Chemical composition, digestibility and intake characteristics of some tropical foliage species used for goats

Daovy Kongmanila, T R Preston^* and Inger Ledin^**

Faculty of Agriculture, National University of Laos, Vientiane Capital, Lao PDR
daovyk@yahoo.com
^* Finca Ecológica, UTA-Colombia, AA #48, Socorro, Santander, Colombia
^* Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences
 PO Box 7024, 750 07 Uppsala, Sweden

Abstract

Chemical composition, digestibility, N retention and feed intake characteristics of some tropical foliage species used for local goats were studied.Twelve local male goats with an initial body weight (BW) of 14.6 kg and around 3.5 months of age, were randomly allocated to six treatments in a repeated randomized complete block design with 3 periods. The treatments were foliages from Erythrina (Erythrina variegata), Fig (Ficus racemosa), Jackfruit (Artocarpus heterophyllus), Jujube (Ziziphus jujuba Mill), Kapok (Ceiba pentandra) and Mango (Mangifera indica), which were offered ad libitum at the level of 130 % of the average daily feed intake.

The Erythrina foliage had a low content of DM and condensed tannins (CT) and a high concentration of crude protein (CP) in leaves plus petioles, 193 g/kg DM, and stem, while the Mango foliage had a low CP, 69 g/kg DM, and high DM content. The other foliages were intermediate between Erythrina and Mango. High content of CT was found in the leaves plus petioles of Jackfruit foliage and in the stem of Fig and Mango foliage. There was a significant difference in feed intake, nutrient intake, apparent digestibility and N retention between treatments (P<0.05), with Erythrina, Jackfruit and Kapok foliage being significantly higher in those parameters than Fig, Jujube and Mango foliage.

In a subsequent experiment, the Fig, Jujube and Mango foliages were offered ad libitum together with fresh water spinach at 0.5% of LW (DM basis).  DM and CP intake, apparent digestibility and N retention were all markedly increased compared to feeding these foliages as sole feeds in the previous experiment.

In a third experiment, the feed intake and selective behaviour of eight local male goats (15.7 kg and 7 months of age) were studied by following each goat during 9 hours per day with six foliages. Three types of foliage species: Erythrina, Jackfruit and Kapok foliage, were selected more often and more time was spent eating these foliages, resulting in higher total feed intake compared to Fig, Jujube and Mango foliage, but the Jujube foliage was preferred by some of the goats. The goats were very individual in their selective and intake behaviour. 

Key words: Behavior,  N retention, Erythrina, Fig, Jackfruit, Jujube, Kapok, Mango, Water spinach,   

Introduction

In the Lao PDR, more than 70% of the total production from livestock such as goats, cattle, pigs and poultry comes from smallholders using traditional management systems. The main feed resources for the ruminants are native grasses, legumes and tree leaves that are available in the natural grassland and forests (Phengsavanh.2003).

Goats have a habit of selecting their feed carefully when eating and are considered to be agile feeders (Dumont et al 1995; Ngwa et al..000). According to Steele (1996) goats are continuously searching for feed and are more satisfied when they have a whole range of different plants available including trees, shrubs and grasses. However, goats are also considered to be very fastidious and even when having a very large selection to choose between they will only consume the most nutritious feed available (Van Soest., 1982; Fajemisin et al 1996). According to Steele (1996) reported that shoots and leaves are preferred to stems when goats are allowed to select. Keskin et al. (2005) showed that goats can spend 26.6 % of their time eating (383 minutes in 24 hours).

There are many kinds of tree fodder, legumes and crops which are important protein resources, for instance foliage from Leucaena, Erythrina, Jackfruit, Kapok and Jujube, sweet potato vines and water spinach. Normally, these green plants are used as traditional feeds in diets for animals, but little is known about their nutritive value, especially the protein availability. Some foliages have been researched, but there are still many types of foliage commonly used as feeds that have not been characterized properly. For example foliage from Jackfruit (Artocarpus heterophyllus) has been extensively researched in tropical countries. Nguyen Thi Hong Nhan and Preston (1997) found that intake of fresh Jackfruit leaves was higher when fed as a sole feed (3.9 kg/day) than when a supplement of sugar cane juice at levels up to 2 kg/day was given (3.5 kg/day) to dairy goats.

