Effect of Iron Treatment at Weaning on Growth Performance in Nursery Pigs Fed Diets Supplemented with Copper

Despite receiving iron at birth, many pigs, particularly those fastest growing, are anemic at weaning. Dietary copper stimulates growth but inhibits iron absorption, perhaps exacerbating the anemic condition. The objective was to determine the effect of iron at weaning on growth in pigs fed diets supplemented with copper. Pigs received 100 mg iron i.m. within 24 h after birth. At weaning (21 d of age) pigs were classified as large (n = 72; 8.3 ± 0.1 kg) or small (n = 72; 5.8 ± 0.1 kg) and one-half of pigs of each size received a second i.m. 100 mg iron injection. Pigs were placed three pigs/pen and allotted to a 2 x 2 x 2 factorial arrangement of treatments, main factors being size (large vs. small), iron injections (one vs. two) and diet (control vs. 250 ppm copper) (n = 6/treatment combination). Growth was determined, and hematocrit assessed (one pig/pen) at weaning (d 0) and d 7 and 49 post-weaning. At d 0 (P < 0.01) but not d 7 (P = 0.16) or 49 (P = 0.99), hematocrit was greater for small (35.4%) than large (30.9%) pigs (size x day, P < 0.01). Hematocrit was greater (P = 0.08) on d 7 in pigs receiving two injections (37.6%) compared to those that received one (34.3%), but was similar (P = 0.97) between groups on d 0 and 49 (injection number x day, P = 0.08). Between d 0 and 7, ADG in copper-fed pigs was greater (P = 0.06) for animals receiving two (103.0 g/d) vs. one (56.8 g/d) injection (injection number x diet, P = 0.06). Pigs fed copper had greater (P < 0.01) ADFI than control-fed pigs (254.2 vs. 220.3 g/d) from d 0 to 7. Gain-to-feed ratio (d 0 to 7) was affected by injection number x diet (P = 0.06) and for copper fed animals was greater (P = 0.06) for pigs receiving two (0.39) vs. one (0.22) injection. From d 0 to 49, ADG (P = 0.05) and ADFI (P = 0.04), but not G:F (P = 0.74) were affected by injection number x diet and within copper-fed individuals ADG (531.8 vs. 476.9 g/d; P = 0.07) and ADFI (929.5 vs. 833.3 g/d; P = 0.05) was greater for pigs receiving two vs. one injection. A second injection of iron at weaning enhanced growth performance in pigs consuming diets supplemented with dietary copper. (National Pork Board Project #17-052)