Of all the management practices available to cow/calf and stocker cattle producers, implanting suckling calves and stocker cattle offers one of the highest benefit- to-cost ratios. Many implants are available, but selection of an implant is less critical than the decision on whether to implant or not.
Implants for calves and stocker cattle
Table 1 lists implants available for use in suckling calves and pasture cattle. The active compounds in calf implants are zeranol, estradiol benzoate-progesterone, or estradiol 17-beta. Stocker cattle implants contain the same active compounds, plus a combination of estradiol and trenbolone acetate. Some stocker cattle implants are designated for use in heifers or steers; they generally are denoted by an “H” or “S” in the implant name. These implants have no withdrawal time before sale or slaughter.
To administer implants, designate one person to implant while processing or working cattle. To avoid infections and reduced implant performance, make sure the ear surface, the implant applicator needle and the hands of the person implanting the cattle are clean. Some companies distribute disinfectant trays along with the implant applicator. Use these trays at chuteside as a place to rest the implant applicator when not in use and to clean the applicator needle. Before administering the implant, use a sponge soaked in disinfectant to remove manure and other foreign material from the ear surface. You can also use the sponge to clean the applicator needle.
Protect implant cartridges and belts from dust and other contaminants during storage and at chuteside. Some implants must be refrigerated during storage.
Place the implant under the skin on the backside of the middle third of the ear (Figure 1). Implanting at any other location violates federal law.
Applicators vary for different implants. Become familiar with the mechanical operation of the applicator to ensure proper implant placement, and avoid crushing, bunching or wasting implant pellets. The needle on the implant applicator must be sharp and free of spurs to avoid unnecessary trauma to the ear and implant site.
After placing the implant in the ear, palpate the site to ensure that the implant was properly placed. Apply pressure on the area punctured by the needle to help the wound close and prevent dirt and other foreign materials from entering the implant site.
Implanting suckling calves once with zeranol or estradiol- progesterone type implants will increase daily weight gains an average of 0.10 pound per day for steer calves and 0.12 pound per day for heifer calves (Selk, 1997). Implus-C® (Calf-oid®), Component- C®, Compudose®, Encore®, Ralgro®, and Synovex-C® are labeled for suckling steers and heifers. Component- S®, Component-H®, Implus-S®, Implus- H®, Synovex-S®, and Synovex-H® can also be used in sucking calves but are recommended for calves weighing over 400 pounds. Table 1 lists specific information and restrictions.
Potential replacement heifers:
Concerns about reproductive performance have limited the use of growth implants in heifer calves that are potential herd placements. Currently, Synovex-C®, Component-C® and Ralgro® are the only implants labeled for use in replacement heifer calves (see Table 1). Use is restricted to heifers older than 30 days for Ralgro® and 45 days for Synovex-C® and Component-C®.
Implanting heifers at or near birth can reduce future reproductive performance. However, research has shown that one implant administered between 2 months of age and weaning has little effect on subsequent reproductive performance. The impacts on future reproductive performance are less predictable and can be severe in some cases when implants are administered after weaning. The probability and severity of reduced reproductive performance increases when heifers are implanted more than once between birth and puberty. Heifer calves that have been implanted have a larger pelvic area at 1 year of age. However, by calving time at 2 years of age, these differences are small and calving ease is not improved.
If replacement heifers are identified at a young age, do not implant them, as it provides no benefits; implants do not improve age at puberty nor calving ease. However, if replacement heifers cannot be identified at an early age, implanting all the heifer calves once between 2 months of age and weaning does not significantly affect reproduction in heifer calves eventually selected for replacements. The remaining heifer calves will be heavier at weaning.
Potential herd bulls:
No implants are labeled for use in bull calves intended for future use as herd sires. Implants can suppress testicular development and reduce libido and semen quality.
A single implant will increase weight gain 8 to 18 percent, or 15 to 40 pounds, during the grazing season (Kuhl, 1997). If the grazing season is more than 100 to 120 days and the plane of nutrition is adequate, reimplanting or using an implant with a longer release period stimulates additional weight gain. All the implants listed in Table 1 can be used in stocker cattle. Implus-C® (Calf-oid®), Component- C®, and Synovex-C® are recommended for calves weighing less than 400 pounds and can be used with lightweight stocker cattle.
Reimplanting, or administering a second implant at some interval after the first implant, improves performance if the plane of nutrition is adequate. An implant releases (or “pays out”) compound for 70 to 400 days depending on the implant (Table 1).
Although the implant releases active compound over an extended period, at some point the quantity of active ingredient released declines to a level that does not stimulate performance adequately. Therefore, the recommended reimplanting interval for each implant is shorter than the estimated payout.
As a rule of thumb, the window to reimplant cattle is about 30 days less than the estimated payout. So, if an implant has a 100- to 140-day payout, then administer another implant between 70 and 100 days if you want to maintain circulating levels of the active compounds.
The Food and Drug Administration requires no withdrawal period before slaughter of implanted cattle. Beef from implanted cattle has a very low level of estrogen activity compared to other common foods. Table 2 lists the estrogenic activity of several common foods. Likewise, the potential amount of estrogen consumed in beef from implanted cattle is extremely low compared to that produced daily by the human body. If a person consumed 1 pound of beef per day from implanted cattle, the potential estrogen intake would be about 10 nanograms. In comparison, the daily estrogen production by the human body is about 100,000 nanograms for adult men, about 5,000,000 nanograms for non-pregnant women, and about 40,000 nanograms for a prepuberal child.