Assessment of endogenous calcium loss from different sources in 45-week-old Hy-Line Brown laying hens.

Objective: The study assessed the calcium (Ca) endogenous losses and digestibility in 45-week-old Hy-Line Brown laying hens fed diets incorporating different Ca-sourcing ingredients.

Methods: A total of 168 hens were randomly assigned to dietary treatments, with six replicates, and four hens were housed per cage. The seven diets included different Ca sources of monocalcium phosphate (MCP), dicalcium phosphate (DCP), limestone, corn, soybean, wheat bran, and a Ca-free diet. All diets included 0.3% Cr2O3 as a digestible marker as well. Hens were given ad-libitum access to feed and water. On day 3, fresh excreta and the ileal digesta were collected to analyze dry matter, Ca, and Cr2O3 for digestibility analysis.

Results: The Ca-free diets led to lower endogenous Ca losses at the ileum (p<0.05) compared to the Ca-supplemented groups. Among the Ca-sourcing diets, MCP resulted in higher Ca losses, whereas corn-based diets showed relatively lower losses at the ileum. Calcium losses at the excretory site were not significant, although the ileal losses were markedly higher (p<0.001), with diet-by-site interaction (p<0.05). Apparent and standardized ileal Ca digestibility were higher for inorganic sources (MCP, DCP, limestone) than for plant-based sources, with DCP showing greater digestibility (p<0.05).

Conclusion: Inorganic Ca sources resulted in increased endogenous Ca loss and digestibility compared to plant seed-based layer diets, with these losses varying depending on the specific measurement sites.