Effects of Zinc Oxide, Zinc Hydroxychloride, and Tribasic Copper Chloride on Nursery Pig Performance

Zinc hydroxychloride is expected to have higher bioavailability than Zn oxide, but research on the effects of Zn source with or without tribasic copper chloride is scarce. A total of 1,215 pigs (PIC 280×1050, initially 5.3 kg), housed under commercial conditions, were used in a 42-d growth trial to determine the effects of ZnO, Zn hydroxychloride (Intellibond Z, Micronutrients, Indianapolis, IN), and tribasic copper chloride (Intellibond C, Micronutrients, Indianapolis, IN) on growth performance. There were 9 pens per treatment and 27 pigs per pen. Pens were blocked by BW and assigned to 1 of 5 treatments in a randomized complete block design. Treatments consisted of added Zn as ZnO (3,000 ppm in phase 1 and 2,000 ppm in phase 2), Zn hydroxychloride (1,000 ppm in phase 1 and 2), and Cu (200 ppm), alone or in combination, as follows: 1) Cu only; 2) ZnO only; 3) ZnO and Cu; 4) Zn hydroxychloride only; and 5) Zn hydroxychloride and Cu. Experimental diets were fed from d 0-21 and a common diet was fed from d 21-42. Data were analyzed using PROC GLIMMIX of SAS. From d 0-21, there was a marginally significant interaction (P=0.073) between Zn source and Cu for ADG, where the addition of Cu to the ZnO diets increased ADG (209 vs. 201 ± 7.9g) but adding Cu to Zn hydroxychloride diets reduced ADG (187 vs. 198 ± 7.9g). Pigs fed added ZnO had greater ADG (205 vs 193 ± 7.15g, P=0.023), ADFI (316 vs 304 ± 8.03g, P=0.020), and BW on d 21 (9.8 vs. 9.5 ± 0.22kg, P=0.035) compared to those fed added Zn hydroxychloride. There was no evidence for differences in performance when added Cu and added Zn individually were compared, regardless of Zn source (P>0.10). From d 21-42, there was no evidence for differences in growth performance. Overall (d 0-42), feeding pigs diets with added ZnO resulted in greater ADFI (556 vs. 541 ± 8.25g, P=0.049) and marginally improved ADG (379 vs. 369 ± 5.92g, P=0.079) compared to Zn hydroxychloride. The results suggest there are little additive effects of added Zn and Cu and no major differences in performance between pigs fed diets with added Zn or Cu. Pigs fed diets with added ZnO had improved performance compared to those fed added Zn hydroxychloride which may be reflective of differences in source or level of added Zn.