Deer damage to alfalfa and mixtures with timothy or orchardgrass

White-tailed deer (Odocoileus virginianus L.) feed heavily on alfalfa (Medicago sativa L.) throughout Pennsylvania. Attempts to reduce deer feeding on forage crops have proven too costly or ineffective. The objective of this research was to determine the loss in yield and economic returns caused by deer feeding on pure and mixed stands of perennial forage crops. At 2 locations in central Pennsylvania, plots of pure alfalfa, timothy, and orchardgrass, and alfalfa-grass mixtures of 25, 50, and 75% alfalfa were established within areas protected (with fencing) or unprotected from deer. Forage was harvested and dry matter yields, percentage of alfalfa and grass, forage quality, and net economic returns were determined. Deer reduced forage dry matter (DM) yield by 1,451 kg ha^-1 yr^-1. Deer feeding also reduced annual yield of pure alfalfa by an average of 54%, while yields of pure orchardgrass were reduced by only 7%, resulting in average economic losses of $198 and $59 ha^-1 for pure alfalfa and pure orchardgrass, respectively. Deer fed more on plots containing timothy than those containing orchardgrass. Forage quality was unaffected by deer feeding but declined as the proportion of alfalfa to grass in the mixture declined. In unprotected areas, mixtures seeded at 50% timothy or 25 to 75% orchardgrass produced greater economic returns than pure alfalfa.