Evaluation of melengestrol acetate prostaglandin (Mga/Pgf), Select Synch, and 7 D Mga/Select Synch estrous synchronization protocols in beef heifers - by R. N. Funston and R. P. Ansotegui, Montana State University, R. J. Lipsey, American Simmental Association; and T. W. Geary, USDA-ARS, Fort Keogh Livestock and Range Research Laboratory, Miles City

• The objective of this study was to evaluate synchronization, conception and pregnancy rates of heifers synchronized with MGA/PGF, Select Synch or Select Synch preceded by MGA (MGA/Select Synch).
• Heifers in the MGA/PGF group received MGA (0.5mg·hd-1·d-1) for 14 days and an injection of PGF (25 mg) 19 days later.
• Select Synch heifers received an injection of GnRH (100 ug) followed by PGF (25 mg) 7 days later.
• The MGA/Select Synch heifers were fed MGA (0.5mg·hd-1·d-1) for 7 days, received GnRH (100 ug) the day following the last MGA feeding and PGF (25 mg) 7 days after GnRH. All heifers received PGF on the same day.
• We observed heifers for estrus continuously during daylight from four days before through five days after PGF and bred by AI approximately 12 hours after onset of estrus. We detremined pregnancy status by ultrasound approximately 50 days after AI.
• More heifers were observed in estrus before PGF injection in both the Select Synch (20%) and MGA/Select Synch (24%) groups than the MGA/PGF (4%) group. Pregnancy rates for heifers in estrus early were higher for both Select Synch (55%) and MGA/Select Synch (63%) compared to MGA/PGF heifers (18%). Synchronization rate (after PGF) was higher for MGA/PGF heifers (86%) compared to Select Synch (66%) and MGA/Select Synch (68%). However, conception rate did not differ for MGA/PGF, Select Synch and MGA/Select Synch, (72, 63, and 62% respectively).
• Overall estrous response was higher for MGA/Select Synch (92%) than Select Synch (85%) but did not differ from the MGA/PGF (89%). The Select Synch (53%) and MGA/Select Synch (57%) protocols provided similar overall pregnancy rates compared to the MGA/PGF protocol (62%). However, considerably more heifers were in estrus before the PGF injection in the protocols using GnRH.
• Estrous synchronization programs must be inexpensive, effective and easy to administer. The MGA/PGF protocol provided the highest pregnancy rates and least variability in estrous response. However, the Select Synch protocol provided acceptable pregnancy rates. Producers who want a shorter synchronization program or when MGA can not be fed or uniformly consumed may consider it. Feeding MGA before the Select Synch program did not provide any benefit in the present study.
• For more information, contact Rick Funston at (406) 232-8223

Effect of age and grain processing method on diet digestibility of beef cattle - by B.M. Rainey, J.A. Paterson, R.J. Lipsey, R.N. Funston, G.W. Brester, and W.T. Choat; Department of Animal and Range Sciences, Department of Agriculture Economics

• We studied the effects of animal age (cows vs. calves) and barley processing method (whole vs. rolled) when fed as a supplement to medium-quality grass hay (10.8% crude protein) on diet digestibility.
• Sixteen, 31-month-old, Angus crossbred cows and 16 newly weaned steer calves were allotted to treatments. We provided light test weight barley (42 lb/bu) at 5.5 lb/cow/day and 2.53 lb/calf/day. Cows received grass hay at 17.5 lb/hd/day and calves at 11.2 lb/hd/day. All animals received .4 pounds of a 37% protein supplement. All animals were adapted to the diet over a 10-day period prior to beginning the experiment.
• Processing the light barley did not influence organic matter, protein or fiber digestibilities. No age x processing interactions were detected for organic matter, protein or fiber digestibilities. Organic matter and protein digestibilities were greater for calves than cows, but fiber digestibilities were similar.
• Processing did not affect starch digestibility when fed to calves, but rolling the barley dramatically improved starch digestibility when fed to cows (71.4% vs. 23.3% for rolled vs. whole). We saw no differences in starch digestibilities between cows and calves consuming rolled barley.
• When whole barley was fed, starch digestibility was reduced by 68.4% in cows compared to calves (23.3 % vs 73.7 %).
• These results suggest processing of barley is necessary more for mature cows than younger calves.
• For more information, contact John Paterson (406) 994-3414

The effects of ranch and backgrounding management on feedyard performance of calves: A survey from Colorado - by D. J. Fennewald, J. A. Paterson, R.J. Lipsey and G. W. Brester, Department of Animal and Range Sciences, Department of Agriculture Economics, Montana State University

• We analyzed 70 pens of feedlot cattle (averaging 202 head per group) from seven states to determine how various ranch management practices affected performance, health and carcass traits in the feedlot.
• Age at weaning averaged 220 days and ranged from 148 to 290 days. After weaning, calves were backgrounded an average of 69 days with a range of zero to 135 days. The weight of the calves entering the feedlot (In WT) averaged 719 pounds and ranged from 456 to 891 pounds. As In WT increased, percent morbidity (sickness) and mortality decreased while ADG and hot carcass weight increased.
• The groups were fed an average of 167 days in the feedlot and had an ADG of 2.95 pounds; steers gained 0.31 pounds more per day than heifers. Calves with heavier In Wt and calves with faster ADG had heavier hot carcass weights, which contributed to more carcasses receiving the USDA Choice grade. Morbidity averaged 11% and ranged from 0 to 39%. Of the calves removed from pens for medical treatment, 36.6% were pulled in the first 30 days and 40.2% were pulled between days 30 and 60. Morbidity increased about 7% when the calves were commingled in the feedlot. The percent that died in the feedlot averaged 1.29% and ranged from 0-5.1%. The morbidity and mortaility rate for Montana calves was comparable to those from surrounding states, but Montana calves were faster gaining, had heavier hot carcass weights and more Choice carcasses. Commingling calves in the feedlot resulted in more morbidity and calves that entered the feedlot at heavier weights had less mortality, higher ADG and HCW, and more Choice carcasses. These data indicate In WT and commingling were critical to health, performance and carcass quality.
• For more information, contact John Paterson (406) 994-3414

