Calcium (Ca) is an important factor that affects the reproductive and lactation performance of sows. Circadian clocks and energy metabolism interact, and nutrient utilization is affected by the time of feed intake even the same type of feed and the same amount of calories is consumed.

If the feeding to animals coordinates with endogenous physiological rhythms, it would optimize mammalian production. Ca demands are greater in sows with larger litter sizes and greater milk production capabilities during late pregnancy and lactation.

Researchers from the Institute of Subtropical Agriculture (ISA) of the Chinese Academy of Sciences found that Ca feeding time on sows during late pregnancy and lactation affected productive performance of sows. Their finding confirmed that the absorption and metabolism of Ca in mammals also have circadian rhythms.

A total of 75 pregnant sows were assigned to three groups: The control (C), earlier-later (E-L), and later-earlier (L-E) groups. During late pregnancy, the C group was fed an extra 4.5 g Ca (in the form of CaCO ) at both 06:00 and 15:00, the E-L group was fed an extra 9 g Ca at 06:00, and the L-E group was fed an extra 9 g Ca at 15:00. Similar treatments with double the amount of Ca were applied during lactation.

The results showed that, compared with the C group, L-E feeding decreased the number of stillbirths and the duration of farrowing and placenta expulsion (FARPLA), and increased the average daily weight gain (ADG) of piglets. Similarly, E-L feeding increased the ADG of piglets (p<0.05).

Furthermore, both E-L and L-E feeding increased the Ca levels in sow serum and umbilical serum as well as the Fe levels in umbilical serum, and decreased the Ca levels in the placenta and colostrum (p<0.05).

E-L feeding activated the mRNA expression of TRPV5, S100G, SLC30A7, SLC39A4, and Ferroportin1, while it inhibited the mRNA expression of ATP7A in the placenta (p<0.05). L-E feeding up-regulated the mRNA expression of ATP2B and IREB2, while it down-regulated the mRNA expression of ATP7B in the placenta (p<0.05).

In their previous studies, they also found that crude protein feeding time modulated the lipid profiles in sow milk and plasma; and Ca feeding time in laying hens or sows affected the expression of genes related to the circadian clock and Ca transporters.

The study, published in Animals, was supported by the National Key Research and Development Program of China.