Age-related changes for serum bone metabolism markers in thoroughbred and quarter horse foals

Serum bone metabolism biomarkers in healthy filies and colts from weaning until one year of age

This study aimed to investigate the serum concentration of osteocalcin (OC), parathyroid hormone (PTH), calcitonin (CT), calcium (Ca), phosphorus (P), alkaline phosphatase (ALP) and acid phosphatase (AP) in healthy-weaned-foals from 8 months of age until the first year of life. Moreover, the correlation of investigated parameters and foals' age, as well as the relationship between the serum values of PTH and the other markers of bone remodeling were assessed. From 20 foals (10 fillies, 10 colts), blood samples were monthly collected (from 8 to 12 months of age, T1-T5) and the concentration of OC, CT, Ca, P, ALP, AP and PTH was assessed. Two-way repeated measures analysis of variance (ANOVA) showed age-related differences on OC concentration in both fillies (P = 0.008) and colts (P = 0.03) with higher OC values at T5 than T1 and T2. Sex-related effect on OC concentration was found with higher OC levels in colts compared to fillies (P = 0.01). A significant positive correlation between the OC, PTH, CT and APL values and foal's age was found in fillies and colts. PTH levels were positively correlated with the values of OC in fillies and colts. Obtained findings confirmed the dynamic bone turnover during growth in foals. The modification of PTH and OC confirmed the potential role of these parameters as indicator of bone growth and metabolism. The sex-related difference observed in OC concentration opens up new insights into the possible involvement of sex hormones in the regulation of bone metabolism in prepubertal foals.

Growth patterns, metabolic indicators and osteoarticular status in the Lusitano horse: A longitudinal study

Development of a healthy musculoskeletal system is of high concern for horse breeders and users. A longitudinal field study was performed in order to: (i) evaluate growth patterns and long-term changes on bone quality, bone metabolism, growth factors and metabolic variables in the Lusitano horse; and (ii) retrospectively assess whether these changes were related with radiographic findings regarding osteochondrosis-like lesions (OC) at the onset of training. Thirty-four Lusitano foals born and raised at four stud-farms, were periodically weighed (BW), and measured (withers height-WH) from birth to 36 months of age. On the same days, blood samples were collected for determination of osteocalcin, bone alkaline phosphatase, insulin-like growth factor I (IGF-I), leptin, insulin, glucose, parathyroid hormone (PTH), calcium, phosphorus and magnesium plasma concentrations, and quantitative ultrasound measurements were performed on the right third metacarpal bone (McIII). At the end of the study horses underwent radiographic examination of the four fetlocks, hocks and stifles. According to their radiographic status (OC negative vs. OC positive), Richards growth function was adjusted to BW and WH data. Instantaneous BW and WH growth rates (BW IADG and WH IADG) were calculated for each foal, from the resolution of the first derivative of growth models for seven age-classes. The presence of radiographic findings compatible with OC at the onset of training was associated with changes in BW and WH growth rates. Positive horses presented higher BW IADG from six to 18 months of age and lower WH IADG before 45 days of age (P<0.001). Speed of sound measurements (SOS), bone markers, growth factors and other metabolic variables change markedly with age (P<0.01). OC positive horses tended to have lower SOS values at the lateral region of McIII, lower IGF-I, and higher insulin and PTH concentrations (P<0.1). This study provides indirect evidence that monitoring foals’ growth during the first year of life may be of assistance in managing the occurrence of OC. Further studies with a higher number of animals and a controlled feed intake should be pursued.