Two feeding experiments were conducted at the experimental farm
of the Agricultural Faculty of Can Tho University in the South of
Vietnam, to determine the effect of feed selection on the nutrient
intake, growth rate and egg performance of confined improved (Tam
Hoang) and local (Tau Vang) chickens.
Experiment 1 (growing period) was conducted with 166 Tam
Hoang and 160 Tau Vang female chickens from 5 to 18 weeks of age.
The birds were allocated at random to 2 treatments in a 2 * 2
factorial experiment. The first factor was breed (Tam Hoang and Tau
Vang), and the second factor diet, including: "Mixed Diet",
consisting of broken rice, fish meal and oil extracted soya bean,
with oyster meal and bone meal; "Separate Diet", including the
same feedstuffs supplied separately in 3 feeders, and with oyster
and bone meal supplied together with the broken rice. There were
thus 4 treatments with 4 replications, and 20 birds per
experimental unit (pen). The diets were supplied ad -
libitum from 5 to 18 weeks of age when 1 bird/pen was
slaughtered for carcass evaluation.
Total DM and metabolisable energy (ME) intakes were not
significantly different between breeds and treatments. Crude
protein and lysine, methionine, leucine and threonine intakes were
higher for the mixed diet than for the separate diet. The chickens
on the separate diet ate more broken rice, and less soya bean and
fish meal compared to the mixed diet. The ratio of CP to ME intake
was not different between breeds, but was significantly different
between diets. The ratios were 12.7 and 13.7 g CP/MJ ME (P>0.05)
for the Tam Hoang and Tau Vang breeds, respectively, and 14.8 and
11.6 g CP/MJ ME (P<0.001) for the mixed and separate diets,
respectively.
The average daily gain for the Tam Hoang was significantly
higher than for the Tau Vang (20.5 g compared with 10.6 g/day,
respectively). However, there was no significant difference
(P>0.05) between the mixed and separate diets (15.9 g compared
with 15. 3 g/day, respectively). The feed conversion ratios (FCR)
were significantly different between treatments, at 3.2 and 4.1 kg
feed/kg gain (P<0.05) for the mixed and separate diet,
respectively, but were not significantly different between breeds
(2.95 and 3.60 kg feed/kg gain (P>0.05) for the Tam Hoang and
Tau Vang, respectively).
The Crude protein intake from separate diet was lower than that
from the mixed diet, as a result the FCR from separate was higher
than that on the mixed diet. However, the average daily gain was
similar.
Experiment 2 was carried out after the growing period,
from 18 weeks of age onwards, with 72 improved (Tam Hoang) and 75
local (Tau Vang) laying hens by randomly allocating surviving
birds, which continued on the same dietary treatments as in the
growing period. The dietary treatments were the same as for the
growing period, except that maize replaced broken rice to improve
yolk color. There were 10 birds per pen (9 hens and 1 cockerel) and
the total pen number was 16. Data were collected for 20 weeks of
the laying period.
Daily intakes of DM, CP and ME were 15 - 17 % higher for the
improved Tam Hoang hens compared with the local hens. The hen - day
production and egg weight for the Tam Hoang were higher than for
the Tau Vang, 32.7 % and 44.5 g compared with 24.9 %and 39.5 g,
respectively (P<0.05). However, there were no significant
differences between the mixed and separate diets (29.7 and 42.3 g
compared with 27.9 % and 41.7 g, respectively).
The feed consumption and feed cost/kg eggs were not
significantly different between treatments and breeds. The feed
cost per kg eggs for the Tam Hoang was 15,302 VND, and for the Tau
Vang 17,665 VND/kg eggs.
Although the DM and CP intakes of the hens from separate diet
were lower than that from mixed diet, but the egg performance were
similar. Tam Hoang has higher egg performance than Tau Vang,
although DM, CP and FC/kg egg were non significant differences.
Key words: Improved breed, local breed, separate
feeds, mixed diet, growth rate, hen - day production, laying hens.
1. Introduction
Nutrition is of major importance in raising chickens, as feed
accounts for 60 - 90 % of the total production costs (Gunaratne et
al., 1992). However, it is difficult for farmers to formulate diets
that match the birds' requirements and production purpose, as it
requires knowledge of requirements as well as of the nutrient
composition of the feed ingredients. Free choice feeding is a much
more natural and simple system of feeding, since each bird can
fairly accurately select its intake and balance of nutrients to
meet its particular physiological requirements, and free choice
feeding also offers considerable economic advantages to the farmer
(Cumming et al, 1987) because the dietary ingredients offered can
be simple, for example broken rice, paddy rice and soya beans,
which are usually cheap and available on small farms and can be
fed separately for the chickens to select. Also of course the
farmer does not need to formulate the diets himself if the birds
are allowed to select from different feedstuffs.
Feed supplementation is a major problem in rural poultry
production and it has been calculated that scavenging birds are
usually able to find feed for their maintenance, but that higher
levels of production require supplementation (Dessie ,1996). The
ability of the chicken to select a balanced diet from different
foods has been demonstrated in broiler chickens and adult laying
hens, but some of these studies have given varying results,
particularly between different breeds. According to Hong Samnang
(1997), for example, local breed chickens ate less protein
supplement and more broken rice than improved breeds, while exotic
breeds consumed more protein. However, there is little information
on this subject and few studies comparing the feed selection and
performance of local and improved chickens. Therefore, this
experiment, comparing the effects of choice feeding on the growth
rate and egg performance of local Tau Vang and improved Tam Hoang
breeds, was carried out in on- station conditions in order to:
2. Materials and methods
2.1 Experimental design and birds
Two on-station experiments were conducted at the experimental
farm of Cantho University. Experiment 1 was carried out in the
growing period (5 to 18 weeks of age) and Experiment 2 in the
laying period, from 19 to 39 weeks of age.
