Interpretive Summary: Effects of administration of a growth promoting implant during the suckling phase or at weaning on growth, reproduction, and ovarian development in replacement heifers grazing native range 

By: Shelby L Rosasco, Emily A Melchior-Tiffany, Cierrah J Kassetas, Shad H Cox, Richard L Dunlap, Jennifer A Hernandez Gifford, Eric J Scholljegerdes, Robert A Cushman, Adam F Summers

Management of beef females during the first year of life can impact fertility and reproductive longevity. Cattle producers can improve calf weight gains by using growth promoting implants; however, to be applicable, they must not negatively impact heifer reproductive performance or development. Understanding the impact of growth promoting implants on growth, fertility, and reproductive development is important to determine if they can be utilized as an effective management strategy in heifers intended to be retained in the breeding herd. To determine if growth promoting implants influence fertility, 233 heifer calves either received no implant, a Synovex-C implant at 2 mo of age, or a Synovex-C implant at 7 mo of age. Implanting heifers at 2 mo of age increased body weight at weaning. Implanting heifers at 7 mo of age did not improve body weight gains. Implanting heifers at 2 or 7 mo of age resulted in similar pregnancy rates. By using a growth promoting implant at 2 mo of age in beef heifers, producers may be able to increase heifer weaning weight without negatively affecting reproductive development or pregnancy rates. Additional body weight at weaning may provide a profit advantage for heifers not retained as replacements.

Read the full article on the Journal of Animal Science.