Hypocalcemia during the transition period in dairy cows significantly affects health, reproduction, and milking performance. Although several effective strategies exist to regulate Ca metabolism, the interactions between Ca dynamics, inflammation, and dry matter intake remain poorly understood. This thesis investigates a combination of two commercially validated products; zeolite, a dietary P binding aluminosilicate, and calcidiol, an intermediate vitamin D metabolite. The objectives of our study were to evaluate the effects of the combination of zeolite and calcidiol on mineral metabolism and lactation performance and determine whether this combination is more effective compared to other strategies widely used in dairy farming. In a 2 × 2 factorial experimental design, we investigated the effects of feeding 92 parous close-up dry cows either a negative dietary cation-anion difference diet or a diet with zeolite, with or without calcidiol on milk production and mineral metabolism. Blood samples were collected at select timepoints during the periparturient period. Additionally, daily dry matter intake, milk yield, and rumination, as well as weekly milk composition, body condition scores, and body weights were measured. Data were analyzed using mixed effects models with repeated measures, if applicable, using SAS software. The results indicate that while the combination of zeolite and calcidiol did not improve milk yield in early lactation, zeolite alone significantly increased blood Ca concentrations postpartum.