AbstractThe performance of lactating dairy cattle fed on a maize silage (S) dry‐lot scheme was compared with that of lactating dairy cattle switched abruptly from a dry‐lot regime to graze endophyte‐free Johnstone (J), Kentucky 31 (K), or AU Triumph (T) tall fescue (Festuca arundinacea Schreb.) as components of dairy diets. Twenty‐four mature Holsteins either grazed pasture or received maize silage in a dry‐lot as the only forage in the diet during each of two autumn and spring studies. A grain mix was allotted at 1 kg per 2.75 kg of 3.5% fat‐corrected milk (FCM). Herbage present was estimated with a disc meter. More herbage dry matter was provided during both spring periods (P<0.05) from T and K than from J pasture. Cows on S ate more (P<0.05) grain mix supplement and tended to gain more mass (P<0.10) during one autumn and one spring period than cows on pasture, but did not consistently produce more actual milk and 3.5% FCM than cows grazing fescue pastures. There was no consistent advantage in actual milk production for cows on any fescue cultivar throughout the study. Animals grazing T produced less (P<0.05) actual milk than those grazing K during the spring of each year, and less than those grazing J in spring, 1991. Milk fat and protein concentrations did not differ (P≥0.05) for cows on different pasture treatments but the trend was for greater (P<0.10) milk fat content for cows on S. The production of 3.5% FCM did not differ for cows grazing different fescue cultivars, except cows on J produced more milk than those on T during one spring period. Cows in early lactation (autumn periods) lost mass while those in mid‐lactation (spring periods) gained or at least maintained their mass. Grazing fescue pastures can be a viable herbage substitute for maize silage when pastures are of high nutrient content.Journal Paper No. 4–923239 of the Alabama Agricultural Experiment Station, Auburn, United States of America.