Effect of biochar and water spinach on feed intake, digestibility and N-retention in goats fed urea-treated cassava stems

Le Thi Thuy Hang, T R Preston¹, R A Leng² and Nguyen Xuan Ba³

Faculty of Animal Sciences and Veterinary Medicine, Agricultural and Natural Resources Faculty, An Giang University, Vietnam
thuyhang.agu@gmail.com
¹ Centro para la Investigación en Sistemas Sostenibles de Producción Agropecuaria (CIPAV), Carrera 25 No 6-62 Cali, Colombia
² University of New England, Armidale, NSW 2351, Australia
³ Hue College of Agriculture and Forestry, Hue University, Vietnam

Abstract

Four “Bach Thao” goats (LW 14 ± 2 kg) were fed urea-treated cassava stems alone (UCS) or with a supplement of water spinach at 1% of LW (DM basis) (UCSW), with biochar (derived by carbonization of rice husks in an updraft gasifier stove) at 1% of DM intake (UCSB) or with water spinach + biochar (CSWB). The design was a Latin square with four treatments and four periods, each lasting 15 days (ten days for adaptation and 5 days for collection of feces and urine).

Urea treatment of the cassava stems increased the crude protein from 5.5 to 11.7% in DM. DM intake was increased 18% by supplementing the urea-treated cassava stems with biochar. Addition of water spinach increased total DM intake by 25% while the combined effect of biochar plus water spinach was to increase intake by 41%. Biochar increased daily N retention by 46% and the biological value of the absorbed N by 12%. Biochar provides no protein to the diet, thus it is postulated that the increase in N retained and in its biological value came about as a result of the biochar stimulating rumen microbial growth resulting in an increase in synthesis and hence of absorption of amino acids. We suggest that biochar effectively functions as a “prebiotic” – stimulating the activity of beneficial microbial communities through its support for biofilms in the digestive tract of the animal.

Key words: biofilms, biological value, microbial communities, prebiotic

Introduction

Major advances have been made recently in the integrated use of the cassava plant as a means of intensifying ruminant livestock production. A system of fattening cattle intensively on cassava pulp (the residue after industrial starch extraction) was developed by Phanthavong et al (2014, 2015), in which urea provided rumen fermentable ammonia and bypass protein was supplied by brewers’ grains at 30% of the diet. In a follow-up series of experiments it was shown that fresh cassava foliage could replace the major part of the brewers’ grains as bypass protein source, provided that a small amount of brewers’ grains (4 to 5% of the diet DM) was retained apparently acting as a “prebiotic” to counteract the potential toxicity of the HCN released from the cyanogenic glucosides in the cassava foliage (Inthapanya et al 2016; Binh et al 2017). The system was further developed to use ensiled cassava root as the carbohydrate energy source with a local “rice wine” byproduct replacing the brewers’ grains as the source of prebiotic (Sengsouly et al 2016; Inthapanya et al 2017).

An experiment with growing goats fed almost exclusively (95% of the diet DM) on fresh cassava foliage (Sina et 2017),confirmed the vital role of the small supplement of brewers’ grains’ in a cassava-based feeding system. Growth performance was more than doubled from 65 to 160g/day when the brewery byproduct was included at 5% of the diet DM.

Increased understanding of the role of prebiotics as support for biofilms and their associated microbial communities involved in the animal’s digestive system led to an appraisal of the potential role of biochar as a prebiotic, following it’s known ameliorating properties in soils (Lehmann 2007; Preston 2015) thought to be due to its interactive role in supporting microbial communities in this medium.

In an initial study with 1% biochar in the diet (Leng et al 2012), growth rates were increased 20% but were probably constrained by errors in management of the feed resource (fresh cassava root) that probably propitiated growth of mycotoxins (R A Leng, personal communication). More recent studies have shown synergistic effects from combining biochar with rice distillers’ byproduct in a cassava-based diet for fattening cattle (Sengsouly et al 2016) and by combining biochar with water spinach in diets of goats (Silivong et al 2015, 2016).

On the basis of this background, the present experiment was designed with the aim of determining if the synergistic effects of biochar and water spinach on growth of goats fed foliage of Bauhinia accuminata would be equally manifested when the basal diet was composed of urea-treated cassava stems, shown to be a potential feed resource for goats by Thanh et al (2013).

