Quantitative feed restriction rather than caloric restriction modulates the immune response of growing rabbits.
BACKGROUND
Short-term feed restriction strategies are used in rabbits to reduce postweaning digestive disorders, but little is known about the involvement of the immune system in these beneficial effects.


OBJECTIVE
In the present study, the consequences of feed and energy restriction on immune response were investigated.


METHODS
At weaning, 320 male and female rabbits were assigned to 4 groups differing in dietary digestible energy (DE) concentrations and intake levels: a low-energy ad libitum-feed (LE100) group, a low-energy restricted-feed (LE75) group, a high-energy ad libitum-feed (HE100) group, and a high-energy restricted-feed (HE75) group. The high-energy groups consumed 10.13 MJ DE/kg of feed, whereas the low-energy groups consumed 9.08 MJ DE/kg (formulated values). Intake amounts for the restricted groups were 75% those of the ad libitum groups. Rabbits consumed these diets until age 63 d, after which they consumed feed ad libitum for 9 d. Ten rabbits per group and per age were killed at ages 42, 50, 63, and 72 d. Spleens and appendixes were weighed; Peyer's patch surface area was determined by image analysis; plasma total immunoglobulin (Ig) G and anti-ovalbumin IgG; and fecal and plasma IgA concentrations were determined by ELISA; and ileal expressions of cytokines were measured by quantitative reverse transcriptase-polymerase chain reaction at ages 50 and 63 d.


RESULTS
The relative weight and size of the lymphoid organs were not affected by treatments. Concentrations of plasma total IgA (-41% at 63 d and -29% at 72 d), IgG (-22% at 72 d), and anti-ovalbumin IgG (-41% at 63 d) were lower with feed restriction. Fecal IgA concentrations were lower with quantitative restriction (-40%, -52%, and -65% at age 42, 50, and 63 d, respectively) and energy restriction (-56%, -46%, and -73% at ages 50, 63, and 72 d, respectively). Feed-restricted rabbits tended to have greater expressions of interleukin (IL) 1β and IL-2 and lower expressions of tumor necrosis factor α (P < 0.1).


CONCLUSIONS
These results demonstrated that, in rabbits, restriction and, to a lesser extent, dietary energy concentration modulate gut immunity.
INRA (Institut National de la Recherche Agronomique), GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Castanet-Tolosan, France; Université de Toulouse, INP (Institut National Polytechnique), ENSAT (Ecole Nationale Supérieure Agronomique de Toulouse), GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Castanet-Tolosan, France; Université de Toulouse, INP, ENVT, GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Toulouse, France;
Christelle
C
Knudsen
INRA (Institut National de la Recherche Agronomique), GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Castanet-Tolosan, France; Université de Toulouse, INP (Institut National Polytechnique), ENSAT (Ecole Nationale Supérieure Agronomique de Toulouse), GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Castanet-Tolosan, France; Université de Toulouse, INP, ENVT, GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Toulouse, France;
Sylvie
S
Combes
CCPA, Janzé, France;
Christophe
C
Briens
Evialis, Vannes, France;
Joël
J
Duperray
TECHNA, Coueron, France;
Gwenaël
G
Rebours
Sanders, Bruz, France;
Jean-Marc
JM
Salaun
ITAVI, UMT BIRD (Unité Mixte Technologique Biologie et Innovation pour la Recherche et le Développement en aviculture), Centre INRA de Tours, Nouzilly, France;
Angélique
A
Travel
INZO, Chierry, France;
Delphine
D
Weissman
INRA (Institut National de la Recherche Agronomique), GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Castanet-Tolosan, France; Université de Toulouse, INP (Institut National Polytechnique), ENSAT (Ecole Nationale Supérieure Agronomique de Toulouse), GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Castanet-Tolosan, France; Université de Toulouse, INP, ENVT, GenPhySE (Génétique, Physiologie et Systèmes d'Elevage), Toulouse, France; thierry.gidenne@toulouse.inra.fr.
Thierry
T
Gidenne
INRA, UMR 1331, Toxalim, Toulouse, France; and Université de Toulouse, INP, UMR 1331, Toxalim, Toulouse, France.
Isabelle P
IP
Oswald
D000821:Animal Feed; D000818:Animals; D001835:Body Weight; D031204:Caloric Restriction; D004032:Diet / Q000662:veterinary; D002149:Energy Intake; D005260:Female; D007082:Ileum / Q000276:immunology; D007109:Immunity / Q000502:physiology*; D007070:Immunoglobulin A / Q000097:blood*; D007074:Immunoglobulin G / Q000097:blood*; D053583:Interleukin-1beta / Q000097:blood / Q000235:genetics; D007376:Interleukin-2 / Q000097:blood / Q000235:genetics; D008297:Male; D010047:Ovalbumin / Q000097:blood; D011817:Rabbits; D013154:Spleen / Q000276:immunology; D014409:Tumor Necrosis Factor-alpha / Q000097:blood / Q000235:genetics; D014886:Weaning
D007070:Immunoglobulin A; D007074:Immunoglobulin G; D053583:Interleukin-1beta; D007376:Interleukin-2; D014409:Tumor Necrosis Factor-alpha; D010047:Ovalbumin
energy intake; feed restriction; health; immune response; rabbit