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Four experiments were conducted to determine the interactive effects of pharmacological amounts of Zn from ZnO and Cu from organic (Cu-AA complex; Cu-AA) or inorganic (CuSO(4)) sources on growth performance of weanling pigs. The Cu was fed for 4 (Exp. 1) or 6 (Exp. 2, 3, and 4) wk after weaning, and Zn was fed for 4 (Exp. 1) or 2 (Exp. 2, 3, and 4) wk after weaning. Treatments were replicated with 7 pens of 5 or 6 pigs per pen (19.0 ± 1.4 d of age and 5.8 ± 0.4 kg of BW, Exp. 1), 12 pens of 21 pigs per pen (about 21 d of age and 5.3 kg of BW, Exp. 2), 5 pens of 4 pigs per pen (20.3 ± 0.5 d of age and 7.0 ± 0.5 kg of BW, Exp. 3), and 16 pens of 21 pigs per pen (about 21 d of age and 5.7 kg of BW, Exp. 4). In Exp. 1 and 2, Cu-AA (0 vs. 100 mg/kg of Cu) and ZnO (0 vs. 3,000 mg/kg of Zn) were used in a 2 × 2 factorial arrangement. Only Exp. 1 used in-feed antibiotic (165 mg of oxytetracycline and 116 mg of neomycin per kilogram feed), and Exp. 2 was conducted at a commercial farm. In Exp. 3, sources of Cu (none; CuSO(4) at 250 mg/kg of Cu; and Cu-AA at 100 mg/kg of Cu) and ZnO (0 vs. 3,000 mg/kg of Zn) were used in a 3 × 2 factorial arrangement. In Exp. 4, treatments were no additional Cu, CuSO(4) at 315 mg/kg of Cu, or Cu-AA at 100 mg/kg of Cu to a diet supplemented with 3,000 mg/kg of Zn from ZnO and in-feed antibiotic (55 mg of carbadox per kilogram of feed). In Exp. 1 and 2, both Zn and Cu-AA improved (P < 0.001 to P = 0.03) ADG and ADFI. No interactions were observed, except in wk 1 of Exp. 2, where Zn increased the G:F only in the absence of Cu-AA (Cu-AA × Zn, P = 0.04). A naturally occurring colibacillosis diarrhea outbreak occurred during this experiment. The ZnO addition reduced (P < 0.001) the number of pigs removed and pig-days on antibiotic therapy. In Exp 3, ADFI in wk 2 was improved by Zn and Cu (P < 0.001 and P = 0.09, respectively) with no interactions. In wk 1, G:F was reduced by ZnO only in the absence of Cu (Cu × Zn, P = 0.03). Feeding Zn decreased fecal microbiota diversity in the presence of CuSO(4) but increased it in the presence of Cu-AA (Cu source × Zn, P = 0.06). In Exp. 4, Cu supplementation improved the overall ADG (P = 0.002) and G:F (P < 0.001). The CuSO(4) effect on G:F was greater (P < 0.001) than the Cu-AA effect. Our results indicate that pharmacological amounts of ZnO and Cu (Cu-AA or CuSO(4)) are additive in promoting growth of pigs after weaning.

Three experiments were conducted to evaluate effects of rice and other cereal grains on growth performance and health of weanling pigs. Pigs (1,008 in Exp. 1 and 3 and 1,004 in Exp. 2; 21 d old) with an initial BW of 5.8 ± 1.0 kg were used. Pigs in each experiment were divided into 3 BW blocks (heavy, medium, or light) in each of 4 rooms, resulting in 12 blocks per experiment. Each pen within a block had 20 or 21 pigs and equal sex distribution. Pens were allotted to dietary treatments in a randomized complete block design. Pigs were fed in a 4-phase feeding program with Phases 1 and 2 of 1 wk each and Phases 3 and 4 of 2 wk each. Diets were formulated to meet the same nutritional standards within each phase. In Exp. 1, effects of different cereal grains on pig performance and removal rate (mortality plus morbidity) were investigated. Pigs were fed 4 diets based on corn, barley, rolled oats, or rice as the only cereal grain. Over a 6-wk period, the ADG of pigs fed rice was greater (P < 0.01) than those pigs fed barley but not different from those pigs fed corn or rolled oats. Pigs fed corn or rice did not differ in ADFI, which was greater (P < 0.05) than those pigs fed barley. The overall removal rate of pigs fed rice or barley was reduced as compared with those pigs fed rolled oats (P < 0.05), and tended to be less than those pigs fed corn (P = 0.075). Experiment 2 was conducted to determine if the benefi ts observed in Exp. 1 could be obtained by feeding rice for less than 6 wk. Treatments included rice diets fed for 0, 1, 2, or 4 wk before changing to corn diets. All pigs received a common diet during wk 5 and 6. Pig performance and antibiotic treatments did not differ among dietary treatments. However, pigs fed rice for 1, 2, or 4 wk had a reduced overall removal rate (P < 0.05) compared with those fed corn. Experiment 3 was conducted to investigate if the amount of rice fed in wk 1 could be reduced without reducing pig performance. Rice replaced 0, 50, 75, or 100% of corn in Phase 1 diets. All pigs received a common diet from wk 2 to 6. No differences in pig performance or antibiotic treatments among dietary treatments were observed. However, pigs fed the diet with 100% rice had a reduced (P = 0.055) overall removal rate compared with pigs fed the corn diet. Generally, rice and corn improve pig performance as compared with barley. Rice can substitute for corn in nursery diets without detriment to pig performance and substantially reduces pig removals, even when fed for only 1 wk immediately after weaning.