Experiment 1 was carried out using two breeds of chicken, the
Tau Vang (local) and Tam Hoang (improved). Up to the age of 4
weeks, the chickens were raised on commercial farms and given a
concentrate feed ad - libitum and vaccinated against common
diseases such as Gumboro, Newcastle disease and Fowl pox. In total
324 female and 30 male chickens of the two breeds at 4 weeks of age
were chosen and brought to the experimental farm. They were
de-beaked before the start of the experiment and were fed a 50:50
mixture of the commercial and experimental diets for one adaptation
week. The chickens were weighed initially and data were collected
from five weeks of age. Antibiotics were also supplied in the water
to prevent common diseases.
The experimental design was factorial with 2 factors: the first
one was breed, including a local (Tau Vang) and an improved (Tam
Hoang) breed. The second factor was diet, including the same feed
ingredients, either mixed or provided separately. The ingredients
were broken rice, fish meal and oil extracted soya bean meal. There
were thus four treatment groups with 4 replications, giving 16 pens
with 20 birds / pen (experimental unit). The experiment was a
completely randomized design (CRD).
Experiment 2 was carried out using around half of the surviving
chickens from Experiment1, and continued from the end of the
growing period. It was also carried out on the experimental farm of
Cantho University, from July to December 2002. In Experiment 2, the
same birds and treatments from the growing period were used, except
that broken rice was replaced by maize meal. In total 75 hens /
breed were kept in the same pens (9 hens /pen) as in Experiment 1.
The formulation of the mixed diet was changed to meet the nutrient
requirements of laying hens.
2.2 Experimental diets and management
In the preliminary period (from day 1 to 28 after hatching) the
chickens were fed a commercial starter diet ad-libitum,
which contained 18 % CP and 12 MJ/kg DM. The chickens were
transferred to the experimental farm at 28 days of age and given
the experimental diet for 1 week of adaptation.
The treatments were:
The mixed diet in the growing period contained 17.5% CP and 12.9
MJ/kg.
The composition of the mixed diet in the laying period was:
Maize meal (70.8%), fish meal (12.0 %), Soya bean meal (10.0 %),
bone meal (2%), oyster meal (5%) and premix (0.2%). This formula
was calculated to provide 17.6 %CP, and 12.9 MJ/kg, which are the
requirements of laying hens according to NIAH (1995). Both
treatments included a vitamin premix.
2.3 Housing and environment
The chickens were confined in pens constructed from trellis and
cast nets and bamboo, with concrete floors covered with about 20
cm of rice husks for bedding, with an average density of 4
chickens/ m2 for the growing period and 2 birds per
m2 for the laying period. Natural light was used in the
daytime and artificial light (electric bulbs) at night, with an
intensity of 3 W/m2 at floor level during the whole
experimental period. The temperature inside the house varied
between 25 - 37 0C. At the time of Expt 1 the weather
was very hot, especially in the middle of the day, and this
resulted in some signs of heat stress, especially in the Tam Hoang.
Water was supplied ad - libitum in plastic tube drinkers.
Feeders used were round plastic basins 35 cm in diameter and 40 cm
high, and both feeders and drinkers were cleaned and refilled daily
in the morning.
2.4. Diets and feeding
The chemical composition and nutrient values of ingredients and
diets are shown in Table1. Mixture 1 was used for the period from 5
weeks up to 18 weeks of age, and mixture 2 was used from 18 weeks
of age and throughout the laying period.
2.5. Feed sample analyses and
calculations
The mixed diet and feedstuffs for both experiments were analyzed
for dry matter (DM), crude protein (N*6.25), crude fibre (CF),
ether extract (EE), and ash, Ca, and P by standard AOAC methods
(AOAC, 1990). Analyses of neutral detergent fibre (NDF) of the
mixed feed and ingredients were also done, following the procedure
of Goering and Van Soest (1991). Representative samples of the
mixed diet, broken rice, oil extracted soya bean and fish meal were
sent to the Animal Nutrition Department of the National Institute
of Animal Husbandry in Ha Noi for analysis of amino acids by
using a method of high performance liquid chromatography
(HPLC).(Table 2).
Metabolizable energy (ME) contents of the diets were calculated
from chemical analysis data using the equation of Janssen (1989):
ME (Kcal/kg)
Broken rice ME = 46.7 x DM- 46.7xAsh -69.55 x CP+ 42.95 x
EE-1.95 x CF
Soya bean ME = 37.5 x CP + 70.52 x EE + 14.9 x
NFE
Fish meal ME = 35.87 x DM - 34.08 x Ash + 42.09 x
EE.
2.6. Feed intake and growth
measurements
All 20 chickens in each pen were weighed together as an
experimental unit weekly from 5 weeks of age up to first egg. Daily
feed intake was calculated according to the total feed consumption
of all the chickens in each pen. Fresh feed was offered every day
and feed refusals were recorded every week at the same time as the
birds were weighed, and the feed consumption calculated. At the end
of Expt 1, one chicken in each pen with an average live weight was
slaughtered for evaluation of the carcass and internal organs. From
19 weeks of age, treatments were the same as for the growing
period, except that maize replaced broken rice in both diets. All
eggs from 19 to 38 weeks of age were collected daily from every pen
and weighed to calculate the feed consumption per kg of eggs, and
mean egg weight.
2.7. Mortality and behavior
The initial number of birds and number remaining at the end of
Expt 1 were recorded to calculate mortality, and eating behavior
and incidence of feather picking and disease were also observed and
recorded.
2.8. Statistical analysis
The data were subjected to analysis of Variance (ANOVA) by using
the General Linear Model (GLM) and regression analysis of
MINITAB.13 reference Manual Release 12(1998).
2.9. Economic analysis
Economic analyses were done by using current prices in
Vietnamese Dong (VND) to calculate the differences in total income
and total expenses between the two treatments and breeds (including
feed, chicks, labor, vaccines and medicines) and net profits.
3. Results
3.1 Experiment 1. Growing period
3.1.1 Chemical composition of
feedstuffs
The chemical compositions values of the broken rice, oil
extracted soya bean, fish meal and mixed feed are shown in Table 1.
