The major constraint to livestock production in Africa South of the Sahara is disease. In particular the parasitic diseases for which there are no vaccines limit seriously the output of livestock production. There are some 155 million cattle and over 250 million sheep and goats in the region and many are subject to these diseases.
Trypanosomiasis, transmitted by the tsetse fly has been recognised for many years as a major burden on livestock production. Equally, the ability of some breeds to withstand infection has been recognised and now Trypanotolerant stock are considered to be a major method by which sustainable animal production can be developed in the region.
However, improvement of those breeds exhibiting tolerance has been slow since the problem of identifying and measuring tolerance itself is extremely complex. This still remains a problem but, in recent years, there have been developments which might make it possible to develops breeding schemes for the improvement of Trypanotolerant cattle breeds and, eventually, sheep and goats.
It was considered appropriate to call the Expert Consultation since there are several new pieces of evidence both on the identification and measurement of tolerance and on genetic parameters related to such measures. At the same time, there is a growing awareness that the chemical control methods are constly, may have undesirable environmental consequences and are only sustainable by continued conetary inputs.
The improvement in efficiency of output of Trypanotolerant breeds offers the possibility of greater output per unit of input, an acceptable environement without likely deterioration and a long term sustainable system of production in harmony with social requirements.
The objective of this Expert Consultation was to identify both the areas of agreement on the genetic aspects, and the areas in which more evidence is needed before any major activity can occur. The Expert Consultation was asked to recommend both priorities for research and any developmental activities which it believes can start now, bearing in mind the long term nature of the genetic improvement process.
This report presents the summary conclusions and recommendations of the Expert Consultation together with the abstracts of the papers presented. The proceedins with complet texts of the papers is being published separately.
The Expert Consultation was opened by Dr. A.W. Qureshi, on behalf of the Director-General of FAO.
Dr. Qureshi reminded the participants that the first Expert Consultation on the subject was in 1976 and two of the participants present now were also present then.
The history of FAO's involvement with the subject of trypanotolerance was renewed starting from the work in 1974, subsequent collaborative work involving IBAR, ILCA, ILARD and UNEP and the initial foundation of ITC.
Dr. Qureshi reminded the Expert Consultation of the responsibility which it had for advising FAO. The momentum of activities had continued to develop and now FAO was looking to the Expert Consultation to guide it and the concerned Member Countries on important issues of research needs and of applied breeding schemes.
On Wednesday 4 September, Dr. H. de Haen, Assistant Director-General, Agriculture Department, addressed the Expert Consultation. He apologized that he was away on leave on the opening day but re-affirmed the welcome given to participants and expressed his gratitude to them for providing their assistance to FAO.
Dr. de Haen briefly reviewed the work of the previous day and the aspects covered. The constraints of present measures of tolerance, of genetic parameter estimates and the potential for identifying single genes associated with tolerance were mentioned. Dr. de Haen then raised several of the issues on which FAO was requiring the advice and guidance of the Expert Consultation. These included the relationship between trypanotolerance and other performance traits, the high priority and research needs the need for, and operation of, any breeding programme.
Dr. de Haen pointed out the need to be pragmatic since the world cannot wait for complete answers before starting activities, and expressed his anticipation of a valuable report to guide FAO in its activities.
In sub-Saharan Africa, the major constraint to livestock production in the sub-humid zones is disease; in particular, the parasitic diseases including tsetse-transmitted trypanosomiasis, tick-borne infections and endoparasites for which there are no vaccines and the current methods of control, namely, drugs and vector control do no more than limit the problem. An immediately available approach is the exploitation of genetic trypanotolerance. The Expert Consultation believes that the well managed use of such livestock may be the most realistic, economic, environmentally sound, sustainable approach for the control of parasitic diseases of cattle, sheep and goats until far into the 21st century.
The Expert Consultation welcomes the progress which has been achieved and reported since the 1st meeting in 1976, particularly in identifying potential methods of assessing tolerance. Currently the evidence on those methods is limited. There is also only limited evidence on the genetic parameters associated with tolerance and performance due to the large resources required to provide accurate estimates.
The Expert Consultation recognises the potential value of the additions, in the last few years, to the techniques available for biological investigation, e.g., immunological, molecular genetic and biometrical techniques. The Expert Consultation emphasises the need for further research and development work on the application of these techniques to the genetic aspects of trypanotolerant livestock - particularly in cattle, sheep and goats.
The Expert Consultation has identified the following specific areas as high priority in research work on the genetic aspects of trypanotolerance:
the accurate identification of the degree of tolerance;
the relationships between the degree of tolerance and performance traits including tolerance to other diseases;
a better understanding of the biological basis of tolerance;
species and, within species, breed characterization in terms of genetic distances and phylogenetic relationships. This is also important for the effective planning of genetic resource conservation;
selected breed comparisons for trypanotolerance and performance traits would provide valuable information for future use;
work aimed at mapping and identifying the gene(s) involved in trypanotolerance.
The Expert Consultation emphasises the need for full coordination of all institutions involved in research in the above mentioned areas to ensure the efficient investment of funds in these priority area.
The Expert Consultation notes that, to date, there has been no implementation of a successful breed improvement programme for trypanotolerant cattle. The constraints have been programme size, duration and lack of effective selection.
There are considerable areas where crossing takes place between tolerant cattle breeds and zebu. Such practice may well be of benefit in areas of low challenge or on the perimeters of the tsetse area but only in such areas.
The Expert Consultation recommends the establishment of a pilot within breed improvement scheme for cattle.
Such a scheme should be based on continuous screening of the population and operate as an Open Nucleus. The scheme must be subject to close and regular evaluation and should be designed to provide estimates of genetic parameters. It is essential that the scheme operates for several generations.
The objectives for the pilot scheme should include:
For the testing and evaluation of animals the management level of the nucleus should be that which is considered likely to be the local commercial environment of village farms in 10–12 years time.
The pilot scheme should involve at least 3 sites and 500 breeding cows. The scheme should ensure that all animals are properly evaluated for tolerance and that response to selection should be designed so that tolerance either is maintained or improved.
A study should be carried out to design the strategy for multiplication and dissemination of improved stock emanating from the pilot scheme.
The Pilot Scheme should be developed in collaboration with the relevant NARS.
The Experts Consultation welcomes the information that selection schemes are being undertaken.
The Expert Consultation recommends that similar pilot schemes to that proposed in 7 are developed for sheep and goats as the tools for evaluation of tolerance are developed for these species.
The Expert Consultation recommends a study of the strategies for use of mapped trypanotolerant genes.
The Expert Consultation recommends that training of scientists and technicians is given appropriate emphasis. The Expert Consultation emphasises the need for ensuring the transfer of the relevant technologies.