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AG News: 20/08/2009

Includes: Testing And Feed Out Times For Silage And Farming Diary

By Department of Primary Industries - 21st August 2009 - Back to News

TESTING AND FEED OUT TIMES FOR SILAGE

When forages have been harvested and fully sealed, they undergo many compositional changes and this is initially due to the action of plant enzymes. Other chemical and organic changes also occur due to a range of undesirable aerobic (air) micro-organisms (bacteria, yeasts and moulds) and desirable anaerobic (without air) bacteria.

Their populations grow at different rates depending on the amount of air (actually oxygen) present, moisture content of the forage, sugar level of the plants, amount of contamination with mud or manure, species, etc.

Ideally, the best process for silage fermentation should be fast. At harvesting, the parent material high in sugar content (usually leafy), is mown, wilted to the correct dry matter content, then foraged or baled quickly (within 1 to 2 days), densely compacted and sealed airtight with high quality plastic.

If any one of the above "ensiling actions" is not carried out carefully, then ‘undesirable’ micro-organisms can develop to lesser or greater degrees.

Air is one enemy of silage and while air is present in the stack or bale, the ‘undesirables’ use the air to live or respire and obtain their energy supply from plant sugars within the forage.

The longer that air is present in the stack or bale, or continues to seep into the storage due to poor sealing, the more energy - or dry matter (DM) - and quality will be lost. The end result is the production of carbon dioxide, water and heat that equates to a loss of DM and nutritive value.

Another enemy is excess moisture. If forage is harvested too wet, then the Clostridia species of ‘undesirables’ will use the plant sugars for growth, break down protein levels, and produce an unpleasant smelling (butyric acid) and unpalatable silage.

The points below explain how stack and baled silages can be tested and when feeding out can begin:

Silage stacks, bunkers and pits

Stacks made under ideal conditions will have their entrapped oxygen supply depleted within a day or so after sealing. These stacks should be well fermented within three to four weeks after sealing, but many stacks undergo much less efficient fermentations and may not be complete until about six to eight weeks after final sealing. Poorly rolled and inadequately sealed stacks may never be completely fermented and if air continues to gain access, it will instead eventually become compost.

Well made stacks can be sampled for analysis around five to six weeks after sealing, but preferably up to eight to 10 weeks later if any one of the previously mentioned ’ensiling actions’ are not correctly carried out. Ideally stacks should not be opened for the same periods.

By this stage, the silage should be relatively stable meaning it won’t go off within one to two days of opening. If opened within a few weeks after sealing, the entry of air into the feeding face and beyond will result in the forage not being completely fermented and the loss of DM and silage quality.

Baled silage

Having a small discrete volume, the trapped oxygen in a bale will become negligible within a few hours due to the activity of the aerobic microbes. This applies to densely packed bales which have been wrapped within an hour of baling with at least four layers of stretchwrap film that covers the entire bale.

However, bales still require three to five weeks to fully ferment due to the longer material and lack of laceration that occurs in bulk chopped forage that in turn releases plant sugars, ie food for ‘desirable’ bacteria. Therefore, analysis sampling should be left for at least three weeks and preferably up to six weeks.

However, however silage can be fed out within a few days of sealing since using it will not affect the remaining bales - although the smell, colour and palatability will be neither fresh grass nor silage as fermentation will have only just started.

For more information, please contact Frank Mickan at DPI Ellinbank on (03) 5624 2222.

FARMING DIARY

Climate change impacts on farming

The Department of Primary Industries (DPI) will be holding a public forum to discuss ‘Climate Change and its Impact on Farming’ on Friday, August 28, 2009 in Woori Yallock.

The forum will provide the opportunity for grazing farmers to learn about the potential impact of climate change in the future. Topics include the Carbon Pollution Reduction Scheme, emissions trading and how it will affect farm businesses.

The forum will be presented by DPI Climate Change policy expert, David Griffin at Parks Victoria, Symes Road, Woori Yallock from 10:30 am to 1:30 pm (refreshments included).

To register for this event or obtain more information, please call Natalie Nelson at DPI Leongatha on (03) 5662 9911.

Source: http://gippsland.com/

Published by: news@gippsland.com