2012 Annual Report 1a.Objectives (from AD-416): The objective of the experiment is to test the hypothesis that gilts (young female hogs) that consume meat from beef steers implanted with estrogenic hormones will have higher levels of estrogenic activity in serum and edible tissue than gilts fed beef from non-implanted steers or a non-meat alternative, tofu. These data will provide evidence to support or refute the hypothesis that implanting beef steers with estrogenic hormones has adverse effects on consumers. 1b.Approach (from AD-416): Beef steers will be implanted according to FDA-approved label directions and slaughtered in a USDA-inspected facility. Control beef steers will not be implanted. Meat from control and test animals will be fed to gilts on a daily basis from weaning until first estrus. Gilts at first estrus will be slaughtered and serum and tissues analyzed for physiologic reproductive endpoints. In addition, estrogenic activity in serum and skeletal muscle will be measured using the cell-based E-Screen assay. 3.Progress Report: Implants of estrogenic steroids are used by the beef industry to increase the rate of weight gain and to improve tenderness of meat. Consumer groups have expressed concern that implanting beef cattle is associated with the early onset of puberty in girls who eat beef. A study was conducted by North Dakota State University using young female hogs as a model for humans. Growth and reproductive variables were not affected by the inclusion of beef from implanted cattle in the diet of test animals. The ARS laboratory in Fargo, ND measured the estrogenicity of each diet using a very sensitive bioassay (E-Screen). Diets supplemented with beef from implanted or non-implanted cattle were nearly identical in relative estrogenicity. Burgers made from tofu contained approximately 100-times the estrogenic activity of burgers made from meat of implanted cattle. Serum samples from hogs provided dietary beef have been assayed and the data analyses are in progress.