Animal performance and diet quality as influenced by burning on tallgrass prairie.

Burning on good to excellent condition tallgrass prairie in central Oklahoma yielded results which visually appeared much greater than would be expected from previous burning research. Therefore, a study was designed to quantify the effect of burning on plant and livestock responses. During 1984-1986, average daily gains of stocker cattle were monitored from late May to midOctober in replicated burned and unburned pastures. Stocking rates varied from 0.8 to 1.5 ha per animal depending on initial animal weights. Fistulated cattle were used to monitor diet quality on the pastures. Standing crops were measured at the end of the growing season (early October) in exclosures, and at the end of the grazing period (late October) in the pastures. Animal performance was improved by burning during the early part of the grazing season, and over the season animal production per ha averaged 11.2 kg higher on burned compared to unburned pastures. Dietary crude protein tended to be higher on unburned compared to burned pastures, but the opposite was true for in vitro organic matter digestibility. Standing crop remaining after the grazing period averaged 4,304 and 2,539 kg/ha for burned and unburned pastures, respectively. Standing crop was 57% higher in burned compared to unburned exclosures. Burning caused a shift in species composition to favor tallgrass species and lower production of weedy forbs in both exclosures and grazed pastures. Key Wom: pruadu fonequfy,m The use of prescribed burning for manipulation of range vegetation has gained wider acceptance in recent years. Vegetation changes associated with burning have been documented in a number of ecosystems (Wright and Bailey 1982). Responses tend to be ecosystem-specific and are further influenced by timing of the burn, nature of the fire, environmental conditions (especially precipitation) during the year of burning, management after burning, site, and species composition. Considerably less information exists on the influence of burning on livestock performance. However, research from the Flint Hills of Kansas (Launchbaugh and Owensby 1978), timbered range in the southeastern U.S. (Hilman and Hughes 1965), the Edwards Plateau in Texas (McGinty et al. 1983), and the Texas Coastal Prairie (Angell et al. 1986) all show that burning can improve livestock performance. The majority of research on burning response of tallgrass prairie has been conducted in Kansas. Generally, late spring (about 1 May) burning has yielded the most desirable results compared to other burn dates in terms of forage production and species composition. However, late spring burning has been shown to decrease (Aldous 1934), have no effect on (Launchbaugh and Owensby 1978), or increase (Towne and Owensby 1984; Knapp 1984, 1985) production of tallgrass prairie species. Burning has been studied in Oklahoma; however, the burns were generally not timed to obtain Author is range scientist, USDA/ ARS, 920 Valley Road, Reno, Nevada 89512. At the time of the research, he was research agronomist, USDA/ ARS, Forage and Livestock Research Laboratory, El Reno, Oklahoma 73036. The author thanks Jim Browning, Bobby Handke, Wes Jackson, Jim Trent, and Dr. Michael Zavy for assistance during the study. Drs. Robert Gillen, Wayne Leininger, and an anonymous reviewer provided constructive comments on earlier versions of the manuscript. Manuscript accepted 24 August 1988. maximum forage production (e.g., Adams et al. 1982, Rice and Parenti 1978, Kelting 1957), or burning was intended to improve poor to fair condition tallgrass prairie (Graves and McMurphy 1969). Results from management burns conducted on good to excellent condition tallgrass prairie in central Oklahoma suggested that positive response to fire was greater than might be expected. Burning of tallgrass prairie is used as a management tool in some parts of Oklahoma, especially the northcentral portion of the state, but data detailing the response of livestock to these prescribed burns are not available in the literature. This study was conducted to assess the impact of burning on seasonal trends in diet quality and livestock performance on native tallgrass prairie in central Oklahoma. Study Site The study was conducted from 1984 to 1986 at the USDA/ARS Forage and Livestock Research Laboratory near El Reno, Oklahoma. Vegetation on the study site was typical of good condition tallgrass prairie, with big bluestem (Andropogon gerardii Vitman var. gerardii), Indiangrass (Sorghastrum nutans L.), and little bluestem (Schizachyrium scoparium [Michx.] Nash) as dominants. Soils were silt loams classified as either Udic Paleustolls or Pachic Arguistolls, tended to be well drained, relatively deep (150 cm), and had high available water capacity (Fisher and Swafford 1976). Mean annual precipitation is 762 mm, of which 68% (520 mm) occurs during the April through September growing season. Precipitation was below average during 1984, when yearly and growing season totals were 724 and 349 mm, respectively. Precipitation was above average in 1985 (annual = 969 mm, growing season = 602 mm) and 1986 (annual = 1,108 mm, growing season = 817 mm). Mean annual temperature is 15.60 C. The site has had a history of moderate grazing, but had not been burned for at least 15 years prior to the initiation of the study. Materials and Methods Two adjacent pastures, 37 and 53 ha in size, were used in the study. Each pasture was split, and at random half was assigned to either burning or control treatments. Pastures were treated as blocks, and treatment/block combinations will subsequently be referred to as paddocks. Burning was conducted on 23 April 1984; 10 April 1985; and 7 April 1986. Paddocks were burned when big bluestem had 2 to 4 cm of leaf growth. This criteria was selected because it ensured that ambient conditions would support growth of tallgrass species immediately following burning. At the beginning of the grazing period sward height was about 15 to 22 cm. Each paddock was stocked at 1.5 ha/animal from 13 June to 11 October 1984 and 19 May to 16 October 1985. Heifers with initial average weights of 425 and 460 kg were used in 1984 and 1985, respectively. Steers averaging 190 kg were stocked at 1.2 ha/ animal from 19 May to 1 July, and 0.8 ha/animal from 2 July to 18 September 1986. Average daily gain (ADG) was calculated on the steers initially placed in the paddocks; the additional animals were used to adjust the stocking rate to more nearly match available forage. Animals were penned during late afternoon and weighed JOURNAL OF RANGE MANAGEMENT 42(1), January 1989 11 This content downloaded from 207.46. 13.129 on Sat, 25 Jun 2016 06:56:02 UTC All use subject to http://about.jstor. org/terms