Maturation effects on forage quality of Kentucky bluegrass

Abstract

Kentucky bluegrass (Poa pratensis L.) is an important constituent of many permanent pastures in the northern United States and is an important source of livestock feed, but there is a paucity of information on its forage quality. The objective of this research was to assess changes with maturity in forage quality of whole herbage, leaves, and stems of Kentucky bluegrass compared with other important cool-season forage grasses. Kentucky bluegrass, orchardgrass (Dactylis glomerata L.), reed canarygrass (Phalaris arundinaceae L.), smooth bromegrass (Bromus inermis Leyss), timothy (Phleum pratense L.), and tall fescue (Festuca arundinacea Schreb) were sampled weekly beginning in mid-May until each species reached milk stage. Kentucky bluegrass had the highest or was among the grasses with the highest average leaf percentage, and leaf, stem, and whole herbage neutral detergent fiber (NDF) and acid detergent lignin (ADL) concentrations; and lowest average whole herbage, leaf, and stem in vitro digestible dry matter (IVDDM) concentrations compared with tall growing species. Kentucky bluegrass also had the slowest rates of change in leaf and stem concentration and in whole herbage IVDDM and NDF concentrations with maturity. Leaf concentration was negatively correlated with herbage NDF and ADL concentration, but was not correlated with herbage IVDDM and CP concentration. Relative to tall growing cool season grasses, Kentucky bluegrass is leafier, but it has poorer forage digestibility. Key words: Poa pratense L., forage quality, perennial grass, leaves, stems