Nutrient selection by cattle from grass and grass/legume pastures

Esophageal fistula and hand-clipped samples were collected from a 32-yr-old crested wheatgrass (Agropyron cristatum L.) pasture and an alfalfa (Medica go saliva L.)/meadow bromegrass (Bromus biebersteinii Reem & Schult.)/Russi an wildrye (Psathyuostachys juncea [Fisch.] Nevski) pasture to compare esti mates of nutritional quality. Samples were analyzed for crude protein (CP), in vitro digestible organic matter (IVDOM) and selected minerals. Fistula samples had greater (P < 0.05) CP and IVDOM contents than clipped samples a t all times except that CP did not differ (P > 0.05) on two occasions and I VDOM did not differ (P > 0.05) on one occasion. Differences in mineral cont ent between clipped and esophageal samples were less consistent, but when t hey occurred the mineral contents of esophageal samples usually exceeded (P < 0.05) those of clipped samples. We conclude that clipped pasture samples mostly provide biased estimates of the nutritional quality of herbage cons umed by cattle grazing grass and grass/legume pastures and should be report ed with caution.