The circadian clock programs daily rhythms and coordinates multiple metabolic processes, including lipogenesis, lipid catabolism, sterol metabolism, and gluconeogenesis.

Pervious study found that changing daily rhythm of food ingestion would change rhythms of metabolites. When changing daily rhythm of methionine ingestion, 25 % of the total methionine ingested in the morning, and 75 % at night, the serum total cholesterol (TC), triglyceride (TG), total protein (TP), and calcium of laying hens are significant lower in early morning.

Recently, researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences investigated the diurnal variation of the circulating nutrients and their related transcripts in laying hens.

The levels of glucose, amino acids and most of the long chain polyunsaturated FA (PUFA) fluctuated in a day. And the genes related to transportation, lipogenesis, lipid catabolism, sterol metabolism, as well as oxidative/anti-oxidative system also varied in a day. The transcripts of transporters, cytochrome oxidases (CYPs), hydrolytic enzymes of protein catabolism, heat shock proteins (HSP), key factors in lipogenesis, lipid catabolism and sterol metabolism displayed day-of-time rhythms.

Interestingly, the nadir of the glucose was at 7:00 am, and reached the peak at 11:00 am in a day. The peak levels of amino acids were almost at night, from 11:00 pm to 3:00 am. Except for the C11.0, C14.1, C20.2 and C20.6N3, most of the PUFAs were with two peak concentrations at C7 and C15 respectively.

"The present results would help to design the diet schedule to prevent over deposition of fats and proteins" said WAN Dan, an assistant researcher at ISA, "We will develop a more accurate nutrition schedule for laying hens to improve their production performance".

This research was granted by the National Key Research and Development Program of China.

Their findings entitled "Integrated hepatic transcriptional and serum metabolic studies on circulating nutrient metabolism in diurnal laying hens" were published on National Center for Biotechnology Information.