Work

Dietary calcium, non-phytate phosphorus, and electrolyte balance in low-protein diets for laying hens: Evaluating laying performance, egg quality, and nutrient utilization

Year: 2025

Type: article

Abstract: ABSTRACT The close relationship between nitrogen and macro-mineral nutrition in laying hens is well-established. Given the increasing promotion of low-protein diets, there is now a critical need to reassess the requirements and balance of calcium (Ca), non-phytate phosphorus (NPP), and electrolytes under such dietary conditions. We conducted a 3×3 factorial experiment using 756 Hy-Line Brown laying hens (49 weeks old). Birds were fed a 15.0% crude protein diet and allocated into nine groups (7 replicates of 12 hens each). The two main factors were: (1) Ca and NPP: Ca 3.50%, NPP 0.32% (NY/T 33-2004); Ca 3.91%, NPP 0.38% (Hy-Line Brown commercial management guide); Ca 4.20%, NPP 0.30% (Dutch CVB standards). (2) Dietary electrolyte balance (DEB) levels: 75 mEq/kg was added to or subtracted from the basal diet's DEB level (45, 120, and 195 mEq/kg). The interaction between Ca, NPP, and DEB affected blood creatinine and phosphorus (P) levels, apparent total tract digestibility (ATTD) of dry matter, crude protein, and duodenal mRNA expressions of Na + /K + -ATPase α1 subunit ( ATP1A1 ) and solute carrier family 2 member A9 ( SLC2A9, P < 0.05). Compared to the Ca 3.91%, NPP 0.38% group, the Ca 3.50%, NPP 0.32% group showed improved eggshell strength ( P < 0.001), albumen height ( P < 0.001), and Haugh unit ( P = 0.018). The elevated blood P and creatinine levels, duodenal ATP1A1 and SLC2A9 mRNA expression observed in the Ca 4.20%, NPP 0.30% group may indicate an increased physiological burden on renal function. The DEB 195 mEq/kg group showed enhanced dry matter and crude protein ATTD ( P < 0.05), and duodenal renal transient receptor potential vanilloid type 5 ( TRPV5 ) expression compared to the DEB 45 and 120 mEq/kg groups ( P = 0.024). Collectively, among the tested levels, the existing NY/T 33-2004 recommendations for Ca and NPP (Ca 3.50%, NPP 0.32%) remain effective in low-protein diets when combined with an elevated DEB of 195 mEq/kg.

Source: Poultry Science

DOI: 10.1016/j.psj.2025.106142