Effects of monensin source on in vitro rumen fermentation characteristics and performance of Bos indicus beef bulls offered a high-concentrate diet

摘要: In Exp. 1, Brachiaria ruziziensis (11.1 % CP) was inoculated or not with two sources of monensin, resulting in three treatments: 1) no monensin inoculation (CONT), 2) 20 mg sodium-A/kg DM (Elanco Animal Health; MON-A), and 3) sodium-B/kg (Shandong Qilu King-Phar Pharmaceutical Co. Ltd.; MON-B). Three rumen-fistulated Jersey steers were offered a cool-season forage-based diet used as the rumen inoculum donors. Volatile fatty acids concentrations evaluated at 0, 6, 12, 24, 30, 48 h after treatment inoculation. Overall, acetate butyrate reduced MON-A vs. CONT (P ≤ 0.02), whereas both products Ac:Pr ratio 0.01); however, also = 0.05) MON-B. A × hour interaction detected for propionate concentration 0.01), primarily because resulted greater than MON-B 24 0.03), but differences observed between ≥ 0.27). 2, 240 Nellore bulls (initial BW 363.2 ± 40.9 kg) ranked blocked according to initial BW, within blocks animals allotted into pens (n 10 pens/treatment). Pens randomly assigned one corn-based plus 28 MON-A/kg DM, MON-B/kg DM. The composed sugarcane bagasse, ground corn, DDGS, urea, mineral-vitamin mix. experimental period lasted 106 d divided 21-d adaptation an 85-d finishing phase. During phase, increased 0.01) change, ADG, F:G, well DMI variation 0.02). When entire evaluated, effects final DMI, ADG 0.26). Nonetheless, included only improved efficiency by reducing F:G biological 0.05). Additionally, carcass tended 0.10) be MON-B, other characteristics 0.53). summary, source vitro during feedlot phase significantly affected energetic performance animals.