25 Effect of Cyclic Monensin Feeding on<i>in Situ</i> Degradability of Low-Quality Forage Fed to Ruminally Cannulated Beef Steers

Abstract Effects of cyclic monensin feeding on in situ disappearance kinetics low-quality forage (LQF; 4.9% CP) were evaluated. Ruminally cannulated steers (n = 12; Bos taurus; 260 kg BW) consuming LQF randomly assigned to 3 treatments a completely randomized design: CON (0 mg∙animal-1∙day-1 monensin; Rumensin 90, Elanco Animal Health, Greenfield, IN), 2) MON (200 monensin), or 3) CYC for 4 d and 0 subsequent d). Steers fed dried distillers’ grains with solubles (1 kg∙animal-1∙day-1) inclusion. Four 28-d replicated cycles used allowing 9 days treatment adaptation, sampling, withdrawal within the group. Low-quality samples weighed into × 20 cm polyester bags replicates four each sampling hour. On 0, all placed ventral area rumen removed 4, 8,6, 24, 48, 72 hours post feeding. Upon removal, rinsed ice water, frozen until final removed. Subsequently, washed utilizing commercial washing machine, at 55°C constant weight residues analyzed DM. Ruminal DM degradation data over time fitted first-order exponential model discrete lag using NLIN procedure SAS 9.4, then parameters compared PROC GLIMMIX compare dietary period included as random variable. There was no effect (P ≥ 0.22) potentially degradable DM, rate degradation, residue, lag, wash loss Results are consistent findings concurrent vivo study conducted by Hook et al. (2022). Further evaluation NDF degradability is required determine clear an LQF.