Drying Rate and Ruminal Nutrient Digestion of Chemically Treated Alfalfa Hay1

Abstract

The effect of chemical drying agents (DA) in combination with surfactant (S) applied to first‐cutting alfalfa (Medicago sativa L.) hay has been variable in reducing drying time. Furthermore, their effect on nutrient availability in rumen has not been ascertained. The objectives of this study were to evaluate the effect of DA concentration and S addition, when applied at mowing, on drying rate, ruminal nutrient availability, and digestion rate of first‐cutting alfalfa hay. Treatments included: UC = untreated control; Lo‐DA/S = DA applied at 30 g L−1 with additional S; Lo‐DA = 30 g L−1, no S; Hi‐DA/S = 60 g L−1, with additional S; and Hi‐DA = 60 g L−1, no S. The trial was conducted in the field, utilizing four replications of each treatment to evaluate drying rate. Two ruminally cannulated cows (Bos indicus) were used to measure the influence of DA on in situ dry matter (DM), nitrogen (N), neutral detergent fiber (NDF), and acid detergent fiber (ADF) digestibility. All treated alfalfa had faster drying rates than UC. Drying agent concentration or S addition had no effect on drying rate. Drying agents did not influence relative proportions of soluble, ruminally digestible or indigestible DM. However, undigestible N, NDF, and ADF increased compared to UC. Rate of ruminal ADF digestion was decreased by DA application. Additional S increased the proportion of indigestible DM, N, and NDF regardless of DA concentration. Digestion rates for N increased for Lo‐DA/S and Hi‐DA compared to Lo‐DA and Hi‐DA/S. Digestion rates for NDF increased and ADF decreased by S addition, Hi‐DA treatments having higher NDF and ADF digestion rates than Lo‐DA treatments. Drying rate of alfalfa hay was increased by chemical treatment at mowing. However, chemical treatment had a variable effect on ruminal nutrient availability.