Control and Manipulation of Animal Growth. Proceedings of Previous Easter Schools in Agricultural Science

342 Pages·1986·7.14 MB·English

by  P.J. Buttery, D.B. Lindsay and N.B. Haynes (Auth.)

Proceedings of Previous Easter Schools in Agricultural Science, published by Butterworths, London
♦SOIL ZOOLOGY Edited by D. K. McL. Kevan (1955)
*THE GROWTH OF LEAVES Edited by F. L. Milthorpe (1956)
♦CONTROL OF THE PLANT ENVIRONMENT Edited by J. P. Hudson (1957)
♦NUTRITION OF THE LEGUMES Edited by E. G. Hallsworth (1958)
*THE MEASUREMENT OF GRASSLAND PRODUCTIVITY Edited by J. D. Ivins (1959)
♦DIGESTIVE PHYSIOLOGY AND NUTRITION OF THE RUMINANT Edited by D. Lewis
(1960)
♦NUTRITION OF PIGS AND POULTRY Edited by J. T. Morgan and D. Lewis (1961)
♦ANTIBIOTICS IN AGRICULTURE Edited by M. Woodbine (1962)
♦THE GROWTH OF THE POTATO Edited by J. D. Ivins and F. L. Milthorpe (1963)
♦EXPERIMENTAL PEDOLOGY Edited by E. G. Hallsworth and D. V. Crawford (1964)
♦THE GROWTH OF CEREALS AND GRASSES Edited by F. L. Milthorpe and J. D. Ivins (1965)
♦REPRODUCTION IN THE FEMALE MAMMAL Edited by G. E. Lamming and E. C. Amoroso
(1967)
♦GROWTH AND DEVELOPMENT OF MAMMALS Edited by G. A. Lodge and G. E. Lamming
(1968)
♦ROOT GROWTH Edited by W. J. Whittington (1968)
♦PROTEINS AS HUMAN FOOD Edited by R. A. Lawrie (1970)
♦LACTATION Edited by I. R. Falconer (1971)
♦PIG PRODUCTION Edited by D. J. A. Cole (1972)
♦SEED ECOLOGY Edited by W. Heydecker (1973)
HEAT LOSS FROM ANIMALS AND MAN: ASSESSMENT AND CONTROL Edited by J. L.
Monteith and L. E. Mount (1974)
♦MEAT Edited by D. J. A. Cole and R. A. Lawrie (1975)
♦PRINCIPLES OF CATTLE PRODUCTION Edited by Henry Swan and W. H. Broster (1976)
♦LIGHT AND PLANT DEVELOPMENT Edited by H. Smith (1976)
PLANT PROTEINS Edited by G. Norton (1977)
ANTIBIOTICS AND ANTIBIOSIS IN AGRICULTURE Edited by M. Woodbine (1977)
CONTROL OF OVULATION Edited by D. B. Crighton, N. B. Haynes, G. R. Foxcroft and G. E.
Lamming (1978)
POLYSACCHARIDES IN FOOD Edited by J. M. V. Blanshard and J. R. Mitchell (1979)
SEED PRODUCTION Edited by P. D. Hebblethwaite (1980)
PROTEIN DEPOSITION IN ANIMALS Edited by P. J. Buttery and D. B. Lindsay (1981)
PHYSIOLOGICAL PROCESSES LIMITING PLANT PRODUCTIVITY Edited by C. Johnson
(1981)
ENVIRONMENTAL ASPECTS OF HOUSING FOR ANIMAL PRODUCTION Edited by J. A.
Clark (1981)
EFFECTS OF GASEOUS AIR POLLUTION IN AGRICULTURE AND HORTICULTURE
Edited by M. H. Unsworth and D. P. Ormrod (1982)
CHEMICAL MANIPULATION OF CROP GROWTH AND DEVELOPMENT Edited by J. S.
McLaren (1982)
CONTROL OF PIG REPRODUCTION Edited by D. J. A. Cole and G. R. Foxcroft (1982)
SHEEP PRODUCTION Edited by W. Haresign (1983)
UPGRADING WASTE FOR FEEDS AND FOOD Edited by D. A. Ledward, A. J. Taylor and R.
