|
|
|
|
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Figure 1a. New Cocoyam or Giant Taro (Xanthosoma sagittifolium) |
|
Figure 1b:
Old cocoyam or Taro |
According to Wang (1983), Taro has great potential as animal feed in the tropics and subtropics where it is often a staple food for pigs. However, because of the problem of the presence of calcium oxalate, the leaves, petioles and corms of Taro are often considered unacceptable for direct use as an animal feed (Jiang Gaosong et al 1996). Wang (1983) claimed that this problem could be solved by the fermentation occurring during the process of ensiling. This has been confirmed recently by Chittavong Malavanh et al (2007), who successfully fed ensiled Taro leaves to pigs during reproduction and lactation, and by Peng Buntha et al (2007) and Chhay Ty et al (2007) who fed ensiled and dried leaves of Taro to growing pigs.
In the Central region in Vietnam, Taro is very easy to grow, naturally or by planting. Some Taro varieties are used only for pigs; some are harvested to produce roots for human consumption while the petiole and leaves have been used as by-product feeds for pigs. Farmers have experience in feeding their pigs with several kinds of Taro but without any information about their composition or nutrient value. Until now, there are no research results recorded about what kinds of Taro are used for pigs, their biomass production, seasonal availability, composition and nutrient content; or how to use better these resources in pig diets.
The aim of this research was: i) to identify: species of Taro popularly used by farmers; ii) their characteristics including biomass productivity, seasonal availability, variation between years, and nutritive value; and iii) how to make better use of this local feed resource for pig production
Materials and Methods
Compilation of information on Taro
A survey was conducted in three areas in Hue province (upland, flat land and coastal area). One commune per area was selected for investigation (Hong Ha commune in the upland area, Thuy Duong commune in the flat land, and Phu Da commune in the coastal area). Interviews were arranged with 150 households (about 25% of the total of pig raisers in each commune) to understand which species of Taro the farmers commonly used for pig feeding, and their characteristics such as seasonal availability, adoptability during the year and what parts of Taro could be used to feed pigs.
Staff of the Department of Agriculture and Rural Development (DARD) and Grass roots extension workers working closely with pig raisers in the targeted areas were also interviewed to collect data and relevant information. Some tools introduced in Rapid Appraisal Approach were time-lining analysis, scale games and questionnaires (Mikkelson 1994).
Identification of seasonal biomass and its chemical composition
Based in the information compiled on Taro, a trial was planned to determine biomass yield of Taro species used for pigs in the dry and wet seasons and their re-growth capacity after cutting. Samples of leaves, petioles and corms were collected and analyzed for their chemical composition (DM, CP, CF and Ash) according to AOAC (1990).
The experiment was a completely randomized blocks (RCB) design with 5 treatments (species of Taro used popularly) and 3 replications. The suckers taken from the roots were planted with a density of 60,000 – 65,000 plants per ha (35 cm between plants in the row and 45 cm between rows). Fertilization rates (per ha) were 10 tonnes of composted pig manure, 200 kg urea, 30 kg P2O5 and 30 kg K2O. All the manure, the P2O5 and one third of the amount of urea and K2O were applied during the period of land preparation. One third of the total amount of urea and K2O were applied along with weeding when all the Taro had germinated. The remaining urea and K2O were applied after 50 to 60 days when the Taro was harvested the first time. (Hoanh Mai Thach and Vinh Nguyen Cong 2003).
Better use of Taro for pig raising
A feeding experiment was conducted in Thuy Duong Farm to measure feed intake and performance of pigs fed diets containing Taro processed in three different ways. Crossbred pigs (Yorkshire x Mong Cai; 6 female and 6 castrated males) at 2 months old with an average initial live weight of 11.4 kg were used. They were vaccinated against hog Cholera and Pasteurellosis, and de-wormed 2 weeks before starting the experiment, which was a completely randomized design with 3 treatments and 4 replications. The pigs were housed in individual pens and fed diets containing Taro leaves and petioles in fresh form (FL), cooked (CL), or ensiled (SL) form. The Taro foliage (leaves and petioles) were the protein supplements to a basal diet of rice bran and ensiled cassava root (2:1 ratio in DM) and 5% of groundnut cake. The basal diet containing 12% crude protein in DM was fed at around 2% of live weight (DM basis) while the Taro leaves and petioles were fed ad libitum (about 20% above recorded intake) .
