Growth performance of goats was improved when a basal diet of foliage of Bauhinia acuminata was supplemented with water spinach and biochar

Phonevilay Silivong and T R Preston¹

Souphanouvong University, Lao PDR
silivongpvl@yahoo.co.th
¹ Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV)
Carrera 25 No 6-62 Cali, Colombia

Abstract

The aim of the study was to determine the effect of water spinach and biochar on enteric methane emissions, feed intake, digestibility, nitrogen retention and growth performance in local goats fed Bauhinia acuminata and molasses as basal diet. The experiment was arranged as a 2*2 factorial with 4 replications using sixteen goats in individual pens (initial live weight 12.9 kg and 6-7 months of age).

Daily live weight gain and feed conversion, and DM digestibility and N retention, were improved by feeding water spinach and by supplementation with biochar. The higher value of rumen ammonia in goats fed water spinach reflected the greater solubility of the crude protein in the water spinach. Supplementation with water spinach led to a reduction in the methane/carbon dioxide ratio in the eructed breath of the goats but this criterion was not affected by biochar.

Key words: carbon dioxide, climate change, methane, N-balance, protein solubility, rumen ammonia

Introduction

Livestock are the most important source of protein food and family cash income of farmers in Laos, and also give manure for cropping in the rural areas. Most of the production from livestock such as goats, cattle, pigs and poultry comes from smallholders using traditional management systems.

The main feed resources for ruminants are native grasses, legumes and tree leaves that are available in the natural grassland and forests (Phengsavanh 2003). The conventional feeding system for goats in Lao PDR is based mainly on the use of natural grasses. However, in the dry season, natural pasture decreases in nutritive value and improved grasses cannot grow. Therefore, it is important to find an alternative feeding system because purchased supplements are too expensive for poor farmers. On the other hand, there are many trees and shrubs available. Preston and Leng (2009) and Leng (1997) have emphasized that in tropical countries one of the most appropriate ways to improve feed supplies for ruminants is through utilization of tree and shrub foliages.

Daovy et al (2007) reported that water spinach (Ipomoea aquatica) supplementation of low quality tree foliage (from Fig, Jujube and Mango trees) increased the DM and crude protein intake of goats, and improved the apparent digestibility and N retention. According to Thu Hong et al (2011), the live weight gain of goats fed Mimosa foliage was increased by supplementing with fresh water spinach at 27% of the total DM intake. Goats fed a sole diet of cassava foliage also responded with increased DM digestibility and N retention when fresh water spinach was provided as a supplement (Pathoummalangsy and Preston 2006).

The legume tree Bauhinia acuminate is widely distributed in the Luang Prabang province and it has been observed that the foliage is readily consumed by goats. As is the case with most foliages from legume trees, it contains many secondary plant compounds including tannins. It was therefore hypothesized that the growth performance of goats fed Bauhinia foliage as the basal diet would be improved by supplementing it with water spinach.

The negative feature of livestock is that they contribute some 18% of the greenhouse gases that are causing global warming (Steinfeld et al 2006). Enteric methane from fermentative digestion is the main source of these emissions. Thus when new or modified feeding systems are being researched the effects of these changes on enteric methane emissions should be monitored, in view of the need to reduce methane emissions so as to meet future targets for mitigating global warming.

A positive approach to the problem of how to reduce methane emissions from live stock has been to incorporate a low level (1%) of biochar in the diet (Sangkhom et al 2012; Leng et al 2012a,b,c). Biochar is the product of incomplete carbonization of fibrous biomass at high temperatures (Lehmann and Joseph 2009). It is a highly porous material which gives it valuable properties as a support mechanism for biofilms that may facilitate the adsorption of consortia of micro-organisms and nutrients (Leng 2014).

In the research reported here, it was hypothesized that: (i) the performance of growing goats fed Bauhinia acuminata as the basal diet would be improved by supplementation with water spinach as a rapidly fermentable protein source; and (ii) that incorporation of a low level of biochar in the diet might reduce enteric methane emissions.

Materials and methods

Location of the study area

The experiment was conducted in the Animal Science Farm and Laboratory of the Faculty of Agriculture and Forest Resource, Souphanouvong University, LuangPrabang Province, Lao PDR. The site is located 7.5 km from LuangPrabang Town to the South-west, at an altitude of 385m above sea level. The experiment was conducted from June to December 2014.