Broken rice, soya bean, fish meal and mixed feeds had average dry
matter (DM) contents of 87, 89, 89 and 87 %, respectively. The
broken rice used was high in ME (14.4 MJ/kg DM), and low in fiber,
lysine and methionine. Oil extracted soya bean had a fairly high
crude protein content (41.0%) and was relatively high in lysine
(16.5 g/kg DM) and ME. The fish meal was ground from small fish and
was of fairly good quality, with a crude protein content of 48.8 %.
It was bought from the coastal area and dried before grinding. It
was quite high in Ca, P, lysine and methionine (5.3, 2.5, 30.0 and
14.4 g/kg respectively). Broken rice and fish meal are both used
commonly in animal feeds in Vietnam.
In the laying period, maize meal replaced broken rice, as maize
is also a good energy feed source and supplies carotenes for better
yolk color. The chemical composition of the ingredients and the
mixed diet are shown in Table 1. Maize meal, soya bean and fish
meal had average dry matter (DM) contents of 85.9, 87.0, 85.7 and
86.3 %, respectively. The CP (%) and ME contents (MJ/kg) of the
maize meal, soya bean and fish meal and the mixed diet were 9.0 and
13.8, 40.7 and 11.95, 48.5 and 9.15 and 17.6 and 12.85,
respectively. Soya beans and maize were bought and stored in the
grain form, and ground weekly immediately before mixing.
3.1.2 Feed intake
The results in Table 3 and Table 4 show that the total dry
matter intakes (g/day/bird) of the Tam Hoang and Tau Vang breeds
were not significantly different (P>0.05) when the initial
weight of the chickens was taken into account. Also the daily DM
feed intakes on the mixed and separate feeding systems were not
significantly different. The total DM intakes for the Tam Hoang
and Tau Vang birds, respectively, were 61.2 and 40.1 g/day, and
49.9 and 51.4 g/day for the mixed and separate diet,
respectively.
Crude protein intake was not significantly different between
breeds but was significantly different between diets. CP intake was
9.14 g/day and 6.33 g/day (P>0.05) for the Tam Hoang and Tau
Vang, respectively, and for the mixed and separate diet was 8.51
and 6.95 g/day, respectively (P<0.001). The broken rice, fish
meal and soya bean intakes were 35.9, 6.5 and 6.5 g/day for the
mixed diet, and 43.4, 4.8 and 2.3 g/day, respectively, for the
separate diet, and were significantly different between diets
(P<0.001).
Amino acid intakes were not significantly different between
breeds, but were significantly different between diets. Lysine,
methionine, threonine, histidine and arginine intakes were 0.42 and
0.32, 0.21 and 0.14, 0.32 g/day and 0.24, 0.37, 0.23, 0.67 and 0.48
g/day for the Tam Hoang and Tau Vang breed, respectively. Daily
intakes of lysine, methionine, threonine, histidine and arginine
were 0.42 and 0.32, 0.19 and 0.16, 0.31 g/day and 0.23, 0.34 and
0.25 and 0.64 and 0.50 g/day for the mixed and separate diets,
respectively (P<0.05).
The ME intakes were not significantly different between breeds
and diets, and were 0.58 and 0.61 MJ/day for the mixed and separate
diet, and 0.72 and 0.47 MJ/day for the Tam Hoang and Tau Vang
breeds, respectively.
3.1.3 Average daily gain (ADG)
Growth rates were not significantly different between diets, and
were 15.8 and 15.3 g/day (P>0.05) for the mixed and separate
diets, respectively. However, there was a highly significant
difference between breeds, and ADG were 20.5 and 10.6 g/day
(P<0.01) for the Tam Hoang and Tau Vang, respectively.
ME/gain was not significantly different between the Tam Hoang
and Tau Vang (34.9 and 43.1 MJ/kg gain, respectively
(P>0.05).The ME/gain ratio for the mixed diet was 37.0 MJ/kg,
while for the separate diet it was 40.9 MJ/kg gain
(P<0.001).
The CP/gain ratios were not significantly different between
breeds and were 430 and 590 g/kg gain for the Tam Hoang and Tau
Vang, respectively. However, the CP needed for one kg gain for the
separate diet was higher than for the mixed diet, and was 550 and
480 g CP/kg gain, respectively.
3.1.4 Feed conversion ratio and carcass evaluation
FCR were not significantly different between breeds, and were
2.95 and 3.61 kg feed /kg gain for the Tam Hoang and Tau Vang,
respectively. However, they were significantly different between
dietary treatments (P<0.05), and were 3.15 and 3.41 kg feed/kg
gain for the mixed and separate diets, respectively.
The carcass percent was significantly different between diets,
but not for breeds. The carcass proportions were 69 and 66 %
(P<0.05) for the mixed and separate diet, respectively and 72
and 63 % (P<0.05) for the Tam Hoang and Tau Vang, respectively.
The abdominal fat weights were higher (P<001) for the birds
given the separate diet than the mixed diet, and were 43.1 and 85.3
g for the mixed and separate diet respectively, and 99.4 and 29.1 g
for the Tam Hoang and Tau Vang breed, respectively
(P<0.01).
3.1.5 Benefit analysis and mortality for the growing
period
The difference in feed cost/kg gain was not significant
(P>0.05) between diets, the values being 8,611 and 8,677 VND/kg
gain for the mixed and separate diet, respectively. However, there
was a significant difference between the Tam Hoang and Tau Vang,
and the cost for 1 kg of Tam Hoang gain was 8,148 VND while for the
Tau Vang it was 9,140 VND/kg gain.
The mortality was 13.4 % and 5.0 % for the Tam Hoang and Tau
Vang, respectively (P<0.05). However, there were no significant
differences in mortality between diets, at 9.8% and 8.6 % for the
mixed and separate diet, respectively (P>0.05).
