Silage: Production and Feeding – Part IV

For last couple of months, I have been talking about silage. So far I have discussed what is silage, what is silo, advantages and disadvantages of silage, crops commonly used for silage, the ensiling process and silos.

Today, I will be discussing the factors that affect silage quality.

There are many factors that affect the quality of silage during storage and also at the time of feeding. Some important factors include maturity stage of crops, type of stored crops, moisture content and length of chop.

Stage of maturity

The stage of maturity of any crops for silage has the greatest effect on silage quality.

In general, as the crops mature or age, silage quality declines, and as a result, inferior performance may be seen in the animal. It is recommended to follow general guidelines for harvesting various crops for silage.

Below are some examples of crops and their ideal maturity age for harvest:

Corn – when kernels are dented and black layers are visible;

Alfalfa – at bud to early bloom;

Cool season grasses – first cutting at boot to early head and thereafter at four- to six-week intervals;

Small grains – boot to early head;

Forage sorghum – 40 inches tall or late boot stage;

Grain sorghum – late milk to late dough;

Sorghum, sudangrass and millet – 40 inches tall or boot stage, whichever appears first; and

Soybeans – late bloom, seeds started to form in pods and before lower leaves fall.

These are some guidelines. It is important to remember that the type or class of livestock to be fed is also significant and should be taken into account before selecting crops and their stage for harvesting.

Moisture and temperature

Moisture content varies significantly depending on the crop ensiled and the type of silo used. If the crop is too dry during harvesting, extra moisture needs to be added to ensure good packing and proper fermentation. Silage temperatures rise due to low moisture content because bacteria, yeast and molds become more active.

If the silage is overheated, it becomes brown to black in color with burned sugar odor. It is really important to monitor moisture and temperature because overheating reduces feeding value and increases dry matter loss, and in extreme cases, it may result in combustion.

On the other hand, silage that is too wet is not good, either. Excessive moisture in the silage will result in loss of nutrients through excessive seepage. It also results in silage being packed too tightly, so all the oxygen is used up before the temperature reaches to 80 degrees Fahrenheit.

As a result, undesirable bacteria become active, use carbohydrates and produce an unpleasant odor.

Also, protein can be broken down by other organisms, resulting odor of ammonia. Overall, this creates an unpalatable silage with poor quality and low feeding value.

In general, moisture content should be kept about 65 to 70 percent to get good quality and proper packing of the silage, especially if the silage is prepared using stacks, trenches or bunkers. Hence, moisture content determination is very important, and this can be measured by using a moisture meter or by drying and weighing silage samples.

I will continue this discussion on other factors affecting silage quality, silage preservatives and additives, and feeding silage in the coming months extension columns. Please keep an eye out for these.

Anowar Islam is an associate professor and the University of Wyoming Extension forage specialist in the Department of Plant Sciences in the College of Agriculture and Natural Resources. He can be reached at 307-766-4151 or mislam@uwyo.edu.