Cattle Responses to Continuous and Seasonal Grazing of California Annual Grassland

Abstract

An 8-year (1961-1968) study at the San Joaquin Experimental Range, in the Sierra Nevada foothills in central California, compared continuous, repeated seasonal, and rotated seasonal grazing on native range, and continuous grazing on sulfur-fertilized range. Cow and calf weight responses showed continuous grazing of annual grassland range to be most productive for cow-calf production. At birth, no advantage of one grazing treatment over another was found among calf weights. At the start of the adequate green forage season, calves under both continuous grazing treatments (native and fertilized) averaged 15 kg heavier than calves under rotated seasonal grazing; calves on continuously grazed fertilized range averaged 12 kg heavier than calves under repeated seasonal grazing. At weaning, calves under continuous grazing treatments averaged 25 kg heavier than calves under seasonal grazing treatments. No advantage of one grazing treatment over another was found among mature cow weights. Overstocking their rangeland was the reason Abram and Lot parted ways (Genesis 13:2-11). The concept of periodically resting the land was set forth by Moses (Exodus 23:10-1 1, Leviticus 25:17). Centuries later specialized grazing management or grazing systems (Range Term Glossary Committee 1974) were set forth to maintain and improve rangeland. Most current grazing systems are designed for managing perennial grasslands. Their purpose is to improve range condition through better livestock distribution, improved plant vigor, greater seed production and seedling establishment, and breaks in habitual use patterns. Such grazing systems may be of little value in managing annual grasslands. Annual plants grow, produce seed, and die in a single year. They need not accumulate food reserves or maintain vigor. Nevertheless, annual plants do respond to factors of seed germination and seedling establishment. And grazing management can affect annual grassland species composition, herbage yield, and livestock production. Can better cow and calf production be obtained on annual grassland under continuous yearling grazing or under some form of grazing system? Cows kept all year in a single range unit at the San Joaquin Experimental Range, Madera County, California, had lower pregnancy and weaning percentages than cows moved to ungrazed units in August (Wagnon et al. 1959). Both groups received supplemental feeding. A third group of cows (moved but unsupplemented) had fewer stillbirths and otherwise did as well as the cows not moved. Interpreting responses of the cows not moved was, however complicated by possible and unusual trace-element deficiencies. Their responses, therefore, were not attributed solely to grazing the same range unit yearlong. The question remained. This paper reports cow and calf weight responses from an 8-year (1961-1968) study intended to answer that question. Herbage Author is range scientists, Pacific Southwest Forest and Range Experiment Station, Forest Service, U.S. Department of Agriculture, 2081 E. Sierra Ave., Fresno, Calif. 93710. Many people were involved in this research. Specific recognition and thanks are due to: Stanley L. Anderson (range technician/herdsman), James L. Burns (maintenance foreman), C. Eugene Conrad (range scientist), Don A. Duncan (range scientist/ project leader), Robert Flournoy (rancher' cooperator, Likely, California), Charles A. Graham (range scientist/ superintendent), C. Dick Hansen (rancher/cooperator, Biola. California), Merton J. Reed (range scientist /project leader), Jack N. Reppert (range scientist). Stanley E. Westfall (range technician), and E. Joseph Woolfolk (division chief/assistant director). Manuscript accepted 10 April 1986. residue amounts and cow reproductive performance are also discussed.