3.2 Experiment 2. Laying period
3.2.1. Feed intake
The total daily DM, CP and ME intakes were not significantly
different between breeds, and were 78.2 g, 13.0 g and 1.02 MJ
compared with 64.8g, 11.0g, and 0.84 MJ for the Tam Hoang and Tau
Vang, respectively. The proportions of maize, soya bean and
fishmeal intakes of the total were 72.0, 12.4, and 8.5 % compared
with 71.3, 12.5 and 9.1% for the Tam Hoang and Tau Vang breeds,
respectively. The CP intakes as a percentage of total feed intakes
were 17.0 and 17.3 % for the Tam Hoang and Tau Vang, respectively,
values which were very similar to the balanced feed (17.6 % CP).
However, there were significant differences between the mixed and
separate diets for daily DM (73.8 and 69.2 g/day) and CP (13.0 and
11.0 g) intakes (P<0.05), but no difference for ME intakes (0.95
and 0.92 MJ/day) (P>0.05).
3.2.2. Egg performance, egg weight and feed
consumption per kg eggs
The hen - day production is shown in Table 10, and was
significantly higher (P<0.05) for the Tam Hoang (32.7 %) than
for the Tau Vang (24.9 %). However, there was no significant
difference between the mixed (29.7 %) and separate (27.9 %) diets.
The mean egg weight was significantly different for breed but
not significantly different between treatments, and was 44.5 g
and 39.5 g for the Tam Hoang and Tau Vang, respectively
(P<0.05), and 42.3 and 41.7 g for the mixed and separate diet,
respectively.
Feed conversion (FC, kg feed/ kg eggs) was not significantly
different between breeds and diets, although the Tam Hoang had
somewhat lower FC than the Tau Vang. FC were 5.17 and 5.95 kg feed
in DM /kg eggs for the Tam Hoang and Tau Vang, respectively and
5.55 compared with 5.57 kg feed/kg eggs for the mixed and separate
diets, respectively. As a result the CP and ME intakes/kg eggs were
not significantly different, and were 864g and 67.7 MJ and 1009 g
and 77.9 MJ/kg eggs, respectively for the Tam Hoang and Tau Vang
hens, and 979g and 71.5 MJ, and 893g and 73.9 MJ/kg eggs for the
mixed and separate diets, respectively.
3. Discussion
4.1 Experiment 1
4.1.1 Feed intake
The results for feed intake show that the growing chickens were
able to fairly accurately balance their intake of nutrients to meet
their requirements, even when the ingredients were supplied
separately. This is in agreement with previous studies which have
also shown that poultry have a control system that allows them to
choose suitable amounts of different foods to satisfy their
nutritional requirements, but this is regarded as being too
simplistic and other factors such as physical form of ingredients,
composition of the food, smell, trough position and previous
experience are also likely to be involved (McDonald et al, 1995).
Although the amounts of feed and nutrients consumed between the two
diets and breeds were not significantly different, the proportion
of feedstuffs eaten was different. For example birds on the
separate diet consumed more broken rice (84 %),and less soya bean
meal (4.7 %) and fishmeal (9.6%) compared with the mixed diet which
contained 72 % broken rice, 13 % soya bean meal , and 13 %
fishmeal. As result the total CP in the separate diet was only 13.9
% of total DM intake, which is well below the crude protein of the
mixed diet (17.1%) and below requirements according to NIAH (1995).
Both Tam Hoang and Tau Vang chickens preferred to eat broken rice,
which may have been due to an observation that chickens prefer to
eat a cereal as grain rather than in the ground form. This result
is similar to the findings of Khang (2001) who found that local
chickens preferred to eat broken rice rather than soya bean meal.
Both Tam Hoang and Tau Vang chickens reduced their intake of soy
bean meal to very low levels. This in agreement with Hong Samnang
(1997), who found that local chickens ate less protein supplement
and more broken rice than an exotic breed, which consumed more
protein supplement. However, these differences could also be
explained by the fact that the soya bean that was used in the diet
was oil extracted soya bean, and the smell was not as attractive as
fishmeal
The difference in CP intake thus was considerable, but the two
groups still had similar live weight gains. This implies that the
protein was balanced and sufficient for the birds' requirement.
According to McNaughton et al. (1977 b) the requirements of
starting and growing Leghorns at ages of 84 and 140 days are 14 and
20 % CP. Another study (Leeson and Summers, 1979) showed that the
estimated requirement for White Leghorn chicks at the age of 0 - 56
days was 12% CP. Requirements for CP for the Vietnamese breeds are
likely to be even lower than for the White Leghorn and it seems
thus that both the Tam Hoang and Tau Vang were given diets that met
or were in excess of their requirements. Amino acid intakes were
not different between breeds but were different between diets. This
indicates that both improved and local chickens have the ability
to balance their nutrient intake, including amino acids, to meet
their requirements for growth, and as a result the growth rates of
chickens on the separate diet was as high as the group on the
mixed diet.
ME intakes were not significantly different between breeds and
diets. This indicates that the local breed birds can also adjust
their ME intakes to meet their requirement. Even though the
proportion of ingredients in the separate diet was different from
the mixed diet, and this group ate more broken rice, the difference
in total daily ME intake was not significant. This is agreement
with the study of Cumming et al. (1987) who showed that each bird
can fairly accurately select its intake and balance of nutrients
and energy to meet its particular physiological requirements.
4.1.2 Average daily gain
Although the crude protein intake from the two diets was
different, the average daily gains of birds on the mixed and
separate diets were similar. This indicates that when feed
ingredients were supplied separately, chickens can select to meet
their requirements and that the CP content of the mixed diet was
well in excess of the requirement of both breeds. The Tam Hoang had
a higher growth rate than the Tau Vang, because the Tau Vang is a
small bodied, unselected local breed while the Tam Hoang is a
larger improved dual purpose breed selected for better growth rate
and performance. As a result, the efficiency of feed conversion of
the Tam Hoang was better than the Tau Vang.