A. Lawrie (1983)
FATS IN ANIMAL NUTRITION Edited by J. Wiseman (1984)
IMMUNOLOGICAL ASPECTS OF REPRODUCTION IN MAMMALS Edited by D.B. Crighton
(1984)
ETHYLENE AND PLANT DEVELOPMENT Edited by J. A. Roberts and G. A. Tucker (1985)
THE PEA CROP Edited by P. D. Hebblethwaite, M. C. Heath and T. C. K. Dawkins (1985)
PLANT TISSUE CULTURE AND ITS AGRICULTURAL APPLICATIONS Edited by Lyndsey
A. Withers and P.G. Alderson (1986)
♦ The titles are now out of print but are available in microfiche editions
Control and Manipulation of
Animal Growth
P. J. BUTTERY, BSc, PhD, DSc
University of Nottingham Faculty of Agricultural Science
D.B. LINDSAY, MA, DPhil
AFRC Institute of Animal Physiology, Cambridge
N.B.HAYNES,BSc,PhD
University of Nottingham Faculty of Agricultural Science
BUTTERWORTHS
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First published 1986
© The several contributors named in the list of contents 1986
British Library Cataloguing in Publication Data
Control and manipulation of animal growth
1. Veterinary physiology 2. Growth
I. Buttery, P.J. II. Lindsay, D.B.
III.Haynes,N.B.
636.089'26 SF768
ISBN 0-407-00422-X
Library of Congress Cataloging in Publication Data
Main entry under title:
Control and manipulation of animal growth.
Bibliography: p.
Includes index.
1. Livestock—Growth—Congresses. 2. Hormones-
Congresses. 3. Growth regulators—Congresses.
I. Buttery, P.J. II. Lindsay, D.B. (Derek Barber)
III. Haynes, N. Bruce, 1926-
SF768.C66 1986 636.089'26 86-4158
ISBN O-407-00422-X
Photoset by Scribe Design, Gillingham, Kent
Printed and bound in Great Britain by
Robert Hartnoll (1985) Ltd, Bodmin, Cornwall
PREFACE
The last few years have seen an awesome proliferation of knowledge regarding the
physiological control of the growth process in animals. To take some specific
examples, the dual system which modulates growth hormone secretion via
hypothalamic releasing and inhibiting hormones has been unravelled; the way
growth hormone acts, through intermediate growth factors, and in synergy with
other hormones is rapidly being clarified at the cellular level. This knowledge,
coupled with advances in biotechnology which could give rise to potentially
unlimited and cheap quantities of growth hormone and growth factors normally
endogenous to the animal, leads to exciting new possibilities for practical
application in animal husbandry. It seemed to us an opportune time, therefore, to
gather a forum of speakers, experts in the field of the control and manipulation of
animal growth, to discourse around the theme 'hormones' and between them to
cover a broad spectrum varying from the highly theoretical, through the legislative,
to the highly practical. In retrospect, the idea was seen to have merit at least in that
it attracted some 200 delegates from 15 different countries who listened to 20
speakers, perused 22 poster demonstrations and took part in much lively debate
both inside and outside the conference hall. We hope that this report of the
Proceedings of the 43rd Easter School in Agricultural Science will serve to some
extent as a text book, that it will act as a valuable source of reference and, most of
all, that it will provoke thought and the whole will become greater than its parts as
new ideas arise from assimilation of the contents.
P.J. Buttery
N.B. Haynes
D.B. Lindsay
v
ACKNOWLEDGEMENTS
It gives us pleasure to acknowledge those who presented papers and posters, and
also the delegates, who contributed a great deal in the way of invigorating and
informed discussion. Much of the smooth running of the conference was due to the
astute chairmanship of G.E. Lamming, D. Lister, L. Muir, R.G. Rodway, J.M.
Bassett and D.B. Crighton and their contribution is appreciated. We also thank the
staff and postgraduate students from Sutton Bonington who helped in many ways in
the everyday organization of the meeting, and we are especially grateful to Mrs.
Shirley Bruce who acted as Conference Secretary.
The following organizations made generous donations to the School, and without
them the conference would not have been possible:
BOCM Silcock Ltd
Monsanto
Merck, Sharp & Dohme
Pfizer Central Research
Roussel-UCLAF
Unilever
vu
INTRODUCTORY COMMENTS
G.E. LAMMING
University of Nottingham Faculty of Agricultural Science, Sutton Bonington,
Loughborough, UK
Eighteen years ago we held a Nottingham Easter School in the general field of
animal growth and the papers and discussions were published in a volume entitled
The Growth and Development of Mammals. I don't think it could be described as a
classic text but it was a good teaching manual, widely used throughout the world,
and it reflected the mood of the period. The papers, showing the influence of the
Hammond School, were mainly descriptive, containing material of a basic
functional and anatomical nature. There were reviews on bone, muscle and fat
development in mammals including man and on the influence of genetics upon
growth and carcass composition, but there was little based upon quantitative
physiology with reference to hormones.
Although growth hormone had been discovered 35 years earlier, it was not
available in sufficient quantity for wide-scale experimental use; we knew little
about the mechanisms of growth hormone release, less about its mode of action,
and the full implications of negative feedback in endocrinology were yet to come to
light.
