PSXIII-6 Effects of cyclic monensin feeding on ruminally cannulated beef steers consuming low-quality forage

Abstract

Abstract The loss of monensin efficacy when fed continuously requires further study for development of novel feeding strategies that may prolong its effectiveness. In the present study, effects of cyclic monensin feeding on utilization of low-quality forage (LQF; 4.9%CP) were evaluated using ruminally cannulated steers (12 Bos taurus; 260 kg BW). Steers were randomly assigned to one of three treatments: 1) CON (0 mg∙hd-1∙d-1 monensin; Rumensin® 90, Elanco Animal Health, Greenfield, IN), 2) MON (200 mg∙hd-1∙d-1 monensin) or 3) CYC (200 mg∙hd-1∙d-1 monensin for 14 d and 0 mg∙hd-1∙d-1 monensin for subsequent 14 d). Dried distillers grains (1 kg∙hd-1∙d-1) were fed for monensin inclusion. Each of four periods were 28 days in length. Hay, ort, and fecal samples were collected d 10–14 of each period for measures of digestion. Rumen fluid was collected with a suction strainer 0, 2, 4, 8, and 12 h after feeding on d 14 for VFA analysis. Data were analyzed using the MIXED procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC). A period × treatment interaction was not observed for any measure of digestion (DMD, OMD, NDFD; P ≥ 0.39). A period × treatment interaction (P < 0.01) was observed for acetate, propionate, and A:P. An hour effect was observed for all ruminal fermentation parameters (acetate, propionate, A:P ratio, total VFA; P ≤ 0.01). No treatment effects or interactions were observed for any ruminal fermentation parameters by period 4 (P ≥ 0.15), but an hour effect was observed for all parameters (P ≤ 0.03) in period 4. Exploration of novel feeding strategies results in knowledge beef cattle producers can apply in their operations. This data is particularly relevant in cow-calf operations where LQF is often consumed. Although cyclically feeding monensin was similar to continuous feeding, this research furthers our knowledge and understanding of monensin.