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Workshop-seminar "Making better  use of local feed resources" SAREC-UAF,  January , 2000.

 

Performance of growing goats fed Gliricidia maculata
as a protein supplement

 

Nguyen Van Hao and Inger Ledin^*

 

University of Agriculture and Forestry, Thu Duc, HoChiMinh City
^* Swedish University of Agricultural Sciences, Box 7024, 750 07, Uppsala, Sweden.

 

 

Abstract

The main objective of this experiment was to evaluate the effect of different levels of Gliricidia leaves as a protein supplements to diets based on locally available crop by-products on the growth of goats. Sixteen  female crossbred (local female x Anglo-Nubian male) goats raised from 20-30 kg  were fed a basal diet of cassava chips, cotton seed cake, rice bran and rice straw supplemented with 0, 30, 40 or 50% of diet dry matter of Gliricidia maculata. All the diets containing Gliricidia resulted in a higher intake than the diet without Gliricidia but the diet with 30% Gliricidia gave the best intake and the highest growth rate (105g/day). Total intake of dry matter was 2.8% of the body weight.

 

Five male goats of the same breed and size were used to study the effect of supplementing rice straw with different levels of Gliricidia leaves on intake and apparent digestibility of the diets. Increasing the amount of Gliricidia leaves decreased the rice straw intake but increased intake of total dry matter, organic matter and crude protein. Supplementing with Gliricidia leaves improved the dry matter digestibility, the organic matter digestibility and the crude protein digestibility, in the mixed Gliricidia and rice straw diet compared to rice straw, but the values were somewhat lower than could be expected by calculations from the rice straw and Gliricidia diets. The dry matter digestibility of Gliricidia was 64.1%.

 

Key words: Goats, cassava, rice straw, Gliricidia maculata, growth, intake, digestibility.

Introduction

Most of the small-holder farms in Southeast Asia are mainly crop-oriented subsistence farms. Livestock and poultry raising are integrated as the supportive sub-system of the farms. The main purposes of keeping ruminant livestock on the farm are to provide power, transportation, fertilizer and reproducible farm assets. The ruminants graze on marginal land and on the roadsides to obtain green forage during the rainy season. During the dry period, when green forages are scarce, crop by-products and farm wastes represent the most important sources of feeds for ruminant livestock. The fibrous crop by-products are the major potential feed resources , and the by-products from rice are most abundant, followed by those from cassava, maize, cotton and bananas. The fibrous crop by-products are characterized by the extensive lignification of the cellulose and the hemicellulose, and by the low levels of protein, soluble carbohydrates and minerals. As a consequence, the intake and digestibility of these feeds are not sufficient to sustain high levels of production. Supplementation with protein but also with soluble carbohydrates is very important for obtaining a good production. The leaves from leguminous trees and shrubs are cheap and easily available sources of protein. The use of good quality forage legumes as supplements for ruminants during the period of critical feed scarcity in the dry season, appears to be a promising means of improving the productivity of ruminant livestock at farm level. One of the possible species is Gliricidia maculata.

Gliricidia maculata used to supplement poor quality roughage and during the dry seasons  may become a major source of feed for goats and cattle in dryland farming areas (Wiersum and Nitis 1992 ; Stewart and Simons 1994). Gliricidia is characterized by fast growth, ability to fix nitrogen, high nitrogen content, tolerance to pruning and to coppicing, good fodder value, high foliage productivity and a vigorous tap root (Atta-Krah and Sumberg 1987). Moreover, Gliricidia can grow in various parts of the tropical zone from sea level to about 1,100m elevation with a mean annual rainfall of 650-3,500 mm and a mean annual temperature range of 22-30^º C (Hughes 1987). The utilization of Gliricidia as a fodder for farm animals has been tested in Central America, Africa and Asia (Devendra 1990).

The objective of the present experiment was to evaluate the effect of feeding different levels of Gliricidia leaves as a protein supplement to diets based on locally available crop by-products on the growth of goats.

 

Material and methods

Location and climate of the study area

The experiment was conducted at the experimental farm of the University of Agriculture and Forestry in Ho Chi Minh City. The climate in the area is tropical monsoon, with a dry season between November and April and a wet season from May to October with an average of 1600 mm rainfall. The mean temperature is 28 ºC degrees during year. The experiment was conducted between April and June in 1998, a year when the wet season started very late in June.

