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Review of the discussions


Review of the discussions
Surveys and measurements
Plant-animal interaction
Changes in pastureland conditions
Nutritive value and estimation of carrying capacity


With regard to the great number of communications, these have been presented under the different topics that resulted from the discussions.

Review of the discussions

The discussions can be regrouped into four major topics:

1. Surveys and measurements of vegetation;
2. Plant-animal interaction;
3. Changes in the conditions of pasturelands;
4. Nutritive value and estimation of the burden capacity.

Surveys and measurements

REVIEW OF THE DISCUSSIONS

H. HEADY:

It is necessary to make the distinction between vegetation density and vegetal cover. In the United States, the density is the number of plants per surface unit and the cover is the vertical projection on the soil of the vegetal surface expressed in percentage of soil surface.

It would be desirable to discuss the following two points:

- standardization of measurements on vegetation,
- distinction of vegetation layers for which the techniques to be used are not necessarily identical.

A. BLAIR RAINS:

It is necessary to study in a critical way the different usable methods, to judge the advantages and limits, in order to be able to choose which is the most suitable for the project to be carried out.

A. DIALLO:

First of all, it would be necessary to have an evaluation of the methods used in the different African countries historically divided into the English-speaking and French-speaking, and to see if a way to combine them exists. This is important for the improvement of information which cannot be interpreted if the methods used are not known.

H. HEADY:

We could certainly do much better work in Africa if we had a good evaluation of the methods already used. This could be done by organizations like FAO, UNDP or ILCA.

Also, it would be necessary to insist that all the articles published clearly mention the methods used.

The standardization of measurements and of methodology would have as the principal interest being able to use the data that comes from the different countries or sources, whatever the computer or type of calculating program used, permitting the establishment of a worldwide program of continual surveillance. Most of us nutritionists are as interested in the consumption of the biomass as in the arrangement of the vegetation. We have already mentioned the cover and the density, and we ought to perhaps add frequency in the Montpellierian sense of the world, insofar as parameters to actually measure in the field. Elements like composition and arrangement would come second in describing the vegetation.

C. HEMMING:

The standardization of survey methods would be very useful to determine the principal types of vegetation covering vast areas, and semi-skilled personnel can suffice for this work. In spite of everything else, the results must be controlled by a very qualified person, to avoid certain errors in interpretation.

D. PRATT:

A certain degree of standardization would be useful in the evaluation of vast zones. The objectives will have to be well-defined, particularly at the time of preliminary evaluations with a view to development.

P. NDERITO:

The standardization of methodology is essential. In fact, after studying French-language and English-language publications in the last few years, one sees that similar results are obtained from methods 50 different that the editorial committee of our quarterly magazine "Journal of Animal Production and Health in Africa" doesn't know what report to take into consideration.

S. KANOUTE:

Actually if you want to do research, it is necessary to try to integrate, at the risk of failure, all the agricultural, forestry, ecological, and livestock breeding factors.

D. GATES:

It doesn't seem that you have to try to carry out the standardization of methods, because there is no uniformity of solutions.

H. LE HOUEROU:

It's impossible to settle on one single work method, because the objectives and the means are different for each study: still, it would be possible to reach an agreement on the minimum level of data to gather, that is, those related to the flora, to the vegetation, the geomorphology, the soil, the climate, and to human and animal activity.

It is evident that a critical review of the different evaluation methods of the pasturelands would be desirable, as Heady pointed out.

B. DESCOINGS:

In order to obtain comparable results between them, it would first of all be necessary to harmonize the survey systems. The method that I have proposed is complementary to the others and has the advantage of emphasizing an often- overlooked notion of knowing the " structural data ". These are objective and compatible whatever the country and the type of flora, and they demand little extra time and effort.

T. BREDERO:

The work undertaken and the methods used by B. Descoings are remarkable, but they make no reference to practical application. Every method ought to consider what is ingested by the livestock - its appetite - as well as what cannot be reached by the livestock, for example, the shrubs and trees.

Plant-animal interaction

REVIEW OF THE DISCUSSIONS

H. HEADY:

It would be useful for the discussions to be oriented in a more practical manner on the management methods which put particular emphasis on the food-animal resource interactions, with the goal of determining the objectives and the necessary parameters for the evaluations and mappings.

