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MEKARN Regional Conference 2007: Matching Livestock Systems with Available Resources |
The effect of two processing techniques (sun-drying before and after 40 days ensiling) with 3 supplementation levels (low, medium and high) of cassava residue meal (CReM) in the diet was investigated in 280 Luong phuong broiler chickens from 28 to 84 days old. The experiment included 7 treatment groups, of which one group was fed a control diet, and 6 groups were given either fresh or ensiled CReM at low, medium and high level of inclusion. All the diets were balanced with respect to nitrogen, lysine, and methionine + cystine content, corresponding to the requirements of growing and finishing broilers. There was no effect of processing technique on the content of crude protein and crude fibre (% of dry matter) in the CReM, or on growth performance and carcass traits at 84 days old. Supplementation of CReM at low and medium level (10-15% and 15-20%, corresponding to growing and finishing diets, respectively) did not affect growth rate and feed conversion ratio. Supplementation up to 20 and 25% in growing and finishing diets resulted in the highest economic efficiency but reduced carcass traits. Carcass, breast, and leg muscle percentage was lowest in the groups fed the high level of CReM, while in contrast abdominal fat percentage was reduced with increased CReM in the diets. There was no difference among treatments in the crude protein and ether extract content in leg muscle.
Introduction
In Vietnam, by-products such as rice bran, sweet potato vine, brewer’s grain and cassava leaves are available and can be used as feed ingredients for livestock diets in general, including poultry. Although their main characteristic is a high fibre content, they sometimes they have relatively high protein or energy content. The effect of these feedstuffs on growth performance of poultry is variable, depending on factors such as level of supplementation, breed and dietary nutrient balance. For example, Dong (2005) concluded that brewer’s grain can replace up to 100% of the concentrate feed in the diets of growing ducks, and a level of 50% replacement was the economic optimum for Muscovy ducks. A study by Borin et al (2006) showed that digestibility of dry matter in chicken and duck broilers was negatively affected by the level of inclusion of cassava leaf meal in the diet.
Cassava residue, which is a by-product of cassava starch processing, is abundant during the harvesting and processing season, and consequently most of this product is wasted and causes environmental pollution, because of its high water content. Drying and ensiling are known methods to preserve it as animal feed for long time, and to reduce environmental pollution. However, drying fresh cassava residue is based mainly on the traditional method of sun-drying and depends on weather conditions. Therefore, in a short season of processing starch, it is not possible by sun-drying to process as large amounts of cassava by-product as ensiling. A combination of two these methods is a potentially valuable alternative that should be easy to apply in practice. Therefore this study was aimed at evaluating the effects of supplementation of fresh and ensiled cassava residue meal to the diet on the growth performance and carcass traits of Luong phuong broilers.
Materials and Methods
The experiment was conducted at the experimental farm of the National Institute of Animal Husbandry, from March to May 2007.
Cassava residue was collected immediately after processing the cassava root for starch, and was then pressed overnight to reduce the water content before being dried by sunshine for 2-5 consecutive days. The final product, dry cassava residue, was ground by machine and stored in plastic bags
Fresh cassava residue was collected immediately after processing the root, then pressed overnight to reduce the water content before being put in plastic bags and ensiled anaerobically for 40 days. After 40 days of ensiling, the cassava residue was dried by sunshine for 2-5 consecutive days, and then ground by machine and stored in plastic bags. Samples of fresh and sun dried cassava residue before and after ensiling were taken for analysis of chemical composition (table 1). Analysis was done in duplicate for each sample.
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Table 1: Chemical composition of different types of cassava residue |
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DM (%) |
CP (% of DM) |
CF (% of DM) |
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Fresh, before drying |
41.3 ± 3.0 |
1.75 ± 0.5 |
17.9 ± 0.7 |
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Fresh after 3-5 days of sun-drying |
85.1 ± 1.0 |
1.85 ± 0.5 |
17.3 ± 0.4 |
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Silage, before drying |
42.3 ± 1.0 |
1.68 ± 0.5 |
16.9 ± 0.2 |
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Silage after 3-5days of sun-drying |
86.5 ± 0.5 |
1.67 ± 0.5 |
17.4 ± 0.2 |
The experiment had 2*3 factorial arrangement with 2 types of cassava residue meal (fresh meal and after ensiling) and 3 levels of supplementation of cassava residue (low, medium and high). The experiment included 280 chickens at an initial age of 28 days divided randomly into 7 treatment groups with 4 pens/group (10 birds/pen), with each pen considered as a replicate. The arrangement of experimental diets and groups is shown below:
· Group 1: Control diet (C)
· Group 2 and 3: Low level (L) of fresh and ensiled CReM, respectively
· Group 4 and 5: Medium level (M) of fresh and ensiled CReM, respectively
· Group 6 and 7: High level (H) of fresh and ensiled CReM, respectively
The chickens in each group were arranged to have similar initial average body weight and sex. Vaccination was done according to normal veterinary procedures for broilers from 28 to 84 days old. The feed and water were supplied ad libitum in separate strays within a pen.
