Autumn Grazing Management

Autumn Grazing Management – The month of August is a month where the buildup of grass for the months of September, October to Mid-November starts. July was a difficult month with the high temperatures soil moisture deficit, the grass was stressed, and growth was poor. Grass will be entering vegetative growth by the end of August and to ensure that grazing can be continued to November, planning is required. The level of grass to build up will depend on the farm stocking rate and the potential to grow grass. Farmers can control the demand for grass by removing culls and buffering with silage of high digestibility (minimum 76% DMD).

Table 1 below gives targets for covers but for farmers using Pasture Base an autumn budget can be more accurate.

Table 1 Target AFC to meet autumn grazing targets
Date 2.5LU/ha 3.0LU/ha 3.5LU/ha Rotation-Days
Kg DM/ha
Early August 600 600 600 21
Mid August 700 800 850 25
Early September 800 900 1,000 30
Mid-September 1,000-1,100 1,100-1,200 1,200 35

Source: Teagasc

It is important to not apply excess nitrogen, nitrogen application greater than 27 units/acre results in crude protein, in the autumn grazing sward, of 22%-28%. The cow cannot handle this and has to use the equivalent of 1-2 kg of ration in energy to digest the excess protein. This excess protein mobilizes BCS which needs to be minimized as mobilization of body reserves can give rise to sub-clinical ketosis.

Signs of energy deficit can be monitored by checking the milk lactose% per collection, a drop of 0.05% in milk lactose means an action is needed. Nitrogen brings water into the plant which creates a lower dry matter, reducing the potential nutrient density per Kg DM. Monitor cows 2-2.5 hours after entering the paddock following morning milking and if 45%-50% are not lying down and still grazing then the dry matter is low in the grazing sward. These cows will have a reduced ruminating time by at least 1 hour, research reports that this is equal to a drop of 1.86Kg of milk. The concentrate you supplement should contain 35% to 40% cereal as maize and barley grain to aid the utilization of the protein, in the total diet and optimize milk protein percentage.

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