Treatments and experimental design

The experimental plan was a 2*2 factorial arrangement in a Randomized Completely Block Design (RCBD) with 4 treatments and four replications.

The factors applied to a basal diet of fresh Bauhinia foliage were:

•  With or without water spinach (WS and No-WS)

• With or without biochar (BC and No-BC)

Individual treatments were:

BA = Bauhinia acuminata ad libitum

BABC = Bauhinia acuminata ad libitum + 1% biochar on DM basis

BAWS = 70% Bauhinia acuminata and 30% water spinach on DM basis

BAWSBC = 70% Bauhinia acuminata and 30% water spinach + 1% biochar

Animals and management

Sixteen local weaned goats with initial average body weight of 12.9kg and 6-7 months of age were used. They included 4 males (non-castrated) and 12 females. These animals were purchased from Phoukhoun District, Luang Prabang Province. They were housed in individual pens made from wood and bamboo (dimensions of width 1 m, length 1 m and height 0.9 m) and designed to collect separately feces and urine (Photo 1).They were vaccinated against pasteurellosis and foot and mouth disease and treated with Ivermectin (1ml/20 kg live weight) to control internal and external parasites. They were adapted to the pens and the feeds for 7 days before starting the experiment. The experiment lasted 97 days, including the adaptation period.

Photo 1. Goats confined in the metabolism pens	Photo 2. Bauhinia acuminata foliage as presented to the goats

Feed and management

Molasses diluted to 10 Brix was used as the carrier for the biochar and was given ad libitum on all diets. Foliages of Bauhinia acuminata and water spinach were collected daily from natural stands in the University campus. They were hung in bunches above the feed trough (Photo 2). Fresh feeds were offered twice daily at 07:30 and 16:00h.

Data collection

Live weight was recorded in the morning before feeding at the beginning and at the end of the experiment and at intervals of 10 days during the experiment. Quantities of feed offered and refused were recorded daily. Every 10 days, samples were taken for analysis of DM and N. Samples of Bauhinia acuminata foliage offered and residues were separated into stem and leaves (containing attached petioles). Representative samples of each component were analyzed for DM, N and ash.

Samples of rumen fluid were taken by stomach tube 2h after morning feeding on the last day of the experiment. The pH value was measured immediately with a portable digital pH meter. A drop of concentrated sulphuric acid was added prior to determination of ammonia by steam distillation. Digestibility and N retention were recorded four times, over 5 days periods at 20 day intervals (after 20, 40, 60 and 80 days). In each collection period, samples of feeds offered and refused were taken daily and bulked for the 5 days of each period. Urine was collected in buckets containing 20ml of a solution of sulphuric acid (10% sulphuric acid concentrate + 90% distilled water). Feces were collected daily and stored in the refrigerator at 4-8ºC and at the end of each period, sub-samples were mixed together and ground with a coffee grinder.

Samples of eructed gases were measured on the last day of the experiment, in the morning 2h after feeding. The goats were placed in a plastic-covered cage (Photo 3) and after a period of 10 minutes for equilibration with the surrounding air, the concentrations of methane and carbon dioxide were recorded over a 10 minute period, using a GASMET 4030 meter (Gasmet Technologies Oy, Pulttitie 8A, FI-00880 Helsinki, Finland).

Photo 3. Goats were confined in a plastic-lined cage for the measurement of the eructed gases with the Gasmet meter	Photo 4. Taking rumen fluid by stomach tube

Chemical analyses

The sub-samples of feces and of feeds offered and refused were analysed for DM, N and ash according to AOAC (1990) methods. Urine was analysed for nitrogen (AOAC 1990).

Statistical analyses

Data for feed intake, N intake, N retention, live weight, pH, NH₃-N and CH₄:CO₂ were analysed with the General Linear Model option of the ANOVA program in the MINITAB software (Minitab 2000) Source of variation were: animals, periods, water spinach, biochar, interaction water spinach*biochar and error. The data for ratios of CH₄:CO₂ were analyzed using the repeated measure option in the GLM program in Minitab (2000).

Results and discussion

Chemical composition

The concentrations of crude protein and ash and the solubility of the protein were lower, and of DM were higher, in Bauhinia than in water spinach (Table 1).

