Taro (Colocacia esculenta) silage and rice bran as the basal diet for growing pigs; effects on intake, digestibility and N retention

Nouphone Manivanh and T R Preston*

Souphanouvong University (SU, Animal department.
Luang Prabang, Lao PDR
nouphone2007@yahoo.com
* Finca Ecológica, TOSOLY, UTA (Colombia)
AA #48, Socorro, Santander, Colombia

Abstract

Four crossbred castrated male pigs, weighing on average 10.5 kg were allotted at random to 4 diets within a 4*4 Latin square design, to study effects of Taro silage (Colocasia esculenta) alone and in combination with rice bran (75:25, 50:50 and 25:75 silage: rice bran) on digestibility and N retention of growing pigs. The trial was conducted in the experimental area of Angang University (AGU), in Angang province, Vietnam,  from 24 August to 16 October, 2010.

Diets with 50% of taro silage plus 50% rice bran (DM basis) supported higher rates of feed intake (49.9 g DM/kg LW/day) than diets with more or less taro silage. Apparent digestibility coefficients of DM, OM  and crude protein were high and tended to increase as the proportion of taro silage in the diet was increased from 25 to 100% (from 85 to 89% for DM and OM and from 81 to 88% for crude protein). N retention was higher with 50% taro silage in the diet than with 25 or 100% with intermediate values for 75% taro silage.  However, when N retention was corrected for differences in DM intake, the highest N retention was on the 100% taro silage diet  with no differences among the diets that contained rice bran.  Urine excretion was increased threefold by raising dietary taro silage intake from 25 to 100% of the diet.

Key words: Diuretic effect, protein, urine volume

Introduction

In most parts of Laos, agricultural by-products, such as rice bran, and natural grasses are the main feeds for liive stock  (ILRI 2002). In Lao villages, where most farmers are growing paddy rice for sale, the feed for pigs is based on rice bran, which is fed together with a small amount of green feed. Thus rice bran is available in most farm households. The main problem is the supply of protein as soybean and fish meals are not available in rural areas. Phengsavanh and Stür (2006) showed that growth rates were increased from 100 to 200 g/day by providing some protein-rich forage in the form of stylosanthes. However, other forages appear to have more potential in pig diets based on rice bran (Preston 2006). 

Taro (Colocasia esculenta) is known as a food crop which provides high yield of roots (or corms) and foliage Taro is a tropical food crop that can be grown under flooded or upland conditions (Chhay Ty et al 2007). Its leaves are rich in protein and easy to ensile (Pheng Buntha et al 2008; Rodríguez and Preston 2009).  One constraint to the feeding of taro foliage is the presence of calcium oxalate which forms crystals on the surface of the leaves. These cause irritation on the skin and in the mouth, and this reduces intake (Pham Sy Tiep et al 2005).  According to Du Thanh Hang and Preston (2008) and Pheng Buntha et al (2008), the farmers in Central Vietnam and in Cambodia cook the taro leaves with rice or rice bran or cassava roots, in order to reduce the concentration of calcium oxalate. Du Thanh Hang and Preston (2008) showed that ensiling was equally effective in reducing the calcium oxalate and that there were no differences in crude protein digestibility and N retention between diets with cooked and ensiled taro leaves.  

Xanthosoma sagittifolium known as New Cocoyam in South America is a member of the same Araceae family as Colocacia esculenta  and has similar characteristics in terms of the presence of calcium oxalate. An important step in the research with this plant was the finding that the stem was quite rich in soluble sugars (Rodriguez et al 2009; Dao Thi Mai Tien et al 2010); and that combining the stem with the leaves facilitated the ensiling process (Rodriguez et al 2009), making it unnecessary to use additives such as molasses (eg: Malavanh et al 2008).  The ensiling of the combined leaf and stem of Taro (Colocacia esculenta) is now widely employed in Cambodia (Chhay Ty et al 2010) and Vietnam (Du Thanh Hang and Preston 2008).

The purpose of the present study was to determine the optimum level of taro silage when used as the only supplement to rice bran in the diet of growing pigs.

Material and methods

Location and duration

The experiment was conducted in the experimental area of Angiang University (AGU), in Angiang province, Vietnam, from 24th August to 16th October, 2010.

Experimental design

Four treatments were compared in a 4*4 Latin Square arrangement with 4 pigs and 4 periods (Table 1). The treatments were:  

• TS100: only Taro silage (TS)

• TS75: 75% TS and 25% rice bran (RB)

• TS50: 50% TS and 50%  RB

• TS25: 25% TS and 75% RB

 The duration of the experiment was 40 days with 4 periods each of 10 days, the first 5 days for adaptation then 5 days for data collection (feed residues, feces and urine). 

