Effect of wilting cassava leaves and supplementing them with DL-methionine, on intake, growth and feed conversion in growing pigs

Ty Chhay, 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
 ^* Finca Ecológica, TOSOLY, AA #48, Socorro, Santander, Colombia 

Abstract 

Twenty four crossbred castrated male pigs with initial body weight from 14 to 28kg were allocated to 4 treatments according to a 2*2 factorial arrangement. The factors were: fresh or wilted (24h) cassava leaves and supplementation or not with DL-methionine.  The cassava leaves supplied 36% of the diet DM and 75% of the dietary crude protein, the other ingredients being rice bran and sugar palm syrup

 Supplementation with DL-methionine increased growth rate and improved feed conversion when the leaves were fed fresh but had no effect when the leaves were wilted 24 hours. Wilting the leaves 24 hours improved growth rates but not feed conversion in the absence of methionine supplementation but had no effect when supplementary methionine was provided. Daily intakes of the equivalent of 5 mg HCN/ kg live weight were not toxic under the conditions of the experiment. 

Key words: cassava leaf, FCR, HCN, live weight gain, methionine, wilted

Efecto del marchitamiento de hojas de yuca y su suplementación con DL-metionina, en el consumo, crecimiento y conversión alimenticia en cerdos en crecimiento

Resumen

Veinticuatro cerdos cruzados machos castrados con peso corporal inicial de 14 a 28 kgs fueron asignados a 4 tratamientos de acuerdo a un arreglo factorial 2*2. Los factores fueron: hojas de yuca frescas o marchitas (24h) y suplementación o no con DL-metionina. Las hojas de yuca suministraron el 36% de la MS y el 75% de la proteína cruda de la dieta, el resto de los ingredientes fueron salvado de arroz y jarabe de palma de azucar.

La suplementación con DL-metionina incrementó la tasa de crecimiento y mejoró la conversión alimenticia cuando se usaron hojas frescas pero no tuvo efecto cuando se usaron hojas marchitas (24 horas). Las hojas marchitas (24 horas) mejoraron la tasa de crecimiento pero no la conversión alimenticia en la ausencia de suplementación con metionina, pero no hubo efecto cuando se suplementó con metionina. Consumos diarios equivalentes a 5 mg HCN/kg peso vivo no presentaron toxicidad bajo las condiciones de este experimento.

Palabras clave: hojas de yuca, TCA, HCN, ganancia de peso vivo, metionina, marchitamiento

Introduction

Cassava leaves as a protein source for pigs have been the subject of many recent studies in SE Asia and Latin America (Bui Huy Nhu Phuc 2006; Preston 2006). In this connection, some constraints to cassava utilization in pig feeding, such as the cyanogenic glucosides present in the plant (Gómez and Valdivieso 1985; Ravindran and Ravindran 1988) can be neutralized successfully by ensiling (Ravindran 1992, Chhay Ty et al 2001) and sun drying (Bui Hui Nhu Phuc et al 1996). However, these methods can be time-consuming and in the case of sun drying are difficult in the rainy season. Wilting under a roof promises to be a simpler and more reliable procedure. According to a recent study in growing pigs (Chhay Ty et al 2007), 24h wilting reduced slightly the HCN content of cassava leaves but had no effect on apparent DM digestibility and nitrogen retention.  It was suggested that amino acid imbalances were probably of greater importance than presence of cyanogenic glucosides as factors limiting the utilization of this feed resource. It is logical to expect that provision of supplementary methionine would be beneficial in diets containing cassava leaves, as it is well established that the process of detoxification of cyanogenic glucosides causes an increased demand for sulfur-containing amino acids (Maner and Gomez 1973) or elemental sulphur (Oke 1978). Support for this hypothesis can be found in the report by Du Thanh Hang et al (2006) that production performance of pigs was improved when diets with 20% fresh cassava leaves (DM basis) were supplemented with 0.2% of synthetic DL-methionine.

The aim of the present study was to examine possible interactions between the effects of wilting and of supplementation with DL-methionine, on intake, growth and feed conversion in growing pigs

Materials and methods 

Location 

The experiment was carried out from 19 July to 16 November 2007 at the 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 

Twenty four crossbred castrated male pigs with initial body weights in the range of 14 to 28kg were allocated to individual pens in 3 blocks according to body weight, and within blocks to a 2*2 factorial arrangement of four treatments. The first factor was wilting 24h or no wilting; the second factor was supplementary DL-methionine (with or without). There were two replicates within each of the 3 blocks.

