Study on the processing and use of Alocasia macrorrhiza (Giant taro) leaves in diets for Mong Cai sows and crossbred F1 (Large White x Mong Cai) growing pigs under mountainous village conditions

Pham Sy Tiep, Nguyen Van Luc, Nguyen Manh Hung^*, Tran Van Tu^* and Tran Van Phung^**

NIAH, Hanoi
phsytiep@yahoo.com
 ^* Department of Agriculture and Rural Development, Dinh Hoa, Thai Nguyen
^** Thai Nguyen University, Vietnam

 

Abstract

Three experiments were carried out in Cho Chu village, Dinh hoa district, Thai Nguyen province with the aim of determining the best ensiling method for leaves of Alocasia macrorrhiza (AL) and the best rate of using the ensiled AL in the diet of Mong Cai sows and growing pigs in mountainous household condition. In experiment 1, six treatments were compared, corresponding to 3 species of Alocasia macrorrhiza, each ensiled with 4% rice bran or 4% molasses. Each treatment was replicated 4 times to facilitate analysis after 0, 7, 14 and 21 days of ensiling. In experiment 2, there were 10 dry Mong Cai sows with similar age and body weight randomly allocated into 5 households. In each household there were 2 sows which were kept individually in pens. One of them was fed the control diet; the other was fed the experimental diet with ensiled AL (EAL). The duration of the  experiment was 155 days. In the third experiment,: sixteen crossbred F1 (Y x MC) growing pigs (equal numbers male and female) from the sows in experiment 2 with average initial body weight of 15 ± 1.0 kg were allocated at random, balanced for sex, to 2 households with 8 pigs in each. In each household, the pigs were housed in 4 separate pens, each with 2 pigs (1 castrated male + 1 female). The EAL was prepared as in experiment 1. The diets contained ensiled Alocacia leaves at 0, 10, 20 and 30% of the diet DM.

There were no differences in pH and nutritive value among the three species of Alocasia macrorrhiza leaves after ensiling with 4% rice bran or 4% molasses. After ensiling, the calcium oxalate was reduced by 69.1 to 78.5% and the pH maintained at 4.10 to 4.22 until the 21^st day,  There were no negative effects on the performance of the pigs and benefits for the farmers were higher using 18 to 25% of EAL for MC sows and 20% EAL (replacing fish and soybean meal) for crossbred (Y x MC) growing pigs.

Key words: Calcium oxalate, ensiling, ethnic minority, farmer households, molasses, rice bran,

Introduction

More efficient use of local feed resources and improving the economical benefit of pig producers is a major challenge in the northern mountainous areas of Vietnam. Alocasia macrorrhiza (AM) is a kind of wild tree found on the slopes of mountains. Today it is also commonly planted in the gardens around the houses in the mountainous area. The yield of fresh AM root is on average 16 tonnes per ha and the leaves are available all year round with a production on a fresh basis of over 10 tonnes per ha, in 2 to 3 harvests.

There are 3 species of Alocasia macrorrhiza in Vietnam’s northern mountainous areas. Wild AM usually grows on stony mountain slopes. It has very large and thick leaves, and the stems and leaves are dark green in color. The leaves are very itchy and used only in traditional medicine. Wavy AM (or elephant ear Alocasia macrorrhiza) usually grows beside streams or in wet places; it has large, wavy leaves. The stems and leaves are green in color, always cause itching and are sometimes used for feeding pigs. Finally, White Alocasia macrorrhiza (or “khoai ray”) usually grows in terraced fields or is planted in the gardens around the houses. Its stems and leaves are light green in color and are less itchy than the two previous kinds. The nutritive value of taro leaves is considered to be similar to that of sweet potato vines (Gerpacio and Castillo 1998). Analytical data from Nigeria and Vietnam show the crude protein content and ash contents to be high, while crude fibre appears to be quite low (Table 1).

Ethnic minority people in the northern mountainous areas have traditionally used Alocasia macrorrhiza leaves (AL) for feeding pigs. But the rate of inclusion of AL in the ration was very limited because the farmers had to spend too long a time for cooking the leaves to destroy the factor (now known to be calcium oxalate), which results in itching when the fresh AL are fed. Pham Sy Tiep et al (2004, 2005) carried out a study on the processing and use of Alocasia macrorrhiza roots for pigs. The results showed that the calcium oxalate content could be reduced by chopping and soaking in 0.5% NaOH, which disrupted the cellular structure of the root. After processing, the Alocasia macrorrhiza root meal could be used at up to 50% in the diet for growing pigs.

 The purpose of this study was to:

• Determine the best ensiling method to reduce calcium oxalate content and maintain the nutritive value of Alocasia macrorrhiza leaves.