Feed intake, growth rate and feed conversion

DM intake expressed as a percentage of live weight was not affected by supplementation with biochar or water spinach (Table 2).

Daily live weight gain and feed conversion were improved by feeding water spinach and by supplementation with biochar (Table 3; Figures 1 and 2). There was a close relationship between live weight gain and feed conversion ratio (Figure 4).

Figure 1 . Effect of biochar on live weight gain of goats fed Bauhinia acuminata with and without water spinach	Figure 2. Effect of supplementation with water spinach and biochar, separately or together, on the growth rate of goats fed a basal diet of foliage from Bauhinia acuminata

Figure 3. Effect of biochar compared with water spinach on feed conversion of goats fed Bauhinia acuminata and molasses as basal diet	Figure 4. Relationship between live weight gain and feed conversion in goats fed Bauhinia foliage and molasses supplemented or not with water spinach and biochar

Apparent digestibility and N retention

Supplementing the basal diet of Bauhinia and molasses with water spinach increased the apparent digestibility of DM, OM and crude protein, but there were no differences due to biochar (Table 4). Daily N retention, N retention as percent of N intake and of N digested were all improved by supplementation with water spinach. There was a tendency for biochar to improve daily N retention (p=0.082) and this effect was significant when N retention was expressed as a percent of N intake or of N digested (Figures 5 and 6).

Figure 5. Effect of biochar on N retention as % N intake of goats fed Bauhinia acuminata and molasses as basal diet with or without water spinach	Figure 6. . Effect of biochar on N retention as % N digested of goats fed Bauhinia acuminata and molasses as basal diet with or without water spinach

Rumen ammonia, pH and methane to carbon dioxide ratio

Rumen pH did not differ among the diets (Table 5). Rumen ammonia, which was high on all diets, was increased by supplementation with water spinach but was not affected by biochar.

 

Figure 7. Effect of supplementation with water spinach and biochar, separately or together, on rumen ammonia of goats fed a basal diet of foliage from Bauhinia acuminata

The ratio of methane to carbon dioxide in eructed breath of the goats was lower in the eructed breath of the goats supplemented with water spinach and not affected by supplementation with biochar (Figures 8 and 9).

Figure 8. Effect of water spinach on ratio of methane to carbon dioxide in eructed gas from goats fed either Bauhinia as basal diet	Figure 9. Effect of biochar on ratio of methane to carbon dioxide in eructed gas from goats fed either Bauhinia as basal diet

The results of this experiment agree with the findings of: (i) Kongmanila et al (2011) that supplementation with water spinach increased the digestibility of Mango foliage y growing goats; and (ii) Phongpanith et al (2013) who reported that water spinach supplementation increased the digestibility and N retention of goats fed Muntingia foliage. Presumably the high solubility of the protein in water spinach furnished amino acids and peptides required by micro-organisms for efficient rumen digestion, and that these were limited in the Bauhina foliage because of its low protein solubility.

In contrast with the report by Leng et al (2014), that biochar reduced methane emission from cattle fed urea-treated rice straw, in the present experiment with goats fed tree foliage there was no effect of biochar on methane emissions. However, in agreement with these authors, the biochar had a positive effect on growth performance.

Conclusions

• Goats fed Bauhinia foliage and molasses, supplemented with water spinach, grew faster and had better DM feed conversion, and higher apparent digestibility of DM and crude protein, and higher N retention, than goats fed only Bauhinia foliage and molasses.
  
  
• The higher value of rumen ammonia in goats fed water spinach reflected the greater solubility of the crude protein in the water spinach.
  
  
• Supplementing the basal diet of Bauhinia and molasses with water spinach led to a reduction in the methane/carbon dioxide ratio in the eructed breath of the goats.

Acknowledgements

This research was done by the senior author as part of the requirements for the PhD degree in Animal Production "Improving Livelihood and Food Security of the people in Lower Mekong Basin through Climate Change Mitigation". The authors acknowledge support for this research from the MEKARN II project financed by Sida. Special thanks to Mr Sisavard, Miss Sounivone and Miss Keud who provided valuable help in the farm and laboratory. They also thank the Faculty of Agriculture and Forest Resource, Souphanouvong University for providing the facilities to carry out this research.

References

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Received 4 February 2015; Accepted 25 February 2015; Published 3 March 2015

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