Abstract
Randomized complete block design experiments (n = 6 experiments) evaluating steroidal implants (all from Merck Animal Health, Madison, NJ) were conducted in large-pen feedlot research facilities between 2015 and 2018 comparing an 80 mg trenbolone acetate (TBA) and 8 mg estradiol-17β (E2) initial implant (Revalor-IH) and reimplanted with 200 mg TBA and 20 mg E2 (Revalor-200; REPEATED) to a single 80 mg TBA and 8 mg E2 uncoated; 120 mg TBA and 12 mg E2 coated implant (Revalor-XH) at arrival (SINGLE) on growth and carcass responses in finishing heifers. Experiments occurred in Nebraska, Oklahoma, Washington, and Texas. Similar arrival processing was used across experiments where 17,675 heifers [initial body weight = 333 kg SEM (4.1)] were enrolled into 180 pens (90 pens per treatment with 65–240 heifers per pen) and fed for 145–222 d. Only REPEATED heifers were removed from their pen at reimplant. Diets contained monensin and tylosin, consisted of ingredients common to each region, and contained greater than 90% concentrate. Ractopamine hydrochloride was fed for a minimum of 28 d prior to harvest. Linear mixed models were used for all analyses; model-adjusted means for each implant group and the corresponding SEM were generated. Distributions of U.S. Department of Agriculture (USDA) quality grade (QG) and yield grade (YG) were analyzed as ordinal outcomes. No differences (P ≥ 0.11) were detected for any performance parameters except dry matter intake (DMI), where SINGLE had greater (P = 0.02) DMI (9.48 vs. 9.38 ± 0.127 kg) compared with REPEATED. Heifers implanted with REPEATED had greater (P ≤ 0.02) hot carcass weight (HCW; 384 vs. 382 ± 2.8 kg), dressing percentage (64.54 vs. 64.22 ± 0.120%), and ribeye area (91.87 vs. 89.55 ± 0.839 cm2) but less (P ≤ 0.01) rib fat (1.78 vs. 1.83 ± 0.025 cm) and calculated YG (2.82 vs. 2.97 ± 0.040) and similar (P = 0.74) marbling scores (503 vs. 505 ± 5.2) compared with SINGLE heifers. Distributions of USDA YG and QG were impacted (P ≤ 0.03) by treatment such that REPEATED had fewer USDA Prime and YG 4 and 5 carcasses. Heifer growth performance did not differ between implant regimens, but HCW and muscling did, perhaps indicating that REPEATED may be suited for grid-based marketing, and SINGLE might be suited for heifers sold on a live basis depending upon market conditions and value-based grid premiums and discounts. However, these decisions are operational dependent and also may be influenced by factors including animal and employee safety, stress on animals, processing facilities, time of year, labor availability, and marketing strategies.
Highlights
Cattle implanted with a combination of trenbolone acetate (TBA) and estradiol-17β (E2) steroidal implants have been shown to consistently exhibit improved average daily gain (ADG), increased dry matter intake (DMI), and decreased dry matter (DM) feed conversion, marbling, and yield grade (YG) compared to nonimplanted cattle or cattle implanted with lower potency implants, fed for slaughter to equal days on feed (DOF; Johnson et al, 1996; Parr et al, 2011a; Smith et al, 2019a)
No significant differences were detected (P ≥ 0.11) for initial body weight (BW) (333 vs. 333 ± 941 kg); final BW calculated with deads and removals—excluded (599 vs. 600 ± 4.5 kg), ADG (1.51 vs. 1.51 ± 0.022 kg) or gain-to-feed ratio (G:F; 0.160 vs. 0.159 ± 0.0010); final BW calculated with deads and removals—included analysis for ADG (1.44 vs. 1.44 ± 0.022 kg) or G:F (0.153 vs. 0.152 ± 0.0020); mortality (0.83 vs. 0.94 ± 0.160 %), removals (1.43 vs. 1.17 ± 0.220 %), or realizers (1.99 vs. 1.89 ± 0.270 %) for REPEATED and SINGLE, respectively
DMI was influenced by implant program, and heifers administered the SINGLE implant had greater (P = 0.02) DMI (9.46 vs. 9.38 ± 0.127 kg) compared to heifers administered REPEATED
Summary
Cattle implanted with a combination of trenbolone acetate (TBA) and estradiol-17β (E2) steroidal implants have been shown to consistently exhibit improved average daily gain (ADG), increased dry matter intake (DMI), and decreased dry matter (DM) feed conversion, marbling, and yield grade (YG) compared to nonimplanted cattle or cattle implanted with lower potency implants, fed for slaughter to equal days on feed (DOF; Johnson et al, 1996; Parr et al, 2011a; Smith et al, 2019a). Estrogenic implants change frame size and delay fattening in cattle (Preston, 1975). This shift in frame size and, final shrunk body weight (BW) requires implanted cattle, and cattle given greater doses of anabolic compounds, be fed to greater final BW in order to reach similar empty body fat percentage as compared to cattle not administered a steroidal growth implant (Preston et al, 1990). The primary objective of these experiments was to compare animal growth performance and carcass traits between a noncoated initial and reimplant program and a single-coated implant at feedlot arrival in beef heifers using a pooled analysis approach. A pooled analysis approach has many advantages over a single-trial analysis, such as a greater sample size to compare outcomes and that a pooled analysis provides estimated means and the associated SEMs with more potential generalizability as they represent data from multiple populations of cattle, study sites, genetic types, and dietary ingredients
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