Growth Implants for Beef Cattle

Growth promoting implants have been available for many years in several forms. The two major classes of implants registered for use in Canada consist of either estrogenic compounds (estradiol benzoate, estradiol 17B, zeranol) or androgenic compounds (trenbolone acetate (TBA) in combination with estradiol benzoate or estradiol 17ß). It is important to understand which compound and which implant you are using, as it will affect implant strategies discussed later in this paper.

How Do Implants Work?

Implants work in conjunction with the natural hormones in the animal’s body resulting in increased weight gain, improved feed efficiency and leaner carcasses. This is done through the partitioning of nutrients to support more lean tissue or muscle growth. Estrogenic compounds stimulate the animal’s body to increase cell division resulting in increased muscle and skeletal growth rates. Androgenic compounds result in an increase in muscle mass by increasing protein synthesis and slowing the rate of muscle protein degradation.

Why Implant Cattle?

The result of implanting cattle is the production of a desirable product (lean meat) which takes less feed to produce in a shorter amount of time. It increases weight gain by 5% to 23% and feed efficiencies can improve 3% to 11%. The cost of the implants range from $2.00 to $6.00 and the increased gain can result in returns ranging from $5.00 to $10.00 for every dollar spent.

Implanting Techniques

Restraining the Animal Properly

Implanting is easier and safer if the animal is held in a squeeze chute with a head restraint. Restraint also minimizes errors in positioning of the implant.

Sanitization

Sanitization is critical. The ear should be clean, dry and the implant needle should be sharp and disinfected. Unsanitary conditions can result in abscesses that can wall off the implant and decrease absorption resulting in a loss of effectiveness.

Inserting the Implant

1. Familiarize yourself with the implant gun and ensure the gun is loaded properly.
2. Hold ear with one hand and insert the needle of the implant gun under the skin on the backside of the ear. The implant should be deposited in the middle third of the ear as shown in Figure 2.
3. Once the needle is in place under the skin hold your thumb over the area of insertion to hold the pellets in place when the needle is retracted (whether automatic or manual). Implanting too close to the head, crushing the pellets during implantation or implanting into a blood vessel results in rapid absorption of the pellets and contributes to side effects such as increased bulling in newly implanted animals and vaginal prolapse in heifers. Avoid implanting into the cartilage ribs, as this will decrease the absorption of the implant.
4. After implanting is complete, feel for the pellets under the skin of the ear to ensure the implant has been properly deposited.

Figure 2. Source: Beef Cattle Implant Update. Cooperative Extension, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln.

All of the growth implants listed in Table 1 are designed and approved for implantation in the ear only, which is not used in the human food system. Implanting elsewhere may be ineffective and result in condemnation of the carcass.

Table 1. Growth promotant implants registered for use in Canadian beef cattle

Source: 1999 Compendium of Veterinary Products.
Note: Z=zeranol; P=progesterone; EB=estradiol benzoate; T=testosterone propionate; TBA=trenbolone acetate; E17=estradiol 17b
^Heifer calves maintained for breeding proposes should not be reimplanted. Bull calves intended for breeding should not be implanted. Follow label directions regarding age and weight restriction and reimplanting.
^Schering-Plough Animal Health 1-888-873-0033
^Wyeth Animal Health 1-888-293-7781
^Elanco Animal Health 1-800-661-6801
^Intervet Canada Ltd. 1-800-668-6644

Implant Considerations

There are a number of important factors to consider when selecting and using implants. In general, most implants have a higher rate of release (60% to 70% of total implant potential) within the first 30 days following implantation. All implants are effective for a certain amount of time (or payout period) which is shown in Table 1. When using any implant ensure that label directions are carefully followed.

Age

There are a variety of products specifically formulated for calves, feeders or finishing cattle. All formulations result in improved efficiencies and must be used according to label directions and specified weight ranges. The terminal implants used in finishing cattle should not be used in replacement animals.

Sex

Some implants are gender-specific. Caution should be taken to match the correct implant with the sex of the animal.

Breed Type

There are two main groups of breed types: exotic and British. Typically the exotic breeds (ex, Charolais, Simmental) are genetically capable of gaining more quickly and have a tendency to be harder to finish, and therefore a less aggressive implant strategy may be considered. The British breeds (ex, Hereford, Angus) are typically easier to finish and a more aggressive implant strategy may be used, creating a larger framed carcass at point of finish.

Days on Feed or Pasture

Estradiol type implants will improve gains and efficiency on pasture, as long as pasture quality is adequate and stocking density is optimum to allow gains of at least 1.5 lbs per day. Implanted livestock will consume more forage, and therefore pasture management is critical. If cattle are to be placed on feed from the backgrounding period through to finishing, it may be necessary to use an estradiol type implant followed with an androgenic type of implant. If the cattle are only on feed for the finishing period, they may be implanted with an androgenic type. The androgenic type (TBA) implant is most effective when it is used in conjunction with animals receiving high-energy rations (more than 80% concentrate barley). Therefore, it is typically used as the "terminal" implant in the finishing phase in the feedlot.

Nutritional Program

Ensure rations are balanced for energy, protein, minerals and vitamins to obtain maximum efficiency from the implant.

Carcass Considerations

If feeding cattle through to finish and they are being sold on quality grade it may be necessary to leave cattle on feed ten to 15 days past the payout period when using an androgenic type of implant to allow for additional intramuscular fat (marble).

References:

Growth Implants for Beef Cattle. 2000. Alberta Feedlot Management Guide. 2nd ed.

Component Implants. Technical Reference Guide. Elanco Animal Health.

Growth Implant Strategies. 2000. Alberta Feedlot Management Guide. 2nd ed.

Beef Cattle Implant Update. July 1997. Cooperative Extension, Institute of Agriculture and Natural Resources, University of Nebraska-Lincoln. July 1997.