Effect of supplementation of l-lysine and dl-methionine on the utilization of diets containing ensiled cassava leaves as a protein source for pigs in central Vietnam

Nguyen Thi Hoa Ly

Hue University of Agriculture and Forestry
Hue City, Vietnam
lydohoai@dng.vnn.vn

Abstract

Three farmers were each allocated 8 crossbred (Mong Cai x Large White) pigs with range of initial live weights of 19.6 to 20.8 kg, randomly distributed into four treatments (pens), with two pigs in each pen. Four experiment diets were formulated according to the two growing phases, 20 -50 kg (Phase 1) and 50 - 90 kg (Phase 2). The four diets were: a basal (CTL) diet containing 15 % ensiled cassava leaves (ECL) (as DM) supplemented with different amounts of amino acids: Low AA: Basal (control) diet containing 3026 kcal ME, 14.9 % CP, 0.7 % lysine and 0.28 % methionine (Phase 1) and 3010 kcal ME, 12.8 % CP, 0.58 % lysine and 0.24 % methionine (Phase 2). Medium AA: Basal diet + 0.1 % L-lysine and 0.05 % DL - methionine (Phase 1) and 0.05 % L-lysine and 0.03 % DL - methionine (Phase 2). High AA: Basal diet + 0.2 % L-lysine and 0.1 % DL-methionine (Phase 1) and 0.1 % L-lysine: 0.05 % DL-methionine (Phase 2). Very high AA: Basal diet + 0.3 % L-lysine and 0.15 % DL-methionine (Phase 1) and 0.15 % L-lysine and 0.08 % DL-methionine (Phase 2).

Increasing levels of inclusion of L-lysine and DL-methionine improved daily live weight gain, feed intake and feed conversion ratio. Diet High AA gave the highest economical efficiency and can be recommended for crossbred pigs of 20-50 kg and 50 -90 kg, respectively. The feed cost / kg gain was highest for the Very High AA treatment because of the high cost of L-lysine and DL-methionine.

Keywords: Ensiled cassava leaves, amino acids, lysine, methionine, daily weight gain, feed conversion ratio, feed cost

Introduction

In Vietnam, cassava ( Manihot esculenta Crantz) is the second most important food crop after rice in terms of total production. In 2002 root production was about 3.15 million tonnes (Pham Van Bien et al 2003), some of which was used for animal feeding. In 2001/2002 more than 300 thousand ha were planted with cassava, of which 94,500 ha was planted with new varieties such as: KM60, KM94, KM95, KM 95 -3 and KM98. This corresponds to about 33 % of the total cassava area in the country (Pham Van Bien et al 2002). These new, high -yield cassava varieties usually have high HCN content.

At root harvesting time, fresh leaf yield is about 5 tonnes/ha (Mui, 1994) and foliage yield about 7 tonnes / ha (Ngoan and Duong 1993). Cassava leaves have a high crude protein concentration (from 16.7 to 39.8 %, Allen 1984), although the leaves are not used practically for feeding animals. However, in spite of the high crude protein content,  the high cyanide content (Buitrago 1990) and an imbalance of the essential amino acids lysine and methionine (Ngoan 2001) limit their use in pig diets.

The most common procedures for reducing the cyanide content are sun-drying and ensiling, which give good results (Wanapat 2001; Duong Thanh Liem et al 2000; Nguyen Thi Hoa Ly et al 1999, 2000, 2001; Nguyen Thi Loc et al 2001, 2003). Recent research (Nguyen Thi Hoa Ly et al 1999; 2000, 2001; Nguyen Thi Loc et al 2001, 2003)  showed that ensiling appears to be the best method of preserving cassava leaves, and that ensiled cassava leaf can replace a part of the fishmeal in diets for pigs, with better economic returns. However, the protein from cassava leaves is low in the amino acids lysine and methionine. L -lysine and methionine supplementation have been reported to significantly improve protein utilization in pigs (Job 1975). Portela and Maner (1972) reported that pigs fed diets with 55 % cassava root meal supplemented by 0.15 % DL-methionine had higher daily weight gains and better feed conversion in comparison with the un-supplemented control or with 0.2 % methionine added. In addition to the amino acid imbalance, pigs consuming diets containing cassava leaves have lower serum thiocyanate concentrations as the animals are unable to adequately detoxify cyanide (Tewe 1992). Supplementation with DL-methionine has been reported to be necessary for the detoxification of cyanide.

Based on this background, an experiment was carried out to evaluate the effect of synthetic L-lysine and DL-methionine supplementation to diets containing ensiled cassava leaves as a protein source for pigs. The study aimed at improving the amino acid balance of the diet, thus increasing the economic efficiency of growing pigs.
 

Materials and methods

Location

The experiment was carried out in three households in Huong Van village, Huong Tra District, Thua Thien Hue province, from December 2003 to April 2004.

Ensiling cassava leaves

The fresh cassava leaves were collected 2-3 weeks before harvesting or when the roots were harvested. The cassava leaves were dried under sunlight, chopped into small pieces (2-3 cm) and mixed with 0.5 % salt and 10 % rice bran (fresh basis), and stored in sealed plastic bags 50-60 days before feeding.

Animals, experimental design and feeding

Each of three farmers was allocated 8 pigs (Mong Cai x Large White) with range in live weight from 19.6 to 20.8 kg.  randomly distributed into four treatments (pens), with two pigs in each pen. The pigs were vaccinated against hog cholera and Pasteurellosis, and de-wormed 2 weeks before starting the experiment. The diets were formulated according to the two growing phases, 20 -50 kg (Phase 1) and 50 -90 kg (Phase 2). The diets were fed according to a restricted allowance recommended by the National Institute of Animal Husbandry (NIAH 2001). The experiment lasted 90 days. The diets were distributed equally into 3 meals per day. Refusals were collected the following morning before the first meal. Drinking water was available ad libitum.