D. WILCOX:

In the zones of little rainfall in western Australia, one has tried to keep a maximum number of animals on the pasturelands. The recent dry spells have caused the loss of as much as 90 percent of certain species of shrubs which are important sources of nutrition. In order to leave these species to regenerate, it would be necessary to forbid use of these pasturelands after the dry spell. Governmental endowments are necessary to permit enforcing such a regulation.

N.G. TRAORE:

When rainfall is studied, it is necessary to consider not only the amount of water but also the rainfall frequency, which can influence the dynamics of the grasslands. In the measurement of different animal species eating different vegetal species, it would be necessary to consider the makeup of the herds (cattle, sheep, goats) in order to determine the best herd composition in terms of the soil. The question can be asked as well for the different animal categories in question. This information permits better land management, particularly in the Sahelian zone, where they are beginning to talk about stratification of livestock breeding.

H. BREMAN:

It's not possible to give fuller details of the influence of rainfall on productivity. The statistics obtained until now have been limited by the reduced number of rainfall stations. It would be necessary to estimate the rainfall based on information gathered by surrounding stations. Such an analysis will be important in the future. It can already begin in some limited areas.

C. DE WIT:

The rainfall distribution alone is uninterpretable data if it is not associated with plurality and physical properties of the soils and plants. I think that appropriate research on the normal inter-relationships between plant physiology, the natural constitution of the soils and the rains would permit us to make the next dry spell less severe.

H. HEADY:

The dry spells are natural phenomena. They recur. Therefore, the problem is to limit the effects, since they cannot be avoided.

M. INUWA:

A recent example of the movement of nomads is the descent of the cattle from the destroyed pasturelands of Mali and Niger to Nigeria. This has caused Nigerian cattle to go farther south into the wetter regions. This pressure has prevented pasturelands from building up again. What ought to be the official regulation? How much time will the pasturelands need to build up again, and in what way? What measures should be taken to avoid animal sickness in the regions of heavy rainfall?

A. BLAIR RAINS:

The problem identified in Nigeria is not unique to drought years. In the northern part of the country, during the wet season, men and their cattle stay in the area. During the dry season they move southward, sometimes for 400 kilometres. But they are replaced by cattle coming from zones farther north.

To conclude, these territories are occupied year round by two types of cattle. The latter use the remains of the harvest and the stubble. All the trees which can be consumed and which ought not to be are severely mutilated. That's where the problem is, and not in the quantity of rainfall.

L. AYUKO:

The problem is identical in Kenya.

T. BREDERO:

The problem brought up by the Nigerian delegate has already been resolved in the Sudanian tropical grassland of this country. it's a question of additional nitrogen brought by leguminous plants either from the Sudanian pasturelands or by harvest remains. This has an effect on the weight maintenance of the animals, with even a slight gain during the dry season. What's more, a practical solution has recently been published by Syria, which has problems of nomadism. Food banks have been created there and the products are sold by cooperatives. There is no reason why that cannot be applied to Nigeria, which also has abundant surpluses of harvest remains.

M. INUWA:

Many publications have appeared on this subject. But if the nomads in Nigeria move, it's because they don't have a choice. Unfortunately, the problem lies in the fact that when the Nigerian livestock raisers move southward the pasturelands in the north are occupied by livestock raisers from Nigeria, Chad or Mali. A regulation at the international level to limit the movements and the number of cattle on the pasturelands would be necessary because these need to regenerate themselves.

A. DIALLO:

The problems of nomads and utilization of pasturelands are well known. What must be done? Humanize the Sahelian zone and put at the disposal of the people what it takes to feed them, clothe them, and feed their cattle. Is it necessary to maintain the seasonal movement of livestock and herders, nomadism, or to control and localize the livestock herders? Do we have sufficient data to give to the states to establish improvement programs in these zones? To avoid the overburden, wouldn't it be necessary to maintain the Nigerian herds in Nigeria? How is this possible?

In Senegal we are determining that it is necessary to " destock " the young animals of the Sahelian zone and take them to zones where they will have good and sufficient food. It is necessary to study the problem of rebreeding the calves in this new zone. There are so many problems that it would be necessary for us to resolve in order to help the people who live in these regions.

