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

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

doi:10.3389/fvets.2023.1117639

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

Front Vet Sci. 2023 Apr 28:10:1117639. doi: 10.3389/fvets.2023.1117639. eCollection 2023.

Affiliations

¹ Department of Animal Nutrition and Production, School of Veterinary Medicine and Animal Science, University of São Paulo, Pirassununga, Brazil.
² Texas A&M AgriLife Research and Extension Center, Amarillo, TX, United States.
³ Department of Animal Science, Texas A&M University, College Station, TX, United States.
⁴ Department of Animal Science, Federal University of Amazonas, Parintins, Brazil.
⁵ Department of Animal Sciences, University of Florida, Gainesville, FL, United States.
⁶ Department of Animal Science, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Piracicaba, Brazil.
⁷ Department of Animal and Range Sciences, Montana State University, Bozeman, MT, United States.

Abstract

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 (P = 0.02) but not compared to CON, MM, MN, or NN (P ≥ 0.12). No differences in DMI were observed among the treatments during the finishing (P = 0.45) or the total feeding period (P = 0.15). Treatments did not affect the nutrient intake (P ≥ 0.51) or the total apparent digestibility of nutrients (P ≥ 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 (P ≤ 0.03), but no differences were observed between NM and NN (P = 0.66) or between CON, MM, and NN (P ≥ 0.11). No other differences between treatments were observed (P ≥ 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.

Keywords: adaptation; feed additives; feedlot; intake; ionophore; rumen.