4.1.3 Feed conversion ratio and feed cost per kg
gain
Feed cost per kg gain for the Tam Hoang and Tau Vang indicated
that the Tau Vang's lower growth rate was the explanation for the
higher cost per kg gain. However, the net income for the Tau Vang
was not lower than for the Tam Hoang, because consumers, in local
markets at least, prefer Tau Vang meat, and the price of a Tau Vang
bird is always higher than for the Tam Hoang, normally by about
4,000 to 5,000 VND/kg. The net income for the Tam Hoang on the
separate diet was higher than for the Tam Hoang on the mixed diet,
but the cost of the mixed diet was higher than for the separate
diet. This is due to the fact that the Tam Hoang on the separate
diet ate more cheap broken rice and less expensive protein
concentrates, but the overall gain was still similar to the gain on
the mixed diet, and so the feed cost per kg gain for the separate
diet was lower than for the mixed diet. However, even though the
Tau Vang on the separate diet also ate large amounts of broken rice
the weight gain on the separate diet was lower than on the mixed
diet, and so the feed cost per gain was higher than for mixed diet.
4.1.4 Carcass evaluation
The Tam Hoang on the separate diet had high levels of abdominal
fat, because they consumed large amounts of broken rice. The extra
energy that chickens eat is primarily converted to fat under the
skin and abdominal fat (Nguyen Duy Hoan, 1999). This is in
agreement with Smith (1990), who reported that heavy breeds will
consume more energy on a high energy diet than on a low energy one,
and become obese.
4.1.5. Mortality
There was a significant difference in mortality between the Tam
Hoang and Tau Vang pullets, which was higher for the Tam Hoang. As
the experiment started at a time of changing weather, from dry to
rainy season, the chickens, especially the Tam Hoang, which have a
poor ability to adapt to hot, humid weather, were very
uncomfortable. As a result a number of Tam Hoang died suddenly with
no any apparent symptoms. There were no particular diseases
observed in this period.
4.2 Experiment 2. Laying period
4.2.1 Feed intake
The local hens consumed about 17 % less feed DM than the
improved breed. In contrast with the growing period, when the
chickens seemed to prefer fish meal to soya bean meal, in the
laying period oil extracted soya bean meal was replaced with
roasted soya bean meal, which both the Tam Hoang and Tau Vang
obviously liked, as they ate more soya bean than fish meal, and the
difference was significant. This indicates that birds offered two
kinds of protein eat more of what they like and still can balance
nutrient intakes.
The CP intakes were 17.0 and 17.3 % for the Tam Hoang and Tau
Vang hens, respectively. These levels are similar the requirement
of laying hens according to Smith (2001) who stated that the CP
requirement of domestic laying hens in the tropics is 16.5 - 17.5
%. In the laying period hens can adjust the proportion of feed
ingredients they consume more accurately than in growing period, As
a result nutrient intakes more closely met requirements. However,
hens on the mixed and separate diets had significantly different DM
and CP intakes, but there was no difference for ME intake, although
the egg performance and feed consumption per kg eggs were still not
different. This indicates that the diet of the hens on the separate
treatment was balanced and still adequate in terms of CP and amino
acids. According to Washington (1994) chickens do not require a
specific level of crude protein, rather they have a requirement for
specific amino acids plus sufficient protein to supply either the
non - essential amino acids themselves or amino nitrogen for their
synthesis.
4.2.2 Age at first egg and mortality
The Tam Hoang is an improved dual purpose breed. Studies have
shown that the breed has late sexual maturity, especially the Tam
Hoang 882 strain, which lays its first egg at 161 days according to
Le Hong Son (1997). However, in our study the Tam Hoang birds were
of the Luong Phuong strain. In addition, they were reared on
station in early summer when day length was increasing, which could
be the reason that the first egg of the Tam Hoang in our experiment
was as early as 127 days. According to Rose (1997) the mean age
that a flock of poultry reaches sexual maturity depends upon
species and strain, but changing day lengths during rearing also
have a large influence. The Tau Vang is local dual purpose breed,
rather than a layer breed, which could explain why the first egg of
Tau Vang was10 days later than the Tam Hoang.
The mortality rates for the Tam Hoang and Tau Vang hens were
15.0 % and 29.8 %, respectively (P<0.05). The laying period was
from July to November, so the Tam Hoang in this period had adapted
to the hot weather. Tau Vang deaths were caused by Mareks disease,
against which they were not vaccinated. However, the Tam Hoang,
purchased in Ho Chi Minh City, were vaccinated against Mareks
disease.
4.2.3 Egg performance, egg weight and feed
consumption per kg eggs
The Tam Hoang's egg production was higher than the Tau Vang's at
32.7 % and 24.9 % respectively, for the 20 weeks of laying. The
highest egg rate was from 8 to 13 weeks, and after that egg
performance decreased slowly, which is the usual pattern. As the
Tam Hoang reached sexual maturity earlier than the Tau Vang, so the
highest egg rate was between week 8 to 13, while for the Tau Vang
it was between week 11 to 14 after the first egg. A similar
difference in egg performance between local and improved breeds was
found by Do Viet Minh (1999), who reported that the hen-day
production from Tam Hoang and Ri (an unimproved local breed common
in North Vietnam) hens was 39.5 and 17.9 % for 14 weeks of laying,
which also shows that the Ri hen has lower egg performance than the
Tau Vang and Tam Hoang breeds.
4.2.4 Mean egg weight
The egg weight for the on-station hens was slightly higher than
for the same breed reared on farm (Paper II). This agrees with a
study by Do Viet Minh (1999), who showed that egg weight is
affected by nutrient intake, and also depends on breed and strain,
and in particular on mature body weight. The egg weights were
nearly similar on the two diets, however, which indicates that the
different nutrient and ME intakes from the mixed and separate diets
did not affect egg weight.
4.2.5 Economic analysis
The feed costs per kg eggs for the two breeds were not
significantly different, although the feed cost per kg of Tam Hoang
eggs was slightly lower than for the Tau Vang (15,302 and
17,6652 VND/kg eggs, respectively (P>0.05), which is 13.7 %
lower for the improved hens compared with local hens. This
difference is due to the lower egg performance of the Tau Vang.
