Cattle Today

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IMPLANT STRATEGIES

Dr. Steve Blezinger
Ph.D.

Many management practices have been developed over the years that significantly help performance and productivity in beef cattle. Of the various practices adopted by many operations one of the most effective, if not THE most effective is the use of growth implants in suckling calves, young growing cattle and finishing steers and heifers destined for slaughter. Over the next couple of issues we will discuss implants and their use and hopefully dispel some of the misinformation which exists in public perception.

Implants are small pellets or devices that are placed under the skin at the back of the ear. Each pellet contains a growth stimulant that is slowly released in to the blood circulation and is subsequently carried to the tissues. We'll discuss more of how implants actually work in a moment.

In a review by Griffin and Mader (1997) they discussed that growth promoting implants have been used extensively in beef production for over 30 years and over this time significant changes in implants and implanting strategies have occurred. Before 1987, available implants were estrogenic agents which metabolically enhanced nutrient use to enhance growth. These products improved feed efficiency 5-10 percent and daily gains from 5-15 percent. In 1987, the androgenic (tissue building) agent, trenbolone acetate, was approved for use in growth promoting implants. This compound had an additive effect with existing estrogenic implants. The androgenic 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 return on implant investment varies, but only in rare situations do implants return less than $5 per $1 spent and in most cases the typical return on investment is $10 per $1 spent. Implants are available for all cattle except calves less than 45 days old and most breeding cattle. 

Today, implants have become almost designer products with varied doses and combinations of estrogenic and/or androgenic agents. While implants tend to be most effective in feed yards, implanting strategies have been effectively applied to other beef production situations. A review by McCollum (1998) showed that implanting of suckling calves and stocker cattle offers one of the highest benefit to cost ratios of any management practice. Table 1 illustrates the implants currently available, manufacturing company, target animal, etc.

Table 1. Guidelines for Currently Approved Implants for Suckling Beef Calves and Stocker Cattle

Implant
Trade
Name

Marketing
Company


Active Ingredient(s)


Target Animal
Estimated
Effective
Period

Implus®-C or Calf-oid Upjohn Co. 100 mg progesterone
10 mg estradiol benzoate
Suckling beef calves up to 400lbs. Not for use in calves less
than 45 days old or calves intended for reproduction.
100-140 days
Compnent®-C VetLife, Inc. 100 mg progesterone
10 mg estradiol benzoate
Steer and Heifer calves to 400lbs.  Not for use in calves less than 45 days old or bull calves intended for reproduction. 100-140 days
Synovex®-C Fort Dodge Animal Health 100 mg progesterone
10 mg estradiol benzoate
Steer and Heifer calves to 400lbs.  Not for use in calves less than 45 days old or bull calves intended for reproduction. 100-140 days
Ralgro® Schering-Plough Animal Health 36 mg Zearanol Steer and Heifer calves; weaned steers and heifers; not for use in calves less than 30 days old or bull calves intended on reproduction. 70-100 days
Compudose® VetLife, Inc. 25.7 mg estradiol Suckling steers; weaned steers and heifers; not for replacement heifers. 170-200 days
Encore® VetLife, Inc. 43.9 mg estradiol Suckling steers; weaned steers and heifers; not for replacement heifers. 400 days
Compone®-H VetLife, Inc. 200 mg testosterone
20 mg estradiol benzoate
Heifers over 400lbs.
not replacement heifers
100-140 days
Compone®-S VetLife, Inc. 200 mg progesterone
20 mg estradiol benzoate
Steers over 400lbs.
100-140 days
Implus®-H UpJohn Co. 200 mg testosterone
20 mg estradiol benzoate
Heifers over 400lbs.
not replacement heifers
100-140 days
Implus®-S UpJohn Co. 200 mg progesterone
20 mg estradiol benzoate
Steers over 400lbs. 100-140 days
Synovex®-H Fort Dodge Animal Health 200 mg testosterone
20 mg estradiol benzoate
Heifers over 400lbs.
not replacement heifers
100-140 days
Synovex®-S Fort Dodge Animal Health 200 mg progesterone
20 mg estradiol benzoate
Steers over 400lbs. 100-140 days
Revalor®-G Animal Health Hoechst-Roussel 200 mg estradiol benzoate Steers over 400lbs. 100-140 days
From: F. T. McCollum 1998. Implanting Beef Calves and Stocker Cattle. TAEX Publ. L-2291

A number of other products of this nature also exist that are designed for use in finishing cattle which I did not include here.

How Do Implants Work?    

Remember there are no substitutes for good management and their are no “silver bullets” out there. 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 deposition. Typically these would be yearling cattle consuming high levels of high energy feed but a significant effect is also seen in suckling and grass cattle.

Estrogenic implants increase the circulating levels of somatotropin (ST) and insulin-like growth factor-1 (IGF-1). Both of these substances are hormone-like and naturally 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 androgenic agent, trenbolone acetate (TBA), does not seem to stimulate the production of ST, but 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 an effective growth stimulating level for a varying length of time depending on the design of the implant and the quality of technique used when administering the implant placement. The length of time an implant releases growth promotant at or above the effective level varies from approximately 75 days for Ralgro® to the manufacturer's estimated 200 days for Compudose®. Table 2 below lists the products available and the periods of time they are effective. This table also describes the types of activity (estrogenic, androgenic or both) each implant utilizes and the strength or intensity of effect. The improvements in rates of gain appear to follow the declining level of growth promotant released from an implant.

Table 2. Implant Relative Potency and Effective Period Rank
Name  
Hormonal
Activity
Relative
Potency
Effective
Period
in days
Ralgro® Estrogen Low 60 - 90 days
Synovex-C® Estrogen Low 60 - 90 days
Calfoid® Estrogen Low 60 - 90 days
Magnum® Estrogen Moderate 80 - 120 days
Synovex-S/H® Estrogen Moderate 80 - 120 days
Implus-S/H® Estrogen Moderate 80 - 120 days
Finaplix-S/H® Androgen Moderate 60 - 90 days
Finaplix-S/H® Androgen
Syn/Imp/Ral Estrogen High 90 - 100 days
Revalor-S/H® Androgen
Estrogen
High 90 - 120 days
Synovex Plus® Androgen
Estrogen
High 90 - 120 days

Reimplanting, which is the administration of an additional implant, is usually scheduled to coincide with the declining level of circulating implant growth promotant, but always above the effective level. The optimum reimplant time is referred to as the reimplant 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. Therefore, the highest rates of gain can be expected during the first part of the effective period.
     Because implant growth promotants interact with the production of hormones produced by the animal, they have not been recommended or approved for use in breeding cattle or calves less than 45 days of age.  

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 1.5 pounds per day.
     Previously implanted cattle are of concern to cattle buyers who take advantage of compensatory gain potential of cattle. Producers should receive a premium equivalent to the loss of production to consider not implanting suckling calves or stocker cattle.
     In feeder cattle, estrogenic growth promoting implants improve feed efficiency and gain 5-15 percent. Implants which include TBA can provide an additional three to five percent improvement in feed efficiency and daily gain. A properly designed reimplant program can sustain implant associated improved performance beyond the payout that would be expected for a single implant.


Conclusions
     Countless research studies have been conducted over the years proving the value of implants as a growth promotant for the improvement of performance and profits.  In the next issue we will continue this discussion, especially pertaining to how to properly use implants as well as the many safety issues which have been raised over recent years.

Dr. Steve Blezinger is a nutritional and management consultant with an office in Sulphur Springs.  He can be contacted at P. O. Box 563 Sulphur Springs, TX 75482, by phone at (903) 885-7992 or by e-mail at sblez@unicomp.n
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