Study on cattle implants....

LM6000

Found this whilst looking for more info. on tren.
Not exactly ground breaking but I thought it was a good read, I particularly like the conclusion....

Beef Cattle Implant Update



Dee Griffin, DVM, MS, Extension Veterinarian


This guide discusses the mechanism of action and use strategies for growth promoting implants, including expected responses and cost analysis. (Griffin revision 2004)


Introduction

Growth promoting implants have been used extensively in beef production for over 30 years. Significant changes in implants and implanting strategies have occurred. Prior to 1987 available implants were estrogenic agents which metabolically improve nutrient use to enhance muscle deposition. These products improved feed efficiency five to 10 percent and daily gains from five to 15 percent. In 1987, the anabolic (tissue building) agent, trenbolone acetate was approved for use in growth promoting implants. This anabolic compound had an additive effect with existing estrogenic implants. The anabolic implant enhanced muscle growth and added an additional two to three percent to the feed efficiency and three to five percent to the daily gains. The financial return on implant investment varies, but only in rare situations do implants return less than $5 dollars per dollar spent. Implants are available for all cattle except calves less than 45 days of age and most breeding cattle. Proper scheduling and use of implants should return in excess of $10 per dollar spent.

Today implants are becoming designer products with varied dose and combinations of estrogenic and/or androgenic agents. While implants tend to be most effective in feedyards, implanting strategies have been effectively applied to other beef productions situations. The growth promoting implants approved for use in the United States are extremely safe. They are safe not only for the cattle, but for the producers who use the products and for the consumers of the beef produced from implanted cattle. There is no required withdrawal time for slaughter for any of the approved implants available in the United States.


Mechanism of Action

Cattle must have adequate nutrition before implants can positively influence feed efficiency and gain. The greatest response to implants tends to be observed in older cattle, near peak periods of lean tissue depositition. Typically these would be yearling cattle consuming high levels of quality high energy feed.

Estrogenic implants increase the circulating levels of somatotropin (ST) and insulin-like growth factor-1 (IGF-1). Both of these substances are produced by the animal and have a marked effect on how nutrients are used by the animal to produce muscle, bone, and fat. The approved anabolic agent, trenbolone acetate (TBA) does not seem to stimulate the production of ST, but it does significantly increase the circulating levels of IGF-1 and decreases the normal loss of muscle tissue in sedentary animals. The implant response is associated with nutrients available and the level of implant growth promotant circulating in the animal.

When growth promoting implants are first placed in the animal there is a rapid release of hormone from the implant. The level of growth promotant being released from the implant will begin to fall after a few days but will remain above the threshold level for effective growth stimulation for months. The length of time the growth promotant remains above threshold will depend on the pharmaceutical design of the implant and the quality of technique used when administering the implant. Re-implanting, the administration of a second implant, is usually scheduled to coincide with the declining level of circulating implant growth promotant but always above threshold. The optimum re-implant time is referred to as the re-implant window. For maximum benefit, it is important to maintain the level of implant growth promotant above threshold throughout the ownership of the stocker or feeder animal. The length of time an implant releases growth promotant above threshold or payout, varies between implants (Table 1). The rate of gain improvements appear to follow the declining level of growth promotant released from an implant. Therefore, the highest rates of gain can be expected during the first part of the payout period.

Because implant growth promotants interact with the production of hormones produced by the animal, the implants have not been recommended or approved for use in breeding cattle or calves less than 45 days of age.




