Current Progressive Dairy digital edition

Sliced bread and silage piles

Published on 09 August 2021

The most common summertime lunch has to be ham and cheese sandwiches. While writing an article for this issue about covering silage piles and snacking on one such sandwich, I had a revelation about how opening a bagged loaf of sliced bread is much like opening a silage pile or ag bag.

Every time I go to open my bread, I take great care to only take out as many slices as needed, and to not jostle the bag too much, so I don’t introduce new air into the bag. Why do I do this? I like to make my bread last as long as physically possible so it doesn’t get moldy. The minute I open a loaf of bread, it’s all downhill from there. With new air comes new organisms that will grow mold and be the end of my perfectly good loaf of bread.



This thought definitely took me back to grade school science, where we learned about germs and dirty surfaces by testing them on slices of bread. Remember how those gross molds spread and grew? If you leave a slice of bread out exposed on the counter, I guarantee you it is growing mold within 48 hours. The same happens to silage piles once opened.

Peter Robinson, a UC – Davis extension specialist, studied the rate of penetration of molds and yeasts into silage piles caused by air entry between the cut plastic and the silage surface after the piles were opened. (Pile guide: Silage surface and face management). He found that the farther you go into a pile as you’re feeding out, the penetration of molds and yeasts moves farther and farther back from the exposed face if the silage face is not matched to the silage feedout rate.

Molds damage silage quality, and in severe cases they lead to dangerous mycotoxins that can make silage unfit to eat. I know I wouldn’t eat any sort of moldy bread, so why would you want or expect your cows to eat moldy silage either? Producers need to understand which molds are harmful and how to limit their development.

The three most common molds that grow in silages include Penicillium roqueforti, Aspergillus fumigatus and Monascus ruber. The easy way to differentiate the three is by color. P. roqueforti is green/blue, A. fumigatus is yellow/green, and M. ruber appears red surrounded by white. Other spoilage molds include Mucor and Monila, which typically are white to grayish in color.

Mold growth varies depending on type. Some types thrive while the crop is growing in the field, while others begin to flourish during storage. Storage molds originate from soil-borne spores that are brought into the silo and require oxygen from air for the molds to sporulate and begin growing.


The final step of harvest – and one of the most critical steps – is to effectively cover and seal bunkers and piles to limit oxygen and protect the forages (Safe, efficient and effective silage piles). Prior to covering, make sure the people involved receive some instruction about the process and contingencies that may need to be considered.

So maybe the next time you open up a loaf of bread to make a sandwich, you too will think about the similarities it has with a silage pile. end mark

Audrey Schmitz
  • Audrey Schmitz

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