Dietary vitamin D improves performance and bone mineralisation, but increases parasite replication and compromises gut health in Eimeria infected broilers.

Abstract

Coccidial infections may reduce fat soluble vitamin status and bone mineralisation in broiler chickens. We hypothesised that broilers infected with Eimeria maxima would benefit from increased dietary supplementation with vitamin D (vitD) or with 25-OH-D3 (25D3). Male Ross 308 chickens were assigned to diets with low (L) or commercial (M) vitD levels (1000 vs 4000 IU/kg) supplemented as D3 or 25D3. At d11 of age birds were inoculated with water (C) or 7000 E. maxima oocysts (I). Pen performance was calculated over the early (d1 - 6), acute (d7 - 10) and recovery periods (d11 - 14) post-infection (pi). At the end of each period 6 birds per treatment were dissected to assess long bone mineralisation, plasma levels of 25D3, calcium and phosphorus, and intestinal histomorphometry. Parasite replication and transcription of cytokines IL-10 and IFN-γ were assessed at d6 pi using quantitative PCR. Performance, bone mineralisation and plasma 25D3 levels were significantly reduced during infection (P < 0.05). M diets or diets with 25D3 raised plasma 25D3, improved performance and aspects of mineralisation (P < 0.05). Offering L diets compromised feed efficiency pi, reduced femur breaking strength and plasma phosphorous levels at d10 pi in I birds (P < 0.05). Contrastingly, offering M diets or diets with 25D3 resulted in higher parasite loads (P < 0.001) and reduced jejunal villi length at d10 pi (P < 0.01), with no effect on IL-10 or IFN-γ transcription. Diets with 4000 IU/kg vitD content or with 25D3 improved performance and mineralisation, irrespective of infection status, whilst 4000 IU/kg levels of vitD further improved feed efficiency and mineralisation in the presence of a coccidial infection.