R. DAS:

The Rajasthan region in India receives little or no rain at all. Nomadism exists there, and efforts have been made to minimize losses during periods of drought. Thus the migration courses have been traced, where the fodder for the journey has been furnished. The routes and destinations are chosen in a selective manner by each community

X.:

Would it be possible to discuss further the rejuvenation of the man-made desert? What methods have been used? Is it possible for this to be applied in the Sahel?

R. DAS:

We are trying to restore a tree-like vegetation in the semi-desert zones by demonstration zones which are reseeded in order to obtain a rapid vegetal cover following a dry period. The seeds are varieties selected for their resistance to the harshest of dry conditions. The cooperation with local communities is carried out through collective decisions. The demonstration zones are not used as pasturelands for a certain period, and when the growth period has ended a limited number of animals from the community are grazed there. This educational system is still going on. The results are not spectacular but satisfactory.

H. HEADY:

It would seem that you have a certain amount of control over the movement of the population. How did you arrive at this?

R. DAS:

We cut off certain very specific and well-defined zones during the rainy season. That reduces the pasturelands, and the work of regeneration is then undertaken in these zones.

H. LE HOUEROU:

Could Dr. Das specify with what average annual rainfall the reseeding of local grasses has been carried out in the Rajasthan desert? What is the variability of this reading? What are the probabilities of success? Rajasthan, Syria, Tunisia, and Algeria start from a common point, that of the localization of nomads and the creation of livestock breeding cooperatives on relatively large areas. That implies outside of the given regions the creation of new fodder resources such as irrigated fodder land, shrub and fodder-tree plantations, use of agricultural and salt pools by plants such as Atriplex. This strategy is not necessarily applicable to the Sahel or in the countries of tropical Africa, but could nevertheless be used in certain cases.

R. DAS:

The types sown locally in Rajasthan are the following: Cenchrus ciliaris, Cenchrus setigerus, Lasiurus sindicus, Panicum antidotale, Panicum turgidum, and Dichanthium annulatum..

These types were planted in zones where the precipitation was less than 100 millimetres, and even in moving sand dunes, to try to stabilize them. These plants were sown as well in areas of varying rainfall, between 150 and 350 millimetres. The production differences in these zones are extremely clear. In the areas of little rainfall, one year out of five was rainy. The research carried out involved knowing how and when to seed these different types.

L. AYUKO:

We ought to try now to answer the following two questions: How to let the pasturelands rest? How to "destock" and maintain an acceptable carrying capacity?

A. MAIGA:

If Das' experiments are repeatable in setting, that would be a great help to Mali.

What actions have been undertaken in the United States, which has states with conditions similar to ours? Have they arrived at a general policy of destocking the young cows and steers in a period of dryness and of conservation of animals during the rainy season through imposed governmental action or by single popular consent?

D. GATES:

No general answer exists to Mr. Maiga's question. In fact, each region has its own characteristics.

P. NDERITO:

Although it is useful to be familiar with the measures taken to combat dryness in the United States and Australia, great differences exist between these countries and Africa. In Africa the population is not altogether conscious of the critical conditions in which it finds itself and of the solutions that are imperative. Therefore, there is a sociological as well as a technical problem.

H. HODGSON:

A drought brings with it a deterioration of the pasturelands without a reduction in the burden on them, or putting appropriate techniques into action. The American livestock breeder doesn't have the possibility of moving the animals from one pasture to another. Either he sells them or he loses them. To acquire a long term solution in Africa it would be necessary to study the potential in animals of each country; and on the international level, to limit the number of head by an increase in direct purchases, and to organize the slaughtering and the distribution of these products in consumer centers.

L. AYUKO:

The simple and easy solution to apply, which consists of reducing the number of animals, runs into problems with the livestock breeder, who refuses to reduce the size of his herd because it represents his entire wealth.

