IMPLANTS: A VALUABLE TOOL FOR THE CATTLE FEEDING ...

IMPLANTS: A VALUABLE TOOL FOR THE CATTLE FEEDING INDUSTRY 

MECHANISM, STRATEGY AND TECHNIQUE 1 

I. INTRODUCTION 

Fred D. Lehman, DVM, MABM, DACT, Hoechst Roussel Vet 

Jerry R. Rains, MS, DVM, DACT Hoechst Roussel Vet 

Estrogen-containing implants were first 

used in the 1950’s. Following a long hiatus 

in the development of new hormone growth 

enhancing products, products containing the 

potent anabolic agent, trenbolone acetate 

(TBA), entered the market in 1987 (US) and 

1994(Canada). These new products improve 

average rate of gain by 30% and feed 

conversion by 17%, when estrogen plus TBA 

is implanted twice during the feeding period, 

as compared to non-implanted controls. 1 For 

optimal animal response, the production 

consultant should be aware of the potential 

and programmatic use of growth promotant 

implants. 

II. MECHANISM OF ACTION 

How estrogen (E 2 ) and TBA promote 

growth was recently reviewed by Johnston, 

et al. 2 E 2 implantation of steers increases 

concentrations of circulating somatotropin 

(ST) and insulin-like growth factor-1 (IGF-1). 

Dependent on ST concentration, IGF-1 is a 

mitogenic peptide that stimulates cellular 

proliferation and differentiation in muscle and 

other tissues. TBA alone, or TBA + E 2 

combinations do not stimulate ST secretion, 

but they do elevate circulating IGF-1 levels. 

Androgens, such as TBA, stimulate cell 

membrane androgen receptors that increase 

cellular production of protein. 

Simultaneously, adreno-corticotrophic 

hormone (ACTH) production is reduced. 

Because ACTH increases catabolism of 

protein, lowering ACTH reduces the rate of 

protein catabolism. Hence, androgens are 

anabolic and anti-catabolic. 

The combination of estrogen with 

androgen (E 2 +TBA) increases concentration 

of IGF-1 and specific insulin-like growth 

factor binding proteins (IGFBP). Mitogenic 

activity was greater in sera from E 2 +TBA 

implanted than non-implanted steers. Such 

actions may explain the increases in feedlot 

performance and rate of protein accretion 

observed with Revalor®-S use. 2 

The combination of E 2 +TBA enhances 

growth above the capacity of either hormone 

independently. 4,5,6 The net effect on weight 

gain is synergistic to that of E 2 or TBA alone. 

III. RESPONSE DYNAMICS & PERFORMANCE 

Growth response presumably depends 

on the level and type of circulating hormones. 

Currently commercially available implants 

differ in dosage, ingredients, bioactivity, 

matrix formulation, and duration of release 

(Table 1). The hormone concentrations 

typically peak a few hours after implant 

administration. Thereafter, serum hormone 

concentrations decline gradually and 

eventually reach a concentration where 

production is no longer enhanced, a 

“threshold” level. The duration for 

Synovex®-S and Revalor®-S is 

approximately 120 days.- 1,7 Other implants, 

including Finaplix-S® 4,8 , Finaplix-H® 4,9 , and 

Ralgro® 10 have shorter duration; 

Compodose® 11 has a longer release pattern. 

As with most implants, gain response 

from Revalor®-S was maximum in the first 

35 days following implantation 1 . During 35 

day periods through 140 days, implant 

responses declined unless the animals were 

re-implanted, presumably reflecting 

circulating hormone concentrations. To 

maximize gain while producing a lean 

carcass, producers must use aggressive 

implant programs that include reimplanting. 

1

Table 1. 