Materials and methods

Experimental design

The experiment was conducted from June to September 2015 at An Giang University farm, An Giang province, Vietnam. Four “Bach Thao” goats (14 ± 2 kg) were fed urea-treated cassava stems alone (UCS) or with a supplement of water spinach at 1% of LW (DM basis) (UCSW), with biochar at 1% of DM intake (UCSB) or with water spinach + biochar (CSWB). The design was a Latin square (Table 1) with four treatments and four periods, each lasting 17 days (12 days for adaptation and 5 days for collection of feces and urine).

Animals and management

The goats were housed in metabolism cages made from bamboo, designed to collect separately feces and urine. They were vaccinated against Pasteurellosis and Foot and Mouth disease and treated with Ivermectin (1ml/10 kg live weight) to control internal and external parasites. They were weighed between 06:30 and 07:30h before feeding at the start and end of each experimental period.

Feeds and feeding

The cassava (sweet variety) was planted in sandy soil in the An Giang University farm. from January to August 2015. It was fertilized (per ha) with 8 tonnes of cattle manure, 175 kg urea, 200 kg super-phosphate and 130 kg potassium chloride.

The cassava stems (no leaves; Photo1) were harvested at 30-40cm above soil level at intervals of 150 days when it had attained a height of 100 - 120 cm. The cassava stems were chopped by machine (Photo 2), mixed with urea (3% DM basis; no water was added) and ensiled in closed plastic bags after first extracting the air (Photo 4). They were ensiled for 21 days (Photo 5), after which they were fed ad libitum as the basal diet of the goats (Photo 6).

Photo 1. Freshly harvested cassava stems	Photo 2. Chopping into 5-10 cm lengths	Photo 3. Urea added at 3% of stem DM
Photo 4. Chopped stems-urea are put in polyethylene bags and the air extracted	Photo 5. Urea-treated stems are stored for 21 days	Photo 6. Urea-treated stems after 21-day storage ready for feeding

The biochar was made by combusting rice husks in an updraft gasifier stove (Photo 7). The chosen amounts were offered twice daily in troughs separate from the cassava stem (Photo 8).

Before starting the experiment, it took several days to accustom the goats to eat the biochar. First, biochar was mixed with small quantities of rice bran and water spinach. After, 3-4 days all the goats were eating this mixture. Then the rice bran and water spinach were gradually removed over the following 3-4 days.  During the experiment, when the diets were changed from “no biochar” to “biochar” [eg: “UCSW to UCSWB] it required only 1 to 2 days for the goats to adapt to the biochar as they had already been accustomed to eat it before the experiment began.

Photo 7. The biochar was the residue from rice husks used as fuel in a gasifier stove (Paul Olivier)

Photo 8.  Biochar, water spinach and urea-treated cassava stems were fed in separate troughs

Feed refusals were weighed every morning prior to giving the new feed. Samples of each diet component were taken daily, stored at -18C, and bulked at the end of each period for analysis.

Digestibility and N retention

During the data collection periods, the feces and urine were recorded twice daily at 7:00 am and 16:00pm and added to jars containing 100 ml of 10% (v/v) sulphuric acid. The pH was measured and, if necessary, more acid added to keep the pH below 4.0. After each collection period: (i) a sample of 10% of the urine was stored at ­-4^o C for analysis of nitrogen (AOAC 1990); (ii) the feces were mixed and a sample (10%) stored frozen at -20^oC.

Statistical analysis

Data were analyzed with the General Linear Model option of the ANOVA program in the MINITAB software (Minitab 2000). Sources of variation were treatments, animals, periods and error.

Results and discussion

Composition of the diet ingredients

Urea-treatment of the cassava stems doubled the crude protein content (Table 2). The WRC value (water retention capacity) of 4.4 liters of water per 1 kg of biochar is similar to that reported for combustion of rice husks in a down-draft gasifier (Orosco et al 2018), and indicates that the biochar had a high “adsorptive” capacity.

DM intake was increased 18% by supplementing the urea-treated cassava stems with biochar which was fed separately {Photo 8) at 1% of the diet DM (Table 3; Figure 1). Addition of water spinach increased total DM intake by 25% while the combined effect of biochar plus water spinach was to increase intake by 41%.

