg).
Besides, on the duckweed treatments vitamin deficiency was
probably not a problem, as Klasing (1998) reported that higher
amounts of vitamins (A, D, E) would be absorbed and digested in
diets based largely on green plant sources (Solomons, 1996), such
as duckweed compared to "artificial" feeds. These vitamins are
needed for growth and egg production (NRC, 1994).
Mean age of the Tau Vang hens at first egg was highest on the
SB100 diet. This could be related to the poor performance in the
previous experiment (Paper II). Studies by Milby et al.,
(1953), and Leeson et al., (1979, 1987a) have indicated that
early growth depression often depresses mature body weight and
thereby adversely affects adult performance and maturity. However,
according to Minh (1998), age at first egg for local hens in
Vietnam was from 160 to 165 days, which is similar to the mean age
in our experiment, although the variation was considerable, ranging
from 144 days for the SB25DW hens to 191 days for the SB100 hens.
Egg production showed a close relationship with the hens' maturity
(at first egg), and data in Table 4 show that the age at first egg
was lowest on the SB25DW diet, and also the highest egg production,
and this agrees with Liem et al. (2003). The high egg
production on the SB0DW diet was confirmed by Haustein et
al. (1987) reported that older hens produce significantly
better than do younger hens when fed diets containing high levels
of duckweed. Replacing 75% of soybean meal by broken rice and
duckweed not only gave higher egg production, but also the laying
rate, fertile egg rate and hatchability were higher. In a previous
study from Cantho University (Minh, 1998) egg production, fertile
egg rate and hatchability were higher than the results of our
experiment that could have been affected by Marek's disease
occurring during the experiment. The ratio between hens and
cockerel in this experiment (5:1) was lower than the recommendation
(12:1) of Minh (1998), so this would not have been a problem.
Egg quality is important in a discerning market (Smith, 2001).
The result in Table 6 shown that the differences in shell thickness
were not significant among treatments. However, the mean shell
thickness on all treatments was higher than the recommendation for
local chickens of Bao (1978) of 0.32 mm, which suggests that
duckweed had no negative effect on the calcium absorption of hens.
Egg shape is also important and the standard index is 75% (Smith,
2001). The results in Table 6 show that eggs of the hens on the
SB25DW, SB75DW and SB100 diets met this standard. Yolk color is
also of concern to the customer and is greatly influenced by diet
(Smith, 2001; George, 1989). In this study, the diets with a
duckweed supplement resulted in eggs with a dark yellow color due
to the high carotene content of duckweed (1,025 mg/kg of DM, Men et
al., 2001; Haustein et al., 1987) which was not the case for
eggs from hens on the SB100 diet, which were rather pale in color.
The yolk index on the diets with DW reached the standard value of
0.4 (Bao, 1978), except for the value for treatment SB100, which
was slightly below the minimum standard. This could be caused by
vitamin A or xanthophyll deficiency (George, 1989). Albumin
quality was slightly below the standard for all treatments except
for SB0DW and this could be related to the high temperature (mean
maximum of 31oC), as George (1989) reported that high
temperatures reduced albumin index. The second possible reason,
which related to the time of lay, because most of the hens were in
the first phase of egg production.
The highest economic benefit on the SB25DW diet was a result of
the high rate of production and high efficiency of conversion when
compared to the other treatments.
5. Conclusion
From these results, it is concluded that egg production, egg
quality, feed conversion and net profit were highest when broken
rice replaced 75% of the soybean meal in the diet and duckweed was
supplied ad-libitum. However, even at 100% of soybean meal
replacement the egg production and profitability were also improved
compared to the control diet.
References
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Analytical
Chemists, Washington, D.C.
Becerra, M. 1994. Evaluation of feeding systems for growing
ducks based on
aquatic plants and sugar cane juice. MSc thesis. Department of
Animal
Nutrition and Management, Swedish University of Agricultural
Sciences.
Uppsala, Sweden. Paper II 1-8.
Bui Xuan Men. 2001. Use of Duckweed as a protein supplement for
growing
ducks. Doctoral thesis. Swedish University of Agricultural
Sciences.
Duong Thanh Liem, Bui Huy Nhu Phuc, Duong Duy Dong, 2003. Feed
and
Animal Nutrient requirements. Agriculture Publishing House.
Department of
Animal Husbandry. University of Agriculture and
Forestry.
George, J.M. 1989. Poultry products technology. Second edition.
Food Products
Press, Inc. Library of Congress cataloging in Publication
Data.
Haustein, A.T., Gilman, R.H., Skilicorn, P.W., Ventura, G. 1987.
Safety and
efficacyof sewage grown Lemna as a protein source for chickens.
6340
Sunny Spring, Columbia, Maryland 21044.
Haustein, A.T., Gilman, R.H., Skilicorn, P.W., Verara, V.,
Guevara, V.,
Gastanaduy, A. 1990. Duckweed, a useful strategy for feeding
chickens:
performance of layers. Poultry Science 69,
1835-1844.
Hill, F.W. 1969. Poultry nutrition and nutrient requirements In:
International
Encyclopaedia of Food and Nutrition 17 (2) (Ed O Cuthbertson)
Pergamon
Press London.
