Date of this Version
Published in 2013 Nebraska Beef Cattle Report.
Two identically designed trials were conducted in separate years at the University of Nebraska Haskell Agricultural Laboratory, Concord, Neb., using 192 crossbred heifers (96/trial). Within a trial, heifers were assigned randomly to 2 groups (3 pens/group): 1) treatment (TRT) animals were administered synthetic hormones via subcutaneous implants (Ralgro and Revalor-H) and fed Melengesterol Acetate (MGA), or 2) control (CON) animals with no synthetic hormone provided.
Gains and feed conversions were 18.8 and 7.5% better, respectively, for TRT, while CON had 16.7% greater choice and prime carcasses. In runoff samples, progesterone was greater for CON. With the exception of androsterone, average hormonal concentrations in pen surface samples were less than 11 ng/g and concentrations of all compounds were not different across treatments. Results indicate that low levels of both natural and synthetic hormones are found on the feedlot surface and in runoff from feedlot pens.