Location: Natural Resource Management Research2008 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.
3. Progress Report
Subobj. 1.1 – Plots have been seeded in the rainout shelter and treatments initiated. Data have been collected for western wheatgrass monocultures and binary western wheatgrass alfalfa mixtures. This work ties to National Program 215, Component 2, Problem Statement F. Subobj. 1.2 – Site selection completed. This work relates to National Program 215, Component 2, Problem Statement F. Subobj. 1.3 – Continuous canopy carbon dioxide exchange sampling was done. This work relates to National Program 215, Component 2, Problem Statement F. Subobj. 1.4 – Sampling sites were identified and the investigation begun on the question of how satellite-based indicators of forage quality and quantity may be used to support stocking rate decisions. A team at the Northern Great Plains Research Lab developed a model in Geographic Information Systems that integrates cattle nutritional requirements with satellite-based data. Preliminary tests indicated cattle stocking rates can be estimated with the model for geo-located pastures selected from Google Earth. A collaborative paper entitled “A satellite data-driven model for estimating grazing capacity in northern prairie” was submitted to Agricultural Systems. This work relates to National Program 215, Component 2, Problem Statement F. Subobj. 2.1 – The first experiment was conducted to evaluate the influence of high-fat supplements on ruminal degradability of dietary protein. This work relates to Problem Statement F of the National Program 215 Action Plan. Subobj. 2.3 – Skills were developed to measure methane output from cattle. 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, which relates to Component 2, Problem Statement F of the National Program 215 Action Plan. 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. This work also relates to Component 2, Problem Statement F of the National Program 215 Action Plan.
1. Greenhouse Gas Emissions from Normal and Altered Cattle Urine in Mixed-Grass Prairie. Use of dietary amendments to reduce nitrogen (N) in excreta, such as condensed quebracho tannin, represent a possible strategy to decrease greenhouse gas (GHG) emissions from livestock. We quantified the effects of tannin-affected cattle urine and normal cattle urine on carbon dioxide, methane, and nitrous oxide flux over a six-week period in a mixed grass prairie. Though the tannin urine treatment possessed 34% less N than normal cattle urine, cumulative nitrous oxide emission between the treatments did not differ. Furthermore, methane uptake from the tannin urine treatment was 40% less than the normal urine treatment. Results from this study suggest the use of condensed quebracho tannin as a dietary amendment for livestock does not yield GHG mitigation benefits in the short-term. Contribution is to the Rangeland, Pasture, and Forages National Program (NP 215, Component 2, Problem Statement F), and Global Change Program National Program (NP 204; Component 2).
2. Condensed tannin did not protect alpha-linolenic acid from biohydrogenation by ruminal microbes. Enrichment of beef and lamb muscle with omega-3 fatty acids is one means to introduce these fatty acids into the human diet, but ruminal biohydrogenation eliminates much of these fatty acids before they can enter the blood stream and be available for uptake into muscle cells. Therefore, treatment of flaxseed, which contains the omega-3 fatty acid alpha-linolenic acid, with the condensed tannin quebracho tannin was evaluated as a means to protect alpha-linolenic acid from degradation by ruminal microbes. Unfortunately, this treatment did not appear to reduce biohydrogenation of alpha-linolenic acid by ruminal microbes because levels of omega-3 fatty acids were not increased in blood plasma when cattle were fed the tannin-treated flaxseed. The research contributes to National Program 215, Component 2, Problem Statement F.
3. Fat supplementation and reproduction in beef cattle. Many beef cows either do not conceive or do not maintain pregnancy after they are artificially inseminated and this is an expensive problem for beef producers that use artificial insemination to improve the genetic composition of their herds. Therefore, the influence of short-term oilseed supplementation at the beginning of estrous synchronization on the fatty acid profile of blood in lactating beef cows grazing summer pasture was determined. Results from the study suggest that providing fat from either whole soybeans or flaxseed will increase the energy density of the diet and provide cattle with fatty acids key to reproduction during breeding and maternal recognition of pregnancy. In addition, there appears to be a lag phase in which dietary fatty acids become elevated in the blood, more so for flax-fed cattle than cattle fed soybeans. Therefore, producers wishing to use an oilseed to increase the energy density of the diet and provide certain key fatty acids in a relatively short period of time should choose soybeans. This research is aligned with National Program 215, Component 2, Problem Statement F.
5. Significant Activities that Support Special Target Populations