Daily intake and the selection of feeding sites by horses in heterogeneouswet grasslands

In spite of the importance of grazed forage in horse nutrition, little info rmation is available on their daily intake at pasture. We determined the in take of 4 non-breeding mares of a heavy breed (average body weight = 674 kg ), grazing during the summer in heterogeneous natural grasslands of the Mar ais Poitevin (France), an internationally important wetland where grazing i s an essential process which maintains biodiversity. The mares ate large qu antities of forage (21.9 +/- 2.4 kg of organic matter per day, i.e. 166.2 /- 20.8 g of organic matter per kg LW0.75 per day) in comparison with previ ous published values and with the estimated requirements of these horses. T he use of the vegetation was very selective, the mares spent about 70% of t heir feeding time on short grass lawns (sward surface less than or equal to 4 cm, biomass < 100 g.m(-2)), that represented only 10% of the area. This behaviour maintained the plants at young growing stages which are of better quality than ungrazed plants. These results are discussed in relation to t he dynamics of the plant communities.