Cattle Implants: What Are They And Should You Use Them?

Cattle implants are growth-promoting implants that stimulate and supplement the growth rate and efficiency of weight gain in beef cattle bred for slaughter. Both moral and health issues arise from the use of implants, and they should only be used to increase profits on beef cattle farms. 

Implants contain natural or synthetic compounds that mimic the behavior of their naturally-occurring equivalents in the cow.

The implants work by increasing circulating levels of these compounds cattle produce naturally. The compounds control biological functions that influence growth and feed efficiency, such as how effectively they extract nutrients from their feed.

In short, the increase in average daily weight gain (ADG) and the ability to process feed more efficiently lowers demands for farming resources, thereby reducing environmental impact.

Why Use Implants in the First Place?

Farmers use implants on their cattle mainly to reduce feed bills. As most annual expenses go on feeding cattle, it’s appealing to find ways in reducing the amount of food a cow needs to fatten up.

Having a steer or heifer reach a weight suitable for slaughter or sale sooner is also very appealing. After all, cattle raising is treated by many as a serious business.

Ethics and the moral high ground usually take a back seat in this kind of decision-making, especially if science suggests no harm to humans who eat meat from implanted cattle.

The Contents of an Implant

The compounds found in implants are androgens, progestins, and estrogens.

The main ingredients of estrogen implants are zeranol, estradiol 17-beta, and estradiol benzoate. Implanted estrogen copies the functions of naturally-produced estrogen.

Androgens imitate the behavior of naturally produced testosterone. The primary constituents of androgen implants are trenbolone acetate (TBA) and testosterone propionate.

Synthetic progesterone is also present in implants, but it has less effect on the cow than other hormone analogs. Hormone analogs act like endogenous (naturally produced) hormones when the analog–receptor complex in the target cell replicates the behavior of the hormone–receptor complex.

Insertion of the Implant

The growth implant looks like a tiny pellet or a large grain of rice. You place the implant into a syringe-like device called an “applicator” or “implant gun”, to which you attach a large diameter needle.

veterinarian performing cattle implant
Veterinarians always administer cattle implants in the middle of the ear

This needle delivers the implant into the skin on the exterior of the ear, right in the center section. The ear is the only scientifically-approved area on the cow for growth-implant application. The exact location is also critical because The Food and Drug Administration (FDA) no longer permits implant insertion at the base of the ear.

However, there are other reasons the ear is so suitable:

  1. The ear is easy to reach and is classed as offal, i.e., one of the few pieces of the cow not used in meat production or processing.
  2. If the injection was in the rump or the flank, it would be close to some of the choicest cuts on the cow and could taint their flavor, rendering them unsellable as premium products.
  3. Any implant program must have a facility to have the animal adequately restrained during insertion. As the ears protrude at a comfortable working height from the cattle restraining mechanism, they are the obvious choice for the application.
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A rigorously clean implant strategy is imperative. You must use a sterile needle and ensure the puncture point is clean. Poisonous secretions from abscesses can render the implant ineffective.

Once inside the ear, the implant will then release its particular hormone over its allotted time.

Wait at least a month after birth before administering the implant to the animal. Thirty days is what the label on a bottle of Ralgro® recommends, while Component® EC with Tylan® and Synovex® advise waiting 45 days.

Effects on Cattle

Weight gain is around 20% greater in heifers than in steers, so implanting heifers you have reared is very beneficial. Implanted calves that are nursing and destined to be beef cattle can achieve a 4 to 6 percent greater weaning weight.

Statistics suggest that calves with implants demonstrate an average daily weight gain of 10% to 20% more than calves without them. They also process food more efficiently, meaning a farmer can reduce their feed intake by between 5% and 10%.

Some commercially available implants like Encore®, Compudose®, or Ralgro® demonstrate single hormone activity with only estrogenic analogs.

The U.S. Food and Drug Administration, the U.S. Food and Agriculture Organization, and even the World Health Organization have reported that using implants in beef production poses no safety risk to consumers.

Six Hormones Used In Beef Production

U.S. agricultural administration has approved six hormones for usage in beef production.

Naturally occurringSynthetic chemicals
EstradiolTrenbolone acetate
Testosteronemelengestrol acetate

The FDA maintain a watchful eye on hormone implant production, usage, and safety, while both the The Food Safety Inspection Service of the U.S. Department of Agriculture are constantly analyzing synthetic hormone levels in beef.

