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Citation of this paper

Reducing the carbon dioxide footprint of goat production with green tea (Camellia sinensis), Jackfruit (Artocarpus heterophyllus) foliage and coconut oil

Nguyen Thi Ngoc Trang1 and Nguyen Thi Thu Hong2,3

1 Faculty of Natural Resources - Environment, Kien Giang University, Vietnam
ntntrang@vnkgu.edu.vn
2 An Giang University, An Giang, Vietnam
3 Vietnam National University, Ho Chi Minh City, Vietnam

Abstract

Four growing male goats (14.9±1.0kg) were used in a 4*4 Latin square arrangement to determine feed intake, N retention and rumen methane production on a basal diet of water spinach (Ipomoea aquatica) supplemented with two sources of dietary tannin:Camellia sinensis leaves or Jackfruit (Artocarpus heterophyllus) foliage with or without coconut oil. The treatments had no effect on DM or protein digestibility but increased N retention and reduced methane production. There appeared to be a negative relationship between N retention and the concentration of methane in the rumen gas.

Key words: methane, N retention, tannin, water spinach


Introduction

Climate change seriously affects ecological balance, human health, and sustainable living (Najeh Dali 2008). Methane emissions from ruminant livestock have contributed significantly to this process (Watson 2008).

Tiemann et al (2008) reported that the inclusion of tannin-rich shrub legumes species Callinadra calothyrsus and Fleminga macrophylla in the diet of lambs reduced CH4 emissions by up to 24%. Tannins are also present in leaves of green tea (Camellia sinensis) and are readily available at tea processing factories in Vietnam. Chu Manh Thang et al (2016) fed different levels of green tea leaves to growing cattle and found that they decreased rumen methane emissions.

In our research, we studied the effects of green tea leaves compared with leaves of another tannin plant Artocarpus heterophyllus as supplements for growing goats fed a basal diet of water spinach, h a plant known to produce high levels of methane when fed to goats (Silivong et al 2013).


Material and methods

Location

The experiment was carried out in the farm of An Giang University from January to June 2019.

Experimental animals, treatments and design

Four growing male goats (14.9±1.0kg) were hired from smallholder goat keepers in the area. The trial was a 2*2 factorial arrangement of four treatments with 4 replications. The experiment was designed with two factors: (i) Camellia sinensis or Jackfruit (Artocarpus heterophyllus) as sources of condensed tannin (at approximately 50g tannin/kg diet DM); and (ii) supplementation with or without coconut oil at 10g/kg DM intake.

Individual treatments were:

WM: Water spinach plus Camellia

WMC: Water spinach plus Camellia with coconut oil

WL: Water spinach plus Jackfruit

WLC: Water spinach plus Jackfruit with coconut oil

Feeds and management

The goats were vaccinated against foot and mouth disease and de-wormed before the start of the experiment. They were individually fed in metabolism cages with free access to water and mineral blocks. New feed was offered daily at 08:00 and 16:00. All treatments included 50g rice bran/day as the carrier for the coconut oil.

Branches of Jackfruit growing in nearby fields were collected every day. Water spinach was grown on plots on the University farm and was harvested after 21 days of regrowth. It was put in the feed trough at an offer level of about 120% of recorded intake. The branches of Jackfruit were tied in bunches suspended above the feed troughs in amounts that would provide approximately 50 g condensed tannin per 1 kg DM intake.

Green tea meal (by-products) was mixed with rice bran.

Photo 1. The goat is feeding on rice bran Photo 2. Suspending the branches of Jackfruit (Artocarpus heterophyllus) to simulate browsing

Each experimental period lasted 20 days. For the first 10 days in each period, the goats were adapted to the new diets. From 11 to 15 days feces and urine were collected, and feeds offered and refused were recorded. The urine was acidified with 10% H2SO4 to prevent ammonia-N loss. Samples of feces and urine. and of feeds offered and refused were pooled over the 5-day collection period and refrigerated (-18°C) prior to analysis. On the 15th day of each period of the experiment, the carbon dioxide and methane in eructed gases were measured. The gases were collected in the morning by placing the goats in a glass chamber and after a period of 5 minutes for equilibration with the air in the chamber, the concentrations of methane and carbon dioxide were determined using a Greenhouse Gas Analyzer, model number 908 - 0011. There were rest periods of 5 days between experimental periods when the goats were fed only grass.

