The use of ensiled cassava leaves for feeding pigs on-farm in central Vietnam

Nguyen Thi Hoa Ly

HueUniversity of Agriculture and Forestry, Vietnam
lydohoai@dng.vnn.vn

Abstract

Cassava (Manihot esculenta Crantz) is the second most important food crop in Vietnam, and new high-yielding varieties, such as KM60, KM94 and KM98, and more sustainable production practices have increased the economic effectiveness of cassava production in Vietnam.

It was found that the inclusion of rice bran or cassava root meal as additives in the ensiling process at levels 5 or 10 % produced good quality silage that could be stored for at least five months. The HCN content of the ensiled cassava leaves decreased very quickly during the first 30 days, and was only from 10.4 - 13.2 % of the initial level at 90 days after ensiling. The inclusion of 15 % (as DM) ensiled cassava leaves in diets for growing pigs improved daily live weight gains (DWG) and the feed conversion ratio (FCR) and reduced the feed cost by 25 %. Supplementation with L-lysine and DL -methionine significantly improved DWG, feed intake and FCR in diets containing ensiled cassava roots and leaves. Diet with15 % ensiled cassava leaves (DM basis) supplemented with 0.2 % Lysine, 0.1 % DL-methionine and 0.1 % lysine and 0.05 % DL-methionine in the 20-50 kg and 50 -90 kg growth stages, respectively, resulted in the highest economic efficiency and can be recommended for crossbred pigs. A second experiment was conducted on farm in Huong Van village, Huong Tra District, Thua Thien Hue province to determine the effect on performance of different levels of ensiled cassava (KM94) leaves in the diets of growing pigs. There were four experimental diets, with inclusion of ensiled cassava (KM94) leaves at 0 %,10 %, 15% and 20 % of DM. It was found that, in diets for growing pigs 10 % to 20 % (of DM) of ensiled cassava leaves could be included in the diet without affecting the animals' health or overall performance and resulting in 8.0 - 13.8 % reductions in feed cost.

In conclusion, cassava leaves can be used as a protein supplement for feeding pigs. Using ensiled cassava leaves in the diet brings more benefit to farmers in Central Vietnam. Ensiling is the best method of preserving cassava when the harvest coincides with the rainy season; the technique is simple, cheap and suitable for farm conditions in Central Vietnam.

Key words: Cassava KM94 leaves, hydrogen cyanide, ensiled cassava leaves (ECL), lysine, methionine, growing pigs, daily weight gain, feed conversion ratio, feed cost.

Introduction

In Viet Nam the agriculture is based mainly on small- scale farming systems. The characteristics of these systems are small farms, integrated crop-livestock systems, low capital input and low economic efficiency. Pig production is an important part of these farming systems, and the pig population in 2005 was 27.43 million animals. The main feeds for pigs are rice bran, maize, cassava meal and vegetables. Cassava, maize and rice bran are rich in energy but have low contents of protein and essential amino acids. The conventional protein supplements in the region are soybean meal, groundnut cake, and fishmeal, but they are relatively expensive and not always available in the villages.

Therefore smallholder pig production is mainly based on agricultural by-products. It is clear that sustainable livestock development by making better use of locally available feed resource is an urgent priority.

Cassava (Manihot esculenta Crantz) is the second most important food crop in Vietnam after rice in terms of total production. In 2004 root production was about 5.6 million tonnes, some of which is used for animal feeding. In 2004/2005 more than 380 000ha, which is about 50 % of the total cassava area in the country, was planted with new cassava varieties, such as KM60, KM94, KM95 and KM98. New high-yielding cassava varieties usually have a high HCN content. At root harvest time, yield of fresh foliage of KM94 is about 5-9 tons/ha (Hoa Ly 2005). Cassava leaves of KM94 variety have a high crude protein concentration of between 25.0-34.7 % in DM (Phuc et al 2001; Hoa Ly et al 2005), and thus have a good potential as a protein source for animal feeding. The greatest limitation to the use of cassava leaves as animal feed is the high HCN content. The most common procedures for reducing the cyanide content are sun- drying and ensiling (Phuc et al 2001, 2005; Wanapat 2001; Khieu Borin et al 2005).