The four dietary treatments in Phase 1 and Phase 2, respectively, were:

• Low AA: Basal (control) diet containing 3026 kcal ME, 14.9 % CP, 0.7 % lysine and 0.28 % methionine (Phase 1) and 3010 kcal ME, 12.8 % CP, 0.58 % lysine and 0.24 % methionine (Phase 2).

• Medium AA: Basal diet + 0.1 % L - lysine and 0.05 % DL - methionine (Phase 1) and 0.05 % L-lysine and 0.03 % DL - methionine (Phase 2).

• High AA: Basal diet + 0.2 % L - lysine and 0.1 % DL - methionine (Phase 1) and 0.1 % L-lysine: 0.05 % DL -methionine (Phase 2).

• Very high AA: Basal diet + 0.3 % L - lysine and 0.15 % DL - methionine (Phase 1) and 0.15 % L-lysine and 0.08 % DL - methionine (Phase 2).

The experimental design is shown in Table 1.

Table 1: Design of experiment
	Low AA	Medium AA	High AA	Very high AA
No. of pigs	6	6	6	6
Initial LW (kg)	20.1	20	20.8	19.6
AA levels	Low	Medium	High	Very high
Phase 1 ( 20 -50 kg)
L - Lys Sup.(as % of DM)	-	0.1	0.2	0.3
DL - Met Sup. (as % of DM)	-	0.05	0.1	0.15
Phase 2 ( 50 - 90 kg)
L - Lys Sup.(as % of DM)	-	0.05	0.1	0.15
DL - Met Sup. (as % of DM)	-	0.03	0.05	0.08

The control (basal) diet consisted of rice bran, maize, ensiled cassava root, fishmeal, and ensiled cassava leaves (Tables 2 and 3). The basal diet was compounded to contain in Phase 1: 3026 kcal ME, 14.9 % CP; 0.70 % lysine and 0.28 % methionine and in Phase 2: 3010 kcal ME, 12.8 % CP, 0.58 % lysine and 0.24 % methionine (as DM).

Chemical analyses

The feedstuffs in the experimental diets were analyzed for dry matter (DM), crude protein (CP), crude fibre (CF) and HCN (AOAC 1984).

Table 3. Ingredient content and chemical composition of the control diet (% of DM)
	20- 50 kg	50- 90 kg
Rice bran	40	35
Yellow maize	20	20
Ensiled cassava Root	17	25
Ensiled cassava Leaves	15	15
Fish meal	8	5
Composition ( % in DM)
ME (kcal/kg DM)	3026	3010
Crude protein	14.89	12.81
Crude fibre	9.42	8.95
HCN (mg/kg DM)	36.4	41.1
Lysine	0.7	0.58
Methionine	0.28	0.24

Measurements

Feed consumption was determined by weighing the mounts given and subtracting any feed remaining the following morning. The pigs were individually weighed initially, monthly and at slaughter. Daily weight gain, daily feed intake, feed conversion ratio and feed cost/kg live weigh gain were calculated for each treatment.

The data collected were analyzed by the General Linear Model (GLM) procedure in the ANOVA program of Minitab version 13. Sources of cariaton were treatments, farms and error.
 

Results and discussion

Final live weight, daily weight gain (DWG), feed intake (FI) and feed conversion ratio (FCR)

The effect of supplementation with L-lysine and DL-methionine in diets containing 15 % (in DM) ensiled cassava leaves on the performance of growing pigs is shown in Table 4 and Figure 1. Final live weight and daily weight gain was highest at the two highest levels of supplementation (High AA and Very high AA) compared to the Low- and Medium AA treatments (Figure 1). The feed conversion ratio was poorer in the Low AA (Control) treatment than in the other three diets. The results demonstrate that increasing the level of supplementary AA in diets of growing pigs improved daily gains and feed conversion. This is in agreement with the results of various other studies on amino acid supplementation of growing pig diets (Job 1975; Portela and Maner 1972; Nguyen Thi Loc 2003).

 

Figure 1. Effect of increasing level of supplementary L-lysine and DL-methionine on
the growth rate of growing pigs fed diets including 15 % (in DM) of ensiled cassava leaves

Feed cost

The data in Table 4 show that feed cost/kg gain for the " high AA" level treatment tended to be lower (P=0.099) than for the other three treatments and was somewhat higher  for the Very High AA treatment due to the high cost of the synthetic amino acids. The diet with supplementation of 0.2 % L-lysine and 0.1 % DL-methionine, and 0.1 % L-lysine and 0.05 % DL-methionine in the growing and finishing phases, respectively, gave the highest economical efficiency and can be recommended for F1 (MC x LW) growing pigs when fed diets contain ensiled cassava leaves.

Similar findings were reported by Nguyen Thi Loc (2003) who recommended supplementation with 0.2 % DL - methionine in diets based on ensiled cassava roots  for F1 (MC x LW) fattening pigs to give improved live weight gain, feed conversion ratio and feed cost.

Conclusions

• Supplementation of a diet containing ensiled cassava leaves with 0.2 % L-lysine and 0.1 % DL-methionine, and 0.1 % L-lysine and 0.05 % DL- methionine, for growing pigs of 20-50 kg and 50 -90 kg, respectively, gave the highest economical efficiency .

• Ensiled cassava leaves can be used as a protein supplement for feeding pigs provided the diets contain adequate levels of lysine and methionine.

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