Table 1. Available Implants
Name Estrogen
(mg/implant) Progesterone
(mg/implant) Anabolic
(mg/implant) Target
Cattle Re-implant
Window Estimated
Payout
Ralgro 36 mg
zeranola Calves/stocker/feeders
over 45 days of age 45 - 70
days 70 - 100
days
Synovex-C 10 mg
E2 benzoateb 100 mg
progestrone Calves between 45 days of age and weaning 45 - 90
days 100 - 140
days
Calfoid 10 mg
E2 benzoateb 100 mg
progestrone Calves between 45 days of age and weaning 45 - 90
days 100 - 140
days
Revalor-G 8 mg
E2 -17bc 40 mg
trenbolone acetated Pastured
stocker & feeder steers 120
days 100 - 140
days
Magnum 72 mg
zeranol a Weaned
stocker & feeder cattle 70 - 100
days 100 - 120
days
Compudose 24 mg
E2 -17b c Calves/stocker/feeders
over 45 days of age 140 - 170
days 170 - 200
days
Duralease 20 mg
E2 -17b c Feeders
over 45 days of age 70 - 100
days 100 - 140
days
Encore 43.7 mg
E2 -17b c Calves/stocker/feeders
over 45 days of age 280 - 340
days 300 - 400
days
Synovex-S 20 mg
E2 benzoateb 200 mg
progesterone Weaned
stocker & feeder steers 70 - 100
days 100 - 140
days
Implus-S 20 mg
E2 benzoateb 200 mg
progesterone Weaned
stocker & feeder steers 70 - 100
days 100 - 140
days
Revalor-IS 16 mg
E2 -17bc 80 mg
trenbolone acetated Weaned
stocker & feeder steers 60 - 100
days 100 - 140
days
Revalor-IH 8 mg
E2 -17bc 80 mg
trenbolone acetated Weaned
stocker & feeder heifers 60 - 100
days 100 - 140
days
Synovex Choice 14 mg
E2 -17bc 100 mg
trenbolone acetated Weaned
stocker & feeder steers 60 - 100
days 100 - 140
days
Revalor-S 24 mg
E2 -17bc 120 mg
trenbolone acetated Weaned
stocker & feeder steers 90 - 100
days 100 - 140
days
Finaplix-S 140 mg
trenbolone acetated Weaned
stocker & feeder steers 70 - 100
days 60 - 100
days
Synovex-H 20 mg
E2 benzoateb 200 mg
Testosterone Weaned
stocker & feeder heifers 70 - 100
days 100 - 140
days
Implus-H 20 mg
E2 benzoateb 200 mg testosterone Weaned
stocker & feeder heifers 70 - 100
days 100 - 140
days
Revalor-H 14 mg
E2 -17bc 140 mg
trenbolone acetated Weaned
stocker & feeder heifers 90 - 100
days 100 - 140
days
Finaplix-H 200 mg
trenbolone acetated Weaned
stocker & feeder heifers 70 - 100
days 60 - 100
days
Synovex Plus 28 mg
E2 benzoateb 200 mg
trenbolone acetated Weaned
stocker & feeder steers 90 - 100
days 100 - 140
days
Revalor 200 Plus 20 mg
E2 benzoateb 200 mg
trenbolone acetated Weaned
stocker & feeder cattle 90 - 100
days 100 - 140
days


a zeranol contains 30 to 33 percent the estrogenic activity of Estradiol-17b (E2 -17b).
b E2 benzoate is approximately 72.5 percent the estrogenic activity of Estradiol-17b (E2 -17b).
c Estradiol -17b
d Trenbolone acetate is often abreviated as TBA

Ralgro and Magnum are trademarks of Mallinckrodt Veterinary, Inc.
Synovex-C, -S, -H, Choice and Plus are trademarks of Fort Dodge Animal Health.
Finaplix-S, -H, Revalor-S, -H, -G, -IS and -IH are trademarks of Intervet (Hoechst-Roussel Agri-Vet) Company.
Calfoid, Implus-S, and -H are trademarks of The Upjohn Company.
Compudose & Encore are trademarks of VetLife.
Duralease is trademark of Merial.


Implant Performance

The estrogenic implants approved for use in suckling calves will improve weaning weights three to five percent. Similar performance improvements can be seen in pastured stocker cattle when the base gain is above one and a half pounds per day.
Previously implanted cattle are of concern to cattle buyers who prey on the compensatory gain potential of cattle. Producers must receive a premium equivalent to the loss of production to consider not implanting suckling calves or stocker cattle. There are numerous outstanding feedyards willing to accept previously implanted cattle.