However, the feed consumption for 1 egg was similar (230 and 235
g/egg for the Tan Hoang and Tau Vang, respectively) (P>0.05).
Consequently, as market prices per egg are similar for the two
breeds, raising Tam Hoang and Tau Vang hens give similar economic
benefits, at least under on-station conditions. The results from
this study are quiet different from the results of Do Viet Minh
(1999), who found that the feed consumption per kg eggs for the
Tam Hoang was lower than for the Ri by about 36 %.
There was no significant difference between the two treatments
in feed costs per kg eggs and also CP and ME required to produce 1
kg eggs were not significantly different. It seems that both Tam
Hoang and Tau Vang balance their feed and nutrient intakes for
maximum production and as a result the economic benefits on the
mixed and separate diets were similar
5. Conclusions
DM, CP and ME intakes for the two breeds in the growing period
were not different, but were in the laying period. However, intakes
of CP and amino acids were lower on the separate diet than on the
mixed diet. Average daily gain, egg performance and feed
consumption per kg eggs were not different between the mixed and
separate diets.
The growth rate of the Tam Hoang was higher than of the Tau
Vang, but the feed conversion ratio was not different between the
two breeds.
The feed consumption of the Tam Hoang hens was 18 % higher than
of the local Tau Vang breed, and also egg performance of the Tam
Hoang was higher than the Tau Vang. However, feed conversion per kg
eggs was not different between treatments and breeds, which
indicates that both improved and local breed hens seem able to
balance their nutrient intakes to meet their requirements for body
maintenance and egg production.
Acknowledgements
Appreciation is expressed to the Swedish Agency for Research
Co-operation with Developing Countries (SAREC) and the Swedish
University of Agricultural Sciences (SLU) for its financial and
material support of this study.
I am also indebted to the Department of Animal Husbandry,
College of Agriculture and Experimental farm for allowing me to use
the facilities and chicken house for my work.
I would like to thank to my supervisor, Dr. Brian Ogle who has
spent a lot of time to correct and guide my studies. Many thanks
to my teacher Mrs.La Thi Thu Minh for her help and devoted
guidance, to the head of the experimental farm for his enthusiastic
help and encouragement. Also thanks to the staff of the
experimental farm for their help and cooperation.
Many thanks to my colleagues Kim Khang and my assistants Hau,
Quyen, Thoai, Giau, Long, Linh, Binh, Ut, Quan for their valuable
help.
Special thanks to my family for their encouragement and help, to
my husband Hong Tien for his help and love, to my daughter Hong
Nhung for her love.
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revised edition, 1994. 9 -33, 85-90.
Table 1. Chemical composition of feedstuffs and the mixed diet,
growing period (in DM)
|
Item |
Broken rice |
Soya bean meal |
Fish meal |
Mixed diet |
|
DM (%) |
87.5 |
89.0 |
89.0 |
87.8 |
|
CP (%) |
8.3 |
41.0 |
48.9 |
17.1 |
|
EE (%) |
0.6 |
3.4 |
3.0 |
1.2 |
|
CF (%) |
0.6 |
4.4 |
3.6 |
1.5 |
|
Ash (%) |
1.2 |
3.8 |
29.9 |
5.0 |
|
NFE (%) |
76.8 |
39.0 |
4.0 |
61.5 |
|
NDF (%) |
1.3 |
8.7 |
2.4 |
2.2 |
|
Ca (%) |
1.3 |
0.9 |
5.3 |
0.97 |
|
P (%) |
0.28 |
0.7 |
2.5 |
0.72 |
|
Lysine (g/kg) |
3.2 |
16.5 |
30 |
8.5 |
|
Methionine,g/kg |
1.8 |
5.3 |
14.4 |
4.0 |
|
ME (MJ/kg) |
14.41 |
9.7 |
9.8 |
12.9 |
|
(Calculated) |
|
|
|
|
Table 2. Essential amino acid composition of feed ingredients
and the mixed diet, growing period
|
Amino acid |
% in DM |
|
||
|
|
Broken rice |
Soya bean meal |
Fish meal |
Mixed diet |
|
Lysine |
0.32 |
1.66 |
3.0 |
0.84 |
|
Isoleucine |
0.32 |
1.71 |
2.09 |
0.73 |
|
Leucine |
0.65 |
2.93 |
3.49 |
1.31 |
|
Methionine |
0.19 |
0.53 |
1.44 |
0.39 |
|
Threonine |
0.23 |
1.46 |
2.15 |
0.64 |
|
Valine |
0.44 |
1.9 |
2.45 |
0.89 |
|
Phenylalanine |
0.34 |