 

Experimental animals and feeds

The animals in the experiments were selected from a flock of goats raised in a confinement system. For the growth experiment,16 females aged 6 months (local female x Anglo- Nubian male; mature weight 35 kg) were selected. In the digestibility study 5 male goats, 8 months-old were used. All goats weighed between 19 and 21 kg when the experiments started. The goats  were vaccinated against foot and mouth disease and treated against gastrointestinal parasites using Albendazole tablets before the commencement of the experiment.

Rice straw was harvested at the university farm and baled in February and March, 1998. The rice straw was chopped to 10-15 cm length before feeding to reduce bulkiness in the feeding troughs. Fresh leaves of Gliricidia maculata, from shrubs planted in 1992 at the University farm, were harvested every day at 6 am for the growth experiment. The leaves and small twigs were included in the feed. Cassava chips, rice bran and cottonseed cake were bought at local feed mills.

 

Experimental design

The animals in the growth experiment were assigned to four treatments, consisting of 4 levels of Gliricidia leaves in the diet: 0, 30, 40 and 50% of expected dry matter (DM) intake in a randomized design with four animals per treatment. The diets were based on the results of the chemical analysis of the experimental feeds (Table 1) and expected DM intake and nutritional requirements according to Peacock (1996). The actual amounts and feeds offered are shown in Table 2 for the first growth period (20-25kg).

 

In the digestibility experiment the animals were allocated to five dietary treatments according to a Latin Square arrangement (5*5) (Mead et al1966). The treatments were as follows:

• RS100: 600g DM/day rice straw

• GL100: 600g DM/ day Gliricidia leaves

• GL30: 420g DM/ day rice straw + 180g DM/ day Gliricidia leaves (30%)

• GL40: 360g DM/ day rice straw + 240g DM/ day Gliricidia leaves (40%)

• GL50: 300g DM/ day rice straw + 300g DM/ day Gliricidia leave (50%)

 

The experiment lasted 17 weeks in total, 2 weeks of adaptation and five periods consisting of three weeks per period, one week of adaptation, one week of collection and one week for releasing the animals on an open ground for exercise. During the period of exercise the animals were fed on the experimental feedstuffs supplemented with rice bran and cotton seed cake.

 

Feeding and management

The goats were individually housed and fed in the growth experiment and kept in simple metabolism cages that allowed separation of faeces and urine in the digestibility experiment. The feeding troughs were divided into sections, giving access to each feed stuff separately. Drinking water, salt and mineral lick blocks were available at all times. The animals were fed twice per day at 08.00 and 14.00 hours.

 

Data collection and analyses

The animals in the growth experiment were weighed when the experiment started and then once per week always at 7.00 am. The experiment lasted 90 days. The feed consumption and the feed refusals (rice straw, rice bran, cottonseed cake, cassava chips and Gliricidia leaves) were collected from individual animals and weighed every day in the morning before feeding. Samples of feeds, rice straw, rice bran, cotton seed cake and cassava chips were taken once per week. Since it can be expected that these feedstuffs were relatively constant in their composition (the feedstuffs were bought as one lot at the same time) the samples were pooled to 2 samples per month (2 weeks samples put together as one). Samples of Gliricidia leaves were taken every day and pooled weekly. DM content was however determined daily before feeding. The refusals were collected every day and pooled together to a weekly sample.

 

During the collection period of the digestibility experiment, samples of rice straw were taken once per week, while samples of Gliricidia leaves was taken every day and pooled weekly. DM content was however determined daily. Feed refusals were collected from individual animals and weighed every day. Samples of faeces and urine were collected every morning, weighed and kept in a deep freezer. The animals were weighed before commencement of the adaptation period and before feeding on first and last days of each collection period.

 

The feeds and refusals in the growth experiment and the digestibility study were analyzed for DM, ash, organic matter (OM), nitrogen (N), neutral detergent fiber (NDF) and acid detergent fiber (ADF). Samples for the chemical analysis were taken from previously bulked feed, refusals and faeces and pre-dried at 60ºC before grinding using a 1mm screen and a hammer mill. DM content in the samples was determined by drying to constant weight at 105 ºC. N was determined using the Macro Kjeldahl method (AOAC 1985). Ash content was determined by incinerating the samples at 500ºC. NDF and ADF were determined using procedures described by Goering and Van Soest (1970) .

 

Statistical analysis

The data from the experiment were statistically analysed with a variance analysis using the General Linear Model (GLM) of Minitab Software (Minitab1998). The following model was used for the growth experiment.