Significant implant side-effects from increased estrogen compounds are prolapses of the vagina and rectum. Phytoestrogens present in the compound could cause these effects, as could user error when placing the implant due to poor technique or carrying out implantation at the wrong time.

Levels of Estrogen in Beef

Beef produced from cattle with hormone implants does contain higher levels of estrogen.

However, let’s compare these with other popular foods:

Beef from a non-implanted steer0.28 nanograms (ng) of estrogenic activity per 1 oz serving (a typical 14 oz steak would contain 3.92 ng of estrogen)
Beef from an implanted steer0.4 ng of estrogenic activity per 1 oz serving (a typical 14 oz steak would contain 5.6 ng of estrogen)
Eggs31.3 ng of estrogenic activity per 1 oz serving (a typical egg weighs 2 oz)
Tofu6.4 million ng of estrogenic activity per 1 oz serving

To give the figures above a little more context, a healthy non-pregnant female produces approximately 500,000 ng of estrogen each day on average, while an adult male makes about 135,000 ng.

Saying estrogen levels in hormone-implanted beef can be dangerous is, therefore, a little misleading.

Usage Can Vary By Region

Implants have long been a feature in beef cattle production, dating back to 1957.

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The cattle feed and stocker sections of the beef market have widely embraced their use, with nearly 95 percent of steers and heifers receiving at least one implant during their finishing period, according to a feedlot survey carried out by the USDA in the early 2010s. However, Cow-calf operators do not use them anywhere as frequently.

Use does vary by region as well. In the Southern Great Plains region, nearly 80 percent of farmers from Texas and Kansas confirmed they used implants in their stocker calves. In comparison, it was nearer 60 percent in Oklahoma.

However, cow-calf producers reported a much lower percentage of implantation in all of these areas.

How Implants Influence Beef Cattle Weight Gain

Nursing Calves

Nursing calves typically weigh under 400 lb, so their implants contain smaller amounts of active ingredients than those used for older cattle.

Farmers will generally administer these implants in the first two to four months of the calf’s birth. The average weight gain among implanted steer calves is around 1.6 oz per day. Heifers will fatten a little more slowly.

Reports suggest that progesterone/estradiol benzoate and zeranol implants outperform ones containing estradiol 17-beta.

To Castrate or Not to Castrate

Implants can cause complications with scrotum development, so castration of bull calves bred for beef should ideally occur before they receive an implant. Bull calves intended for breeding should never receive an implant.

Bull calves are often left intact until weaning. Popular belief is that the testicles produce hormones, leading to increased mass when the calf has finished suckling.

However, there is evidence that castrated calves with implants have an ADG superior or at least equivalent to intact ones. A further incentive is that castration at an early age is less stressful for the calf. If the animal is castrated when weaning, it can affect weight gain and the calf’s ability to combat diseases.

Market prices reflect this in that steers will bring up to US$10 more per hundredweight.

To sum up, if you wish to obtain the highest market value for your weaned male cattle, use an implant designed for suckling calves and castrate after two months and before four months.

Replacement Heifers

A replacement heifer is usually one descended from stock with excellent calving characteristics. A farmer will often buy one because raising one of their own calves to a stage where the replacement is already at is exceptionally costly and somewhat risky.

Research suggests that heifer calves used for breeding can safely receive one implant between reaching 45 days and weaning without suffering problems with impregnation or birthing later in life. Applying the implant directly after birth or when already weaned had a detrimental effect on their ability to conceive.

Stocker heifers would be prime candidates for the application of an implant. However, on occasions, farmers can identify replacement heifers in their own herds, usually during weaning. These heifers should not receive an implant.

Reasons For Not Implanting a Replacement Heifer

One of the primary uses for hormones is on heifers used for beef production. Heifers lag behind steers in average daily weight gain and are not economically viable. One way to close the gap and make them useful to beef farmers is by injecting them with hormones.

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If a rancher uses implants on a potential replacement heifer, they should ensure that she is not mixing with bulls when in heat. Allowing her to mix with the bulls will distract her from feeding and consequently lose weight.

It is also not advisable if you decide you want to keep some of the heifers you have implants in for breeding instead of meat production.

Reproductive systems are very complicated. Introducing additional or synthetic compounds into the metabolism of a breeding cow could be risky, not to mention the behavioral change that exposure to hormones probably containing elements like testosterone might cause.

Stocker Calves 

A young cow that has finished weaning and grazed on grass or grain for about five months before going to a feedlot for finishing and slaughter is known as a stocker calf. Implanted stockers can show a higher ADG of 0.2 to 0.25 lb or between 10 and 15% daily compared to non-implanted calves.

