Effect on feed intake, digestibility and N balance in goats of supplementing a basal diet of Muntingia foliage with biochar and water spinach (Ipomoea aquatica)

Sengsouly Phongpanith, Sangkhom Inthapanya and T R Preston*

Animal Science Department, Faculty of Agriculture and Forest Resource, Souphanouvong University Lao PDR
ssl.souphanouvong@gmail.com
* Finca Ecologica, AA #48, Socorro, Santander, Colombia

Abstract

Four weaned female goats, with an initial body weight of 8-9 kg and 3 months of age, were assigned to 4 treatments arranged in a 4*4 Latin square with experimental peiods of of 14 days: 9 days for adaptation to the new diets and 5 days for collection of feces and urine. The factors were: Muntingia as the only forage or Muntingia supplemented with water spinach; and biochar at 1% of the diet DM or no biochar.  

Feeding water spinach along with Muntingia foliage led to increases in DM intake, apparent crude protein digestibility and N retention. These effects appear to have been caused by the increased crude protein content of the diet when the water spinach was fed (12.8 versus 9.4% in the DM). When the N retention data were corrected for differences in N intake the beneficial effects of the water spinach were no longer apparent (P=0.22).  There were no differences in feed intake, apparent digestibility coefficients and N retention due to addition of biochar. It was concluded that the Latin square changeover design was not suitable as a means of testing the effects of biochar on these parameters due to carryover effects of the biochar from one period to the next.

Keyword: Carryover effects, covariance, N retention

Introduction

The great challenge is to make the goats become environmentally friendly through the changing of the free range farming system to stall feeding system. Farmers tend to restrict their herds in order to avoid excessive damage to crops, for which the owner is held responsible. In recent years (Phengsavanh and Ledin 2003), goat management practices have been changing, and vary from site to site depending mostly on land availability, labor and community regulations. Goats are reared only for meat and they reach a mature weight of about 40 kg in 2-3 years under local conditions. First kidding is at 12-18 months of age, usually a single kid at the first litter and twin kids later. Goats produce meat, milk, skins and fiber for sale or family consumption. They have an ability to survive on low quality feeds or in difficult conditions on relatively small amounts of feed and they also have a higher reproduction rate compared to cattle (Steel 1996).

According to Simbaya (2002) and Phengsavanh (2003) the major feed resources for the ruminants in Laos are native grasses, legumes and fodder tree leaves that are available around the farms and in the forest. Improved nutrition requires increasing the energy density of the diet, ensuring efficient rumen function and providing a complimentary source of bypass protein (Preston and Leng 2009). 

Muntingia calabura belonging to the family Elaeocarpacae grows everywhere in Lao PDR (sandy land, humid areas, and high land area) and is well adapted to the dry season. The farmers use it as shade tree around the homestead, and along the roadside. It is a tall tree with a large canopy of leaves but it is not normally fed to animals (Nguyen Xuan Ba et al 2003). Pok Samkol (2003) reported that the foliage was palatable to goats; and that DM intake was higher when the foliage was offered hanging in the feed trough compared with giving the leaves alone. As a strategy to improve the nutritive value of foliages of low nutritive value to goats, Kongmanila et al (2007) and Kongmanila et al (2011) reported positive responses in feed intake and N retention when foliage from the Mango tree [which is  rich in tannins and of low digestibility (Kongmanila et al 2007)], was supplemented with water spinach (Ipomoea aquatica), the protein in which is considered to be highly degradable by rumen microbes  (Kongmanila et al  (2007). 

A recent development arising from studies on promoting renewable sources of energy has been the finding that biochar -  the residue from the gasification of rice husks - appeared to act as a biofilm in rumen fermentation studies with beneficial effects manifested by reduced production  of enteric methane and better growth rates when added at low levels to cattle diets (Leng et al 2012).

The aim of the present study was therefore to examine the combined effect of water spinach and biochar on the feed intake, digestibility and N balance of goats fed a basal diet of Muntingia foliage.

Materials and Methods

The experiment was carried out at the farm of Souphanouvong University, which is located about 7.5 km from Luang Prabang district, Lao PDR. The experiment was conducted from September to October 2012. 

Animals and management 

Four female goats with body weights in the range from 8 to 9 kg and 3 months of age were housed individually in metabolism cages made from bamboo (dimensions of width 0.8 m, length 0.9 m and height 0.9 m) and designed to collect separately feces and urine (Photo 1). The goats were vaccinated against Pasteurellosis and Foot and mouth disease and treated with Ivermectin (1ml/33 kg live weight) to control internal and external parasites. They were gradually introduced to the cages and diets over 7 days before beginning the experiment.

Photo 1: Goats confined in the metabolism cages

 Treatments and design

The treatments arranged in a 4*4 Latin square (Table 1) were:

·         MC-B: Muntigia foliage with biochar

·         MC: Muntigia foliage with no biochar

·         MC-WS: Muntigia foliage with water spinach

·         MC-B-WS: Muntigia foliage with water spinach and biochar

Experimental periods were of 14 days: 9 days for adaptation to the new diets and 5 days for collection of feces and urine.

 A small amount of finely chopped sugar cane  was fed in all the diets as a carrier for the biochar which was given at the rate of 1% of the diet DM intake. 

Feeds and feeding system 

Muntingia, water spinach and sugar cane were collected daily from areas around Souphanouvong University. The Muntingia and water spinach were hung in bunches above the feed trough.  The biochar was produced  by burning rice husks in a top lit updraft (TLUD) gasifier stove (Olivier 2010). The biochar was mixed with the sugar cane which was chopped (Photo 2)  and offered in a plastic bucket at 10% of diet DM. The Muntigia foliage was fed ad libitum; water spinach was offered at 30% of diet DM intake.   Feeds offered and residues were weighed every morning.

