Just like we don’t want to eat moldy bread, cows can’t thrive on contaminated silage. If you want better outcomes for your herd, it’s crucial to focus on feed quality. Clean, high-quality feed minimizes the risk of contaminants and harmful microbes that can compromise cattle health and performance. Among these microbes, spoilage yeasts are particularly concerning due to their significant impact on silage quality and animal well-being.
Embodying a “clean feed” approach emphasizes the importance of maintaining high-quality, hygienic silage as the foundation for healthy rumen function, leading to improved production outcomes. Proper on-farm practices and the addition of microbial solutions can enhance feed efficiency and digestion. Starting with forage inoculants helps protect silage from naturally occurring, damaging microbes. Understanding the role of spoilage yeasts in silage is critical, as their presence can significantly influence feed quality and herd performance.
What are yeasts?
Yeasts are microorganisms naturally present in soil and on plant surfaces. Although typically found in lower numbers than bacteria, yeasts can significantly impact silage quality. While some yeast species are beneficial, others may cause significant problems during silage feedout. Probiotic yeasts such as Saccharomyces cerevisiae CNCM I-1077 help by scavenging oxygen and stabilizing rumen pH, which is crucial for animal health and digestion. However, spoilage yeast activity can lead to substantial dry matter (DM) and nutrient losses, heating and ultimately pave the way for opportunistic microorganisms, resulting in massive deterioration of the silage.
Spoilage yeasts and aerobic deterioration
Spoilage yeasts, that particularly are able to feed on lactic acid, can significantly harm silage quality. When a silo is opened and air enters, these yeasts become active, eating up residual sugars and lactic acid. This raises the pH, creating a welcoming environment for other harmful microbes. This process, called aerobic spoilage, leads to rising temperatures and a musty smell. These yeasts are too small to see, so spotting the problem early can be tough (Figure 1).
Moldy bread
The effects of spoilage yeasts in silage can be compared to mold growth on a loaf of bread. Just as bread contains preservatives to maintain shelf life, silage relies on fermentation acids to keep its quality. When you open a loaf of bread, the preservatives help keep yeasts and molds at bay for a time, but eventually, as the bread is exposed to air, mold will start to grow. Similarly, when a silo is opened, it introduces oxygen, allowing spoilage yeasts to become active. By the time the expiration date of the bread is around the corner, we can extend the shelf life by refrigerating it – but not to silages.
Just as keeping bread at a low temperature can delay mold growth, proper silage management strategies such as minimizing air penetration and exposure by proper packing and covering, using effective inoculants and adequate feedout management are essential to prevent spoilage and maintain feed quality. However, despite all precautions, both bread and silage will eventually spoil once exposed to air over time.
Combating spoilage yeasts
To combat spoilage yeasts, it's essential to minimize air exposure and ensure rapid initial fermentation. Effective inoculants can inhibit or minimize these yeasts’ activity. Maintaining a good feedout rate to match air penetration also helps prevent aerobic spoilage (Figure 2). Harvesting plants later in the season or ensiling high-starch crops such as whole-plant corn, earlage and high-moisture corn can favor spoilage yeast growth, requiring stringent silage management practices to preserve feed quality and prevent losses of spoiled feed and ultimately lowered cow health and production.
Impact on animal health and performance
Feeding spoiled silage or silage high in yeasts can hurt your herd’s health and production. When a total mixed ration (TMR) is made with spoiled silage, it heats up faster and tastes worse, leading cows to eat less and reducing their productivity. High yeast levels compete with the microbes in a cow’s rumen, lowering digestibility and nutrient absorption.
Research shows that animals consuming feeds contaminated with high populations of spoilage yeasts often experience reduced fiber digestibility (NDF-D). Early studies indicated that incorporating just 5% spoiled silage into a ration decreased NDF-D by 7.2 points. A decade later, Dr. Limin Kung’s research found that high levels of spoilage yeast (Candida valida) resulted in a 10-point decrease in NDF-D – nearly a 23% reduction compared to control TMR samples. A 1-point reduction in NDF-D can equate to a loss of 0.4 to 0.55 pound of fat-corrected milk (FCM) per cow daily.
Silage is a vital component of your herd's diet and a significant investment for your operation. Despite protection, it remains susceptible to damaging microbes like spoilage yeasts, bacteria and molds, which may produce harmful mycotoxins. By incorporating research-proven inoculants into your silage and implementing strict on-farm hygiene protocols, you can protect your investment and minimize waste. Just as you take care of bread to prevent spoilage, taking a diligent approach to silage ensures your herd receives the highest-quality feed, ultimately enhancing their health and productivity.
References omitted but are available upon request by sending an email to the editor.