Figure 1. Effect of biochar on DM intake goats fed urea-treated cassava stems, with or without fresh water spinach and with or without biochar

Coefficients of apparent DM digestibility were increased more by biochar (by 9%) than by water spinach (2.4%) (Table 4; Figures 2 and 3). The combined effect of biochar plus water spinach was to increase DM digestibility by 12%. Results for organic matter were similar. Digestibility coefficients for crude protein have no real meaning when the major part of the dietary nitrogen (40-50%) is in the form of NPN (urea and ammonia) derived from urea-treatment of the cassava stems.

Figure 2. Effect of water spinach on DM digestibility in goats fed urea-treated cassava stems with or without a supplement of biochar	Figure 3. Effect of biochar on DM digestibility in goats fed urea-treated cassava stems with or without a supplement of water spinach

The most dramatic effects of biochar supplementation were on N retention (Table 5; Figures 4 and 5) and the biological value of the protein absorbed (calculated as the N retained as percent of N digested) (Figures 6 and 7). Biochar increased daily N retention by 46% on the diet of urea-treated cassava stems and by 21% when water spinach replaced half of the urea-treated cassava stems (Table 5). Comparable values for the increases in biological value of the protein were 12 and 4%.  Biochar provides essentially no protein (0.0037% CP in diet DM) thus the increase in N retained and in its biological value can only have come about as a result of the biochar stimulating rumen microbial growth resulting in an increase in synthesis and hence in absorption of amino acids. It is hypothesized that biochar promotes habitat for micro-organisms that detoxify phytotoxins (Leng 2017); and that the “free” selection of biochar is an example of
“self-medication”, similar to that reported by Struhsaker et al (1997). These authors reported that: “charcoals adsorb organic materials, such as phenolics, particularly well and, as a consequence, remove these compounds, which have the potential to be toxic or interfere with digestion or both”.

Figure 4. Effect of water spinach on N retention in goats fed urea-treated cassava stems with or without a supplement of biochar	Figure 5. Effect of biochar on N retention in goats fed urea-treated cassava stems with or without a supplement of water spinach
Figure 6. Effect of water spinach on N retention as % of digested N in goats fed urea-treated cassava stems with or without a supplement of biochar	Figure 7. Effect of biochar on N retention as % of digested N in goats fed urea- treated cassava stems with or without a supplement of water spinach

Conclusions

• Urea treatment of the cassava stems increased the crude protein from 5.5 to 11.7% in DM.
  
  
• DM intake was increased 18% by supplementing the urea-treated cassava stems with biochar.
  
  
• Addition of water spinach increased total DM intake by 25% while the combined effect of biochar plus water spinach was to increase intake by 41%.
  
  
• Biochar increased daily N retention by 46% and the biological value of the absorbed N by 12%. Biochar provides no protein to the diet, thus it is postulated that the increase in N retained and in its biological value came about as a result of the biochar stimulating rumen microbial growth resulting in an increase in synthesis and hence of absorption of amino acids.
  
  
• We suggest that biochar functions as a “prebiotic” – facilitating the activity of beneficial microbial communities that enhance fermentation or remove the effects of phytotoxins or mycotoxins.

Acknowledgments

This research is part of the requirement by the senior author for the degree of PhD at Hue University of Agriculture and Forestry, Hue University, Vietnam.  The authors acknowledge support for this research from the MEKARN II project financed by Sida; and the University of An Giang, Vietnam.

References

AOAC 1990: Official methods of analysis. 15th ed. AOAC, Washington, DC

Binh P L T, Preston T R, Duong K N and Leng R A 2017 : A low concentration (4% in diet dry matter) of brewers’ grains improves the growth rate and reduces thiocyanate excretion of cattle fed cassava pulp-urea and “bitter” cassava foliage. Livestock Research for Rural Development. Volume 29, Article #104. http://www.lrrd.org/lrrd29/5/phuo29104.html

Inthapanya S, Preston T R and Leng R A 2016; Ensiled brewers’ grains increased feed intake, digestibility and N retention in cattle fed ensiled cassava root, urea and rice straw with fresh cassava foliage or water spinach as main source of protein. Livestock Research for Rural Development. Volume 28, Article #20. http://www.lrrd.org/lrrd28/2/sang28020.htm

Inthapanya S, Preston T R, Phung L D and Ngoan L D 2017: Effect of supplements of yeast (Saccharomyces cerevisiae), rice distillers’ by-product and fermented cassava root on methane production in an in vitro rumen incubation of ensiled cassava root, urea and cassava leaf meal. Livestock Research for Rural Development. Volume 29, Article #220. http://www.lrrd.org/lrrd29/12/sang29220.html

