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United States Department of Agriculture

Agricultural Research Service

Research Project: Develop and Evaluate Grass and Legume Mixtures for Improved Livestock Performance

Location: Forage and Range Research

2013 Annual Report

1a. Objectives (from AD-416):
The objectives of this cooperative research project are: 1) Evaluate the relative livestock performance when grazing mixtures of pasture grasses and legumes; and 2) Evaluate the productivity of grass and legume mixtures; and 3) Breed pasture grasses and legumes with enhanced compatibility for use in grazing.

1b. Approach (from AD-416):
This research is an expansion and continuation of the research goals and objectives originally started under SCA #58-5428-4-373 entitled "Develop and evaluate plants for improved livestock performance." The new research will determine livestock performance and pasture productivity of grass-legume mixtures in comparison to commercially fertilized grass monocultures. Standard check cultivars and germplasm from ongoing ARS breeding programs will be established in large and small scale research plots. Large scale plots will be used to compare/determine animal performance, carrying capacity, and nutritional content of grass monocultures versus grass and legume mixtures. Results will be based upon livestock weight gain, forage dry matter production, and in-vitro forage quality analyses. Small plots, using multiple species of grasses and legumes in varying composition ratios, will be established to determine optimum grass-legume mixtures and plant densities that maximize pasture productivity in comparison to commercial fertilizer. Livestock grazing on these plots will ensure realistic pressures common to pastures. The role that endophyte infection of grasses has on grass-legume mixture compatibility may be evaluated. Livestock and plant data will be utilized in plant improvement programs to breed for improved compatibility among pasture grasses and legumes.

3. Progress Report:
During FY2013: This agreement was entered into to evaluate plant and animal components of grass-legume mixtures. During this fiscal year several components were evaluated. A 2-yr grazing study was completed evaluating the effects of finishing beef cattle grazed on tall fescue (TF) pastures without or with nitrogen (N) fertilization on growth performance, ruminal fermentation, and carcass characteristics. Some results and subsequent peer-reviewed manuscripts were reported in FY2012. In brief, in response to N fertilization (NF), overall average daily gain (ADG) was greater (P<0.05) and dry matter intake trended upward (P=0.07) in steers that grazed TF+NF pastures (P < 0.05). Overall results of this study indicate that N fertilization on TF affected ruminal fermentation which positively influenced growth performances. During FY2013, an additional manuscript was submitted to Professional Animal Scientist and two poster presentations were made at the 2013 ADSA-ASAS Meeting at Indianapolis. A related study is now evaluating cattle performance when grazing grass-legume mixtures. During FY2013, the first year of this study was completed evaluating beef steers grazing tall fescue (TF) pastures with or without low- and high-tannin legumes and the resulting effects on growth performance, ruminal fermentation, and carcass characteristics. In response to grass-legume mixtures, the preliminary (1-yr) average daily gains (ADG) were 1.7, 1.4, 1.4, and 0.8 pounds per day for TF + birdsfoot trefoil, TF + alfalfa, and TF + fertilizer, respectively, with the TF no fertilizer check being statistically lower than the other treatments. Forage yields followed a similar pattern with the TF + fertilizer yield being the highest (4950 lbs/acre) but not significantly different than mixtures with alfalfa and birdsfoot trefoil, and all three being higher than TF no fertilizer (3591 lbs/acre). Carcass quality and forage yield and quality data are being analyzed. The study will be repeated a second year. This research is being conducted in partial completion of a M.S. thesis and results were presented by the graduate student at the Western Society of Crop Science meetings in Pendleton, OR. A small-plot binary mixture study was completed. Small plots of binary mixtures of five grasses [orchardgrass (OG), tall fescue (TF), meadow brome (MB), timothy, and perennial ryegrass (PR)] and three legumes [alfalfa (AF), birdsfoot trefoil (BF), and cicer milkvetch (CM)] were established and yield data was collected for two years (2011, 2012). Ratios in the mixtures included 0, 25, 50, and 75% legume composition. Results revealed that tall fescue, OG, and MB grass-legume mixes averaged 6.0, 5.0, and 14.0% higher forage production than their respective grass monocultures. The highest seasonal forage production of TF combinations was 1.62 Mg/ha TF:AF (50:50), 1.63 Mg/ha TF:BF (75:25), and 1.64 Mg/ha TF:CM (75:25). Highest forage production of OG combinations was 1.10 Mg/ha OG:AF (50:50), 1.09 Mg/ha OG:BF (75:25), and 0.99 Mg/ha OG:CM (75:25). Highest seasonal forage production of MB combinations was 1.23 Mg/ha MB:AF (50:50), 1.25 Mg/ha MB:BF (75:25), and 1.11 Mg/ha MB:CM (75:25). These results suggest that grass-legume mixtures can be an effective strategy to improve pasture productivity. Mixtures with cicer milkvetch and birdsfoot trefoil were most productive when they constituted 25% of the mix, whereas, mixtures with alfalfa were most productive when it comprised 50% of the mix. This research was conducted in partial completion of a M.S. thesis, and was presented at two professional meetings. In conjunction with a visiting scientist at Utah State University, orchardgrass germplasm freezing tolerance was evaluated. Three genotypes from each of fifty orchardgrass germplasm sources were evaluated with replication at five temperatures. Initial results were inconclusive, but the study will be done again in the fall of 2013. Also, a set of approximately fifteen genes associated with carbohydrate pathways in orchardgrass were identified. These genes were sequenced and we developed primers for PCR. The primers will be used to associate carbohydrate expression with freezing tolerance in orchardgrass germplasm. A protocol modified and evaluated for determining concentrations of water-soluble carbohydrates in perennial grasses. An NIRS equation to predict grass-legume mixtures in mixed pasture planting was generated using different known amounts of grass (tall fescue, orchardgrass, and meadow brome) and legumes (alfalfa, sainfoin, and birdsfoot trefoil) at grass : legume mixtures of 100:0, 75:25, 50:50, 25:75, and 0:100, respectively. The equation was able to predict accurate percentages of grass and legumes early in the growing season. However, later in the growing season, the equation predicted higher percentages of legume and less grass than were present. It appears that the NIRS is using nitrogen levels to differentiate between the grasses and legumes and hence, later in the year the grasses have less N than the legumes. It may require that one equation be generated for early spring forage and one for later summer forage. Utah State University has been an excellent cooperator. They provided land at the USU Pasture Research Facility, livestock research, and support in many areas. Co-authored, peer-reviewed manuscripts have come from this research; as well as, proceedings and abstracts as part of the presentations given.

4. Accomplishments

Last Modified: 07/27/2017
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