This article written by Dr. Reynold Bergen, BCRC Science Director, originally appeared in the October 2021 issue of Canadian Cattlemen magazine and is reprinted on the BCRC Blog with permission of the publisher.
Growth promotants dramatically improve the growth rates and feed efficiency of beef cattle. Trenbolone acetate (TBA) behaves like testosterone and is used in several feedlot implants (Component, Revalor, and Synovex). Melengestrol acetate (MGA) behaves like progesterone, a pregnancy hormone. Some feedlots feed MGA to suppress estrous cycles and riding activity in heifers until a few days before slaughter. Ractopamine (Actogain, Optaflexx) is a feed additive that improves weight gain, feed efficiency and leanness in the last 28-42 days before slaughter.
Growth promotants also have environmental benefits; reducing the number of days (and amount of feed) needed to finish cattle means fewer days producing greenhouse gases and manure, and less water, feed and fossil fuel inputs per pound of beef.
Animals metabolize and excrete these growth promotants over time – that’s why growth promotant residues in beef are too low to pose any risk to consumers. But do these excreted residues and metabolites pose a risk to the environment? How long do they persist in soil and manure, and is there a risk they could enter surface or groundwater?
A Beef Cluster study led by Frank Larney and co-workers at Agriculture and Agri-Food Canada’s Lethbridge Research & Development Centre and the University of Saskatchewan’s Toxicology Centre is examining these questions. Their first study was published earlier this year (Ractopamine and Other Growth-Promoting Compounds in Beef Cattle Operations: Fate and Transport in Feedlot Pens and Adjacent Environments; Environmental Science & Technology. DOI: 10.1021/acs.est.0c06450). Continue reading