Implanting calves with growth promoting implants is one of the most profitable practices for cattle producers. Unfortunately, my experience suggests that many local producers are simply not taking advantage of growth promoting implants in their calves. This could be due in part to a lack of familiarity with implants and their appropriate use or potentially, a deficiency in management strategy necessary to realize benefits.
Growth promoting implants are typically administered under the skin on the back side of the ear. Most products are composed of small pellets that provide a slow release of steroid hormones (or synthetic hormone-like compounds) into the blood stream of the animal. These hormones then act from a production standpoint to increase rate of gain and feed efficiency in the growing animal. Physiologically, most animals will show a significant increase in muscle deposition, a small increase in bone growth and a marginal decrease in fat deposition.
The actual performance advantage will vary from herd to herd based on factors such as animal genetics, available nutrition and type of implant used. However, producers can expect a 10-15 percent increase in average daily gain or an additional 15-20 lbs. of gain when implanting nursing calves. 
In order to achieve these results producers must keep in mind several factors that come into play with implant use. Most implants provide their effect over 70-100 days. This is important in regards to timing of implantation. For cow-calf producers, calves can be implanted at traditional ‘branding’ time or at around 2-4 months of age. If a preconditioning program is utilized with a 30-45 day post weaning phase, this provides plenty of time for the producer to realize the maximum return on investment. For those producers implanting stocker calves, implanting early allows for improved animal performance and efficiency throughout the stocker phase. In addition to adequate time, producers must also provide a sufficient plane of nutrition to allow calves to meet the elevated nutrient demands of more rapid growth.  The correct implant choice is also important and your local veterinarian can be an excellent advisor in choosing the appropriate implant for the animal’s stage of production. Proper administration is also necessary. Label directions should always be closely followed and the ear should be free from gross manure contamination to minimize injection site complications.
While a single implant at branding may not carry much long term reproductive implications, implanting replacement heifers and bulls is often not recommended. Additionally, implanting calves at weaning or when calves are sick or on poor pasture conditions may actually prove detrimental.
Under most circumstances, however, growth promoting implants represent an easy way for producers to boost pounds of production with few if any drawbacks. I strongly encourage local producers to consider implementing growth promoting implants into their current herd management protocol.
Darren Loula, DVM, is a large animal veterinarian at Fair Grove Vet Service in Fair Grove, Mo.


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