The Taro leaves and petioles (Colocasia esculenta (L.) Schott, green stem) were chopped into small pieces, after which a part was used immediately to feed the pigs in treatment FL. Another part was cooked for 15 minutes to feed pigs in treatment CL. The Taro silage was made by using chopped Taro leaves and petioles with rice bran at 5% (fresh basis) as additive. The mixture was placed into plastic bags with a volume of 40 litres, which were then sealed to maintain anaerobic conditions. The bags were stored at room temperature (27-33oC) and the ensiled material used for pigs in treatment SL after 3 weeks ensiling.
Live weight (10 day intervals) of the pigs and daily feed intake were recorded.
The general linear model (GLM) of Minitab Version 13
(2000) was used to analyze the data. Results are presented as least squares
means with the pooled standard error of the means. Sources of variation were:
treatments and error.
Results and Discussion
Compilation of information on Taro
Eight species of Taro were found in the targeted areas of which 5 were planted traditionally (Table 1). In the upland area the “wild” Taro was growing naturally, while in the lowland and coastal areas it was planted.
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Table 1. Taro species found and planting rate of interviewed farmers in the targeted areas (%) |
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|
Vietnamese name |
Latin name |
Upland n=30* |
Flat land n= 60* |
Coastal n=60* |
|
Mon Nuoc |
Colocasia esculenta (L) Schott (Green stem) |
20.0 |
100.0 |
100.0 |
|
Mon Chia voi |
Colocasia esculenta (L) Schott (Light Green stem) |
10.0 |
76.7 |
63.3 |
|
Mon Tho (mon do) |
Colocasia esculenta (L) Schott (Red stem) |
16.7 |
86.7 |
70.0 |
|
Mon Bac Ha |
Alocasia odora C. Koch (Green stem) |
20.0 |
83.3 |
88.3 |
|
Mon Moi |
Alocasia odora C. Koch (Red stem) |
3.3 |
25.0 |
33.3 |
|
Mon Chum (mon tim) |
Alocasia odora C. Koch (Purple stem) |
23.3 |
78.3 |
90.0 |
|
Mon sap vang |
Xanthosoma nigra (Vell.) Stellfeld |
0 |
8.3 |
25.0 |
|
Mon rung |
Wild Taro |
100.0 |
- |
- |
|
*. n: number of farmers interviewed in each area |
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Wang et al (1981) reported that Taro is indigenous to the humid tropics and can be grown under flooded or upland conditions. In the targeted areas, Taro was planted at different times based on the species; e.g. Mon Nuoc and Chia Voi were planted throughout the year, Mon Moi and Mon Sap vang were planted in Spring season while Bac Ha, Chum and Tho were planted in Summer season (Table 2).
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Table 2. Crop Seasonal Calendar of Taro planted in targeted areas |
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Vietnamese name |
Latin name |
Planting time |
|
Mon Nuoc |
Colocasia esculenta (L) Schott (Green stem) |
Year round |
|
Mon Chia voi |
Colocasia esculenta (L) Schott (Light Green stem) |
Year round |
|
Mon Tho (mon do) |
Colocasia esculenta (L) Schott (Red stem) |
July |
|
Mon Bac Ha |
Alocasia odora C. Koch (Green stem) |
July |
|
Mon Moi |
Alocasia odora C. Koch (Red stem) |
January |
|
Mon Chum (mon tim) |
Alocasia odora C. Koch (Purple stem) |
July |
|
Mon sap vang |
Xanthosoma nigra (Vell.) Stellfeld |
January - February |
|
Mon rung |
Wild Taro |
- |
Different species of Taro are planted according to intended use. Some (Mon nuoc, Mon chia voi, Mon tho) are to produce stems and leaves, others (Mon sap vang, Mon moi) are mainly to produce root while Mon chum and Bac Ha) are for both purposes. For these reasons, stem and leaves were available throughout the year in the targeted areas. However, there were some differences in availability of Taro stem and leaves used for pig raising between species, duration and ecological zone (Table 3).
