Serum bone biomarkers osteocalcin and pyridinoline in mares during pregnancy and lactation, and in foals during early post-natal life.

The research analyses how two important bone biomarkers, osteocalcin and pyridinoline, behave in pregnant and lactating mares as well as in foals during their early life. It particularly focuses on understanding the timeline and dynamics of maternal bone mobilisation and replenishment during and after pregnancy, and how bone metabolism develops in foals.

Study Design and Methodology

• The research involved the observation of 18 mares starting from six months into their pregnancy until they gave birth, and then also included the monitoring of both the mares and their foals for four months after birth.
• During this period, the researchers regularly measured the concentrations of osteocalcin (OC) and pyridinoline (PYD) in the blood serum of the subjects. These two markers are indicators of bone metabolism, with OC linked to bone formation and PYD associated with bone resorption or breakdown.

Findings in Pregnant and Lactating Mares

• Interestingly, the research found no change in the mean monthly osteocalcin levels from six to eleven months of gestation. This indicates stability in bone formation during these stages of horse pregnancy.
• However, the concentration of pyridinoline, the biomarker associated with bone resorption, increased noticeably starting at seven months gestation until the time of foaling – suggesting that progressive bone mobilisation occurs in this period.
• In the early lactation period after birth (within 14 days), mean osteocalcin levels were low, reflecting reduced bone formation, but increased significantly by post-foaling month one. These shifts are in line with the increased pyridinoline concentrations in the same period, as well as a drop in these levels afterwards.
• The study theorizes that after the initial mobilisation of bone stores during pregnancy and very early lactation, mares start to replenish their bone stores – which appears to happen between the first and second months after giving birth.

Findings in Foals

• The researchers found that osteocalcin levels in newborn foals initially increased within the first 24 hours after birth and reached a peak by the third month of age. This increase signifies a rapid and significant bone formation occurring in the early life of the foals.
• Pyridinoline levels in foals, however, dropped by their first month of age, suggesting a decrease in bone resorption compared to the period immediately after birth.
• The changes in the ratio of osteocalcin to pyridinoline in the foals indicate that bone growth or accretion dominates in the early postnatal period.

In summary, the observed shifts in the biomarkers osteocalcin and pyridinoline provide valuable insight into how bone metabolism adapts during horse gestation, lactation, and early life of offsprings. This might set the basis for better management protocols addressing the needs of pregnant and lactating mares, as well as neonate horses.