The experimental duration was 56 days, divided into two periods, growing and finishing. The concentrations of CP, lysine and methionine + cystine in all experimental diets were balanced and met requirements for Luong phuong broilers in each feeding period. All feed ingredients were ground to pass through a 5 mm diameter screen before mixing. The feeds were presented as a meal throughout the study. The ingredient and chemical composition of the experimental diets are presented in table 2.
The samples of FCReM, ECReM, fresh cassava residue and silage were analysed for DM, CP and CF (table 1). All chickens were weighed at the beginning and at the end of each feeding period in the early morning after overnight fasting. Offered and refused feed were recorded daily. At the end of the experiment, after 12 hours fasting, within a group four broilers (2 males and 2 females) were slaughtered to measure carcass traits. Hot carcass weight was live body weight at slaughter minus weight of blood, feathers, full gastro-intestinal tract and visceral organs. The abdominal fat, breast and leg muscle were weighed and expressed as proportion of hot carcass weight (%). Samples of leg muscle were taken for analysis of DM, CP and ether extract.
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Table 2: Ingredient and chemical composition of the experimental diets, % of DM |
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Ingredient |
Growing period* |
Finishing period* |
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C |
L |
M |
H |
C |
L |
M |
H |
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Maize meal |
73.6 |
61.4 |
55.3 |
49.2 |
75.8 |
61.2 |
55.1 |
49.0 |
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CReM |
0 |
10 |
15 |
20.0 |
0 |
15 |
20.0 |
25.0 |
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Soy bean meal |
20.7 |
22.9 |
24 |
25.2 |
15.5 |
18.1 |
19.2 |
20.3 |
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Fish meal |
4.0 |
4.0 |
4.0 |
4.0 |
4.0 |
4.0 |
4.0 |
4.0 |
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Limestone |
0.9 |
0.8 |
0.8 |
0.8 |
3.8 |
0.9 |
0.9 |
0.9 |
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Vitamins-minerals |
0.3 |
0.3 |
0.3 |
0.3 |
0.3 |
0.3 |
0.3 |
0.3 |
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Lysine |
0.2 |
0.16 |
0.14 |
0.13 |
0.23 |
0.19 |
0.17 |
0.15 |
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Methionine |
0.11 |
0.12 |
0.12 |
0.13 |
0.06 |
0.07 |
0.08 |
0.08 |
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Salt (NaCl) |
0.3 |
0.30 |
0.30 |
0.30 |
0.30 |
0.30 |
0.30 |
0.30 |
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Chemical composition |
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ME** (MJ/kg) |
12.8 |
12.4 |
12.2 |
12.01 |
12.50 |
12.29 |
12.09 |
11.88 |
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CP (%) |
18.1 |
18.2 |
17.8 |
18.3 |
16.2 |
16.3 |
16.0 |
16.4 |
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CF (%) |
3.5 |
4.7 |
5.3 |
5.93 |
3.28 |
5.16 |
5.77 |
6.37 |
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Ca (%) |
0.6 |
0.6 |
0.6 |
0.60 |
1.48 |
0.60 |
0.60 |
0.60 |
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P (%) |
0.5 |
0.5 |
0.5 |
0.46 |
0.43 |
0.43 |
0.43 |
0.44 |
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Lysine (%) |
1.05 |
1.05 |
1.05 |
1.05 |
0.95 |
0.95 |
0.95 |
0.95 |
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Meth+Cys (%) |
0.65 |
0.65 |
0.65 |
0.65 |
0.55 |
0.55 |
0.55 |
0.55 |
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*: C is control diet; L, M and H are diets containing low, medium and high level of CReM, respectively **Sources: NIAH (2001); ME, CP, CF; Meth+Cys: dry matter, metabolisable energy, crude protein, crude fibre and methionine + cystine,r espectively |
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The collected data were analysed by ANOVA using GLM of MINITAB Software 13.31 using two models:
Model 1 (excluded control group): Y = M + Ti + Lj + (T*L)ij + eij; Where Y is performance and carcass traits; M is overall mean; Tj is effect of type i of CReM; Lj is effect of level j of CReM in the diet (L, M and H diet); (T*L)ij is interaction effect of type i and level j; eij is effect of error.
