Using cutting management and alfalfa-based mixtures as strategies to increase readily-available energy to protein ratio in forages

Cow’s diet with a greater ratio of water soluble carbohydrate (WSC) to crude protein (CP) results in improved N use efficiency and reduced N loss in urine. Little information exists on the effect of management practices on the WSC/CP ratio of forage crops. We assessed the effect of alfalfa (Medicago sativa L.)-based mixtures and cutting management on the forage WSC/CP ratio with measurements from two separate experiments conducted at three sites in Québec (Canada) in 2015 and 2016. Forage WSC/CP ratios were predicted by visible near infrared reflectance spectroscopy. Among six binary alfalfa-grass mixtures and across three sites, the highest WSC/CP ratio was observed in the alfalfa-festulolium (Lolium sp. × Festuca sp.) mixture (0.46) and the lowest ratio in the alfalfa-meadow bromegrass (Bromus biebersteinii Roem. & Schult.) mixture (0.37). During spring growth, the stage of development at cutting significantly affected the WSC/CP ratio of the alfalfa-based mixtures at all sites, with a greater ratio at the flowering (0.52) than at the bud stage (0.40). In another experiment testing different grass and alfalfa proportions, the WSC/CP ratio of the alfalfa-timothy (Phleum pratense L.) mixture was greater when the proportion of timothy in the mixture was 80% (0.32) rather than 20% (0.24), which was expected given that grasses usually contain more WSC and less CP than legumes. Crop management practices could therefore be used to increase the forage WSC/CP ratio.