Masters Theses

Date of Award


Degree Type


Degree Name

Master of Science


Animal Science

Major Professor

J. B. McLaren

Committee Members

Haley M. Jamison, Curtis C. Melton


Two trials, involving 40 yearling steers at the University of Tennessee Blount Farm and 60 yearling heifers at Ames Plantation were conducted to evaluate two methods of delivering monensin sodium (Rumensin) to cattle grazing pasture. Salt and a salt-cottonseed meal mixture, each containing ICQ mg of Rumensin per oz, were fed free-choice and salt intake, Rumensin intake and animal performance were compared to that of cattle fed salt free-choice. Average daily consumption of Rumensin was about.70 mg per animal per day in both trials when mixed with loose salt at the rate of 100 mg per oz. Average daily consumption was 111 mg per animal when suppled at the rate of 100 mg per oz of a salt-cottonseed meal mixture (1:1) at Ames Plantation. Average daily salt and Rumensin intake (calculated on a moisutre constant basis) varied from week to week and tended to increase as elapsed days of supplementation increased. Increasing the Rumensin level in the carriers from 100 to 200 mg per oz during the latter periods of the trial increased (P < .05) Rumensin intake. However, salt consumption of cattle consuming the salt-cottonseed meal Rumensin mixture was decreased. Rate of gain was similar for the control animals and the Rumensin-supplemented animals in the Blount trial (P > .05). However, Rumensin supplemented animals increased in weight slower (P < .05) than the control animals at Ames Plantation. Two questions with respect to efficacy of these two mixtures as delivery systems for Rumensin to cattle on pasture were identified in this study. If variation of daily Rumensin intake inhibits the ability of Rumensin to change rumen VFA proportions, this addition of Rumensin to salt as a method of delivering Rumensin to cattle on pasture may not be satisfactory. Higher levels of cottonseed-meal may result in a more palatable mixture and increased Rumensin intake, but the effect of such mixtures on salt consumption needs study. In this study, Rumensin intake using either of the two delivery systems (salt + Rumensin and salt + cottonseed meal + Rumensin) was within the effective dosage level (50 to 200 mg per animal per day). When the Rumensin content was increased to 200 mg per oz of carrier, average daily intake was within the range of the most efficient dosage level (100 to 200 mg per animal per day) which was observed when.daily intake was controlled.

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