Selecting an Appropriate Cattle Turn-out Date is Critical Any Year

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 Sustaining high levels of pasture production
Pasture production can only be sustained at relatively high levels if grass plants retain adequate leaf area and are given suitable recovery time. Heavy grazing that repeatedly removes a great proportion of the leaf area reduces production. Late summer and fall grazing of short regrowth affects grass tillers ability to overwinter and become next springs early growth. Also, early spring grazing before the plants are ready deprives grass plants of needed leaf area and results in reduced production and economic returns.

Grazing start dates and defoliation
Levels of production and economic returns vary with grazing starting date and season long grazing strategies. The amount of growth decreases when plants are defoliated before the third and a half leaf stage. The earlier defoliation is started, the greater the decrease in production. Starting grazing after the third and a half leaf stage results in minimal damage to plants and can improve annual production of forage.

Early spring growth depends both on carbohydrate reserves and on photosynthetic products produced from the active leaf area of the tiller. Before the third and a half leaf stage, the plant has little leaf area and low carbohydrate levels. Defoliation of the plant at this time results in reduced rates of production. The plant with very small leaf areas left produces little photosynthetic product. It must depend upon stored carbohydrates which are already depleted from overwinter survival.

Make the first spring grazing a short duration one timed to prevent regrazing plant visible regrowth. With this grazing remove only 25-33% of leaf area (leaving 67-75% of the predefoliation leaf area )so there will be no detrimental damage to plants. There is in fact an increase in available carbon from grass plant exudates for the rhizosphere organism biomass to increase their activity level. With this addition of soil carbon and mobilization of mineral nitrogen, plant tillering will be increased, and forage production also increased.

Continuous grazing - In continuous grazing, starting grazing before or after the third and a half leaf stage causes a 45 percent reduction in production which causes reductions of 29 percent in stocking rate, 14 percent in calf average daily gain and 40 percent calf gain per acre compared to starting after the third and a half leaf stage. This reduction in pasture and animal performance causes a decrease in net returns both per cow-calf pair and per acre compared to starting after the third and a half leaf stage.

Twice-over rotational grazing - Twice-over rotational grazing starting after the third and a half leaf stage can have grazing periods designed to coordinate with the biological requirements of growing plants and grazing animals and offers increased stocking rates, calf average daily gain, calf gain per acre, net returns per cow-calf pair and net returns per acre compared to season long grazing starting before and after the third and a half leaf stage.

Protecting grasslands with additional forage
In order to protect grasslands before the plants have reached the 3.5-leaf stage, it is important to feed another type of forage. Specifically planning for this by selecting a paddock with an early growing perennial species mix (eg. crested wheatgrass mix), using winter annuals, or planning to winter feed longer pays dividends on any year. This type of grazing management is absolutely crucial for pastures that have been stressed from previous grazing. The more stressed they are the less carbohydrate reserves they contain. They may green up but do not grow or are very slow to grow in spring. The future yields of these pastures are harmed greatly by grazing before the 3.5 leaf stage.

Paddocks that contain carry-over forage that was grazed after freeze up will be slightly slower to grow in spring. Stockpiled paddocks specifically held over from the previous year for early spring grazing will have their early shoots grazed off before the plants have any chance of recovering from winter dormancy. Both these paddocks need extra recovery time before being grazed again during the growing season.

These points have been taken from “Grazing Before Grass Is Ready” and "Management of Livestock Grazing to Fully Activate the Defoliation Resistance Mechanism in Perennial Grass Plants" by Llewellyn Manske PhD, Dickinson Research Extension Center, North Dakota, USA

Note: The information shared in this article is based on well managed rotational grazing systems. If continuous grazing is used grazing turn out should start later so that more pasture leaf area is present. Greater leaf area is needed to allow for more leaf residual to be left after being grazed. Since continuous grazing will have repeated removal of leaf area over the grazing season, this helps better balance plants photosynthetic production and carbohydrate needs.

By Ken Ziegler and Grant Lastiwka, Forage/Livestock Specialists/ ARD
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For more information about the content of this document, contact Grant Lastiwka.
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This information published to the web on May 20, 2010.
Last Reviewed/Revised on October 17, 2018.