In the rainy season it is difficult to sun-dry, and so making silage is the most appropriate method to preserve cassava roots and leaves and reduce the toxicity of HCN. Fresh KM 94 cassava leaves have a very high HCN contain (1745 mg/kg DM), so it is necessary to find appropriate methods to process the leaves and so be able to use KM 94 for animal feeding. However, the protein from cassava leaves is low in the amino acids lysine and methionine. Further research on using cassava silage for feeding animals is required

The object of these experiments was to identify appropriate preservation and processing methods of cassava leaves and to evaluate the economic efficiency of using ensiled cassava leaves for pig feeding under farm conditions in Central Vietnam.

Experiment 1. Evaluation on station of the effect of time of wilting and additives on the quality of cassava leaf (KM94) silage

Processing method

The fresh leaves of cassava KM 94 were collected at time of root harvest and spread out on the floor for wilting. The fresh leaves, and at 12 hours and 24 hours after wilting, were analysed for DM, CP and HCN content. After 24 hours wilting the leaves were separated from the stems and petioles, chopped into small pieces (2 - 3 cm), mixed with 0.5 % salt and additives (rice bran or cassava root meal at 5 or 10% levels) and sealed in plastic bags. The treatments were:

• 5CRM: Cassava leaves (KM 94 )+ 0.5 % NaCl + 5 % Cassava root meal

• 10CRM: Cassava leaves (KM 94 )+ 0.5 % NaCl + 10 % Cassava root meal

• 5RB: Cassava leaves (KM 94) + 0.5 % NaCl + 5 % Rice bran

• 10RB: Cassava leaves (KM 94) + 0.5 % NaCl + 10 % Rice bran

Silage samples were taken after 0, 30, 60 and 90 days of ensiling and analyzed for dry matter (DM), crude protein (CP) and HCN (AOAC 1984).

Results and Discussion

The DM of fresh cassava (KM94) leaves increased significantly after wilting for 12 h or 24 h (table 1). The aim in wilting is to reduce the moisture content and HCN in cassava leaves. Pre-wilting is a very important step to reduce the moisture content of fermenting material. After wilting for 24 hours, the DM % of the cassava leaves was 37.8 %, which is suitable for ensiling. Higher levels of moisture will cause the sugar and colloidal- matter in plant liquid to be diluted, which will damage the lactic acid bacteria and cause silage to be putrid.

The HCN content of cassava KM94 leaves decreased after wilting (Table 1). The HCN content of the fresh leaves was 1745 mg/kg DM, that was reduced 1313 mg and 885 mg/kg DM after wilting for 12 and 24 hours, respectively. The HCN content thus was about 75 -51 % of the initial level at 12 and 24 hours wilting, respectively.

The crude protein content (Table 2) in all treatments with additives decreased significantly from 0 to 30 days of ensiling and then decreased slightly from 30 days until 90 days ensiling. Concentration of crude protein in the KM94 silage fell for all treatments by 3-5 %, probably as a result of bacterial degradation. Plant enzymes also bring about proteolysis and the production of amino acids and peptides from the protein of the original material.

The HCN content of the ensiled leaves decreased very quickly from 0 days (after leaf wilting 24 hours) to 30 days and then further decreased until 90 days after ensiling (Table 3). The HCN content of the fresh cassava leaves was 1745 mg/kg DM, and was reduced to 885 mg/kg DM after 24 hours of wilting, when the HCN content was only about 51 % of the initial level. Then at 90 days after ensiling, the HCN content of the cassava leaves had fallen to 181- 231 mg/kg DM, only about 10.4 - 13.2 % of the initial level.

Wilting for 24 h and then ensiling, could be a suitable alternative way of preserving KM94 cassava leaves when the harvest of cassava coincides with the rainy season. The technique is simple, cheap and suitable for farm conditions in Central Vietnam.

Experiment 2. Ensiled cassava leaves for feeding growing pigs

Location

The two experiments were carried out on household farms in Huong van village, Huong tra District, Thua Thien Hue province .

Experiment 2.1. Effect on performance of including ensiled cassava leaves in the diet of growing pigs

Materials and methods

Four families in Huong van commune raised a total 16 pigs (each farmer kept 4 pigs), all crossbreeds between Mong Cai and Large White, with initial live weights of around 24 -25 kg. Two pigs on each farm were housed together and fed the control diet (a traditional diet) which contained rice bran, fermented fish, cassava meal and sweet potato vines, while the other two pigs were fed the experimental diet: 85 % control diet + 15 % ECL (ensiled cassava leaves). The experiment lasted for 90 days.

