Circadian rhythms regulate a wide array of metabolic and physiologic activities in a periodicity of about 24 hours. Calcium (Ca) is a critical nutrient which ensures the production of egg with good quality eggshell.

The serum calcium exhibits a circadian rhythm which varied with the changed light: dark cycle in laying hens. The dynamic feeding time of Ca coupling with circadian rhythms may affect serum trace minerals concentration in laying hens.

No attempt was made to determine relationships between circadian rhythms and calcium transport in laying hens.

Researchers in the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences conducted a 70-day experiment to explore the effects on serum Zn concentration, gene expression levels of circadian clock, Ca transporters and oxidative status in laying hens (Brown Hyline, 180 birds, 41-weeks) under the circadian feeding regimes with low Ca (3.2%) diets and high Ca (3.6%) diets in daily cycles.

In their study, compared with the CON group (Control Ca, diets contained 3.4% Ca at both 0730 and 1530?h): the serum zinc in HL group (High-low Ca, diets contained 3.6%–3.2% Ca respectively) increased at 2000 h, but lower at 1600 h in LH group(Low-high Ca, diets contained 3.2%–3.6% Ca respectively).

In jejunum, circadian clock genes including CLOCK and BMAL1 expression of HL group were down-regulated at 0000 h and 1600 h, as well as CLOCK, BMAL1, Cry2, Per3 and calcium transporter gene NCX1 in LH group at 2000 h.

In kidney, CLOCK, Cry1, Cry2 and Per3 of LH group were upregulated at 0400 h, CLOCK at 0000 h as well, while CLOCK at 2000 h were down-regulated.

In conclusion, the dynamic circadian calcium feeding regime affected circadian rhythms of serum zinc concentration as well as the expression of certain genes related to the circadian clock, calcium transport and antioxidative capacity, and circadian calcium feeding regimes may therefore be considered with regard to improving the calcium usability.

The study entitled “Circadian calcium feeding regime in laying hens related to zinc concentration, gene expression of circadian clock, calcium transporters and oxidative status” was published in Journal of Trace Elements in Medicine and Biology, details can be found at https://www.sciencedirect.com/science/article/pii/S0946672X17308520.

It was supported by the National Key Research and Development Program of China.

Contact: WU Xin

E-mail: wuxin@isa.ac.cn

Institute of Subtropical Agriculture, Chinese Academy of Sciences