Implant 

Implants: Approvals, Growth Promotant, & Release Time 

Approval: Animal 

And hormone (mg) 

Estrogenic 

Effect (mg) 

Androgenic 

Effect (mg) 

Anabolic 

Effect 

(Days) 

Original or 

Generic 

Synovex-C 

Calves 400 lbs 

14.4 0 120 Original 

20 estradiol benzoate/ 

200 testosterone 

Synovex-H 

Heifers >400 lbs 

14.4 200 T-4 120 Original 



Implus-H 


14.4 200 T-4 120 Generic 



Component E-H 


14.4 200 T-4 Unknown Generic 



Revalor-G 

Pasture Steers & Heifers 

8 40 TBA 120 Original 

8 estradiol 17 beta/ 

40 TBA 

Ralgro Magnum Steers in confinement 

22-26 0 Unknown Original 

72 Zeranol 

Compudose 200 

All Classes 

24 0 168 Original 

24 estradiol 17 beta 

Compudose 400 

All Classes 

48 0 336 Original 

48 estradiol 17 beta 

Finaplix-S Confinement Steers 140 TBA 0 140 TBA 105 Original 

Component T-S Confinement Steers 140 TBA 0 140 TBA Unknown Generic 

Finaplix-H Confinement Heifers 200 TBA 0 200 TBA 105 Original 

Component T-H Confinement Heifers 200 TBA 0 200 TBA Unknown Generic 

Synovex-Plus Confinement Steers 28 

estradiol benzoate/200 TBA 

Revalor-S 

Confinement Steers 

24 estradiol 17beta/120 TBA 

Component TE- 

Confinement Steers 

S 


Revalor-H 

Confinement Heifers 




24 120 TBA Unknown Generic 


NOTE: 

1) estradiol benzoate = 72% estradiol-17B when computing estrogenic effect 

2) T-4 = Testosterone and TBA = Trenbolone Acetate: 1 mg. TBA has 8-10X growth promotion effect compared to 1 mg 

testosterone 

Ralgro ® and Ralgro Magnum ® : product of Schering-Plough 

Compudose ® : product of Elanco, marketed by Vet Life 

Synovex ® -S, Synovex ® -H, Synovex ® -C: products of Fort Dodge Labs. 

Implus ® -S, Implus ® -H, Calf-oid ® : products of Ivy Labs., marketed by Pharmacia Upjohn 

Component ® E-C, Component ® E-H, Component ® E-S, Component ® TE-S, products of Ivy Labs., marketed by Vet Life 

Revalor ® -G, Revalor ® -S, Revalor ® -H, Finaplix ® -H, Finaplix ® -S: products of Hoechst Roussel Vet 

2

However, to maximize fat deposition and 

marbling, more conservative strategies are 

useful. 13 

If implants act through hormone 

concentrations, higher dose levels should 

provide higher rates of gain. One dose of 

24mg of estradiol-17B plus 120 mg. of TBA 

(Revalor®-S) improved performance by 3% 

when compared to two doses of 20 mg 

Estradiol-benzoate (Synovex-S®) reimplanted 

during a 140 day feeding period (Table 2). 

Two doses of Revalor®-S improved 

performance by nearly 10% over the two 

doses of 20 mg. Of estradiol-benzoate in the 

same time period. 14 Responses observed in 

Canadian trials were 1.1 – 2.6% numerical 

increase for a single dose of Revalor®-S, 

versus two doses of Synovex®-S (reimplant) 

in 121-149 day feeding periods, 

respectively. 15 

However, more is not always better. 16 

Administration of multiple implants within a 

short interval (“stacking”) or excess estrogen 

or androgen can have adverse effects, 

perhaps via down-regulation of the 

hypothalamus and (/or) occupation of 

estrogen receptor sites. 17 Implanting too 

frequently may also contribute to an 

increased incidence of estrus-like behavior 

between individuals. 

Table 2. Revalor-S® five trial summary (US data) 14 

Day 1 

Day 60 

Revalor-S 

-- 

Synovex-S 

Revalor-S 

Revalor-S 

Revalor-S 

Synovex-S 

Synovex-S 

Production Data 

Initial Wt., lb. 755 755 757 754 

Final Wt., lb. 1224 1227 1242 1210 

Total Gain, lb. 469 472 485 456 

ADG, lb. 3.43 bc 3.45 b 3.56 a 3.33 c 

Intake (DM), lb. 20.88 20.52 21.03 20.71 

Feed/Gain 6.09 b 5.95 c 5.91 c 6.22 a 

Carcass Data 

Hot Carcass, lb. 777 c 783 b 792 a 770 d 

% Choice 68 a 70 a 61 b 69 a 

Backfat, in. .51 b .54 a .51 b .52 b 

Yield Grade 3.09 3.13 2.99 3.00 

Cost of Gain/cwt. $50.85 $50.02 $49.93 $51.77 

Profit/hd.(live basis) $36.10 $40.65 $44.38 $28.95 

abc = Means in same row with different superscripts differ (p

where the plane of nutrition is low 

enough to limit daily gain to 1.0-1.25 

lbs per day or less, the use of an 

estrogenic implant may result in little 

or no response, and deferred 

implanting should be considered. 

