Purdue University Agricultural Experiment Station Lafayette, Indiana
Mimeo AS--288 September, 1960 Final Report
A COMPARISON OF DIFFERENT LEVELS OF SPIRAMYCIN AND TYLOSIN ON GROWING-FINISHING SWINE 
J. H. Conrad, D. M. Hendricks and W. M. Beeson Department of Animal Science
In an experiment conducted last winter (Mimeo AS-284), five antibiotics or combinations of antibiotics resulted in statistically significant increases in rates of gain during the first 56 days of the experiment0 However* the gains were not statistically significant at the end of the complete experimental period when each lot had reached 200 pounds„ The improvement in feed efficiency ranged from a high of 5»2 percent to a low of 1„8 percent„ None of the treatments had a significant effect on carcass quality as measured by backfat thickness„
The continuous feeding of an antibiotic may change the character of the intestinal flora* so that after a time its effectiveness may be reduced0 For this reason* new antibiotics must be tested to find those that will most effectively improve gain and feed efficiency,, Another important aspect of this study is to determine the levels at which these various antibiotics will most effectively and most economically yield these benefits„	•
The objectives of this experiment were (l) to determine the effect of various levels of spiramycin and tylosin on gain and feed efficiency, (2) to compare the effects of aureomycin, spiramycin and tylosin and (3) to determine the effect of these antibiotics, at the levels fed, on back fat deposition,.
Experimental Plan
Eighty-eight Duroc weanling pigs averaging 27 pounds were divided into eight lots of eleven pigs each on the basis of sex, weight, litter and general appearance„ Each lot was confined to a concrete paved lot and fed a complete mixed ration„
The experimental treatments were as follows;
Lot 1—Control
Lot 2—Control plus aureomycin, 20 grams per ton to ICO pounds, 10 grams per ton from 100 to 200 pounds,
Lot 3—Control plus tylosin, 10 grams per ton to 100 pounds, 5 grams per ton from 100 to 200 pounds.
Lot 4—Control plus tylosin, 20 grams per ton to 100 pounds, 10 grams per ton from 100 to 200 pounds«
Lot 5—Control plus tylosin, 40 grams per ton to ICO pounds, 20 grams per ton from 100 to 200 pounds.
Lot 6—Control plus spiramycin, 10 grams per ton to 100 pounds, 5 grams per ton from 100 to 200 pounds•
Lot 7—Control plus spiramycin, 20 grams per ton to ICO pounds, 10 grams per ton from 100 to 200 poundSo
Lot 8—Control plus spiramycin, 40 grams per ton to 100 pounds, 20 grams per ton from 100 to 200 pounds•
17 The'" research reported in this mimeograph was supported in part by grants-in-aid from the following; American Cyanamid Co0, New York, N„ Y0, Eli Lilly and Co„, •hdianapolis, Indiana" and Rhcdia, Inc„, New York, N* Y„