A. DIALED:

It's useless to try to make all the technicians here agree on the remedies for nomadism and moving of herds. In fact, the solutions are particular to each region. Our seminar would be more useful if it permitted setting up an evaluation of recommended solutions in different centres where nomadism and moving of herds have appeared. This evaluation could consider proposed solutions, the size of the regions involved, the numerical importance of populations, the techniques of vitality and education To mobilize the participation of the livestock breeders, and also the degree of integration of the different factors which naturally influence these movements. It would be necessary to make the population participate in whatever the proposed solutions might be, in the language of the country. This last point seems to be fundamental, though we have never talked about it.

C. HEMMING:

It is very necessary to reduce the stocking rate in the zones of extreme drought, on which only the nomads can survive. As long as governments do not induce the reduction of livestock, the only foreseeable solution is to reduce the number of nomads. That would be possible by creating cooperatives in the less dry areas where the displaced nomads could settle. This solution will always have to be politically and practically acceptable.

M. INUWA:

How to reduce the number of nomads? Some nomads exist only because there is livestock. If the number of head is reduced, the nomads are eliminated and a new type of farmer is created.

SORA ADI:

The nomads are the best users of desert lands, and the will of Ethiopia is to help them produce a greater number of head and not to reduce the number. One solution would be for a country of great livestock breeding potential to diversify its methods of production, while countries with a lesser number of animals adopt other methods of development.

L. AYUKO:

Kenya helps the nomads settle to their liking on their own pasturelands and not by official force. The goal is that once settled, they will establish themselves and that their children will prefer to look for work in the city. That's one possibility for reducing the number of nomads. Yet it is very important to settle them on their own land.

S. RISOPOULOS:

The FAO and the UNDP were shocked by the problem of deterioration of tracts of land in Africa and in the Middle East. They decided to work up a cooperative program to promote a project established on worth-while ecological bases, to manage tracts of land and to promote and step up investment in these areas.

T. BREDERO:

One additional possibility for the utilization of soils is found on the lands called " fadamas ", in Nigeria. These lands, which are natural pastureland zones, and where the water level is high, are usable during the dry season. These vast areas have a production potential for important green fodder with a relatively high protein level, and it is necessary to make the best use of them.

H. HEADY:

We have too much tendency toward a short-term view. As soon as it rains, it is necessary to foresee the next drought and act accordingly.

H. BREMAN:

It must not be forgotten that pasturelands are used not only by livestock but also by wild animals. It is necessary to protect the natural setting by a prohibitive measure, for example, which would permit utilization by wild animals, which are generally better suited to achieving better productivity from the natural surroundings. What's more, their influence on the vegetation can be less serious than that of livestock.

Why use wild animals? A lot of effort and many investments exist to stimulate livestock breeding, while almost no investment exists to seriously protect wild animals whose yields in meat are already competitive. The difference indicates that this natural resource must not be forgotten.

A. BLAIR RAINS:

These remarks are very true; yet one must consider the management problems posed for hunting preserves.

Would Dr. Ayuko answer this question, considering his experience in Kenya?

L. AYUKO:

It's correct to say that livestock breeding excludes the wild fauna of the pastureland zones. The conservationists must determine the importance of livestock breeding and compare the results with the value of the wild fauna in terms of monetary returns from industry, tourism and other factors.

H. HEADY:

ILCA must try to bring together work carried out on the wild fauna.

A.L. N'DIAYE:

Professor R. Germain, unfortunately absent, is not in favor of the creation of ranches for fattening wild animals. Sufficient investments have been made for the improvement of tracts of land. It is time to reap the benefits, instead of setting off in other directions.

Changes in pastureland conditions

REVIEW OF THE DISCUSSIONS

T. BREDERO:

It is interesting to note in Dr. Valenza's report that on the overgrazed zones near wells and well drillings, a very sizeable increase in organic matter and primarily nitrogenized matter was observed in the soil and in fodder-plants. That could have interesting practical applications.

A. MAIGA:

Absolutely no observation concerning the grade of the soils of different layers in nitrogenized matter has been done. The observed amount of nitrogenized matter in the plants near watering points could occur in connection with the grade of the first layers of organic matter.

This is a simple supposition. On the other hand, some observations done on the grade of total nitrogenized matter of the samples gathered in the immediate area of the well drillings show that this grade is inferior to what is found three or four kilometres from there.