Photo 2: Chopping the sugarcane stalk

Measurements 

In the digestibility trial, feeds offered and refused were recorded daily during the collection period. Muntigia foliage and water spinach were separated into leaves and stems to estimate the average proportions of each. During the collection period the refusals were also separated into leaves and stem in order to measure the selection of the different parts.  

During the data collection periods, the feces and urine were recorded twice daily at 7:00  and 17:00 . At each  time, 10% of the feces was sampled and frozen at –20^oC. Urine was collected in a jar containing 50 ml of 10% sulphuric acid (urine pH<3) to preserve the nitrogen. A sample of 10% of the urine was stored at 4^oC for further analysis.

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

Data analysis 

The data were analyzed by the General Linear Model option in the ANOVA program of the Minitab (2000) software. Sources of variation in the model were: goats, periods, effect of biochar, effect of water spinach,  interaction biochar*water spinach and error.

Results and Discussion

Muntigia foliage was low in crude protein (CP) and in ash (Table 2); by contrast the water spinach foliage was high in both CP and ash.

There were no differences in feed intake, apparent digestibility coefficients and N retention due to addition of biochar (Table 3). In retrospect, the experimental design was not suitable as a means of testing the effects of biochar on these parameters. As biochar is believed to act by forming a biofilm within the fermentation medium (Leng et al 2012a), it is to be expected there would be carryover effects beyond the 14 day periods during which the biochar was fed or not fed. This would inevitably mask the potential benefits that have been shown to occur in a long-term feeding trial (Leng et al 2012b).

There were major benefits from feeding water spinach along with the Muntingia foliage (Table 3). DM intake was increased 32%, apparent DM digestibility tended to increase (P=0.14),  crude protein digestibility increased by 10% and N retention by 94%. All these effects appear to have been caused by the increased crude protein content of the diet when the water spinach was fed (12.8 versus 9.4% in the DM). When the N retention data were corrected for differences in N intake the effects of the water spinach were no longer apparent (P=0.22).  These effects of  increasing intake of diet DM, and especially of the dietary concentration of crude protein, with resultant improvements in N retention, are similar to those observed by Kongmanila et al (2007) when they supplemented Mango foliage with water spinach.  

Conclusion

·         Feeding water spinach along with Muntingia foliage led to increases in DM intake, apparent crude protein digestibility and N retention. These effects appear to have been caused by the increased crude protein content of the diet when the water spinach was fed (12.8 versus 9.4% in the DM). When the N retention data were corrected for differences in N intake the benefial effects of the water spinach were no longer apparent (P=0.22).

Acknowledgement

The authors acknowledge support for this research from the MEKARN project. Special thanks to Mr Thonglone Sengkhamkong and Mr Chanhthachon Phanthavong who provided valuable help in the farm. We also thank the staff of the Department of Animal Science, Faculty of Agriculture and Forest Resource, Souphanouvong University for providing the facilities to carry out this research. 

References

AOAC 1990 Official Methods of Analysis. Association of Official Analytical Chemists. 15th Edition (K Helrick editor). Arlington pp 1230. 

Kongmanila Daovy, Preston T R  and Ledin Inger 2007 Chemical composition, digestibility and intake of some tropical foliage species used for goats. MSc Thesis, MEKARN-SLU http://www.mekarn.org/MSC2005-07/theses07/daov1.htm

Kongmanila D, Phommachanh K and Preston T R 2011 Effect on growth rate and digestibility in goats of supplementing a basal diet of mango foliage with fresh water spinach (Ipomoea aquatica). Livestock Research for Rural Development. Volume 23, Article #203. http://www.lrrd.org/lrrd23/10/daovy23203.htm

Leng R A, Inthapanya S and Preston T R 2012a Biochar lowers net methane production from rumen fluid in vitro. Livestock Research for Rural Development. Volume 24, Article #103. http://www.lrrd.org/lrrd24/6/sang24103.htm

Leng R A, Preston T R and Inthapanya S 2012b 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

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Olivier P 2010 The Small-Scale Production of Food, Fuel, Feed and Fertilizer; a Strategy for the Sustainable Management of Biodegradable Waste. http://www.mekarn.org/workshops/pakse/html/olivier.docx 

Phengsavanh P 2003 Goat production in smallholder farming systems in Lao PDR and the possibility of improving the diet quality by using Stylosanthes guianensis CIAT 184 and Andropogon gayanus cv Kent. MSc. Thesis. Department of Animal Nutrition and Management, Swedish University of Agricultural Sciences, Uppsala, Sweden  

Pok Samkol 2003 Effect of method of offering Muntingia (Muntingia calabura) foliages to goats on intake and feeding behaviour;  Retrieved December 11, 110, from MEKARN Mini-projects. http://www.mekarn.org/msc2003-05/miniprojects/web page/samkol.htm  

Preston T R and Leng R A 2009 Matching ruminant production systems with available resources in the tropics and sub- tropics. Penambul Press: Armidale, Australia http://www.utafoundation.org/P&L/preston&leng.htm 

Simbaya J 2002 Potential of tree fodder/shrub legumes as feed resources for dry season supplementation of smallholder ruminant animals. National Institute for Scientific and Industrial Research, Livestock and Pest Research Centre, Chilanga, Zambia 69-76.   

Steele M 1996 Goats. The Tropical Agriculturalist. Macmillan Education, Between Towns Road, Oxford.

Received 27 December 2012; Accepted 27 January 2013; Published 5 February 2013

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