Feed Additives
AnSci 320
2-27-12
Lance Baumgard
baumgard@iastate.edu
Feed Additives
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Antibiotics: disease prevention
Coccidiostats: control parasites
Xanthophyll: makes egg yolks yellow
Hormones (hormone like): increases growth
Yeast, Fungi, Direct fed microbials:
Buffers: HCO3 etc.. Prevent rumen acidosis
Antioxidants: prevents feed from getting rancid
Pellet Binders: keeps feed in pellet form
Flavoring Agents: makes feed taste better
FEED ADDITIVES
• Feed additives used in livestock supplements and
rations to improve performance & animal health.
• Use of feed additives is strictly regulated in the
developed countries, and many others, to ensure:
– Human food safety; Animal safety.
– Additive efficacy; Minimal environmental impact.
• Dramatic increase in globalization of marketing
of animal products has led to more uniformity in
regulations among countries.
– Animal products must comply with the laws of
the countries to which they are being sold.
FEED ADDITIVES
• AFCO (American Feed Control Officials) provides
the U.S. mechanism for developing/implementing
uniform & equitable laws, regulations, standards,
and enforcement policies.
– Regulating manufacture, distribution, and sale of
safe and effective animal feeds.
• AFCO defines a feed additive as…
– "an ingredient or combination of ingredients added
to the basic feed mix …to fulfill a specific need."
– " …usually used in micro quantities and requires
careful handling and mixing"
FEED ADDITIVES
• In practice, feed additives are defined as feed
ingredients of a nonnutritive nature that…
– Stimulate growth or other types of performance.
– Improve the efficiency of feed utilization.
– Are beneficial in some manner to health or
metabolism of the animal.
FEED ADDITIVES
• Of the groups of additives classed as drugs, the
major groups include many different compounds:
– Antibiotics, nitrofurans and sulfa compounds.
– Coccidiostats, wormers (antihelminthics & others),
and hormone-like compounds.
• Feed additives have been used extensively in
the U.S. and many other countries since the
discovery & commercial production of antibiotics
and sulfa drugs in the late 1940s.
– The European Union recently banned feeding of
antibiotics to animals meant for human consumption.
FEED ADDITIVES
• Animal products are routinely tested to ensure
that feed additives are being used correctly.
– Use of feed additives has been beneficial to livestock
producers under our modern methods of production.
• Development of intense systems of management
and concentration of animals has been made
possible only because additives could be used to
help control various diseases and/or parasites.
– Broilers, laying hens, growing-finishing pigs, and
fattening cattle and sheep.
USE OF FEED ADDITIVES CLASSED AS DRUGS
• In the U.S., use & regulation of additives classed
as drugs is controlled by the Center for Veterinary
Medicine, within the FDA.
– To determine that drugs & medicated feed are properly
labeled for intended use and that animal feeds and food
derived from animals are safe to eat.
• Federal law states no animal drug can be used
in feed until adequate research submitted to the
FDA proves the drug is both safe and effective.
– In developing a new drug for use with animals,
manufacturers must go through extensive testing.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Requirements for Medicated Feed
• FDA requirements for medicated feed focus on
mixers who use human-risk drug sources.
– Mixers who do not use human-risk drug sources
are subject to less demanding regulation.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• Antibiotics are compounds produced by
microorganisms.
– With properties of inhibiting growth/metabolism of
some (not all) other microorganisms.
– In some instances, they may be toxic to warmblooded animals.
– Most antibiotic names end in -cin or -mycin.
• All antibiotics used commercially for growth
promotion are produced by fermentation
processes using fungi or bacteria.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• Antibiotics have been effective, in general, as
production improvers when fed at low levels to
young, growing animals.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• Use tends to result in an increased feed intake.
– Growth is nearly always increased, particularly with animals
exposed to adverse environmental conditions.
– Feed intake usually decreases in ruminants
• Response in growth & feed efficiency varies by animal
species, time of year and location.
– Antibiotic-fed animals are less apt to go off feed.
• Antibiotics may be useful for other purposes, such as the
prevention and control of a wide variety of animal and
poultry diseases.
• As a rule, reduce the incidence or severity of several
types of diarrhea
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• Some are approved at low levels of continuous use for
reducing the incidence of…
– Enterotoxemia (overeating disease) in lambs.
– Liver abscesses in fattening cattle
– Diarrhea in young mammals deprived of colostrum.
• In poultry, some claims include…
– Reduction in respiratory disease.
– Nonspecific enteritis (blue comb) & infectious sinusitis.
– Improved egg production and hatchability.
