Case Studies: Brassica’s provide great spring feed options

a quick guide to grazing management
Figure 1. Quick guide to grazing management of leafy brassicas, Brassica & Herb Guide, 2018

Tony Hall of “Lara Downs” Peelwood in NSW runs a self-replacing Merino Flock. The farm has 700-750mm rainfall with Sandy Loam Limestone soils. Hunter Leafy Turnip has been used as a high-quality pasture to wean the lambs.  Hunter was selected because of its rapid establishment and early bulk feed. Tony planted 22 hectares of Hunter in September 2018 and 600 lambs were grazed for two months.  They were taken off for a month to six weeks and were returned for a 2nd grazing for almost two months. Tony said “they did really well whilst on the Hunter”. Lamb liveweight gains of 200-250g/day are expected due to the excellent quality leaf Hunter provides.

Tony’s understanding of grazing management assisted in achieving three good grazing’s. “To maximise regrowth, we don’t want to overgraze the growing points on the plant but at the same time we want to take off as much leaf as possible.” If the growing points are grazed off, the plant is much slower to regrow, as it needs to generate new growing points, using stored energy.

For the correct post grazing residuals for Hunter, please refer to Figure 1.

lambs grazing
Lambs grazing Winfred in Bungonia, NSW

Sam Dobbie of “Lumley Park” Bungonia near Goulburn breeds prime lambs on shallow Tablelands soils. Winfred Brassica was dry sown last November. Sam made use of the versatility of Winfred and used it as a quick feed option. He said, “I used it because I had no feed”. Farming at 600 metres+ above sea level means Brassica’s can be established in November. The crop was dry sown into zero soil moisture, but after some early summer storms, 1500 lambs were grazing the 30ha paddock by the 28th of December 2018.

At Bungonia the ideal sowing time for Winfred is late August/early September if you are looking to maximise regrowth. With an early November planting, Winfred still showed excellent regrowth. There were three grazing’s for two weeks at a time until 23 April, even though January and February had extended dry periods. Sam said, “The lambs looked good” as seen by the photo of 2nd Cross Border Leister/Merino Ewes crossed with Dorset Rams left.

Forage brassica plant
Figure 2. Comparison of Winfred (short type) and Greenland (tall type) and Metabolisable Energy, Judson et al, NZ Grasslands 2013

Winfred is a short brassica and has a higher percentage of leaf relative to the total yield than tall types. The leaves of forage rape plants are high quality regardless of the cultivar, however the quality of the rape stem decreases from the top to the bottom. Short types are generally higher quality in the bottom two thirds of the steam, compared to taller varieties. The lowest quality part of the rape plant is the bottom portion of the stem and this makes up a lower proportion of the total yield of Winfred compared to other varieties, this is shown in Figure 2.

If weeds are controlled over the summer, spring sown brassicas provide good seedbed preparation for autumn sowings. Sam drilled Knight Italian Ryegrass into the brassica paddock during the autumn, to give additional winter feed production.

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