Conventional production of meat products from ruminant animals in the United States requires inputs including the cultivation and nitrogen fertilization of annual grains such as corn and barley, and transportation of cattle and grain to feedlots. Consumers have concerns about the impact of feedlot conditions on animal health, and about the implications of pharmaceutical inputs such as growth hormones and antibiotics on the environment and human health. These concerns have led to a growing interest in pasturefinished meat production by consumers. Such smaller-scale livestock production systems can be healthier and lower-stress for animals, are integrated into local food systems and are more transparent to consumers, and have higher potential profitability for producers than traditional ruminant production methods. There is a strong market for pasture-finished beef products, and prices for naturally or organically raised beef have remained well above feedlot-produced product prices. There is also concern about the impact of ruminant production on the environment, including air and water pollution from feedlot production and greenhouse gasses that are emitted from ruminant animals during feed digestion. This thesis project explored the potential of a beef production system based on perennial legumes, including the non-bloating legume birdsfoot trefoil (BFT; Lotus corniculatus L.) for producing meat products from cattle while reducing concentrate feeding and methane production. The condensed tannins that are produced by BFT bind proteins in the rumen but allow them to be digested in the abomasum and intestines, which in turn leads to better utilization of forage nutrients during the finishing period and higher gains or milk production. The higher digestibility of legumes compared with grasses reduces methane emissions in cattle both through higher digestibility of the forage and through direct impacts on methanogens operating in the rumen. As reported in this thesis, steers finished on BFT gained significantly more weight per day than steers fed another perennial forage legume, cicer milkvetch, but did not gain as rapidly as feedlot-fed steers. At the end of summer grazing, the blood plasma of pasture-fed steers was lower in saturated and omega-6 fatty acids and higher in transvaccenic and omega-3 fatty acids than the blood plasma of feedlot-fed steers. When beef cows grazed grass and legume pastures, enteric methane emissions were lower on the legume pastures than the grass pasture. These results demonstrate that, compared with other feed sources, perennial legume pastures used for cattle production can improve cattle gains and reduce environmental impacts.

Rising fertilizer prices have led a return to the use of grass-legume mixtures to reduce N costs and improve pasture productivity. The objective of this study was to determine optimal species combinations of binary grass-legume mixtures to improve forage production and pasture nutritive value in irrigated pastures of the Intermountain West. The study was conducted at the Utah State University Intermountain Pature Research Facility near Lewiston, UT. Tall Fescue (TF), Orchardgrass (OG), and meadow brome (MB) were grown with alfalfa (ALF), birdsfoot trefoil (BFTF), and cicer milkvetch (CMV) in legume-grass mixes and monocultures at planting ratios of 25:75, 50:50, 75:25. Grass monocultures were fertilized with 0 (0 N), 67 (67 N), or 134 kg N ha-1 (134 N). Forage was harvested four times each season during 2011-2012. Forage of the mixtures and monocultures from the first and third harvests was analyzed for crude protein (CP) and neutral-detergent fiber (NDF). Average forage production of the unfertilized TF, MB, and OG monocultures was 11.03, 9.76, and 8.10 Mg ha-1, respectively. TF-ALF, OG-ALF, and MB-ALF grass-legume mixes averaged 24.0, 35.0, and 41.0% higher forage production than their respective unfertilized grass monocultures. The grass-legume mixtures with the highest CP were MB-ALF 159, TF-ALF 159, and TF-OG-159 g kg-1 and average 59, 43 and 51% higher than their respective unfertilized grass monocultures. Likewise, the mixtures with the lowest NDF were OG-ALF 453 g kg-1, OG-BFTF 469 g kg-1, and MB-ALF 480 g kg-1. These mixtures had 10, 7, and 18% lower NDF than their respective unfertilized grass monocultures. Individual harvests had similarly higher yields and CP, with lower NDF for the mixtures than the unfertilized grass monocultures. The grass-legume mixture with the 50:50 planting ratio were most productive and had high forage quality. The grass-legume mixtures had similar forage production as the grass monocultures at 134 kg N ha-1. The grass-legume mixtures also had higher CP and lower NDF than the grass monocultures. Cicer milkvetch did not perform well in irrigated pastures. Grass-legume mixtures with ALF and BFTF can be used to replace commercial N while increasing forage nutritive value.