Anti-CaSR egg yolk antibody improves calcium absorption and bone mineral deposition through intestinal CaSR...

Calcium-sensing receptor (CaSR) is a key negative regulator of intestinal calcium transport, and targeting CaSR represents a promising strategy to improve mineral retention. Egg yolk antibodies can be used as a feed-based approach to modulate intestinal physiological processes. Therefore, this study aimed to evaluate whether anti-CaSR egg yolk antibodies could modulate intestinal calcium transport and enhance calcium and phosphorus retention in broilers. Hy-Line Brown laying hens were immunized over a 4-week period with either a CaSR peptide vaccine or an adjuvant control (without CaSR peptide). High titers of anti-CaSR antibodies were detected in egg yolk at week 5, indicating successful antibody production. The egg yolks were subsequently collected, freeze-dried into powder, and incorporated into broiler diets at a supplementation level of 0.5%. A 14-day feeding trial demonstrated that dietary supplementation with anti-CaSR antibodies markedly increased serum calcium and phosphorus levels, improved apparent ileal digestibility of both minerals, and enhanced tibial ash as well as calcium and phosphorus deposition. Mechanistically, dietary supplementation with anti-CaSR antibodies upregulated components of the transcellular calcium transport pathway, including transient receptor potential vanilloid 5 (TRPV5) and calbindin-D28k (CaBP-D28k), and elevated serum calcitriol level, indicating activation of a vitamin D-dependent regulatory axis. Furthermore, anti-CaSR increased the expression of key phosphate transporters in both the intestine and kidney, supporting its broader role in mineral homeostasis. These findings demonstrate that anti-CaSR antibodies enhance the expression of calcium and phosphorus transport proteins, thereby improving mineral retention and promoting bone mineralization in broilers.