PSIX-2 Residual Effect of Narasin on Ruminal Fermentation Characteristics in Steers

Abstract This study aimed to evaluate the effect of narasin withdrawal on steers ruminal fermentation characteristics. Nellore [n = 30; initial body weight (BW) 281 ± 21 kg] cannulated at rumen were assigned individual pens in a randomized complete block design according their shrunk BW. The trial lasted 156 days, divided into 2 periods. first period 140 days and consisted daily supply narasin. In second (last 16 days) animals not supplemented with narasin, when residual additive was evaluated. diet composed by 99% haylage Tifton-85, 1% concentrate used as delivery vehicle for experimental diets were: 1) no feed additives (CON); 2) 13 mg narasin/kg DM (N13); 3) 20 (N20). dry matter intake (DMI) evaluated fluid obtained day 0, 1, 3, 5, 8 after withdrawal. data analyzed using MIXED procedure, considered significant P ≤ 0.05. DMI affected (P ≥ 0.27). There treatment interaction removal molar ratio acetate < 0.01), propionate ac:prop 0.01) ammonia nitrogen 0.03). inclusion linearly reduced increased 0.04), decreased up 5 Narasin 1 0.01). It is concluded that use results process from diets.