Effects of Synovex One Grass, Revalor-G, or Encore implants on performance of steers grazing for up to 200 days

Growth rates by cattle (n = 986) grazing for 200 d and treated with Synovex One Grass (SOG; 150 mg of trenbolone acetate, 21 mg of estradiol benzoate), Revalor-G (REVG; 40 mg of trenbolone acetate, 8 mg of estradiol), or Encore (ENC; 43.9 mg of estradiol) were measured under field use conditions in a randomized complete block design. Blocks were defined by study start dates (n = 3). Crossbred beef cattle, which included steers (n = 669) and bulls castrated upon arrival (n = 317), were stratified by sex and pretreatment BW within start date and assigned to treatments within strata (n = 328 to 330 per treatment, initial BW = 191 ± 2.3 kg). Implants were given on d 0 after BW was measured. Blocks were subdivided into pasture management groups with equal numbers from each treatment on each pasture, and animal was the experimental unit. Cattle grazed pastures supplemented with 26% CP concentrate and bermudagrass hay during periods of limited forage. Cattle BW were also measured on d 70 and 200; implant status (present or absent) was documented on d 70. Average BW of SOG cattle (391.2 kg) was greater (P < 0.05) on d 200 than REVG (380.7 kg) or ENC (381.4 kg). Between d 0 and 200, ADG by SOG cattle was 1.00 kg/d, which was greater (P < 0.05) than REVG (0.95 kg/d) or ENC (0.95 kg/d). Economics were assessed based on cattle purchase and sale prices, implant costs, and morbidity; cattle treated with SOG returned $24.35 more than REVG and $26.77 more than ENC (P < 0.05). Over 200 d, grazing cattle implanted with SOG gained more than REVG or ENC, which increased returns.