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Table 3. Taro availability during the year in targeted areas |
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Months |
Upland |
Flat land |
Coastal |
|
1 |
+++ |
++ |
+++ |
|
2 |
+++ |
+++ |
++++ |
|
3 |
+++ |
+++ |
++++ |
|
4 |
+++ |
+++ |
++++ |
|
5 |
++ |
++ |
+++ |
|
6 |
++ |
++ |
++ |
|
7 |
++ |
+ |
++ |
|
8 |
++ |
+ |
++ |
|
9 |
++ |
+ |
+++ |
|
10 |
+++ |
++ |
++++ |
|
11 |
+++ |
++ |
++++ |
|
12 |
+++ |
++ |
++++ |
|
++++: Plenty; +++: Many; ++: Moderate; +: Few |
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Taro leaves were mainly used for pigs. Taro stems were also used for pigs and some for humans as vegetable. Taro roots were only used for human consumption. Taro stem and leaves were used as main feed source for pig raising in the targeted areas, especially in the upland area where there is a lack of protein sources for pigs. They were fed to pigs daily, every 2 to 3 days or weekly depending on areas planted by each family (in the flat land and coastal areas) and how much Taro leaves and stem could be collected from the forest (in the upland area) (Table 4).
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Table 4. Frequency of use of taro leaves and stems for pig raising (% total interviewed farmers) |
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|
Zone |
Daily |
Every 2-3 days |
Weekly |
|
Upland |
100 |
- |
- |
|
Flat land |
25 |
42 |
33 |
|
Coastal |
100 |
- |
- |
The data showed that 100% of farmers interviewed in the upland area fed their pigs daily with Taro stem and leaves. The farmers collected them in the forest free of charge. The same situation applies in the coastal area but the reason for using Taro was quite different. Taro grows in the coastal area more easily and is more popular than other vegetables, so it is considered as the main feed source for pigs in this region. In the flat land, many vegetables are available for pig raising such as sweet potato leaves, water spinach, duck weed and banana stems. In this region, feeding of Taro leaves and stem was infrequent (Table 4).
Identification of seasonal biomass and its chemical composition
Re-growth capacity of Taro was high (Table 5). It reached the level of 65 - 95% compared to the first harvest depending on species and season as well as harvest times. In the dry season, the re-growth capacity was higher than in the wet season and harvest intervals (30 - 40 days) were also shorter than in the wet season (40 - 50 days).
The highest yield of Taro stem and leaves was with Alocasia odora C. Koch (Green stem) while the lowest was with Alocasia odora C. Koch (purple stem). Within species of Colocasia esculenta (L) Schott, the one with light green stem had the highest biomass yield while the lowest was the one with Green Stem. The biomass yield was strongly affected by season, weather, soil fertility and cultivation methods.
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Table 5. Seasonal biomass yield of Taro species and their re-growth capacity (tonnes fresh matter/ha) |
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|
|
Taro species |
||||
|
CELS* (Green stem) |
CELS (Light Green stem) |
CELS (Red stem) |
AOCK* (Green stem) |
AOCK (Purple stem) |
|
|
Dry season (March - August) |
|||||
|
1st Harvest |
39.3 |
47.0 |
46.0 |
51.3 |
34.0 |
|
2nd Harvest |
34.7 |
42.8 |
40.7 |
43.8 |
32.0 |
|
3rd Harvest |
30.6 |
39.5 |
36.4 |
42.0 |
29.6 |
|
4th Harvest |
28.7 |
36.8 |
34.4 |
38.4 |
26.4 |
|
5th Harvest |
28.2 |
39.0 |
36.0 |
40.6 |
24.0 |
|
Wet season (September - February) |
|||||
|
6th Harvest |
31.2 |
40.6 |
39.5 |
42.4 |
27.8 |
|
7th Harvest |
26.9 |
36.0 |
34.0 |
38.0 |
26.0 |
|
8th Harvest |
25.4 |
34.6 |
32.6 |
35.6 |
23.2 |
|
9th Harvest |
27.9 |
38.4 |
35.8 |
39.3 |
24.6 |
|
Total |
273d |
355b |
335c |
373a |
248e |
|
*CELS: Colocasia esculenta (L) Schott; AOCK: Alocasia odora C. Koch a,b,c,d,e Means with different superscripts within rows differ at P<0.05 |
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The taro leaf, like most higher plant leaves, is rich in protein and ash (Table 6). According to Inno Onwueme (1999), it is also a rich source of calcium, phosphorus, iron, vitamin C, thiamine, riboflavin and niacin, which are important constituents of the human diet.