Model 2 (included control group): Y = M + Li + ei; Where Y is performance and carcass traits; M is overall mean; Li is effect of level i of CReM (C, L, M and H diet); ei is effect of error.
In Model 1 the effect of type of CReM and interaction between type and level of CReM in the diet were not significant (P>0.05), and were removed from Tables 3 and 4.
As expected, CP and CF contents, expressed as percentage of DM (table 1) were not influenced by ensiling and sun drying. Crude protein content ranged between 1.68 and 1.75 % and CF was between 16.9 and 17.9 %. In general, cassava residue contained low crude protein and high fibre. The calculated metabolisable energy of CReM was about 9.6 MJ/kg DM (NIAH 2001).
As expected, supplementation of the two types of CReM had no effect on growth performance, irrespective of level of inclusion.The effects of processing method and level of supplementation of CReM on feed intake, growth performance and feed conversion ratio of Luong phuong broilers are shown in table 3. During the growing period, irrespective of the type of meal, the groups given the high level of CReM had higher feed intake than those in the other groups (P<0.05). During the finishing period and overall, the trend of feed intake was similar to that in growing period but did not reach significance (P>0.05).
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Table 3: Effect of supplementation level and processing method of cassava residue meal on growth performance of broiler chickens |
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Item |
CReM level* |
Type of meal |
SEM** |
Significance |
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C |
L |
M |
H |
Fresh |
Silage |
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P (1) |
P (2) |
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DFI 1 |
77a |
78a |
80a |
86b |
81 |
81 |
2.2 |
* |
** |
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DFI 2 |
90 |
88 |
89 |
93 |
91 |
89 |
5.6 |
NS |
NS |
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Overall |
84 |
84 |
85 |
89 |
86 |
85 |
2.7 |
NS |
NS |
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IBW |
389 |
390 |
375 |
375 |
389 |
374 |
8.9 |
NS |
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FBW1 |
1288ab |
1276a |
1220ab |
1193b |
1236 |
1224 |
24.3 |
* |
* |
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FBW2 |
1968ab |
1960a |
1856ab |
1812b |
1889 |
1863 |
42.8 |
* |
* |
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ADG1 |
32a |
32a |
30ab |
29b |
30 |
30 |
0.73 |
* |
* |
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ADG2 |
24 |
24 |
23 |
22 |
23 |
23 |
1.03 |
NS |
NS |
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Overall |
28ab |
28a |
27ab |
26b |
27 |
27 |
0.71 |
* |
* |
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FCR 1 |
2.40a |
2.48a |
2.66ab |
2.93b |
2.69 |
2.68 |
0.08 |
** |
** |
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FCR 2 |
3.79 |
3.63 |
3.90 |
4.22 |
3.92 |
3.92 |
0.20 |
NS |
NS |
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Overall |
2.99a |
2.99a |
3.18ab |
3.48b |
3.22 |
3.21 |
0.10 |
** |
* |
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Within a row, mean values with different superscript letters are significantly different (P<0.05) *See footnote in table 2;**SEM: pooled SEM P (1): P value included control diet, P (2): P value excluded control diet; NS is non-significant; DFI is daily feed intake (g/bird/day); IBW is initial body weight (g), FBW is final body weight (g); ADG is average daily gain (g/bird/day), FCR is feed conversion ratio (kg feed/kg gain) |
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There was a tendency for average daily gain (ADG) to decrease and feed conversion ratio (FCR) to increase as the level of CReM in the diet increased. In the growing period and overall, ADG and FCR of the broilers in group L and M were comparable to those in group C (P>0.05), while they was poorest in group H (P<0.05). There were no significant differences in ADG and FCR between treatments in the finishing period. This implies that the ability to utilize CReM improves with age.
