Rotation grazing strategies have been proposed to increase stocking capacity, improve animal gains, and improve forage production and range condition. We compared continuous or season-long, 4-pasture rotationally deferred, and g-paddock time-controlled rotation grazing on mixed-grass rangeland near Cheyenne, Wyo. from 1982 through 1994. Stocking rates under light, moderate and heavy grazing averaged 21.6,47.0, and 62.7 steer-day ha-'; grazing pressures were 11.0 to 90.1 steer-day Mg-' of forage dry matter produced. We estimated above-and belowground biomass, botanical composition and basal cover. Bare ground and cover of warm-season grasses, forbs, and lichens were greater under heavy stocking; cover of litter, western wheatgrass, and total cool-season graminoids were greater under tight stocking. Stocking rate and grazing strategy had no effect on above-ground biomass and little effect on below-ground biomass. Under heavy stocking, percent of above-ground biomass contributed by forbs increased, especially under time-controlled rotation grazing, and that of western wheatgrass decreased. Otherwise+ effects of grazing strategy, level vs. slope, and north vs. south slope on vegetation were insignificant. Steer average daily gain decreased linearly as grazing pressure increased (3 = 0.44); grazing strategies had no significant effect. When cattle prices are favorable, the stocking rates that are most profitable in the short run may be high enough to reduce range condition.

Reduced pasture size and distance to water may be responsible for the alleged benefits of intensive time-controlled rotation grazing systems. We compared cattle gains, activity, distance traveled, and forage utilization on a time-controlled rotation system with eight 2&a pastures, on two 24-ha pastures grazed continuously (season-long), and on a 207-ha pasture grazed continuously, all stocked at the same rate. Utilization on the 207-ha pasture, but not on the 24ha pastures, declined with distance from water. At distances greater than 3 km from water in the 207-ha pasture, utgization was significantly less than on adjacent 24ha pastures, at distances of 1.0 to 1.6 km from water. Cows on the 2071a pasture travelled farther (6.1 km/day) than cows on the 24ha rotation pastures (4.2 km/day), which travelled farther than cows on the 24ha continuously grazed pastures (3.2 km/day). Grazing system, range site, slope, and weather had minimal effects on cow activity patterns. Gains of cows and calves were less on the 207-ha pasture (0.24 and 0.77 kg/day, respectively) than on the 24ha rotation pastures or 24-ha continuously grazed pastures (0.42 and 0.89 kg/da, respectively), with no differences between the latter. Calculated "hoof action" on the rotation pastures was less than that demonstrated to increase seed burial and seedling emergence. Intensive rotation grazing systems are unlikely to benefit animal performance unRss they reduce pasture size and distance to water

Beef cattle distribution patterns on foothill rangeA 3-year experiment designed to quantify the spatial and temporal utilization patterns of range sites by beef cattle on summer foothill range was conducted on the Wick Brothers Management Unit of the Wyoming Game and Fish Commission, 8 km w. of Arlington, Wyo. The grazing seasons, in replicate pastures, were from 15 July-9 August, 15 June-26 July, and 15 June-2 August in 1980,1981, and 1982, respectively. Daily observations were made of radio-telemetry collared cattle (3 per pasture). Cattle dispersion was constrained by the spatial distribution of water and slope. Across 3 seasons, 77% of observed use was within 366 m of water. Approximately 65% of the land area WPS beyond 723 m from water and sustained only 12% of observed use. Cattle concentrated use (79%) on slopes less than 7%. Consequently 35% of the area, on or surrounded by slopes >lO%, received only 7% of observed use. Loamy, grszable woodland and wetlandfsubirrigated range sites were most preferred and accounted for over 65% of observed use while occupying less than 35% of the land area. Overall, course upland, very shallow and shallow loamy sites were not preferred; however, site preference varied as areas further from water were utilized. Observed usewassigniticantly (P