“Payout” is the length of time the implant is effective. Payout durations can differ quite significantly. Manufacturers estimate that Ralgro®, for example, is effective for 75 days while Compudose® can last for 200 days.

Stocker implant payout periods are typically between 80 and 120 days. However, some products on the market report an even longer effective time span. With long grazing seasons, farmers should decide between using implants designed for more extended payouts or using a second implant part of the way through.

Reimplanting has proved to be an effective way of increasing ADG, providing an approximate five percent increase in weight gain over the second payout. The benefits stocker cattle derive from implants depend on their gender, weight, propensity for ADG, quality, the quantity of feed and forage, supplements, and environment.

According to reports, implanted stockers fed on supplements and ionophores (ionophores aid propionate production in cattle leading to greater feed efficiency) have a 100 percent additive response. When given a diet of supplements and ionophores, these steers demonstrated a daily weight gain of around 0.5 lb, meaning an improved net return of over US$40 per animal.


There are three main phases in the development of beef cattle:

  1. The cow-calf phase, where the infant cow suckles the dam – 9 to 10 months
  2. The stocker or backgrounding phase, which begins after weaning is over. Here, the animal grazes on pasture and supplemental feed – 4 to 6 months
  3. The finishing phase or the final production phase. This period involves intensive feeding on “feedlots” to prepare the cattle for slaughter or market – 4 to 6 months.

An intensive feedlot management program of implanted cattle can mean a 20 percent increase in ADG and an improvement in feed efficiency of over 10 percent.

When farmers combined implants with ionophores and feed-grade antibiotics, feed efficiency grew to over 20 percent, final hot-carcass weights improved by nearly 90 lb, and ribeye areas increased in size. Skeletal maturity means USDA quality grades for implanted beef are also higher.

However, there was a decrease in marbling, reducing the grading of beef by nearly 25 percent. The larger size of the ribeye does somewhat offset the fat content reduction.

Scientists have also advocated using polymer-coated implants to avoid a bias for higher doses of compounds earlier in the implant payout. The coating allows a more controlled dosage over the practical life of the implant.

High-quality nutrition will also allow the fat reserves to build up and provide the basis for the appropriate amount of marbling to form.

List of Implants and Compounds

At a return on investment of up to US$15 for every US$1 spent on stocker calves, implants are perhaps the most profitable item on which a cattle farm can spend money. Used wisely, they can save a beef farmer up to seven percent in production costs.

Here are some of the most common implants and compounds:

Estradiol BenzoateExogenous 17β-estradiol and estradiol benzoate have been used in cattle to terminate pregnancies. It also induces lactation in cattle.
The estrogen in Compudose® increases weight gain in suckling and stocker steers. It improves feed efficiency and weight gain in feedlot steers and heifers.
ProgesteroneProgesterone is a naturally occurring steroid hormone.
Ralgro® or zeranolRalgro® or zeranol (by Merck Animal Health) is an anabolic agent that increases daily weight gain and feed efficiency of weaned beef calves, stocker cattle, feedlot steers, and heifers. Ralgo® improves weight gain in suckling beef calves.
Revalor® HRevalor® H increases weight gain and improves feed efficiency in feedlot heifers. It is a slow-release growth promoter that augments lean muscle without an increase in fat deposits. There is an improvement in feed conversion.
Synovex® CSynovex C can increase weight gain in suckling steers and heifers of up to 400 lb before weaning and feedlot steers over 400 lb.
Synovex Plus®Synovex Plus® is an implant designed for feedlot steers and heifers. It provides an increased rate of weight gain and improved feed efficiency in steers and heifers fed in confinement for slaughter.
Trenbolone AcetateTrenbolone acetate is an androgen and anabolic steroid that increases muscle growth in cattle.
ZoetisZoetis Inc is an American drug company and is the world’s largest producer of medicine and vaccinations for livestock. The company used to be a subsidiary of Pfizer but is now completely independent.

Organic farming regulations will not generally allow the use of implants. The higher prices customers pay for organically-farmed meat can offset the highest production costs, but this is generally not the case.


Adam has always had a fascination with farmyard animals, no doubt sparked by the farm in Devon he used to visit every summer when he was a young pup. He became close friends with the farmer’s children, two of which were about his age, and they allowed him to help out with cattle milking, herding and tagging. Being a fondly magical experience, he recently jumped at the opportunity to help the team at Cow Care Taker.

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