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Growth promotants and feed enhancers AnS 426 . Growth Modifiers. Two broad groups Agents that alter the digestive process Agents that modify the way the animal uses or partitions nutrients for growth. Growth modifiers . General types Antibiotic growth promoters Ionophores Implants

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growth modifiers
Growth Modifiers
  • Two broad groups
    • Agents that alter the digestive process
    • Agents that modify the way the animal uses or partitions nutrients for growth
growth modifiers1
Growth modifiers
  • General types
    • Antibiotic growth promoters
    • Ionophores
    • Implants
    • -adrenergic agonist
    • melengestrol acetate (MGA)
a ntibiotic growth promoters
Antibiotic growth promoters
  • Any medicine that destroys or inhibits bacteria and is administered at a low, subtherapeutic dose
  • Main antibiotics added to cattle feed
    • Chlortetracycline
    • Oxytetracycline
    • Tylosin
    • 3 to 5 % improvement in gain and FE
    • No withdraw if fed at subtherapeutic dose
slide5

Antibiotics fed to finishing cattle for the control of liver abscesses

When fed high concentration rations, cattle that are borderline on subacute acidosis and have a few small liver abscesses gain faster and more efficiently than cattle that are not stressed and have no liver abscesses. However, managing to allow a slight amount of acidosis is difficult.

feed enhancers
Feed enhancers
  • Ionophores
    • monensin (Rumensin)
    • lasaloacid (Bovatec)
  • Improve feed conversion
    • Increase efficiency of bacterial protein and energy metabolism
    • Can also reduce incidence of digestive upsets
growth modifiers2
Growth modifiers
  • Feed enhancers

Study by Dr. Gill, OSU

Reason high silage diet showed greater improvement in feed

efficiency attributed to lower propionic acid level initially

slide8
VFA

Why dose changing the VFA profile affect performance:

  • 63% of energy from acetic acid is used for maintenance and production
  • 100% of energy from propionic acid is used for maintenance and production
  • 75% of energy from butyric acid is used for maintenance and production
growth modifiers3
Growth modifiers
  • Effective dose

Rumensin:

150 to 330 mg/hd/day

Bovatec:

100 to 360 mg/hd/day

  • NO withdraw period
  • The effects of ionophores and growth promoting implants are additive
protein sparing
Protein “sparing”
  • Ionospheres decrease the breakdown of feed protein and thus increase bypass protein that reaches the small intestine
  • This has little effect on performance of feedlot cattle on high-grain diets, but it is important in growing cattle on high-roughage diets
  • The protein sparing effect on performance is maximized when natural protein is fed below the animals requirement
rumensin
Rumensin
  • Can be fed with tylosin or MGA

Finishing Cattle

    • 1 to 3 % improvement in daily gain
    • 6 to 8 % improvement in feed efficiency

Growing Cattle

    • 5 to 15 % improvement in daily gain
    • 8 to 12 % improvement in feed efficiency

Growing cattle on pasture

    • Provide in supplement or free choice mineral
    • Can supplement 300-400 mg/hd every other day
bovatec
Bovatec
  • Not cleared to be fed with antibiotics or MGA

Finishing cattle

    • 4 to 6 % improvement in daily gain
    • 6 to 8 % improvement in feed efficiency

Growing cattle

    • 5 to 15 % improvement in daily gain
    • 8 to 12 % improvement in feed efficiency
use of ionophores in transition to finishing diet
Use of Ionophores in transition to finishing diet
  • Cattle started on feed without ionophores
    • more erratic feed intake patterns
    • more digestive problems
use of ionophores in transition to finishing diet1
Use of Ionophores in transition to finishing diet
  • Rumensin
    • Feeding 100 mg/hd/d during the step-up period and then switching to 200-300
      • improves daily gain, feed intake, and feed efficiency compared to starting cattle on 200 -300 mg/hd/d
  • Bovatec
    • The response to stepping-up Bovatec??
      • Less?…Bovatec does not reduce intake as much as Rumensin early in the feeding period
i mplants
Implants
  • General types
    • Estrogen based (estradiol, zeranol, and progestrone)
    • Androgens (testosterone and trenbolone acetate or TBA)
    • Combination of estrogen and androgens
implants
Implants
  • No withdraw time
  • Cost usually between $1-3
  • Increase ADG 5 to 30%
  • Increase feed conversion 6 to 16%
how to implant
How to Implant

1) Load Implant Gun with implant cartridge

2) Insert needle between skin and cartilage in middle third of the ear

3) Pull trigger and retract needle

4) Check implant site with thumb

5) Disinfect needle

1) Load Implant Gun with implant cartridge

2) Insert needle between skin and cartilage in middle third of the ear

3) Pull trigger and retract needle

4) Check implant site with thumb

5) Disinfect needle

implants1
Implants

Mode of action:

1. Exogenous estrogenic promotants are thought to enhance protein gain through increased production of growth hormone, insulin and insulin-like growth factors.

2.Androgenic substances are thought to increase muscle growth by inhibiting the release of hormones (e.g. glucocorticoids) which cause degradation of muscle; this results in net shift in the partition of nutrients which is manifested by faster relative rates of muscle growth.

how implants work
How Implants Work

Pituitary

ESTROGENS

ANDROGENS

Growth hormone

Protein synthesis

Beta agonists

MUSCLE

X

Protein breakdown

implants and adrenergic agonists
Implants and -adrenergic agonists

Mode of action: “partition” nutrients into the more desirable, higher valued components (i.e. muscle) and away from the less desirable components of the carcass (i.e. fat) causing an apparent shift in the lean tissue growth.

adrenergic agonist
-adrenergic agonist

ractopamine hydrochloride (optaflexx)

Feed during the last 28 to 42 days of the finishing period

150-300 mg/hd/d and no withdraw

zilpaterol hydrochloride (zilmax)

Feed during the last 20 to 40 days of the finishing period

60-90 mg/hd/d and has a 3 d withdraw

adrenergic agonist1
-adrenergic agonist
  • Structurally similar to catecholamines and other compounds that bind to the beta-adrenergic receptor
  • Agonist: Able to bind to receptor and elicit response
  • beta-agonists works via the β-Adrenergic Receptor
slide24

“Repartitioning” effects are due to stimulation of lipolysis and changes in muscle protein metabolism

why do we only feed agonists at the end of finishing
Why do we only feed - agonists at the end of finishing?
  • Market cattle become less efficient during the last month of the finishing period, because the animal is depositing less muscle and more fat.
  • Chronic exposure to a ligand can cause desensitization of the receptor due to uncoupling or down-regulation of receptor
adrenergic agonist2
-adrenergic agonist

Optaflexx:

Rumensin may reduce feed intake during adaptation period

melengestrol acetate mga
Melengestrol acetate (MGA)
  • Similar to progesterone
  • Suppresses estrus of intact heifers
  • Reduces injuries and energy loss from riding and chasing
    • 3 to 7 % improves gain and feed efficiency
  • Effective dose 0.25-0.5 mg/hd/d
  • Cost about 1¢/da