Studies on the nutritive value of foliage from legumes and shrubs for goats

 

Ngo Tien Dung, Nguyen Thi Mui, Tran Hoang Chat and Dinh Van Binh
 

Goat and Rabbit Research Centre, Sontay, Hatay, Vietnam
ngotiendzung@yahoo.com

Abstract

Leaves from six different trees commonly available in the tropics were selected, dried and subjected to analysis by the in sacco nylon bag degradability test, and by the in vivo digestibility method.

The dry matter (DM) and crude protein (CP) degradability and digestibility of Leucaena were higher than for Calliandra, Flemingia and Jackfruit. The potential degradability (A+B) and effective degradability (ED) of the DM and CP of the Leucaena K636 and Leucaena .KX2 were higher than for the other foliages. Nitrogen retention values by growing goats were 24.4, 20.5, 21.1, 19.8, 18.9 and 10.1 g/day for Leucaena K636, Leucaena KX2, Calliandra, Leucaena pallida K748, Jackfruit and Flemingia, fed as the sole diet, respectively. The highest nitrogen retention was with L.KX2 and the lowest with Flemingia foliage. There were close relationships between in sacco estimates of rumen degradability of DM and crude protein and the corresponding in vivo determinations (R²= 0.62 and 0.96, respectively).

Keywords: Foliage, Leucaena leucocephalla K636, Leucaena pallida K748, Leucaena KX2 hybrid, Calliandra calothyrsus, Flemingia (Flemingia macrophylla), Jackfruit (Artocapus heterophyllus), in sacco rumen degradability, in vivo digestibility
 

 

Introduction

 

Foliages from legumes and shrubs have been used traditionally by farmers as animal feed but relatively little is known about their potential to replace conventional protein-rich concentrates such as soya bean meal and fish meal (Keir et al 1997a,b). The plants also fulfill a valuable environmental role. In many countries especially in developing countries deforestation is a widespread problem. Encouraging farmers to plant trees and shrubs, which can be used as animal feed, helps to solve these problems. Two aspects are possible for developing feeding systems using leaves from trees: using the foliage from legumes and shrubs already planted in the households;  and introducing new legumes and shrubs which have high biomass production and good potential as animal feed.

 

Leucaena leucocephala  K636, Leucaeana pallida K748, Leucaena KX2 hybrid and Calliandra calothyrsus have been selected from 28 varieties that were imported from Australia in 1994, and which have adapted to conditions in North Vietnam, especially in the acid soils, and have given higher biomass yield than local varieties. Leaves and seeds of Leucaena contain mimosine, a toxic amino acid,  and tannins, which can produce ill effects in ruminants, which do not have the necessary microorganisms in their rumen microflora to detoxify them.

 

Flemingia macrophylla is a shrub introduced to many areas in Asia. Flemingia grows well on acid soils (Dinh Van Binh et al 1998) and has been used for soil conservation with good results (Susilawati et al 1997). Flemingia produces a very high edible biomass yield (40 to 64 tonnes/ha/year) with a protein content of approximately 17% of dry matter (Dinh Van Binh et al 1998), which makes it interesting as a potential protein source for ruminants.

 

Jackfruit (Artocapus heterophyllus) is a common, non-leguminous tree growing up to 15 m high which is planted for fruit in home-gardens in many parts of Vietnam. The jackfruit leaves have been collected by pruning the trees and are widely used as a feed source despite their apparently low protein digestibility thought to be due to the high tannin content.

 

The aim of this study was to examine and evaluate the nutritive value of foliage from six species of trees using the in sacco rumen degradability and in vivo digestibility methods.

 

Material and methods

Location

This study was carried out at the Goat and Rabbit Research Center in Sontay, Hatay, North Vietnam.

In sacco rumen degradability

 

Sampling

One portion of each of the samples of leaves (from Leucaena leucocephala K636, Leucaena pallida K748, Leucaena KX2 hybrid, Calliandra, Flemingia and Jackfruit) was oven-dried and milled in a hammer mill through a 1.0 mm sieve for chemical analysis. The rest was dried and ground through a 2.5 mm screen for the DM degradation in sacco method (Ørskov and Hovell 1970).

DM degradation was determined by incubating about 3.5 g of sample in nylon bags in three rumen-fistulated goats. The goats were fed a basal diet of ad libitum guinea grass (DM 17.5 %; crude protein in DM 10.6 %) plus 200 g dried cassava root (DM: 87%; crude protein 3% in DM) and 210g concentrate (DM: 87%, CP: 18% in DM). All the bags were suspended in the rumen prior to the morning feeding. They were withdrawn after 6, 12, 24, 48, 72 and 96 h of incubation, washed  by hand in cold running water until the water ran clear and then dried to a constant weight at 60^oC (about 48 h). Washing losses at zero time were estimated by soaking two bags per sample in warm water (39^oC) for 1 h followed by washing and drying as before. The course of degradation of the feed was described by fitting the data (loss of DM and crude protein during incubation)  to the exponential equation of McDonald (1981):

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

using the "Fcurve" software, running on Microsoft Excel.

