Effects of phytase and 25-hydroxycholecalciferol supplementation in broilers fed calcium-phosphorous deficient diets, with or without Eimeria challenge, on growth performance, body composition, bone development, and gut health

The study evaluated the effects of nutritional strategies on broilers challenged with <i>Eimeria</i> from d 14 to 26. A total of 840 Cobb male broilers were fed five diets in a 2 × 5 factorial arrangement: 1) nutrient adequate diet (PC; 0.84% calcium [Ca], 0.42% available phosphorus [avP]); 2) Ca-P deficient diet (NC; 0.64% Ca, 0.22% avP); 3) NC + 1500 FTU/kg phytase of diet (NC + PHY); 4) NC + 5000 IU/kg 25-Hydroxycholecalciferol of diet (NC + 25OHD); and 5) NC with both supplements (NC + PHY + 25OHD), with and without <i>Eimeria</i> challenge. All treatments had six replicate cages with 14 birds per cage. At 5 days post inoculation (DPI), the challenged birds exhibited higher serum fluorescein isothiocyanate-d (FITC-d) levels than the unchallenged birds (<i>P</i> < 0.001). The NC + PHY and NC + PHY + 25OHD groups exhibited lower FITC-d levels compared to the NC + 25OHD group (<i>P</i> = 0.012). Significant interaction effects between <i>Eimeria</i> challenge and dietary treatments were observed on various parameters. During 0 to 6 and 0 to 12 DPI, <i>Eimeria</i> challenge resulted in decreased the body weight gain (BWG) (<i>P</i> < 0.05) but had a negative effect on the feed conversion ratio (FCR) in birds compared to the unchallenged group (<i>P</i> < 0.05). Reducing Ca and avP levels in the diet (NC) did not adversely affect BWG, but negatively impacted FCR, bone ash weight, ash concentration, and femur bone microstructure parameters (<i>P</i> < 0.05). On 12 DPI, <i>Eimeria</i> challenge led to decreased tibia bone weight, bone volume, fat-free bone weight (FFBW), and ash weight of birds (<i>P</i> < 0.05). Supplementation with phytase alone or in combination with 25OHD improved growth performance, gut permeability, bone ash and bone microstructure parameters in birds (<i>P</i> < 0.05). However, the group fed 25OHD alone showed enhancements on growth performance, mineral apposition rate (MAR), bone ash concentration and ash percentage of the birds (<i>P</i> < 0.05). In conclusion, lowering Ca and avP levels in the diet negatively affected FCR and bone development but did not affect intestinal integrity in broilers. Dietary supplementation of phytase, 25OHD, or phytase in combination of 25OHD could enhance the growth performance and bone quality of broilers infected with <i>Eimeria</i>. Notably, the benefits of phytase supplementation were generally more pronounced than those associated with 25OHD supplementation; however, the combination of phytase and 25OHD could induce optimum effects.