• Use of appropriate implants. Only 

implants approved for use in pasture 

cattle should be used in this phase of 

production. Use of higher-dose 

implants will not enhance grazing 

phase gain since plane of nutrition 

(forage quality and quantity) is limiting 

and will not allow the animal to 

respond to higher doses with greater 

weight gains. Further, use of higherdose 

implants in backgrounding and 

stocker cattle may result in a 

diminished response to implants in 

subsequent phases of production. 

• Implanting intervals. Grazing 

implants should not be administered 

within 60 days of a previous implant. 

Implanting in shorter intervals may 

cause too high a hormone level in the 

blood (particularly for estrogenic 

implants). The potential side effects 

are depressed performance, and 

increased estrus activity, and vaginal 

prolapse in heifers. Therefore, it is 

important to know as much as 

possible about the previous implant 

history of cattle purchased for 

backgrounding or stocker purposes. 

Reimplanting cattle midway through 

season-long grazing periods does not 

appear necessary for maximum 

performance, unless forage quality 

remains high, or high levels of 

supplemental feed are fed. 

Feedlot: Strategies for feedlot implant 

use depend on the implant’s ingredients, 

levels, payout period, and impact on 

performance. Historically, producers have 

administered estrogen implants at 80 to 100 

day intervals following arrival; often 

disregarding the relationship to slaughter. 

However, if the finished animal is the endproduct, 

the focus of the program becomes 

administering the implant at the proper time 

before marketing. This allows producers to 

use implants and implant strategies to 

influence performance and carcass quality. 

Because live rate of gain decreases as 

an animal approaches maturity, larger 

animals can respond to larger doses of 

hormone, and the terminal implant becomes 

the cornerstone of an implant program. 

Products that contain estradiol plus 

trenbolone acetate offer certain advantages 

as terminal implants. Time of administration 

of the terminal implant should correspond 

with the producer’s respective goal as shown 

in Table 3. 

Table 3. Goals of implant strategies 

Maximum over all performance and feed 

efficiency. 

Maximum quality grade*. 

Combination of performance and quality 

grade*. 

*(in reference to USDA grading system.) 

If rate and efficiency of gain are the 

priority, the terminal implant should be 

administered 70-80 days prior to slaughter. 

Some reduction in quality grade could be 

expected with aggressive implant use, 

especially if a TBA-containing implant is 

preceded by an initial TBA-containing 

implant 14. Conversely, yield grade tends to 

be improved since the carcass will be 

leaner 14 . Based upon the Canadian grading 

system, aggressive use of TBA may be 

desirable. 15 

Administration of the terminal implant 

100-135 or more days prior to slaughter as 

the hormone levels decline permits marbling 

scores to recover. At this time, protein 

accretion rate will have slowed to the 

animal’s inherent capability, resulting in 

protein:fat ratio comparable to that of nonimplanted 

aniamls. 18 The weight gain 

advantage is largely maintained, but the rate 

of gain declines as hormone levels decline. 

This strategy results in quality grades that 

equals or approaches non-implanted 

animals. 5,18 However, when hormone levels 

and stimulus have been allowed to decrease, 

4

overall rate of gain and feed efficiency will 

not be maximized. 

The implant(s) that precedes the terminal 

implant should be selected based on the 

length of the period and corresponding 

performance objectives. For example, if the 

total feeding period is projected to be 140 

days, and if the terminal implant is to be 

administered 90 to 100 days prior to 

slaughter, a relatively short-acting implant 

can be used as the initial implant. This 

should provide an intermediate approach and 

yet combine moderate performance with 

satisfactory quality grade. However, if 

performance is the primary objective, 

Revalor® may be administered 70 days prior 

to slaughter preceded by a Revalor®. 