Also Erythrina variegata has been studied to some degree. Simbaya (2002) reported that Erythrina contains 258 g CP and 14.4 MJ per kg DM, which is a high content of CP when compared to other fodder tree and shrub species. Aregheore and Perera (2004) and Kibria et al. (1994) suggested that Erythrina could be used as a protein supplement to improve the nutritional quality of maize stover fed to mature goats, since it has significantly higher digestibility of DM, CP, NDF, OM and energy than Leucaena and Gliricidia.

Kapok (Ceiba pentandra) is a multipurpose tree, which, as the fruit bursts open, exposes a cotton like substance. The seeds, leaves, bark and resin from the Kapok tree are used as traditional medicine for dysentery, fevers, venereal diseases, asthma, menstruation bleeding and kidney diseases. The leaves can be used for animal feed and contain 186 g CP and 884 g OM per kg DM. It has the potential to increase the DM digestibility and voluntary intake of low quality basal diets by supplying a valuable protein source (Theng Kouch et al 2005).

Mango (Mangifera indica) is native to South Asia and is a multipurpose tree. The fruits and the foliage are not only used as food and feed but have also medicinal uses for humans. The foliage is a good potential source of forage to ruminants since it is green all the year round. According to Ajayi et al. (2005) Mango leaves contain 204 g CP/kg DM and when Mango leaves and concentrate were fed as a supplement to a Panicum maximum based diet, DM and CP intake increased as well as daily liveweight gain to 44.6 g/d.

Some foliages are known to be preferred by goats e.g. Jujube (Ziziphus jujuba Mill), but there is little or no research available. According to Morton (1987) and Reich (1991) fresh Jujube leaves contain a saponin, ziziphin, and from dried leaves a sweetness-inhibiting saponin could be extracted. Nath et al. (1996) reported that Jujube leaves are a rich source of protein and minerals with 140 g CP, 28 g Ca and 1.4 g P per kg DM. Fig (Ficus racemosa) is also an available tree in tropical areas. Schurrie (1990) reported that Fig leaves are related to Jackfruit, Mulberry (Morus spp.) and Chinese Mulberry (Cudrania tricuspidata). According to data analysis from the Faculty of Agriculture Laboratory, NUoL, Laos, Fig foliage has high content of CP, 193 g/kg DM, and 170 g/kg DM of crude fiber.

Water spinach (Ipomoea aquatica) is another plant which produces high yields of protein-rich biomass. Water spinach has a high nutritive value for humans and also for animals such as rabbits (Pok Samkol et al 2006), pigs (Chhay Ty and Preston 2005) and goats. According to Peng Buntha and Chhay Ty (2006) the N intake of local goats was 8.84 g/day when fed fresh water spinach, which is higher than when feeding cassava foliage, guinea grass or stylo. Dry matter and N intakes were increased linearly by supplementation with water spinach by 40% compared to feeding cassava alone (Pathoummalangsy and Preston.2006), and water spinach also increased DM digestibility and N retention in local goats.

The aim of these experiments was to analyses the chemical composition of some foliages available for goats and compare intake, digestibility, nitrogen retention and selective behaviour when feeding these foliages either as a sole feed or for foliages with low intake and digestibility, together with water spinach.

Material and methods

Location and climate

The experiments were conducted in the farm of the Livestock and Fisheries Department, Faculty of Agriculture, National University of Laos, 35 km south of Vientiane, Lao PDR. The climate in this area is tropical monsoon with a rainy season between May and October and a dry season from November to April. Average annual rainfall is 2000 mm/year. The two trials were conducted during June to December 2006.

