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University Warns Against Autumn Grazing and Forage

02 November 2012

US - Late hay and grazing this autumn could lead to depleted grass energy reserves and bloat if frost arrives this aututmn, warn Rory Lewandowski and Marc Sulc of Ohio State University.

This year's drought has left most livestock producers with very short forage supplies, so many are cutting hay fields this autumn regardless of the calendar or weather forecast.

Hay harvesting across Ohio the past few weeks has led to questions about management guidelines and the impact of late cutting or grazing on forage grass and legume stands. The biggest management concern is with legume stands.

When significant regrowth occurs after a fall cutting of tall legumes (alfalfa, red clover, birdsfoot trefoil), energy reserves in the roots and crowns will be depleted and there may not be sufficient time for their replenishment before a killing frost. This is often the case with cuttings made the first 10 to 12 days in October. Fall cutting dates that allow only a short regrowth period will leave the plant in a lower energy status going into the winter. Energy reserves are important for winter survival and regrowth early next spring. This is why we recommend the last cutting be taken early enough (early September) to allow at least 6 weeks of fall regrowth so energy reserves can be built up to a high level going into the winter.

An alternative is to delay fall cutting until a time when regrowth will no longer occur, although this is not recommended on heavier soils. The best way to ensure no fall regrowth is to cut after a killing frost.

With our shorter days and cooler temperatures it becomes very difficult to get a cut legume or grass to dry down enough to bale as dry forage. Wrapping wilted forage or harvesting as haylage is the best mechanical option.

Grazing a hayfield is usually a more economical option as compared to mechanical harvest at this time of year. Use of temporary electric fencing can facilitate the grazing of a hayfield. While forages such as alfalfa, clovers and cool-season perennial grasses do not produce toxic compounds after a frost, bloat can be a concern when alfalfa or clovers are grazed after a frost.

The risk of bloat is higher one to two days after a killing frost. The safest management practice is to wait a few days after a killing frost before grazing pure legume stands. At that point the forage will begin to dry down from the frost damage. If animals are not accustomed to grazing high legume content stands or when grazing the stand before a killing frost, it is a good idea to fill them with dry hay before turning into the legume field. Move animals into the legume field in the late morning or early afternoon after they have been grazing another pasture so that they are not entering with an empty rumen.

Maintain access to dry hay or corn stalks while grazing alfalfa, or swath the alfalfa ahead of grazing and let the animals graze the dried forage in the swath. Bloat protectant compounds like poloxalene can be used effectively if fed to animals in a way that ensures consumption of the compound in sufficient and uniform quantities each day by each animal. Finally, when grazing alfalfa stands, restrict grazing when soils are firm to avoid treading damage to the plant crowns.

TheCattleSite News Desk

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