Effects of group-size-floor space allowance during the nursery phase of production on growth, physiology, and hematology in replacement gilts

The objective was to determine effects of nursery group-size-floor space allowance on growth, physiology, and hematology of replacement gilts. A 3 × 3 factorial arrangement of treatments was used wherein gilts classified as large, medium, or small (n = 2537; BW = 5.6 ± 0.6 kg) from 13 groups of weaned pigs were placed in pens of 14, 11, or 8 pigs resulting in floor space allowances of 0.15, 0.19, or 0.27 m²/pig, respectively. Pigs were weighed on d 0 (weaning) and d 46 (exit from nursery). The ADG was affected by group-size-floor space allowance × pig size (P = 0.04). Large- and medium-size gilts allowed the most floor space had greater (P < 0.05) ADG than similar size gilts allowed the least floor space but for small size gilts there was no effect (P > 0.05) of group size-floor space allowance. Mortality in the nursery was not affected (P > 0.05) by treatment, size, or treatment × size and overall was approximately 2.1%. Complete blood counts and blood chemistry analyses were performed on samples collected at d 6 and 43 from a subsample of gilts (n = 18/group-size-floor space allowance) within a single group. The concentration (P < 0.01) and percentage (P = 0.03) of reticulocytes was the least and red blood cell distribution width the greatest (P < 0.01) in gilts allowed 0.15 m² floor space (effects of treatment). Blood calcium was affected by treatment (P = 0.02) and concentrations for gilts allowed the greatest and intermediate amounts of floor space were greater (P < 0.05) than for gilts allowed the least floor space. Serum concentrations of cortisol were not affected by treatment × day (P = 0.27). Cortisol concentrations increased from d 6 to d 43 in all groups and were affected by day (P < 0.01) but not treatment (P = 0.53). Greater space allowance achieved by placing fewer pigs per pen in the nursery affected blood parameters and resulted in large- and medium-size replacement gilts displaying increased ADG. Further study will determine if these effects influence lifetime reproductive capacity and sow longevity.