Effect of processing taro foliage on growth of pigs fed two grades of rice bran

Chhay Ty, Khieu Borin and T R Preston*

Center for Livestock and Agriculture Development (CelAgrid),
Pras Teat village, Rolous commune, Kandal Stung district, Kandal province.
PO Box 2423 Phnom Penh 3, Cambodia
chhayty@celagrid.org
* TOSOLY, AA48 Socorro, Santander, Colombia

Abstract

Eighteen crossbred castrated male pigs with initial body weights in the range of 16 to 28 kg were allocated to individual pens in 3 blocks according to body weight, and within blocks to a 2*3 factorial arrangement of 6 treatments. The first factor was grade of rice bran (fine or coarse); the second factor was processing of taro foliage (dried leaves, ensiled leaves or ensiled leaves plus petioles).

The fine grade rice bran had higher percentages of crude protein and crude fat and less fiber than the coarse grade and supported better performance in growing pigs. Taro leaves and taro leaves+petioles, that had been ensiled with rice bran,  were less palatable than taro leaves that had been sun-dried.

Key words: Colocacia esculenta, drying, ensiling, feed conversion, live weight gain, water spinach

Introduction

A recent (2006) workshop in Cambodia (http://www.mekarn.org/proprf/content.htm) focused attention on the increasing interest in the use of forages as protein sources for pigs in SE Asian countries in view of escalating costs of traditional sources of protein such as fish meal and soybean meal. The leaves of the Taro species (Colocia esculenta, Alocasia macrorrhiza, Xanthosoma sagittifolium) have attracted attention in view of the high protein content and the fact that many species are found growing in the wild state in mountain areas, in forests and in ponds and other water surfaces (Pham Sy Tiep et al 2007; Ngo Huu Toan and Preston 2008; Pheng Buntha et al 2008).  In surveys by these authors on farmer practices on the use of taro leaves, it was found that they were occasionally fed to pigs but usually after boiling as farmers had observed that this eliminated the itching of the mouth and skin when the fresh leaves were fed. This itching problem appears to be caused by the presence of crystals of calcium oxalate in the leaves and petiole since the levels of this substance in leaves of Alocacia macrorrhiza were reduced markedly by boiling or ensiling (Pham Sy Tiep et al 2007).  Du Thanh Hang and Preston (2008) subsequently showed that intake of the leaves and nitrogen retention were increased when the fresh leaves of Colocacia esculenta were boiled or ensiled. In a study in our laboratory, it was found that sun-dried Colocacia leaves supported higher feed intake and N retention in growing pigs than the ensiled leaves (Chhay Ty et al 2007).

It is reasonable to believe that the mixing of two sources of leaves would be advantageous as a means of complementing arrays of amino acids and reducing overall concentrations of anti-nutritional compounds. This strategy gave positive results when water spinach foliage replaced 50% of the cassava leaves as the protein source in pig diets (Chhay Ty and Preston 2005) and when combinations of mulberry leaves and water spinach were used instead of water spinach alone (Chiv Phiny et al 2008).

Another factor considered to limit the utilization of protein-rich forages for pigs is the high fibre content, which reduces the digestibility of the protein (Ogle 2006). For this reason, feeds of zero fibre content such as sugar cane juice (Rodriguez et al 2006) and sugar palm syrup  (Pheng Buntha et al 2008), or with very low fibre such  as cassava roots (Chittavong Malavanh et al 2008), have been investigated as the energy source to accompany leaves of Xanthosoma and Colocacia in pig diets. Rice bran as produced  in most rice mills of Cambodia contains high levels of crude fibre with values of up 20%, which is at the high end of the range (9 to 19%) reported in the data base compiled by Göhl (1973). It appears that in many of these mills, which have relatively old milling technology, part of the rice husks find its way into the bran, thus increasing the fiber content and reducing the nutritive value. It was therefore hypothesized that by passing the bran through a fine mesh screen, it should be possible to derive a product of higher nutritive value.

The research reported here aimed to test the effect on pig growth of using  basal diets containing fine or coarse grades of rice bran, supplemented with taro foliage which had been dried or ensiled. The relative effect of ensiling the combined leaf plus petiole compared with leaves alone was also investigated.

Materials and methods  

Location  

The experiment was carried out from 20 August to 29 November 2008 in the experimental farm of Center for Livestock and Agriculture Development (CelAgrid), located in Phras Teat village, Rolous Commune, Kandal stung district, Kandal province about 25km from Phnom Penh City, Cambodia.  