A. DIALLO:

We are used to saying that around well drillings there is a deterioration in the vegetation. Yet, the experiments done by Valenza show that there can be a disappearance at the level of the woody strata, while at the level of the grasslike strata there would rather be a modification of the flora. The difference in nitrogenized matter must be due to the difference between the species located near the well drillings and those appearing several kilometres from them. These modifications depend especially on the nature of the soil. In certain regions, an increase in the overall production at the grasslike strata has been verified. It is possible to see at the level of well drillings in sandy regions a rather important development of species like the Cenchrus biflorus and in other areas of harder or more clayish soil some species well-liked by livestock, like yard-grass. In certain regions outside of the well-drilling areas in zones more or less trampled by livestock, it is possible to observe the disappearance of very well-liked species such as the Zornia

H. BREMAN:

The Sahel ranch station at Niono, in Mali, can be ranked as a preserve, because there are not enough watering points. On this preserve a study of the action of drought on the zones not used and on the zones of intense usage has been carried out.

Beside the watering points the soil is bare, and much of the woody substance dies. The grasslike perennials have almost completely disappeared, and the carrying capacity has been reduced by 2/3 of the possible capacity before drought. At a distance of about 10 to 20 kilometres from watering points, where there is little use, the vegetation is quite different from that which surrounds the watering points.

N.G. TRAORE:

We can only affirm that such and such a soil specifically carries the Zornia, which in my opinion grows everywhere in the Sahel. Concerning the species that grow around wells and water drillings, we can also cite those named by our colleague from Senegal, Cenchrus ciliaris and Dactylotenium aegyptum

G. BOUDET:

Here are some precise details on the evolution of pasturelands subject to grazing. When the grazing takes place throughout the rainy season, the annual grass-like plants disappear in the space of one or two years. The Zornia, a short-cycle species which flourishes and bears in three weeks, multiplies in spite of the grazing in such a way that in the space of two or three years, there is no longer anything except Zornia. As this is a very small species, otherwise an excellent leguminous fodder-plant, it dies rapidly and the pastureland becomes bare. This is the case in Ferlo, where an excess of rain causes an increase in the Zornia. On the other hand, in the case of the permanent watering point at Niono, where there is an excess throughout the whole year, the soil is stripped. Several kilometres away, we find the Zornia again, and farther on still, natural vegetation.

X.:

Why do certain grass-like species evolve and certain woody species disappear next to watering points? Why does overgrazing bring a multiplication in the desired species? The explanation could be the amount of defecation, but it is possible that there are other explanations.

A. CISSE:

Has a detailed evaluation of plants indicatory of overgrazing been done? Hasn't the appearance of new species following the drought of the last few years been verified? If yes, what can be their nutritive value?

X.:

The food value of the new floral composition around the watering points and its availability in the course of the year are points to be considered.

If it's a question of leguminous plants, certain species will be liked by the livestock. But when dry, the leaves fall and the desirability decreases. The fodder is very often used during the period when the livestock consumes dry grass. The protein value of the leguminous plants, which increased at the outset, became weak during the period of use.

M. INUWA:

The watering points are directly linked to the pastureland zones and are all usable, contrary to the idea expressed by Dr. Ayuko; in Nigeria, 200 have been constructed in the desert zones where the grass is not very good, and after four to five years there is nothing left on the land. Yet the livestock need water. Therefore, it is necessary to select resistant species for the areas around watering points.

H. HEADY:

It is in terms of the objectives and the level of deterioration of pasturelands that the latter need to be cut off for one or two seasons. This prohibitive measure can be brought about simply by closing off a watering point and centralizing the supply.

A. BLAIR RAINS:

During the growing season of the grass, surface water is available as well. Therefore it is desirable to close off the watering points during this period to permit the pasturelands to regenerate.

R. PERRY:

For the last ten years in Australia, the management of pasturelands has supported much more the concepts of fodder-plant resources and livestock breeding.

In particular, the research has emphasized the present state of pasturelands and their evolution. From another point of view, a method based on the changes in floral composition beginning with the indicatory species permits determining the state of conservation of the soils.

H. HEADY:

It is necessary to emphasize that in this method the sites are defined and mapped before one begins studying the actual condition and evolution.

R. PERRY:

In the use of such a method, it is important to avoid scientific measures which are too complex. It is preferable to choose more easily understandable techniques for the farmers working directly on their pasturelands.

