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Lawton Stewart¹

• Introduction
• Implants
• Using Implants
• Nursing Calf Performance
• Stocker Calf Performance
• Feedlot Calf Performance
• Implanting Bulls
• Lifetime Effects of Implanting
• Implanting Replacement Heifers
• Side Effects
• Implant Safety
• Summary
• Literature Cited

Introduction

Implanting nursing calves with a growth stimulant is one of the most economically justifiable practices available in the beef industry. Implants have been shown to increase weaning weights of nursing calves in hundreds of research trials. Stocker and feedlot calves exhibit even greater responses than nursing calves. Implanting returns more revenue per dollar invested than any other management practice.

Despite being approved for more than 50 years, only 33 percent of cow/calf producers nationwide use growth-promoting implants. Unless calves are marketed to a program that prohibits the use of implants, nursing calves intended for sale should be implanted prior to weaning.

Although technologies are constantly being developed to reduce the costs of beef production, cow/calf producers are often reluctant to use implants. Therefore, it is critical that manufacturers invest money into research and product development to benefit cow/calf producers.

Implants

Implants are small pellets that contain a growth stimulant that is slowly released over a period of time. Implants work by increasing circulating levels of somatotropin and insulin-like growth-factor 1. This causes an increase in the secretion of growth hormone, which increases muscle growth.

Many implant products are available for use in nursing calves, stocker calves and feedlot calves. Most implants are specifically designed for a certain sex, age or stage of production. Always read the product label and follow the manufacturer’s recommendations prior to implant use.

Implants that are approved for use in beef cattle are shown in Table 1. Of the hormones used in beef cattle implants, three are naturally occurring (estradiol, progesterone and testosterone) and two are synthetics (zeranol and trenbolone acetate). Estradiol, progesterone and zeranol are estrogenic, whereas testosterone and trenbolone acetate are androgenic. Estrogenic refers to hormones affecting female characteristics and androgenic refers to hormones affecting male characteristics. Zeranol mimics estradiol and trenbolone acetate mimics testosterone. Table 2 lists the production phase and age approvals for each implant.

Using Implants

The U.S. Food and Drug Administration (FDA) approves and regulates the use of all growth-promoting implants. The only FDA-approved location for placement of an implant is the middle third on the back side of the ear, between the skin and the cartilage.

Optimal response to implants depends on sanitation and proper implanting techniques. Improper sanitation and technique may cause defects including abscesses, lost implants, improper placement, crushed pellets and missing pellets. Implant manufacturers market an implant gun that is specific for each implant. The implant and implant gun should be made by the same manufacturer to keep defects to a minimum. Take the following steps to minimize implant failures:

1. Restrain the animal’s head in a head gate to restrict movement. Catch the animal just behind the ears. If the animal will not be calm, use a halter for the safety of both the animal and implant technician. If the animal is moving, the needle can easily come out of the ear and the implant will be deposited on the ground.
2. Check the needle to make sure it is tightly secured to the implant gun; replace the needle when it becomes dull or damaged. Clean the needle with a disinfectant between each implant. Some implants are coated with antibiotic, which can decrease the risk of infection.
3. Clean the ear of any mud or manure and disinfect it before implanting. A commonly used disinfectant is Nolvasan® (chlorhexixine acetate), which should be mixed at 1 ounce per gallon of water.
4. Place the implant in the center one-third of the ear. To prevent crushing the pellets, slowly withdraw the needle as the implant is being administered to allow space for the implant pellets. Close the incision made by the needle by pressing down on the opening.

Examine the ear to make sure the implant was properly placed. The implant should be slightly movable if placed between the skin and cartilage. The implant will not be absorbed if it is placed in the cartilage where there is no blood flow. Avoid placing the implant in the blood vessel because the absorption rate will be higher, and the implant will be effective for a shorter period of time. Be patient and make sure the implant is correctly placed. Each implant that is improperly placed can mean $15 to $20 of lost income.

^aDo not implant heifers prior to 30 days of age.
^bDo not implant heifers prior to 45 days of age.

Nursing Calf Performance

Calves (steers and cull heifers) that are destined for finishing and sale to a terminal market should be implanted. Heifers intended for breeding require specific implant recommendations to avoid reproductive failures, which are discussed in a later section of this publication. Several research trials have shown that implanting nursing beef calves once will improve daily gains from birth to weaning by four to six percent. Growth response to implants is about 20 percent greater in heifers than steers.

Implanting a nursing calf once will increase weaning weight by approximately 15 to 30 pounds. Most calves are not weaned, however, until seven to eight months of age, and the majority of implants lose effectiveness within 120 days of implanting. If calves are implanted at birth or before two months of age, the implant will lose effectiveness three to four months before weaning. Research has shown that re-implanting nursing calves increased weight gains by 1 to