Purified lipopolysaccharide (LPS) infusion in cattle induces clinical and metabolic responses similar to gram-negative bacterial infection. Effects of LPS and dietary protein on rectal temperature, serum hormones, haptoglobin, plasma urea N and AA, and N balance were evaluated in 24 steers (250 +/- 2.8 kg of BW). Treatments were a 2 x 3 factorial of LPS (0 vs. 1.5 microg/kg of BW; -LPS vs. +LPS) and diets containing (DM basis) 1) 14.5% CP, 11.6% ruminally degradable protein (RDP), and 2.9% ruminally undegradable protein (RUP; CP14.5CON); 2) 16.3% CP, 13.4% RDP, and 2.9% RUP (CP16RDP); and 3) 16.1% CP, 11.2% RDP, and 4.9% RUP (CP16RUP). Diet RDP and RUP were altered using casein, fish meal, and corn gluten meal. Steers were adapted to diets (1.1 Mcal/kg of NE(g); DM fed at 1.8% BW) for 14 d and were infused (intravenously 1 mL/min) with LPS (in 100 mL of saline) on d 15. Rectal temperature and serum cortisol, prolactin, haptoglobin, and insulin increased, glucose initially increased and then declined, and serum thyroxine and triiodothyronine decreased for +LPS vs. -LPS steers (LPS x hour; P < 0.01). Serum IGF-I was less (P < 0.01) for +LPS vs. -LPS steers. Plasma urea N increased in response to LPS (LPS x hour; P = 0.02) and was greater for +LPS steers fed CP16RDP and CP16RUP vs. CP14.5CON, but greater in -LPS steers fed CP16RUP vs. CP16RDP and CP14.5CON (LPS x diet; P = 0.04). Plasma Met, Thr, Leu, Ile, Phe, Trp, Gly, Ser, Asn, and Tyr decreased, and plasma Ala increased in response to LPS (LPS x hour; P < 0.01). Plasma Orn initially increased and then decreased in +LPS vs. -LPS steers (LPS x hour; P < 0.01). No LPS x diet interactions (P > or = 0.15) occurred for DM, OM, NDF and N intake, fecal excretion, or apparent digestibility. Dietary DM, OM, NDF, and N intake, and retained N were less (P < 0.01) for +LPS than -LPS steers. Total N intake, apparent N digestibility, and retained N were greater (P < or = 0.05) for steers fed CP16RDP and CP16RUP vs. CP14.5CON. An LPS x diet interaction (P = 0.05) occurred for N retention (% N intake) because N retention was less for +LPS than -LPS steers when fed CP14.5CON, but not different between +LPS and -LPS steers when fed CP16RDP and CP16RUP. These results demonstrate that LPS infusion alters serum hormones, plasma AA, and N balance in cattle and imply that growing steers exposed to LPS may require greater dietary protein concentrations to account for altered intake and metabolic AA demand.

No abstract

The sagebrush-grass rrnge in southcentral Wyoming presently summer and winter grazing seasons of 198 I. supports large numbers of feral homes and domestic livestock. Diets of feral horses and cattle during summer and winter grazing Study Area were evaluated using fecal analydr under 2 stocking levels in small pastures. Horses and cattle consumed primarily grasses during the Study sites were located in the Red Desert, northeast of Rock summer and winter. However, shrubs and forbs were also impor-Springs, Wyo., in Sweetwater County(Fig. I). A semiarid climatic tant dietary components. Needleandthread, Sandberg bluegrass, thickspike wheatgrass, Indian ricegrass, gray horsebrush, and winterfat were the maJor foods of horses and cattle during the summer anti wfnter. Dietary overlap between horses and cattle during the summer averaged 72% and Increased to 84% during the winter. Horses and cattle selected foods in a simllrr order. Large increases in feral horse (Equus cubaflus) numbers have occurred in the western United States since passage of the Wild Free-Roaming Horse and Burro Act of 1971 (Artz 1977, Wolfe 1980). These increases have become a major concern to public land managers, livestock producers, and animal welfare groups. Cook (1975) reported a 20-30% annual increase in feral horse populations in the western United States yearly from 1973 through 1975. This increase in population has forced public land administration agencies to reduce domestic livestock grazing in localized areas to accommodate the grazing pressure feral horses have added on Fig. 1. Locations ofsummer and winrer sites in the Wyoming Red Lksert. western ranges (Artz 1977). In 1974 the feral horse population in pattern prevails over both areas. Yearly precipitation averages 21.5 Wyoming was estimated at 4,434 animals; however a recently cm with approximately 40% falling from April to June. Snowfall completed census estimates the population at 10,448 animals usually occurs from October to May (BLM 1978 a,b). (USDI-BLM and USDA-FS 1980). Three distinct vegetation types cover most of the summer study An important factor in determining proper animal stocking area. The sagebrush-grass type on sandy and loamy range sites is levels for a given range is the botanical composition of diets of characterized by a shrub layer of big sagebrush (Artemisia tridenmajor herbivores and the relationship of diets to available forages. tata subsp. tridentata, vaseyanu, Wyomingensis), Douglas rabbit-Animal Science, University of Wyoming, assistant professor, Division of Range greasewood (Sarcobatus vermiculatus), rubber rabbitbrush (Chrymanagement, an! associate profeso~, Division of Animal Science, University of sothamnus nauseosus), fourwing saltbush (Atriplex canescens), Wypming, Laranue 8207 I. Mr. Krysl IS currently a graduate assistant! Department of ;;&?I and Range Scwnces. Box 3-1. New Mexxo State Universl(y, Las Cruces spiny hopsage (Grayia spinosa), Sandberg bluegrass, Indian ricegrass, needleandthread, lambsquarter (Chenopodium alba), west-This study was ...

