Growth performance and hematology characteristics in pigs treated with iron at birth and weaning and fed a nursery diet supplemented with a pharmacological level of zinc oxide

Objective: To determine effects of an iron dose at weaning on growth and hematology in pigs fed zinc. Materials and methods: Weaned pigs (n = 144) were allocated to treatments in a 2 × 2 × 2 factorial arrangement (6 pens/treatment, 3 pigs/pen), with factors being pig size (large or small); number of 100 mg iron dextran doses (1 [birth] or 2 [birth and weaning]); and dietary zinc (100 or 2000 ppm). Average daily gain (ADG), feed intake (ADFI), and gain to feed ratio (G:F) were determined. Blood samples were collected at weaning and 7 and 49 days post-weaning. Results: Anemia (hemoglobin < 9.0 g/dL) at weaning tended to be greater (P = .07) for large pigs and hemoglobin (P = .02) and hematocrit (P = .05) were greater in small pigs. Hematology was largely unaffected by number of iron doses or diet. Large pigs displayed greater ADG (P < .001) but poorer G:F (P = .002). Zinc-supplemented pigs had greater (P = .002) ADG and G:F from day 0 to 21. From day 22 to 49, G:F (P = .005) was greater for controls. Overall, zinc tended to increase ADFI in large (P = .09) but not small (P = .46) pigs. Growth was largely unaffected by number of iron doses. Implications: Anemia at weaning was common, especially for larger pigs, but was not exacerbated by zinc. An iron dose at weaning had minimal effects on growth. Dietary zinc enhanced growth early post-weaning but effects waned as pigs aged.