An alternative philosophy for livestock breeding

Livestock Production Science, 8 (1981) 95--99 Elsevier Scientific Publishing Company, Amsterdam --Printed in The Netherlands

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AN ALTERNATIVE PHILOSOPHY FOR LIVESTOCK BREEDING

R.B. LAND A R C Animal Breeding Research Organisation, West Mains Road, Edinburgh EH9 3JQ (Gt. Britain) (Accepted 28 October 1980)

ABSTRACT Land, R.B., 1981. An alternative philosophy for livestock breeding. Livest. Prod. Sci., 8: 95--99. The merits of animal breeding are related to the rate of improvement which can be offered. Objectives however may alter particularly as a result of social change, so that improved local livestock may be left adapted to outdated conditions, thus emphasising the need for flexibility. Historically such flexibility and indeed much improvement has depended on the introduction of superior strains, previously selected by others, which happened to meet local requirements. The development of strains with divergent biological characteristics as a supplement to existing policies would increase genetic flexibility, could facilitate a faster genetic response and aid the rapid improvement of indigenous breeds. Such a policy would ensure the availability of appropriate genetic variation in the future and thus provide a positive complement to the passive conservation of "rare" breeds.

INTRODUCTION L e r n e r a n d D o n a l d (1966), in t h e i r b o o k " M o d e r n D e v e l o p m e n t s in A n i m a l B r e e d i n g " , c o n c l u d e d t h a t " A n i m a l genetics stands r e a d y to h e l p in reaching t h e objectives o f society. It is f o r s o c i e t y to decide w h e r e its a m b i t i o n s lie and w h a t are its p u r p o s e s " . C u r r e n t b r e e d i n g p r o g r a m m e s aim to m e e t the dem a n d s o f s o c i e t y b y defining the p e r f o r m a n c e o f o u r d o m e s t i c animals in e c o n o m i c t e r m s and a t t e m p t i n g to i m p r o v e this b y genetic selection. T h e success o f genetic i m p r o v e m e n t is t h e r e f o r e d e p e n d e n t u p o n rapid genetic change relative to t h e r a t e o f change in objectives. T h e r a t e o f social change m a y , h o w e v e r , increase in r e s p o n s e to political a n d e c o n o m i c pressures, whereas t h e r a t e o f genetic change is largely limited biologically and m a y even decline as genetic v a r i a t i o n is r e d u c e d . An adverse c h a n g e in the r a t i o o f t h e rates of genetic t o social change m i g h t r e d u c e i n v e s t m e n t in c o n v e n t i o n a l l i v e s t o c k breeding. In a d d i t i o n t o the p o s s i b i l i t y t h a t p o t e n t i a l welfare legislation m a y restrict the i m p r o v e m e n t o f t h e p e r f o r m a n c e o f c o m m e r c i a l livestock t h r o u g h changes in t h e i r nutri-

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96 tional or physical environment, there is consequently the risk that current genetic policies may be inappropriate. It is therefore opportune to consider ways of increasing genetic flexibility and the rate of short-term changes. This paper is offered as a discussion of these possibilities and of the extent to which events of the past offer lessons for the future. LESSONS FROM PAST AND CURRENT POLICIES During the first half of this century it became apparent that the Black and White Friesian cattle of Holland were particularly appropriate for milk production in the temperate regions of the world. They have spread through grading up indigenous breeds by crossing and by direct substitution so that generations of selection to improve Dairy Shorthorns in Britain or Normande cattle in France, for example, may be superseded. More recently it has become evident that dairy cattle geneticists in North America, and the United States in particular, have been the most successful at further improving these cattle, so that American Holsteins are now rapidly spreading to other countries. The introduction of large breeds of cattle such as the Charolais from mainland Europe into Britain, and of the highly prolific Romanov breed of sheep into France, further illustrate the failure of local breeders to predict and provide for future demands, or the inadequacy of local breeds to meet these demands. For the receiving countries which in general had contributed nothing to the development of these breeds or strains, their availability was entirely fortuitous. The occurrence of these events, however, illustrates the place of divergent and extreme types in animal breeding and points the way to a policy where extreme types are generated deliberately. The slow genetic response to selection for lean carcasses following the earlier development of very fat pigs emphasises the potential benefit of such divergent strains, for on this occasion no superior alternative happened to be generally available at the time. Further problems can be foreseen, and two examples from the sheep industry illustrate the instability of selection objectives. Within Europe lamb prices have varied markedly so that some countries have established intensive housed production units and chosen selection criteria to meet these requirements. If the relative price of lamb were to fall and intensive production were no longer viable, a different animal might be required. The regulation whereby live sheep weighing less than 50 kg cannot be exported from Australia to the Middle East was imposed to protect the jobs of slaughtermen in Australia, but as a result of the premium on animals which passed this threshold, the balance between the merits of selection to increase wool versus body growth was tipped in favour of body growth. Any change in the regulation would, however, be largely outside the influence of the Australian breeder. Those who selected to meet a different balance between meat and wool production might be in a better position t o m e e t future markets than those selecting for current demands.