Results and discussion

The effect of using ECL in growing pig diets is shown in Table 4. Daily weight gain was higher and feed conversion ratio lower in the pigs given the ECL diet compared to the control diet (P<0.05). Feed cost was 25.62 % lower with ECL supplementation ( P<0.001).

Experiment 2.2: Effect of supplementation of L-lysine and DL-methionine on the utilization of diets containing ensiled cassava leaves as protein source for pigs

Materials and methods

Animals and experimental design and feeding

Each of three farmers was allocated 8 pigs (Mong cai x Large White) with a range in live weight from 19.6 -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, Vietnam (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 and weighed. Drinking water was available ad-libitum.

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

The control (basal) diet consisted of rice bran, maize, ensiled cassava root, fishmeal, and ensiled cassava leaves (Table 5 and 6). The basal diet was compounded to contain in Phase 1: 3026 kcal/kg ME, 14.9 % CP; 0.7 % lysine and 0.28 % methionine and in Phase 2: 3010 kcal/kg ME and 12.81 % 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).

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, and daily weight gain, daily feed intake, feed conversion ratio and feed cost/kg live weigh gain calculated for each treatment. The data collected were analyzed by the General Linear Model (GLM) procedure in the ANOVA program of Minitab version 13.

Results and discussion

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

The effect of supplementation with L-lysine and DL-methionine in the diet on the performance of growing pigs is shown in Table 7. Final live weight and DWG were highest at the two highest levels of supplementation (High AA and Very High AA) compared to the Low - and Medium AA treatment . The feed conversion ratio was poorer in the Low AA (control) treatment compared to the other three diets. The results demonstrate that increasing the level of supplementary AA in diets of growing pigs improved daily gain and feed conversion. This is in agreement with the results of various other studies on amino acid supplementation of growing pig diets (Portela and Maner 1972; Nguyen Thi Loc 2003).

Feed cost

The data in Table 7 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, thus gave the highest economical efficiency and can be recommended for F1 (MC x LW) growing pigs when diets are used with high levels of 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.

Experiment 2.3. Effect of level of ensiled cassava KM94 leaves in the diet on the performance and economic efficiency of growing pigs in Central Vietnam

Materials and methods

Animals and experimental design and feeding

The experiment was carried out in three households in Huong Van village, Huong Tra District, Thua Thien Hue province from December 2004 to May 2005. Three households were selected to carry out the experiment, and raised a total of 24 crossbred pigs (MC x LW) with average initial weight of about 23 - 24 kg. Each farmer was allocated 8 pigs randomly distributed into four treatments, with 2 pigs in each pen. The trials were designed as a complete randomized block with four levels of ensiled cassava (KM94) leaves: 0, 10%, 15 % and 20 % ensiled cassava leaves (in DM) in diets. The control (basal) diet contained rice bran, maize meal, ensiled cassava roots, fishmeal and sweet potato vine, without ensiled cassava leaves. The four diets were compounded to contain: 3000 kcal/kg ME and 14 % CP, with 0.65 % L-lysine and 0.25 % DL-methionine in Phase 1 (pigs 20 -50 kg) and in Phase 2 (pigs 50 -90 kg): 3000 kcal/kg ME and 12 % CP, 0.55 % L-lysine and 0.23 % DL-methionine (as DM), respectively. A vitamin and mineral premix was added (0.5 % of DM) according to requirements given by NRC (1998).

Results and discussion

Final live weight, daily weight gain and feed conversion ratio

The data in Table 8 indicate that final live weight and daily weight gain tended to decrease as the level of ensiled cassava leaves increased. However, there were no significant differences in final live weight and daily weight gain among the experimental diets (P>0.05). Similarly, there were no significant differences in DM intake among the experimental diets. The feed conversion ratios (FCR) increased slightly at the higher levels of ensiled KM94 leaves in the diet, but the differences were not significant (P= 0.63).

Feed cost

There were no significant differences in feed cost/kg weight gain among treatments (P = 0.47). However, this parameter was lower in the ECL diets than in the control diet. The feed cost tended to decrease as levels of ensiled cassava leaves increased. Including 10%, 15 % and 20 % ensiled cassava leaves in the diet reduced the feed cost by 8.0 %, 9.3 % and 13.8 %, respectively. This indicates that including ensiled cassava leaves as a protein source for feeding pigs can reduce feed costs under small farm conditions in Central Vietnam.

