Winter diet composition and quality, and performance of cattle grazing burned and unburned gulf cordgrass rangeland

Abstract

Gulf cordgrass {Spartina spartinae (Trin.) Hitchc.} is a caespitose native warm season perennial grass which grows in low-lying areas of south Texas, especially along the Gulf Coast. Mature gulf cordgrass stands were prescription burned in late fall, 1979, 1980 and 1981. Gulf cordgrass regrowth, cattle diet composition and quality, and livestock performance were monitored in winter following each burn. Grazed forage from four esophageally fistulated steers indicated that steer diets averaged 80 and 71% live leaf tissue on burned and unburned treatments, respectively. Stem tissue averaged 5 and 7% of diets on burned and unburned areas, respectively. Diet samples indicated that during winter period in 2 out of 3 years burning elevated percent live leaf in diets over that of unburned plots. Grasses dominated cattle diets on both treatments, averaging 85% by volume during the study. Because of the lack of sufficient green forage on adjacent unburned uplands, cattle on both burned and unburned uplands consumed substantial gulf cordgrass (49 and 42%, respectively). Consumption of gulf cordgrass decreased in March and April because of the availability of more palatable species on upland areas. Burning increased steer diet quality compared to that on unburned treatments. Crude protein (CP) content of diets was highest in spring when green forage diversity was greatest, regardless of treatment. Burning increased CP contents of diets during January and February of 1980 and 1982 over those from stands not burned. Digestible organic matter was not generally greater in diet samples from burned treatments as opposed to unburned. Average DOM content of diets from burned and unburned was 59 and 56%, respectively, over 3 years, while average CP values were 11.6 and 9.9% on burned and unburned pastures....