Evaluation of some unconventional trees/plants as ruminant feeds in Central Vietnam

Abstract

This investigation was aimed at evaluating foliage production and nutritive value of Muntingia calabuara,  Hibiscus rosa sinensis L, Mulberry (Morus alba) and Trichanthera gigantea based on chemical composition, rumen degradability and gas production. The trees were planted from stem cuttings at spacing of  0.2*0.5m for Mulberry and Trichanthera,  0.2*1.0m for Hibiscus and 1*1 for  Muntingia calabuara, which was planted from seedlings. The plot size was 25m² for each of the trees.

Introduction

In central Vietnam, the population of ruminants occupy around 45% of the total live stock in the whole country. Because of harsh conditions (high temperature, low rainfall in the dry season), shortage of animal feed is a big problem for livestock development, particularly for grazing cattle. The main feed supplement for animals during the dry season is rice and maize straws and various crop residues. Quantity and quality of feed is usually limited, particularly the protein content. This is reflected in poor animal performance.

In recent years, there have been many studies on the of tree foliages as supplements for live stock (Leng 1997). In central Vietnam, there are some indigenous trees that can be used as forages. Among these are:

• "Trung Ca" (Muntingia calabura) belonging to the family Elaeocarpacae. It can grow everywhere (sandy land, humid areas, and high land area) and is well adapted to the dry season in central Vietnam. The farmers use it as shade tree around the homestead, and along the roads. Trung Ca is a tall tree with a large canopy of leaves but it has not been used for animals.

• "Dam But"  (Hibiscus rosa-sinensis L.) belongs to the Malvacae family. It adapts and grows well during the dry season in Central Vietnam. The most common planting method is by stem cuttings. The tree is grown as a live fence. In some areas "Dam But" is fed to rabbits and goats.

• Mulberry (Morus spp) belongs to the Moraceae Family (Subtype Angiosperms; Class Dicotyledons; Subclass Urticales) and there are several species. Mulberry leaves have been the traditional feed for silk worms. In Vietnam there are many varieties with high yield. In recent years, the area of Mulberry has decreased due to reduced activities in silk processing and limited market.  The traditional way of using mulberry as animal feed in silk-producing areas is to feed ruminants with the residue left by the silk worm.

• Trichanthera gigantea is a tree of the Acanthaceae family and is apparently native to the Andean foothills of Colombia (Rosales 1997). The tree was introduced into Vietnam in 1991 and has been readily adopted by farmers throughout the country because of its tolerance to a wide range of ecological conditions and apparent resistance to pest and diseases (Nguyen Ngoc Ha and Phan Thi Phan 1993; Nguyen Thi Hong Nhan et al 1996; Nguyen Thi Hong Nhan and Nguyen van Hon 1999; Nguyen Xuan Ba, personal observations).

The research described in this paper was aimed at the evaluation of the agronomic characteristics and the nutritive value of the above trees as ruminant feeds.

Materials and methods

The experiment was started in September, 2001 in the Hue University of Agriculture and Forestry experimental farm in Hue City. The climate is tropical monsoon with a yearly rainfall around 3415cm, most of which occurs from August to January. The temperature range is 21 to 29 ºC. Air humidity varies in the range 79 to 91%. The soil is sandy loam with the pH around 5.5 in the topsoil.

The above species of shrubs and trees were planted at the same time in September, 2001. The trees were planted from stem cuttings at spacing of  0.2*0.5m for Mulberry and Trichanthera,  0.2*1.0m for Hibiscus and 1*1 for  Muntingia calabuara,  which was planted by seedlings when their height was about 50 cm. The plot size was 25m² for each of the trees. The foliages were harvested when the plants reached 1 m height except for "Trung Ca" which was 2.5 m. The cutting point was  50 cm above ground level.

Samples of the foliages (leaves, petioles and young stems) were collected at harvest time and analysed according to the official methods of AOAC (1990). Cell wall components (NDF, ADF) were determined according to Van Soest et al (1991).  Rumen degradability was determined according to Ørskov et al (1980) using three fistulated crossbred cattle. In vitro  gas production method was measured following the method of Menke and Steingass (1988). Rumen degradation and gas production parameters were estimated by fitting the exponential equation of McDonald (1981):
 

P = a + b (1 - e ^-ct)

using the F-curve software running on Microsoft Xcel.