• Evaluate ensiled Alocasia macrorrhiza leaves as a protein source to replace the soybean and fish meal in the diets of Mong Cai (MC) sows and crossbred F1 (Yorkshire x MC) growing pigs in mountainous household conditions.

Materials and methods

Three experiments were carried out:

Experiment 1: Study on ensiling giant taro (Alocasia macrorrhiza) leaves with rice bran or molasses

The experiment was conducted in households in Cho Chu Village, Dinh Hoa District, Thai Nguyen Province between August and October 2006.

Treatments and design

The leaves were from 3 species of Alocasia macrorrhiza, each ensiled with rice bran or molasses:

• Wild Alocasia macrorrhiza + 4% rice bran (WiR)

• Wild Alocasia macrorrhiza  + 4% molasses (WiM)

• Wavy Alocasia macrorrhiza  + 4% rice bran (WaR)

• Wavy Alocasia macrorrhiza  + 4% molasses (WaM)

• White Alocasia macrorrhiza  + 4% rice bran (WhR)

• White Alocasia macrorrhiza  + 4% molasses (WhM)

Ensiling procedure and analyses

The Alocasia macrorrhiza leaves (only the young leaves were used) were chopped into small pieces 2 - 3 cm in length and sun-dried for 1 -2 hours, then mixed with 4% of rice bran or 4% of molasses (on DM basis). The ingredients were mixed thoroughly and kept in plastic bags, tied tightly to maintain anaerobic conditions, and stored at room temperature (25 - 35^oC).  There were 4 bags for each treatment which were sampled for analysis of the contents at 0, 7, 14 and 21 days. Determinations were made of calcium oxalate, pH, total N and ammonia-N, also perceptible characteristics such as color, smell, and itching intensity of the leaves before and after processing. 

Experiment 2: Effects of including ensiled Alocasia macrorrhiza leaves (EAL) in the diets of Mong Cai sows

The experiment was conducted in households in Cho Chu Village, Dinh Hoa District, Thai Nguyen Province between November 2006 and April 2007. Mong Cai sows (n=12) of similar age and body weight were selected 3-4 days after weaning their piglets. They were randomly allocated into 5 households in Cho Chu village. In each household there were 2 sows kept in individual pens. One sow was fed the control diet, the other received the experimental diet (AM). The duration of the experiment was 155 days, from 3-4 days after weaning to weaning of the piglets of the following litter. Wavy Alocasia macrorrhiza leaves were chopped into small pieces about 2-3 cm long, wilted overnight and mixed with 4% rice bran and 1% NaCl. The mixtures were kept in plastic bags with a capacity of 30 to 40 kg, pressed under airtight conditions and stored for 3 weeks before use. The sow diets consisted of maize, rice bran, fish meal, ensiled Alocasia macrorrhiza leaves, limestone, premix and NaCl (Table 2).  In the WaL diet the ensiled leaves replaced 50% of the protein from fish meal (Table 3).

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During the experimental period all the diets were given ad libitum in two meals per day. The feeds were mixed immediately before feeding them to the sows. Feed offered and feed refusals were recorded daily. At the beginning and at the end of the experiment (from 10 days before farrowing to the day after weaning the piglets), the sows were weighed in the morning before feeding. Piglets were weighed at birth, at weaning and at 56 days.

Measurements included daily feed intake, number of piglets (born alive, at weaning at 35 days and at 60 days), weight of piglets (born alive, at weaning and at 56 days), loss in weight of sows and feed costs for production of 1 kg piglets at 60 days.

The data were analyzed using the GLM procedure in MINITAB program 11.2.

Experiment 3: Effects of including ensiled Alocasia macrorrhiza leaves (EAL) in the diets of crossbred F1 (LW x MC) growing pigs

The experiment was conducted in farmer households in Cho Chu Village, Dinh Hoa District, Thai Nguyen Province between April and June 2007. Sixteen crossbred F1 (Yorkshire x Mong cai) pigs (8 males and 8 females) from the sows in Experiment 2 with average initial body weight of 15 ± 1.0 kg (two months of age) were ear-notched and allocated at random, balanced for sex, into 2 households with 8 pigs in each. In each household, the pigs were divided into 4 pens (3 pens for the experimental diets and one for control). Each pen consisted of 2 pigs (1 castrated male + 1 female) and households were replicates.

The ensiled Alocasia macrorrhiza leaves were prepared as in Experiment 1 using rice bran as additive. The pigs in the control pen were fed a basal diet consisting of maize, rice bran, fish meal, limestone, premix and NaCl. Ensiled Alocasia macrorrhiza leaves were included at 0, 10, 20 and 30% of the diet DM (Table 4).

