Nutritive Value Change during the Fall of Late-Summer-Planted Oats, Radishes, and Turnips

摘要

The change in nutritive value of late-summer-planted oats (Avena sativa L.) and brassicas (Brassica spp.) during the fall in the Midwestern US is not well documented. A mixture of 'Jerry' oats, 'daikon' oilseed radish (Raphanus sativus L), and 'purpletop' turnip (Brassica rapa ssp. rapa L.) was drill-seeded in late August/early September in southcen-tral Nebraska over two years. Forage was collected in early November, early December, and mid-January. The mean in vitro organic matter digestibility (IVOMD) of radish (86%) and turnip (87%) tops were high and were greater than oats (75%). Within forage type, IVOMD did not decline from November to December, but due to a decline in total ethanol soluble carbohydrates in January, IVOMD decreased 10 percentage units for oats and 5 percentage units for brassica tops from December to January. However, these forages would still be considered high energy even in January. In both years, crude protein (CP) of all forages was high, with oats (16% CP) being lessthan both radish (27%) and turnip (24%) tops. Little change in CP occurred over the sampling period. Sulfur content of the brassicas was high in November (0.8-0.9% S) and remained above 0.5% S through January, suggesting that the potential for sulfur toxicity, if grazed alone, persists. Delayed grazing of these cool-season forage mixtures late into the fall and early winter is an option for cattle producers in the Midwestern US, as nutritive value remains appropriate for growing cattle or lactating beefcows.