Effect of Water Salinity, Dietary Potassium Carbonate, Vitamin D<sub>3</sub> Levels, and Vitamin D<sub>3</sub> Form (1α-Hydroxycholecalciferol) on Calcium and Phosphorus Digestibility and Tibia Bone Properties in Broilers

This study aimed to assess the joint impact of water salinity, K₂CO₃, vitamin D₃ levels, and inclusion of 1α-hydroxycholecalciferol (1αOHD3) on broiler tibiae. A total of 1200 one-day-old male Ross broiler chickens were given four different levels of vitamin D₃ (2000, 5000, 7000, and 5000 IU + 20 µg/kg 1αOHD₃), three levels of water salinity (WS) (low, moderate, high), and two concentrations of K₂CO₃ (0 and 2.5 g/kg). Supplementation with 1αOHD₃ reduced body weight and increased the feed conversion ratio throughout the experimental period. Birds consuming water with low salinity up to 21 days of age presented significantly lower body weight and feed intake, but a higher feed conversion ratio. Water consumption was reduced by increasing WS during the first week, but increased during the grower and finisher periods. K₂CO₃ lowered water consumption. Higher WS increased litter moisture by 35% and 27% at 14 and 28 days of age, along with alkaline phosphatase (ALP) activity, but reduced plasma Ca, P, and K. Inclusion of K₂CO₃ lowered plasma Ca, P, and ALP activity at 14 days, but increased plasma K. Apparent total tract retention (TTR) of P decreased by increasing D₃ levels and adding 1αOHD₃ on day 14. Increasing WS linearly decreased TTR of P on day 14 and TTR of Ca and P on day 28, causing a significant loss of tibia ash, Ca, and P. Tibial shear force was reduced by increasing dietary D₃ on day 28. Tibial shear force and stress were decreased, while its elongation was improved, by increasing WS at 14 days of age. In conclusion, high WS lowered bird weight gain, increased water consumption and litter moisture, and reduced TTR of Ca and P, which significantly diminished tibia ash, Ca, and P, as well as tibial mechanical properties.