Experiment 1 and 2: Intake and digestibility trail

Animals and management

The animals used in the two experiments were 16 local male growing goats, 12 goats for the first digestibility experiment and 4 goats for the second digestibility experiment. The goats were bought in the area around the Faculty of Agriculture, Nabong Campus. The mean and SD of the initial body weight (BW) of the goats was 14.6 (1.4) and 13.4 (2.2) kg, and the age around 3.5 and 6 months in the first and second experiment, respectively. Before starting the experiments, the goats were treated against parasites with injections of Ivermectin solution (1 ml per 4 kg BW) and were vaccinated against Foot and Mouth disease. Feed and water offered to each goat were weighed every morning and the animals were given the feed ad libitum at the level of 130% of the average daily feed intake the previous week. The animals were fed 3 times per day at 08:00 h, 12:00 h and 16:00 h. The minerals offered to each goat were given ad libitum by hanging a mineral block in each cage. The mineral lick block contained 140 g Na, 140 g Ca, 51 g P, 10.5 g S, 22 g K, 10 g Mg, 2.5 g Fe, 900 mg Zn, 350 mg Mn, 400 mg Cu, 90 mg Co, 380 mg I and 12 mg Se, per kg block. The goats were housed in individual metabolism crates made from local materials measuring 0.8 x 0.8 x 0.8 m in width, length and height, respectively. The houses, cages and troughs were cleaned every day.

Experimental feeds

The experimental feeds used in the first digestibility experiment were foliages from Erythrina (Erythrina variegata), Fig (Ficus racemosa), Jackfruit (Artocarpus heterophyllus), Jujube (Ziziphus jujuba Mill), Kapok (Ceiba pentandra) and Mango (Mangifera indica). In the second digestibility experiment, the feeds used were Water spinach (Ipomoea aquatica), Fig, Jujube and Mango. Each foliage was used in the fresh form, including leaves, petioles and 30 cm of the stem. The foliages were offered hanging, tied to a bamboo stick over the cage and above the feed trough to collect leaves that may have fallen down. The foliages were harvested by cutting trees and shrubs around the Faculty of Agriculture in the morning for feeding at noon and in the afternoon for feeding the next day in the morning. The water spinach was bought from farmers around the Faculty of Agriculture in the morning and weighed for feeding during the whole day.

Experimental design

The first digestibility experiment was a repeated randomized complete block design (RCBD) with 6 treatments (the different foliages fed as the sole feed). The experiment was run for 3 periods (3 repetitions) and each period had 2 blocks. The goats were randomly allocated to the metabolism cages and the foliages. In every period, each foliage was given to 1 animal in each block. The periods consisted of 14 days of adaptation to the diets and 7 days of data collection. Between each period there were 7 days for rehabilitation with good diets such as grass, cassava chips and some foliage supplementation.

The second digestibility experiment was a 4*4 Latin Square design. The treatments were four diets: 1: Water spinach ad libitum (WS), 2: Fig ad libitum + 0.5% of BW as DM Water spinach (FWS), 3: Jujube ad libitum + 0.5% of BW as DM Water spinach (JWS) and 4: Mango + ad libitum + 0.5% of BW as DM Water spinach (MWS). Half of the daily offer of Water spinach was fed at 08:00 h in the morning and half at 16:00 h in the afternoon. Each period of the experiment consisted of 10 days of adaptation to the diets and 5 days of data collection and between each period there was a 3 day period for rehabilitation, with good diets such as grass, cassava chip and some foliage provided.

Measurements and analyses

Feeds offered and refused were recorded individually daily during the whole experimental period. Each foliage, six samples in the first experiment and eight samples in the second experiment, was separated and weighed to estimate the average proportion of leaves plus petiole and stem. During the collection period the refusals were separated into leaves plus petiole and stem in order to measure the selection of the different parts. Water offered and refused was also measured daily. Samples of feed offered were taken twice in each period, resulting in 6 and 8 samples of leaves plus petiole and stem in total in the first and second experiment, respectively. The whole foliage was sampled (divided into leaves plus petiole and stem). Samples of refusals (also divided into leaves plus petiole and stem) were taken individually daily during the data collection periods. The faeces and urine excreted were recorded twice daily at 7:00 h and 17:00 h. At each data collecting time, 10% of the faeces was sampled and frozen at –20^oC. Urine was collected in a jar containing 50 ml of 10% sulphuric acid (urine pH<3) to preserve the nitrogen (Chen and Gomes, 1992) and 10% urine was also sampled and stored at 4^oC for further analysis.The fresh form of the foliages was analysed for DM, ash, and CP according to AOAC (1990). NDF was determined using the procedure of Goering and Van Soest (1970) and Condensed tannins were analysed according to Makkar et al. (1995).

