The choice of implants and a strategy for timing of implants has become very complex. Currently there are over 20 implants available. These implants differ primarily in the active ingredient and the potency or dosage of the active ingredient. Choosing the right system depends on the stage of growth, the time between implants, the length of ownership and even the marketing system.
Most implants have estrogen or estrogen-like compounds as the active ingredient.
Because androgens and estrogens effect growth of cattle in different ways, implants that have both estrogen and androgen as active ingredients cause almost twice the growth response as either implant alone. Potency Low potency estrogen implants are generally used as calfhood implants. Moderate potency estrogen implants are generally considered as weaning implants, during a growing phase, or as a first implant in the feedlot. Higher potency implants, combining TBA and estrogen as active ingredients should generally be reserved for terminal implants during the feedlot phase. More recently, lower and moderate dosage combination implants have been approved for stocker cattle and feedlot reimplant programs.