Effect on growth of goats and enteric methane emissions of supplementing foliage of Melia azedarach with foliage of Mimosa pigra

Bui Phan Thu Hang, Vo Lam and T R Preston*

Angiang University, Faculty of Agriculture and Natural Resources, Vietnam
bpthang@agu.edu.vn
*TOSOLY, AA48 Socorro, Santander, Colombia

 Abstract

Sixteen weaned crossbred goats (Bach Thao x local female) with an initial weight between 10 and 12 kg and 3 to 4 months of age were used to evaluate the growth rate and methane emissions when fed a basal diet of Melia azedarach supplemented with Mimosa pigra. The design was Completely Randomized  (CRD) with 4 treatments: levels of Mimosa pigra of 0, 0.5, 1.0 and 1.5 (as DM % of LW).

Replacing Melia azedarach  with Mimosa pigra foliage in diets of goats reduced enteric methane emissions linearly reaching a maximum of 43% at the 22% level  of substituion, after which methane emissions rose again. Growth rates and feed conversions rates were similar for all levels of substitution of Melia azedarach by Mimosoa pigra and were unrelated to rate of emissions of enteric methane.

Key words: Browse, climate change, greenhouse gases

Introduction

Mimosa pigra is an invasive weed that is spread by seeds over many areas in South East Asia, especially on river banks and other wet areas. The rapid spread of this weed has become a complicating factor in land use management for the farmers. Suggested ways to control Mimosa pigra are by harvesting the plant for fire-wood or harvesting the foliage for animals, cutting or grazing it before flowering and seeding (Miller 1988). Recent research has shown that Mimosa has a high nutritive value for goats supporting growth rates of over 100 g/day when grazed in situ (Thu Hong et al 2008) and of over 80 g/day when fed in confinement as the sole feed (Thu Hong and Vo Lam 2011).  It was hypothesized that the presence of condensed tannins in the mimosa leaves conferred rumen "bypass"  properties to the proteins, a process known to improve the protein: energy ratio of absorbed nutrients leading to improved animal productivity (Preston and Leng 2009).

Melia azedarach is a found throughout Vietnam, traditionally being used for timber. The fruits are thought to be poisonous to humans and to some other mammals (Batcher 2000). However, we have fed it successfully to growing goats at levels up to 70% of the diet replacing ensiled water hyacinth leaves (Bui Phan Thu Hang et al 2012).

The aim of the present experiment was to ascertain if supplementation of Melia azedarach foliage with Mimosa would lead to growth rates exceeding the 70 g/day previously reported for combinations of Melia azedarach and ensiled water hyacinth (Bui Phan Thu Hang et al 2012). 

Materials and Methods

Location and climate of the area

The experiment was located in a private farm in Tinh Bien district, Long Xuyen city, An Giang province, that had collaborated in the conduct of the previous experiment with Melia azedarach (Bui Phan Thu Hang et al 2012).   

Experimental design

Weaned Bach Thao goats were fed a basal diet of  Melia azedarach as the sole feed or supplemented with  0.5, 1.0 or 1.5% of LW (DM basis) of fresh foliage of Mimosa pigra. The allocation to treatments was according to  a Completely Randomized Design (CRD) with 4 replications.

Feeds, animals and management

Mimosa pigra and Melia azedarach foliages were hung in bunches above the feed trough with 50% of the daily supply offered at 08.00h and the remainder at 17.00h.  Amounts offered were decided weekly based on individual weights of the goats. Fresh water and mineral licks were  supplied ad libitum.

The sixteen weaned Bach Thao crossbred goats were bought from smallholder goat keepers in An Giang province and housed in individual cages. The initial weights were 12 (±0.9) kg with an age range of  3 to 4 months.. They were de-wormed with Ivermectin and vaccinated against foot-and-mouth disease.The goats were weighed at the start of the experiment and then weekly, at the same day of the week and before feeding in the morning. The experiment lasted 90 days

On the ??th day during the last week of the experiment, the carbon dioxide and methane in eructed gases were measured. The gases were collected in the morning (time???)  by placing the goats in a plastic-covered cage (Photo 2) and after a period of 5 minutes for equilibration with the air in the box, 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). The CH₄ and CO₂ concentrations in background air in the building were recorded at the same time. The methane to carbon dioxide ratios were used to calculate the reduction  of methane according to the formula proposed  by Madsen et al (2010).

Chemical analysis

Samples of feeds offered and feed refusals were analysed for DM, CP and ash according to AOAC (1990).  NDF and  ADF were measured according to Van Soest et al (1991). 

Statistical analysis

The data from the experiment were subjected to analysis of variance using the General Linear Model (GLM) procedure of Minitab Software Release version 15 (2007). Sources of variation were: treatments and error.

Results and Discussion

The DM and CP contents of Melia azedarach were similar to those in Mimosa pigra, but NDF and ADF components were much lower (Table 1).

Supplementation of Melia azedarach with Mimosa pigra at the 0.5% LW level led to a 20% increase in DM intake; however, at higher levels  of Mimosa,  feed intake decreased but was still higher than on Melia alone (Table 2; Figure 1).

There were no differences in growth rates nor in  feed conversion for the different levels of supplementation with Mimosa pigra (Table 3; Figure 2).  A DM feed conversion in the range of 6:1 to 7:1  is considered a good result for an all-forage diet fed to growing goats.

Enteric methane emissions decreased as the proportion of Mimosa in the diet DM increased to 22% then rose as the proportion of mimosa increased to 33%. With 22% mimosa in the diet the reduction in methane emissions was 43% as compared with Melia alone. We have no explanation for these trends which appeared to be unrelated to animal performance.

Conclusions

• Replacing Melia azedarach  with Mimosa pigra foliage in diets of goats reduced enteric methane emissions linearly reaching a maximum of 43% reduction at the 22% level  of substitution, after which methane emissions rose again

• Growth rates were high (80 to 90 g/day) for all levels of substitution of Melia azedarach by Mimosoa pigra and were unrelated to rate of emissions of enteric methane.

Acknowledgements

The authors are grateful for the support from the MEKARN project, financed by the Sida-SAREC agency. The authors would also like to thank the Department of Animal Husbandry and Veterinary, Faculty of Agriculture and Natural Resources of An Giang University for infrastructure support.

References

AOAC 1990 Official Methods of Analysis, 15th edition. Association of the Official Analytical Chemists. Washington D.C.

Batcher M S 2000 Element Stewardship Abstract for Melia azedarach. The Nature Conservancy.

Bui Phan Thu Hang, Vo Lam and Preston T R 2012 Effects on the performance of growing goats by supplementing ensiled water hyacinth leaves with Melia azedarach foliage.  Proceedings of the International Conference "Livestock-Based Farming Systems, Renewable  Resources and the Environment", 6-9 June 2012, Dalat, Vietnam (Editors: Reg Preston and Sisomphone Southavong) http:/www.mekarn.org/workshops/dalat2012/html/thuhangagu1.htm

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Minitab 2007 Minitab Reference Manual, Release 15 for Windows. Minitab Inc, USA.

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