Slow-Releasing Calcium Using Coating Technology Improves Egg Production and Quality by Enhancing Calcium Absorption in Aged Laying Hens.

Calcium (Ca) is one of the most critical macro-minerals in poultry nutrition, playing a fundamental role in skeletal integrity, eggshell formation, and numerous metabolic processes. In laying hens, particularly those in the late laying period, adequate calcium supply is essential because these birds must continuously mobilize Ca for eggshell mineralization while maintaining bone homeostasis. This study evaluated the effects of graded levels of slow-releasing calcium on performance, egg quality, nutrient retention, and blood mineral and bone turnover responses in aged laying hens. A total of 336, 54-week-old Hy-line brown laying hens were randomly allocated to four treatments (7 replications, 12 hens per cage) fed on a corn-soybean meal-based diet supplemented with slow-releasing calcium (SR-Ca) at 0% (CON), 0.25% (TRT 1), 0.5% (TRT 2), or 0.75% (TRT 3) for 12 weeks. Growth performance parameters, including body weight, average daily feed intake, and feed conversion ratio, were not significantly affected by dietary treatments (p > 0.05). Egg production rate and egg weight were also not significantly affected (p > 0.05) throughout the experimental period. The proportion of downgraded eggs did not differ significantly during 54-60 weeks (p > 0.05) but was significantly reduced from 61 to 66 weeks of age (p  0.05) during 54-60 weeks except for eggshell thickness which was improved by increasing levels of SR-Ca (p