Animals and housing

Four male castrated crossbred pigs with average live weight of 10 kg were housed in cages made of bamboo, designed to separate feces and urine (Photo 1). The floor area was 60*60 cm. 

Feeds and feeding

The Taro foliage (leaves with stems) was collected in the vicinity of Angiang University where it was growing naturally (Photo 2).

Photo 2: Taro (Colocacia esculenta) growing wild in An Giang city

The leaves and stems were chopped into small pieces (2-3 cm length) (Photo 3) and exposed to sunlight for 6 hours to reduce the moisture to about 75%, prior to packing tightly into 50 litre plastic bags where it was stored for 14 days before being fed to the pigs (Photo 4). Rice bran and taro silage were fed two times per day at 6:00 AM and 4:00 PM, the amount being based on an offer level of 40 g DM/kg live weight. For treatments TS25, 50 and 75, the rice bran was fed first, followed by the taro silage the quantity pf which was adjusted so as to minimize residues. Water was supplied ad libitum through nipple drinkers.      

Measurements and data collection

The pigs were weighed in the morning before the start of each period. Feed offered was recorded and refusals collected daily. The refusals were stored in a refrigerator (4 °C) until the end of each collection period when they were mixed and sub-samples taken for analysis of DM, ash and N. Feces and urine were collected daily. Each day 20 ml of 15 %  H₂SO₄ were added to the urine container to maintain the pH of the urine below 4.0.  All the feces were stored in the refrigerator until the end of the collection period when they were mixed and a sub-sample taken for analysis of DM, ash and N. A sub-sample of urine was taken daily and stored in the refrigerator until the end of the collection period when the samples were mixed and a sub-sample taken for analysis for N.

Chemical analysis

Samples of feeds offered and refused and feces were analysed for DM, ash and N using the procedures of AOAC (1990). Urine was analysed for N (AOAC, 1990).  

Statistical analysis

The data were analyzed using the general linear model (GLM) option of the ANOVA program in the MINITAB software (Minitab 2000). Sources of variation were pigs, periods, treatments and error.

Results and discussion

Feed composition and feed intake

The rice bran was of moderate quality (10.5% CP in DM) compared with that used by Nguyen Tuyet Giang et al (2010) in an experiment with ducks in An Giang (13.2% CP in DM). By contrast, the taro silage (CP 17.2% in DM) compared favourably with that prepared by Nguyen Tuyet Giang et al (2010) (18.7% in DM).

The Taro silage and rice bran as the basal diet were consumed completely; there were no residues of rice bran and taro silage on all treatments (Table 3). The daily DM intakes showed a curvilinear trend increasing as the proportion of taro silage was raised from 25 to 50% then declining (Figure 1; Figure2).  As a function of live weight the intakes were high (37 to 50 g DM/kg live weight).  

Figure 1.  Relationship between proportion of taro silage in the diet and daily DM intake as function of live weight

Coefficients of total tract apparent digestibility

The coefficients of apparent digestibility of DM, OM and CP were high on all treatments with highest values on Taro silage as the sole diet and lowest values on the 75% rice bran diet (Table 4). Compared to Chhay Ty et al (2010), apparent digestibility coefficients on the present study were higher for the diets containing Taro silage.

 Nitrogen balance

N intakes were higher with 50% taro silage in the diet than with 25 or 50% with intermediate values with 75% taro silage in the diet (Table 5). These intakes mostly reflected differences in DM intake which was highest on the TS50 diet. N retention followed the same trend with highest values for the TS50 diet. However, when N retention was corrected for differences in DM intake, the highest N retention was on the 100% taro silage diet  with no differences among the diets that also contained rice bran (TS2\5, TS50 to TS75).

Figure 4: Trends in N balance with increasing proportions of taro silage in the diet of growing pigs	Figure 5: Comparison of N retention with and without correction for DM intake in pigs fed different ratios of rice bran and taro silage

Diuretic effect of Taro silage

The volume of urine excreted by the pigs increased (Figure 6) with a curvilinear tendency (Figure 7) as the intake of taro silage increased., being almost threefold greater on the 100% compared with the 25% taro silage diet.  A diuretic effect in pigs due to feeding water spinach has been reported by Chhhay Ty and Preston (2006) and Nguyen Yuyet Giang (2009) but this appears to be the first observation of such an effect due to feeding taro silage.