Y_i = µ + A_i + e_i

where Y_i = growth or feed consumption, µ = overall mean, A_i = effect of diet,  e_i = random error.

For the digestibility experiment the model was:

Y_ijk = µ + A_i +B_J+ C_k + e_ijk

where Y_ijk = dependent variable, µ = overall mean, A_i = effect of diets, B_j = effect of  animals, C_k = effect of periods, e_ijk = random error.

 

Results

Nutrient levels of the diet ingredients  were in accordance with expectations (Table 1) with the fibre content of Gliricidia and cottonseed cake intermediate between the rice straw and the rice bran.  The ash content was quite high in the Gliricidia and very high in the rice straw.

 

 

The low level (30%) of Gliricidia leaves increased the intake of rice straw and of total dry matter compared with zero Gliricidia (Table 2). There are many reports of low levels of legume foliage or green grass increasing the intake of a fibrous basal diet (Guttierrez and Elliott 19; Kimambo et al 1992)

 

The mean daily gains were highest in the treatment with 30% Gliricidia but significantly so only during the second period (Table 3).

 

 

In the digestibility experiment, supplementation with different levels of Gliricidia leaves to rice straw resulted in a significant increase of the total intake of DM, OM, ADF, NDF and CP (Table 4).

 

Figure 1: Relative intakes of rice straw and gliricidia leaves by goats in the digestibility trial

 

The digestibility coefficients of DM and OM were highest in the diet consisting of 100% Gliricidia. Calculations of DM and crude protein digestibility for the mixed diets based on the intake and digestibilities of straw and Gliricidia showed that the calculated values were higher for dry matter and lower for crude protein than the values actually obtained.

 

 

 

All diets with Gliricidia supplementation resulted in a positive N balance, while the goats fed only rice straw were in negative balance.

 

 

Discussion

The animals were adapted to eating the supplements within the first few days of the preliminary period and it took only 20-30 minutes for the animals to clear the supplements from the feeding troughs. The goats on all dietary treatments readily consumed the feedstuffs, indicating no palatability problems. The goats on the diet containing no Gliricidia, however, were not able to consume all the cotton seed cake and the faeces were very dry and hard. According to Chadhokar and Kantharaju (1980) Gliricidia maculata was found to be palatable by both cattle and sheep even when fed in very large quantities over a long period.

 

In the digestibility experiment the increasing levels of Gliricidia resulted in a an increase in the total intake but a depression in intake of the basal rice straw diet. This was probably due to the substitution effect as reported by Chakodar and Kantharaju (1980), Ash (1990) and Kimambo et al (1992). Preston and Leng  (1987) also reported that when roughages of low nitrogen concentration are given to the ruminant, the supplementation with green forages often results in an increase in voluntary feed intake, due to increased availability of fermentable nitrogen and other nutrients required by rumen bacteria.

 

Supplementation of rice straw with Gliricidia leaves resulted an increase in the digestibility of DM, OM, and crude protein which could be expected. These results are in agreement with those observed by Mosi and Butterworth (1985) and McMeniman et al (1988) who reported an improvement in digestibility when sheep were fed a crop residue diet supplemented with legume straw and increasing levels of the legume Trifolium tembense (Clover). The level of Gliricidia supplementation did not seem to be important for the digestibility of crude protein in spite of the fact that the crude protein intake increased significantly. This could be due to the presence of large quantities of condensed tannin in Gliricidia leaves. This result agrees with the study of Jones (1979) and Reed et al (1990), who reported that supplements of fodder tree leaves should be about 30% of the diet dry matter, because of the secondary compounds which inhibit the digestibility and reduce the acceptability to animal at higher levels of inclusion. Also Devendra (1993) and Stewart (1994) conclude that, when used as supplements, the optimum dietary level of fodder trees and shrubs should be about 30 to 50% of the ration on DM basis.

 

Conclusions

This study showed that:

·        Supplementing a basal diet of rice straw with 30% Gliricidia (DM basis) resulted in an increased intake of DM, OM and crude protein. Higher levels of Gliricidia leaves did not give any increase in intake or growth but supported higher retention of nitrogen.

·        The DM digestibility of the rice straw was 55.5% and of  Gliricidia leaves 64.1%.

·        The results indicated that moderate levels (30-40%) of Gliricidia supplements in a basal diet of rice straw can significantly improve the intake and performance of goats.

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