Growth implants in cattle have been the subject of this column before, but this week we will revisit the topic with some new information and a review of implant basics.
Implants contain hormones or combinations of hormones that trigger increased growth, primarily muscle, with the ultimate outcomes of increased growth rates, improved feed efficiency and increased carcass leanness. The hormones in implants include estrogenic hormones (estradiol, progesterone, zeranol) and androgenic hormones (trenbolone acetate).
Because different hormones or combinations of them result in differing growth rates, implants are classified as low-, mid- or high-potency. Single-hormone implants, or low-level estrogenic implants, generally are less potent than the combination implants typically used during the finishing period.
A common term heard in regard to implanting is payout, which is the length of time the active ingredient is released from the implant. This varies from about 60 to 200 days, depending on the type of implant.
In the feedlot scenario, calculating the approximate harvest date of the cattle should determine when and what type of implanting protocol to use. Cattle fed more than 120 days probably will benefit from re-implanting. Generally, when re-implanting cattle, the second implant should be at least as potent as or more potent than the first. For example, implanting with Revalor-IS during the growing phase and then re-implanting with Revalor-S would be following a moderate-potency implant with a high-potency implant. Letting an implant “run out,” or no longer release hormone toward the end of the feeding period, is costly because cattle generally are less efficient at the end of the feeding period regardless of management. Letting the implant run out only amplifies this drop in efficiency.
Research indicates that implanting cattle during the finishing period can result in an improvement in feed efficiency of about 10 percent compared to nonimplanted cattle fed the same ration, along with increasing final weights by 50 pounds or more. Implants are going to be most effective as part of a total program with a high-quality nutrition program in place and adequate energy and protein for the growth rate to ensure that the cattle reach their maximum potential.
Implanting can be managed to limit its impact on carcass quality. Delaying implanting is one strategy to help mitigate negative effects on carcass quality. By implanting cattle 10-21 days after arrival at the feedlot, we can get the calves on a higher plane of nutrition before implanting, which will help in regard to meeting the energy demands of improved growth and performance.
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