Nutrient Requirements for Body
Functions
Topic 3041 Nutrients and Nutrient
Requirements
Developed by Amanda R. Moore
Overview
Definitions
Requirements for:
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Body Maintenance
Growth
Fattening
Reproduction
Lactation
Egg Laying
Wool Production
Work
Definitions
Metabolism
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All the chemical and physical properties that
take place in the body
Anabolism
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Metabolism that builds tissue
Catabolism
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Metabolism that breaks down materials
Nutrient Requirements for Body
Maintenance
Body Maintenance: A condition in which the
body is maintained without an increase or
decrease in body weight, and with no production
or work being done.
Examples:
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Body tissue repair
Control of body temperature
Energy to keep vital organs functioning
Water balance maintenance
Body Maintenance
Approximately 50% of feed is used to fill
the maintenance requirement
This must be met before supplying nutrients
for other functions
Maintenance needs are related to body size
Body Maintenance
Maintenance requirement in relation to
weight can be expressed as Wt.75
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Ie:If a 500-lb animal needs 15 lb of feed per
day for maintenance, a 1,000-lb animal of the
same type would not require twice as much
feed as the first. Instead: 1000.75 shows that
this animal requires 1.7 times as much as the
smaller animal = (15lb x 1.7 = 25lb)
Nutrient Requirements for
Growth
Growth is the increase in protein over its loss in
the animal body. It occurs by increases in cell
numbers, cell size or both
Growth requires energy, protein, minerals,
vitamins and energy
Young animals require more protein in order to
build muscle and grow
Mongastric animals also need certain amino acids
for proper growth
Growth
Young animals also need calcium and phosphorus,
salt or a normal sodium level, any mineral that
may be deficient in the area the animal lives
Iodine and Selenium require special consideration
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Iodine deficiency in the fetus prevents thyroxine
from being produced, causing goiters and eventual
death in newborns
Selenium deficiency may cause white muscle
disease in newborns
Growth
Vitamins are also required by growing animals
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Must be supplied to pigs and poultry through feeds
(usually vitamin D)
Vitamin A is usually the only vitamin commonly
fed to ruminants
Energy is required to sustain growth, metabolic
rate and activities
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Can be supplied by feeding corn, barley or wheat
Nutrient Requirements for
Fattening
Fattening: Storing of surplus feed energy as
fat
Results from excess energy from
carbohydrates, fats or protein beyond the
the maintenance requirements
Nutrient Requirements for
Reproduction
Two categories of requirements:
Gamete production
 Fetal growth in the uterus
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Fetus requirements are much greater in the
last trimester of pregnancy
Nutrition of the female must not be
inadequate during pregnancy
Nutrient Requirements for
Lactation
Milk production requires considerable
protein, minerals, vitamins and energy
The need for protein is greater because milk
contains more than 3% protein
Calcium and phosphorus are the two most
important minerals needed for lactation. If
absent, may result in decreased lactation,
disease or even death
Lactation
Energy is the most vital requirement for the
production of a large quantity of milk
High producing dairy cows may need up to
four times the energy of a nonlactating cow
of the same size.
Nutrient Requirements for Egg
Laying
Egg layers are usually fed free choice (as
much as they can eat)
It is important that rations have adequate
concentrations of energy, protein, vitamins
and minerals
Nutrient Requirements for Wool
Production
These are in addition to nutrients needed for
maintenance, growth and reproduction
Wool fibers are primarily protein, the ration
should be adequate in protein
Shearing may cause an increase in energy
requirements
Nutrient Requirements for Work
Large amounts of energy beyond the
maintenance needs
If energy is not sufficient in the ration, the
animal will begin to use body fat stores to
provide the additional energy needs
Resources
Taylor, Robert E. and Field, Thomas G. 1998.
Scientific Farm Animal Production, Sixth
Edition. New Jersey:Prentice Hall Publishing.
Desert Roses[online]:
www.ag.arizona.edu/desert_roses, 3/14/01