Intensive indoor versus outdoor swine production systems: genotype and supplemental iron effects on blood hemoglobin and selected immune measures in young pigs.

The objectives of Exp. 1 were to determine the effects of production system and genotype on pig performance and health. Sows were bred, gestated, farrowed, and lactated in either an intensive indoor or an intensive outdoor production system. The three dam genotypes of pigs used in each environment were PIC Camborough-15 (C-15), PIC Camborough Blue (CB), and Yorkshire x Landrace (YL). All pigs received 100 mg of iron dextran at d 3 of age. Pigs raised in the outdoor unit had higher blood hemoglobin (Hb) concentrations on d 28 of age than pigs raised indoors (11.5 +/- .22 vs 8.16 +/- .26 g/dL, P < .0001). Outdoor-reared pigs had more white blood cells (WBC) on d 3 than indoor-reared pigs (9.7 +/- .38 vs 8.04 +/- .38 cells/microL x 10(3), P < .05), but outdoor pigs had fewer WBC on d 28 of age than indoor-reared pigs (9.8 +/- .5 vs 11.1 +/- .45 cells/microL x 10(3), P < .05). Genetic lines did not differ in plasma immunoglobulin G (IgG) concentrations at 3 or 28 d of age. Environment and age influenced pig Hb levels and WBC numbers. The objectives for Exp. 2 were to determine whether C-15-405 pigs reared outdoors or indoors needed supplemental iron or whether they would receive enough environmental iron, and how the lack of supplemental iron may impact pig Hb and immunity. Indoor and outdoor pigs received either no supplemental iron, 100 mg, or 400 mg of iron dextran on d 3 of age. Blood percentage neutrophils and neutrophil: lymphocyte ratio were lower (P < .05) indoors, and natural killer cell (NK) activity was greater (P < .05) among indoor- than outdoor-reared pigs (NK % cytotoxicity: 15.6 +/- 2.3 vs 9.7 +/- 2.3). Outdoor-reared pigs that received no injected iron had similar Hb at d 28 of age as indoor-reared pigs that received 100 mg of iron dextran (11.1 +/- .36 vs 10.7 +/- .4 g/dL, P = .59). Supplemental iron may not be necessary in an outdoor production system. Outdoor-reared pigs had lower values for some immune measures, but they had similar survival rates as indoor-reared litters.