Growth rate and feed conversion were improved, and emissions of methane reduced, when goats fed a basal diet of pigeon wood foliage (Trema orientalis) were supplemented with sun-dried cassava foliage (Manihot esculenta, Crantz) or water spinach (Ipomoea aquatica)

Phonethep Porsavathdy, Ho Quang Do¹ and T R Preston²

Faculty of Agriculture and Environment, Savannakhet University, Lao PDR
pphonetheb@gmail.com
¹ Cantho University, Vietnam
² Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia

Abstract

The treatments applied to 12 local goats housed in individual pens were three feeding systems: pigeon wood foliage alone or supplemented with sun-dried cassava foliage or water spinach (20% of basal diet DM).

Supplementation resulted in higher feed intake and growth rates, and better feed conversion, with best results for cassava foliage. The proportion of methane in eructed gas was reduced when pigeon wood foliage was supplemented with sun-dried cassava foliage or fresh water spinach, with lower values for cassava foliage than for water spinach.

Key words: feed intake, greenhouse gas, HCN, tannin

Introduction

Goats are by nature browsers rather than grazers. Their preference for browsing was demonstrated in the research by Theng Kouch et al (2003) when rates of eating, total DM intake and DM digestibility were maximized when tree foliages (of cassava, Jackfruit and Mulberry) were suspended above at the front of the pen (Photo 1), rather than being offered as separated leaves in the feed trough. For this reason, our recent experiments with goats have been directed to identifying and testing foliages from trees and shrubs as supplements, or as the sole diet (Theng Kouch et 2006; Daovy et al 2008; Dunget al 2010; Kongmanila et al 2011; Silivong and Preston 2015a,b).

In the upland area of Luang Prabang province in northern Lao PDR, it is common practice for farmers to harvest foliage from the “pigeon wood” ( Trema oriertals) tree and to feed it to their cattle and buffaloes. The foliage of this tree was evaluated as the sole feed for goats in India (Narayan Jyotindra et al 2013); DM intake was high but apparent digestibility coefficients of DM (59.2%) and CP (63.7%) were relatively low.

The strategy used by Kongmanila et al (2011) to improve the digestibility of foliage from Mango and Ficus trees (which supported low DM intakes when fed alone) was to supplement them with a highly digestible foliage in the form of water spinach (Ipomoea aquatica). The reasoning for this approach was that water spinach would supply a readily fermentable source of protein that would provide the peptides, amino acids and ammonia rquired to enhance the microbial fermentation of the fiber in the less digestible leaves of the Mango and Ficus trees. A related approach was taken by Dung et al (2010) when they gave cssava foliage as a supplement to the leguminous shrub Flemengia macrophylla. In this case the cassava foliage was hypothesized to provide both fermentable protein and bypass protein to complement the nutrients derived from the less digestible Flemengia macrophylla.

The hypothesis tested in the experiment reported here was that cassava foliage would be a more appropriate supplement, than water spinach, for goats fed pigeon wood tree foliage.

Materials and methods

Location and duration

The experiment was conducted in the farm of the Faculty of Agriculture and Environment (Nongpue Campus), Savannakhet University, Savannakhet province, Lao PDR, from February to July 2016.

Experimental design

The experiment was conducted as a Completely Randomized Design (CRD) with 3 treatments and 4 replications. The treatments were Pigeon wood foliage fed ad libitum as the sole diet (PW) or supplemented (at 20% of basal diet DM intake) with sun-dried cassava foliage (PWCF) or with fresh water spinach (PCWS).

Animals and housing

Twelve local goats (Photo 1) with initial mean body weight 9.5 kg and 4-5 months of age were housed in separate pens, made from wood and bamboo with floor area 60*80 cm (Photo 2). The goats were vaccinated against epidemic diseases and treated against internal and external parasites with Ivermectin (3ml/100 kg live weight). They were adapted to the pen and feeds for 14 days before starting the collection of data.

Photo 1. Local goats used in the experiment	Photo 2. Housing for the goats made from local materials

Feeding and management

Pigeon wood foliage (Photo 3) was harvested every day from trees in the forest around the farm. Cassava was grown in the farm area and the foliage harvested at 8-10 week intervals. It was sun-dried prior to feeding (Photo 4) . Water spinach was also grown in the farm area and harvested at approximately 4 weeks of growth/re-growth (Photo 5). It was fed fresh. The feeds were offered twice per day at 07:00 and 6:30h.