Finally, if quality grade is a component of 

carcass price and the animals are projected 

to grade at the choice/select interface, a 

Ralgro ® followed by Revalor ® or one 

Revalor®-S administered on arrival with no 

reimplant should be used. In this 

conservative approach, quality grade may 

not be depressed but some sacrifice in the 

rate and efficiency of gain may occur. 4,13,14 

V. TECHNIQUE 

Processing crews often are not 

concerned about proper implant 

administration. The consulting veterinarian in 

conjunction with management must properly 

train crews about implant techniques. Some 

method of quality assurance to assess 

performance at processing will help maintain 

proper technique. 19,20 

Abscess-related problems top the list of 

unsatisfactory implants (Table IV). Proper 

administration begins with sanitation. 

Implant guns and trays should be cleaned 

prior to use. Implants should be kept in a 

clean container, such as a plastic bowl with a 

sealable lid. A tray containing a roller or 

sponge soaked with the appropriate 

clorhexadine/water solution should be 

located near the head gate so that the needle 

can be wiped clean between each use. 

Likewise a bucket containing disinfectant 

and 

a brush should be available to scrub the ears 

if they are soiled. 

The location of the implant should be on 

the caudal side, in the middle one-third of the 

ear. Veins should be avoided since 

lacerated blood vessels may cause the 

implant to be rejected or accumulation of 

blood could contribute to an abscess. 

Placement at the base of the ear results in 

more rapid absorption due to increased blood 

supply. USDA-FSIS forbids placement in the 

base of the ear to prevent adulteration of 

edible meat. With one hand the ear is 

stabilized; with the other hand, the implant is 

administered. If the needle slips over the 

surface of the skin, it should be re-wiped in 

disinfectant because the needle will retain 

pyogenic material. Withdrawal of the needle 

from the ear requires operator finesse to 

prevent gaps or crushing of the individual 

implant pellets. Either separating or crushing 

the implants could alter absorption and 

contribute to undesirable performance or 

“bullers”. 20 The injection site always should 

be pinched to seal the wound. Finally, the 

implant should be palpated with the thumb to 

ensure proper implant placement. 

Although this technique appears simple, 

improper head restraint or faulty equipment 

complicates the procedure. Implanting 

should be the rate-limiting step during 

processing. Slowing the processing rate 

helps to emphasize the importance of proper 

implanting technique to the processing crew. 

An on-going US survey of implant 

placement conducted by Hoechst Roussel 

Vet in commercial feedlots in midwestern and 

southwester feeding states indicates that 

implants are placed properly in only 86% of 

the cattle implanted at the feedlot (Table 4). 21 

An implant that is not properly placed or is 

otherwise unsatisfactory probably costs an 

average of $18.00 per animal. Thus, for 

each 10,000 processed, if 15% are not 

properly implanted, the total unrealized loss 

amounts to $27,000. Improving proper 

placement rate from 85% to 95%, would yield 

an additional $1.80/head. 21 

5

Table 4.HRV implant placement survey 21 

Problem % of Total Implants 

Abscess 6.9 

Bunched 0.3 

Cartilage 2.4 

Fluid 0.4 

Misplaced 0.7 

Missing 1.7 

Multiple 0.1 

Separated 0.5 

Partial 1.0 

VI. MAKING RECOMMENDATIONS 

Growth promoting implants can help 

reduce the cost of production and improve 

the consistency of beef produced. Thus the 

potential benefits, appropriate use, and 

misuse of implants have an impact both on 

individual producers and on the total beef 

industry. Implant planning should consist of: 

1. Projecting days on feed, 

2. Proper selection and timing of the 

terminal implant, 

3. Selecting initial implants, 

4. Making adjustments as needed. 

REFERENCES 

1. Preston R.L. and J.R. Rains. 1995. Response 

dynamics to Revalor®-S implantation in steers. 

Revalor®-S Tech Bulletin 10. Hoechst-Roussel 

Agri-Vet Company, Somerville, NJ. 