Klasing, K.C. 1998. Comparative avian nutrition. CAB
International. University
Press at Cambridge, UK.
La Thi Thu Minh. 1998. Studies on the Tau Vang chickens.
Unpublished data.
Department of Animal Husbandry.Cantho University.
Leeson, S., Summers, J.D. 1987a. Effect of immature body weight
gain on laying
performance. Poultry Science 66, 1924.
Leeson, S., Summers, J.D.1979. Step-up protein diets for growing
pullets.
Poultry Science 58, 681.
Leng, R.A. 1999. Duckweed - A tiny aquatic plant with enormous
potential for
agriculture and environment. FAO Animal Production and
Health.
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feeding on growth
and subsequent production of pullets. Poultry Science 32,
916.
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to statistics.
Minitab Inc., USA.
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Scientific and
Technical House. Hanoi. Translated from Wirtschaftgeflugel zucht
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haltung- futterung veb Deutscher landwirtschaftsverlag.
Berlin.
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Academy Press. Washington, D.C.1994.
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production in a
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Nigeria.
Smith, A.J. 2001. Poultry. The Tropical Agriculturalist. Revised
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Macmillan Education LTD. London and Oxford.
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1190.
|
Table 1. Ingredient composition of the experimental
diets |
|||||
|
Ingredient |
Treatment |
||||
|
SB100 |
SB75DW |
SB50DW |
SB25DW |
SB0DW |
|
|
Broken rice |
67.5 |
74.5 |
81.5 |
88.5 |
95.5 |
|
Soya bean meal |
28.0 |
21.0 |
14.0 |
7.0 |
0.0 |
|
Shell meal |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
|
Bone meal |
2.0 |
2.0 |
2.0 |
2.0 |
2.0 |
|
Vitamin Premix |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
|
Lysine |
0.2 |
0.2 |
0.2 |
0.2 |
0.2 |
|
Methionine |
0.1 |
0.1 |
0.1 |
0.1 |
0.1 |
|
Duckweed |
0 |
Ad libitum |
Ad libitum |
Ad libitum |
Ad libitum |
|
Cost (VND/kg) |
2906 |
2767 |
2627 |
2486 |
2345 |
|
Table 2. Chemical composition of the experimental diets (% of
DM) and duckweed (DW) |
||||||
|
|
Treatment |
|||||
|
SB100 |
SB75 DW |
SB50 DW |
SB25 DW |
SB0 DW |
DW |
|
|
Dry matter |
86.4 |
89.9 |
86.1 |
85.5 |
86.2 |
4.7 |
|
Crude protein |
16.8 |
14.2 |
12.3 |
10.7 |
9.9 |
37.3 |
|
Amino acids |
|
|
|
|
|
|
|
Lysine |
0.79 |
0.71 |
0.63 |
0.53 |
0.31 |
2.9 |
|
Methionine |
0.43 |
0.41 |
0.4 |
0.37 |
0.31 |
0.7 |
|
Crude fibre |
1.91 |
1.55 |
1.53 |
1.4 |
1.14 |
5.85 |
|
Ether extract |
5.34 |
4.21 |
2.68 |
1.17 |
0.48 |
9.62 |
|
Ash |
6.23 |
6.02 |
6.1 |
5.21 |
1.14 |
17.91 |
|
Calcium |
1.50 |
1.38 |
1.39 |
1.29 |
1.18 |
0.97 |
|
Phosphorus |
0.66 |
0.60 |
0.60 |
0.57 |
0.53 |
1.53 |
|
ME, MJ/kg |
13.17 |
13.17 |
13.16 |
13.15 |
13.15 |
9.3 |
|
(calculated) |
|
|
|
|
|
|
|
Table 3. Effect of replacing soy bean meal by broken rice and
duckweed on total daily nutrient intakes of Tau Vang laying
hens |
|||||||
|
Item |
SB100 |
SB75DW |
SB50DW |
SB25DW |
SB0DW |
SE |
P |
|
Total feed intake, g DM |
41.3 |
47.5 |
37.5 |
44.0 |
54.6 |
7.47 |
0.58 |
|
Conc. intake, g DM |
41.3 |
44.9 |
35.2 |
40.4 |
49.4 |
7.30 |
0.72 |
|
Duckweed, g DM |
0.0 |
2.6b |
2.3b |
3.6ab |
5.2a |
0.52 |
0.00 |
|
CP intake, g |
6.95 |
7.33 |
5.21 |
5.63 |
6.81 |
1.12 |
0.63 |
|
CP from conc., g |
6.95 |
6.35 |
4.34 |
