Cazerta Duarte Goulart, Ricardo

Fleury Azevedo Costa, Diogo

Alves Correa Carvalho da Silva, Tiago

Francklin de Souza Congio, Guilhermo

da Silva Marques, Rodrigo

Corsi, Moacyr

2023

<p>The effectiveness of feed additives delivered through free-choice mineral mixtures (MMs) to grazing cattle remains unclear. Two farm-scale and one in vitro experiment (Exp.) were conducted to investigate the effects of salinomycin and virginiamycin, delivered through an MM, on growing bulls grazing tropical pastures. In Exp. 1, 316 zebu (Bos indicus) Nellore bulls (225 ± 26.7 kg liveweight (LW)) were randomly allocated to four treatments: (1) MM no additives (CON), (2) MM with salinomycin at 1950 mg/kg (SLI), (3) MM with salinomycin at 780 mg/kg (SHI), and (4) MM with virginiamycin at 1950 mg/kg (VGN). Over 123 days, these bulls grazed tropical grasses on pastures of guinea grass, palisade grass, or Bermuda grass. No significant treatment effects were observed for oocyst eggs or ruminal parameters. Bulls fed VGN had higher average daily gain (ADG) compared to CON (<i>p = 0.02</i>) and SLI (<i>p = 0.03</i>) but similar compared to SHI (<i>p = 0.07</i>). In Exp. 2, 308 zebu cross bulls (237 ± 23.0 kg LW) grazed Bermuda grass paddocks and were allocated into two treatments: (1) MM with no additives (CON) and (2) MM containing virginiamycin at 2522 mg/kg (VGN). Cattle fed VGN had a significantly higher ADG (<i>p = 0.007</i>). Exp. 3 tested salinomycin's effectiveness in vitro at different exposure times to MM, revealing no impact of exposure time on short-chain fatty acid production. In conclusion, virginiamycin delivered through free-choice MM can increase grazing beef bulls' ADG by 12% compared with CON, with no clear link to rumen fermentation or coccidiostat effects.</p>

Ruminants, 3(4), p. 483-494

2673-933X

https://hdl.handle.net/1959.11/59081

MDPI AG

Attribution 4.0 International

Farm-Scale Effectiveness of Feed Additives Supplied through a Mineral Mix for Beef Cattle Grazing Tropical Pastures

Journal Article

Publication