During the 18 years since that growth meeting we have held four Easter Schools
concerning reproduction where research problems and achievements in the area of
reproductive endocrinology have been extensively reviewed. In these Easter
Schools the pioneering and detailed work on hypothalamic control of pituitary
gonadotrophin secretion, the importance of patterns of such secretion in
influencing gonadal steroid release and the role of these steroids in negative
feedback control of pituitary hormone secretion has been much discussed and
amplified. This has been not only from a theoretical standpoint, but also from the
important practical aspect of artificially manipulating the hypothalamo-pituitary-
gonad axis to increase reproductive efficiency. As reflected by the gap between the
growth meeting 18 years ago and this one, that type of information, readily
accessible to reproductive physiologists, was not available in the growth field for
informal discussion and comment until recently; this by the very diffuse nature of
growth, making it a much more difficult area for quantitative study. But the growth
physiologists are rapidly catching up, to the extent that the major thrust of this
meeting will come from biochemists, molecular biologists, cell physiologists and
those interested in genetic engineering. Not only have the growth research
programmes developed over the interim period, but public attitude to studies on
growth have also changed significantly.
1
2 Introductory comments
Eighteen years ago populations in Western countries demanded great quantities
of cheap food. They were not particularly concerned about the methods of
production, or animal welfare, or about food composition or its effect on human
health. Now human, as well as animal health and welfare occupies the consumer's
mind to a much greater extent, and governs the actions of politicians and their
scientific advisors to the point where some Western nations are preferentially giving
financial support to new research in these areas. Chemical industries, quick to
realize the wide potential use of growth stimulants of one sort or another are
capitalizing by using new techniques in biotechnology to provide such products with
the aim of producing more efficiently, animal protein of acceptable quality, but
with adequate regard to safety in respect of animal health. Of course, there are still
vast areas of the world where food shortages and human and animal starvation,
particularly following periods of drought, occur and this has stimulated the
sympathy of affluent societies. It is an important, and opportune time, therefore,
for this Easter School to be held with the aim of drawing together the many
different facets of animal growth in quantitative physiological terms and
considering the exciting new possibilities for its manipulation.
I want to focus your attention, before the meeting proper begins, on three areas
of interest to which we might address ourselves. Firstly, whilst the format of the
meeting is not geared towards genetics this area should not be forgotten. It is only
just becoming possible to clearly identify the key steps in processes governing
growth which contribute to the natural variation in animal traits of commercial
importance. Until we identify these components fully, further progress in this
important area of physiological genetics is limited. The geneticist has already
contributed by creating appropriate laboratory stocks, particularly mice, to provide
the appropriate experimental models. For example strains of mice have been
developed which have lower fat content, higher protein content and an increased
appetite which could provide suitable experimental material for study. This
conference, it is hoped will, albeit indirectly, throw much light on how such animals
might be best used experimentally by the geneticist.
The second area concerns the necessity or otherwise for development of new
growth-promoting agents which may be used to enhance the rate of growth or at
least to prevent a depressed growth rate or food conversion efficiency in conditions
where intensive systems of husbandry may limit maximum growth. Currently there
is a vast array of chemotherapeutic growth-promoting agents which are available
both for the ruminant and non-ruminant species and for licensing purposes they are
broadly classified into three groups: the antibiotics, the antibacterials and the
antiparasitic drugs. The use of these compounds has not been entirely
problem-free. For instance, in some cases their long-term use, sometimes in
inappropriate circumstances, results in the development of resistant organisms
which then create problems of either a decreased response or overt disease. In
addition, there exists the potentially serious hazard of the development of resistant
strains of organism and the question of transferred resistance to organisms which
are pathogenic to man. These problems continue to occupy drug licensing
authorities. It is difficult to foresee that there will be major development of new
products of this type and indeed the philosophy of limiting the use of antibiotics as
feed additives to those agents not required for therapeutic purposes in man has
gained much ground.
Then there is the potential use of anabolic agents, particularly for ruminant
production. These have marked effects in improving animal performance, and
G.E. Lamming 3
again the current difficulty is not one of mode of action but the question of public
acceptance. Current discussion revolves largely around the use of the three natural
steroid hormones (oestradiol-17ß, progesterone and testosterone) and two
zenobiotic agents (trenbolone and zeranol). However, consumer resistance
concerning drug residues in some countries and public concern related to the
toxicological safety of these products has resulted in delays in their widespread use.
