Nutritive value change during the fall of late-summer-planted oats, radishes, and turnips

Authors: LENZ, MARY - UNIVERSITY OF NEBRASKA; COX-O'NEILL, JORDAN - UNIVERSITY OF NEBRASKA; HALES PAXTON, KRISTIN; DREWNOSKI, MARY - UNIVERSITY OF NEBRASKA

Submitted to: Crop, Forage & Turfgrass Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/18/2019
Publication Date: 8/29/2019
Citation: Lenz, M.E., Cox-O'Neill, J.L., Hales, K.E., Drewnoski, M.E. 2019. Nutritive value change during the fall of late-summer planted oats, radishes, and turnips. Crop, Forage & Turfgrass Management. 5(1):180097. https://doi.org/10.2134/cftm2018.12.0097.
DOI: https://doi.org/10.2134/cftm2018.12.0097

Interpretive Summary: The change in nutritive value of late summer planted oats and brassicas during the fall in the Midwestern United States is not well documented. Oats, turnips, and radishes were drilled following corn silage harvest in late August or early September in South Central Nebraska, and samples were taken in early November, December, and January over 2 years. Within each month, the turnip and radish tops did not differ in digestibility and were more digestible than oats. Within species, the digestibility in November and December did not differ, but decreased from December to January. However, the digestibility of oats appeared to decline more than turnip and radish tops. The crude protein content of oats was less than radish and turnip top in both years. Although, the forage changed color from green to brown after hard freezes in the month of November, the forage retained much of its nutritive value through January. Thus, delaying grazing of these cool-season annual forages late into the fall is a viable option for cattle producers in the Midwestern United States.

Technical Abstract: The change in nutritive value of late-summer planted oats (Avena sativa L.) and brassicas (Brassica spp.) during the fall in the Midwestern U.S. is not well documented. A mixture of ‘Jerry’ oats, ‘daikon’ oilseed radish (Raphanus sativus L.), and ‘purple top’ turnip (Brassica rapa ssp. rapa L.) was drill-seeded in late August/early September in southcentral 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 less than 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 U.S., as nutritive value remains appropriate for growing cattle or lactating beef cows.