A290
Growth Implants


Introduction: Growth promoting implants are compressed pellets or slow release devices placed under the skin of the ear. These implants contain hormones that supplement the animal’s natural hormone production to increase growth rates and feed efficiency. They have been used throughout the United States for more than 25 years in commercial beef cattle. It is estimated that over 90% of all fed cattle are now implanted at least once in their lifetime.

All currently marketed implants contain some form of slow release estrogens, androgens, or progestins. To ensure that the products are safe and effective, they are regulated by the FDA and must go through the new animal drug approval process before marketing.

How They Work: Implants accelerate growth rates. Growth is largely controlled by the pituitary gland and its secretions of growth (somatotrophic) hormone. Implants act on the pituitary to produce increased levels of growth hormone, and at the cellular level to increase insulin production. The effect of these elevated hormone levels is an increase in the synthesis of muscle tissue and a reduction in the deposition of body fat. Because muscle tissue is more dense than fat, the increase in lean to fat production results in an increased rate of gain and more gain per pound of feed consumed. Table 1 summarizes the expected average improvements in daily gain and feed conversion from implanting cattle.

Table #1: Implant Effectiveness
Class of Cattle Expected Improvement
(Gain) (Feed Efficiency)
Nursing Calves 4-8% -
Growing Cattle 10-20% 6-8%
Finishing Cattle   6-12% 8-10%

Together, these increased efficiencies can reduce the cost of feedlot gain by $2 to $6 per cwt. This can result in an overall decrease in the cost of beef production of up to 7%. Using a $1 implant to yield a gain of 20 lbs. more than non-implanted cattle nets a 20:1 return on investment when calves are worth $1 per pound.

Recent studies indicate that aggressive implanting strategies can have a negative impact on carcass quality. Yield grades do not appear to be affected, but the percent of cattle grading choice can decrease 10 to 25% depending on the implant strategy used. For this reason, it is important to use an implant strategy that maximizes gain and meat quality. This is done by matching the animal to be implanted with the correct product.

Products: Only Ralgro, Synovex C, Component EC, and Implus C are approved for use in young calves. These products have a lower effectiveness and are safe for this stage of growth and nutrition. As the animal ages and the level of nutrition advances, the effectiveness of the implant should increase to match the growth characteristics of the animal. Within 120 days of harvest, hormone combinations, including trenbolone acetate, can be used. These are the most effective products and can be used during the periods of fastest weight gain with minimal impact on carcass quality grades. The following table lists some of the currently available implants, their principal ingredients, and the animals and stage of growth for which they are indicated:

Table #2: Implants Heifers Steers
Implant
(Active Ingredients)
For Use After Days of Activity  *Nurs. Grow. Finish. Replace. Nurs. Grow. Finish.
Ralgro
(Zeranol - 36 mg)
Birth 60-120 X X X X X X X
Synovex C or Component EC
(Progesterone - 100 mg 
Estradiol benzoate - 10 mg)
45 days 70-150 X     X X X X
Revalor G
(Trenbolone Acetate - 40 mg 
Estradiol - 8 mg)
Pasture Turnout 70-90   X X     X X
Synovex S or Component ES
(Progesterone - 200 mg 
Estradiol benzoate - 20 mg)
400 lbs. 70-150           X X
Synovex H or Component EH
(Testosterone - 200 mg 
Estradiol Benzoate - 20 mg)
400 lbs. 70-150   X X        
Revalor H
(Trenbolone Acetate - 140 mg 
Estradiol - 14 mg)
Feedlot
Arrival
70-90     X        
Ralgro Magnum
(Zeranol - 72 mg)
Feedlot
Arrival
80-120           X X
Synovex Plus
(Trenbolone Acetate - 200 mg 
Estradiol Benzoate - 28 mg)
Feedlot
Arrival
70-150             X
Finaplix S or Component TS
(Trenbolone Acetate - 140 mg)
Feedlot
Arrival
70-110           X X
Finaplix H or Component TH
(Trenbolone Acetate - 200 mg)
Feedlot
Arrival
70-110   X X        
Revalor S or Component TES
(Trenbolone Acetate - 120 mg 
Estradiol - 24 mg)
Feedlot
Arrival
70-120             X
Compudose
(Estradiol - 25.7 mg)
Feedlot
Arrival
150-180     X   X X X
Encore
(Estradiol - 43.9 mg)
Feedlot
Arrival
280-340     X   X X X

*Nurs. = Nursing animals; Grow. = Growing animals; Finish. = Finishing animals; Replace. = Replacement animals.

How to Implant: Follow the label directions carefully regarding age and weight restrictions and reimplanting. Be especially careful when implanting potential replacement heifers. Using the wrong product and/or implanting at the wrong age or wrong weight can all impair fertility. Reimplanting replacement heifers is not recommended. None of these implants are registered for use in bull calves and use of these hormones will reduce fertility in bulls.

Implants used for backgrounding and feedlot cattle are more potent than calf implants and require a higher nutritional plane for optimum performance. Implants containing trenbolone acetate are the most potent and should be considered terminal implants (ones given to older animals just prior to being harvested). Terminal implants should be given 100-120 days prior to harvest to minimize negative effects on carcass quality.

Using proper procedures for placing implants is important. Being clean and precise in location will improve implant performance. Use the following guidelines for proper administration:

  1. Properly restrain the animal in a way that allows good access to the ear.
  2. Clean and disinfect the back side of the ear. Infected implants will not perform well.
  3. Deposit the implant between the skin and the cartilage of the ear, just below the horizontal midline. The implant must not be placed too close to the head. Most implants should be placed in the middle third of the ear (Fig. #2).
  4. The insertion site of the needle will be towards the outer tip of the ear, one needle length from the desired "middle-third" position.
  5. Avoid placing the implant in the site of an old implant or in an area that will be used for an ear tag.
  6. Do not crush implants.
  7. Avoid injuring the major blood vessels of the ear.
  8. Disinfect the implant needle between applications.
Figure #1: This is a typical ear implant gun. The black arrow identifies a cartridge of Ralgro implants, and the white arrow identifies the needle portion of the gun.

 

Figure #2: The circled area indicates the middle-third of the ear where the implant should be placed.

 

Figure #3: The black arrow shows the desired "middle-third" location for the implant in this ear. The gun and needle will need to be pulled back towards the tip of the ear and inserted one needle length from the desired area for the implant. This insertion point is indicated by the white arrow.

 

Figure #4: This picture shows the needle fully inserted under the skin, with the tip of the needle ending in the desired location. The implant can now be released from the gun.