4.30 |
4.88 |
1.06 |
0.33 |
|
CP from DW, g |
0.00 |
0.98b |
0.86b |
1.33ab |
1.93a |
0.19 |
0.00 |
|
CP, % of DM |
16.83a |
15.46b |
13.84c |
12.83d |
12.53e |
0.24 |
0.00 |
|
% of CP from DW |
- |
13.42c |
16.11b |
23.72ab |
28.67a |
2.25 |
0.00 |
|
ME, MJ |
0.54 |
0.62 |
0.49 |
0.56 |
0.70 |
0.10 |
0.63 |
|
Lysine intake, g |
0.32 |
0.40 |
0.29 |
0.32 |
0.30 |
0.05 |
0.68 |
|
Ca, g |
0.62 |
0.64 |
0.51 |
0.55 |
0.64 |
0.10 |
0.87 |
a,b,c,d means without
common superscripts within rows are significantly different
(P<0.05)
|
Table 4. Effect of replacing soy bean meal by broken rice and
duckweed on egg production, feed/egg laid and egg weight of Tau
Vang laying hens |
|||||||
|
Item |
SB100 |
SB75 DW |
SB50 DW |
SB25 DW |
SB0 DW |
SE |
P |
|
FCR, kg feed /kg egg |
1.76 |
2.03 |
1.69 |
1.79 |
2.31 |
0.33 |
0.67 |
|
Age at 1st egg, day |
191 |
177 |
160 |
144 |
173 |
12.68 |
0.17 |
|
Egg production, eggs/layer |
7.6 |
9.9 |
13.5 |
16.0 |
16.2 |
2.9 |
0.22 |
|
Average egg weight, g |
40.8 |
42.5 |
44.9 |
43.5 |
41.8 |
1.65 |
0.49 |
|
% Eggs>38g |
66.3 |
62.1 |
80.7 |
71.0 |
50.7 |
15.3 |
0.72 |
a,b means without common
superscripts within rows are significantly different
(P<0.05)
|
Table 5. Effect of replacing soy bean meal by broken rice and
duckweed on reproductive performance of Tau Vang laying
hens |
|||||||
|
Item |
SB100 |
SB75 DW |
SB50 DW |
SB25 DW |
SB0 DW |
SE |
P |
|
Laying rate, % |
16.7 |
20.7 |
23.6 |
28.7 |
33.0 |
4.44 |
0.16 |
|
Fertile egg rate*, % |
66.7 |
79.2 |
74.1 |
75.1 |
61.0 |
13.28 |
0.89 |
|
Hatchability**, % |
38.9 |
70.0 |
75.4 |
82.2 |
68.7 |
12.24 |
0.21 |
* Proportion of fertile eggs of
incubated eggs
**Proportion of hatched eggs of
fertile eggs
|
Table 6. Effect of replacing soy bean meal by broken rice and
duckweed on egg quality of Tau Vang laying hens |
|||||||
|
Item |
SB100 |
SB75 DW |
SB50 DW |
SB25 DW |
SB0 DW |
SE |
P |
|
Yolk pigmentation |
5.5b |
9.7a |
11.2a |
12.2a |
12.2a |
0.72 |
0.00 |
|
Egg yolk, % |
28.52 |
31.51 |
29.86 |
30.59 |
30.85 |
1.49 |
0.68 |
|
Shell thickness, mm |
0.34 |
0.35 |
0.37 |
0.35 |
0.36 |
0.02 |
0.67 |
|
Egg shape |
75.5ab |
75.2ab |
73.4ab |
77.7a |
69.2b |
1.54 |
0.01 |
|
Index of Albumin |
0.07 |
0.07 |
0.06 |
0.07 |
0.08 |
0.01 |
0.22 |
|
Index of Yolk |
0.38 |
0.41 |
0.41 |
0.43 |
0.44 |
0.01 |
0.11 |
a,bmeans without common
superscripts within rows are significantly different
(P<0.05)
|
Table 7. Effect of replacing soybean meal by broken rice and
duckweed on the economics of egg production of Tau Vang laying hens
for the 8 week experimental period |
|||||
|
Item |
SB100 |
SB75DW |
SB50DW |
SB25DW |
SB0DW |
|
Total feed consumption, g |
2,027 |
2,296 |
2,147 |
2,462 |
2,966 |
|
Feed cost, VND/kg |
2,906 |
2,767 |
2,627 |
2,486 |
2,345 |
|
Total feed cost, VND |
5,890 |
6,353 |
5,640 |
6,120 |
6,955 |
|
Total eggs produced/layer |
7.6 |
9.9 |
13.5 |
16.0 |
16.2 |
|
No.of eggs weighing >38g |
5.0 |
6.2 |
10.9 |
11.4 |
8.2 |
|
No. of fertile eggs, |
3.4 |
4.9 |
8.1 |
8.5 |
5.0 |
|
No. of hatched chicks |
1.3 |
3.4 |
6.1 |
7.0 |
3.4 |
|
Eggs weighing <38g |
2.6 |
3.8 |
2.6 |
4.6 |
8.0 |
|
Income, VND |
8,280 |
18,159 |
27,502 |
33,673 |
23,386 |
|
Sale of chicks, 4,000
VND/chick |
5,217 |
13,645 |
24,368 |
28,093 |
13,787 |
|
Sale of eggs, 1,200 VND/egg |
3,063 |
4,514 |
3,134 |
5,580 |
9,599 |
|
Net profit, VND |
2,390 |
11,806 |
21,862 |
27,553 |
16,431 |
For fertile eggs and eggs > 38g and
<38g present as % of total laid