ARS | Publication request: Optimizing Pasture Quality and Allowance

Submitted to: Meeting Abstract
Publication Type: Abstract
Publication Acceptance Date: March 9, 2004
Publication Date: March 10, 2004
Citation: Brink, G.E. 2004. Optimizing pasture quality and allowance. Proc. Southwest Wisconsin Profitable Pastures Seminar.

Technical Abstract: Producers understand the importance of pasture yield and quality to dairy cattle. Concerns about pasture characteristics were reflected in a questionnaire taken at the 2003 Wisconsin Grazing Conference, where sward density and dry matter intake were listed as top research priorities in both the 'Pasture Management' and 'Animal Nutrition' categories. These priorities are primary components of grazing research conducted at the U.S. Dairy Forage Research Center. Pasture productivity and composition are influenced primarily by weather and climate (temperature and precipitation), soil characteristics, and management. Due to the effects of climate and soil at a particular site, growth and persistence of certain grass species will be favored. Management can influence the composition of a pasture by the introduction of new species, but grasses growing outside their zone of adaptation may be difficult to maintain. Regardless of the grass species present, however, intake by grazing cattle is strongly influenced by the quantity and quality of available forage. Intake per day increases as the quantity of forage allocated for each animal for a specific time period increases, but decreases as the maturity of that forage increases. As sward height is increased, intake per bite increases more quickly for tall swards such as orchardgrass than for short swards such as Kentucky bluegrass. Bulk density of the sward has a large influence on intake per bite, although the physical effort required to bite and chew forage, texture, carbohydrate or alkaloid content, cell wall digestibility and rate of passage, and the overall dietary balance also influence selection and intake. Questions related to forage selection and intake by the grazing dairy cow have prompted our research into sward structure (the change in forage density and quality from top to bottom) and plant maturity (the ratio of leaf to stem) for a broad range of pasture grasses and grass-legume mixtures. A grazing trial will be conducted to determine relationships among intake, palatability, physical and chemical traits, and rate of passage. Experiments will also address how timing of nitrogen fertilization influences sward structure, tillering, composition, and persistence. Research will be conducted at the U.S. Dairy Forage Research Farm at Prairie du Sac, on University of Wisconsin agricultural research stations at Lancaster, Arlington, and Marshfield, and on selected grazing farms to represent the climate-soil environments where farms are located.