Taro (Colocacia esculenta) silage and water spinach as supplements on rice bran for digestibility of crossbred pigs
 

Nguyen Tuyet Giang

An Giang University (AGU)
Angiang Province, Vietnam
ntgiang@agu.edu.vn

Introduction

Livestock production is making an important contribution to global food supply. We also have to cope with the considerable and increasing demand of finding new feed sources for animals. Many recent researches have been conducted with the purpose of utilizing the local feed resources and by-products of agriculture.

Water spinach (Ipomonea aquatica) can grow easily not only in soil but also in water (pond or river). It is planted for traditionally consumed in South East Asia and appears to be devoid of non-nutritional elements ( Malavanh Chittavong 2006). It was reported that in the fresh leaves and stem of water spinach contain 28% cruide protein of DM. Chopped water spinach can replace 30% of DM on concentrate diet for gestating sows and 15% of diet for lactating sows in both  Ba Xuyen  and exotic breeds, resulting the improvement of reproductive performance and welfare (Men et al 2000).

In many tropical countries, Taro (Colocasia esculenta) is known as a wet-land plant which is cultivated mainly for corm production. In the Southern part of Vietnam, although Taro is grown everywhere, farmers normally harvest the corm, the rest of this plant (leaves and petioles) is not used.  Some studies report the nutritive value of Taro and that the plants can be used for feeding animals ( Pheng Buntha 2006; Chhay Ty 2007; Malavanh Chittavong 2006). The leaves have high crude protein content (26.3% of dry matter) (Chhay Ty 2007). The dried and ground Taro root has also been used as a feed for poultry; without toxic effects observed, but at high levels growth was poor (AFRIS 2004). Calcium oxalate crystals, a substance presenting in all parts of this plant, have an effect on digestive tract by irritating the throat and mouth epithelium (Miller 1929). In order to reduce the concentrate of calcium oxalate present in taro plants, commonly, people cook the corm before eating. According to Pheng Bunta (2007), beside the corm, the leaves and petioles of the taro plant are easy to ensile with palm syrup (soluble sugars). Malavanh et al (2006) also reported good silage quality when using 4% molasses to ensile Taro leaves.

Hypothesis

Apparent digestibility of DM and crude protein, and the N retention, will be improved when Taro silage replaces part of the water spinach, as protein source for growing pigs fed a basal diet of rice bran.

Objectives

This experiment was carried out to investigate the effect on intake, digestibility and N retention of using silage made from Taro leaves and petioles, as partial replacement for water spinach, in a basal diet of rice bran for growing pigs.

Materials and methods

Location and duration

The experiment was conducted in the experimental area of Kampong Cham National School of Agriculture in Kampong Cham province, about 129km from Phnom Penh. Kampong Cham has a tropical climate with an annual monsoon season from May to November. The monsoon is heaviest in late July and August. The climate is most pleasant during the dry season which is from November to April. The annual temperature is around 25 degree Celsius with maximum temperature  known to hit 32 degrees, minimum temperatures rarely fall below 10°C.

The experiment will be carried out from 4^th August to 16^th September 2008.

Experiment design

The experiment will be carried out as a Latin Square 3 x 3 arrangement with 3 pigs and 3 periods, each of 8 days. The treatments are supplements to the basal diet of rice bran (Photos 1-4) as follows:

• WS: Only water spinach

• TS: Taro leaf and petiole silage

• WS-TS: Mixture of water spinach and Taro silage

The adaptation first is 7 days before the animal are fed with the experimental diets corresponding to Period 1 (Table 1).

The feed fomula of the experiment is presented in table 2 below:

Animals and housing

There are three crossbred castrated male pigs, with initial live weights of 10.0 ± 2.5 kg. They are kept in metabolism cages (0.66cm x 0.63cm x 0.60cm) made of wood and designed to separately collect daily faeces and urine.

Feeds and feeding

Taro leaves and petioles were harvested, dried for 24 hours then chopped and ensiled. This procedure has been shown to reduce the content of calcium oxalate (Pheng Buntha, 2007). The ensiled taro was stored in sealed plastic containers for 30 days before being used. Water spinach was bought from the farmers and chopped into small pieces (3-5cm). Rice bran was purchased from Kampong Cham market.

The pigs will be fed three times per day (in the morning, at noon and in the afternoon). The feed components are supplied separately and fed at a level equivalent to 4% of the live weight (DM basis). The quantities of feeds are adjusted slightly to minimize residues. Water is supplied through nipple drinkers.

Measurements and data collection

Feeds offered and residues, faeces and urine will be  recorded daily during the last 5 days of each period. Urine will be collected in a plastic bucket to which sulphuric acid will be added to maintain the pH below 4.0 (10ml of a solution of 10% concentrated sulphuric acid). The volume of urine will be measured every day and 10% of the total volume stored until the end of each period, when it is analysed for N.

The pigs will be  weighed in the morning before feeding at the beginning and the end of each period. Feed samples and residues and faeces will be analysed for DM and CP after every period.

Chemical analysis

Feed and faecal samples will be dried by microwave radiation to measure the DM content (Undersander et al 1993). Total N and the organic matter of samples (feed, faeces and urine) will be according to the AOAC (1990) recommendations.

Statistical analysis

The data will be analyzed by the GLM option in the ANOVA software of MINITAB (release 13.31) (Minitab 2003).

References

AOAC 1990 Official methods of analysis. Association of Official Analytical Chemists, Arlington, Virginia, 15^th edition, 1298 pp.

Buntha P, Borin K, Preston T R and Ogle B 2008  Effect of Taro (Colocasia esculenta) leaf silage as replacement for fish meal on feed intake and growth performance of crossbred pigs.  Livestock Research for Rural Development. Volume 20, Article #5. http://www.cipav.org.co/lrrd/lrrd20/supplement/bunt3.htm

Chhay Ty, Borin K, Preston T R and Mea Sokveasna 2007 Intake, digestibility and N retention by growing pigs fed ensiled or dried Taro (Colocasia esculenta) leaves as the protein supplement in basal diets of rice bran/broken rice or rice bran/cassava root meal. Livestock Research for Rural Development. Volume 19, Article #137. http://www.cipav.org.co/lrrd/lrrd19/9/chha19137.htm

Men L T, Ogle B and Son V V 2000Evaluation of water spinach as a protein source for BaXuyen and Large White sows. Workshop-Seminar on Making Better Use of Local Feed Resources. SAREC-UAF, January 2000. http://www.mekarn.org/sarpro/lemen.htm

Malavanh C, Preston T R and Ogle B 2008  Effect of replacing soybean meal by a mixture of taro leaf silage and water spinach on reproduction and piglet performance in Mong Cai gilts.  Livestock Research for Rural Development. Volume 20, Article #16. http://www.cipav.org.co/lrrd/lrrd20/supplement/mala2.htm

Pheng Buntha, Khieu Borin, T R Preston and B Ogle 2006 Digestibility and nitrogen balance studies in pigs fed diets with ensiled taro (Colocasia esculenta) leaves as replacement for fish meal. Livestock Research for Rural Development. Volume 20, Article # 4. http://www.cipav.org.co/lrrd/lrrd19/9/chha19137.htm

Preston T R 2006  Forages as protein sources for pigs in the tropics. Workshop-seminar on Forages for Pigs and Rabbits MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August 2006. http://www.mekarn.org/proprf/preston.htm

Undersander D, Mertens D R and Theix N 1993 Forage analysis procedures. National Forage Testing Association. Omaha pp 154

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