Effect of pharmacological concentrations of zinc oxide with or without theinclusion of an antibacterial agent on nursery pig performance

A study involving nine research stations from the NCR-42 Swine Nutrition Co mmittee used a total of 1,978 crossbred pigs to evaluate the effects of die tary ZnO concentrations with or without an antibacterial agent on postweani ng pig performance. In Exp. 1, seven stations (IA, MI, MN, MO, NE, ND, and OH) evaluated the efficacy of ZnO when fed to nursery pigs at 0, 500, 1,000 , 2,000, or 3,000 mg Zn/kg for a 28-d postweaning period. A randomized comp lete block experiment was conducted in 24 replicates using a total of 1,060 pigs. Pigs were bled at the 28-d period and plasma was analyzed for Zn and Cu. Because two stations weaned pigs at < 15 d (six replicates) and five s tations at > 20 d (18 replicates) of age, the two sets of data were analyze d separately. The early-weaned pig group had greater (P < 0.05) gains, feed intakes, and gain:feed ratios for the 28-d postweaning period as dietary Z nO concentration increased. Later-weaned pigs also had increased (P < 0.01) gains and feed intakes as the dietary ZnO concentration increased. Respons es for both weanling pig groups seemed to reach a plateau at 2,000 mg Zn/kg . Plasma Zn concentrations quadratically increased (P < 0.01) and plasma Cu concentrations quadratically decreased (P < 0.01) when ZnO concentrations were > 1,000 mg Zn/kg. Experiment 2 was conducted at seven stations (KY, MI , MO, NE, ND, OH, and OK) and evaluated the efficacy of an antibacterial ag ent (carbadox) in combination with added ZnO. The experiment was a 2 x 3 fa ctorial arrangement in a randomized complete block design conducted in a to tal of 20 replicates. Carbadox was added at 0 or 55 mg/kg diet, and ZnO was added at 0, 1,500, or 3,000 mg Zn/kg. A total of 918 pigs were weaned at a n average 19.7 d of age. For the 28-d postweaning period, gains (P < 0.01), feed intakes (P < 0.05), and gain:feed ratios (P < 0.05) increased when di etary ZnO concentrations increased and when carbadox was added. These respo nses occurred in an additive manner. The results of these studies suggest t hat supplemental ZnO at 1,500 to 2,000 mg Zn/kg Zn improved postweaning pig performance, and its combination with an antibacterial agent resulted in a dditional performance improvements.