Further Trials on the Response of Earlyweaned Pigs and Rats to Diets Supplemented with Tylosin and High Levels of Copper

Abstract

Sixty-four, 3-week-old pigs and 128, 4-week-old rats were used to measure the effects on growth and feed efficiency of adding tylosin phosphate and a high level of copper sulfate to diets containing either 6% or 23% soybean meal and 23.5% protein. Each diet was provided without supplement, with copper (250 ppm) as copper sulfate, with tylosin phosphate (110 ppm) and with both copper and antibiotic. The pigs were fed for 6 weeks and the rats for 4 weeks. Tylosin increased feed intake and body weight gain of pigs fed the 6% soybean meal diet only, but with neither diet did tylosin have any effect on efficiency of feed conversion. Copper supplementation improved body weight gain of pigs fed both diets. This improvement was associated with an improvement of feed/gain from 1.93 to 1.83. Feed intake of pigs fed the 6% soybean meal diet was greater than that of those given the 23% soybean meal diet, but the greater feed/gain of the pigs fed the 6% soybean meal diet resulted in body weight gains of a similar magnitude in each group. The addition of tylosin to the diet decreased feed intake and growth rate of rats. The addition of copper improved the efficiency of feed conversion of the female rats but decreased efficiency of conversion of the male rats. Copper supplementation increased final liver copper levels of the pigs from 24 to 122 ppm (P<.05) and of the rats from 16 to 20 ppm (P<.05).