Photo 3. Foliage from the pigeon wood tree	Photo 4. Sun-dried cassava foliage	Photo 5. Fresh water spinach

Data collection and measurements

Feeds offered and refused were weighed. The live weights of the goats were taken at the beginning and every 2 weeks over the growth period of 84 days. Rates of live weight gain were determined from the linear regression of live weight (Y) on days in the experiment (X). At the end of the experiment the ratio of methane and carbon dioxide in eructed gas from each animal was recorded using the Gasmet equipment (GASMET 4030: Gasmet Technologies Oy, Pulttitie 8A, FI-00880 Helsinki, Finland), following the procedure outlined by Madsen et al (2010). The goats were held for 5 minutes in wooden crates covered with polyethylene film (Photo 6) before taking the measurements, so that the gases emitted from the animal could equilibrate with the air in the box. Samples of air in the animal house were also analysed for the methane: carbon dioxide ratio.

Photo 6. Wooden cage covered by plastic for recording methane emissions

Chemical analysis

Samples of feeds offered and refused were collected every 14 days to determine dry matter (DM) and crude protein (CP) according to AOAC (1990) methods.

Statistical analysis

The data were analyzed by the general linear model option of the ANOVA program in the Minitab (2000) software (version 16.0); sources of variation were treatments and error.

Results and Discussion

Chemical composition of the feeds

The values of CP and DM in the cassava foliage and water spinach were within the ranges reported in Feedipedia. DM and CP (% in DM) in the leaves of the pigeon tree were slightly lower than was reported by Narayan et al (2013) (34 and 19%, for DM and CP respectively).

Feed intake

Intake of pigeon wood foliage was similar on all treatments thus total intake was increased when water spinach or sun-dried cassava foliage were also given (Table 2; Figure 1). Similar responses were reported by Kounnavongsa et al (2010) when local goats fed Gamba grass ( Andropogon gayanus cv. Kent)) or sugar cane stalk were complemented with sun-dried cassava foliage.

Figure 1. Effect of supplements of water spinach (PWWS) or sun-dried cassava foliage (PWSC) on DM intake of goats fed a basal diet of pigeon wood foliage (PW).	Figure 2. Effect of supplements of water spinach (PWWS) or sun-dried cassava foliage (PWSC) on live weight gain of goats fed a basal diet of pigeon wood foliage (PW).

Growth rate and feed conversion

Growth rate and feed conversion showed similar responses as DM intake with best performance being obtained when cassava foliage was the supplement (Table 3; Figures 2 and 3). Faster growth and better feed conversion rates of goats given cassava foliage as a supplement to a range of forage-based diets were reported by many researchers (Ho Quang Do et al 2002; Seng Sokerya and Preston 2003; Ho Bunyeth and Preston 2006; Kounnavongsa et al 2010; Phengvichith and Preston 2011).

Figure 3. DM feed conversion in goats fed pigeon wood foliage supplemented with water spinach or sun-dried cassava foliage	Figure 4. The ratio methane:carbon dioxide in eructed gas and air in goats fed pigeon wood foliage was reduced by 26% by supplementation with water spinach and by 41% with sun-dried cassava foliage

Methane production

The ratio of methane to carbon dioxide in the mixed air and eructed gas was reduced by 26% in the goats supplemented with water spinach and by 41%% when sun-dried cassava foliage was the supplement (Figure 4). The beneficial effects of a supplement of cassava foliage in reducing methane production in goats have been reported previously (Phonethep et al 2016).

Conclusions

Goats fed pigeon wood foliage had better growth and feed conversion when supplemented with sun-dried cassava foliage or fresh water spinach, with the best results for cassava foliage

The proportion of methane in eructed gas was reduced when pigeon wood foliage was supplemented with sun-dried cassava foliage or fresh water spinach, with lower values for cassava foliage than for water spinach.

Acknowledgements

This research was done by the senior author as part of the requirements for the MSc degree in Animal Production "Improving Livelihood and Food Security of the people in Lower Mekong Basin through Climate Change Mitigation" in Cantho University, Vietnam. The authors acknowledge support for this research from the MEKARN II project financed by Sida.

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Received 20 January 2017; Accepted 20 February 2017; Published 1 April 2017

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