Individual treatments were (Table 1):

•  FC: Fresh cassava leaves

• FCM: Fresh cassava leaves plus 0.2% methionine

• 24WC: Wilting cassava leaves 24h

• 24WCM: Wilting cassava leaves 24h plus 0.2% methionine

The pigs were housed in individual pens with concrete floor and provided with feeders and drinking nipples. The pigs were vaccinated against common diseases such as 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 

Broken rice was purchased from the rice mill near CelAgrid and sugar palm was purchased from shops in Phnom Penh city. Cassava leaves (sweet variety) were harvested every day beginning 3 months after planting in existing plots in CelAgrid, which were fertilized from biodigester effluent. Some leaves were purchased from farmers who plant cassava for root production.

Cassava stems and petioles were removed from the leaves, which were then chopped into small pieces and offered immediately for feeding fresh or left for wilting in the shade for 24 hour after chopping. The basal diet was broken rice and sugar palm (diluted with water 1:1) restricted to 1.5% and 1% respectively (DM basis) of live weight and the cassava leaves from 1-1.5% of body weight depending on observations of feed intake. The chemical composition of ingredients is show in Table 2. The daily allowance was offered in three meals daily (8.00, 12.00 and 17.00h).

Data collection and analyses 

The pigs were weighed every 10 days during the 120 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 content, N and HCN. The DM content was determined using the microwave method of Undersander et al (1993). N and HCN were analyzed following procedures of AOAC (1990). 

Statistical analysis 

Data for weight gain, DM feed intake, and crude protein intake, feed conversion rate and HCN were analyzed using the general linear model (GLM) option of the ANOVA software of Minitab (2000). The sources of variation were processing, methionine, interaction between processing*methionine and error. 

Results and discussion 

DM intake as function of live weight was increased by methionine supplementation but not by wilting (Figures 1 and 2; Table 3). There was no interaction between supplementation and wilting.

Live weight gain was increased by methionine supplementation and by processing (Table 3). However, in this case the interaction was significant. Methionine supplementation significantly increased growth rates when the cassava leaves were fed fresh ; but had no effect when the leaves were wilted 24 hours (Figures  3, 4, 5 and 6).  

Similarly, wilting increased growth rate in the absence of methionine but not when methionine was added to the diets (Figure 4). Results for DM feed conversion were similar with significant improvements due to methionine supplementation, no effect due to wilting and with a strong tendency (P=0.065) to an interaction between the two factors. As with live weight gain, methionine supplementation improved feed conversion when cassava leaves were given fresh, but had no effect when they were wilted 24h (Table 4).

The HCN intakes on the diets with fresh cassava leaves (about 5 mg/kg LW) are at the high end of the levels reported to be toxic in pigs (1.4 according to Getter and Baine 1938;  2.1 to 2.3 in Johnson and Ramond 1965; 4.4 in Butler 1973 and 3.5 mg/kg LW in Tewe1992). However, there were no symptoms of ill-health and no apparent relationship between intake of HCN and production response as measured by DM intake and live weight gain.  These findings are in agreement with the results of Du Thanh Hang and Preston (2005) and Chhay Ty and Preston (2005, 2006) that production responses in pigs fed fresh cassava leaves are not related with levels of ingestion of HCN.

The significant interaction between the effects of methionine and wilting on growth rate (Figure 7) nevertheless indicates that there may be some advantages in reducing the levels of HCN (eg: by 24h wilting) or facilitating it’s detoxification by providing additional sources of sulphur, in this case in the form of synthetic methionine.

Promkot and Wanapat  (2008) showed that increasing the level of sulphur in the diet of dairy cows fed cassava foliage  led to increases in voluntary intake and live weight gain. The effect was more pronounced when the cassava foliage was fed fresh compared with feeding it as hay.

Conclusions 

• In pigs given diets with 36.5% of the DM (75% of the dietary protein) as fresh cassava leaves, supplementation with DL-methionine increased growth rate and improved feed conversion when the leaves were fed fresh but had no effect when the leaves were wilted 24 hours.

  
  

• Wilting the leaves 24 hours improved growth rates but not feed conversion in the absence of methionine supplementation but had no effect when supplementary methionine was provided.

  
  

• Daily intakes of the equivalent of 5 mg HCN/ kg live weight were not toxic under the conditions of the experiment.

Acknowledgments 

The authors would like to express their gratitude to the International Foundation for Science (IFS), for financing the research as part of the project B 3759-1, and to the Center for Livestock and Agriculture Development (CelAgrid), for providing resources and facilities for this experiment.
 

