The influence of age on bone metabolism in mares during late pregnancy and lactation

•During late pregnancy, the concentration of PTH was higher in older animals.•The concentration of OCN during late pregnancy was higher in younger animals.•The concentration of IGF-I in the younger group was highest during early lactation.•Concentration of IGF-I did not differ between two age groups of mares.•Adaptation of bone metabolism to late pregnancy is impaired in older animals.

The concentrations of carboxyterminal cross-linked telopeptide of type I collagen (CTx), osteocalcin (OCN), parathyroid hormone (PTH) and insulin-like growth factor (IGF-I) were measured in the blood serum of two age groups of mares during late pregnancy (70–50 days before foaling), during early lactation and at the peak of lactation (10–30 and 55–80 days after foaling, respectively). During late pregnancy, the PTH was higher in older (8–19 years old), compared to younger animals (3.5–4 years old) (P < 0.05). The OCN was higher in younger group during late pregnancy (P < 0.05). IGF-I was higher in the younger group during early lactation, in comparison to late pregnancy and the peak of lactation (P < 0.05). IGF-I did not differ between two age groups of mares. The results indicate on the differences in adaptation of bone metabolism to late pregnancy and lactation in older animals, in comparison to younger animals, reflected by elevated PTH secretion.