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Political and economic factors are not the only forces beneath social change, and increased awareness of the values and disadvantages of animal products may become more important for selection objectives. Greater emphasis against animal fats is an example. The spread of Texel sheep and Charolais cattle with their propensity to produce lean carcasses illustrates the response to this change; they provide a ready alternative to existing strains. For dairy cattle, however, the range of alternatives is relatively small. Milk at least has the advantage that its composition may be changed artificially through the removal (or addition) of fat. There is no such option for eggs: cholesterol cannot be removed mechanically. Ethical attitudes are a further c o m p o n e n t of social opinion which may affect selection objectives. New animal welfare requirements in Europe seem likely to affect poultry husbandry in the short term, and possibly pig production soon after. The economic advantage of current strains of pig might be reduced if it were no longer possible to restrict their diet by limiting the amount of food available to housed stock. The social base for animal breeding is, therefore, unstable; economic and political events and changes in public attitudes can all lead to changes in the objectives of genetic selection. A N A L T E R N A T I V E P H I L O S O P H Y - - T H E D E V E L O P M E N T O F D I V E R G E N T BIOLOGICAL TYPES

The chance availability of superior strains has illustrated their usefulness. In addition, the sheep industry illustrates the value of strains which span the range of current commercial objectives. The availability of Southdown to Oxford or Hampshire Down meat rams, and fine-wool Saxony to coarse-wool Bungaree Merinos, facilitates rapid responses to changes in market requirements. There is no d o u b t that the introduction of an existing superior population, given its availability, is the most rapid form of genetic improvement. It is therefore possible to consider the planned development of an array of strains which cover current objectives and possible environments so that the future availability of alternative populations is ensured rather than left to chance. The planned development o f strains with the desirable expression o f biological components of economic merit would p u t the availability o f superior material on an organised, scientific basis. The main biological components of performance should first be identified, e.g., b o d y size, reproductive performance, efficiency of food conversion (including the use of roughage and concentrates in ruminants). Where the direction of change cannot be predicted, or where intermediate optima are likely, as with b o d y size or litter size, strains could be selected for levels of performance on either side of that currently desired. Where unidirectional change is envisaged, a single, biologically extreme strain could be developed. Where the performance of animals might be expected to interact with the physical, domestic or disease environment such a series could, for particularly important traits, be replicated in the various zones.

