Quantitative genetic analyses of traits related to calcium and phosphorus metabolism in two different laying hen...

Phosphorus (P) and calcium (Ca) are essential minerals for laying hens. Phosphorus in plant feeds is mainly stored as phytate and needs to be released by the enzyme phytase. Due to the high requirement of Ca, laying hens exhibit limited endogenous phytate degradation and thus plant-P is available to a limited extent. Mineral P supplemented to laying hen feed reduces phytate degradation further and decreases myo-inositol release in the intestinal tract, which is known to have many functions in poultry metabolism. The focus of this study was the investigation of P and Ca metabolism in the peak period of egg production in commercial hybrid laying hens from Lohmann Selected Leghorn (LSL; n = 200) and Lohmann Brown (LB; n = 200) strains at the phenotypic and quantitative genetic level using data referring to blood plasma, ileal digesta, excreta, and eggs.

Population genetic analyses revealed larger genetic diversity in LB than LSL and substantial differentiation between the strains. The majority of Ca and P metabolism traits differed significantly in trait mean or variance between the two strains. The LB strain showed more trait variation at the phenotypic and quantitative genetic levels. Moderate to high and significant heritabilities were estimated for myo-inositol in the plasma ([Formula: see text] = 0.43 for LSL and [Formula: see text] = 0.36 for LB), ileum digesta ([Formula: see text] = 0.60 for LB; not estimable for LSL) and egg ([Formula: see text] = 0.69 for LSL and [Formula: see text] = 0.55 for LB), and for the Ca concentration in the plasma ([Formula: see text] = 0.27 for LB; not estimable for LSL). Noticeably significant phenotypic correlations between the traits of P and Ca metabolism measured in excreta, plasma, and ileal digesta were present in both strains.

The study provided a comprehensive insight into P and Ca metabolism under standardized conditions in the two commercial laying hen strains LSL and LB during egg laying. Differences between the strains were present at the phenotypic and quantitative genetic level. Thereby, the hens' genetics appeared to be a relevant driver of P and Ca metabolism, with LB showing more variability. The study confirmed population genetic differences between the strains. Despite the detected strain differences, significant correlations among the traits of P and Ca metabolism indicate that the general relationships between traits are comparable in both strains.