Cutting schedule and species composition to improve energy-to-protein ratios in alfalfa-based mixtures

Energy-to-protein ratios have been suggested as a potential forage attribute related to nitrogen (N) use efficiency in dairy cows but how these ratios vary with the cutting management of alfalfa-based mixtures is poorly known. Our objective was to determine the effect of cutting schedules of alfalfa-based mixtures and their species composition on two forage energy-to-protein ratios from a large number of samples from four field experiments with previously published results on forage dry matter yield and nutritive value. The two energy-to-protein ratios were (1) nonfiber carbohydrates (NFC) to crude protein (CP), NFC/CP, and (2) NFC to the sum of nonprotein N (NPN) and rapidly degradable protein fraction (PB1), NFC/(NPN + PB1). Cutting alfalfa-based mixtures at the early bloom stage rather than at the early bud stage of alfalfa and taking a fall harvest increased mostly the NFC/CP ratio. Including at least one grass species with alfalfa had variable effects on the two ratios. Although several grass species were tested, we cannot conclude on the best grass species to use. Observed increases in the energy-to-protein ratios, however, were relatively small (<8%) and not always consistent in different experiments. Because the relative changes in the energy (NFC) and protein (CP or NPN + PB1) components of the ratios often varied in the same direction when induced by cutting schedules or the presence of grasses with alfalfa, opportunities to improve energy-to-protein ratios with those practices remain limited.