98 The strains formed in this way would then be combined, either among themselves or with indigenous breeds, to meet the demand of the time. Where appropriate strains were not available within an environment, the greater the biological deviation of those available from outside that environment, the smaller the proportion that would have to be introduced to effect a particular change and hence the less the risk of losing the existing advantages of adaptation to that environment. As social demands change, the proportion of the different strains would be modified to meet this change. Lines need not be limited to a single biological characteristic; for example, one line might be selected for efficiency at the top and at the b o t t o m end of the adult bodyweight distribution, or selected for growth rate without increasing adult weight. The policy would also provide an active complement to the passive conservation of rare breeds. Rather than merely preserving them for their unique characters, their unusual attributes could be exaggerated as a further source of variation. The extreme types would also be very valuable for the physiological and genetic study of variation. The lines themselves need not be particularly large, the factors governing their size being similar to those for control populations. Since it would be intended to use the selected population for crossing, the effect of inbreeding on the performance of the population itself would not be of over-riding importance; the possibility of accidentally losing favourable genes, and of ultimately running out of genetic variation, would be greater causes for concern. The divergent strains might not be economically efficient themselves. Indeed one can imagine that a high value for crossing may sometimes be associated with low performance. For example, uterine competition in sheep or cattle with an ovulation rate of 10 might lead to such high embryo mortality that very few matings were fertile, but such animals would have enormous breeding merit, for a very small proportion would be required to change the litter size of their crossbred offspring. POLICY FOR IMPLEMENTATION Improved strains are currently internationally available, subject only to quarantine restrictions. The development of extreme biological types lends itself to cooperative action and indeed to aid programmes. Some biological traits could be agreed, shared out, and the important ones duplicated; countries with particular interest in some traits could opt to develop them individually. The divergent strains would then be combined to meet the varied requirements of the collaborating countries. Such a scheme would be appropriate for sponsorship by government agencies, for it fills the gap between research and the development of strains to meet current commercial requirements by the animal breeding industry. It would be well within the scope of, for example, a European or, with their role in aid, an F.A.O. initiative.

99 REFERENCES Lerner, I.M. and Donald, H.P., 1966. Modern Developments in Animal Breeding. Academic Press, London. RESUME Land, R.B., 1981. Une autre philosophie de la s~lection. Livest. Prod. Sci., 8 : 9 5 - - 9 9 (en anglais). La valeur de la s~lection d~pend de la rapidit~ du progr~s qu'elle apporte. Cependant, ses objectifs peuvent se modifier par suite de changements sociaux, de sorte que le b~tail local am~lior~ se trouve adapt~ ~ des conditions d~pass~es, ce qui souligne le besoin de flexibilitY. Dans le passe, cette flexibilit(~, et certainement une part importante du progr~s, ont d~coul~ de l'introduction de souches am~lior(~es, ant~rieurement s~lectionn~es par d'autres, qui se sont trouv(~es aptes ~ satisfaire les besoins locaux. Le d4veloppement de souches de caract~ristiques biologiques divergentes en compl~ment des politiques existantes accro~'trait la flexibilit~ g~n~tique, pourrait faciliter une r~ponse g~n~tique plus rapide et contribuer fi l'am~lioration rapide des races locales. Une telle politique assurerait pour l'avenir la disponibilit~ d'une variation g~n~tique appropri~e et elles seraient ainsi un compl(~ment positif ~ la conservation passive des races "rares". KURZFASSUNG Land, R.B., 1981. Eine alternative Philosophie ffir die Tierzfichtung. Livest. Prod. Sci., 8 : 9 5 - - 9 9 (in Englisch). Die Auswirkungen der TierzSehtung sind verkniipft mit dem Grad der Verbesserung, der durch sie erreicht wird. Diese Ziele kSnnen jedoch, besonders als Ergebnis sozialer Ver~nderungen, wechseln. Dadurch kann vielerorts verbessertes Tiermaterial an veraltete Bedingungen angepasst sein. Der Bedarf an Flexibilit~/t wird dadurch hervorgehoben. Historisch gesehen war diese Art von Flexibilit~t und auch ein grosser Teil der Verbesserung abh~ngig yon der Einf[ihrung verbesserter Linien, die vorher yon anderen selektiert worden waren, um den 8rtlichen Bedfirfnissen zu entsprechen. Die Entwicklung von Linien mit unterschiedlichen biologischen Merkmalen als Erg~nzung zu bestehenden Zuchstrategien wUrde die genetische Flexibilit~t erhShen, kSnnte einen schnelleren genetischen Fortschritt bewerkstelligen und die rasche Verbesserung einheimischer Rassen unterstiltzen. Eine solche Strategie wilrde die Verf[igbarkeit einer angemessenen genetischen Varianz fur die Zukunft sicherstellen und dadurch fur eine positive Erg~nzung zu der passiven Erhaltung "seltener" Rassen sorgen.