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 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.) and the alfalfa-ryegrass (Lolium perenne L.) mixtures (0.36) and the lowest ratio in the alfalfa-meadow bromegrass (Bromus biebersteinii Roem. & Schult.) mixture (0.24). Cutting mixtures at the early bud stage of alfalfa generally resulted in a greater forage WSC/CP ratio, except for the first cut in 2015, than cutting at the early flowering stage. In another experiment testing different grass and alfalfa proportions, the WSC/CP ratio was greater when the proportion of timothy (Phleum pratense L.) or tall fescue (Festuca arundinacea Schreb.) in the seed mixture was 80% (0.26) rather than 20% (0.20), 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.