C. HEMMING:

It is necessary to draw conclusions from past errors. Nigeria is not the only country to have too many water drillings, which brings about overgrazing. The intentions that led to their existence were commendable, but the results are disastrous. Many land ecologists recommend the closing of these wells, but in certain zones that would be a politically unacceptable solution because persons other than the livestock breeders have chosen to settle near watering points. For the future, the different ministries will have to control the settling of the non-breeders around the wells, because the latter are dependent on them and would suffer from their closing.

A. MAIGA:

Where are we going? First of all, it was proposed to localize the nomads, then to reduce the number of animals, now to close the watering points. How can we suggest the closing of watering points without proposing some alternative solutions? If this solution is applied to the countries that have many watering points, it can be very good. But what to do for the countries that don't have any?

H. HEADY:

The suggestion was not to close the watering points, but to use them on a rotating basis. Surely, in the case of a number of limited wells, the question does not arise.

A. BLAIR RAINS:

The problem comes from the permanent watering points. It would be necessary to strive to increase the number of natural or artificial surface water reservoirs supplied by rains and thus provide limited quantities of water.

L. AYUKO:

The management of watering points can allow for the planning of pastureland zones for the nomads. The increase in small reservoirs would allow for grazing on larger areas. If you want to attempt to regenerate the pasturelands around the wells, it is necessary to close them during the rainy season when surface water is available.

Nutritive value and estimation of carrying capacity

REVIEW OF THE DISCUSSIONS

A. DIAOURE:

Whatever the measure of energy value used, the starting point is knowing the digestibility of fodder plants. Yet very little work has been devoted to this thankless task of determining digestibility. It is therefore necessary to do this work while trying to avoid the imperfections found in European tables: digestible nitrogenous materials (MAD) talked about exclusively for cattle, while total nitrogenous materials (MAT) are talked about for animals having one digestive process. While the digestive physiology of ruminant animals is familiar, the notion of digestible nitrogen has little significance, since the animal ruminates everything it ingests and transforms it. Therefore, it would be more correct to express nitrogen in total nitrogenous material for research in normal rationing for tropical cattle.

A. BLAIR RAINS:

Numerous studies have been done on digestibility of a great number of plant varieties in Africa and Australia. On the notion of nitrogen, it would be more desirable to work on the digestible matter, because the proteins are enclosed in lignin and cellulose and sometimes they are not assimilated. Therefore, the results are incorrect if you are talking about total nitrogenous material.

F. TRAORE:

Three questions concerning Dr. Rivière's article:

1) If you can measure the desirability of species and the amount of digestibility in the field, why isn't it possible to measure the level of ingestion? In fact, the standard 2.5 kilograms of dry material per 100 kilograms of live weight is questioned more and more.

2) For the agrostologists, the field work to determine the coefficients of digestibility and the level of ingestion could be done rather simply by previous deduction, but aren't the problems at the level of the sampling of feces and their processing in the laboratories?

3) Could someone talk specifically about the estimation method of the Harris group?

R. RIVIERE:

The indirect methods of estimation use two types of indicators: internal, the lignin; and external, chromium oxide. Beginning with these analyses of the food consumed and fecal material gathered, it is possible to deduce the elements researched. But the quality and the components of the ingested fodder plant can only be evaluated by observation of cattle in the pastureland. In this case, the results remain subjective.

M. DICKO TOURE:

All the researchers of the tropical countries are conscious of developing appropriate digestibility tables. Couldn't an international body like ILCA assemble the necessary information for their establishment in the tropical countries?

J. PAGOT:

The International Network on Feed Information and Composition on food composition has entrusted I.L.C.A. with the robe of studying the composition of food products and their digestibility. All the related laboratories will be associated with I.L.C.A. research

M. GWYNNE:

The quantity of common cellulose has a considerable effect on the food intake of the herbivores. This amount varies with age and from the apex to the base of the plant. A growth stage exists, the length of which varies according to the plants, during which they are desirable. This may explain why certain plants judged not desirable are found ingested when the indicators are used. These indicators are used to judge the amount of passage.

