By Owen Rees, TRAC Senior

Ruminant Productivity Consultant

What to expect from this year’s hay and silage…

It has been a trying year for growing fodder. From those that flooded in the north of the country to the south where rain was pretty scarce.  Both extremes have made it hard to grow feed and will also have challenges in preserving high-quality forage.  Many farmers have exhausted their stored homegrown fodder and are looking to replace large chunks of fodder this year.  This may force many farmers and contractors alike to push the boundary of safe forage preserving methods, trying to replenish on-farm storage.

We are recommending that, this season in particular, all forages are tested using A1 Plus.  The A1 plus provides really valuable information on silage acids and pH for silages that tells us how a fermentation has gone for the silage sample, and even indications of spoilage risk (think Butyric acid). The A1+ also shows valuable information regarding time point NDF digestibility for hay and silage. Mould and yeast count should be done if forage has been exposed to rainfall or high moisture during the curing process, this applies to both hay and silage. 

To understand how the weather has influenced silage, first, it is important to cover the basics. Silage is a preserved, high-moisture forage that goes through several phases where acids, temperature and O2 levels change. When the grass or crop is cut, the plant is still respiring and utilizing sugars and energy, the faster the stomata close the more nutritional value is retained.  This is where conditioning and tedding facilitate the process. When the forage is layered into the pit or into a bale, the most crucial component is reducing the amount of oxygen throughout the forage through compaction or bale density.

There are three main phases of the fermentation process.

Phase One:

Phase one is the aerobic phase, which begins immediately after cutting and early on after being ensiled. This is where respiration and proteolysis occur. During respiration, sugars and O2 get converted to carbon dioxide, water and energy for the microbes. This will continue as long as substrate and oxygen are available. When looking at time on the ground it is estimated there will be 5% nutrient loss per day - so it is a high priority to shorten this phase.

In this phase, the sugars are used for aerobic bacteria causing oxygen to drop in a closed stack. The other main factor in this phase is that we will see a rapid increase in temperature. If the temperature goes too high there will be more nutrients used and will result in an increase in NDF, ADF and a drop in energy for lactation – the increase in fibre as a percentage is because we are losing other components. Proteolysis is the second portion of phase one, where we can see protein breakdown resulting in high levels of ammonia (also from excess O2) or high temperature. The longer the silage is exposed to air, the greater protein loss will be observed.

Phase Two:

Phase two will start when all oxygen has been used and we begin fermentation.  Initially Acetic acid, and later lactic acid will begin to be formed and pH will start to decline, however there is only weak acids at this point and high nutrient losses can be observed. This phase should typically only take 1-3 days. An important time to consider whether it is necessary to relocate baled silage, by moving the silage we will be adding oxygen again and the entire process will restart, losing more nutrients.

Toward the end of phase two, lactic acid will begin to be produced. It should come to dominate the acid profile and pH will continue to drop under 5 and towards 4. The higher the sugar content to begin with, the stronger the fermentation that can occur as this is food for the microorganisms to create the preserving acids.

Phase Three:

The silage is now at a stable state with a constant temperature and no more fermentation taking place. Generally, we allow 45 days minimum to reach this phase, however for better results allow 90 days. It is only when oxygen is introduced back to the silage that fermentation can begin again - think of moving baled silage, accidental tears to the plastic and opening the face of the stack to feed out, all problems that can restart the process. However, if the oxygen is not eliminated such as taping the holes, it will never reach phase two and continue to lose nutrients and grow mould.

Our forages this year present several challenges to this preservation process occurring successfully!

• Too Wet: For some early cut silages where there has been less drying time, moisture levels are higher from putting feed into bales or pits a little too wet. Where this has occurred, bales may have slouched, and some effluent may be seen coming from silage stacks. Many of these feeds will look around 17-25% Dry matter (DM). These feeds will have higher acid content and likely lower pH.

With wetter silages, there is also a risk of butyric acid. The high acid content, low pH and the presence of butyric acid can all influence dry matter intake. For these silages it is best to introduce it to animals slowly and dilute with other feeds such as hay. Take a close look at ammonia, sugar content, acid balance and pH and determine if this feed could also pose a clostridial risk. This will also likely be accompanied by a very pungent smell. Cumberland Valley Analytical Services (CVAS) data shows that all silages below 32% DM, will have less than 55% successful fermentation. Above 32% DM the success rate is 74%. These are factors that cannot be changed once it is ensiled, however it can help aid decision making on how and in which animal groups this feed is best used.

• Too Mature: Other silages which reached a very mature plant stage by the time it was able to be cut for silage will have had seed or grain head emergence with varying levels of filling. The plants that have reached maturity will find that NDF typically is higher than 50%, with many results of later cut forages returning results of 55-65% NDF.  The biggest challenge of mature fodder into silage is the ability to get the oxygen out of the plant biomass, and to establish anaerobic ensiling.  Ongoing presence of oxygen will inevitably see spoilage organisms as a greater risk.  The silage starts to compost, not ensile.

Mature silage also has a lower starting sugar level, and with low sugar content we have less capacity to convert sugar to organic acids to allow preservation by acids.

• Silages / hay that were cut and received rain will have lower protein, sugars and energy, depending on when the rain fell after cutting and how long the forage was on the ground. Depending on the time of rain and amount, proteins may drop to 6-7% Crude protein, NDF will remain high around 55-65%, sugars may be under 5% and energy 7.5-9 ME. These results will be very similar for hay that received rain during the drying time.

Whilst these outcomes may seem pretty daunting, there will still be plenty of opportunities to make good quality hay and silage this season. Early planning both on farm and with your contractors will allow you to set up a fodder preserving plan that will kick goals this year.  In every good sporting team there is a point at the end of the season where you need to sit have and evaluate how you went and that is what forage lab tests allow you to do, evaluate how your hay / silage making went.

Forage Lab Australia provides phone support regarding questions around sampling and results, many of these questions so far have been concerns regarding the low quality of their forage.

Please do not hesitate to contact Forage Lab Australia if you have any questions regarding the most suitable test options for your situation.

Take a look at our website www.foragelabaustralia.com.au for more technical information on a wide range of topics, including:

• Understanding Mould & Yeast Count

• In Vitro Fibre Digestibility

• Faecal Starch Analysis

• Understanding Your Lab Report

• Silage Fermentation