In vivo digestibility

Six male goats of F1 (Bachthao x Jumnapary) with live weights from  22.3 to 28 kg were  fed the fresh leaves from the six tree foliage according to a randomized complete block design with 4 replications. They were confined in metabolism cages allowing the separate collection of faeces and urine. The foliages (stems with attached petioles and leaves) were fed three times daily (7.30, 13.30 and 17.00h) by hanging them in the cage at a daily offer level of 4 % of body weight (DM basis). Water was available at all times. Before starting the experiment, the animals were treated against internal and external parasites (Ivermectin at 1ml/kg live weight injected subcutaneously and Albendazole at 0.1 mg/kg body weight given orally).   The experiment consisted of two periods: 9 days of adaptation followed by 7 days of collection of faeces and urine and recording of feed offered and refused. The faeces were weighed every day at 07.00 h then mixed thoroughly and 10% taken for analysis. Urine was collected in a glass bottle, to which 50 ml of H₂SO₄ 0.1N was added to avoid nitrogen loss. Samples of 10% of the daily urine output were frozen and pooled for each animal.  The goats were allowed 10 days of free feeding/grazing between the collection periods..

The data from the experiment were analysed as a Randomized Complete Block Design  using the General Linear Model option of the ANOVA MINITAB software (Minitab 2000). The treatment means which showed significant differences at the probability level of P<0.05 were compared with each other using the Tukey’s pair-wise comparisons procedure..  The statistical model used in the analysis was:

Yij = µ + Tj +Bi + (TB)ij  +  eij         

where Yij = dependent variable, µ = overall mean, Tj  = treatment; Bi: block; (TB)ij  = interaction between treatment and block, eij  = random error

Chemical analysis

Dry matter was determined by micro-wave radiation to constant weight (Undersander et al 1993). Total nitrogen was determined by the Kjeldahl technique and crude protein calculated as N x 6.25. Ash and ADF were determined according to AOAC (1990). NDF was determined by the method of Van Soest et al (1991).
 

Results and discussion

Chemical composition

In this study the crude protein contents of the Leucaena varieties and Calliandra were higher, and NDF and ADF lower, than the Flemingia and Jackfruit (Table 1).

 

In sacco rumen degradability

Rates of dry matter and crude protein  loss in the rumen from the Leucaena varieties were always higher than from Calliandra, Flemingia and Jackfruit (Table 2).   Most of the DM and CP was lost during the first 24 hours of incubation.

 

Water soluble losses at zero time, and potential and effective degradabilities,  were higher for the Leucaena varieties than for Flemingia, Jackfruit and Calliandra (Table 3).

 

In vivo digestibility trial

Despite their lower digestibility, the foliage of Jackfruit was consumed in greater amounts than the other foliages (Table 4). The feed refusals were also least for this foliage and highest for the Flemingia. The Leucaena variety K748 was less digestible than the other Leucaena varieties. The intake of Flemingia was the lowest of all the foliages.

N retention was highest on the Leucaena varieties, and lowest for Flemingia with Calliandra and Jackfruit having intermediate values (Table 5). N retained as percentage of N consumed showed few differences for all the foliages, with the exception of Flemingia which had very low values.

The low values for intake, digestibility  and N retention of goats fed only Flemingia foliage support the findings of Nguyen Thi Mui et al  (2001) that depressed performance was observed on growing and lactating goats when Flemingia foliage supplied more than 15% of the dietary DM. In contrast, the high intake and N retention of goats fed the Jackfruit foliage helps to explain the high intakes (Kouch  et al 2003) and good growth rates (Nguyen Thi Mui et al 2001) of goats fed on foliage from this tree. 

Figure 1: Relationship between in sacco DM degradability at 24h and in vivo DM digestibility in 6 tree foliages
 

 

 

Figure 2: Relationship between in sacco crude protein degradability at 24h  and in vivo crude protein digestibility in 6 tree foliages
 

There was an extremely close relationship between in sacco degradability of crude protein and the in vivo digestibility of crude protein (R²=0.96; Figure 2).  The corresponding relationship for dry matter was less pronounced (R²=0.62; Figure 1).
 

Conclusions

• Foliage from the three Leucaena varieties supported high voluntary intakes and retention of nitrogen, and were  highly digestible.
• The foliage of Jackfruit supported the highest intake with least refusals. In contrast, intakes were lowest on Flemingia and refusals were the highest. Digestibility and N retention were the lowest for this foliage.
• There were close relationships between in sacco estimates of rumen degradability of DM and crude protein and the corresponding in vivo determinations (R²= 0.62 and 0.96, respectively).
   

Acknowledgements

The authors are grateful to the Swedish International Development Authority (SIDA/SAREC) for financing this study. We are also grateful to the Goat and Rabbit Research Centre Sontay, Hatay for use of their facilities.

References