RESUMEN
OBJECTIVES: To determine keratan sulfate (KS) concentration in the serum of foals at the early stage of growing, and to evaluate the role of serum KS as a cartilage catabolic marker, comparing its values with the fluctuation of serum alkaline phosphatase (ALP) activity as a measurement of osteoblastic activity. ANIMALS: 12 foals with normal growth and 3 foals with joint abnormalities within 18 months after birth. PROCEDURE: Measurement of KS concentration and ALP activity in serum and radiographic and physical examinations were done. RESULTS: In all foals, serum KS concentration was high from 1 week after birth to 3 months of age, while serum ALP decreased with aging. The value started to decrease rapidly from 3 to 5 months of age, then gradually reached adult values. During the first 3 months, KS concentration in male foals was significantly higher than that in female foals. In 3 foals which had joint problems, KS concentration was higher than that in normally growing foals at 1 week, and at 1, 2, and 3 months of age. CONCLUSIONS: Cartilage catabolic activity is higher in developing foals up to 3 months of age, suggesting that the immature joint at this time could be easily affected by any factor of loading. Moreover, though only 3 diseased foals were examined, higher serum KS concentration in these foals suggest that this variable might be a useful measure of joint diseases, even at an early stage of life in foals.