Growth, Feed Efficiency and Metabolite Concentrations of Cattle Fed High Forage Diets with Lasalocid or Monensin Supplements

Abstract
Angus steers were fed one of six daily levels of antibiotic in supplements: control (no added drug); 183 mg monensin; 83, 175 or 220 mg lasalocid, or 149 mg lasalocid in mycelium cake. Alfalfa cubes and .57 kg of supplement were fed individually to five or six steers by means of electronic feeding doors. Cube consumption was ad libitum above daily consumption of supplement. Orthogonal contrasts of the five degrees of freedom for supplement additives showed that cattle fed monensin ate less (P<.01 and gained more slowly (P<.005) than cattle fed lasalocid. This result was possibly caused by the steers' aversion to monensin supplement, which, in turn, decreased dry matter intake too drastically for them to maintain adequate energy intake above maintenance for efficient growth. Lasalocid affected growth rate, feed efficiency and plasma glucose in a quadratic (P<.025) manner; steers fed 175 mg lasalocid/day grew fastest and most efficiently and had the highest plasma glucose concentrations. Cattle fed monensin had rumen (P<.005) and plasma (P<.10) acetate to propionate ratios lower than the average of cattle fed any of the lasalocid supplements. Rumen (P<.005) and plasma (P<.10) acetate to propionate ratios increased from day 22 to day 79 of the 98-day experiment. Acetate and propionate concentrations were correlated (P<.05). Growth rate was correlated (P<.01) with feed consumption and feed efficiency. Acetate and propionate concentrations were not correlated with plasma glucose, and no metabolite concentrations were correlated with growth or feed efficiency. Copyright © 1981. American Society of Animal Science . Copyright 1981 by American Society of Animal Science.

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