Phosphate Status of Bovines Maintained for Long Periods on Bluestem Pasture

Abstract

In the cattle rearing operations in the Flint Hills area of Kansas and also in eastern Oklahoma, much of the native pasture is bluestem grass. The common management practice is to allow animals continuous access to this pasture and to practice during the winter months, supplementary feeding. In many cattle crops, a low percentage of animals fail to thrive as well as the rest when maintained on this pasture, and it frequently postulated that phosphate deficiency is responsible. For the past four years two pairs of 7-year-old identical female twins have been reared on two levels of intake. One animal of each pair received native bluestem pasture only and other animal received a small daily supplement during the winter months. The animals have had an ad libitum intake of spring and well water. Because (a) phosphate is present in limited amounts in bluestem pasture grasses (Table 1) and (b) the adults have been subjected to these levels of nutrition for four years without change, the phosphate status of these unique animals was investigated. Bluestem grasslands are characterized by great stability under grazing conditions and during the period of active growth are highly productive. They are classified as true prairie. The pastures are a combination of such mid-grasses as little bluestem (Andropogon scoparius), sideoats grama (Bouteloua curtipendula), Kentucky bluegrass (Poa pratensis), together with tall grasses, including big bluestem (Andropogon gerardi), indiangrass (Sorghastrum nutans) and switchgrass (Panicum virgatun) (Anderson and Fly, 1955).