Experimental animals, treatments and design 

Eighteen crossbred (Exotic*Indigenous) castrated male pigs with initial body weight in the range of 16 to 28kg were allocated to individual pens in 3 blocks according to body weight, and within blocks to a 2*3 factorial arrangement of 6 treatments. The first factor was grade of rice bran (fine or coarse); the second factor was processing of taro foliage (dried leaves, ensiled leaves or ensiled leaves plus petiole). There were three replicates of each treatment.

Individual treatments were

·                    DL-F: Dry taro leaves plus fine rice bran

·                    EL-F: Ensiled leaves plus fine rice bran

·                    EF-F: Ensiled leaves plus petiole plus fine rice bran

·                    DL-C: Dry taro leaves plus coarse rice bran

·                    EL-C: Ensiled leaves plus coarse rice bran

·                    EF-C: Ensiled foliage (leaves plus petiole) plus coarse rice bran

The pigs were housed in individual pens with concrete floors and provided with feeders and drinking nipples. They were vaccinated against salmonellosis and swine fever and were de-wormed with Ivomectin prior to being adapted to the feeds and the housing for 10 days before starting the experiment.  

Feeds, feeding and management 

Rice bran was purchased from the rice mill near CelAgrid. It was sieved by passing it through a plastic net with holes of 1 mm, to separate the fine and coarse particles. Taro leaves and petioles (Colocacia esculenta) were harvested from ponds in the region around the CelAgrid Center. For two thirds of the taro foliage, the petioles were removed. The remaining leaves were then either dried under sunlight for 3-4 days after which they were ground in a hammer mill with 1 mm screen; or were ensiled after hand chopping and the addition of 10 kg of rice bran and 0.5 kg of salt for 100 kg of fresh leaves. The fraction containing leaves plus petioles was ensiled in the same way as for leaves alone.  The water spinach was from plots established within the CelAgrid farm. It was harvested daily and chopped into small pieces (1-2 cm) before being fed.

The daily feed allowance was given in three meals at 07.00, 12.00 and 15.00h. The quantities offered of each dietary ingredient were based on an expected total daily intake of 40g DM per 1 kg live weight and the projected proportions of each ingredient (Table 1) adjusted for the respective percentages of DM  (Table 2).  

The rice bran fractions were given first followed by the two forages which were placed in separate troughs. Feed refusals were partitioned into three fractions corresponding to each diet ingredient. 

Data collection and analyses 

The pigs were weighed every 10 days during the 100 days of the experiment. Feeds offered and residues were recorded daily. Representative samples of feeds offered and residues were taken one time per 10 days to estimate DM, N, crude fiber and crude fat. The DM content was determined using the microwave method of Undersander et al (1993). N and crude fiber were analyzed following procedures of AOAC (1990). Crude fat in the rice bran fractions was determined by immersing nylon bags containing the bran in gasoline for 24 hours and measuring the loss of DM.

Statistical analysis 

Data for weight gain, feed intake and feed conversion were analyzed using the general linear model (GLM) option of the ANOVA software of Minitab (2000). The sources of variation were processing of taro foliage, grade of rice bran, interaction between processing*grade of rice bran and error. 

Results and discussion  

Processing of rice bran

The sieving of the rice bran produced two fractions which differed markedly in proximate composition (Table 2). The fine fraction contained more crude protein, more fat and less fiber, than the coarse fraction (Table 2).

Dried and ensiled taro leaves had a similar composition but incorporation of the petioles in the silage reduced the protein and increased the fibre content.

Feed intake

Intake (DM basis) of rice bran was higher and of ensiled taro foliage and water spinach lower for the diets with the fine compared with the coarse grade of bran (Table 3).

There appeared to be considerable differences in the sources of the protein consumed by the pigs on the different treatments (Table 3: Figures 3 and 4).

Pigs fed fine rice bran consumed more of the protein from the bran than from the foliages; the opposite occurred with the coarse bran treatment. Pigs fed ensiled taro leaves ate less protein from the foliages than pigs on the other taro treatments. However, while pigs fed the dried taro leaves ate similar proportions of taro leaf and water spinach protein, on the ensiled leaves+petioles treatment most of the foliage protein came from water spinach. In the end, the percentages of crude protein in the diet DM as consumed did not differ among treatments, despite the differences in the sources of the protein.

Growth and feed conversion

Growth rates were 27% greater, and feed conversion 15% better, in pigs fed the diet with fine bran compared with the diet having the coarse bran (Table 4; Figure 5). There were no differences due to the method of processing the taro foliage (Table 4).

