Grass intake by growing horses at pasture: a test of the effects of the horses' age and sward biomass.

No data are currently available on the quantities of food ingested by young horses at pasture, in spite of the fact that pasture constitutes the main source of nutrients for these animals. In this study, three levels of sward mass were offered to animals (2.3; 2.9 and 3.5 T DM.ha(-1)), which corresp ond to grass heights of 6.6, 8.1 and 9.4 cm. Horses of the Cheval de Selle Francais breed were used (1 and 2 years old, live weight of 334 and 478 kg respectively) in a latin square design. The daily quantities of grass inges ted at pasture were determined, and relationships between daily intake, and the characteristics of the pasture and animal were studied. Intake relativ e to metabolic live weight did not vary between yearlings and 2-year-old ho rses. Intake averaged 82 g OM.kg(-1) LW0.75.d(-1). Compared with yearlings, 2-year-old horses had a lower daily foraging time and a higher intake rate (9.9 vs. 7.6 g OM.min(-1)). Grass height had no effect on the food intake of growing horses for grass between 6 and 9 cm high. Compared with cattle a nd even sheep, horses maintain their levels of food intake even at low swar d heights.