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Evaluation of Cover Crops as an Alternative Forage Source for Beef Cattle




Carrell, Russell

Type of Degree

PhD Dissertation


Animal Sciences


Grazing of cool-season cover crops has been shown to be a viable tool for extending the grazing season while mitigating environmental risks associated with row-crop farming systems. Grazing cover crops is not novel, but most recent information available on this practice focuses on soil health as opposed to forage production and animal performance. A 3-yr study was conducted in Headland, AL to evaluate the effects of cattle removal date on steer performance, forage biomass, and forage nutritive value in a grazed cover crop system. Twelve 0.62-ha pastures were established in a forage mix consisting of ‘Cosaque’ oats (Avena strigose), ‘FL401’ cereal rye (Secale cereal), ‘AU Sunrise’ crimson clover (Trifolium incarnatum), and ‘T-raptor’ brassica (Brassica napus × B. rapa) and randomly allocated to be grazed through either mid-February (FEB), mid-March (MAR), or mid-April (APR) with an ungrazed control (CON). Three tester steers were randomly assigned in each paddock based on BW with the exception of CON. Put-and-take steers were added as needed to maintain a forage allowance of 1 kg DM/1 kg BW. Differences in forage biomass were detected between CON and FEB (P < 0.001), CON and MAR (P < 0.001), and CON and APR (P < 0.001). A difference in forage crude protein (CP) concentration was detected between MAR and CON (P < 0.02). No differences in animal performance were detected, and multiple regression analysis indicated that forage NDF concentration had the greatest influence on ADG of forage quality and stocking parameters. Results indicate that grazing of cool-season annual cover crops can reduce winter supplementation needs for cattle but may not be as advantageous when managed under continuous grazing for stocker cattle production. An additional study conducted at the Auburn University Ruminant Nutrition Laboratory evaluated the digestibility, Volatile Fatty Acid (VFA) production, and methane (CH4) production of cool-season cover crops harvested at the beginning of either January (JA), February (FE), March (MA), or April (AP). The objective of this study was to determine if forage digestibility and subsequent products of digestion differed as forage physiology changes within a growing season. Samples were digested in vitro for either 2, 4, 8, 24, or 48 h. Cover crops harvested in JA had greater in vitro dry matter digestibility (IVDMD) than FE (P = 0.009), MAR (P = 0.008), and AP (P = 0.01) following 48-h digestion. No difference in total VFA production were present, but JA harvested forages produced less CH4 than FE (P = 0.01), MA (P = 0.003), and AP (P = 0.01). Data from both studies indicate that cool-season annual cover crops can be a suitable grazing crop for beef cattle. Optimum grazing management strategies are not fully known, however.