title: Effect of monensin and monensin and tylosin combination on feed intake variation of feedlot steers.
abstract: A trial involving four commercial feedlots and an individual feeding trial evaluated the effect of monensin and monensin/tylosin on intake variation and deaths from digestive disorders. Four commercial feedlots in Texas and Colorado fed 2,904 yearling crossbred steers (340 kg) high-grain diets containing approximately 82% grain, 8% silage and alfalfa hay, 4% fat, and 6% supplement (DM basis). Steers were allotted randomly to one of three monensin/tylosin levels: 1) no monensin or tylosin (control); 2) 22 mg/kg of monensin and 11 mg/kg of tylosin; or 3) 33 mg/kg of monensin and 11 mg/kg of tylosin. Monensin/tylosin reduced DMI (P < .05) and improved ADG (P < .05) and feed efficiency (P < .01). Intake variation associated with dry matter offered per pen was not different among treatments. In the individual feeding trial, feeding 27 mg/kg of monensin reduced (P < .10) DMI variation during grain adaptation and during d 57 to 70 and d 97 to 110 compared with the control (no monensin) diet. The magnitude of intake variance was 5 to 10 times greater with individually fed steers than with steers fed in the commercial feedlot pens. When the DMI of the individually fed steers were averaged and treated as a pen of steers, DMI variance was reduced drastically and was not different between treatments. We interpret these data to indicate that monensin and monensin/tylosin reduce feed intake variation among individual steers within a pen of steers. Pen means mask individual animal variation to the point that it is difficult to detect treatment differences.
authors.affiliation: Department of Animal Science, University of Nebraska, Lincoln 68583-0908.
authors.forename: R A
authors.initials: RA
authors.lastname: Stock
authors.forename: S B
authors.initials: SB
authors.lastname: Laudert
authors.forename: W W
authors.initials: WW
authors.lastname: Stroup
authors.forename: E M
authors.initials: EM
authors.lastname: Larson
authors.forename: J C
authors.initials: JC
authors.lastname: Parrott
authors.forename: R A
authors.initials: RA
authors.lastname: Britton
mesh_terms: D000818:Animals; D002417:Cattle / Q000502:physiology*; D004032:Diet; D004041:Dietary Fats / Q000592:standards; D004338:Drug Combinations; D004435:Eating / Q000187:drug effects* / Q000502:physiology; D002523:Edible Grain / Q000592:standards; D008297:Male; D000455:Medicago sativa / Q000592:standards; D008985:Monensin / Q000494:pharmacology*; D011897:Random Allocation; D012820:Silage / Q000592:standards; D015645:Tylosin / Q000494:pharmacology*
chemical_list: D004041:Dietary Fats; D004338:Drug Combinations; D008985:Monensin; D015645:Tylosin