Immunological studies on new rabbit paternal lines with different potentials for growth rate and resilience: pathways...

This study evaluated leukocyte and immune parameters in female rabbits and their kits from three genetic lines (R, RF, and RFLP) during their first reproductive cycle. The R line was selected for growth rate over 37 generations, the RF line was derived from elite R animals, and the RFLP was obtained by backcrossing the RF line with a maternal line (LP). In females, the total lymphocyte percentage decreased from the first AI to weaning (-15.8 percentage points; p < 0.001; MIXED model); granulocytes peaked at weaning (+12.4 percentage points greater than the AI and +4.4 percentage points greater than parturition; p < 0.01; MIXED model). The CD4⁺ /CD8⁺ ratio increased 53.4% (p < 0.001; MIXED model), and the haptoglobin concentration doubled (p < 0.001; MIXED model). RF and RFLP had higher total lymphocyte percentages than R did (+6.4 and +4.6 percentage points; p < 0.05; MIXED model). R females had lower CD4⁺ percentages and CD4⁺ /CD8⁺ ratios than RLFP females did (-3.4 percentage points and -24.4%; p < 0.05; MIXED model) but higher monocyte and granulocyte percentages (on average +0.9 and +4.1 percentage points; p < 0.05; MIXED model). At weaning, R kits had fewer T lymphocytes and CD4⁺ T lymphocytes than RF kits did (-8.1 and -6.1 percentage points; p < 0.05; GLM) and lower CD25⁺ and phagocytosis of heterophils than RFLP kits did (-0.8 and -1.2 percentage points; p < 0.05; GLM). The results suggest that creating a paternal line via elite animals (RFs) and backcrossing it with a robust line could improve immune status and stayability, offering insights into the impacts of rabbit breeding on immune health and reproductive success.