N. MCLEOD:

There is a significant decrease in the ingestion of dry materials during the dry season. A part of the fodder-plant areas should be reserved for feeding during the dry season. However, it can be proved that the animals feed principally on shrubs and overhead plants during this season. To base a pastureland program for the Sahel solely on grass is an error.

T. BREDERO:

The evaluation of pastureland must take into consideration the possibilities of supplementation brought in during the dry season, using protein or nitrogenous components. The shrubs and overhead plants contain protein and nitrogenous components and constitute a potentially valuable supplementation in spite of their low level of digestibility. Without supplementation, the fodder-plant is not usable during the dry season.

A. SOW:

To be familiar with the food value of pasturelands in kilograms of dry material is useless if there are no watering points for the livestock in the area.

N.G. TRAORE:

For us, the essential thing is knowing the number of animals that a given area can handle. It certainly depends on the food value of the tract of land. How have the countries of the Sahelian region done in determining this?

H. HEADY:

The stocking rate and carrying capacity should not be confused. The stocking rate is the number of animals present at a given time on one unit of surface area. The carrying capacity can be considered as an average carrying over a rather long period of time.

R. PERRY:

In central Australia the following process for calculating the stocking rate is used. A region that receives 250 millimetres of water is used as a rate of reference. This rate of reference is then adjusted in terms of different factors balanced according to their importance: the type of land, the type of vegetation, the slope, the precipitation, the amount of aerial pastureland. Two considerations in density rate for each type of land are calculated as well: one during the periods of drought, the other during a good year. The first runs about a quarter of the second.

H. HEADY:

The stocking rate observed in the field is the best information to estimate the carrying capacity. It's the answer of the vegetation to the stocking rate in the course of the year that furnishes the necessary response.

R. PERRY:

Contrary to what one usually thinks, there have been few studies on pasturelands in Australia. The system described only has the results formulated from experiments already carried out.

H. LE HOUEROU:

The desirable animal density on the pasturelands has been defined in North Africa, on the one hand by the experience of the livestock breeders and on the other hand by experimentation on different vegetal groupings with different capacities. Thanks to mapping and to these experiments, a carrying capacity has been simulated for each type of vegetation.

S. RISOPOULOS:

In the industrialized countries, because of private Ownership of lands, relatively precise figures exist over several decades concerning carrying capacity. In Africa these elementary figures, namely on meat production per surface unit, are practically nonexistent. The research for a definition of carrying capacity in Africa ought to be made a matter of high priority.

N.G. TRAORE:

The reasons called for by Mr. Risopoulos seem justified. However, it is necessary to recognize that certain research has already been carried out in Africa. Wouldn't you have to gather the data in order to calculate a carrying capacity?

R. HODGSON:

The carrying capacity must be studied in the light of the profits that you wish to take from it. If the objective is only maintenance or the production of 50 to 100 kilograms of meat per animal, the carrying capacity is very different.

A. DIALLO:

The carrying capacity varies according to several factors concerning the needs of the animals. Some estimate that the needs of our animals are identical to those of European animals. Some experiments have been carried out to define the needs of our animals. When someone asks us the question about knowing whether a zone is or is not capable of feeding a definite number of animals, it would be necessary for us to be able to answer. Yet the standards put at our disposal don't permit us to find out.

H. HEADY:

In answer to Dr. Diallo, in the United States an effort was made on such evaluation from 1920 to 1930. This effort, which had as a goal determining the carrying capacity, was terminated before the end of the work. Parallel to these studies, about 50 experiments on pasturelands with different degrees of usage and burden were done. Actually, what to do with the information obtained is not known. The best method is to go into the field, observe the state and evolution of the pasturelands, and act in accordance.

A. DIALLO:

What are the ways proposed by Dr. Heady to answer the question of determining how many animals can be put on one pasture?

H. HEADY:

Aerial or ground evaluations permit determining in what state the pastureland is found and in what way it is evolving. If it is in poor condition, it is not only necessary to act on the number of head but also perhaps to create a program rotation of the pasturelands or of reseeding; therefore, it is necessary to strive to determine what the land needs, rather than trying to determine theoretical numbers of head.

M. INUWA:

The important thing is to define the necessary methods and means to surmount our problems. Actually, nomadism is accepted. How to arrive at the notion of carrying capacity and how to evaluate it, considering these facts?

