Recent Advances in Animal Nutrition–1991

245 Pages·1991·3.695 MB·English

by  W. Haresign and D.J.A. Cole (Auth.)

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Edited by C.J.C. Phillips
Recent Advances in Animal
Nutrition
1991
W. Haresign, PhD
D.J.A. Cole, PhD
University of Nottingham School of Agriculture
U T T E R W O R TH
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First published 1991
© The several contributors named in the list of contents 1991
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British Library Cataloguing in Publication Data
University of Nottingham Feed Manufacturers
Conference (25th 1991 Nottingham)
Recent advances in animal nutrition - 1991.
- (Recent advances in animal nutrition)
I. Title II. Haresign, W. III. Cole, D.J.A.
IV. Series
636.08
ISBN 0 7506 1397 1
Composition by Scribe Design, Gillingham, Kent
Printed and bound in Great Britain by Redwood Press Ltd, Melksham, Wiltshire
PREFACE
This book marks the Twenty-fifth Anniversary of the University of Nottingham
Feed Manufacturers Conferences. In the twenty-five years since 1967 there have
been marked changes in the challenges to the industry and in its response to them.
The programme of the first conference reflected the need for an industry to
improve efficiency and increase output. This year's conference reflected a changing
face of animal agriculture which now has a greater awareness of consumer attitudes
and the environmental consequences of animal production. For example, two
chapters address the problem of nitrogen and phosphorus excretion from pigs.
They seek to minimize excretion through greater precision in diet formulation and
by the use of enzymes. Protein and energy interactions in the diet of the pig are
examined in a chapter based on Australian experiences but are equally applicable
to intensive pig production in any country. The pig section is completed by a
chapter on the nutrition of the working boar. This is an often neglected area in
both research work and review coverage, which is surprising in view of the
importance of the boar in the breeding herd.
The growing interest in the use of dietary enzymes is reinforced in the poultry
section. In this case high levels of production are sought through the hydrolysis of
non-starch polysaccharides of barley, oats, rye, triticale and wheat in order that
they may match the value of maize. In recent years the importance of tailoring
nutrition to genotype has become particularly evident in pigs and poultry. A further
chapter on poultry considers the nutrition of fat and lean broiler genotypes which
have been selected on the basis of very low density lipoprotein (VLDL)
concentration in the plasma.
It has become evident that the immune system acts as a sensory organ to detect
the presence of foreign organisms in the body and the consequences of this are
examined in relation to the behavioural, cellular and metabolic changes that
influence growth and nutrient requirements. It is concluded that research should
detail the appropriate changes in nutritional management to maximize production
and immunocompetence during infectious challenges or in situations of poor
hygiene.
A regular feature of this series is the annual review of changes in legislation
which affect the feed compounder. Particular attention is paid to medicated feeds,
marketing of compound feeds, undesirable substances and Salmonella. In a further
chapter strategies for animal nutrition over the next ten years or more are
considered in relation to changing attitudes and legislation. In a period of change,
v
vi Preface
involving considerable overcapacity, it stresses the need for greater European
coordination.
In a ruminant section the balance of cations and anions, is considered in relation
to its influence on acid-base regulation in order to achieve a dietary cation-anion
balance that would optimize biological function and efficiency of production. On
a more practical level the nutrition of intensively reared bulls is considered. This
is particularly relevant in view of the dramatic increase in the number of bulls being
kept because of their claimed greater efficiency and to the advent of 'organic' bull
beef production. The farming of red deer is also expanding in the UK and their
nutritional requirements are considered in relation to their characteristic seasonal
appetite cycle. Finally, the principles of modelling nutrient supply for ruminants
is considered. It is suggested that mathematical models are themselves not capable
of 'fine-tuning', which relies on personal experience, and that better knowledge of
digestion and metabolism is needed. However, they do provide a ready framework
to test the effects of different diets on nutrient supply.
W. Haresign
D.J.A. Cole
1
ENERGY-PROTEIN INTERACTIONS IN PIGS
A.C. EDWARDS and R.G. CAMPBELL
Bunge Meat Industries, Corowa, NSW, Australia
Introduction
Knowledge of the factors influencing protein deposition capacity is crucial for the
design of diets and feeding strategies for growing animals and for predicting the
effects of change in feed or energy intake on growth performance and carcass
composition. Protein deposition can be constrained by both dietary and intrinsic
factors and in this chapter we have attempted to highlight the major factors
affecting protein growth and how these affect requirements of growing pigs for
dietary protein (amino acids) and the partition of energy between fat and protein.
The initial sections of the chapter concentrate on the interrelationship between
nutrient intake and the various animal factors as they affect protein growth capacity
and dietary requirements. The latter sections deal with dietary factors as they affect
nutrient 'requirements' and attempt to integrate the animal and dietary factors to
draw conclusions concerning the present state of knowledge and to identify areas
requiring further work.
