AUTHOR=Baggio Marcelo , Gouvêa Vinícius N. , Barroso José Paulo R. , Miszura Alexandre A. , Limede Arnaldo C. , Soares Letícia C. B. , Ferraz Marcos Vinicius C. , Vicente Ana Carolina S. , Ferreira Evandro M. , Marques Rodrigo S. , Pires Alexandre V. 

TITLE=Different combinations of monensin and narasin on growth performance, carcass traits, and ruminal fermentation characteristics of finishing beef cattle

JOURNAL=Frontiers in Veterinary Science

VOLUME=10

YEAR=2023

URL=https://www.frontiersin.org/journals/veterinary-science/articles/10.3389/fvets.2023.1117639

DOI=10.3389/fvets.2023.1117639

ISSN=2297-1769

ABSTRACT=<p>The objective of this study was to evaluate the effects of different combinations of monensin and narasin on finishing cattle. In Exp. 1, 40 rumen-cannulated Nellore steers [initial body weight (BW) = 231 ± 3.64 kg] were blocked by initial BW and assigned to one of the five treatments as follows: Control (CON): no feed additive in the basal diet during the entire feeding period; Sodium monensin (MM) at 25 mg/kg dry matter (DM) during the entire feeding period [adaptation (days 1–21) and finishing (days 22–42) periods]; Narasin (NN) at 13 mg/kg DM during the entire feeding period (adaptation and finishing periods); Sodium monensin at 25 mg/kg DM during the adaptation period and narasin at 13 mg/kg DM during the finishing period (MN); and narasin at 13 mg/kg DM during the adaptation period and sodium monensin at 25 mg/kg DM during the finishing period (NM). Steers fed MM had lower dry matter intake (DMI) during the adaptation period compared to NM (<italic>P</italic> = 0.02) but not compared to CON, MM, MN, or NN (<italic>P</italic> ≥ 0.12). No differences in DMI were observed among the treatments during the finishing (<italic>P</italic> = 0.45) or the total feeding period (<italic>P</italic> = 0.15). Treatments did not affect the nutrient intake (<italic>P</italic> ≥ 0.51) or the total apparent digestibility of nutrients (<italic>P</italic> ≥ 0.22). In Exp. 2, 120 Nellore bulls (initial BW = 425 ± 5.4 kg) were used to evaluate the effects of the same treatments of Exp. 1 on growth performance and carcass characteristics of finishing feedlot cattle. Steers fed NM had greater DMI during the adaptation period compared to CON, MM, and MN (<italic>P</italic> ≤ 0.03), but no differences were observed between NM and NN (<italic>P</italic> = 0.66) or between CON, MM, and NN (<italic>P</italic> ≥ 0.11). No other differences between treatments were observed (<italic>P</italic> ≥ 12). Feeding narasin at 13 mg/kg DM during the adaptation period increases the DMI compared to monensin at 25 mg/kg DM, but the feed additives evaluated herein did not affect the total tract apparent digestibility of nutrients, growth performance, or carcass characteristics of finishing cattle.</p>