In feeder cattle, estrogenic growth promoting implants improve feed efficiency and gain five to 15 percent. Implants which include trenbolone acetate can provide an additional three to five percent improvement in feed efficiency and daily gain. A properly designed re-implant program can sustain implant associated improved performance beyond the payout that would be expected for a single implant.

For estrogenic implants used in yearling cattle fed typical Nebraska feedlot rations, a $5 return above the cost of the implant can be expected for each $1 price of a bushel of corn. Adding TBA to an estrogen implant system will return an additional $2 above the cost of the implant for each $1 price of a bushel of corn. For example, if corn cost $3 per bushel an estrogenic implant would return approximately $15. Implants containing TBA would return approximately $21 when used in cattle fed $3 corn.

While cull cows are not typical feeders, limited data suggest they respond to implants at or above the level of younger feeder animals, especially to TBA. Most cull cows are not fed long enough to consider a re-implanting program.


Implant Use

Regulations governing the use of implants are set by the U.S. Food and Drug Administration (FDA). Always read and follow the manufacturer’s directions as approved by the FDA-CVM before implanting any cattle.


Figure 1. Approved Location for Implant Administration.



The only approved location for implant administration is the middle third of the back side of the ear. All implants must be located subcutaneously within this area (Figure 1). Try to avoid blood vessels. If part of the ear has been lost because of frostbite or injury, the implant should be placed in the last half of the ear. This should place the implant outside the cartilage ring at the base of the ear. Implants should never be placed in locations other than the ear.

Implanting technique defects are a serious economic concern because of suspected associated performance loss. Defects of concern include abscesses, expelled implants, cartilage embedment, crushed pellets, missing pellets, and bunched pellets. Identification of these defects can be hard to determine. Generally abscesses will be enlarged and will feel doughy. If the abscess ruptures, the implant will be expelled leaving a very small ring of scar tissue. Some implant sites will accumulate fluid that is not associated with an infection and will not seem to be associated with implanting technique. Cartilage embedment should be suspected when the implant feels firmly attached to the deeper tissues of the ear or the roughened edge of the implant cannot be felt. While no published data is available to validate an associated economic loss from these defects, unpublished data from work conducted at University of Nebraska -Great Plains Veterinary Educational Center during the summer of 1996 suggests misplaced and abscessed implants found at the packing plant were associated with 0.17lb/day reduction in carcass gain in cattle fed 150 days when compared to cattle with normal implants. Common sense suggests better performance could be expected in cattle free of implant defects.

The loss of implants before payout can be avoided if the implants are properly located in a dry ear with a clean implanting needle. If the ear is wet it should be dried before implanting. If the ear is covered with wet manure or mud, the filth should be scraped or washed off and the ear dried. The needle should be cleaned between each animal with a diluted disinfectant. If the needle slips over the surface of the ear it should be cleaned before continuing. The tissue irritation caused by an undiluted disinfectant can cause the expulsion of an implant or the formation of scar tissue which could interfere with the effective release of growth promotant from the implant. Care should be taken when selecting an implant needle cleaning solution. One ounce of chlorhexidine, the blue disinfectant, per gallon of water is an effective implant needle cleaning solution while alcohol is not. Some feedyards coat the cleaned implanting needle with an approved, non-irritating antibiotic between animals as an additional safeguard to help prevent implant site infections. Visit with your veterinarian about the selection, dilution and use of a disinfectant.

Developing a light touch and slightly rotating the needle when implanting is the best defense against cartilage embedment. A properly placed implant will be slightly moveable.

Missing or bunching of implant pellets can be avoided by carefully restraining the animal and slowly withdrawing the implant needle as the implant is being administered. Implant guns and needles are available from the companies that manufacture growth promoting implants. All implants can be effectively administered with the implanting gun designed for the associated implant. It is important to visually inspect and physically palpate the implant site after the implant is administered to ensure the implant is properly placed and all the pellets in the pelleted implants are properly aligned. As part of the inspection, the implant needle opening should be closed by pressing down on the hole. Most of the problems with implant guns can be avoided by closely following the manufactures’ directions.