PROTEIN AND ENERGY INTAKE EFFECTS OF PROTEIN DEPOSITION
The relationship between protein deposition and protein and energy intake consists
of two phases: (i) an initial protein-dependent phase in which protein deposition
is linearly related to protein intake and independent of energy intake or animal
factors such as sex or genotype, and (ii) an energy-dependent phase in which
additional protein is deposited only when energy intake is increased. These effects
are illustrated in Figure 1.1.
When pigs of a given weight are fed increasing amounts of protein, of a constant
quality, in conjunction with a set amount of energy (El), protein deposition
increases linearly until a maximum value (Ml) is reached at a particular level of
protein intake (A). Additional increments of protein will not produce any further
rise in protein deposition. However, when more energy is supplied (E2) protein
deposition increases up to new maximum value (M2) at a higher protein intake
(B). Thus protein deposition is unaffected by energy intake when protein is limiting
and, conversely, is driven by energy intake when dietary protein supply is equal
to or above requirement.
The slope of the linear component of the response functions is determined by
the digestibility and biological value of the dietary protein. The latter define
3
4 Energy-protein interactions in pigs
n
o
siti Energy-dependent
o
p phase
e
d
n
ei
ot
Pr
Protein-dependent phase
-Level E2-
-Level E
A B
Protein intake
Figure 1.1 Interrelationships between protein deposition and protein and
energy intake
protein quality and this in turn determines the quantity of dietary protein required
to support maximum protein deposition. In contrast Ml and M2 represent the
requirement at a tissue level and are independent of protein quality, but are
dependent on such animal factors as live weight, gender, breed or strain.
Consequently unless they are associated with improved dietary protein utiliza-
tion these factors must alter the level of dietary protein required to support
maximal rates of protein, or lean tissue, growth. For example the values Ml and
M2 in Figure 1.1 could be used to depict the difference in protein accretion capacity
comparing the intact male and female pigs provided with the same energy intake,
and the values A and B the amounts of dietary protein required to support maximal
protein deposition in the respective sexes.
The interrelationship between the pig's requirements for protein at the tissue
and dietary levels can be described by the equation:
PR( ) = RPD + OPL
D g / d
Dig x BV
where DPR = dietary protein requirement, RPD (g/d) = rate of protein deposition
(tissue requirement for growth), OPL (g/d) = obligatory protein loss (tissue
requirement for protein maintenance), Dig (%) = digestibility of dietary protein
and BV (%) = biological value of dietary protein.
If all these factors were measured in experiments to assess the growing pigs'
response to nutrient intake or any other factor which might influence growth
performance it would be relatively easy to determine the extent to which these
various factors might alter dietary protein requirements via their effects on either
tissue requirements and/or alteration of dietary protein utilization. Unfortunately,
such information is limited and these aspects should be seriously considered in the
design of future experiments to elucidate the effects of animal or dietary factors
on the growing pig's nutrient requirements.
A.C. Edwards and R.G. Campbell 5
It was mentioned previously that under conditions of dietary protein adequacy,
protein deposition is a function of energy intake and it is the form of the
relationship between energy intake and protein deposition which determines the
partition of energy between protein and fat components. This relationship has
consequent effects on energy intake (feeding level), growth performance and body
composition. However, for reasons discussed previously it is essential when
assessing the relationship between energy intake and protein deposition that the
diet is not protein deficient. Otherwise any improvement in protein deposition
resulting from increased feed intake will be in response to increased protein intake
independent of energy intake, and the animal will not be able to express its
inherent or metabolically enhanced capacity for protein growth.
In reviewing the available information for pigs the ARC (1981) mentioned the
paucity of experiments of appropriate design to define the relationship and
although favouring a linear relationship, which presumes there are no intrinsic
limits to protein deposition, commented that there was some support for linear-
plateau and curvilinear forms. These contrasting models imply markedly different
rates of change in the fat:protein ratio and different expressions of the pig's
requirement for dietary protein with change in energy intake.
It is now established that the relationship is essentially of the linear/plateau form
(Campbell, Taverner and Curie, 1985a; Dunkin and Black, 1987) with the plateau
value representing the animal's genetic or intrinsic limit for protein accretion. This
relationship and the consequent effects on the partition of energy retained as
protein and fat are shown in Figure 1.2.
Total energy retained increases linearly with energy intake (Figure 1.2a). Energy
retained as protein also increases linearly to point Q beyond which it remains
constant (maximal protein deposition). Energy deposited as fat is represented by
the difference between total and protein energy deposition. At zero energy balance
(maintenance energy requirement) protein gain is marginally positive but fat
deposition is negative and does not commence until energy intake reaches some
higher level (R as determined by factors such as gender and genotype). Figure 1.2b
represents the corresponding change in the fat:protein ratio of weight gain in
response to changing energy intake.