Metabolic demand for sulfur-containing AA increases during inflammation in nonruminants. Therefore, Met supplementation may alleviate the negative effects of infection on N balance. Effects of gram-negative bacterial lipopolysaccharide (LPS) and supplemental dietary Met on N balance, serum hormones and haptoglobin, and plasma urea-N and AA were evaluated in 20 Angus-cross steers (BW = 262 +/- 6.3 kg). Treatments (2 x 2 factorial) were infusion of no LPS (-LPS) or a prolonged low dose of LPS (+LPS) and dietary supplementation of no (-MET) or 14 g/d (+MET) of rumen-protected Met (providing 7.9 g/d of dl-Met). Steers were adapted to a roughage-based diet (DMI = 1.4% of BW daily) and supplemental Met for 14 d, and were then infused (1 mL/min via intravenous catheter) with LPS on d 1 (2 microg/kg of BW) and 3 (1 microg/kg of BW) of a 5-d collection period. Blood was collected on d 1, before LPS infusion, and at 2, 4, 6, 8, 10, 12, and 24 h after LPS challenge. Diet samples, feed refusals, feces, and urine were collected daily for 5 d. Rectal temperature and serum concentrations of cortisol, prolactin, tumor necrosis factor-alpha, and haptoglobin increased, whereas thyroxine and triiodothyronine decreased for +LPS vs. -LPS steers (LPS x h; P < 0.01). Plasma urea-N was greater for +LPS than -LPS steers (LPS; P = 0.03), and serum IGF-1 was not affected (P > or = 0.26) by LPS or Met. Plasma concentrations of Thr, Lys, Leu, Ile, Phe, Trp, Asn, Glu, and Orn decreased, plasma Ala increased, and Gly and Ser initially increased, then declined in +LPS vs. -LPS steers (LPS x h; P < or = 0.04). Plasma Met was greater for +MET than -MET steers before LPS infusion, but declined in +MET steers after LPS infusion (LPS x Met x h; P < 0.01). By design, DMI was not different, but DM digested was less (P = 0.04) for +LPS than -LPS steers. Infusion of LPS did not affect (P > or = 0.24) N intake, fecal N excretion, or N digested, but resulted in greater (P < 0.01) urinary N excretion and less (P < 0.01) N retention. The absence of an LPS x Met interaction (P = 0.26) for N retention indicates that supplemental Met does not improve the N utilization of growing beef steers exposed to a gram-negative bacterial endotoxin. Decreases in plasma concentrations of several essential AA in +LPS steers suggest that metabolic demand for these AA likely increased in steers exposed to endotoxin.

Cattle gains and conception rates in 1974-1977 on crested wbeatgrass pasture in spring and fall and native range in summer (CW-NR system) were compared with performance on native range throughout the grazing season (NR system). The CW-NR and NR systems were stocked at 0.20 and 0.10 AU/ha, respectively. Conception rates on CW-NR and NR were 84% and 86%, respectively, excluding results from 1975 when there were problems with heat detection; this difference was not significant. Cow, heifer, and calf gains (average of 0.30, 0.41, and 0.82 kg/day, respectively) and calf weaning weights (average of 196 kg) did not differ significantly between systems. Because of the higher carrying capacity of CW-NR, calf production averaged 24.8 kg/ha vs. 13.0 kg/ha on NR. Other advantages of the CW-NR system included reduced labor for heat checking and for gathering cows for breeding.