EFFECT OF CARBADOX (ANTIBIOTIC) SUPPLEMENTATION OF WEANLING SWINE DIETS VARYING IN PROTEIN AND (OR) LYSINE ON PERFORMANCE TO MARKET WEIGHT

Three experiments were conducted to study the effects of carbadox addition (55 ppm) to diets which varied in crude protein (16 or 18%) and/or lysine (.20% synthetic lysine added) content on the performance of weanling (7.5 kg) swine; and to monitor their performance to market weight (94 kg) after withdrawal of carbadox (33 kg). Initial diets were fed until pigs weighed 33 kg (period 1); then dietary crude protein (CP) was decreased by 3%, carbadox was removed, and in diets containing synthetic lysine, the addition was reduced to .10%. The addition of carbadox during period 1 improved, (P < .05) weight gains and feed:gain (F:G) ratio. Adding carbadox during period 1 lowered (P < .05) F:G ratio over the entire study (Exp. 1 .ANG. 2). In Exp. 3, adding carbadox to diets from which lysine was provided by either corn and soybean meal (18% CP) or by the addition of synthetic lysine to a lower protein diet (16% CP) resulted in similar performance. Over the entire study, ADG was increased (P < .05) by carbadox supplementation.