Assessment of forage brassica species for dairy and beef - cattle fall grazing system

Authors: DILLARD, LEANNE - University Of Auburn; Billman, Eric; Soder, Kathy

Submitted to: Applied Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/12/2019
Publication Date: 4/1/2020
Citation: Dillard, L., Billman, E.D., Soder, K.J. 2020. Assessment of forage brassica species for dairy and beef - cattle fall grazing system. Applied Animal Science. 157-166. https://doi.org/10.15232/aas.2019-01921.
DOI: https://doi.org/10.15232/aas.2019-01921

Interpretive Summary: Perennial forages are mainstays in pasture systems for grazing livestock, but lose quality during the fall and early winter months, forcing farmers to feed high-cost harvested forages. Forage brassicas offer a potential solution to this issue as they produce and maintain high-quality forage late into the fall and early winter. We compared yield and quality of three forage brassica species (canola, rapeseed, and turnip) with annual ryegrass, a common annual forage used in fall grazing systems that served as a baseline, in a field-plot study over two fall production seasons. Our results indicated that forage brassica protein and energy yields were twice that of annual ryegrass. Incorporation of forage brassicas into grazing systems provides high-quality biomass for fall grazing when other forages are not productive. Additionally, the increased yield will result in grazing more animals per unit area, and improved animal productivity (milk and weight gain), while reducing the need for harvested forages to decrease feed costs and improve farm profitability.

Technical Abstract: In temperate environments of the United States, winter forage management has traditionally necessitated either: a) feeding conserved forages, or b) stockpiling grazeable perennial forage. Forage brassicas offer a low-cost alternative to these strategies. This project evaluated different annual forage brassicas in a temperate forage production system. Three brassicas, ‘Barisca’ rapeseed [RAP (Brassica napus L.)], ‘Inspiration’ canola [CAN (B. napus L.)], and ‘Appin’ turnip [TUR (B. rapa L.)] were compared against ‘KB Supreme’ annual ryegrass [ARG (Lolium multiflorum Lam.)] for dry matter yield and nutritive value over two fall seasons. Plot sizes were 5.5 × 9.1 m and seeded (brassicas, 5.6 kg ha-1; ARG, 22.4 kg ha-1) in August of 2015 and 2016 in a randomized complete block with four replications. Three harvests occurred in 2015, and four occurred in 2016, at two-wk intervals following initial harvest. Brassica yields (734 – 861 kg ha-1) were greater than ARG (344 kg ha-1), and net energy of lactation, [NEL (1.73 – 1.79 g kg-1)], gain [NEG (1.04 – 1.11 g kg-1)], and maintenance [NEM (1.65 – 1.72 g kg-1)] concentrations in CAN and RAP were all greater than ARG. Additionally, total nutrient yields (kg ha-1) resulted in consistently greater crude protein [CP (176 – 204 kg ha-1)] and NEL (1200 – 1500 Mcal ha-1) than ARG (CP = 88 kg ha-1; NEL = 555 Mcal ha-1). These increased brassica yields allow for twice as many potential grazing days as ARG, thereby extending the grazing season with high-quality forage and decreasing feed costs.