Conclusions

• Using various additives in the ensiling process of cassava KM94 leaves, it was found that the inclusion of rice bran or cassava root meal at levels 5 or 10 % produces a good quality silage that can be stored for at least five months. The HCN content of ensiled KM94 cassava leaves was only from 10.4-13.2 % of the initial level at 90 days after ensiling.

• Using 15 % of DM inclusion of ECL in the pig diets containing 30 % ECR (as DM) as replacement for sweet potato vines and partial replacement for fish meal in diets for growing pigs did not effect the growth rate but reduced feed cost/kg gain by 26.8 %.

• A diet containing 15 % ensiled cassava leaves with supplementation of 0.2 % L-lysine and 0.1 % DL- methionine, and 0.1 % L-lysine and 0.05 % DL-methionine, gave the highest economical efficiency and can be recommended for crossbred pigs of 20-50 kg and 50 -90 kg live weight, respectively.

• The inclusion of 10 % to 20 % (as DM) of ensiled KM94cassava leaves in diets for growing pigs did not affect the animals' health or overall performance and resulted in a 8.0 % - 13.8 % reductions in feed cost.

• Ensiled cassava leaves can be used as a protein supplement for feeding pigs and will bring more benefit to farmers.

References

AOAC 1984:Official methods of analysis. 12^th Ed. Association of Official Analytical Chemists, Washington, D.C.

Bui Huy Nhu Phuc, Ogle R B and Lindberg J E 2001: Nutritive value of cassava leaves for monogastric animals. Proceedings, International Workshop "Current Research and Development on Use Of Cassava as Animal Feed" held in Khon Kaen University, Thailand. July 23- 24, 2001.

Bui Huy Nhu Phuc 2005: Effects of cassava leaves on the performance of growing pigs. Proceedings, Regional seminar-workshop on " Sustainable Livestock Based Agriculture in the Lower Mekong Basin". Organized and Sponsored by Cantho University and MEKARN Programme held in Cantho University, Vietnam. May 23-25, 2005.

Khieu Borin, Chhay Ty, Preston T R and Ogle R B 2005: Research on the use of cassava leave for livestock feeding in Cambodia. Proceedings of the Regional Workshop on "The Use of Cassava Roots and Leaves for On-Farm Animal feeding", organized by CIAT, and held in Hue University of Agriculture and Forestry, Vietnam. January 17 -19, 2005.

Nguyen Thi Hoa Ly, Le Van An, Le Van Phuoc and Dao Thi Phuong 2001: Effect on using ensiled cassava roots and ensiled cassava leaves under village conditions. Proceeding National Seminar Workshop on research and extension Cassava in Vietnam held in Hue City, Vietnam. 20 - 25 August 2001.

Nguyen Thi Hoa Ly and Le Duc Ngoan 2005: Evaluation of the economical efficiency of using cassava leaves (variety KM94) in diets for pigs in Central Vietnam. In Proceedings of Regional seminar-workshop on" Sustainable Livestock Based Agriculture in the Lower Mekong Basin". Organized and Sponsored by Cantho University and MEKARN Programme held in Cantho University, Vietnam. May 23-25, 2005. http://www.mekarn.org/proctu/hoa34.htm

Nguyen Thi Hoa Ly 2005: 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. In Proceedings Regional seminar-workshop on" Sustainable Livestock Based Agriculture in the Lower Mekong Basin". Organized and Sponsored by Cantho University and MEKARN Programme held in Cantho University, Vietnam. May 23-25, 2005.http://www.mekarn.org/proctu/hoal36.htm

Nguyen Thi Loc and Le Khac Huy 2003:Effect of DL - methionine supplementation levels in ensiled cassava root based -diets on the performance and economic efficiency for F1 (MC x LW) fattening pigs. Proceedings of seminar-workshop "Sustainable Livestock Production on Local Feed Resources". SAREC- HUAF, held in Hue City, Vietnam. 25 - 27 March 2003. Agricultural Publishing House, Ho Chi Minh City.

Portels J and Maner J H 1972: Chronic Cassava Toxicity. International Development Research Centre, London, Monograph.

Wanapat M 2001: Role of cassava hay as animal feed in the tropics. Proceedings of International Workshop "Current Research and Development on Use Of Cassava as Animal Feed" held in Khon Kaen University, Thailand. July 23- 24, 2001.

Go to top