Module 5

1
Module 5 Growth Promotants
2
Nutrient Utilization
Animal
Intake Diet Digestion Nutrient
Pools Tissue Absorption Growth
Steroids ß-agonists
Probiotics Antibiotics
3
MICROBIAL CULTURES IN THE RUMEN
DIET
Saccharomyces cerevisiae Live culture
MICROBIAL CULTURE

• Stabilize rumen
• environment
• gas/pH/ammonia
• cellulolytic bacteria
• rate fibre degradation
• acetatepropionate
• microbial protein production

RUMINAL RESPONSE
INCREASED INTAKE
POST RUMINAL RESPONSE
viable cells nutrient uptake toxin adsorption
PRODUCTION RESPONSE
WHOLE TRACT RESPONSE
rate of digestion digestibility
milk or live weight
4
Probiotics

• 1) Probiotics consist of specific microbial
  cultures and/or ingredients that stimulate
  cultures capable of modifying the
  gastrointestinal environments to favor healthy
  tissue development.
• 2) Commercially available products may contain
  pure or combined cultures of
• Lactobacillus
• Streptococcus
• Pediococcus
• Aspergillus
• Bacillus
• 3) Probiotics are available as
• Feed additives (heat from pelleting or long
  storage may render certain product non-viable).
• Water dispensing
• Bolus or gel form
• 4) Use of probiotics is most frequent in newborn
  foals, dairy replacement calves, growing/adult
  horses, lactating dairy cows, incoming feedlot
  cattle, sick pens and hospitals, newborn baby
  pigs and various pets. In general, young animals
  or animals in stress will be more likely to
  respond to microbial inoculation.
• 5) Reasons for using probiotics include
• Increase or balance the beneficial intestinal
  bacteria
• Reduce toxic byproducts of digestion

5
Antibiotics
6
Steroids

• General classifications
• Estrogens estradiol and estrone
• Non-steroidal compounds with estrogenic activity
  -diethylstilbestrol (DES) and zeranol
• Androgens testosterone and trenbolone acetate
  (TBA)
• Progestagens progesterone and melengestrol
  acetate (MGA)
• ß-adrenergic, ß agonists, repartitioning agents
• lipolysis (fat mobilization), protein
  synthesis eg clenbuterol, cimaterol ractopamine

7
Commonly Used Steroidal Growth Promotants
8
Hormonelike Products for Growth
Stimulation Hormones are substance which are
formed in endocrine organs and which activate
specifically receptive organs when transported to
them by the body fluids. Synthesized compounds
which produce the same responses as those from
naturally produced hormones can be used to
promote animal growth when administered as either
a feed additive or a subcutaneous implantation.
9
Hormonelike Products as Feed Additives

• Melengestrol acetate (MGA)
• MGA is a synthesized steroid which is closely
  related structurally to progesterone.
• Feed continuously to feedlot heifers at 0.25 to
  0.50 mg per head daily. Not effective in
  pregnant or spayed heifers or in steers.
• Claims include
• --Growth stimulatin (7-11)
• --Improved feed efficiency (6-10)
• --Suppression of estrus
• Must be removed from the feed at least 48 hours
  prior to slaughter.
• Mode of action includes suppression of estrus as
  well as elevated endogenous estrogen levels which
  stimulate growth hormone release and growth
  promotion.

10
Implants
An implant is a substance implanted into the
animal body and designed to release slowly, but
constantly, the active chemical(s) for the
purpose of growth promotion, improved feed
efficiency or control of some physiological
function.
11
Hormonelike Products as Implants

• Ralgro-an implant pellet
• The active ingredient is zeranol which is made
  from zearalenone, a natural metabolite of the
  mold Gibberella zeae.
• Cleared for use in calves, growing cattle,
  feedlot steers and heifers, as well as feedlot
  lambs. Not cleared for breeding animals.
• Claimed to improve gain (8-12) and improve feed
  efficiency (7-10) in feedlot beef cattle and
  sheep.
• Cattle may be implanted anytime up to 65 days
  before slaughter. The duration of response is 90
  to 120 days. Cattle should be reimplanted every
  65 to 100 days for optimum results.
• Dosage level 36 mg in cattle 12 mg in sheep
• Produces a potent anabolic property by increasing
  secretion of growth hormone.
• Enhances retention of nitrogen and promotes
  skeletal growth without an increased deposition
  of fat.

12
Hormonelike Products as Implants

• Synovex-an implant pellet
• Synovex-S (for steers over 400 lb BW) each
  implant contains 20 mg of estradiol benzoate and
  200 mg of progesterone
• Synovex-H (for feedlot heifers over 400 lb BW)
  each implant contains 20 mg of estradiol benzoate
  and 200 mg of testosterone
• Synovex-C (for steer or heifer calves 45 days to
  400 lb BW) each implant contains 10 mg of
  estradiol benzoate and 100 mg of progesterone
• Not for veal or replacement breeding animals
• Claimed to improve gain (10-15) and improve feed
  efficiency (7-12)
• Reimplanting is recommended from 60 to 90 days
  after the previous implant
• Mode of action includes stimulating muscle
  deposition at the cellular level and also
  increased secretion of growth hormone.

13
Hormonelike Products as Implants

• Compudose-a drug impregnated silicone rubber
  implant
• The active ingredient is a natural steroid,
  estradio-17 B which is consistently released over
  a 200 day period. Each implant contains 24 mg of
  estradiol.
• Approved for steers only beneficial to suckling
  calves, growing steers on pasture, as well as
  feedlot steers.
• Claimed to increase average daily gain of
  suckling calves by 5 9-16 in growing steers,
  and up to 17 in feedlot steers. Also improves
  feed efficiency by 7 in feedlot steers.
• Molecules of estradiol are released into the
  circulatory system of the animal, thereby
  stimulating the pituitary gland to produce more
  growth hormone, which increases protein
  deposition. The estrogenic substances are a type
  of anabolic steroid that cause growth promotion.

14
Animal
Intake Diet Digestion Nutrient
Pools Tissue Absorption Growth
Steroids ß-agonists
Probiotics Antibiotics Ionophores