Relationship Between Biomass Accumulation and Forage Quality in a Mixed Cool-Season Grass Sward.

The seasonal pattern of forage growth rate is a fundamental determinant of grazing system productivity. Pasture stocking rates and supplemental feed requirements are influenced by the dynamic balance between forage growth and animal consumption. The animal only reaches high performance when it achieves high forage intake of high quality feeds, which under grazing conditions implies the presence of large amounts of new leaves on offer. On the other hand, forage plants depend on those same leaves to maintain high growth rates and production. The objective of this research was to quantify forage nutritive value of a mixed cool-season grass sward throughout the growing season in Ohio and to describe the relationships of forage nutritive value to forage biomass and plant morphological characteristics. This information will be useful for explaining changes in nutritive value of the forage across the season, and specifically to provide data for modeling the relationship between biomass accumulation and nutritive value. The hypothesis is that there is a strong relationship between amount of biomass present and forage nutritive value, with that relationship being fairly consistent over the growing season. The research was conducted at Columbus, OH, from April to October 2009. The treatments consisted of different dates of initiation of growth (clipping dates) in a mixed cool-season grass species sward. The treatments were replicated 4 times in a randomized complete block design. Total aboveground dry matter biomass yield was measured weekly in each plot using a calibrated rising plate meter. Morphological composition of the sward was quantified and forage quality analyses were conducted. We will present the mathematical relationships developed between forage nutritive value and biomass accumulation.