An inquiry was carried out to assess the concentrations of plasma metabolites related to bone remodelling in 21 saddle horses of Warmblood breed aged 4-26 years, five draught horses of Ardennes breed aged 4-10 years, and 10 Ardennes foals aged 9-11 months. They were fed according to normal feeding practice in Belgium. The changes in some bone remodelling plasma metabolite concentrations were studied when an unbalanced diet was offered and later corrected for four Warmblood horses. Bone formation was evaluated by bone alkaline phosphatase (BALP), total alkaline phosphatase (TALP) and osteocalcin (bone gla-protein, OC). Bone resorption was assessed by hydroxyproline (HYP). Total calcium, ionized calcium, phosphorus (P) and 25-hydroxyvitamin D3 [25-(OH)D] concentrations were more or less constant. The comparison of four bone remodelling factors between the Ardennes and Warmblood horses showed higher concentrations in the Ardennes breed. Bone marker concentrations decreased according to age. The correction of the unbalanced Ca : P diet induced inconsistent effects at plasma level. The interpretation of the different bone parameters appeared to be difficult if not associated with other parameters such as a complete anamnesis and clinical examination of the animal in addition to dietary evaluation.

Lucerne and chalk are sources of calcium used to supplement horses diets. The voluntary ingestion of lucerne varies with its form (Cuddeford, 1994). The objectives of this study were to compare the appetency for different sources of calcium, measured by kinetic of ingestion and selection behaviour (sorting, refusal) and to evaluate the effect of those different sources of calcium supplements on the preference of diets offered as a simultaneous choice. The sources of calcium studied were chalk and dehydrated lucerne presented in three forms: 6 mm diameter pellets, 18 mm diameter pellets and ground.

When horses are on diets that are predominant in cereals, the combination of low concentrations of calcium in the diet and the binding of calcium by phytates may result in inadequate calcium intake (Rose, 1990). Chalk and dehydrated lucerne are rich in calcium. It has been shown that the voluntary ingestion of lucerne varies with its form (Cuddeford, 1994). The aim of this study was to evaluate the effect of different sources of calcium (chalk vs dehydrated lucerne) and lucerne forms (6 mm diameter pellets, 18 mm diameter pellets and ground lucerne) on the ingestion and on the metabolic profile in horses offered a cereal-based diet.