Cattle Today

Cattle Today

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Dr. Steve Blezinger

In the last issue we began a discussion of implanting and the effectiveness of this management tool. As we saw, there are numerous products on the market based on a variety of chemical combinations and varying in the time they are effective. In the conclusion to this series we will discuss product use, some implanting strategies which can be used to maximize effectiveness and finally, safety issues which are of great concern to the consumer and subsequently to the cattleman.

Implant Use

Regulations governing the use of implants are set by the U.S. Food and Drug Administration (FDA). It is important that you always read and follow the manufacturer's directions before implanting any cattle.

The only approved location for implant administration is the middle third of the back side of the ear. All implants must be located within this area as shown in Figure 1. If part of the ear has been lost because of frost bite or injury, the implant should be placed in the last third 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 potential performance loss. The loss of implants before the end of the effective period 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. 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 movable. 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 implant 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 manufacturer's directions.

Implanting Replacement Animals

Implanting heifers intended to enter the breeding herd is controversial. The 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 practical. Normally, implantation occurs at the same time calfhood vaccinations are given and other processing such as castration and dehorning takes place. Research has shown that an average of 60 days of age works well. As noted above it is important not to implant replacement heifers and never implant bull calves intended to be kept for breeding purposes unless strict adherence to manufacturer's directions are followed.

Calves at weaning not intended for breeding should be implanted again with a more aggressive 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 as illustrated in Table 1.

Table 1. Implant Relative Potency
and Effective Period Rank





Period in Days

Ralgro® Low 60 - 90
Synovex C® Low 60 - 90
Calfoid® Low 60 - 90
Magnum® Moderate 80 - 120
Synovex-S/H® Moderate 80 - 120
Implus-S/H® Moderate 80 - 120
Finaplix-S/H® Moderate 60 - 90
w/ Syn/Imp/Ral* High 90 - 100
Revalor® High 90 - 120
Synovex Plus® High 90 - 120

* Combination implanting placing the first product in one ear and one of the others in the other ear. Adapted from Griffin and Mader, 1996

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 can be selected for subsequent implanting or an estrogenic-trenbolone implant may be selected.

Reimplant schedules should be developed to reflect the targeted sale or finish date, the historic grade price spreads, the genetic potential of the cattle, and the feeding program available. From the projected finish date, reimplanting should be scheduled by back calculating the effective of the last implant intended for use. Maximum response is seen in cattle that are continuously implanted throughout the production period.

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

Ration Considerations

It is generally thought that no special ration considerations are needed for maximal implant performance although it is important to feed a balanced high quality ration. Some research has shown, however that improved response has been observed in with the Androgen/Estrogen implants (Finaplix® combinations, Revalor®, Synovex Plus®) when rations are formulated with higher protein contents. 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

Some side effects have been occasionally noted through the extensive use of implants, although primarily in the finishing phase. These include:

1) Heavy carcass weight when feeding large frame exotic long yearlings.

2) Poor yield grades in heifers implanted with combination estrogenic-trenbolone implants and concurrently fed the feed additive melengestrerol acetate (MGA).

3) Poor quality grades if implanting schedules are not properly designed to match the age, weight, genetics, and nutritional management of the cattle.

4) An increase in the buller rate has been reported with the use of some implants.

5) Vaginal and rectal prolapses.

6) High tailheads, sunken loins, udder development, and heavy hide weights.

These problems are generally rare or have minor economic significance when compared to the performance benefit realized from the use of implants.

Food Safety

The FDA requires no withdrawl period before the slaughter of implanted cattle. McCollum (1998) reported that contrary to many articles in the popular press, beef from implanted cattle has only a very low level of hormonal (particularly estrogen) activity compared to other common foods. Table 2 below lists the estrogenic activity of several common foods. Likewise, the potential amount of estrogen consumed in beef is extremely low compared to that produced daily by the human body. To put this in perspective, if a person consumed 1 pound of beef per day from implanted cattle, the potential estrogen intake would be about 10 nanograms (a nanogram is equal to one billionth of a gram). By comparison, the daily estrogen production in the human body is about 100,000 nanograms for adult men, about 5,000,000 nanograms for non-pregnant women and about 40,000 nanograms for a prepuberal child. So based on these numbers we can see that the amount of estrogen which might be consumed by eating implanted meat is very small.

Table 2. Estrogenic Activity of Several Common Foods

Food Estrogenic Activity*

Soybean Oil 908,000
Cabbage 10,896
Wheat Germ 1,816
Peas 1,816
Eggs 15,890
Ice Cream 2,724
Milk 59
Beef from Pregnant Cow 636
Beef from Implanted Cattle 10
Beef from Non-implanted cattle 7

* nanograms per lb. of food. Adapted from Preston, 1997.


Using growth promoting implants is one of the most cost effective methods of enhancing cattle gain and efficiency of gain. 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 nonimplanted cattle and are lower in hormones of concern than many other commonly consumed foods.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs, Texas. he can be reached at P. O. Box 653 Sulphur Springs, TX 75483, by phone at (903) 885-7992 or by e-mail at


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