The pigs were fed ad libitum during the experimental period. Drinking water was freely available from automatic drinkers. Daily feed intake, average daily gain (ADG) and feed conversion ratio (FCR) were determined.  Observations on health, the dressing percentage, quality of the meat in terms of color, smell, taste and chemical composition were determined and economical efficiency calculated.

During the experimental period all the diets were given ad libitum 2 times per day. The feed was mixed immediately before feeding it to the pigs. Feed offered and feed refusals were recorded daily. At the beginning and at the end of the experimental period the pigs were weighed in the morning before feeding.

The data were analyzed using the GLM procedure in MINITAB program 11.2. Source of variation in the model were treatments, sex and error.

Results and discussion

Effect of additives on the composition of the AL silage

The pH in the leaves ensiled with 4% molasses decreased rapidly during the first week and then fell further to 4.01-4.05 after 60 days (Table 5). In AL ensiled with 4% rice bran the pH decreased up to day 14 after ensiling then remained stable until 21 days with slightly higher values (pH  4.26 - 4.42) compared with use of molasses. There were no differences among species of Alocacia. These results are similar to those reported by Chittavong Malavanh et al (2007) when leaves of Colocacia esculenta were ensiled with molasses.   

The differences in the crude protein of the leaves before and after ensiling (Table 6) reflect the differences in the protein content of the two additives (higher in rice bran than in molasses, and both less than in AL). Crude protein content was similar in the three varieties of Alocacia.  Ensiling with either additive reduced the content of calcium oxalate by 69 – 78% with the effect more pronounced for varieties WaL and WhL. The colour, taste and smell of the silage was best for the WaL leaves ensiled with rice bran. This treatment was therefore selected for the feeding trials.

Ensiled Alocasia macrorrhiza leaves (EAL) in diets for Mong Cai sows

There were no difference between the control and experimental treatments in all the criteria concerned with reproductive performance (Table 7). The feed cost to 1 kg of piglets at 60 days was 9.2% in the WaL treatment.

Ensiled Alocasia macrorrhiza leaves (EAL) in the diets of crossbred F1 (LW x MC) growing pigs

Pigs on the control (EAL0) and EAL10 treatments had higher live weight gain than those fed diets EAL20 and EAL30 (Table 8). However, feed costs were some 20% lower for the EAL20 and EAL30 treatments compared with the control.
 

From these results it can be concluded that if the farmers can ensile Alocasia macrorrhiza leaves, they can save on feed costs and get higher economic benefits. Although labor costs were not included it is assumed that the opportunity cost of labor is very low in the village situation. .   

Conclusions

·        Ensiling Alocasia macrorrhiza leaves with 4% rice bran or 4% molasses reduced calcium oxalate levels by about 70% and maintained the pH at around 4.  The rice bran additive gave a slower fermentation, and supported a higher pH at 21days after ensiling compared to the molasses treatment.

·        Including ensiled Alocasia macrorrhiza leaves at 18-25% in the diet of Mong cai sows had no effects on reproductive performance but gave higher benefits for the farmers under mountainous village conditions in Northern Vietnam.

·        Using 20 or 30% ensiled Alocasia macrorrhiza leaves in the diet of F1 (Yorkshire x Mong cai) growing pigs reduced slightly the growth rate but economic benefits were higher.

References

Chittavong Malavanh , Preston T R and Ogle B 2008: Ensiling leaves of Taro (Colocasia esculenta (L.) Shott) with sugar cane molasses.  Livestock Research for Rural Development. Volume 20, supplement. http://www.cipav.org.co/lrrd/lrrd20/supplement/mala1.htm

Gerpacio A L and Castillo L S 1998. Nutrient composition of some Philippines feedstuffs. Los Banos, 12-24pp.

NIAH 2001  Composition and nutritive value of animal feeds in Vietnam. Agricultural Publishing House, Hanoi.

Pham Sy Tiep, Nguyen Van Luc and Dang Hoang Bien 2005: Processing and use of Alocasia macrorrhiza (taro) roots for fattening pigs under mountainous village conditions;  Workshop-seminar "Making better  use of local feed resources" (Editors: Reg Preston and Brian Ogle) MEKARN-CTU, Cantho, 23-25 May, 2005. Article #44. RetrievedJune 14, 108, from http://www.mekarn.org/proctu/tiep44.htm

Pham Sy Tiep, Nguyen Van Luc, Trinh Quang Tuyen, Nguyen Manh Hung and Tran Van Tu 2006: Study on the use of Alocasiamacrorrhiza(roots and leaves) in diets for crossbred growing pigs under mountainous village conditions in northern Vietnam. Workshop-seminar "Forages for Pigs and Rabbits" MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August,  2006. Article # 11. RetrievedJune 14, 108, from http://www.mekarn.org/proprf/tiep.htm

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