Implant restraint bars or plates have become common on processing chutes. They effectively hold the animal’s head still, making it much easier to properly place the implant. However, implant restraint bars and plates will cause the loss of four to six inches of exposed neck available for injection making it more difficult to properly give neck injections. Because injections site damage in the rump and round is a serious concern of the beef industry, we recommend giving all antibiotic and vaccine injections in the neck and therefore do not recommend the use of implant restraint bars or plates. If cattle are caught properly, just behind the ears in an un-modified head gate, implanting restraint bars or plates are not needed to properly place implants.

Routine inspection of implant and vaccine sites should be done every time animals are handled through a chute and at periodic quality audits performed at packing houses. A practical and consistent inspection can be accomplished on each animal that enters the hospital.


Other Considerations

Implanting heifers intended to enter the breeding herd is controversial. Mixed results from research trials suggest detailed management considerations must be adhered to before considering an implant program for replacement heifers. Highlights of these considerations include selecting an implant approved for use in replacement heifers, providing adequate nutrition for growth and leaving adequate time between implanting and breeding. Implanting replacement breeding bull calves is not approved or recommended.


Implanting Strategies

It is important to implant cattle as soon as possible. In suckling calves, the traditional branding time in Nebraska provides an excellent opportunity to implant and vaccinate most of the calves in the herd. Prior to bull turn out, the preferred procedures include vaccination with subcutaneously administered modified live four way viral and clostridial vaccines and implanting calves older than 45 days of age with a product designed for suckling calves. It is important not to implant replacement heifers or bull calves intended to be kept as breeding bulls unless strict adherence to manufactures directions are followed.

Calves at weaning not intended for breeding should be implanted again with a feeder implant. The feeder implant can be either an estrogenic implant or a combination estrogenic - trenbolone implant. It appears to be important to finish the feeding period with the most potent implant selected in the implanting program (Table 2). Therefore, if a combination estrogenic - trenbolone implant is selected as the first implant, it should be used again in subsequent implantings. If an estrogenic implant without trenbolone is selected as the first implant, a similar product or an estrogenic - trenbolone implant can be selected for subsequent implanting.

Re-implant schedules should be developed to reflect the targeted finish date, the historic grade price spreads, the genetic potential of the cattle, and the feeding program available. From the projected finish date, re-implanting should be scheduled by back calculating the payout days of the last implant intended for use. For example, if 550 pound, medium to large frame weaned steer calves enter the feedyard the first of October, an estrogenic product such as Magnum, Synovex-S or Implus-S can be selected as the initial implant. If the cattle are projected to gain three pounds per day and be marketed at 1100 pounds, the estimated sale date would be the first two weeks of April. Back calculating the 120 day payout of a combination estrogenic - trenbolone implant from the middle of April, re-implanting would be scheduled for the mid to late December.

Maintaining implanting schedules can be very difficult, but tremendous performance advantages can be achieved if properly managed. If you have any questions, seek the advise of a qualified feedlot nutritionist or veterinarian.

Never stack implants by re-implanting before the preceding implant has met the re-implant window. To do other wise will lead to severe side effects such as prolapses and decrease in gain and / or efficiency performance.

Table 2. Implant Relative Potency and Payout Rank
Name Hormonal Activity Relative Potency Optimum Payout Period in days
Ralgro Estrogenab Low 60 – 90 days
Synovex-C Estrogenab Low 60 – 90 days
Calfoid Estrogenab Low 60 – 90 days
Duralease Estrogenab Moderate 80 – 120 days
Magnum Estrogenab Moderate 80 – 120 days
Synovex-S/H Estrogenab Moderate 80 – 120 days
Implus-S/H Estrogenab Moderate 80 – 120 days
Finaplix-S/H Androgenab Moderate 60 – 80 days
Revalor-IS/IH Andorgena b Estrogenab Moderate 90 –120 days
Synovex Choice Andorgena b Estrogenab Moderate 120 –140 days
Finaplix-S/H Andorgena b Estrogenab High 90 – 110 days
Revalor-S/H Andorgenab Estrogenab High 90 – 120 days
Synovex Plus Andorgenab Estrogenab High 90 – 120 days



a See notations for Table 1. b Androgen and Estrogen is denoted as A and E in the Figure 2.


