How to analyse your silage this winter

Silage makes up the largest proportion of winter feed fed on beef and sheep farms in Ireland.

It represents a massive cost each year in terms of growing it, ensiling it and feeding it and yet it doesn’t seem to get the attention it deserves on many drystock farms.

A suckler farmer with 60 suckler cows finishing all animals at 24 months will require close to 800t of silage for a six-month winter.

At current prices, this amount of silage could be valued at €20,000.

But how many farmers know the feed value or DMD of this pit of silage?

If you ask farmers what the protein content of their winter ration is, they will most likely know it.

However, when asked the protein content of their silage, few will be able to answer.

Silage with a feed value of 64DMD to 66DMD will help to reduce cow BCS

Winter performance in cattle, especially in young weanlings, can drop below target on many farms due to incorrect supplementation and not meeting an animal’s nutritional requirements.

Silage quality can have a huge effect on this and silage quality will determine the level of concentrates required in all cases.

The nutritional requirements of an autumn-calving suckler cow and a dry cow are very different and it’s important to have a feeding plan to make sure all animals are getting the correct feed. It’s a simple test that can be carried out by most feed companies for clients to determine silage quality. Taking an accurate sample with a silage corer is important to get an accurate analysis.

Dry matter (DM)

This is the amount of silage remaining after all water has been removed. The energy and protein value of silage is quoted in %DM. The higher the DM, the higher the intake of energy and protein will be for every 1kg of freshweight silage the cow eats. In general the lower DM silage will have lower intakes and higher DM silage will have higher intakes.

pH

A well preserved silage should have a pH of between 3.8 and 4.2. Wet silage with a high pH will not keep as well and will usually indicate a silage that has not fermented well and silage intakes will be low. If pH is below 3.8, this can lead to acidic conditions, a sharp smell and cows throwing up “cud balls”. Dry silages can have a higher pH and good preservation.

Ammonia levels

High ammonia levels show poor preservation. This can be due to high grass nitrogen levels at cutting or low sugar, wet young grass being cut. Values of <5% indicate excellent preservation, while >15% will lead to reduced intakes.

Crude protein

This measures the protein concentration of the silage. Young leafy reseeded swards will have higher protein values. Inadequate fertiliser applications can lead to lower protein levels. Values > 15% indicate young leafy swards.

ME (MJ/kgDM)

This is the amount of energy in the silage. Young grass will have the highest energy while mature grass will have lowest energy. The younger and dryer the grass, the more energy the silage will supply for milk production and liveweight gain.

DMD value

This is a measure of the feeding value of the silage expressed as a percentage. Late cut old swards can have a DMD as low as 55DMD while excellent leafy silage can be > 75DMD. Silage with a high DMD will be digested quicker and lead to higher intakes.

Lactic acid %

Bacteria in fresh silage uses grass sugar to make lactic acid which aids the ensiling process by pickling the silage. Cutting young grass in sunny conditions will lead to high lactic acid %. A well preserved stable silage will have a high % of lactic acid. Levels of 8-10% are classified as very good.

Neutral detergent fibre (NDF)

This is a measure of the total fibre content in the silage. Late cut mature stemmy silage will have a high NDF.

Young grass: 45-50%

Average: 55%

Mature grass: 60-65%

Intake value

This is a relative measure of the likely intake of silage. HFIS is the unit measure for beef cattle. This can range from 50-105, and a higher figure indicates high DM, high DMD and low ammonia.

Silage quality so far in 2017

Silage quality is extremely variable this winter. Early reports from silage samples analysed this year show that dry matter digestibility (DMD) levels ranged from 52% to 77%.

The average is running around 70%, which is very good for dry cows. Finishing cattle, weanlings and autumn-calving cows will need some supplementation.

Protein levels range from 8% to 20%.

The average was 12%. Store cattle will struggle to gain anything over 0.3kg/day without meal at this level.

Fibre (NDF) levels range from 41% to 63% with an average of 51%. Table 1 outlines good-quality silage targets.

For a dry spring-calving cow that needs to gain condition, silage quality should be at minimum 68 DMD and offered ad-lib. Silage with 66 to 67 DMD will maintain body condition.

Silage quality below 65 DMD will require supplementary concentrates to be fed for a short period.

Due to lower feed value and reduced silage intake, feeding 1kg/day of concentrate will help to increase cow body condition gradually.

Once the cow reaches ideal BCS, you can remove the concentrates and put cows on to ad-lib silage.

Feeding to reduce body condition score

Reducing body condition should be carried out at a similar rate to gaining condition to prevent metabolic problems. Again, BCS should be altered during the middle months of gestation.

Trying to cut the feed from a cow in the final weeks of pregnancy can lead to milk fever and will also affect the quality of colostrum produced.

Calves can be weaker and slower to get up and suck after birth.

Cows should be reduced from BCS 4.0 to 3.0 over a 10-week period in mid-pregnancy. Silage with a feed value of 64DMD to 66DMD will help to reduce cow BCS.

Where silage quality is higher, offer some straw every other day to reduce silage intake.

Restricting silage intakes by 20% (approximately 10kg to 15kg) will also reduce body condition. Cows should only be restricted if there is sufficient feeding space available.

If not, over-fat cows should be grouped and penned together as the dominant cows will eat to appetite.

Shy feeders will then be under-fed.

Read more

The rules and principles for feeding dry cows

How far will my silage go this winter?

What to do when silage is running low

Meal time: what's on the menu for beef cattle this winter?

What can my silage do for me this winter?