Effects of prairie dogs on vegetation - by C. Johnson and B. Sowell, Department of Animal and Range Sciences, Montana State University

• At the turn of the 20th century, the prairie dog was seen as an agricultural pest, and widespread eradication programs began as early as the 1920's throughout the home range of the black-tailed prairie dog. The public's view of the prairie dog has shifted in recent years, as preservation of the grassland ecosystem has gained importance. In 1998, the U.S. Fish and Wildlife Service received a petition requesting immediate consideration of the prairie dog as a threatened species. Supporters of this petition claimed that prairie dogs enhance rangelands by increasing productivity, biodiversity and nutritional content of vegetation on prairie dog colonies.
• In June 2000, we began to evaluate the impact of prairie dog colonies on the mixed-grass prairie of eastern Montana. The objectives were to compare total plant biomass, plant species richness, cover, nutritional differences, and shrub dynamics between prairie dog colonies and adjacent uncolonized sites.
• Total biomass comparisons indicated that standing crop biomass is greater off the prairie dog colonies. Aboveground biomass for cool-season (C3) grasses (dominated by western wheatgrass, needle-and-thread, and Sandberg bluegrass) was nearly three times greater off the prairie dog town than on. Warm season grasses (primarily blue grama) were also greater off the prairie dog town. Nearly seven times the amount of standing dead grass was present off the prairie dog town than on, because prairie dogs constantly clip vegetation to increase visibility and facilitate movement, greatly decreasing the amount of grasses that reach maturity. Dwarf shrub standing crop biomass, dominated by fringed sagewort, was significantly greater on the prairie dog town, which is consistent with any disturbed or overgrazed site.
• In addition, there was no difference in total biomass of forbs between treatments, forbs account for twice the amount of percent total biomass on a prairie dog town (7.4% vs 3.2%) compared to off-colony sites. The shift of C3 :C4 grasses, forbs, and dwarf shrubs suggest that long term occupation (30-50 years) of prairie dogs shift the rangeland toward a lower successional stage. Results of total species richness indicate fewer total plant species on prairie dog colonies. Bare ground was also greater on colonized rangeland compared to uncolonized sites. Crude protein concentration of all vegetative classes was higher on colonized rangeland, with the exception of forbs, which contained similar concentrations of crude protein in both treatments. Total standing crop nitrogen was lower on a prairie dog town compared to off prairie dog towns. Sagebrush biomass, cover and density was greater on uncolonized rangeland compared to on a prairie dog colony.
• The findings indicate that prairie dogs decrease standing crop biomass, plant species richness and total crude protein biomass on their colonies when grazed with cattle. These results are contradictory to those stated in the petition to list the prairie dog as a threatened species.
• For more information, contact Bok Sowell (406) 994-3721

Effects of spring elk grazing on summer cattle forage - by Tracy K. Brewer and Jeffrey C. Mosley, Department of Animal and Range Sciences, Montana State University; Daniel L. Lucas, Montana State University Extension Service, Philipsburg; and Lisa R. Schmidt, Montana Farmer-Stockman, Whitehall

• Foothill rangeland is extremely valuable seasonal habitat for both cattle and Rocky Mountain elk. Elk consume nearly 80% graminoids in spring on foothill rangeland, while cattle consume 75-85% graminoids in summer on foothill rangeland. The existing spatial and dietary overlap of these species on foothill rangelands warrants an elevated level of attention. Increasing elk populations, urban sprawl, conversion of native rangeland to cropland, and increased recreational activity exacerbate the impacts of spatial and dietary overlap among wild and domestic ungulates. Bluebunch wheatgrass is an important forage species on foothill range throughout the Pacific Northwest and the Rocky Mountain West for cattle in summer and for elk in spring. Spring elk grazing of bluebunch wheatgrass could delay cattle turn-out dates onto summer range, increasing annual feeding costs, lowering summer cattle stocking rates, and/or lowering summer livestock performance. Ultimately, excessive levels of grazing may threaten the sustainability of the existing resources.
• The objectives of this study were to compare the effects of early and late spring defoliation at various levels for a single year on plant yield and plant vigor of bluebunch wheatgrass in the summer on foothill rangeland in Montana, and to compare the cumulative effects of early and late spring defoliation at various levels on plant yield and plant vigor of bluebunch wheatgrass in the summer on foothill rangeland in Montana.
• Our results indicate that elk grazing of bluebunch wheatgrass plants in April will not decrease their yield or vigor in June or July. Therefore, cattle grazing management (e.g., turn-out date, stocking rate, etc.) in June or July need not be adjusted to compensate for elk use in April. Elk grazing of bluebunch wheatgrass plants for more than two successive years in May to less than 2-inch stubble heights will decrease plant yield and vigor in June. Therefore, in areas that receive May use by elk that are to be grazed by cattle in June, grazing management needs to be altered in order to sustain the forage resource.
• One option is to encourage elk to use the site earlier in spring or to delay cattle use until later in summer. Another option is to reduce stocking rates of either elk in spring or cattle in summer. Resource managers, wildlife biologists and ranchers should carefully monitor bluebunch wheatgrass vigor in foothill areas that receive elk use in May, especially sites that are subsequently grazed by cattle in June or July, in order to sustain the resource for both species.
• For more information, contact Jeff Mosley (406) 994-3415