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Table 6. The composition of different species of Taro (leaves combined with stems) |
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|
|
Taro’s species |
||||
|
CE(L)S (Green stem) |
CE(L)S (Light Green stem) |
CE(L)S (Red stem) |
AOCK (Green stem) |
AOCK (Purple stem) |
|
|
DM, % |
7.43 |
8.05 |
6.98 |
7.48 |
7.36 |
|
% in DM |
|||||
|
Crude protein |
17.5 |
16.5 |
18.2 |
17.9 |
17.4 |
|
Crude fibre |
16.9 |
21.7 |
18.2 |
20.6 |
17.8 |
|
Ash |
15.9 |
16.5 |
17.0 |
17.2 |
15.4 |
Pig performance
The Taro leaves and stems provided about 20% of the diet DM (Figure 2) and about 25% of the dietary crude protein (Figure 3). Groundnut cake supplied about 15% of the crude protein, with the major proportion coming from rice bran.
 |
 |
| Figure 2. Proportions of feed ingredients in the diet DM | Figure 3. Proportions of dietary crude protein from feed ingredients |
Feed intake, rate of live weight gain and feed conversion were best when the combined Taro leaves and stems were ensiled (Table 7). Poorest responses were when the Taro leaves and stem were fed fresh, with intermediate values for processing by cooking . The improvement due to ensiling and cooking is in agreement with the findings of Du Thanh Hang and Preston (2007) who fed leaves of Colocacia esculenta to growing pigs and reported higher values for N retention when the leaves were cooked or ensiled compared with feeding them fresh.
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Table 7. Mean values for feed intake, live weight at slaughter, feed conversion rate and carcass lean percentage in pigs fed Taro leaves and stems in fresh form (FL), cooked (CL) or ensiled (SL) |
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|
|
Treatments |
|
||
|
FL |
CL |
SL |
Probability | |
|
Initial live weight, kg |
11.3 |
11.5 |
11.4 |
0.45 |
|
Experiment time, days |
122 |
122 |
122 |
- |
|
Slaughter live weight, kg |
65.3 c |
72.2b |
77.4a |
0.01 |
| Live weight gain, g/day | 443c | 498b | 541a | 0.01 |
|
DM intake, kg/day |
1.52c |
1.58b |
1.66a |
0.04 |
|
DM feed conversion |
3.43a |
3.18b |
3.07c |
0.03 |
|
Lean meat percentage (%) |
46.5b |
48.5a |
46.1b |
0.005 |
|
a,b,c, Means with different superscripts within rows are different at P<0.05 |
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The Taro plant is known to cause itchiness (acridity). According to Lee (No date), the acridity is due to the presence of calcium oxalate crystals and that when these are released they inflict minute punctures on the skin. Pham Sy Tiep et al (2006, 2007) showed that ensiling the leaves and stems of Taro (Alocacia macrorrhiza) reduced the concentration of calcium oxalate from 66-70 to 14-20 mg/kg DM. Presumably, the acridity was the cause of the lower intakes in the present experiment when the Taro leaves and stems (Colocasia esculenta) were fed fresh. However, the degree of acridity appears to vary among different species of Taro. Thus Rodriguez et al (2006) reported that growing pigs fed fresh leaves of Xanthosoma sagittifolium, as replacement for 50% of the soybean meal protein in a diet based on sugar cane juice, grew at the same rate (500 g/day) as pigs fed only soybean as the protein supplement.
Conclusions
-
Taro with 8 species belonged to the sub-family of Colocasiodeae (Alocasia, Colocasia, and Xanthosoma) were available during the year in flat land, upland and coastal areas in Thua Thien Hue, Vietnam.
-
They were planted in flat land and in coastal areas with very high biomass yield and re-growth capacity . In the upland region they were found growing wild.
-
Feed intake, growth rates and feed conversion in crossbred pigs fed Taro leaves and stems were improved when these ingredients were cooked or ensiled, with the latter supporting the best performance.
-
The ensiled foliage (leaves and stems) of Taro species has high potential as a protein source to balance pig diets based on rice byproducts.
Acknowledgements
Financial support from the Swedish International Development Cooperation Agency – Department for Research Cooperation (SIDA/SAREC) is gratefully acknowledged. We would also like to thank Dr. Le Duc Ngoan, Vice Rector of Hue University of Agriculture and Forestry, Vietnam and Dr. Britta Ogle, Uppsala University, Sweden for their valuable advice and comments.
References
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