In an effort to insure a higher percentage of replacement heifers are bred to calve early in their first calving season, ranchers should consider using a supplement containing an “ionophore” in the growing diet of the heifers. "Ionophore" is the generalized name for the feed additives such as monensin (RumensinTM) and lasalocid (BovatecTM). Both are presently approved for use with growing programs for replacement heifers.
Research conducted in Texas and Wyoming indicated that growing heifers fed an ionophore at lable dosage reached puberty at an earlier age than did similar heifers fed similar diets containing no ionophore. Most stocker cattle research has indicated that the addition of an ionophore will increase average daily gain by .1 to .2 pound per day. Over a 150 day growing period of a replacement heifer, this means an additional 15-30 pounds in average weight improvement of the heifers by breeding time.
Source: Glenn Selk