Influence of implant strategy on growth performance and carcass characteristics of calf-fed Holstein steers

The effect of initial implant type (short or long duration) and reimplant scheme on performance and carcass characteristics of calf-fed Holstein steers was evaluated. A total of 240 steers (113.5 ± 6.2 kg) were used in a 349-d trial. The 2 implant strategies were (1) implant on arrival with 43.9 mg of estradiol and reimplant on d 224 with 120 mg of trenbolone acetate and 24 mg of estradiol (Imp-2) and (2) implant on arrival with 100 mg of progesterone and 10 mg of estradiol benzoate and reimplant on d 112 and 224 with 120 mg of trenbolone acetate and 24 mg of estradiol (Imp-3). During the initial 112 d, performance was not affected by implant strategy. From d 112 to 212, Imp-3 had greater ADG (9.6%, P < 0.01), DMI (2.3%, P = 0.04), and gain efficiency (7.0%, P < 0.01) than Imp-2. During the final 137-d period, Imp-3 had similar ADG (P = 0.93) but greater DMI (4.1%, P < 0.01) and lower gain efficiency (3.9%, P < 0.01) than Imp-2. Overall, DMI (2.3%, P = 0.02) and final weight (1.9%, P = 0.07) were greater for Imp-3 versus Imp-2. Treatment effects on gain efficiency and energy utilization were not appreciable (P > 0.75). Implant strategy had minor effects on carcass characteristics (P > 0.10). Although, LM area was greater (4%, P < 0.01) for Imp-3 versus Imp-2. Implanting with a longer-duration implant on arrival followed by a combination implant on d 224 (Imp-2) may result in slightly lower ADG than implanting at 3 intervals (Imp-3).