Abstract
A model was developed in an attempt to predict the selection ratio of little bluestem (Schizachyrium scoparium) and brownseed paspalum (Paspalum plicatulum) in a simulated short-duration grazing system stocked at four different levels. The research was carried out over a two year period (1981 and 1982) in a Schizachyrium-Paspalurn grassland of the Post Oak Savannah located at the Texas A&M Native Plant and Animal Conservancy near College Station. Linear and multiple regression analyses were used to determine the variables herbage allowance (total, little bluestem and brownseed paspalum), extended tiller height, live:dead ratio of tillers , temperature, rainfall and stocking rate influencing selection ratio of little bluestem and brownseed paspalum. Total herbage allowance was not restrictive for the potential intake during 1931. The increased grazing pressure for all stocking rates during 1982, coupled with low precipitation during the late growing season, affected herbage allowance only in the two heaviest stocking rates during the fall and early winter. Herbage allowances of little bluestem and brownseed paspalum were the most important variables for prediction selection ratios for both species. Increased herbage allowance of little bluestem favored the preference of brownseed paspalum. This i interrelationship was more noticeable in 1981 when grazing pressure was less than 1982. Mean tiller height and mean live:dead ratios of both species also accounted for variability in selection ratios for these key species. Total herbage allowance was not a significant variable in all models. Temperature and rainfall were the most predictable variables for selection ratio of brownseed paspalum, while stocking rate was most important to the selection of little bluestem. Therefore, selectivity of the dominant species was influenced not only by their botanical composition but by their abundance and morphology, which were affected by stocking rate. Increased stocking rate reduced inter- and intraplant differences. Generally, the ability of the models to predict the selection ratio of brownseed paspalum was dependent upon the availability and phenology of little bluestem. Intraspecific variables were more important in predicting selection ratios of little bluestem than brownseed paspalum.
Araujo, Maria Ribeiro (1985). Dietary selection by cattle as influenced by stocking rates in a short-duration grazing system. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -407788.