Figure 2 Implant Program Relative To Days From The Packer To Achieve A Choice Finish End Point (CFEP)

Note: The diagram is interpreted bottom to top. Each column represents an individual example of the length of days the animal will be finished – Days On Feed (DOF). All protocols should be designed so that the implant has been use up by the time the animal is scheduled to go to the packer. NEVER, give an implant before any previous implant has met the re-implant window.
Days from the packer 250 DOF
Example 150 DOF Example A 150 DOF example B 120 DOF example A 120 DOF example B 90 DOF Example A 90 DOF Example B
Day 0 ? ? ? ? ? ? ?
? ? ? ? ? ? ?
? ? ? ? ? ? ?
Day 70 ? ? ? ? HP ? ?
Day 80 ? ? HP HP ? ? ?
Day 90 ? ? ? ? ? MP HP
Day 100 HP HP ? ? ?
? ? ? ? ?
Day 120 ? ? ? LP MP
? ? ?
? ? ?
Day 150 ? LP MP
?
? LP = Low Potency (E)
Day 190 MP MP = Moderate Potency (E)
? HP = High Potency (E + A)
?
Day 250 LP or MP



Ration Considerations

Although no special ration considerations are needed for maximal implant performance, it is important to feed a balanced high quality ration. All approved feed additives, used in an approved manner, are appropriate to consider in a feeding program for implanted cattle. Performance improvements associated with approved feed medications are additive to the expected performance improvements from implants.


Side Effects

Heavy carcass weight can be a problem when feeding large frame exotic long yearlings. Typically, implanted cattle will be heavier when finished to the same quality grade as non-implanted cattle. Weight discounts in the magnitude of 15 percent of the carcass value can be applied to carcasses that weight over 950 pounds or live cattle that weight over 1500 pounds. This problem can be minimized if cattle start on feed at a lighter weight, only estrogenic implants are used or the finishing grade is targeted to achieve the select instead of choice grade.

Poor yield grades have been reported in heifers implanted with combination estrogenic - trenbolone implants and concurrently fed the feed additive melengestrerol acetate (MGA). These observations were made in studies designed to evaluate the benefits of a combination implant. It is likely the heifers were over fed. It is important in any feedlot management program to evaluate cattle near their target finishing date and move the cattle to the packer as soon as the cattle reach the most economically appropriate degree of finish.

Poor quality grades can be a problem if implanting schedules are not properly designed to match the age, weight, genetics, and nutritional management of the cattle. It is always important to consider the historic quality grade price spreads at the targeted finishing date.
An increase in the buller rate has been reported with the use of some implants. Crushing implants has also been blamed on the increased buller rate in some groups of implanted animals. With the modern implanting tools available today this problem seems unlikely. The effects of climatic changes, ambient temperature, animal handling, commingling, feed stuffs containing fungal or plant estrogens, and implant technique seem more likely to play a role in these observations.

Vaginal and rectal prolapses have been reported as an implant side effect. If hormones are involved in these occurrences, it is possible additional estrogenic compounds from the feed are involved. These compounds could come from feed molds or from some classes of feeds such as legumes containing plant estrogens. Other suspected causes include improper implanting technique or improper inplant scheduling.

High tailheads, sunken loins, udder development, and heavy hide weights have also been reported as side effects. These problems are generally rare or have minor economic significance when compared to the performance benefit realized from the use of implants.


Conclusions

The use of growth promoting implants is one of the most cost effective methods of enhancing cattle gain and efficiency of gain. Implants are most effective when used in pre- and post-weaned cattle and finished or destined to be finished in the feedlot. In general, implants enhance protein deposition while diminishing fat accretion. Properly designed implant programs should take into account animal age, sex, weight, breed and market objectives. Meat and animal products from cattle implanted with growth promotants are as safe and acceptable as comparable products derived from non-implanted cattle.