Joint FAO/IAEA Division's Coordinated Research Project

COORDINATED RESEARCH PROJECT: D3.10.21

Title: Development, standardization and validation of nuclear based technologies for estimating microbial protein supply in ruminant livestock for improving productivity

1. BACKGROUND

Recent advances in ration balancing include manipulation of feed to increase the quantity and quality of protein and energy delivered to the small intestine. Selection of feeds based on high efficiency of microbial protein synthesis in the rumen along with high dry matter digestibility, and development of feeding strategies based on high efficiency as well as high microbial protein synthesis in the rumen will lead to higher supply of protein post-ruminally. The strategy for improving production has therefore been to maximise the efficiency of utilisation of available feed resources in the rumen by providing optimum conditions for microbial growth and then by supplementing provide dietary nutrients to complement and balance the products of rumen digestion to the animal requirement.

Various methods are available for determining microbial protein production, which depend on the external markers such as ¹⁵N, ³²P and ³⁵S, and internal markers such as diamino pimelic acid (DAPA), L-alanine and ribonucleic acid (RNA). However, the need to use post-ruminally cannulated animals, and complicated and error-associated procedures to determine digesta flow are major limitations in these methods. The idea of using microbial purine compounds as a specific marker for the rumen microbial biomass was suggested by McDonald in 1954. Purines are heterocyclic rings with nitrogenous bases with varying functional groups. The purine bases, adenine and guanine are found in both DNA and RNA. Microorganisms have high concentrations of purine containing compounds (RNA and DNA) relative to concentrations in plant and mammalian cells. Furthermore, rumen microbes in general, rapidly degrade purines in diets. They are, therefore, likely to be present in only negligible amounts in digesta leaving the rumen therefore. The purines present in digesta entering the small intestine is, therefore, almost totally of microbial origin. These purine components are then metabolised in ruminants to form purine derivatives (PD) such as xanthine, hypoxanthine, uric acid and allantoin that are excreted, mainly in the urine. All four components are found in urine of sheep, goats, red dear and llamas, but only allantoin and uric acid are present in cattle and buffalo urine.

With estimates of daily urine volume and urinary concentrations of PD, the total daily urinary excretion of PD can be determined and used to predict the rates of absorption of purines from the small intestine using relationships developed for individual ruminant species. Since only urine is needed, an estimation of microbial protein supply can be incorporated into nitrogen balance and digestibility trials without much additional labour inputs. The advantages of this technique are its non-invasive nature and relative ease of use.

As a result of a Consultants meeting held in May 1995 to advise the Joint FAO/IAEA Division on the feasibility of using nuclear and related techniques for the development and validation of techniques for measuring microbial protein supply in ruminant animals, an FAO/IAEA Co-ordinated Research Project (CRP) on ‘Development, Standardization and Validation of Nuclear Based Technologies for Measuring Microbial Protein Supply in Ruminant Livestock for Improving Productivity’ was initiated in 1996, with a view to validating and adapting this technology for use in developing countries.

2. OBJECTIVES OF THE CRP

• To refine and standardise the PD excretion technique for measuring microbial protein supply in ruminant livestock,

• To validate the PD excretion technique for indigenous cattle (Bos indicus) and their crosses with exotic breeds, buffaloes, sheep, goats and camel in developing countries,

• To use the PD excretion technique as a robust and inexpensive method for estimating rumen microbial protein supply for developing feeding strategies and as a diagnostic tool for assessing nutritional status of animals in the field and for grazing animals where the quantitative collection of urine output is much more difficult.

The programme was carried out in two phases. During Phase 1 which lasted for 3 years, the technologies developed based on research by the Rowett Research Institute, UK, and other European laboratories, were refined, standardised and validated for indigenous Zebu (Bos indicus) cattle and their crosses with exotic breeds (Bos taurus x Bos indicus) and buffaloes. During Phase 2, the validated technique were extended for modelling PD in camel, and a spot urine sample approach was validated for different breeds of cattle, buffalo, sheep and camel for use at field level to estimate the supply of rumen microbial protein to the intestine. This spot urine sample approach dispenses with the quantitative recovery of urine.

The first Phase 1 was concluded with a Research Coordination Meeting (RCM) held in Vienna from 24-28 August 1998. The results from the first phase have already been published as an IAEA TECDOC 1093. A Laboratory Manual on the PD methodologies (IAEA TECDOC 945) has also been produced under this project. This manual has been found to be highly valuable to all participants of the CRP and other researchers using the PD excretion technique for estimating rumen microbial protein supply.

The second and final phase of this CRP concluded in May 2002 with the final RCM, which was held in Vietnam. In March 2000, a mid-term review and planning meeting was held in Malaysia.

A total of 15 groups participated in the project.

The summary of reports from some of the Research Coordination Meetings (RCM) are available as PDF files:

	TECDOC 945 (PDF format 2.41 MB)
	TECDOC 1093 (PDF format 8.70 MB)
	The 3rd RCM held in Malaysia (PDF format, 13 k)
	The final RCM held in Vietnam (PDF format, 42 k) and the photo of participants of this meeting.