Development and Use of Rumen Molecular Techniques for Predicting and Enhancing Livestock Productivity
Closed for proposals
Project Type
Project Code
D31024CRP
304Approved Date
Status
Start Date
Expected End Date
Completed Date
11 October 2010Description
The world's livestock sector is amidst a massive transformation, fuelled by high demand for meat and milk, which is likely to double over the next two decades in developing countries. The major driving force behind this soaring demand for livestock products is a combination of population growth, urbanization and income growth, especially in developing countries. The challenge is to enhance animal productivity without any adverse effects on environment.
A large proportion of the global ruminant population is located in tropical environments, where animals feed predominantly on low quality highly fibrous forages. Recent studies in respiration chambers have confirmed that methane emissions from ruminants fed on fibrous diets are higher than outputs from better quality temperate forages. The excretion of methane from the rumen can represent a loss of up to 15% of the digestible energy depending on the type of diet. Therefore, reducing methane production could benefit the ruminant energetically provided the efficiency of ruminal metabolism is not compromised. The challenge therefore is to devise strategies, which reduce methane emissions from ruminants and improve production efficiency.
Current approaches to the evaluation of digestibility and nutritive value of feed resources using conventional in vitro feed evaluation and animal studies have resulted in a large body of information about nutrient composition, digestion kinetics and digestibility. However, these techniques are unable to describe the microbial mechanisms involved in ruminal digestion, and are unlikely to result in the development of rational feeding strategies.
Conventional culture-based methods of enumerating rumen bacteria are being rapidly replaced by the development of nucleic acid based techniques which can be used to characterise complex microbial communities. The foundation of these techniques is SSU rDNA (eg. 16S rRNA sequences) sequence analysis which has provided a phylogenetically based classification scheme for enumeration and identification of microbial community members. The molecular based ecology techniques are also likely to provide better insight into the interactions between methanogens and the other rumen microorganisms. All this information should assist in the development of strategies for improving production by reducing methanogenesis.
The Overall Objective of this CRP is to improve ruminant performance through a reduction in methane production. It is aimed to: i) reduce the level of methane production by up to 50% in animals fed roughage diets, ii) increase microbial protein and energy supply through reduced methane production using approaches such as inhibitors of methanogens, dietary approaches (e.g. use of polyunsaturated fatty acids or ingredients containing these acids), supplementation strategies, etc, iii) build in-country capacity to develop and use molecular techniques for studying rumen function, iv) develop molecular probes for quantifying populations of methanogens, fibre degrading bacteria, fungi and protozoa, v) correlate methane production to methanogen numbers, vi) determine effects of reduced methanogen numbers on fibre degrading bacteria, fungi and protozoa. Through these investigations, feeding strategies and or supplements that reduce methane production and improve productivity in ruminants on tropical diets will be developed, and better insight into the mechanism of feed digestion particularly interactions between various groups of rumen microorganisms will be available. This would lead to development of guidelines for reduction in methane emission and enhancement of animal productivity, for use at a wider scale.
Objectives
To improve ruminant performance through a reduction in methane production
Specific objectives
Build in-country capacity to develop and use molecular techniques for studying rumen function.
Correlate methane production to methanogen numbers.
Determine effects of reduced methanogen numbers on fibre degrading bacteria, fungi and protozoa.
Develop and use molecular probes for quantifying populations of methanogens, fibre degrading bacteria, fungi and protozoa.
Identify naturally occurring plant secondary compounds that inhibit methanogens.
Increase microbial protein and energy supply through reduced methane production using approaches such as inhibitors of methanogens, dietary approaches (e.g. use of polyunsaturated fatty acids or ingredients containing these acids), supplementation strategies, etc.
Reduce the level of methane production by up to 40% in animals fed roughage diets.
Impact
The CRP improved our knowledge and understanding of the ecology of rumen microorganisms, particularly methanogenic archaea and their interaction with predominant rumen microorganisms. Specifically,
• In vitro gas production test was standardized and used for screening antimethanogenic activity of plants containing secondary metabolites.
• Real-time PCR to enumerate rumen microbes in in vitro and in vivo systems, and DGGE for the study of rumen microbial diversity were optimized and implemented.
• Protozoal activity by (14C) Radio Isotope Technique was standardized and used for screening.
• In vivo methane production measurements in small and large ruminants using SF6, tunnel system and open circuit respiration calorimeter were validated and used.
• Increased capacity of NAS - over 30 students were trained to MSc and PhD levels and over 50 project staff, technicians and researchers trained in molecular biology techniques.
• Two (2) books titled "Methods in Gut Microbial Ecology for Ruminants" and "Measuring Methane Production from Ruminants" and over 50 peer-reviewed journal articles were published in peer-review journals. Description of approaches, methodologies and guidelines for methane measurement, methane reduction and enhancement of animal productivity are available to national authorities, farmer organizations and industry for use in implementing these tools on a larger scale.
These techniques which contribute to reducing the impact of ruminants on the environment, are currently being transferred to Member States through Technical Cooperation Projects.
Relevance
The CRP contributed to the project 2.1.2.3: Molecular technologies for improving productivity in smallholder livestock systems. Current approaches to the evaluation of digestibility and nutritive value of feed resources using conventional in vitro feed evaluation and animal studies have resulted in a large body of information about nutrient composition, digestion kinetics and digestibility. However, these techniques are unable to describe the microbial mechanisms involved in ruminal digestion, and are unlikely to result in the development of rational feeding strategies. Gene-based technologies have the potential to improve the nutritive value of ruminant feedstuffs that are fibrous, low in nitrogen and contain anti-nutritive factors.
Until recently our knowledge of rumen microbiology was primarily based on classical culture based techniques (isolation, enumeration and nutritional characterization) which probably only account for 10 to 20% of the rumen microbial population. Conventional culture-based methods of enumerating rumen bacteria are being rapidly replaced by the development of nucleic acid based techniques which can be used to characterise complex microbial communities. The 16S rRNA sequences in DNA extracted from a mixed digesta sample can be amplified by PCR using primers and the diversity and identity of the amplified 16S rDNA can be further analysed by several molecular techniques including: 1) restriction enzyme analysis of amplified polymorphic DNA (RFLP); 2) 16S rDNA based cloning, sequencing and probing; and 3) denaturing gradient gel electrophoresis (DGGE), temperature gradient gel electrophoresis (TGGE), and single strand conformation polymorphism (SSCP). Therefore RT-PCR and oligonucleotide probes targeting the respective 16S rRNA of the methanogenic archaea, and the major fibrolytic bacteria (Fibrobacter succinogenes, Ruminococcus albus and R. flavefaciens) in the rumen would be a robust approach to quantifying the effect of reduced methanogenesis on important functional microbial groups. The molecular based ecology techniques are also likely to provide better insight into the interactions between methanogens and the other rumen microorganisms. All this information should assist in the development of strategies for improving production by reducing methanogenesis. However, the challenge is how we utilize these technologies to improve ruminant production through a better understanding of microbial function and ecology.