Journal of Animal Science, Vol 72, Issue 4 1049-1058, Copyright © 1994 by American Society of Animal Science

JOURNAL ARTICLE

Effects of lasalocid and monensin plus tylosin on serum metabolic hormones and clinical chemistry profiles of beef steers fed a 90% concentrate diet

G. C. Duff, M. L. Galyean, M. E. Branine and D. M. Hallford
Department of Animal and Range Sciences, New Mexico State University, Las Cruces 88003.

Fourteen crossbred beef steers (average initial BW 313 +/- 13.1 kg) fed a 90% concentrate diet (as-fed basis) were used to evaluate effects of ionophores on serum metabolic hormones and clinical chemistry profiles. Treatments were no ionophore (C; four steers), lasalocid (L; 33 mg/kg of diet; five steers), and monensin (33 mg/kg of diet) plus tylosin (11 mg/kg of diet; MT; five steers). All steers were adapted to the 90% concentrate diet, after which treatments were applied and blood was sampled via jugular catheters on d 7, 35, 63, 91, and 119 of the trial at 0, 1, 2, 3, 4, 6, 8, and 10 h after feeding. Averaged over sampling days, serum glucose concentrations did not differ (P > .10) among treatments at any sampling time (treatment x sampling time, P < .05). Average across sampling days and times, serum growth hormone, insulin, cholesterol, and triglyceride concentrations did not differ (P > .10) among treatments. No major effects of ionophores were noted for serum enzymes or protein fractions. Averaged over sampling times within day (treatment x day interaction, P < .10), both L and MT increased (P < .05) serum Ca and Na concentrations on d 91 and 119 compared with C. Serum inorganic P was increased (P < .10) for L vs MT and for ionophore treatments compared with C (P < .10) on several occasions (treatment x day x sampling time interaction, P < .05). Results suggest that ionophores do not cause dramatic changes in serum metabolic hormones or clinical chemistry profiles; however, monensin and lasalocid altered serum minerals in beef steers fed a high-concentrate diet.