2.0 |
1.98 |
0.77 |
|
Histidine |
0.28 |
2.05 |
1.72 |
0.69 |
|
Arginine |
0.57 |
2.62 |
4.09 |
1.29 |
|
Tryptophan |
0.12 |
0.41 |
1.2 |
0.28 |
Table 3. Effect of breed on DM and nutrient intake, FCR and
average daily gain, growing period
|
Item |
Breed |
SE |
P-value |
|
|
TH |
TV |
|||
|
Initial weight, g |
609 |
319 |
71.53 |
0.000 |
|
Final weight, g |
2130 |
1290 |
90 |
0.001 |
|
ADG, g * |
20.5 |
10.7 |
1.45 |
0.009 |
|
Total DM intake, g/day * |
61.2 |
40.1 |
5.76 |
0.073 |
|
CP intake, g/day * |
9.14 |
6.33 |
1.01 |
0.061 |
|
CP intake,% of total DM |
15.5 |
16.5 |
|
|
|
ME intake, MJ/day * |
0.72 |
0.47 |
0.07 |
0.092 |
|
FCR, kg/kg * |
2.95 |
3.61 |
0.40 |
0.716 |
|
CP/gain (g/kg) * |
430 |
590 |
84 |
0.364 |
|
ME/gain, MJ/kg * |
34.9 |
43.1 |
5.01 |
0.426 |
|
CP/ME, g/MJ * |
12.74 |
13.7 |
0.7 |
0.505 |
|
Lysine,g |
0.42 |
0.32 |
0.05 |
0.307 |
|
Methionine, g |
0.21 |
0.14 |
0.02 |
0.174 |
|
Threonine |
0.32 |
0.24 |
0.04 |
0.326 |
|
Mortality, % |
13.4 |
5 |
2.42 |
0.029 |
|
|
|
|
|
|
(*) Adjusted by covariance according to initial
weight
Table 4. Effect of dietary treatment on DM and nutrient intakes,
FCR and ADG
|
Items |
Diet |
SE |
P-value |
|
|
Mixed |
Separate |
|||
|
Initial weight, g |
464 |
464 |
0.007 |
0.971 |
|
Final weight, g |
1740 |
1670 |
15 |
0.013 |
|
Total DM intake, g/day * |
49.9 |
51.4 |
0.96 |
0.309 |
|
CP intake, g * |
8.51 |
6.95 |
0.17 |
0.000 |
|
CP intake,% of total DM |
17.1 |
13.9 |
|
|
|
ME intake, MJ/day * |
0.58 |
0.61 |
0.012 |
0.074 |
|
FCR * |
3.15 |
3.41 |
0.068 |
0.018 |
|
ADG, g * |
15.9 |
15.3 |
0.24 |
0.157 |
|
CP/gain (g/kg) * |
550 |
480 |
14 |
0.006 |
|
ME/gain (MJ/kg) * |
37 |
40.9 |
0.84 |
0.007 |
|
CP/ME (g/MJ) * |
14.81 |
11.63 |
0.11 |
0.000 |
|
Lysine,g |
0.42 |
0.32 |
0.008 |
0.000 |
|
Methionine, g |
0.19 |
0.16 |
0.004 |
0.000 |
|
Threonine |
0.32 |
0.24 |
0.006 |
0.000 |
|
Mortality (%) |
9.8 |
8.6 |
2.42 |
0.716 |
(*) Adjusted by covariance according to initial
weight
Table 5. Effect of treatment and breed on the proportion of
the ingredients of total daily feed intake, growing period
(%).
|
Item |
Treatment |
Breed |
||||||
|
Mixed |
Sep |
SE |
P-value |
TH |
TV |
SE |
P-value |
|
|
|
|
|
|
|
|
|
|
|
|
Broken rice, % |
72.0 |
84.0 |
0.40 |
0.00 |
79.3 |
76.6 |
0.40 |
0.000 |
|
Soya bean, % |
13.0 |
4.7 |
0.42 |
0.00 |
8.3 |
9.4 |
0.42 |
0.073 |
|
Fish meal,% |
13.0 |
9.6 |
0.15 |
0.00 |
10.5 |
12.1 |
0.15 |
0.000 |
|
Oyster, bone meal, % |
2.0 |
1.7 |
0.01 |
|
1.9 |
1.8 |
|
|
|
CP % |
17.1 |
13.9 |
|
|
15.5 |
16.5 |
|
|
Table 6. Effect of breed and treatment on relative intakes of
the dietary ingredients (%)
|
Item |
Tam Hoang |
Tau Vang |
|
|
||
|
SE |
P-value |
|||||
|
Mixed |
Sep. |
Mixed |
Sep. |
|
|
|
|
Broken rice,% |
72.0 |
86.6 |
72.0 |
81.3 |
0.56 |
0.000 |
|
Soya bean,% |
13.0 |
3.5 |
13.0 |
5.8 |
0.60 |
0.000 |
|
Fish meal,% |
13.0 |
8.1 |
13.0 |
11.2 |
0.21 |
0.000 |
|
Oyster, bone meal, % |
2.0 |
1.7 |
2.0 |
1.7 |
0.01 |
|
|
CP, % |
17.1 |
12.9 |
17.1 |
14.9 |
|
|
|
|
|
|
|
|
|
|
Table 7. Effect of breed and dietary treatment on carcass
characteristics.
|
Iterm |
Breed (B) |
Diet (D) |
P-value |
||||
|
Tam |
Tau Vang |
Mixed |
Sep |
Breed (B) |
Diet (D) |
B*D |
|
|
Hoang |
|||||||
|
Live weight, g |
1989 |
1178 |
1603 |
1564 |
0.00 |
0.16 |
0.07 |
|
Carcass weight, g * |
1162 |
997 |
1097 |
1062 |
0.23 |
0.04 |
0.96 |
|
% carcass |
72 |
63 |
69 |
66 |
0.24 |
0.03 |
0.62 |
|
Breast muscle, g * |
253 |
236 |
253 |
236 |
0.83 |
0.04 |
0.17 |
|
Thigh muscle,g * |
199 |
179 |
197 |
180 |
0.58 |
0.00 |
0.12 |
|
Gizzard /carcass ,% |
3.6 |
6.0 |
4.7 |
5.0 |
0.53 |
0.61 |
0.40 |
|
Abdominal fat, g * |
99.4 |
29.1 |
43.1 |
85.3 |
0.02 |
0.00 |
0.14 |
|
Abd fat/carcass, % |
7.2 |
3.7 |
4.0 |
7.0 |
0.06 |
0.01 |
0.22 |
|
Liver/carcass % |
4.5 |
2.4 |
3.4 |
3.5 |
0.12 |
0.80 |
0.05 |
|
|
|
|
|
|
|
|
|
(*)Adjusted by covariance according to live
weight
2. Laying period
Table 8. Effects of breed on egg production, egg
weight, feed conversion and mortality.
