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Response of Growing-Finishing Swine to Different Levels and Methods of Feeding Chlortetracycline¹

Ohio Agricultural Research and Development Center, Wooster

Abstract

The effect on performance of different levels of chlortetracycline in growing-finishing swine rations was observed over a 13-year period. In 21 drylot comparisons conducted in the same feeding unit, antibiotic significantly (P<.01) increased daily gain only from weaning to a live weight of 54 kg. Response in rate of gain did not decrease significantly with time, and the effectiveness of antibiotic supplementation decreased only when measured as the amount of feed saved per unit of gain from 54 kg. to market weight. The daily gain of control pigs significantly (P<.01) decreased with time, and, while the beneficial effect of antibiotic on efficiency of feed conversion appeared to decline, there was a concomitant increase (P<.01) in the efficiency of control pigs. During periods when the efficiency of feed conversion of control pigs was poorer, antibiotic supplementation resulted in a greater amount of feed saved.

In five trials the immediate and long-term effect of intermittent supplementation of chlortetracycline was observed. Supplementation ranged from every other week to as infrequently as 1 week out of 8. The addition of 22 mg. of CTC per kg. of feed during alternate 1- or 2-week periods significantly (P<.05) increased rate of gain over the entire feeding period, and performance was not significantly different from that of continuous supplementation at the same level. Levels of 44 mg. per kg. every fourth week or 88 mg. per kg. of feed every eighth week exerted an effect on performance similar to that which resulted from continuous intake of feed containing 11 mg. of CTC per kg.

¹ Published with the approval of the Associate Director as Journal Article No. 111-65.

² Present address: Pay Way Feed Mills, Inc., Kansas City, Missouri.

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