H. HEADY:

It's not necessary to calculate the carrying capacity; managing the pasturelands suffices.

B. NORTON:

The concept of carrying capacity is losing more and more of its significance because it doesn't take into account the rainfall variations over the years.

H. HEADY:

It is preferable to preserve the pasturelands rather than to use them to The ultimate. Concerning carrying capacity, it is necessary to stress the practical aspect. It is in direct correlation to the quantity of usable fodder, which itself depends on the environment and in particular on the rains. These are uncontrollable factors. The controllable factors and the farmers' use or non-use of manure and choice of seeds are equally important, and affect the carrying capacity.

R. PERRY:

The calculation of the carrying capacity is dangerous because it is often considered as an unchangeable statistic, whereas it's only a question of a fluctuating estimation. To determine the carrying capacity, it is necessary to follow the evolution of the pasturelands and to increase or decrease the burden in livestock according to the good or poor state of the pasturelands. In accordance with Dr. Blair Rains, it is not possible to determine the carrying capacity from fodder samples and their nutritive value. On the other hand, if you study the evolution of the pasturelands, you can then determine the carrying capacity.

R. RIVIERE:

It would be necessary to define what is meant by carrying capacity. Is it simply the area necessary to support the animals to allow them to survive, or is it the area necessary for the animals to keep the same weight?

In this last case, it can be said that in the dry season, no Sahelian pasture is capable of supporting a single animal.

G. BOUDET:

Considering the evolution and the deterioration of numerous Sahelian pasturelands, the potential of the pastureland, namely its grass-like cover, could be kept as a priority. The West African professionals and the researchers have preoccupations that are diametrically opposed. On the other hand, until now no estimate of the burden of the pasturelands and of their exploitation in West Africa has been undertaken.

H. BREMAN:

Did Mr. Boudet take into account some observations done by myself in Mali to estimate the carrying capacity? These observations were established on the relationships productivity/rainfall/capacity. This was a first attempt, the importance of which was able to show itself during the latest dry spells, and the results of which were able to be expanded to other zones.

R. BAKER:

The carrying capacity is essentially variable and depends almost entirely on the management method of the pasturelands. It is necessary to be aware of this when a management method is chosen.

D. PRATT:

The estimate of the carrying capacity of a pasture is a necessary statistical fact for the submission of a financial request for a development project, even if this estimate indicates a decrease rather than an increase in the grazing intensity. This fact is useful in the management process. It must be adjusted according to seasonal changes and conditions of the pastureland. It is not easy to change the existing rates in most of the areas of pastoral Africa as it is possible to do in the United States or Australia. Knowledge of the carrying capacity is definitely indispensable for new lands opened to grazing, particularly in zones formerly affected by the tsetse fly.

L. AYUKO:

In answer to Mr. Pratt's first point, I don't remember having come across a justification for a project request being based on a decrease in carrying capacity. The usual justifications consider the different characteristics of the carrying capacity, namely the production of meat, the localization of managed pasturelands, and the social advantages that result from them. These factors are probably more important than the nutritive value in the evaluation of the projects submitted for subsidy.

H. HEADY:

In the justification of requests for obtaining loans or donations, two elements are looked at:

1) the actual production capacity of the land,

2) the production capacity after application of new management methods.

It is possible that some of these elements proceed from a decrease in the carrying capacity and not the opposite. The estimate of the carrying capacity of a pasture does not only take into account the considerations of climate and soil, but also the management policy. In the United States, government lands are leased on the basis of the carrying capacities and these are kept as flexible as possible.

T. BREDERO:

Concerning the lenders, and particularly the World Bank, two objectives have priority: the meat production at a certain investment level and, secondly, the social benefit.

M. INUWA:

Contrary to what a preceding speaker indicated, the international bodies do consider the carrying capacity in their awarding of aid. The carrying capacity, the production rates, and the profits gained are very important for those who lend or donate money.

L. AYUKO:

To avoid any misunderstanding, it is correct to specify that the carrying capacity has never been considered as a very important factor. The discussion should stick to defining the relative importance of the carrying capacity and the nutritive value of the pasturelands.


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