Purdue University	Mimeo A.H.	118
Agricultural Experiment Station	September 18, 1953
Lafayette, Indiana
COMBINATIONS OF ANTIBIOTICS FOR GROWING AND FATTENING SWINE
G. W. Thrasher, T. W. Perry, and W. K. Beeson Department of animal Husbandry
Several distinct types of antibiotics have been shown to improve the gain of logs when incorporated in the ration at the proper level (5.0-7.5 mg./lb. feed), However, as yet it is not known if each antibiotic functions in the same manner ad whether certain combinations might have a complementary or additive effect, jiantitative studies have shown that when fed singly aureomycin, penicillin, and •.erramycin are equally effective; but the results on bacitracin have not been consistent. Therefore, it seemed desirable to study various combinations of these four antibiotics to find .out if they function differently when fed in mixtures.
In testing mixtures of antibiotics, it is important to use an effective mini-m level so that the true supplementary value can be determined. Therefore, in this experiment 6.0 mg. of antibiotic, or combination thereof, was used per pound of total ration.
Experimental Plan
Six lots of 12 Duroc pigs each averaging 30 pounds were fed in dry lot on an 11-plant basal ration (listed in Table 1) and a mineral mixture (40$ bonemeal, limestone, and 20$ iodized salt) free choice. The ration was fortified with oalcium pantothenate at recommended levels since this ration was found to be deficient in calcium pantothenate. Lot I served as a negative control and received only the basal ration. Lot II served as the positive control and received an op-•iiuni level (6.0 mg. per pound total ration) of aureomycin in addition to the *sal ration. The other four lots received various combinations of antibiotics onch that the total antibiotic present was 6.0 mg. per pound total ration (listed in Table 2).
All lots were fed for 112 days and then compared for final vreight, average :-ily gain, feed consumption and feed efficiency.