• Antibiotics are often used at therapeutic levels in
treatment or control of many common diseases.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• At higher levels for therapeutic treatments,
antibiotics have been very useful for…
– Cattle for treating or preventing stresses associated
with transportation and adjustment to new conditions.
– Treatment of diseases such as anaplasmosis in cattle
and bacterial enteritis in swine.
– Respiratory diseases, diarrhea, fowl cholera, fowl
typhoid, and breast blisters in poultry.
• In most instances, the higher levels are not
approved for long-term usage.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• Two antibiotics for use in cattle, monensin and
lasalocid, are unusual in that they give a good
response in both growing and mature animals.
– Approval was first received for use as coccidiostats
with poultry.
– Both of these antibiotics are quite toxic to horses.
Dietary Polysaccharides
Bacterial enzymes
Monosacharides (glucose: 6 Carbons)
CH4
H
Glycolysis
CO2
Acetate (2 C)
Butryate (4C)
Pyruvate (3 C)
Propionate (3C)
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• Obtaining approval for new feed additive drugs
has become more difficult in recent years.
– More investigative effort & expense are involved.
– As a result, not many new additives have been
approved in recent years.
• Very few additives are approved for horses,
rabbits, sheep, goats, ducks, pheasants & quail.
– No approvals are given for geese or pets such
as cats and dogs.
• The primary reason is the cost of obtaining
approval in relation to potential sales volumes.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• Many antibiotics approved for cattle are tested
with sheep, but few are ever approved for sheep.
– Even fewer for species other than cattle, swine,
chickens, and turkeys, because of the costs.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Antibiotics
• In poultry, the trend is to use one or more
antibiotics in nearly all broiler feeds.
– Most can be used for layers, except high levels
of chlortetracycline and erythromycin.
• Manufacturer approval must be obtained for
using different combinations of antibiotics.
– Or combinations of antibiotics & other controlled drugs.
• Far more drug combinations have been approved for
chickens & turkeys than all other animals combined.
– It is illegal to feed antibiotics at different levels or in
different combinations from those previously approved.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Arsenicals
• Arsenicals are all synthetic compounds
(chemotherapeutic agent) & include a number of
drugs used in turkey, chicken, and swine rations.
– Developed as a means of controlling parasites.
– Some compounds stimulate growth in the same
manner as antibiotics.
– The effect can be additive to antibiotic stimulation.
• Several arsenicals have claims of improved
growth production as well as improved feed
efficiency for chickens, turkeys, or swine.
– And control of blackhead in poultry & diarrhea in swine.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Arsenicals
• Arsenicals have the disadvantage that they may
accumulate in body tissues, particularly the liver.
– At the levels fed, they are not considered to be toxic.
– All have a minimum 5-day withdrawal period before
animals are to be slaughtered for human food.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Coccidiostats
• Coccidia are microscopic parasites.
– Coccidiostats include a wide variety of compounds,
ranging from a number of synthetic drugs to several
of the antibiotics.
• These drugs are of considerable importance to
the poultry producer because close confinement
methods used in modern facilities accentuate the
possibility of coccidiosis outbreaks.
– Evidence suggests coccidiosis is becoming a greater
problem with sheep & cattle in close confinement.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Nitrofurans
• The nitrofurans are antibacterial compounds and
are effective against a relatively large number of
microbial diseases.
– Continued use of nitrofurans has not as yet
developed bacterial resistance, as is the
case for some antibiotics.
• Nitrofurans are often used in combination with
other drugs, especially with swine and poultry.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Sulfas
• The first sulfa drug was synthesized in the
1930s, and early ones were used extensively
against some human diseases very difficult to
treat at the time.
• Most sulfas present problems with tissue
residues, and some of the injectables result
in tissue residues in edible cuts of meat.
– There has been a gradual withdrawal of sulfa
drugs as feed additives.
• Most of problems alleviated by sulfas can be
treated successfully with other drugs.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Hormone-like Production Improvers
• Melengestrol acetate is the only hormone-like
production improver remaining on the approved
list.
– Extensively used with beef heifers; it acts to suppress
estrus, resulting in more efficient and more rapid gain.
USE OF FEED ADDITIVES CLASSED AS DRUGS
Hormone-like Production Improvers
• Although not feed additives, several products
are available for use as subcutaneous implants.
– Hexestrol, (outside the U.S.)
– Zeranol (Ralgro™), said to be an anabolic agent.
– Synovex™, a combination of estrogen & progesterone.
– Rapid Gain™, a combination of testosterone &
estrogen
– Steer-oid™, a combination of progesterone and
estradiol.