The samples of feed offered and refused and of feces were analyzed by AOAC (1990) methods for dry matter (DM) by drying at 1050C for 24h; organic matter (OM) by ashing at 5500C for 4h; and crude protein (CP) by Kjeldahl technique. Neutral detergent fiber (NDF) and acid detergent fiber (ADF) were analyzed using the method of Van Soest and Robertson (1985). The condensed tannin content of feeds was determined by the Lowenthal method (AOAC 1936). Protein solubility was determined by the method described by Whitelaw and Preston (1963).

Statistical analysis

The data were analyzed using the general linear model in the ANOVA program of the Minitab software release 16.20. Sources of variation in the model were: source of supplementary foliage (Camellia and Jackfruit), supplementation with coconut oil, interaction foliage*coconut oil, animals, periods, and error.


Results and discussion

Condensed tannin was 20% higher in leaves of Camellia than in leaves of Jackfruit (Table 1). There was no tannin in water spinach. NDF was higher in Jackfruit than in Camellia leaves The solubility of the protein was high in the water spinach and low in the jackfruit leaves.

Table 1. Chemical composition of the feeds used in the experiment

Items

Camellia

Jackfruit

Water spinach

Rice bran

Dry matter, g/kg

967

375

151

878

DM basis, g/kg

CP

195

124

195

101

OM

907

872

883

891

ADF

236

359

223

86

NDF

336

471

415

223

Comdensed tannin

198

131

-

-

Protein solubility, %

nd

12.2

77.8

nd

DM intake and DM digestibility were not affected by the source of tannin nor by supplementation with coconut oil (Table 2). N retention tended to be higher (p=0.09) for supplementation with green tea leaves compared with Jackfruit leaves but was not affected by the addition of coconut oil (Table 2).

The methane: carbon dioxide ratio in expired gas was lower when green tea was the supplement compared with Jackfruit and can be assumed to be lower than in the basal diet of water spinach for which methane emissions are known to be very high (Preston et al 2019; Sengsouly et al 2016). The high solubility of the protein in the water spinach (78%) has also been shown to be directly related to the comment of methane in expired gas (Do H Q et al 2013).

Table 2. Mean values for DM intake and digestibility, N retention, DM conversion (DM intake/N retention), and methane:carbon dioxide ratio in the expired breath of goats fed a basal diet of water spinach and: (i) Camellia sinensis (CS) or Artocarpus heterophyllus (AH); or (ii) were supplemented or not with coconut oil

Leaves

p

Coconut oil

p

SEM

Camellia

Jackfruit

No CLO

CLO

DM intake, g/d

Leaves

111

176

0.001

142

145

0.825

11

Water spinach

302

252

0.136

277

278

0.979

22.0

Rice bran

44

44

-

44

44

-

-

Total

457

473

0.688

463

467

0.910

26.4

Crude prote

88.6

80.6

0.305

83.2

86.0

0.705

5.2

DM dig, %

76.9

73.8

0.249

74.4

76.3

0.450

1.8

N ret. g/d,

5.83

4.22

0.087

4.69

5.36

0.451

0.61

CH4 : CO2

0.01327

0.01531

0.050

0.01667

0.01191

<0.0001

0.000661


Discussion

Production of methane in the rumen involves a reduction in the nutritive value of the diet (Johnston and Johnston 1995) as methanogens compete for hydrogen in the rumen fermentation with reduced production of propionic acid an important precursor of glucose in the ruminant animal.

A trend was observed in the present experiment for N retention to be decreased as the as methane: carbon dioxide ratio in rumen gas was increased (Figure 1).

Figure 1. Relation ship between N retention and methane:carbon
dioxide ratio in the expired breath of the goats

Tavendale et al (2005) suggested two modes of action of tannins on methanogens: directly affecting activity or population of methanogens, resulting in lower methane emission, and indirectly by reduced hydrogen production by lowering feed degradation.


Conclusions


References

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