Statistical analysis

The data from the intake and digestibility trials were analyzed statistically by using the GLM procedure of Minitab Software, version 13.31 (Minitab.000). Treatment means, which showed significant differences at the probability level of P<0.05, were compared using Tukey’s pairwise comparison procedures.

In the first experiment, the statistical model used was: Y_ijk = m  + P_i  + B_j(P_i) + F_k +  e_ijk where Y_ijk is the dependent variable, P_i is the effect of period, B_j(P_i) is the effect of block in the period, F_k is the effect of treatment (different foliages) and e_ijk is the random error effect.

In the second experiment, the statistical model used in the analysis was: Y_ijk  = m  + F_i  + A_j + P_k + e_ijk where Y_ijk is the dependent variable, F_i is the effect of treatment, A_j is the effect of animals, P_j is the effect of period and e_ijk is the random error effect.

Experiment 3: Intake and selective behaviour trial

The animals used in the experiment were 8 local male growing goats. The goats were bought in the area around the Faculty of Agriculture, Nabong campus, Vientiane, Lao PDR. The mean and SD of the initial body weight (BW) of the goats was 15.7 (1.1) kg and the age around 7 months. Before starting the experiment, the goats were treated against parasites with injections of Ivermectin solution (1 ml per 4 kg BW) and were vaccinated against Foot and Mouth disease.

Foliage from Erythrina (Erythrina variegata), Fig (Ficus racemosa), Jackfruit (Artocarpus heterophyllus), Jujube (Ziziphus jujuba Mill), Kapok (Ceiba pentandra) and Mango (Mangifera indica) was hung in separate bunches in a large pen. All foliages were offered in the same amount, 1.5% of the BW as dry matter (DM) and together offered in a total amount of 9 % of the BW. The goats were fed 3 times per day at 08:00 h, 11:00 h and 14:00 h. One goat was let in to the pen every morning and the feeding behaviour was recorded as the time spent consuming each foliage during the day from 08:00 h to 17:00 h. The foliages offered were separated and weighed to estimate the average proportion of leaves plus petioles and stems four times during the experiment and the refusals were also separated into leaves plus petioles and stem every day after feeding. The bunches of foliage were weighed before and after feeding to estimate feed intake from leaves plus petioles and stem of the different species. Fresh bunches of feed and a new goat was provided every day and the procedure was repeated for 8 days.

The data from the preference test is presented in the form of frequencies and means using the Excel program.

Results

Experiment 1

The chemical composition of leaves plus petioles and stem of the foliages is presented in Table 1. The Erythrina foliage had a DM content of 197 g and 198 g/kg and a concentration of CP of 193 g and 89 g/kg DM of leaves plus petioles and stem, respectively. The Mango foliage had a CP content of 69 g and 47 g/kg DM and a DM content of 459 g and 352 g/kg of leaves plus petioles and stem, respectively. The other foliages were intermediate between Erythrina and Mango. The content of condensed tannins of leaves plus petioles ranged from 51 g/kg DM in the Erythrina foliage to 130 g/kg DM in the Jackfruit foliage. In Fig and Mango the content of condensed tannins was higher in the stem than in the leaves and petioles while it was lower in Erythrina, Jackfruit, Jujube and Kapok.

Feed offered and feed intake for the six foliages are shown in Table 2. Total DM offered of Jackfruit foliage (965 g DM) was significantly higher than for Erythrina, Fig, Jujube and Mango foliage, but similar to DM offer of Kapok foliage. The total DM intake of Jujube and Mango foliage was lowest, 380 g and 393 g, respectively, significantly different from Jackfruit (with the highest intake of 650 g), Erythrina, and Kapok foliage, but similar to the intake of Fig foliage. Feed intake expressed in percent of BW varied from 2.5% to 4.4%, the highest for Jackfruit and lowest for Jujube.

Water intake varied from 94 g 201 g/day, but was not significantly different among foliages. Feeding Erythrina foliage resulted in significantly higher CP intake, 109 g/day, compared to the other foliages (Table 3). The lowest CP intake was obtained with Mango foliage, 25 g/day.