Use of cover crops as fall ungulate forage deterrents and subsequent spring livestock forage

Abstract

In the western United States, high quality forages like alfalfa (Medicao sativa L.) and perennial fall grass pastures containing cereal grains, legumes (Fabaceae spp.), and brassica (Brassica spp.) are commonly utilized by wild ungulates like elk (Cervus) and deer (Cervidae), resulting in negative economic impacts to livestock producers. Cover crops typically include combinations of cereals, legumes, and brassica while providing agronomic benefits to the soil, and alternative forages for either grazing or storage. Some species of brassicas like forage rape and turnips may limit voluntary feed intake in livestock and deer. Objectives of this study were to evaluate wild ungulate activity on fall planted cover crops and, forage quality and yield the subsequent summer. The experiment was conducted near Carmen, ID in the fall of 2016 and summer of 2017. On September 1, 2016, approximately 3 ha under sprinkler irrigation, were divided into three 1 ha plots, which were further divided into three 0.33 ha plots with three cover crops randomly and equally assigned to the smallest plots. Cover crops contained winter triticale (Triticosecale), Austrian winter peas (Pisum sativus subsp. arvense), and hairy vetch (Vicia villosa), and each treatment included canola (Brassica napus), crimson clover (Trifolium incarnatum), or purple top turnip (Brassica rapa). Game cameras were placed at the corners of each small plot to record ungulate activity from October 19 to December 7. In the summer of 2017, three fenced exclosures (0.80 m2) were randomly placed in each of the nine plots to determine cover crop yield and quality. Exclosure harvest was based on growth stage of triticale with initial harvest on June 12, a second on June 28, and a third on July 10. In the fall of 2016, deer and elk had an aversion (P ≤ 0.05) to grazing turnips but not canola and clover. Starting November 18, an increase (P ≤ 0.05) increase in elk detected/grazing turnips compared to canola and clover was observed. As temperatures decreased below 0°C for 5 of 7 days before November 18 we hypothesized that turnip leaves became more palatable and more tender, and elk started to graze them more frequently. In summer 2017, cover crop quantity across harvest periods was similar at 15.9 metric tons DM/ha. Crude protein decreased (P ≤ 0.05; 4.9, 11.4, 7.8%, respectively) and TDN increased (P ≤ 0.05; 54.9, 55.9, 57.3%; respectively) between harvest 1, 2, and 3. Results suggest that cover crops can be manipulated to encourage or deter wild ungulate species as a management tool and still provide adequate quality forage for livestock the following year.