Effects of DL-methionine supplementation in ensiled cassava

root-based diets on the performance and economic efficiency of

F1 (Large White x Mong Cai) fattening pigs

Nguyen Thi Loc and Le Khac Huy

Hue University of Agriculture and Forestry

Abstract

Thirty two crossbred (Large White x Mong Cai) pigs, with an average initial live weight of 20 kg were randomly allocated to 4 diets based on ensiled cassava roots supplemented with 0, 0.1, 0.2 and 0.3% DL-methionine (DM basis).

Increasing the level of DL-methionine improved growth rate and feed conversion,  but there was no effect on feed intake. The level of 0.3% slightly reduced daily gain when compared with the 0.2% level. Feed costs for growth were reduced by  9% by 0.2% DL-methionine supplementation.

Supplementation with DL-methionine at 0.2% in ensiled cassava root - based diets gave the best results on performance and economic efficiency.

Key words: Economics, feed conversion, growth, methionine, Mong Cai, pigs

Introduction

In animal production generally, and in pig fattening in particular, an adequate  supply of protein, especially with a good amino acid balance, is a particularly important issue that greatly affects the productivity and efficiency of the industry. This problem is more important for fattening pigs in the central  area  of Vietnam where the basic feedstuff is cassava, which can contain relatively large amounts of cyanogenic glucosides that give rise to toxic hydrocyanic acid (HCN) when chopped or ground. Ensiling cassava roots has been shown to lower the HCN content to 36% of original levels after  26 weeks (Gomez and Valdivieso 1988) and to 59% after 60 days of ensiling (Nguyen Thi Loc 1996). In the animal body, the detoxification of HCN needs methionine, a sulphur donor amino acid, which converts hydrogen cyanide to non-toxic thiocyanate (Oke 1973). Portela and Maner (1972) reported that pigs fed a diet with 55% cassava root meal supplemented by 0.1% DL-methionine had higher daily weight gains and better feed conversion in comparison with the un-supplemented control  or with 0.2% DL-methionine. Job (1975) came to the conclusion that methionine supplementation improved live weight gain and feed conversion efficiency in pigs fed cassava roots-based rations, because the amino acid is needed for detoxification of the HCN in the cassava. In an earlier experiment (Nguyen Thi Loc 2001), nitrogen retention values in growing pigs fed a cassava root-based diet were 19.3, 20.1, 20.8 and 21.9 for supplementation with 0, 0.1, 0.2 and 0.3%  DL-methionine, respectively.  

Based on this theoretical  and practical background, an experiment was carried out to evaluate the effects of D-L methionine supplementation in ensiled cassava root-based diets fed to F1 (Large White x Mong Cai) fattening pigs, with the aims of improving the amino acid balance of the rations and reducing the HCN content, in order to improve weight gains and thus increase the economic efficiency of pig fattening.
 

Materials and methods

Location

The experiments were carried out in Thua Thien Hue province Pig Breeding Centre from November 2000 to April  2001.

Experimental design

A total of 32 cross-bred (LW x MC) pigs with an average initial live weight of 20 kg were randomly allocated to four treatments consisting of levels of supplementation with 0, 0.1, 0.2 and 0.3% DL-methionine. There were 4 replications with 2 pigs per pen.  The control diet was compounded to have 15 and 13% crude protein for the growth stages of 20-50 and 50-90 kg, respectively (Table 1).

Feeding and management

The cassava roots had been ensiled for 30 days when the trial started and for 150 days at the end (Table 2).  The pigs were fed the mixed feed ad-libitum three times per day at 07.00h, 11.00h and 17.00h. Drinking water was available via automatic valves.   

Parameters recorded

Feed intake was recorded daily and live weight monthly. Feed conversion ratios were calculated for the growing and fattening periods. Economic benefits were estimated using current market prices of feed ingredients and live pigs. 

Statistical analysis

The data were analysed by ANOVA using the GLM option of the Minitab 10.2 (1998) software. Sources of variation were treatments and error.

Results and discussion

Changes in pH, DM and HCN concentration with ensiling time

The pH  of the ensiled roots decreased  from  6.6 on the initial day to 4.1 at day 30,  and to 3.8 at day 60, and thereafter remained constant up to 150 days of ensiling. The HCN concentration decreased rapidly from the initial day to 30 days after ensiling, and then continued to fall up to the 150th day of ensiling. These values are in agreement with those of CIAT (1981), Gomez and Valdivieso (1988), Nguyen Thi Loc (1996) and Nguyen Kim Duong and Nguyen van Phong (1995). According to Buitrago (1990), 26-week ensiled cassava contains HCN concentrations as low as 1/3 of the levels of the initial day. 

Live weight gain, feed conversion ratios and economic efficiency

There was a linear increase in growth rate as DL-methionine supplementation was increased from 0 to 0.2% of the diet DM, thereafter decreasing slightly at the 0.3% level (Table 3 and Figure 1). Feed intake was not affected  by methionine supplementation thus feed conversion followed a similar pattern to growth rate in response to methionine supplementation. Feed cost per kg daily gain was lowest on the diet with 0.2% supplementary DL-methionine, and was  9% better in comparison with the control group.
 

Figure 1: Effect of increasing levels of supplementary DL-methionine  on growth rate
of fattening pigs fed diets with high level of ensiled cassava roots

Conclusions

• Live weight gain of pigs fed a diet with high levels of ensiled cassava roots increased linearly with DL-methionine supplementation to a maximum on the diet with the 0.2% level, above which it decreased

• Feed conversion ratio and feed cost per kg daily gain were lowest with 0.2 % DL- methionine supplementation.

Acknowledgements

The authors are grateful to the Swedish International Development Authority (SIDA/SAREC) and IFS for funding this study. We would like to express  gratitude to to Dr Thomas R Preston, Dr E R Orskov and  Dr Le Duc Ngoan who provided useful guidance, encouragement and made it possible for us to complete the task. We also thank our colleagues in the Swine Breeding Centre of Thua Thien Hue province and  Hue University of Agricultural and forestry for supporting the feeding trial.  

References

Buitrago  J A  1990   La yuca en la alimentacion animal, Centro Internacional de Agricultura Tropical CIAT, No. 85. Cali, Colombia, pp. 446.

Gomez G and Valdivieso M  1988  “The effects  of  ensiling cassava whole-root chips on cyanide elimination”, Nutrition Reports International 37, pp. 1081-1092 and 1161-1166.

Job  T A  1975  “Utilization and protein supplementation of cassva for animal feeding and the effect of sulfur sources on cyanide detoxification”, PhD. Thesis, University of Ibadan, Nigeria. (Abstr. on cassava Vol. III), pp. 97-98

Nguyen Kim Duong and Nguyen van Phong 1995 Casava by-products and using them as pig feeds. National Workshop on Animal Science, Ha noi, 1995 (in Vietnamese).

Nguyen Thi Loc 1996  Evaluation of protein supplementation of traditional diets and cassava root silage for local cross breed pigs under village conditions in Central Vietnam.  MSc thesis - Uppsala Sweden. pp. 8-10.

Oke O L  1973  The mode of cyanide detoxification. In:  Nesel  B.; MacIntyre  R  (eds ) chronic cassava toxicity. Proc. Interd. Workshop, London, England, 29-30 Jan.1973. IDRC-010e, pp. 97-104.

Portela J and  Maner J H 1972  (B L Nestel and R MacIntyre, eds). Chronic Cassava Toxicity. International Development Research Centre, London, Monograph No. 010e, pp.113-120

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