When protein deposition is linearly related to energy intake, which is the
situation up to ad libitum energy intake for young pigs (<50 kg) and some superior
genotypes, the fat:protein ratio and body fat content increase in a curvilinear
fashion and approach a constant or steady-state value. However, if protein
deposition reaches a plateau, further increases in energy intake result in a steep
rise in the fat:protein ratio and body fat content. Growth rate increases linearly
when protein deposition is similarly related to energy intake but the rate of increase
declines once the plateau is reached.
Whether protein deposition responds linearly to increased energy intake to the
limits of the animal's appetite or reaches a plateau at some intermediate level of
feeding markedly affects the rate and composition of live weight gain, feed
conversion ratio and expression of dietary protein requirements. For example the
concept of a constant protein (amino acid):energy ratio is only valid when protein
deposition is a linear function of energy intake.
This is simply because energy intake is always the major determinant of maximal
protein deposition and, providing the dietary protein:energy ratio is correct,
changes in feed intake and thus in the pig's tissue demand for protein will always
be satisfied by a concomitant change in dietary energy intake. Conversely, on the
6 Energy-protein interactions in pigs
(a)
Total energy retained
d
e
n
ai Energy retained
et as protein
r
y
g
er Energy retained
n
E as fat
(b)
n
ai
g
ht
g
ei
w
n
i
n
ei
ot
r
p
at
of f
o
ati
R
J L
R Q
Energy intake
Figure 1.2 Effect of energy intake on (a) retention of protein and fat where
protein retention is of a linear/plateau form, and (b) the corresponding ratio of
fatiprotein in weight gain
plateau, the pig's tissue requirement is independent of energy intake and dietary
requirements can only be expressed on a daily intake basis.
Nevertheless, the form of the relationship between energy intake and protein
deposition is affected by factors such as sex and genotype, and by metabolism
modifiers such as porcine somatotropin. Similarly the amount of dietary protein
required to support maximum protein deposition even in pigs of a known age, sex
or genotype is affected by amino acid availability and balance. Information is
required on all these factors if the tissue and dietary components affecting
A.C. Edwards and R.G. Campbell 7
performance and requirements are to be fully integrated. There is a need for
nutritional programmes to be founded on a more biological basis than they are
currently.
Animal factors
SEX
Pigs between 20 and 50 kg live weight
Females and castrated males have a lower capacity for muscle growth than entire
males. Whilst this difference is reflected to some extent in the different degrees of
energy restriction imposed on male and female finisher pigs, its practical
implications have not been fully explored or exploited.
During the earlier stages of development (to 50 kg), rate of protein deposition
increases linearly with increase in energy intake up to the limit of the animal's
appetite (Campbell, Taverner and Curie, 1985a) and the differences between the
sexes are generally only small but increase with live weight. Consequently, the
most appropriate feeding strategy in the period 20-50 kg is that which promotes
near maximum energy intake and thus most fully exploits this high potential for
muscle growth. The implementation of such a strategy allows very rapid growth,
but because rate of protein deposition is linearly related to energy intake, does not
result in excessive fat deposition or deterioration in feed:gain ratio.
However, ensuring maximum energy intake is not merely a matter of offering
pigs a 'grower' diet ad libitum. Between 20 and 50 kg, pigs eat to the limit of their
ingestive capacity which lies between 1.8 and 2.0kg/d. On the other hand, over
the same liveweight range the pig's demand for energy, which is a reflection of its
potential for protein and fat growth, lies between 30 and 32 MJ DE/d. Accordingly,
unless offered diets with energy concentrations between 14 and 15MJ/kg the
animal is unable to satisfy its demand for energy or fully to express its potential
for growth. The effect of dietary energy content on growth performance is shown
in Table 1.1, which gives the results of an experiment in which entire male pigs
were given five diets ranging in DE concentration from 11.8-15.1 MJ/kg between
22 and 50 kg live weight.
Table 1.1 EFFECT OF DIETARY DE CONCENTRATION ON THE
VOLUNTARY FEED INTAKE AND PERFORMANCE OF ENTIRE MALE
PIGS GROWING FROM 22-50 kg
Dietary energy content (MJ/kg)
11.8 12.7 13.6 14.5 15.1
Voluntary feed intake (kg/d) 2.19 2.21 2.19 2.17 2.05
Voluntary energy intake (MJ DE/d) 25.7 27.7 29.7 31.3 30.9
Daily gain (g) 695 776 847 898 913
Feed: gain 3.16 2.89 2.61 2.39 2.25
Carcass P2 (mm) 14.4 15.3 15.6 16.0 16.4
Campbell and Taverner (1986)