95
Comparative effects of dietary Cu, Zn, essential oil, and chlortetracycline on nursery pig growth performance
Weaned pigs (n=350; PIC 1050; initially 6.05 kg) were used in a 47-d study to compare the effects of feeding antibiotic alternatives (Cu, Zn, and essential oil), alone or in combination, on nursery pig performance. Pigs were allotted to pens at weaning (d 0) and fed a common starter diet with no antimicrobial for 5 d prior to diet treatments. On d 5, pens of 5 pigs were allotted to 1 of 10 dietary treatments balanced on average pen weight in a randomized block design with 7 replications/treatment. Dietary treatments were arranged in a 2×2×2+2 factorial with main effects of added Cu from CuSO4 (0 vs. 125 ppm Cu), added Zn from ZnO (0 vs. 3,000 ppm Zn from d 5 to 12 and 2,000 ppm Zn from d 12 to 33), and essential oil (0 vs. 0.1% Regano EX containing origanum oil; Ralco Animal Nutrition, Marshall, MN). The 2 additional treatments were sub-therapeutic and therapeutic levels of chlortetracycline (CTC; 55 or 441 mg/kg). All diets contained 16.5 ppm Cu and 165 ppm of Zn from the trace mineral premix. Pigs were fed experimental diets from d 5 to 33 after weaning followed by a common corn-soybean meal–based diet without any antimicrobial, essential oil, or pharmacological levels of Cu or Zn from d 33 to 47. To comply with FDA guidelines, CTC was removed on d 19 from the diet of pigs fed 441 mg/kg CTC, then added again from d 20 to 33. During the treatment period, essential oil had no effect (P>0.05) on ADG or ADFI whereas pharmacological levels of Cu, Zn, and CTC increased (P=0.003, 0.001, linear 0.028, respectively) ADG with coinciding increases (P=0.055, 0.006, and linear 0.079, respectively) in ADFI. Copper, Zn, and CTC had no effect (P>0.05) on G:F. Essential oil decreased (P=0.009) G:F and a Cu × essential oil interaction (P=0.024) was observed due to poorer than expected G:F of pigs when Cu was fed in combination with essential oil. The dietary treatments had minimal carryover effects on subsequent nursery pig growth performance. Overall from d 5 to 47, Cu increased (P=0.018) ADG, Zn increased (P<0.05) ADG and ADFI, and essential oil tended to decrease (P=0.086) overall G:F. In conclusion, increased levels of dietary Cu, Zn, or CTC improved weanling pig performance while essential oil elicited no growth performance benefits.
Keywords: nursery pig, antibiotic, essential oil