Effects of chlortetracycline (CTC) and Revalor-S on the growth performance and carcass quality traits of finishing beef steers

Kitts, S.E.; Harmon, D.L.; Vanzant, E.S.; McLeod, K.R.

Journal of Animal and Veterinary Advances 5(1): 70-76


Accession: 004423238

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The objective of the current study was to ascertain the effects of chlortetracycline (CTC) and Revalor-S, both alone and in combination, on the growth performance and carcass merit of finishing beef steers. Ninety-six English-Continental crossbred steers (401+or-1 kg) were blocked according to body weight (BW) and pens were assigned randomly to a 2x2 factorial arrangement of treatments of either 0 or 39.6 ppm (DM basis) CTC/day with and without Revalor-S. Steers received ad libitum amounts of a 90:10 concentrate-forage diet formulated to provide 105% of the Metabolizable Protein (MP) requirement for steers gaining 1.60 kg/day during days 1-62 and 1.20 kg/day during days 63-139. Steers were slaughtered on days 126 or 140 to determine carcass quality characteristics. Growth and feedlot performance data were adjusted to reflect a 139-day feeding period. During days 1-84 of the experiment, Revalor-S increased average daily gain (ADG; p<=0.01) by an average of 25% and efficiency of gain (p>=0.004) by an average of 27% relative to non-implanted steers. There were no effects (p<=0.13) of CTC on ADG or feed efficiency during days 1-84; however, dry matter intake (DMI) decreased (p<=0.01) during days 29-56 for steers receiving CTC compared to those receiving no CTC. During days 85-139, there was an interaction (p<=0.07) between CTC and implant for ADG and feed efficiency. In the absence of CTC, implanted steers gained an average of 0.74 kg/day more BW (p<=0.02) and 60% more efficiently (p<=0.02) than non-implanted steers. However, in the presence of CTC, there was no effect (p<=0.13) of implant. Treatment did not affect carcass quality (p<=0.22). Across the 139-day feeding period, implant increased ADG (p<0.0001), while CTC decreased DMI (p<=0.02). Efficiency of BW gain was greater for implanted steers in the absence, but not in the presence, of CTC (CTC x implant interaction, p<=0.03). This experiment shows that Revalor-S increases ADG, while efficiency of gain is partially diminished when subtherapeutic levels of CTC are fed in conjunction with this implant.