During a three years survey (1997-1999) in 28 horse breeding farms of Western France (Basse Normandie), the diet of the 286 mares and their foals, and the growth of 439 foals from birth up to 2 years old has been followed. From this pool, X-ray scoring has been realized on 79 yearlings in order to estimate the influence of the diet on Development orthopaedic Disease (DOD). The energy requirement of the mares was correctly covered. The nitrogen and calcium requirements were generously covered while the copper and zinc requirements were hardly satisfied. This situation is a good reflect of the field quality in this part of the country. The breeding farms presenting the least DOD (mean X-ray score between 0 and 1) are those with the highest nitrogen (p<0.01) and calcium (p<0.05) supply of the mares. The energy and nitrogen requirements of 6 to 10 months old foals were met, while their mineral supply was generous with however a large variability. The breeding farms presenting the least DOD include foals who received a moderate energy and nitrogen supply, a generous calcium supply and a Ca/P ratio higher than 2. A copper and/or zinc supplementation, beyond the foals requirements, doesn't constitute a significant preventing factor against DOD.