Limestone Granulometry and Vitamin D Supplementation in Brown Laying Hens: Implications for Performance, Egg Quality, Bone Health, Thermoregulation, and Behavior in a Hot Environment

This study evaluated the effects of limestone particle size and 25-hydroxycholecalciferol supplementation on performance, egg quality, digestive organ biometrics, bone characteristics, thermoregulatory responses, and behavior of brown laying hens reared under hot environmental conditions. The trial lasted five periods of 28 days. A total of 270 Lohmann Brown Lite hens (48 weeks old) were allocated in a completely randomized design with a 2 × 2 + 1 factorial arrangement, comprising two limestone particle sizes (MGD 0.568 mm and MGD 1.943 mm) and two supplementation levels of vitamin D (2760 IU and 1380 IU), plus a control diet, totaling five treatments with six replicates each. The dietary treatments were as follows: (1) control diet without vitamin D supplementation; (2) 250 g vitamin D with 100% fine limestone; (3) 125 g vitamin D with 100% fine limestone; (4) 250 g vitamin D with 50% fine + 50% coarse limestone; and (5) 125 g vitamin D with 50% fine + 50% coarse limestone. Productive performance, egg quality, organ biometrics, bone traits, thermoregulatory variables, and behavioral indicators were measured. Data were analyzed by ANOVA, followed by Tukey test (5%), considering the factorial model. There was no interaction between the factors for any parameter evaluated. There was an effect of shift on thermoregulatory variables. The other variables were not influenced by the treatments. These findings indicate that the tested limestone particle sizes can be incorporated in the diets of brown laying hens without affecting performance, egg quality, bone integrity, thermoregulation, or behavior, regardless of vitamin D supplementation, under hot climatic conditions.