|
Items |
Breed |
SE |
P-value |
|
|
Tam Hoang |
Tau Vang |
|||
|
Daily feed intake (g) (*) |
78.2 |
64.9 |
7.1 |
0.364 |
|
Daily CP intake (g) (*) |
13.2 |
10.8 |
1.3 |
0.474 |
|
CP intake,% of total DM |
17.0 |
17.3 |
|
|
|
Daily ME intake (MJ) (*) |
1.02 |
0.84 |
0.1 |
0.363 |
|
Total eggs |
3095 |
1865 |
|
|
|
Hen- day production (%) |
32.7 |
24.9 |
1.93 |
0.015 |
|
Egg weight (g) |
44.5 |
39.5 |
0.47 |
0.000 |
|
FCR (kg feed/kg eggs) |
5.17 |
5.95 |
0.34 |
0.135 |
|
CP/kg eggs (g/kg ) |
864 |
1009 |
60 |
0.112 |
|
ME/kg eggs (MJ/kg) |
67.6 |
77.9 |
4.5 |
0.135 |
|
Feed cost/kg eggs (VND/kg) |
15,302 |
17,655 |
1044 |
0.137 |
|
Mortality (%) |
15.0 |
29.8 |
4.6 |
0.044 |
|
AWG (g/day) |
3.8 |
3.9 |
0.17 |
0.686 |
|
|
|
|
|
|
(*) Adjusted by covariance according to initial
weight
Table 9.Effect of dietary treatment on egg production, egg
weight, feed per kg eggs and mortality.
|
Items |
Treatment |
SE |
P-value |
|
|
Mixed |
Separate |
|
||
|
Daily feed intake (g) (*) |
73.8 |
69.2 |
1.20 |
0.023 |
|
Daily CP intake (g) (*) |
13.0 |
11.0 |
0.23 |
0.000 |
|
CP intake,% of total DM |
17.6 |
16.7 |
|
|
|
Daily ME intake (MJ) (*) |
0.95 |
0.92 |
0.02 |
0.205 |
|
Total eggs |
2456 |
2504 |
|
|
|
Hen-day production (%) |
29.68 |
27.96 |
1.93 |
0.541 |
|
Egg weight (g/) |
42.31 |
41.71 |
0.47 |
0.390 |
|
FCR/ (kg feed/kg eggs) |
5.55 |
5.57 |
0.34 |
0.960 |
|
CP/kg eggs (g/kg ) |
979 |
894 |
60 |
0.331 |
|
ME/kg eggs (MJ/kg) |
71.5 |
73.9 |
4.5 |
0.713 |
|
Feed cost /kg eggs (VND/kg) |
16,756 |
16,202 |
1044 |
0.714 |
|
Mortality (%) |
27.8 |
17.2 |
4.6 |
0.134 |
|
AWG (g/day) |
4.2 |
3.5 |
0.17 |
0.024 |
(*) Adjusted by covariance according to initial
weight
Table 10. Effect of breed and treatment on egg production, egg
weight and feed conversion
|
Item |
Tam Hoang |
Tau Vang |
SE |
P-value |
||
|
Mixed |
Sep. |
Mixed |
Sep. |
|||
|
Daily FI (g) (*) |
81.8 |
74.5 |
65.8 |
63.9 |
7.20 |
0.156 |
|
Daily CP I (g) (*) |
14.3 |
11.6 |
11.6 |
10.5 |
1.37 |
0.032 |
|
CP ,% of total DM |
17.6 |
16.4 |
17.6 |
16.9 |
|
|
|
Daily ME I (MJ) (*) |
1.06 |
1 |
0.84 |
0.84 |
0.1 |
0.228 |
|
Total eggs |
1531 |
1564 |
925 |
940 |
|
|
|
Hen- day, (%) |
33.2 |
32.3 |
26.27 |
23.6 |
2.7 |
0.742 |
|
Egg weight (g) |
44.9 |
44.1 |
39.6 |
39.3 |
0.67 |
0.690 |
|
FCR/ (kg /kg egg) |
5.42 |
4.92 |
5.67 |
6.22 |
0.48 |
0.299 |
|
CP/kg egg (g/kg ) |
956 |
772 |
1003 |
1015 |
84.8 |
0.272 |
|
ME/kg egg (MJ/kg) |
69.8 |
65.4 |
73.3 |
82.4 |
6.4 |
0.310 |
|
Feed cost/kg egg (VND/kg) |
16,346 |
14,258 |
17,166 |
18,145 |
1477 |
0.320 |
|
Mortality (%) |
20.0 |
10.0 |
35.0 |
24.0 |
6.6 |
0.926 |
|
AWG (g/day/hen) |
4.2 |
3.5 |
4.27 |
3.6 |
0.24 |
0.919 |
(*) Adjusted by covariance according to initial
weight
Table 11. Effect of dietary treatment on daily feed and
ingredient intake (%)
|
Items |
Dietary treatment |
Breed |
||||||
|
Mix |
Sep |
SE |
P-value |
TH |
TV |
SE |
P-value |
|
|
MM, % |
71.0 |
72.4 |
0.15 |
0.000 |
72.0 |
71.3 |
0.15 |
0.006 |
|
SBM, % |
10.0 |
14.9 |
0.18 |
0.000 |
12.4 |
12.5 |
0.18 |
0.638 |
|
FM, % |
12.0 |
5.6 |
0.06 |
0.000 |
8.5 |
9.1 |
0.06 |
0.000 |
|
Oyster, BM,% |
7.0 |
7.0 |
|
|
7.0 |
7.0 |
|
|
|
CP% |
17.6 |
16.7 |
|
|
17.0 |
17.3 |
|
|
|
|
|
|
|
|
|
|
|
|
Table 12. Effect of breed and treatment on relative intakes of
the dietary ingredients (%).
|
Item |
Tam Hoang |
Tau Vang |
SE |
P-value |
||
|
Mixed |
Sep. |
Mixed |
Sep. |
|
||
|
Maize meal, % |
71.0 |
73.1 |
71.0 |
71.6 |
0.21 |
0.006 |
|
Soya bean meal, % |
10.0 |
14.8 |
10.0 |
15.0 |
0.25 |
0.000 |
|
Fish meal, % |
12.0 |
5.0 |
12.0 |
6.2 |
0.09 |
0.000 |
|
Oyster, bone meal,% |
7.0 |
7.0 |
7.0 |
7.0 |
|
|
|
CP, % |
17.6 |
16.4 |
17.6 |
16.9 |
|
|
|
|
|
|
|
|
|
|