Livestock production in developing countries has been challenged by the scarcity, fluctuating quantity and poor quality of feeds and forages, which are composed of fibrous tropical grasses and crop residues. Scientists and farmers have used various treatments and supplements to increase the digestibility of low-quality forages with variable results. Fibrolytic enzymes, such as cellulase and zylanase, were reported to increase fibre degradation in ruminant feeds and help to increase the availability of nutrients, especially energy and protein to animals. In response to requests from Member States, the Joint FAO/IAEA Animal Production and Health Sub-programme aimed to develop, validate and transfer tools and technologies to Member States for the optimal utilisation of locally available feed resources to enhance animal productivity while protecting the environment through the inclusion of exogenous enzymes as in the diet.
Enzyme treatments, despite individual variability, generally increased the nutrient availability from fibrous poor-quality forages and crop residues to animals. In this Coordinated Research Project (CRP), eight out of 10 research contracts reported increased digestibility of feeds. The improved feed utilisation was manifested by increased feed intake, fibre degradation, dry matter digestibility, as well as microbial protein synthesis and production of gas and volatile fatty acids in in vitro and in vivo studies. Seven contract holders reported increased body condition and productivity of animals, e.g. more and better-quality milk and meat.
In vitro laboratory studies were instrumental to screening 10 enzymes and finally identifying four (endoglucanase, exoglucanase, cellulase and xylanase) best-bet enzymes along with appropriate doses and incubation times. The main forages and crop residues were rice straw, maize stover and tropical grasses.
Two to four best-bet candidate enzymes at optimum dose ranges were identified for in vivo studies through feed digestibility using protocols and methodologies previously standardised for the treatment of feeds and forages with these enzymes.
Methane production varied regarding enzyme supplementation of feeds depending on the experimental methods (in vitro vs. in vivo) and feeds and forages used. There was a general trend of reduced methane emission when the total dry matter digestibility was considered. The CRP has resulted in the development of tools and methodologies for developing exogenous enzyme supplementation strategies to improve animal nutrition and productivity.
The use of nitrogen-15 stable isotope proved valuable to estimate increased gastrointestinal tract microbial protein synthesis. Similarly, carbon-13 was successfully used to identify methanogenic bacteria in the gastrointestinal tract as an important step in greenhouse gas mitigation from livestock farming.
Researchers from Argentina, Australia, Brazil, Canada, China, Mexico, Mongolia, Peru, South Africa, Spain, Sri Lanka, the USA and Zambia participated in this CRP.
The CRP resulted in 45 publications in peer reviewed journals and proceedings and 20 MSc/PhD students used the project’s results to complete their thesis work.
For more information, please see the CRP description:
http://www.dgdingfa.net/projects/crp/d31027
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