INFLUENCE OF FEED RESTRICTION AND ZINC OXIDE NANOPARTICLES SUPPLEMENTATION ON GROWTH PERFORMANCE, BLOOD BIOCHEMISTRY, INTESTINAL MORPHOLOGY AND CECAL FERMENTATION PARAMETERS OF GROWING RABBITS

The present study investigated the response of growing rabbits in terms of growth performance, serum biochemical, intestinal morphology, and caecal fermentation parameters to feed restriction and zinc oxide nanoparticles (ZnO-NPs) supplementation. A total of 60 New Zealand male rabbits were randomly distributed into 6 groups: AL-0 (fed ad libitum + fresh water as control); AL-15 and AL-30 (ad libitum + water supplemented with ZnO-NPs in water, 15 and 30 mg/L, respectively); and R-0, R-15 and R-30 were the same as the first 3 groups but with restricted feeding regime. Rabbits fed ad libitum and supplemented with ZnO-NPs (15 mg/L) showed the highest body weight with no significant difference from AL- fed groups or R-0. Feed conversion ratio (FCR) showed no difference among the different experimental groups (P > 0.05). ZnO-NPs supplementation reduced the serum lipid profile parameters, catalase enzyme in R-30, superoxide dismutase in AL-15 and AL-30 while increased serum malondialdehyde (MDA) in both ad libitum and restricted rabbits. ZnO-NPs administration resulted in lower caecal ammonia in AL-30 compared to its control (AL-0) as well as the content of individual volatile fatty acids (VFAs) (acetate, butyrate and propionate) (P < 0.05). Ileum morphological parameters (mucosal length, villi length, and goblet cell number) were modified in response to the feed restriction and ZnO-NPs addition. In conclusion, feed restriction program applied in this experiment altered rabbit growth performance (final body weight and weight gain with no differences in FCR), improved ileum morphology while had no significant effect on caecal fermentation (VFAs profile) or microbiological parameters. ZnO-NPs supplementation in both levels (15 and 30 mg/L) differently modulated serum lipid profile, antioxidant enzymes and MDA, VFAs profile in cecum and ileal morphology with no differences in rabbit growth performance. VPLIV OMEJITVE KRME IN DODAJANJA NANODELCEV CINKOVEGA OKSIDA NA RASTNO ZMOGLJIVOST, BIOKEMIJO KRVI, ČREVESNO MORFOLOGIJO IN PARAMETRE CEKALNE FERMENTACIJE RASTOČIH KUNCEV Izvleček: V tej študiji smo proučevali odziv rastočih kuncev na omejitev krme in dodajanje nanodelcev cinkovega oksida (ZnO-NP) v okviru uspešnosti rasti, biokemičnih parametrov v serumu, morfologije črevesja in fermentacije v slepem črevesu. Skupno 60 samcev novozelandskih kuncev je bilo naključno razdeljenih v 6 skupin: AL-0 (krmljenje ad libitum + sladka voda kot kontrola); AL-15 (krmljenje ad libitum + voda z dodatkom 15 mg/l ZnO-NP) in AL-30 (krmljenje ad libitum + voda z dodatkom 30 mg/l ZnO-NP). Skupine R-0, R-15 in R-30 so bile enake prvim trem, vendar z omejenim režimom krmljenja. Kunci, hranjeni ad libitum z dodatkom ZnO-NP (15 mg/L), so imeli največjo telesno maso brez statistično značilnih razlik v primerjavi s skupinami AL-0, AL-30 in R-0. Razmerje pretvorbe krme (FCR) se med različnimi poskusnimi skupinami ni razlikovalo (P > 0,05). Dodajanje ZnO-NP je vplivalo na zmanjšanje parametrov lipidnega profila v serumu, tj. encim katalaza pri R-30 in superoksid dismutaza pri AL-15 in AL-30, medtem ko se je vsebnost serumskega malondialdehida (MDA) povečala tako pri kuncih, krmljenih ad libitum, in kuncih z omejenim režimom krmljenja. Dajanje ZnO-NP je pri AL-30 v primerjavi s kontrolo (AL-0) povzročilo znižanje vsebnosti amonijaka v slepem črevesu ter vsebnosti posameznih hlapnih maščobnih kislin (acetata, butirata in propionata) (P < 0,05). Kot odgovor na omejitev krme in dodajanje ZnO-NP so se spremenili morfološki parametri ileuma (dolžina sluznice, dolžina resic in število čašastih celic). Ključne besede: omejitev krme; rast; kunci; nanodelci Zn oksida