Testing silage quality: The importance of it and how you can go about doing it

The wet weather of late has meant many farmers have started housing their cattle, while others won’t be far behind.

With pits of silage and bales being opened right across the country, it’s important that farmers know what quality of feed they are feeding their cattle/sheep.

AgriLand spoke to Peter Lawrence, a drystock advisor for Teagasc in Co. Wicklow, about why testing your silage is important and how it can be done.

Peter went into detail about how crucial it is to know what quality of silage you are feeding your cattle/sheep this coming winter and how it can help you make better, more informed management decisions when it comes to feeding additional concentrates.

Here’s what he had to say: The winter feeding period is the most expensive stage in most Irish ruminant production systems. Therefore, it is critical that animal nutrition is tailored correctly to each animal group to optimise animal performance.

Grass silage is costly to produce so it is important that its nutritional value is assessed by taking an accurate sample and sending it to a laboratory for chemical analysis.

With animals currently being housed on many farms around the country, now is the time to sample grass silage and other preserved forages so that a plan can be put in place for this year’s winter feeding period.

Benefits of analysing silage

As grass silage forms the major ingredient of many diets, it is very important to quantify the feed value of the silage in order to formulate diets accurately.

By analysing silage it will allow farmers to supplement animals with the appropriate rate of concentrates to meet the animal’s dietary requirements and subsequent performance targets.

Therefore, the level of meal feeding required is determined by the quality of the silage produced.

For example, the target liveweight gain for a spring-born beef weanling over its first winter is 0.6kg/day to allow for cheap weight off grazed grass in their second grazing season.

Table 1 (below): Concentrate supplementation rates (kg/day) necessary for weanlings to grow at 0.6kg/day and for finishing steers (600kg) to grow at 1.0kg/day when offered grass silage of varying dry matter digestibility (DMD) to appetite.

Data source: Teagasc Grange

If this animal is fed average quality silage ad-libitum (65% DMD) that has not been analysed and is only supplementing them with 1kg of concentrate/head/day, then this animal will not reach its target weight at turn-out to grass next spring.

However, if the silage is tested then the correct supplementation of 2kg/day should be fed so the animal is on target. Similarly, if pregnant cows or in-calf heifers are fed high-quality silage ad-libitum (72% DMD) and gaining body condition during the winter, this may lead to a significant increase in calving difficulties and subsequently increased production costs.

In baled silage systems, some farmers may have many different cutting dates during different stages of the growing season and use bales as a tool to manage pre-grazing covers. In these situations, knowing the feed quality of these different cuts is important so certain bales can be fed to the appropriate stock groups on the farm.

Table 2 (below): Silage quality guidelines for different types of stock.

Data source: Teagasc Grange

What a silage analysis report will tell you

The silage sample report will detail the feeding quality characteristics of the silage such as: its dry matter (DM); its digestibility (DMD); the protein content; the fibre content (NDF); the energy value (MJ/UFL); and its intake potential.

It will also give the farmer an indication of how well it fermented by measuring the lactic acid concentrated, ammonia and pH level. This will subsequently help ascertain the stability of the silage at feed out.

How to take a sample

Taking a representative sample of silage for analysis is critical to get accurate analysis results of silage pits or bales.

For example, a standard silage sample (500g) taken from a 500t clamp represents about 0.0001% of fresh material available. Consequently, poor sampling technique is one of the major causes of unreliable silage analysis results. Therefore, farmers should follow these simple steps in the table (below).

These include:

  • Wait five-to-six weeks after ensiling to take samples;
  • Take samples early in the week (Monday to Wednesday) to avoid sample deterioration in post;
  • Use a long core sampler to sample three-to-five well-spaced points on various areas of the surface on the silage pit. The core will sample a profile through the layers of the pit. Take different samples for first and second cuts if layered one on top of the other in a pit;
  • Discard the top 100mm of each core before mixing into a composite sample. The final sample should weigh approximately 500g;
  • Alternatively, sample an open pit and take 10 grab samples in a “W” pattern across the pit face. Ideally, take the sample behind the outer surface of the pit;
  • For bales, use the core sample to sample three-to-four bales per cut located at various locations in the storage stack. Tape up sample holes to avoid spoilage;
  • Alternatively, sample three-to-four bales per cut by grabbing random hand samples throughout the bale when freshly opened;
  • Put the sample into a zip-tie plastic bag. Exclude air, seal well and post immediately.

Finally, it is important that farmers consult their agricultural advisor or nutritionist about the results from their silage analysis in order to plan and formulate diets for this winter.

A silage sample report is valuable information for a farmer to allow them to assess and review their management practices when making silage for the future. Every farmer should ask themselves is their silage fit for purpose and, if required, how could it be improved next year?