One hundred sixty-five crossbred steers averaging 823 lb were utilized to
evaluate the daily or weekly rotational feeding of ionophores. Treatments were (g/ton
of feed, 90% dry basis): 1) Bovatec (B; 30), 2) Rumensin plus Tylan (RT; 25 and 10,
respectively), 3) treatments one and two in a daily rotation (D), and 4) treatments
one and two in a weekly rotation (W). Steers fed RT consumed less (P<.05) dry matter
than B, D>or W steers. No differences (P>.15) in daily gain were observed, suggesting
that the increased consumption by B, D) and W steers was accompanied by an
al teration in passage rate and/or other kinetics of digestion, such that additional
consumption was poorly utilized. Thus, RT steers gained 3.9% more efficiently
(P=.06) than B steers and numerically more efficiently than D or W steers. No
differences were observed among treatments for carcass quality or yield. Performance
of D and W steers did not differ from that predicted by the performance of steers fed
B and RT fed separately, indicating no synergism from alternate feeding of ionophores
in this study.
