No abstract

Fescue (Festuca arundinacea Schreb.) toxicosis during summer grazing is characterized by decreased tolerance to environmental stress. The purpose of this study was to determine if this reduced tolerance causes changes in the behavioral patterns of steers (Bos spp.) grazing fescue pastures during summer conditions as has been shown under other conditions of environmental stress and sickness. During a 3‐year experiment to measure chemical characteristics of four lines of tall fescue and to study physiological responses of steers grazing these fescue varieties, observers monitored the behavior of steers at 1300 h daily and during two 24‐h periods on 9 Sept. and 12 Oct. 1978. Categories with the highest frequency included grazing, lying in the field and shade, and standing in the field and shade. Steers on G1‐307 (an experimental line which contained a low level of perloline) showed symptoms of fescue toxicosis and grazed 20% less, laid in the field 4% less, and laid and stood in shade 8 and 17% more, respectively, than the steers that grazed ‘Kentucky 31’, ‘Kenhy’, and G1‐306 (high level of perloline). All steers spent less time lying in field and more standing in shade on 9 September than 12 October. Results suggest that the grazing behavior of steers varied as a function of variety of tall fescue grazed, particularly during periods of climatic stress.

Tallgrass prairie annual hay production and chemical composition (N, P, K, CA) data from n 23-year study conducted by H.J. Harper, Oklahoma State University, from 1929 through 1951 were correlated with corresponding monthly and seasonal temperature (mean, maximum and minimum, and absolute maximum and minimum), precipitation, wind, spring and fall growing season freeze dates, current and previous year's harvest dates, and previous year's yield. Multiple regression analyses were used to determine the weather variables and multiple regression equations which nccounted for the greatest percentage of variation in PMUri hay production and nutrient concentrations. Equations with 4 independent weather variables for all months prior to the date of hay harvest produced high Rz values for production (82%), and N (SO%), P (81%), K (81%) and CA (91%) concentrations. In general temperature values, especially in the fall of the previous year and Jmuary and midsummer of the current year, recounted for more of the variation in all response variables than did any other kind of weather variable, such as precipitation, wind, or freeze dnte. Equations with 4 independent weather variables for those months prior to June produced only a moderate Rz value (48%) for production, but produced high R2 values for N (76%), P (74%), K (74%) and Ca (7%) concentrations. Relationships deserving additional research are suggested. Temporally and spatially, Oklahoma exhibits a unique variety of weather due to the location of the state on the North American continent. Oklahoma's climate is controlled by various air masses (i.e., warm and humid maritime Tropical from the Gulf of Mexico, continental Tropical from the arid southwest, continental Polar from northern Canada, and continental Arctic from the north polar regions) vying for positions over the state. The weather characteristics of a given area depend upon the frequency and timing of occurrence of these air masses. The frequencies of air mass dominance vary significantly from year to year with the result Oklahomans can usually predict with confidence only that next year's weather will be different from this year's weather. In any given year, the state can experience temperatures and precipitation characteristics of the more humid climate to the east or the more arid characteristics to the west. Ranchers and other rangeland managers are acutely aware weather conditions cause rangeland forage production to vary widely from year to year. The annual variations in growing conditions make it difficult to predict or interpret vegetational responses to grazing and range improvement practices. Oklahoma also offers a significant east-west gradient in elevation, precipitation, and soil types and a north-south temperature gradient influencing the relative abundance of subtropical and temperate-origin flora. This makes it difficult to extrapolate research results from one area to another within the state. Consequently, the accuracy of interpretations of Oklahoma's weather-vegetation relationships and dependa...

No abstract