The explanation of the results for feed intake in the current study is mainly attributed to the energy concentration in the experimental diets, which were diluted by adding CReM. The higher feed intake in diet H was due to the lower ME content in the diet. This result is comparable to the findings of Onifade and Babatunde (1998) and Hetland and Svihus (2001) that broilers on low energy diets attempted to adjust food intake to meet their energy requirement, because among nutrients energy concentration is the first factor affecting voluntary feed intake of chickens fed ad libitum (NRC, 1994). Similarly, Dong (2005) indicated that Common and Muscovy ducks fed diets with higher replacement levels of concentrate feed with brewer’s grain had higher DM feed intake than those on diets at lower replacement level. This was a result of the difference in ME content between brewer’s grains and concentrate feed (7.3 verses 12.9 MJ/kg DM, respectively). In the current study, the negative effect of the high level of CReM on ADG and FCR is mainly related to the high fiber content in the diets, that reduced nutrient digestibility and consequently reduced growth performance and efficiency of feed utilization (Jorgensen et al, 1996; Onifade and Babatunde, 1998).
The lack of difference in feed intake between FCReM and ECReM was probably due to the fact that there was no change in chemical composition due to processing method.
The effects of processing method and supplementation level of CReM on the carcass traits of the broilers at 84 days of age are presented in table 4.
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Table 4: Effect of supplementation level and type of cassava residue meal on carcass percentage (%) and chemical composition of lean meat (%) |
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Item |
CReM level* |
Type of meal |
SEM** |
Significance |
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C |
L |
M |
H |
Fresh |
Silage |
P (1) |
P(2) |
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Mortality |
93 |
95 |
89 |
96 |
93 |
94 |
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Carcass |
78.0 |
77.7 |
77.0 |
75.8 |
76.4 |
77.3 |
0.70 |
* |
NS |
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Breast muscle |
18.5 |
17.7 |
17.5 |
17.3 |
17.4 |
17.6 |
0.43 |
NS |
NS |
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Leg muscle |
18.7 |
18.5 |
17.5 |
17.2 |
17.9 |
17.5 |
0.42 |
NS |
NS |
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Abdominal fat |
1.62 |
1.53 |
1.35 |
1.38 |
1.47 |
1.38 |
0.07 |
NS |
NS |
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DM |
22.1 |
21.7 |
21.9 |
22.1 |
21.9 |
21.9 |
0.25 |
NS |
NS |
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CP |
19.4 |
18.9 |
19.2 |
19.3 |
19.2 |
19.2 |
0.22 |
NS |
NS |
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EE |
1.10 |
1.01 |
1.08 |
1.05 |
1.05 |
1.05 |
0.09 |
NS |
NS |
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Within a row, the mean values with different superscript letters are significantly different (P<0.05) *See footnote in table 2; P (1): P value included control diet, P (2): P value excluded control diet; NS is none significant; DM, CP and EE is dry matter, crude protein and ether extract in leg muscle, respectively |
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As expected, there was no significant effect of processing
of CReM on carcass characteristics of broilers after 56 days of feeding.
However, the level of CReM in the diet had a significantly negative effect on
carcass percentage (relative to live body weight), due to an increase of the
weight of the gastrointestinal tract (GIT), and digesta weight in the chickens
on the high fibre diet also increased as a result of the high water holding
capacity property of fibre. The increase in mass weight of GIT and digesta
weight in broilers given high fibre diets has been documented in several reports
(Jorgensen et al, 1996; Hetland and Svihus, 2001; Borin et al, 2006). There was
a tendency towards decreased breast, leg muscle and abdominal fat weight as a
proportion of carcass weight in diets with CReM, particularly diet H. This could
be due to a decrease in nitrogen and energy retention in the broilers fed high
levels of CReM. These results are in agreement with the findings of Dong (2005)
that carcass traits of duck broilers were negatively correlated to replacement
level of concentrate feed by brewer’s grain.
Both fresh and ensiled cassava residue meals can be included in broiler diets from 4 to 12 weeks old
Supplementation of CReM up to 15% in growing diets and 20% in finishing diets did not affect growth performance and feed conversion ratio of Luong phuong broilers
Supplementation of CReM up to 20% in growing diets and 25% in finishing diets resulted in the highest economic efficiency but reduced growth performance and carcass traits.
From the results of this study, it is recommended that under small-farm conditions, cassava residue can be processed by sun-drying, before or after ensiling, without any effect on the performance and feed utilization of growing-finishing broilers. The most suitable level of supplementation is 15% in growing diets and 20% in finishing diets.
Acknowledgements
The authors would like to thank the Swedish International Development Co-operation Agency (Sida-SAREC) through the MEKARN project for financial support of this study.
References
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