Pasture-finishing of Bison Improves Animal Metabolic Health and Potential Health-Promoting Compounds in Meat

Abstract

Background With rising concerns regarding effects of red meat on human and environmental health, a growing number of livestock producers are exploring ways to improve animal and human health. A proposed way to achieve this is implementation of agro-ecological practices, including rotational grazing and pasture-finishing of locally-adapted ruminants. Additionally, growing consumer interest in pasture-finished meat (i.e., grass-fed) has raised several questions about its nutritional quality. Thus, the goal of this study was to determine the impact of two common finishing systems in North American bison—pasture-finished or pen-finished in confinement on concentrates for 146 days—on metabolomic, lipidomic, and fatty acid profiles. Striploins (M. longissimus lumborum) were collected for profiling. Results 671 out of 1570 (43%) compounds differed between pasture- and pen-finished conditions (n = 20 animals per group) (all, p < 0.05). Relative to pasture-finished animals, muscle of pen-finished animals displayed markers of excess glucose (~ 1.6-fold), triglycerides (~ 2-fold), oxidative stress (~ 1.5-fold), and proteolysis (~ 1.2-fold). In contrast, pasture-finished animals displayed improved mitochondrial metabolism (~ 1.3-fold higher levels of various Krebs cycle metabolites) and carnitine metabolism (~ 3 higher levels of long-chain acyl carnitines) (all p < 0.05). Pasture-finishing also concentrated higher levels of phenolics (~ 2.3-fold), alpha-tocopherol (~ 5.8 fold), carotene (~ 2.0 fold), and very long-chain fatty acids (saturated and unsaturated; ~1.3-fold) in meat, while having lower levels of common advanced lipoxidation (4-hydroxy-nonenal-glutathione; ~2-fold) and glycation end products (N6-carboxymethyllysine; ~1.7-fold) (all p < 0.05). In contrast, vitamins B5, B6, and C, and gamma-tocopherols were ~ 2.5-fold higher in the grain-fed animals (all p < 0.05); suggesting some concentrate feeding, or grazing plants rich in those compounds, may be beneficial. Conclusions Pasture-finishing (i.e., grass-fed) broadly improves bison metabolic health and potential health-promoting compounds in their meat compared to finishing on confinement on concentrates (i.e., pen-finished). Our data does not, however, indicate that meat from pen-finished bison is therefore unhealthy, as bison meat—irrespective of finishing practice—contained considerable amounts of amino acids, vitamins, phenolics, and a favorable omega 6:3 ratio. Our study represents one of the deepest meat profiling studies to date (> 1500 identified unique compounds), having revealed various previously unrecognized differences in animal metabolic health and meat nutritional composition as a result of finishing mode. Whether observed differences in nutritional profiles between finishing modes have an appreciable effect on human health remains to be determined.