Taro (Colocasia esculenta (L) Schott): biomass yield and nutritive value for pigs

D T Hang, T T X An¹, L Thuong, N T Loc, V V Hai, T T T Tra, P V Hai and L D Ngoan

Faculty of Animal Husbandry and Veterinary Medicine, Hue University of Agriculture and Forestry, Hue City, Viet Nam.
¹ Faculty of Crop Production, Hue University of Agriculture and Forestry, Hue City, Viet Nam.

Abstract

The biomass yield of two varieties of Taro grown in the sandy or clay soils of Huong Chu village was studied. The varieties were: Ao Trang (Colocasia esculenta (L) Schott (Green Stem) and Mon Ngot (Colocasia esculenta (L) Schott (dark brown dot in leaves).

Ao Trang and Mon Ngot varieties were estimated to produce from 220 to 244 tonnes/ha/year, providing 12 tonnes DM and 2.4-2.5 tonnes CP/ha/year.  Fresh biomass yield of Taro was the same in sandy or clay soil. The high apparent digestibility of cell wall components in diets with 50% ensiled leaves or petioles indicate that the Taro plant can be used as a major ingredient in diets for growing pigs.

Keywords: digestibility, harvest interval, leaves, petioles, silage

Introduction

In Central Viet Nam, many smallholders are located in areas where soils have a high content of sand or clay. The staple crops are sweet potato and cassava but the farmers produce also Taro (Colocia esculenta) for animal feed , mainly for pigs. Two varieties of Taro are commonly cultivated in these soils, the Mon Ngot (Colocasia esculenta (L) Schott) characterized by a brown dot in the middle of the leaf and the Ao Trang ( Colocasia esculenta (L)) Schott with green stem. These varieties are grown for harvesting of petioles and leaves but not for tubers.

The objective of this study was to determine the biomass yield and the nutritional value of Mon Ngot and Ao Trang varieties, grown in the clay or sandy soil of Central Vietnam.

Materials and methods

Location

The experiment was carried out in Huong Chu village, Huong Tra district of Thua Thien Hue province. The two varieties were grown in areas with clay or sandy soil. The plants were arranged in 12 rectangular plots measuring 2.5 x 4 m each one, with 3 replications for each variety in each type of soil. The total experimental area was 120 m².

Procedure

Experiment 1

The varieties were planted at a distance of 20 cm between plants and 60 cm between rows. Before planting, pig manure was applied at 150 kg/ha together with 8 kg/ha of NPK (15.15.15). After each harvest a further application of pig  manure was applied (300 kg/ha), The first harvest was made 60 days after planting, with subsequent harvesting at intervals of 14 days. The whole plant was harvested just leaving one or two veery green buds. Leaves and petioles were then weighed separately. At each harvest, samples of the leaves and petioles of each species were analysed for DM, crude protein, NDF, ADF and crude fibre (CF). Analytical methods for DM, CP and CF were according to AOAC (2002); and for NDF and ADF according to Van Soest et al (1991).

Experiment 2:

Eight 16-weeks old crossbred (Large White x Mong Cai) castrated male pigs (LW 45±2.55kg) were housed individually in metabolism cages, and fed in consecutive periods diets with 50% of the DM as ensiled taro leaves or 50% of DM as ensiled taro petioles (Table 1). In each case the silages were made with addition of 5% molasses (on fresh basis).  In each period, there were 7 days for adaptation to the diet followed by 5 days for collection of feces and urine. Feces were collected four times per day and stored at -20ºC. Urine was collected in a bucket via a funnel below the cage. To prevent nitrogen losses the pH was kept below 4 by adding 50ml of 25% sulphuric acid in the collection bucket.

Statistical analysis

The data were analysed using the general linear model (GLM) in the ANOVA program of the Minitab (2010) software. In experiment 1, sources of variation were varieties, soil type, interaction varieties*soil and error; in experiment 2, sources of variation were diet and error.

Results and discussion

Biomass yields tended to increase with consecutive dates of harvesting (Table 2). The DM content of leaves and petioles increased, but the content of crude protein decreased, with date of harvest. There were no consistent effects of harvest date on composition of NDF and ADF.

Assuming that the harvests would continue through the year, then the fresh biomass yield of both varieties was  predicted to be between 220 and 244 tonnes/ha/year and of crude protein (CP) to be 2.4 to 2.5 tonnes (Table 3).

Taro cultivated on clay soils had the higher biomass  yield and protein content compared with taro grown on sandy soils (Table 4).

The apparent digestibility coefficients of all proximate components of the diet were high with indications of slightly lower values for diets with taro petioles as compared with leaves (Table 5)

Conclusions

• Ao Trang and Mon Ngot varieties were estimated to produce from 220 to 244 tonnes/ha/year, providing 12 tonnes DM and 2.4-2.5 tonnes CP/ha/year.
  
  
• Fresh biomass yield of Taro was the same in sandy or clay soil
  
  
• The high apparent digestibility of cell wall components in diets with 50% ensiled leaves or petioles indicate that the Taro can be used as a major ingredient in diets for growing pigs

Acknowledgments

The authors would like to thank the Vietnam National Foundation for Science and Technology Development (NAFOSTED) (Grant number 106-NN.05-2013.31), for the funding of this research.

References

AOAC 2002 Official methods of analysis of AOAC International. 17th edition. 1st revision. Gaithersburg, MD, USA, Association of Analytical Communities.

Le Van An, Tran Thi Thu Hong and Lindberg J E 2004 Ileal and total tract digestibility in growing pigs fed cassava root meal diets with inclusion of fresh, dry and ensiled sweet potato leaves. Animal Feed Science and Technology 114, 127-139

Minitab 2010 Minitab user's guide. Data analysis and quality tools. Release 16 for Windows. Minitab Inc., Pennsylvania, USA.

 Van Soest P J, Robertson J B and Lewis B A 1991  Methods for dietary fiber, neutral detergent fiber, and nonstarch polysaccharides in relation to animal nutrition. Journal of Dairy Science 74: 3583-3597.

Received 15 April 2015; Accepted 28 May 2015; Published 3 June 2015

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