References 

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

Bui Huy Nhu Phuc, Ogle R B, Lindberg J E and Preston T R 1996. The nutritive value of sun-dried and ensiled cassava leaves for growing pigs. Livestock Research for Rural Development. Retrieved (8) 3, Retrieved from http://www.lrrd.org/lrrd8/3/phuc83.htm

Bui Huy Nhu Phuc 2006: Review of the nutritive value and effects of inclusion of forages in diets for pigs. Workshop-seminar "Forages for Pigs and Rabbits" MEKARN-CelAgrid, Phnom Penh, Cambodia, 22-24 August,  2006. Article #7 RetrievedAugust 25, 108, from http://www.mekarn.org/proprf/phuc.htm

Butler G W 1973 Physiological and genetic aspects of cyanogenesis in cassava and other plants, Chronic cassava toxicity. Proceedings of the Interdisciplinary Workshop, London England, 29-30 Jan. 1973.

IDRC -010e, pp. 65-71
 

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 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 Ty, Ly J and Rodríguez Lylian 2001 An approach to ensiling conditions for preservation of cassava foliage in Cambodia. Livestock Research for Rural Development 13: http://www.lrrd.org/lrrd13/2/chha132.htm

Chhay Ty, Preston T R and Borin K 2007: Effect of variety and wilting on HCN content of cassava leaves and on intake, digestibility and N retention by growing pigs. Livestock Research for Rural Development. Volume 19, Article #135. Retrieved printDate()September 12, 2007, from http://www.lrrd.org/lrrd19/9/chha19135.htm

Du Thanh Hang and Preston T R 2005 The effects of simple processing methods of cassava leave on HCN content and intake by growing pigs. Livestock Research for Rural Development. Volume 17, Article No. 99. http://www.lrrd.org/lrrd17/9/hang17099.htm

Du Thanh Hang, N. Q. Linh, T. R. Preston, H. Everts and A. C. Beynen 2006. The effect of simple processing methods of cassava leaves on HCN content, intake and performance by growing pig, Workshop on forage for pigs and rabbit, Phnom Penh, 22-24 august 2006  http://www.mekarn.org/proprf/hang.htm

Getter A O and Baine J 1938 Research on cyanide detoxification. American Journal of Medical Science. pp. 185-189

Gómez G and Valdivieso M 1985. Cassava foliage: chemical composition, cyanide content and effect of drying on cyanide elimination. Journal of the Science of Food and Agriculture 36:433-441

Johnson R M and Ramond W D 1965 The chemical composition of some Tropical food plants: Manioc. Tropical Science 7, pp. 109-115.
 

Maner J H and Gomez  G 1973 Implications of cyanide toxicity in animal feeding studies using high cassava rations. ed. Nestel, B. and MacIntyre, R. In: Chronic cassava toxicity. Proceedings of an interdisciplinary workshop, London, UK. 29–30 January 1973. Ottawa, International Development Research Centre, IDRC-010e, 113–120

Minitab 2000 User’s guide to statistics. Minitab Inc., USA.

Oke O L 1978 Problems in the use of cassava as animal feed. Animal Feed Science and Technology 3: 345-380

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 RetrievedOctober 28, 108, from http://www.mekarn.org/proprf/preston.htm

Promkot C and Wanapat M 2008 Effect of sulfur on rumen ecology, blood metabolites, hormones and production in lactating dairy cows supplemented with fresh cassava foliage or cassava hay.  Proceedings MEKARN Regional Conference 2007: Matching Livestock Systems with Available Resources (Editors: Reg Preston and Brian Ogle), along Bay, Vietnam, 25-28 November 2007 http://www.mekarn.org/prohan/cham.htm

Ravindran V 1992 Preparation of cassava leaf products and their use in animal feeding. In: Roots, tubers, plantains and bananas in animal feeding (D H Machin and S Nyvold, ed.) FAO Animal Producction and Health Paper 95. Rome. P 111-126 http://www.fao.org/DOCREP/003/T0554E/T0554E08.htm

Ravindran V and Ravindran G 1988 Changes in the nutritional composition of cassava (Manihot esculenta Crantz) leaves during maturity. Food Chemistry 27:299-239

Tewe O O 1992 Detoxification of cassava products and effects of residual toxins on consuming animals. In: Roots, tubers, plantains and bananas in animal feeding. (D. Machin and S. Nyvold, editors) FAO Animal Production and Health Paper No 95. Rome p 81-98 http://www.fao.org/docrep/003/T0554E/T0554E06.htm

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

Received 15 October 2008; Accepted 30 November 2008; Published 1 January 2009

Go to top