Feed restriction reduces IgA levels and modifies the ileal cytokine expressions in growing rabbits

Postweaning short-term restriction strategies are commonly used in rabbit breeding to reduce mortality and morbidity. However, little is known about the implications of the immune system in that reduction. This work studied the consequences of feed restriction and dietary digestible energy (DE) concentration on the local immune response, according to a 2x2 factorial design: 320 animals were alloted at weaning (35 days of age) in four groups, with two diets differing in DE (10.13 vs 9.08 MJ DE/kg) and two intake level (ad libitum "AL" or restricted at 75% of AL). Ten animals per group and per age were sacrificed at 50 and 63 days of age. Feces, blood and ileum were collected. Fecal and plasmatic IgA levels were determined by ELISA and ileal cytokine expressions were measured by RT-qPCR. Fecal IgA levels were reduced by 58% with feed restriction (P<0.001) and increased by 47% with a high energy diet (P<0.01), regardless of the age. Plasmatic IgA levels were only affected by feed restriction at 63 days of age (-48%, P<0.01). Cytokine expressions were similar for both ages and diets, but were affected by feed restriction with a higher expression of IL-1β and IL-2 (respectively +30%, P<0.05 and +77%, P=0.07) and a 15% lower expression of TNF-α (P=0.08) compared to AL animals. Thus, feed restriction and, to a lesser extent, the dietary energy level modulate gut immunity.