• A high percentage of growing- finishing cattle are
treated with one or another of these implants.
Implants
– Implants for Growth Stimulation
• Designed for slow release
• Growth promotion, feed efficiency
• Products
 Ralgro
 Use in calves, growing cattle, feedlots animals
 70-110d response
 Cattle should be reimplanted every 65-100d for
maximum
 Magnum
 Double dose of Ralgro
 Best in initial 70-90d on feed
Implants
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Synovex or Implus
 Different forms for different cattle
 Stimulates muscle deposition
 Increases growth hormone secretion
Revalor
 Claims to improve gain 15-20%
 Improves feed efficiency 15%
 Duration of response 100d
 May reduce marbling
Feed Additives and Implants
• Hormone Implants
– Most are pelleted
– Synthetic or natural
– Improves rate of gain and feed efficiency
Hormone Implantation
USE OF FEED ADDITIVES CLASSED AS DRUGS
Hormone-like Production Improvers
• In ruminants, natural or synthetic hormones
produce a response that results from increased
nitrogen retention accompanied by an increased
intake of feed.
– Increased growth rate; Improvement in feed efficiency.
– Reduced deposition of body fat, which may, at times,
result in a lower carcass grade for animals fed to the
same weight as nontreated animals.
Steroids (Estrogens and Androgens)
• Classification
– Estrogenic
– Androgenic
• Predominate illegal steroid in humans
– Progestin
– Non-steroidal
Steroids (Estrogens and Androgens)
• Animal agriculture
– Approved for beef
– Not as effective in pigs
• Effects
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Increased protein accretion
Decreased fat accretion
Increased average daily gain
Increased feed efficiency
Negative side effects (humans)
• Both Genders
– Increased heart disease, liver cancer, acne, male
pattern baldness
• Females:
– Decreased breast size, deepening of voice, increase in body hair
• Males:
– reduced sperm production, shrinking of the testicles, impotence,
difficulty or pain in urinating, baldness, and irreversible breast
enlargement, testicular shrinking
Steroid summary
• Improves animal performance
– Approved for beef cattle
• Taken illegally by body builders
• Used legally for many health reasons
-agonists
• Reasons for interest:
– Human medicine
• Branchodialators
– Agriculture
• Increase growth
 Enhanced muscle
 Decreased fat
 Approved for pigs and cattle
 Feed supplement
 Orally active
-agonists
• Molecules that structurally resemble
epinephrine
– Caffeine, ephedrine, aspirin
• Easily made in the lab
• Muscle:
– Increase in muscle synthesis
– Decrease in muscle breakdown
• Fat
– Decrease in lipogenesis
– Increase in lipolysis
control
50 d/150.5 kg feed
100 kg of bw
46 d/132 kg feed
-agonist
75 kg
Moody et al., 2000
Ham
14.3 kg
Loin
11.2
Shoulders 11.9
Belly
10.2
13.3 kg
10.7
11.2
10.3
Carcass lean 43.9
39.4
 Agonist summary
• Structurally resembles epinephrine
• Increases muscle synthesis
– Need to increase the protein % of diet
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Decreases fat content
Orally active
Desensitization
Recently approved for pigs and beef cattle
Buffers and Neutralizers
– Buffers & Neutralizers
• Compounds that minimize pH decreases
 Sodium bicarbonate
 Potassium bicarbonate
 Calcium carbonate
 Mag oxide
 Mag carbonate
DFMs and Yeast
– Lactobacillus, streptococcus, fungi, aspergillus, bacillus
– Probiotics
• Scientifically inconsistent
• Consist of microbial cultures
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Can stimulate cultural growth
• Reasons for use
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Increase/balance beneficial bacteria
Reduce toxic byproducts of digestion
Support rate of gain and feed efficiency
Alleviate/minimize stress
• Various times for use
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When do you use them?
• Available forms
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Feed additives
Water dispensing
Bolus/gel form
Pet Food
• Pet food, including dry and canned food and pet treats, is
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considered to be animal feed. Like other animal feed,
FDA regulates pet food and establishes standards for
labeling.
Pet food labeling is regulated at two levels: federal and
state. The federal regulations, enforced by FDA’s Center
for Veterinary Medicine, establish standards that apply to
all animal feeds:
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proper identification of the product
net quantity statement
manufacturer’s address
proper listing of ingredients
• FDA carries out its animal feed regulatory responsibilities
in cooperation with state and local partners, and works
together with AAFCO on uniform feed ingredient
definitions and proper labeling.