More Pasture Growth this winter

20% More Pasture Growth This Winter.

10% more milk in the vat this season?

Coming out of a hard summer (yet again) the majority of farmers are once again trying to balance getting pasture covers to 2200kgDM/ha and trying to get cow condition score to 5 by calving time. To do this, farmers try to dry cows off according to condition score and according to pasture covers at the time. They then use a combination of supplements, Nitrogen, undersowing and grazing cows off to help build covers and cow condition.

All of the above will give positive responses to covers and condition score but they do not address the fundamental winter imbalance between pasture growth and animal demand. The traditional use of high stocking rates to ensure good utilisation of spring feed and high milk solids per hectare with out the support of supplements leads to a number of tensions in winter. The traditional "feed rationing" used to limit cow intake in the winter implies a low residual after grazing, a long rotation and a high pasture cover by the next grazing. Principles of sward dynamics elucidated by Stephanie Bluett, Cory Matthew, and others, at Massey University, suggest that the low residual may limit initial regrowth rate by as much as 20%.

High pasture cover is also undesirable. Earlier UK studies by New Zealander John Bircham, working with John Hodgson show that a prolonged period at high pasture cover leads to increased losses from leaf death (senescence). So, going into grass that is too long means that growth rates have reduced due to grass starting to die (senescence), and feed quality has also declined. You get yellowing in the base and the pastures will start to open up due to shading and lower tiller survival.

The new pasture grazing techniques being applied are based on narrowing the gap between pre-and post grazing residuals, with consequent reductions in winter rotation length. Avoiding the inefficiencies of high and low pasture cover in this way provides a higher overall winter pasture growth rate.

This increased pasture growth coupled with the use of supplements to support a higher stocking rate and manipulate grazing height eases the winter feed deficit, yet because of better feed quality, animals increase intake and utilisation remains high in the spring flush. The key change to traditional farming is that the cow can no longer be used as a buffer in the system (ie mining cow condition by under feeding to build or maintain pasture covers). Supplements are needed if a feed deficit does occur.

It is a recipe for disaster if residuals are not protected on a quick round during winter. To protect the residuals will either require you to take cows off the break, feed cows ad lib if lowly stocked or buffer the residuals by using supplements. To get the greatest benefit from grazing pastures correctly, farmers should be doing regular farm walks to monitor changes in pasture covers. Particularly take note of what cows are going into as well as what the cows are leaving. By doing this regularly you can note trends and adjust feeding levels accordingly.

Clients that have followed the guidelines set out above have found that they are growing extra grass over the winter. Those doubting Thomases amongst us should try grazing grass before it reaches 3,000 kgDM/ha and leave higher residuals with one herd, not less than 1200 kgDM/ha and note the recovery time compared with a more traditional hard long rotation, typically leaving residuals of 800-1000 kgDM/ha. You will be pleasantly surprised.

Bruce Thomas B.AgSc C.PAg
Intelact Nutrition Consultant
Waikato/North Auckland