It is generally accepted that the three natural steroid hormones should be licensed;
however the use of the powerful anabolic agents, trenbolone and zeranol, is still
under active discussion. Because of their potential worldwide sale, these two
materials have probably been more widely studied in relation to their toxicology
than almost any other compound which might occur as a food residue, and new
toxicological procedures regarding tests of their possible genotoxic potential, their
mutagenicity and carcinogenicity are being investigated. Similarly to the naturally
occurring steroids, the two xenobiotic agents can be tumorogenic when used at high
dose levels in susceptible test species. This tumorogenic potential is generally
related to their hormonal action and the concept of a no-hormone effect level is
being developed to allow calculation of an acceptable daily intake. Until these
problems are resolved it is difficult to see the potential for development of new
compounds. No doubt those with commercial interests will await the outcome of
these discussions concerning safety before proceeding further with the heavy
commercial investment which is necessary for research into new compounds. It is
because of these reservations we await with interest the results from current
research into the potential use of ß-adrenergic agonists on metabolism and body
composition. However, I suspect that even if proven efficacious, these compounds
would also be subjected to the same degree of rigorous assessment concerning
aspects of safety.
It is in the third area that this meeting will, I am sure, generate the most interest,
namely that relating to the physiological mechanisms which control cellular growth.
Here is the greatest potential for quantifying and artificially manipulating animal
performance. We shall, I hope, hear that growth has caught up with reproduction,
through the major advances in knowledge of growth hormone control with the
identified and chemically characterized somatostatin and growth hormone releasing
factor and the negative feedback systems which operate to modulate growth
hormone secretion. This knowledge has already led to investigations into the
possibility of immunizing against endogenous growth hormone inhibitors as a
means of increasing growth at the practical level, and we shall hear more about this.
The possibility of manipulating growth and indeed lactation through the use of
exogenous sources of growth hormone or modified growth hormone fragments is an
area of research offering much potential. There is also tremendous interest in the
effect of growth hormone in stimulating the production and activity of plasma
peptides and most effort so far has focused on the two insulin-like growth factors,
IGF-1 and IGF-2. However, it seems that there exists a whole family of plasma
peptides which may be important, not only in relation to their direct effects on
skeletal growth but also in that they exert non-skeletal effects on DNA:RNA
ratios, on protein synthesis and the process of cell proliferation. The availability of
supplies of recombinant DNA-derived growth hormone, or fragments, and the
possibility of using these techniques to provide large quantities of IGFs should
facilitate studies of the growth-promoting activity of these materials in domestic
animals. Finally, we await the latest news regarding gene transfer in farm livestock
with the plethora of possibilities this could bring.
4 Introductory comments
Having expressed my reservations earlier about our abilities to develop new
techniques in some areas of growth physiology, I certainly have few reservations
about this third area and indeed, since the advances now being made are rapidly
reported, we are experiencing a great surge of interest, and I do not think it will be
a further 18 years before this Faculty organizes another symposium along these
lines.
A prime purpose of these Easter Schools is to illuminate the critical scientific
issues concerning a particular field of research and to indicate to the administrators
of funds for research programmes where the maximum potential for scientific
progress might lie. I have no doubt that the papers presented and discussed in the
next few days will go a long way towards doing just that for the control and
manipulation of animal growth.
2
ENVIRONMENTAL EFFECTS ON GROWTH AND DEVELOPMENT
D.L. INGRAM and M.J. DAUNCEY
AFRC Institute of Animal Physiology, Babraham, Cambridge, UK
Introduction
The influence of environmental temperature on growth and development has been
studied in many species. Over 100 years ago, the Bergmann-Allen Rule pointed
out that there is a tendency for animals living in the cooler regions of the world to
have a greater body size and shorter extremities than those in the warmer regions
(Bergmann, 1847; Allen, 1877). It had always been considered that these
morphological differences were related mainly to genotype. However, this cannot
be the complete explanation because under carefully controlled conditions the
tendency towards longer extremities in those living in the warm compared with the
cold can be seen even in litter mates (Weaver and Ingram, 1969).
Differences in the physical appearance of pigs kept at a warm or cold
environmental temperature have been noted by several workers (Fuller, 1965;
Pearson et al., 1966; Jensen et al., 1969; Weaver and Ingram, 1969). Animals in the
warm appear to be lean and elongated, while those in the cold, even when they are
litter mates of the same body weight, have a rotund appearance with short limbs
and snout, small tail and ears, and more hair. Other investigations have
concentrated on physiological or biochemical differences induced by environmental
temperature. However, in many studies animals are allowed to eat ad libitum, and
to produce animals of similar body weight those in the cold must eat more than
those in the warm. Thus, when analysing results it is not clear which effects are due
to temperature and which to food intake.
In this chapter attention will be focused on studies carried out in growing pigs in
which the separate and combined effects of ambient temperature and nutrition
have been evaluated. Particular attention has been paid to differences in
morphology, physiology, behaviour, cell structure and cell function.
Method of investigation
In order to control both environmental temperature and food intake, a model has
been developed in which 14-day-old piglets are first housed separately at 30 °C, and
then for half the litter the temperature is increased to 35 °C over a two-week period
while for the other half it is gradually reduced to 10 °C. At each temperature some
5