Implanting preweaning is one of the most cost effective ways to increase production for the cow-calf producer. Implants are typically administered when the calves are between 2 months and 4 months of age. Research shows that implants given during the suckling phase will increase average daily gain (ADG) of steer calves by approximately 0.10 pounds per day.
The increase in gain by implanting heifers is slightly better, at 0.12 pounds per day. Implanting heifer calves at birth decreases the pregnancy rate of replacement heifers by 30 to 50 percent, but implanting heifers between 1 and 3 months of age does not affect pregnancy rate later in life.
Most calf implants are designed to last 120 days. Calves should be 30 days to 45 days old before they are implanted; refer to manufacturers’ labels for approved timing. Bull calves intended for breeding should not be implanted. Bull calves not intended for breeding should be castrated at the time of implanting because implants impact scrotal development, which makes later castration more difficult.
Many producers follow the practice of leaving bull calves intact until weaning rather than castrating them at an early age. Jokingly known as the “Oklahoma implant” in other beef producing areas, the idea is that natural hormones produced in the testicles increase ADG and weaning weight of the calves.
Numerous research trials have shown that implanted steer calves gain weight faster and wean heavier than bull calves. This is because bull calves have very little testosterone production until they reach puberty at a much later age than normal weaning.
The stress of castration at weaning reduces postweaning gain potential and the calf’s ability to withstand diseases typically associated with weaning and marketing. This difference in the postweaning performance of bulls versus steers is recognized by cattle buyers, as indicated by the $5-10/cwt premium for steers over intact bull calves. Producers wanting to maximize the value of male calves at weaning should consider early castration at birth or at 2 months to 4 months of age and should use an implant approved for nursing calves.
Implanting your calves before weaning is cost effective and will increase weaning weights of both steers and heifers with very little impact on reproduction rates in replacement heifers. There are several products labeled for use in preweaned calves. Using the right product at the right time can provide returns of $25-30 for each dollar invested in implants—this will help pay for the increased production costs we are facing this year. — Paul Beck, Oklahoma State University Extension beef nutrition specialist
