Browsing Journal of Range Management, Volume 48, Number 3 (May 1995) by Subjects
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Forage intake by beef steers grazing winter wheat with varied herbage allowancesTwo grazing trials were conducted in separate years on a 5.86 ha winter wheat (Triticum aestivum var. Chisholm) pasture divided into 10 experimental paddocks. Paddocks were differentially grazed with beef steers to produce an array of different herbage mass levels, expressed as kg dry matter (DM)/ha. Each experimental paddock was then continuously stocked with 3 beef steers during each 7-day forage intake trial. Daily forage intake, expressed as kg organic matter (OM)/100 kg body weight (BW), was estimated from fecal output (Cr2O3 dilution) of the beef steers and in vitro organic matter disappearance of esophageal masticate collected from each paddock. Estimated daily gain was calculated from forage intake and net energy values calculated from organic matter disappearance data. Forage intake, organic matter disappearance, and estimated daily gain were related to daily herbage allowance, expressed as kg DM 100 kg BW-1 day-1, and herbage mass utilizing a quadratic equation with a plateau function. As herbage allowance increased, organic matter disappearance improved (Y = 62.18 + 1.08 herbage allowance -.022 herbage allowance2; r2 = .64, MSE = 5.06) as did forage intake (Y = 1.3 + .12 herbage allowance -.003 herbage allowance2; r2 = .52, MSE = .07), and estimated daily gain (Y = -.059 + .12 herbage allowance -.003 herbage allowance2; r2 = 59, MSE = .07). Plateaus were achieved at herbage allowance between 20 to 24 kg DM 100 kg BW-1 day-1. Results of this study indicate forage intake and estimated daily gain declined severely as herbage allowance fell below 20 to 24 kg DM 100 kg BW-1 day-1. This data may provide a threshold herbage allowance for initiation of energy supplementation programs for growing cattle on wheat pasture.
Growth of winterfat following defoliation in Northern Mixed Prairie of SaskatchewanAn observed increase in winterfat (Ceratoides lanata (Pursh) J.T. Howell) on ungrazed rangeland suggests that this shrub may potentially be an important forage resource in the Northern Mixed Prairie under improved grazing management. The objectives of this study were to: 1) compare density, frequency, and cover of winterfat in a grazed pasture and site that had been protected from grazing for about 30 years; and 2) evaluate regrowth of winterfat following defoliation during the growing season on a clayey range site in Saskatchewan. Density, frequency, canopy cover, and basal cover were significantly greater in the protected range than the grazed pasture. Density (1.1 SE +/- 0.01 plants m-2) and frequency (70% SE +/- 3.6) were about 2-fold greater, while canopy cover (7.0% SE +/- 1.4) and basal cover (1.7% SE +/- 1.5) were 7- to 8-fold greater, in the protected versus grazed range. When defoliated to a 5-cm stubble in May, June, or July plants produced significant amounts of regrowth but not when herbage was removed in August. When defoliated in late July or August current year production the following year was significantly lower than control and earlier defoliations. Current year production peaked in late July and August. Total standing crop was 2- to 4-fold greater in the control than the defoliation treatments because the biomass produced in previous years was removed from clipped plants. Because winterfat produces substantial amounts of new growth following defoliation in May, June, or July it is recommended that this shrub be grazed only once during the growing season to prevent grazing of this regrowth. Plants defoliated in May can potentially produce biomass equal to control the following year whereas plants defoliated in June, July, or August will likely require more than 1 year of rest to recover their annual productivity.
Livestock grazing impacts on interrill erosion in PakistanThis study was conducted for 2 consecutive growing seasons in a temperate region of Pakistan to determine a residual phytomass level necessary to adequately protect the soil against accelerated interill erosion A rainfall simulator was used to apply rainfall to 48 (1 m square) circular plots arranged in a completely randomized experimental design, with 4 residual phytomass levels and 2 replications. The residual treatment with 3,024 kg ha-l phytomass resulted in the lowest erosion rates, and the treatment with 624 kg ha-l phytomass produced the highest erosion. Standing phytomass was the most important variable affecting erosion with foliar cover and basal cover also highly correlated to erosion.