Energy to Protein Ratio of Grass–Legume Binary Mixtures under Frequent Clipping

Abstract

Forages with a greater energy to protein ratio increase dairy cow N use efficiency. We studied binary mixtures of one legume and one grass species that can increase the ratio of energy availability to protein degradability under frequent clipping. Timothy (Phleum pratense L.), Kentucky bluegrass (Poa pratensis L.), tall fescue [Schedonorus phoenix (Scop.) Holub], orchardgrass (Dactylis glomerata L.), meadow bromegrass (Bromus biebersteinii Roem. & Schult.), and meadow fescue (Festuca elatior auct. Amer.) were seeded with either alfalfa (Medicago sativa L.), white clover (Trifolium repens L.), or birdsfoot trefoil (Lotus corniculatus L.). Carbohydrate and protein fractions (Cornell Net Carbohydrate and Protein System), other nutritive attributes, and dry matter (DM) yield were determined at the first two harvests of the first production year at two sites in eastern Canada. Alfalfa mixtures had a greater ratio of water‐soluble carbohydrates (WSC) to crude protein (CP) and of readily degradable carbohydrate fractions to readily degradable protein fractions than the average of all mixtures; however, they had lower digestibility of neutral detergent fiber and DM, greater fiber concentration, and similar yield. Mixtures with meadow fescue and tall fescue had a greater WSC/CP ratio, yield, and fiber concentration than the average of all mixtures. Mixtures of meadow fescue with any legume species, especially with alfalfa, provided the best combination of a high ratio of WSC/CP (0.70), high yield, and average digestibility. The feasibility of maintaining this desired composition throughout the growing season and for several cropping years remains to be determined.