Effects of a monensin ruminal delivery device on daily gain, forage intake and ruminal fermentation of steers grazing irrigated winter wheat pasture

• Published in: Journal of animal science Vol. 67; no. 8; pp. 2129 - 2139
• Main Authors: Davenport, R.W. (Livestock Advisory Services, Inc., Friona, TX), Galyean, M.L, Branine, M.E, Hubbert, M.E
• Format: Journal Article
• Language: English
• Published: United States Am Soc Animal Sci 01-08-1989
• Subjects: ANALISIS; ANALYSE; ANALYSIS; Animal Feed; Animals; BEEF CATTLE; BLOOD; BOEUF; BOLO DIGESTIVO; BOVIN DE BOUCHERIE; BUEY; BULLOCKS; Cattle - growth & development; Cattle - metabolism; CULTIVOS DE INVIERNO; CULTURE D'HIVER; Delayed-Action Preparations; DIGESTA; DRUGS; Eating - drug effects; FEED INTAKE; FERMENTACION; FERMENTATION; Fermentation - drug effects; GAIN DE POIDS; GANADO DE CARNE; GANANCIA DE PESO; GRAZING; INGESTION DE PIENSO; Male; MEDICAMENT; MEDICAMENTOS; Monensin - administration & dosage; Monensin - pharmacology; PASTOREO; PATURAGE; PRISE ALIMENTAIRE (ANIMAUX); Random Allocation; RUMEN; Rumen - drug effects; Rumen - metabolism; SANG; SANGRE; TRITICUM; Weather; WEIGHT GAIN; Weight Gain - drug effects; WINTER CROPS
• ISSN: 0021-8812; 1525-3163; 0021-8812
• DOI: 10.2527/jas1989.6782129x

Two trials evaluated the effects of a monensin ruminal delivery device (MRDD) on steers grazing winter wheat pasture. In Trial 1, 60 Hereford steers (initial wt 238.5 kg) grazed a 21.9-ha paddock of Vona-variety winter wheat for 112 d. Steers were assigned to either MRDD or control (C) treatments in a randomized complete block design. In Trial 2, eight ruminally cannulated steers (avg wt 234.4 kg) grazed a 2.4-ha paddock of Vona-variety wheat and were assigned randomly to either MRDD or C treatments. Three 11-d collection periods were conducted during early February, early March and early April. Chromic oxide was dosed to determine fecal output, and ruminal samples were collected on d 6 of each period. Nylon bags containing ground wheat forage were incubated ruminally beginning on d 8. In Trial 1, steers with MRDD tended (P less than .11) to gain more weight than C steers (.44 vs .38 kg/d). In Trial 2, wheat forage intake, in situ DM disappearance, ruminal pH, ruminal ammonia concentrations and ruminal proportions of acetate and total VFA concentrations were not affected by treatment. Ruminal proportions of propionate were increased (P less than .05) slightly by MRDD (20.3 and 19.2 mol/100 mol for MRDD and C, respectively). Butyrate proportions in ruminal samples were decreased (P less than .05) by MRDD during March but not in other sampling periods. Ruminal fluid chlorophyll concentration was less (P less than .05) for MRDD-treated vs C steers during early March but was greater (P less than .10) for MRDD-treated steers during early April. The MRDD shows promise as a method of supplying monensin to cattle grazing winter wheat forage.