growth modifiers an s 426 spring 2007. growth modifiers general types general types 1.antibiotics...

Growth ModifiersGrowth Modifiers

An S 426 An S 426 Spring 2007Spring 2007

Growth modifiers Growth modifiers

General typesGeneral types1.1. Antibiotics – chlortetracycline (Aureomycin),Antibiotics – chlortetracycline (Aureomycin),

oxytetracycline (Terramycin)oxytetracycline (Terramycin)2.2. Growth promotants – estrogen (Compudose),Growth promotants – estrogen (Compudose),

estrogen-like (Ralgro)estrogen-like (Ralgro)3.3. Feed enhancers – monensin (Rumensin), Feed enhancers – monensin (Rumensin),

lasaloacid (Bovatec), ractopaminelasaloacid (Bovatec), ractopamine

hydrochloride (Optaflexx)hydrochloride (Optaflexx)

-adrenergic agonist-adrenergic agonist


Growth promotantsGrowth promotants

Mode of action:Mode of action:1.1. Evidence they change hormone status of animal.Evidence they change hormone status of animal.

2.2. Probably function at site of hormone production Probably function at site of hormone production and at the receptor sites of target cells.and at the receptor sites of target cells.

3.3. Thought to affect mechanism which causes Thought to affect mechanism which causes increased nitrogen retention in muscle.increased nitrogen retention in muscle.

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


Growth promotantsGrowth promotants

Mode of action:Mode of action:5.5. Exogenous estrogenic promotants are thought to Exogenous estrogenic promotants are thought to

enhance protein gain through increased enhance protein gain through increased production of growth hormone, insulin and insulin-production of growth hormone, insulin and insulin-like growth factors.like growth factors.

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


Characteristics:Characteristics:– Implants approved for insertionImplants approved for insertion

Most will be absorbedMost will be absorbed

– No withdrawal timeNo withdrawal time– Cost per implant will range fromCost per implant will range from

Effects on performance:Effects on performance:1.1. 5. 5. 2.2. 6. 6. 3.3. 7. 7. 4.4.


Characteristics:Characteristics:– Strategies for utilization:Strategies for utilization:

– Melengesterol acetate (MGA) Melengesterol acetate (MGA) Feed additive for suppressing heat in heifers Feed additive for suppressing heat in heifers

–– Similar effects on performanceSimilar effects on performance Effective dose =Effective dose = Cost = Cost =


Characteristics:Characteristics:– Melengesterol acetate (MGA) Melengesterol acetate (MGA)

Other uses of MGA:Other uses of MGA:1.1.2.2.

MGA / LutalyseMGA / Lutalyse5 ml injection of Lutalyse will cause most heifers 5 ml injection of Lutalyse will cause most heifers

lesslessthan 100 days pregnant to abort within 35 than 100 days pregnant to abort within 35 days (most within 14 days)days (most within 14 days)

Heifers can be started on MGA 7 to 10 days Heifers can be started on MGA 7 to 10 days following Lutalyse injection following Lutalyse injection


Feed enhancersFeed enhancers– Mode of action:Mode of action:

Increases feed conversion byIncreases feed conversion by

Summary by Elanco: Summary by Elanco:

Rumensin Rumensin Percent VFAs Percent VFAs

(g/T)(g/T) AceticAcetic PropionicPropionic Butyric Butyric

00 5252 3838 99

3030 4949 4343 77


Feed enhancersFeed enhancers

Considering that:Considering that:– 63% of energy from acetic acid is used for 63% of energy from acetic acid is used for

maintenance and productionmaintenance and production

– 100% of energy from propionic acid is used 100% of energy from propionic acid is used for maintenance and productionfor maintenance and production

– 75% of energy from butyric acid is used for 75% of energy from butyric acid is used for maintenance and productionmaintenance and production


Feed enhancersFeed enhancersStudy by Dr. Gill, Ok. St. Un. Study by Dr. Gill, Ok. St. Un.

Reason high silage diet showed greater improvement Reason high silage diet showed greater improvement in feedin feed

efficiency attributed to lower propionic acid level efficiency attributed to lower propionic acid level initially initially

SilagSilage e

RumensiRumensin n

Percent VFAs Percent VFAs ADADGG

Feed Feed FeedFeed Percent Percent

Level Level (g/T)(g/T) AcetiAceticc

PropionPropionicic

ButyriButyric c

ConsuConsum.m.

ConverConver. .

ImprovImprove.e.

30 %30 % 00 48.548.555

39.5539.55 11.9511.95 3.33.311

18.7718.77 5.695.69

5.665.66

3030 46.546.500

45.7045.70 7.857.85 3.23.277

17.8817.88 5.465.46

75 %75 % 00 61.661.600

24.7024.70 13.7013.70 2.52.522

18.5118.51 7.407.40

7.747.74

3030 54.754.755

33.7533.75 11.5511.55 2.42.499

17.0817.08 6.826.82


Characteristics:Characteristics:– Effective doseEffective dose

Rumensin:Rumensin:

150 mg/hd/day for less than150 mg/hd/day for less than200 mg/hd/day for 200 mg/hd/day for 330 mg/hd/day for330 mg/hd/day for

Bovatec:Bovatec:100-360 mg/hd/day100-360 mg/hd/day

Optaflexx:Optaflexx:Rumensin may reduce feed intake during Rumensin may reduce feed intake during

adaptation periodadaptation periodMay start cattle onMay start cattle on


Characteristics:Characteristics:– No withdrawal timeNo withdrawal time

Rumensin fatal toRumensin fatal to

– Costs:Costs:Rumensin –Rumensin –Bovatec –Bovatec –Optaflexx – Optaflexx –


Effects on performance:Effects on performance:1.1. 5.5.2.2. 6.6.3.3. 7.7.4.4.

Strategies for utilization:Strategies for utilization:Rumensin may be fed with Tylosin (rumensin 10-Rumensin may be fed with Tylosin (rumensin 10-

30 g/T + Tylosin 10g/T)30 g/T + Tylosin 10g/T)

Some research suggests feeding Rumensin and Some research suggests feeding Rumensin and Bovatec on alternate days or weeks toBovatec on alternate days or weeks to


Buller – steer syndromeBuller – steer syndrome Abnormal sexual behavior observed among Abnormal sexual behavior observed among

steers steers

Recipient of repeat mountings is referred to Recipient of repeat mountings is referred to as a buller steeras a buller steer

Results in:Results in:


Buller – steer syndromeBuller – steer syndromeKansas survey indicates 2.2% of all steers on Kansas survey indicates 2.2% of all steers on feedfeedremoved from pens because of this conditionremoved from pens because of this condition

Represented a minimum loss ofRepresented a minimum loss ofCause:Cause:

Chemistry: plasma contains more total Chemistry: plasma contains more total estrogens possibly as a result of stress and estrogens possibly as a result of stress and growth stimulants – thus estrogen may growth stimulants – thus estrogen may account for a pheromone secretion partially account for a pheromone secretion partially responsible for the buller syndrome.responsible for the buller syndrome.

growth modifiers an s 426 spring 2007. growth modifiers general types general types 1.antibiotics...

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