2. Johnston, B.J., M.R. Hathway, P.T. Anderson, J.C. 

Meiske and W.R. Dayton. 1996. Stimulation of 

circulating insulin-like growth factor-1 (IGF-1) and 

insulin-like growth factor binding proteins (IGFBP) 

due to administration of a combined trenbolone 

acetate and estradiol implant in feedlot cattle. J. 

Anim. Sci. 74:372-379. 

3. Roussel Uclaf. 1986. Revalor®. Paris. 

4. Anderson, P.T. 1991. Trenbolone acetate as a 

growth promotant. Compend. Contin. Educ. Pract. 

Vet. 13(7):1179-1190. 

5. Gerken, C.L., J.B. Morgan, G.C. Smith, J.D. Tatum 

and K.L. Hossner. 1994. Use of cloned calves to 

determine the mechanisms by which estradiol and 

trenbolone acetate enhance muscle growth. Dept. 

of Ani. Sci., Colorado State U., Fort Collins, CO. 

6. Trenkle, A. 1990. Evaluation of Synovex-S, 

Synovex-S + Finaplix-S and Revalor-S implant 

program in finishing steers. J. Anim. Sci. 

68(Suppl):479. 

7. Rumsey, T.S., A.C. Hammond and J.P. McMurtry. 

1992. Response to reimplanting beef steers with 

estradiol benzoate and progesterone: performance, 

implant absorption pattern, and thyroxin status. J. 

Anim. Sci. 70:995-1001. 

8. Hoechst-Roussel Agri-Vet Company. 1987. 

Freedom of information summary for Finaplix®-S 

(trenbolone acetate and estradiol). Somerville, NJ. 


Freedom of information summary for Finaplix®-H 

(trenbolone acetate and estradiol). Somerville, NJ. 

10. Pusateri, A.E. and D.C. Kenison. 1993. 

Measurement of zeranol in plasma from three blood 

vessels in steers implanted with zeranol. J. Anim. 

Sci. 71:415-419. 

11. Elanco Products Company. 1982. Compudose 

payout-delivery of estradiol in Compudose technical 

Manual: Controlled release implant for beef cattle. 

Division of Eli Lilly and Company, Indianapolis, IN. 

pp. E1-E7. 

12. Thornsberry, M. 1992. Personal Communication. 

Pittman-Moore, Inc., Mundelein, IL. 

13. Nichols, W., J. Rains and F. Taylor. 1993. Implant 

strategies for feedlot steers. Revalor®-S Tech 

Bulletin 12. Hoechst-Roussel Agri-Vet Company, 

Somerville, NJ. 


Pooled summary of five feedyard trials with 

Revalor®-S, Finaplix®-S, and/or Synovex®-S 

administered to yearling steers during finishing 

period in Revalor®-S Tech Bulletin1. Somerville, 

NJ. 

15. Jim, G.K., P.T. Guichon and C.W. Booker. 1995. A 

comparison of estradiol 17B/trenbolone acetate 

(Revalor®) implant programs to conventional 

estradiol benzoate (Synovex®) implant programs in 

feedlot steers in western Canada. Hoechst 

Canada, Inc., Regina, Saskatchewan, Canada. 

16. Hoechst-Roussel Agri-Vet Company. 1996. Know 

the Facts about Revalor®-S and Synovex®-Plus 

in Feedlot Forum. Special edition. 

17. Perry, T. 1992. Personal Communication. Cornell 

University, Ithaca, NY. 

18. Johnson, B.J., P.T. Anderson, J.C. Meiske and 

W.R. Dayton. 1996. Effect of a combined 

trenbolone acetate and estradiol implant on feedlot 

performance, carcass characteristics, and carcass 

composition of feedlot steers. J. Anim. Sci. 

74:363-371. 

19. Hollis, L. 1989. Proper management of implant 

technique in feedlot cattle. Compend. Contin. 

Educ. Pract. Vet. 11:763-768. 

20. Rains, J. and D. Nash. 1990. Implanting: waste 

not. Large Ani. Vet. Jan/Feb:18-21. 

21. Lehman, F.D. 1995. Revalor®-S Tech Bulletin 14- 

B. Hoechst-Roussel Agri-Vet Company, 

Somerville, NJ.® 

6

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