Lehmann J 2007: A handful of carbon. Nature447, 143-144 http://www.css.cornell.edu/faculty/lehmann/publ/Nature%20447,%20143-144,%202007%20Lehmann.pdf

Leng R A, Preston T R and Inthapanya S 2012 : Biochar reduces enteric methane and improves growth and feed conversion in local “Yellow” cattle fed cassava root chips and fresh cassava foliage. Livestock Research for Rural Development. Volume 24, Article #199. http://www.lrrd.org/lrrd24/11/leng24199.htm

Leng R A 2017 : Biofilm compartmentalisation of the rumen microbiome: modification of fermentation and degradation of dietary toxins. Animal Production Science Review https://doi.org/10.1071/AN17382

Minitab 2000: Minitab user's guide. Data analysis and quality tools. Release 13.1 for windows. Minitab Inc., Pennsylvania, USA.

Orosco J, Patiño F J, Quintero M J and Rodríguez L 2018 : Residual biomass gasification on a small scale and its thermal utilization for coffee drying. Livestock Research for Rural Development. Volume 30, Article #5. http://www.lrrd.org/lrrd30/1/jair30005.html

Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2014 : Cassava pulp as livestock feed; effects of storage in an open pit. Livestock Research for Rural Development. Volume 26, Article #169. http://www.lrrd.org/lrrd26/9/phan26169.htm

Phanthavong V, Viengsakoun N, Sangkhom I and Preston T R 2015 Effect of biochar and leaves from sweet or bitter cassava on gas and methane production in an in vitro rumen incubation using cassava root pulp as source of energy. Livestock Research for Rural Development. Volume 27, Article #72. http://www.lrrd.org/lrrd27/4/phan27072.html

Philavong S, Preston T R and Leng R A 2017: Biochar improves the protein-enrichment of cassava pulp by yeast fermentation. Livestock Research for Rural Development. Volume 29, Article #241. http://www.lrrd.org/lrrd29/12/somp29241.html

Preston T R 2015; The role of biochar in farming systems producing food and energy from biomass. In: Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration and Reversing CO2 Increase (Editor: Thomas J Goreau) CRC Press, Tayler and Francis Group, Boca Raton, Florida USA

Sengsouly P and Preston T R 2016: Effect of rice-wine distillers’ byproduct and biochar on growth performance and methane emissions in local “Yellow” cattle fed ensiled cassava root, urea, cassava foliage and rice straw. Livestock Research for Rural Development. Volume 28, Article #178. http://www.lrrd.org/lrrd28/10/seng28178.html

Silivong P and Preston T R 2015: Growth performance of goats was improved when a basal diet of foliage of Bauhinia acuminata was supplemented with water spinach and biochar. Livestock Research for Rural Development. Volume 27, Article #58. http://www.lrrd.org/lrrd27/3/sili27058.html

Silivong P and Preston T R 2016 : Supplements of water spinach (Ipomoea aquatica) and biochar improved feed intake, digestibility, N retention and growth performance of goats fed foliage of Bauhinia acuminata as the basal diet. Livestock Research for Rural Development. Volume 28, Article #98. http://www.lrrd.org/lrrd28/5/sili28098.html

Sina V, Preston T R and Tham T H 2017 : Brewers’ grains have a synergistic effect on growth rate of goats fed fresh cassava foliage (Manihot esculenta Crantz) as basal diet. Livestock Research for Rural Development. Volume 29, Article #137. http://www.lrrd.org/lrrd29/7/sina29137.html

Struhsaker T T, Cooney D O and Siex K S 1997 Charcoal Consumption by Zanzibar Red Colobus Monkeys: Its Function and Its Ecological and Demographic Consequences. International Journal of Primatology, 18: 61-72. doi: 10.1023/A:1026341207045

Thanh T X, Hue K T, Anh N N and Preston T R 2013 : Comparison of different forages as supplements to a basal diet of chopped cassava stems for growing goats. Livestock Research for Rural Development. Volume 25, Article #7. http://www.lrrd.org/lrrd25/1/than25007.htm

Received 16 March 2018; Accepted 27 April 2018; Published 1 May 2018

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