Evaluation of ensiled groundnut leaves
for fattening pigs

Vo Thi Kim Thanh, Nguyen Thi Loc, Dao Thi Phuong
 and  Phung Thi Luu

Hue College of Agriculture and Forestry, Hue University

Abstract

A survey was carried out in Huong Van village near Hue focusing on the production and utilization of groundnut leaves. The main findings were that there were over 600 tonnes of the leaves produced annually, most of which are not utilized. In an on-station experiment the leaves were ensiled with 5, 10 or 15% (fresh basis) of fresh cassava roots (FCR) or 5, 10 or 15% of molasses. After 56 days of ensiling the quality of all silages was acceptable in terms of odour and appearance, and pH was below 4.35.  pH values were lower and solubility higher for the silages made with molasses. There were no significant changes in DM or crude protein concentrations with time of ensiling, or between additives.

An on-farm feeding trial was carried out with 40 Mong Cai x Large White pigs fed either a traditional (control) diet, or an experimental diet in which 50% of the crude protein  supplied by fermented fish was replaced by ensiled groundnut leaves (EGL50). Daily liveweight gains were not affected by treatment, although the feed cost/kg liveweight gain was 22% lower for the experimental diet.

Key words: Ensiling, groundnut leaves, molasses, cassava roots, fattening pigs

Introduction

Pigs are commonly kept as a domestic animal in almost all households in the rural areas in Vietnam. Rice bran, cassava and vegetables are the main feedstuffs, although these feed resources are low in protein and often expensive. Groundnut is the main cash crop in many parts of central Vietnam; the nuts are used for oil and the residue after extraction as a protein resource. However, the leaves have not been used to any great extent. The groundnuts are harvested in April or May, and a second crop is taken in July or August, the harvesting taking only 2 or 3 weeks. There are about 3 tonnes of groundnut leaves/ha/year (from the 2 crops) available in Huong Van village. Some farmers dry these leaves, and store them to feed to their animals, although it is difficult to dry the leaves during the rainy season, and ensiling could be a more appropriate method of preservation.

Methods and materials

The research was carried out from April 1998 to February 1999 at the Hue College of Agriculture and Forestry and in Huong Van village, Huong Tra district, Thua Thien Hue Province.

On-station research

The objective of the research was to find the most appropriate method of preservation of groundnut leaves and to determine the nutritive value of the leaves preserved by different techniques. The fresh groundnut leaves (GL) were ensiled with molasses (ML) or fresh cassava roots (FCR) in the following proportions:

·        GL mixed with 10%, 20% and  30% FCR (fresh basis)

·        GL mixed with 5%, 10% and 15% ML (fresh basis)

The silages were analyzed for pH, DM, crude protein, solubility and ash content at 0, 7, 14, 21, 28 and 56 days after ensiling. The best preservation method was selected for later evaluation in on-farm trials. The criteria for identifying the best quality silage were:

·        Low pH during storage

·        High nutritive value

·        Good smell.

On- farm research

Survey

A survey was conducted in Huong van village to determine the production of groundnuts in terms of area, season, yield, proportion of leaves and the utilization of these products.

Feeding trial

Forty crossbred piglets with a mean initial liveweight of 16 kg were allocated to 10 households in Huong van village. Each household raised four pigs, two (one castrate and one female) on a traditional diet (Ctrl) and two on the experimental diet (EGL50), in which 50% of the protein supplied by fermented fish in the traditional diet was replaced by ensiled groundnut leaves (EGL). The pigs were weighed every month during the experimental period (6 months). The total feed consumed was recorded. The amounts of the diet ingredients and daily DM, CP and calculated ME intakes are shown in Table 1.

Results

Survey

Huong Van village is an upland village of Huong Tra district, Thua Thien Hue Province, in Central Vietnam. It has a total land area of approximately 1,740 ha, of which total agricultural land is 464ha. In 1998, due to high groundnut prices in 1997, the farmers increased the groundnut area from 84 ha (1997) to 128 ha (1998). There are 2 groundnut crops in Huong Van village, the main crop from January to April and a second crop from May to August. Groundnut seeds are sold after harvesting and exported. The yield of groundnuts in Huong Van is around 0.9 tonnes seed/ha, and 3.08 tonnes leaves/ha. Therefore every year there are about 662 tonnes of GL available, which is currently underutilized. Some farmers dry these products and use as feed for cattle, while some feed them to pigs in fresh form. However, since the harvesting time is very short they cannot base their pig production on fresh leaves.

Nutritive value of silage

The pH dropped to around 4 one week after ensiling with both molasses (ML) and fresh cassava root (FCR), but the decrease was greater with molasses (Table 2). There were no effects of level of molasses or FRC on the pH. All treatments produced an acceptable silage in terms of smell and appearance.

The dry matter percentages did not change materially during the ensiling period (Table 3).

There were no consistent changes in crude protein concentration with time of ensiling (Table 4).

The measurements of dry matter soluble in water showed no consistent changes due to ensiling time but was lower for the FCR silage than for the ML silage, reflecting the higher fibre content of the cassava roots and also the fact that the starch would probably remain largely insoluble, compared with the soluble sugars in the molasses.

On-farm feeding trial

The feed offered per day, together with total intake for the different weight intervals, is given in Table 1. There were no treatment effects on total consumption or on ME  and crude protein intakes in any of the weight intervals.

The treatment effects on daily gain, feed conversion and feed costs are given in Table 6. The growth performance of the pigs was not affected by replacing 50% of the crude protein of the fermented fish and sweet potato leaves with ensiled groundnut leaves, but the cost of feed/kg gain was reduced by 22%.

Conclusions

Ensiling is a convenient way of preserving groundnut leaves without reducing their nutritive value. Groundnut leaves ensiled with freshly ground cassava root and with molasses  had low pH values, but the silage made with molasses had a higher solubility. The level of 5% molasses was sufficient for producing good quality silage, and was the cheapest and easiest treatment that can be applied on farms in Huong Van village, as molasses is readily available in the area.

Fattening pigs using ensiled groundnut leaves to replace 50% of the protein, normally provided by fermented fish, gave the same performance results as the traditional diet, but with a superior economic return. Based on these results the farmers can increase pig production and income by utilizing groundnut leaves that would otherwise be wasted.

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