growth-promoting technologies, implants, beta-adrenergic agonists, feedlot performance, feedlot heifers, carcass characteristics


The use of growth-promoting technologies has become a common practice in the beef cattle industry as producers strive for efficient growth and greater lean deposition. Two common technologies include exogenous hormonal implants and beta-adrenergic agonists (β-AA). Combination implants containing estrogen and testosterone increase muscle mass by elevating protein synthesis and/or reducing protein degradation. The increase in protein synthesis allows the animal to produce more lean muscle tissue. Optaflexx (Elanco Animal Health, Greenfield, IN) is a popular β-AA that works as a repartitioning agent to redirect nutrients toward muscle deposition and away from adipose tissue production. The two technologies utilize separate pathways for muscle growth and can have additive results on efficiency and ultimate carcass characteristics. Feedlot heifer responses to growth-promoting technologies have been inconsistent and not as potent as those observed in steers. The objective of this study was to determine the effects of two growth-promoting programs on feedlot heifer performance and carcass composition.


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