Figure 6. Mean values of urine excreted in pigs fed taro silage with rice bran.	Figure 7.  The relationship between intake of taro silage and the urine excreted in pigs fed Taro silage and rice bran.

Conclusions

• Diets with 50% of taro silage plus 50% rice bran (DM basis) supported higher rates of feed intake (49.9 g DM/kg LW/day) than diets with more or less taro silage.
  
  
• Apparent digestibility coefficients of DM, OM  and crude protein were high and tended to increase as the proportion of taro silage in the diet was increased from 25 to 100% (from 85 to 89 for DM and OM and from 81 to 88% for crude protein).
  
  
• N retention was higher with 50% taro silage in the diet than with 25 or 50% with intermediate values for 75% taro silage.  However, when N retention was corrected for differences in DM intake, the highest N retention was on the 100% taro silage diet  with no differences among the diets that contained rice bran.
  
  
• Urine excretion was increased threefold by raising dietary taro silage intake from 25 to 100% of the diet.

Acknowledgements

The authors would like to express sincere gratitude to the MEKARN program, financed by Sida/SAREC (Swedish International Development Cooperation Agency - Department for Research Cooperation) for supporting this mini-project. We are very grateful to Mr Tran Trung Tuan, Ms Nguyen Tuyet Giang, and the staff  and students of Angang University (AGU), Vietnam, for their help and support during the experiment.

References

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

Pheng Buntha, Borin K, Preston T R and Ogle B 2008  Survey of taro varieties and their use in selected areas of Cambodia.  Livestock Research for Rural Development. Volume20, supplement.  http://www.cipav.org.co/lrrd/lrrd20/supplement/bunt1.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 20, Article #137.  http://www.lrrd.org/lrrd19/9/chha19137.htm

Chhay Ty and Preston T R  2006  Effect of different ratios of water spinach and fresh cassava leaves on growth of pigs fed basal diets of broken rice or mixture of rice bran and cassava root meal. Livestock Research for Rural Development. Volume 18, Article No. 57. http://www.lrrd.org/lrrd18/4/chha18057.htm

Chhay T, Borin K and Preston T R 2010 Effect of Taro (Colocasia esculenta) leaf + stem silage and mulberry leaf silage on digestibility and N retention of growing pigs fed a basal diet of rice bran. Livestock Research for Rural Development. Volume 22, Article #109. http://www.lrrd.org/lrrd22/6/chha22109.htm 

Du Thanh Hang and  Preston T R 2008 Taro (Colocacia esculenta) leaves as a protein source for growing pigs in Central Viet Nam Proceedings MEKARN Regional Conference 2007: Matching Livestock Systems with Available Resources (Editors: Reg Preston and Brian Ogle), Halong Bay, Vietnam, 25-28 http://www.mekarn.org/prohan/hang_hue_new.htm

Dao Thi My Tien, Nguyen Tuyet Giang and Preston T R 2010 A note on ensiling banana pseudo-stem with taro leaves and petioles. MEKARN Conference 2010,  Live stock production, climate change and resource depletion (Editors: Reg Preston and Brian Ogle) http://www.mekarn.org/workshops/pakse/abstracts/tien_agu2.htm

ILRI. 2002. Review of the Livestock Sector in the Lao People’s Democratic Republic.

Malavanh C, 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.lrrd.org/lrrd20/supplement/mala1.htm

MINITAB 2000 Minitab reference Manual release 13.31. User’s guide to statistics. Minitab Inc., USA

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Nguyen Tuyet Giang, Preston T R and Ogle B 2010: Effect on the performance of common ducks of supplementing rice polishings with taro (Colocacia esculenta) foliage. Livestock Research for Rural Development. Volume 22, Article #194. http://www.lrrd.org/lrrd22/10/gian22194.htm

Phengsavanh Phonepaseuth and Stür Werner 2006 The use and potential of supplementing village pigs with Stylosanthes guianensis in Lao PDR, from: http://www.mekarn.org/proprf/wern.htm

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. http://www.mekarn.org/proctu/tiep44.htm

Preston T R 2006: Forages as protein sources for pigs in the tropics. Workshop-seminar "Forages for Pigs and Rabbits" MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August,  2006. Article #2 http://www.mekarn.org/proprf/preston.htm

Rodríguez L and Preston T R 2009   A note on ensiling the foliage of New Cocoyam (Xanthosoma sagittifolium).  Livestock Research for Rural Development. Volume 21, Article #183.  http://www.lrrd.org/lrrd21/11/rodr21183.htm

Received 14 January 2011; Accepted 11 February 2011; Published 6 March 2011

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