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The objective of this research was to determine the influence of implanting heavy wether lambs with 12 mg zeranol (1 pellet Ralgro, Merck Animal Health. Madison, NJ) 59 d before harvest. Average daily gain (ADG), feed efficiency, and carcass merit were evaluated. Polpypay and crossbred wethers (n = 32 total) were equally divided into two treatment groups within a randomized complete block design. Sixteen pens were used resulting in 8 replicate pens per treatment. Wethers were fed a finishing diet consisting of cracked corn, soybean meal and soybean hulls ad libitum for 59 d. Lambs had access to clean water at all times from water fountains. Lambs were weighed on d 0, 1, 14, and 59 lambs. On d 59, 16 lambs (8 lambs/treatment) were harvested in the South Dakota State University Meat Lab. Hot carcass weight (HCW), dressing percent (DP), rib fat, body wall thickness, ribeye area, boneless closely trimmed retail cut percentages and yield grades were recorded. Final body weight (BW), cumulative ADG and gain efficiency were greater (P ≤ 0.01) for implanted lambs by 2.9%, 25.0%, and 35.2%, while dry matter intake (DMI) was not appreciably influenced by implant treatment (P = 0.18). No appreciable differences were noted (P ≥ 0.17) between treatments for any carcass traits measured. These results indicate that zeranol improves growth performance without detriment to carcass quality which implies that producers can improve profitability due to increased gains and efficiency.


South Dakota State University


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