2009 Annual Report
1a.Objectives (from AD-416)
Specific objectives of this research include:
Objective 1. Provide management guidelines to improve the conservation and enhancement of agroecosystem function and structure in grasslands of the NGP.
Objective 2. Improve the viability of cattle production on the NGP by providing management strategies that increase the efficiency of forage utilization.
Objective 3. Develop methods to alter the composition of beef so that it better meets the emerging market demand for healthier beef.
1b.Approach (from AD-416)
An automated rainout shelter will be used to simulate drought conditions and test if early-season water stress and (or) defoliation following water stress will have greater impact on productivity of switchgrass or western wheatgrass or on mixtures of western wheatgrass and alfalfa. The influence of soil attributes on growth characteristics of perennial grasses will be determined with greenhouse evaluations using soil collected under native vegetation and under severely weed invaded plant communities at four sites between Mandan, ND and Pierre, SD. Field-based estimates of the greenhouse gases carbon dioxide and nitrous oxide will be used to determine if soil emissions of nitrous oxide offset carbon uptake by moderately grazed mixed-grass prairie. Satellite-based estimates of plant canopy carbon:nitrogen ratio will be determined for five native rangeland pastures and these estimates will be used to determine if they can be used to estimate forage quality for pastures on the northern Great Plains. Experiments with cattle will be conducted to determine if supplemental fat and ruminally undegradable protein will improve feed efficiency of grazing cattle, and if supplemental fat that is fed to forage-finished cattle can increase carcass quality and concentration of unsaturated fatty acids in beef. Trials with cattle will also be conducted to determine if grazing higher quality forages with supplemental flaxseed and (or) forages containing condensed tannin will result in reduced methane emissions per unit of beef produced and greater economic returns. Other trials with cattle will be conducted to determine if omega-3 fatty acid levels in beef can be raised substantially if fattening yearlings are fed flaxseed or flaxseed oil that is treated to protect the alpha-linolenic acid in it from hydrogenation by ruminal microbes. Finally, experiments with fistulated and normal cattle will be conducted to determine if restricting dietary intake of forage and supplemental unsaturated fat will not slow growth but will increase the level of unsaturated fatty acids in beef.
Subobj. 1.1 – Stand and biomass data from the rainout shelter experiment is progressing well. Initial data analysis will be done in the fall and winter.
Subobj. 1.2 – Soil sampling was delayed because of initiation of winter before sampling could be completed in early December. A cool wet spring delayed plans for spring sampling. Sampling will occur as soon as possible in the fall.
Subobj. 1.3 – Continuous canopy carbon dioxide exchange sampling was done.
Subobj. 1.4 – A paper was published in Agricultural Systems from the initial work done for this subobjective.
Subobj. 2.1 – The second experiment was conducted to evaluate the influence of fat and ruminally undegradable protein on site and extent of digestion in cattle consuming a forage-based diet.
Subobj. 2.3 – Measurement of methane output from cattle will begin in last quarter of fiscal year. This allows for testing methods that may reduce methane output from cattle and thus reduce their contribution to their greenhouse gas load and improve their production efficiency.
Subobj. 3.1 – A trial was conducted to test the potential for increasing the omega-3 fatty acid content of beef by feeding flaxseed that was treated to resist rumen microbial hydrogenation of the omega-3 fatty acid in it.
Subobj. 3.2 – A trial was planned for late winter, but the cannulated cattle to be used for the trial were still in use for a field trial that last longer than expected. So, the trial for this subobjective will be done in 2010.
Grazing does not negatively impact soil properties under intermediate wheatgrass. Intermediate wheatgrass is a productive, high quality perennial forage that lacks persistence under grazing. A study was conducted to evaluate the effects of three grazing times on soil bulk density, soil pH, and soil organic carbon under intermediate wheatgrass. Treatment effects on the three soil attributes were negligible, implying grazing time did not negatively impact intermediate wheatgrass beyond a threshold whereby critical soil functions were impaired. Findings from this study are important in the context of sustainable forage and cropping system management, where maintaining or improving critical soil functions are essential for enhancing the long-term viability of agricultural production systems.
Fat supplementation can influence ruminal degradable protein level of soybean meal. Ruminants have two requirements for protein. The first protein requirement is for protein that is degradable in the rumen and second being protein that escapes ruminal degradation and is absorbed in the small intestine. Proper balance of these proteins is critical for the animal because deficiencies in protein degraded in the rumen can reduce the ruminal bacteria’s ability to efficiently ferment forages. In addition, deficiencies of protein that escapes ruminal degradation and is absorbed in the small intestine can hinder animal production. Cattle diets high in fat can reduce dietary intake which will alter the site at which protein is degraded. Furthermore, cattle grazing lush summer pastures are often deficient in protein reaching the small intestine. Therefore an experiment was conducted to evaluate the impact a high fat supplement had on ruminal degradability of protein from a common feedstuff, soybean meal. Results of this experiment showed that as fat intake increased, the ruminal degradability of protein from soybean meal increased above that of published values. Therefore, livestock managers and nutritionists must use published values for ruminal degradability of protein with caution when feeding high-fat supplements to grazing beef cattle. For livestock producers wishing to improve animal weight gain and (or) reproduction, proper diet formulation is important in order to enhance the efficiency with which animals utilize nutrients such as protein.
Organic cobalt supplement on nutrient digestion in growing lambs. Cobalt is an essential macro mineral for use in the production of vitamin B12 and other enzymes involved in energy metabolism. A vast amount of work has been done evaluating livestock and how they respond to diets that are deficient in Cobalt and are supplemented with Cobalt. Supplemental Cobalt has been shown to increase diet digestibility in beef cattle yet little has been done in the growing lamb. Therefore an experiment was conducted in growing lambs fed a Cobalt adequate diet consisting of grass hay and fed mineral containing supranutritional levels of organic Cobalt. Although total tract diet digestibility did not differ, forage intake was increased with additional Cobalt. This improvement in forage intake has positive implications for growing lambs because intake is an important factor in improving weight gain for livestock. This is also a significant finding because most livestock receive mineral supplements throughout the year, and if a producer is able to improve forage intake with a particular mineral ingredient it can improve the profitability of livestock production.
Using satellite data to help managers estimate cattle stocking rates for prairie pastures. The 300 million acres of northern U.S. mixed-grass prairie rangelands are highly variable over space and time and require regular assessment to determine the capacity of rangelands to support cattle. Rangeland managers need reliable, current data delineating forage quality across multiple landscapes and seasons to support management strategies. ARS scientists in Mandan, ND combined cattle nutrition models with remotely sensed plant data to determine the grazing capacity for experimental pastures. Results to date suggest satellite data can be used to assist land managers to estimate stocking rates under changing environmental conditions.
Liebig, M.A., Hendrickson, J.R., Berdhal, J.D., Karn, J.F. 2008. Soil resistance under grazed intermediate wheatgrass. Can. J. Soil Sci. 88:833-836.
Phillips, B.L., Beeri, O., Scholljegerdes, E.J., Bjergaard, D., Hendrickson, J.R. 2009. Integration of Geospatial and Cattle Nutrition Information to Estimate Paddock Grazing Capacity in Northern U.S. Prairie. Agric. Syst. 100:72-79.