Effect of Stage of Maturity and Method of Preservation of Alfalfa on Production by Lactating Dairy Cows

Two experiments were conducted using three maturities of first-cutting alfalfa harvested at midbud (early), early flower (mid), and full flower (late) as silage in 1984 and as silage and hay in 1985. All diets for both experiments were fed at a 55:45 forage:concentrate ratio (dry basis). In Experiment 1, production was most affected by maturity of alfalfa silage in the high production group in which cows produced 30.3, 28.9, and 26.2 kg of milk per day for the early-, mid-, and late-cut alfalfa diets, respectively. In Experiment 2, alfalfa maturity had no overall effect on production or OM intake. Cows fed the alfalfa silage diets in Experiment 2 consumed an average of 3.0 kg more of OM and produced 1.5 kg more milk than did cows consuming the hay diets. Dry matter digestibility of the total diet decreased with increasing maturity of alfalfa in both experiments, averaging 67.9, 63.8, and 63.1% across all production groups in Experiment 1 and 63.8, 61.4, and 58.7% in Experiment 2 for the early-, mid-, and late-cut diets. Intake of digestible OM was 1.0 kg lower, and rumen retention time of the lanthanum marker applied to the forage was 2.1 h longer for late-cut than for early-cut alfalfa Rumen retention times of lanthanum were shorter and digestible OM intake was greater for cows consuming the silage diets than for cows consuming hay.