Discussion

The better growth and feed conversion in pigs fed the fine grade of rice bran is a logical consequence of the superior nutritive value of this product compared to the coarse grade, namely higher levels of protein and fat and lower concentrations of fiber.  The lack of difference in pig production traits between the different ways of processing the taro foliage may be because of the confounding effect of the associated water spinach. Pigs ate less taro leaves when these were ensiled than when they were dried; however, the pigs compensated by eating more water spinach thus the total protein derived from the combined foliages was similar on the three taro treatments.

The lower acceptability of the ensiled compared with dried taro leaves corroborates our earlier findings when these two methods of processing were compared (Chhay Ty and Preston 20). However, it differs from experience elsewhere where high acceptability of the ensiled leaves or ensiled leaves + petioles by pigs has been reported. Thus Du Thanh Hang and Preston (2008) reported that ensiled taro leaves accounted for 44% of the dietary protein in pigs fed a basal diet of cassava root meal and rice bran. In an experiment with pregnant and lactating Mong Cai pigs, the intakes of ensiled taro leaves accounted for more than one third of the dietary protein (Chittavong Malavanh et al 2008). In both these reports,  the same species of taro was used (Colocacia esculenta) but the leaves were ensiled with 4% molasses. It would seem that the mistake was to use rice bran as the ensiling additive for both the leaves and the combined  leaves + petiole. In the fresh state the leaves of Colocacia have 16% DM and the petioles 7%, thus after the inclusion of 10% rice bran, the final ensiled product would have contained of the order of 30 to 40% rice bran on DM basis.  It is possible that this high level of bran in the silages was the reason for the negative effect on silage intake. The recent observations in Colombia (Rodríguez and Preston 2009), where combined leaves and petioles of New Cocoyam (Xanthosoma sagittifolium) are regularly ensiled with no additive (1.5 tonnes of silage are made and fed monthly to pigs  indicate that palatability of the silage is very high.  High acceptability by growing pigs of ensiled leaves + petioles of Colocacia esculenta have also been reported in Central Vietnam (Du Thanh Hang, in preparation), although in this case 4% molasses was added at the time of ensiling.

Conclusions leaves

•  Rice bran that had been sieved to eliminate the coarser particles had higher percentages of crude protein and crude fat and less fibre than the coarse particles, and supported better performance in growing pigs.

  
  

• Taro leaves and taro leaves+petioles, that had been ensiled with a high level (10%) of rice bran, were less palatable than taro leaves that had been sun-dried.

Acknowledgments 

The authors would like to express their gratitude to the MEKARN project financed by SIDA-SAREC, and to the Center for Livestock and Agriculture Development (CelAgrid), for providing resources for conducting this experiment.

References 

AOAC 1990 Official Methods of Analysis. Association of Official Analytical Chemists. 15th edition (K Helrick editor). Arlington pp 1230 

Chhay Ty and Preston T R 2005 Effect of water spinach and fresh cassava leaves on growth performance of pigs fed a basal diet of broken rice. Livestock Research for Rural Development. Volume 17, Article No. 76. http://www.lrrd.org/lrrd17/7/chha17076.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.lrrd.org/lrrd19/9/chha19137.htm

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Chiv Phiny, Ogle B, Preston T R and Borin K 2008  Growth performance of pigs fed water spinach or water spinach mixed with mulberry leaves, as protein sources in basal diets of cassava root meal plus rice bran or sugar palm syrup plus broken rice.  Livestock Research for Rural Development. Volume 20, supplement. http://www.lrrd.org/lrrd20/supplement/phin2.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: T R Preston and B Ogle), Halong Bay, Vietnam, 25-28 November 2007 http://www.mekarn.org/prohan/hang_hue.htm

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MINITAB 2000 Minitab Reference Manual release 13.31.

Ngo Huu Toan and Preston T R  2008 Taro as a local feed resource for pigs in small scale household condition. Proceedings MEKARN Regional Conference 2007: Matching Livestock Systems with Available Resources (Editors: T R Preston and B Ogle), Halong Bay, Vietnam, 25-28 November 2007 http://www.mekarn.org/prohan/toan_hue.htm

Ogle R B 2006 Forages for pigs: nutritional, physiological and practical implications. Workshop-seminar "Forages for Pigs and Rabbits" MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August,  2006. Article #1 RetrievedJuly 8, 109, from http://www.mekarn.org/proprf/ogle.htm

Pham Sy Tiep, Nguyen Van Luc, Nguyen Manh Hung, Tran Van Tu and Tran Van Phung 2007 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. http://www.mekarn.org/prohan/tiep.htm

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Received 9 July 2009; Accepted 3 September 2009; Published 1 November 2009

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