Prairies pâturées par des chevaux pur-sang en Normandie : composition minérale des zones surpâturées

Pastures in Normandy grazed by thoroughbred horses : mineral composition of overgrazed areas

Horse breeding is important in Lower Normandy, and farmers are anxious to know about the quality of grazed grass entering the diet of thoroughbred horses. The mineral composition of grass grazed by horses was studied in 11 overgrazed pastures situated on 11 stud farms in the Pays d'Auge. In each of them 4 chemical analyses were carried out : one per category of pasture plants (grasses in the vegetative stage, grasses in the headed stage, legumes, forbs). The use of relative specific co-efficients emphasizes the importance of sward make-up. The pastures are very rich in legumes (mainly white clover), ensuring a large supply of certain micro-elements. The herbage has very large contents in calcium, iron, and manganese, especially in the intensively managed pastures. Phosphorus is low, and the Ca/P ratio is above the recommended norms. White clover plays an important part ; it is recommended to suppress liming and to modify certain management practices so as to keep the clover content at 40-50% of the summer bio-mass. The composition of herbage should be allowed for when determining the strategy of complementary stall feeding (in P, Cu, and Zn) during the grazing period.