Effects of the dietary inclusion of copper and(or) antibiotics on the performance of weanling pigs.

Five trials involving 518 pigs were conducted to determine the effects of the dietary addition of copper (0 or 250 ppm as copper sulfate) with and without antibiotics (55 ppm chlortetracycline, CTC, or 27.5 ppm virginiamycin VIR) on the rate and efficiency of gain and survival of early-weaned pigs. The experimental animals consisted of all pigs weaned from each of 67 litters at 28 +/- 2 days of age, regardless of weight or condition. In trials 1 through 4, single additions of copper, CTC or VIR to the corn-soybean meal-based diet improved (P less than .05) daily gains by 22, 22 and 17%, respectively, and feed to gain ratios by 5.1, 8.9 and 8.2% compared with those of pigs fed the unsupplemented diet during the 28-day trials. However, only the addition of copper to the diet increased (P less than .05) postweaning pig survival. Dietary inclusion of both copper and an antibiotic (CTC or VIR) further improved daily gains (P less than .05) by 10 to 11% and feed to gain ratios by 2 to 5% compared with the single addition of each antimicrobial agent. In trial 5, 125 ppm of copper were found to optimize daily gain and feed intake, whereas 250 ppm were required to maximize pig survival. These data demonstrate that high levels (125 to 250 ppm) of dietary copper increase the growth rate and reduce the incidence of mortality among weanling pigs. The data also indicate that the growth-promoting effects of copper and CTC, a broad spectrum antibiotic, or VIR, a gram-positive antibiotic, are additive in nature.