Is TMR Heating Costing You More Than You Think?

Feeding adequate quantities of high-quality feed is the foundation of profitable milk production. However, during warmer weather, many dairy farms unknowingly lose valuable nutrients before cows have the opportunity to consume them.

TMR heating is a common challenge during summer, particularly when silage is exposed to oxygen during feedout. While heating is often viewed as a feed management issue, its impact extends far beyond causing feed to get hot in the feed bunk. As yeasts and moulds begin to multiply, nutrients are lost, feed quality deteriorates, and performance can suffer.

During periods of warm weather, producers may spend considerable time rebalancing a ration to meet the changing nutritional requirements of the herd, but if heating occurs, the ration consumed by the cow may be significantly different from the ration originally formulated.

What Causes TMR Heating?

Silage naturally contains yeast and mould populations that remain largely inactive while oxygen is excluded. Once silage is exposed to air during feed out, conditions change rapidly.

Lactic acid present in silage serves as an energy source for spoilage organisms. In the presence of oxygen and fermentable sugars, yeasts and moulds begin to multiply, driving secondary fermentation within the feed. As microbial activity increases, and expensive nutrients are used up, heat is generated throughout the ration.

The result is a TMR that gradually heats up, often long before obvious spoilage becomes visible.

While heating is often judged by temperature alone, the real concern is what is happening to the nutrients within the ration. As yeasts and moulds multiply, valuable energy and protein are consumed by spoilage organisms, reducing the feed value available to the cow before it can support milk production and performance.

How TMR Heating Affects Feed Quality And Performance

As spoilage progresses, feed value begins to decline. Digestibility can be reduced, nutrient losses increase, and the risk of mycotoxin contamination rises. At the same time, heated feed often develops changes in smell and freshness that reduce palatability. This can have a direct impact on dry matter intake.

Cows are naturally selective feeders and are less likely to consume feed that has begun to deteriorate. During periods of warm weather, when intake is already be under pressure, reduced palatability can further limit nutrient consumption and increase feed refusals.

The consequences often extend beyond intake alone. Reduced nutrient supply, lower digestibility and increased exposure to spoilage organisms can all contribute to poorer animal performance and a higher cost of production.

In simple terms, nutrients that have already been paid for are being lost before they ever reach the cow.

The Hidden Risk Of Mycotoxins

One of the less visible consequences of TMR heating is the increased risk of mycotoxin exposure.

As mould populations develop within feed, they can produce secondary metabolites known as mycotoxins. These compounds have been associated with reduced feed intake, poorer performance and wider health challenges within the herd.

The challenge is that feed can appear relatively normal while mycotoxin levels are already affecting performance. Producers may therefore focus on the visible symptoms of feed heating while overlooking the hidden impact of fungal contamination.

Preventing feed spoilage is not simply about preserving feed quality. It is also about reducing the wider risks associated with mould growth and mycotoxin exposure.

Figure 1. Untreated TMR immediately after feedout and after 24 hours.

Figure 2. TMR treated with Cool-It immediately after feedout and after 24 hours.

Preventing TMR Heating During Summer

Good feed management remains the first line of defence. Fresh TMR preparation, effective clamp management, regular feed push-ups and prompt removal of leftovers can all help reduce the opportunity for spoilage organisms to multiply. However, nutritional solutions can also play an important role.

UFAC’s Cool-It is a glycerine-based feed preservative designed specifically to help reduce the growth of yeasts and moulds within TMRs. By providing key ingredients that actively help to limit microbial activity, Cool-It helps maintain feed freshness, improve trough life and preserve the nutritional value of the ration.

Importantly, Cool-It is designed to address more than just heating. The product also contains a mycotoxin binder to help trap mycotoxins that may already be present within feed ingredients, helping reduce the risks associated with mycotoxin contamination.

Unlike many preservative-only approaches, Cool-It also contains glycerine and propylene glycol. These ingredients provide a source of glucogenic energy, helping replenish some of the energy lost during the secondary fermentation processes responsible for feed heating.

By helping preserve feed quality, reduce spoilage and manage mycotoxin risk, Cool-It supports the objective of ensuring cows receive the nutrients intended within the original ration.

TMR heating is often viewed as a feed spoilage issue. In reality, it is a nutrient supply issue.

Every degree of heating represents valuable nutrients being lost before they can support milk production. Protecting feed quality means protecting nutrient density, maintaining dry matter intake and maximising the value of the feed already being put in front of the cow.

For a typical high-yielding cow consuming 24kg of dry matter TMR at 12MJ/kg DM and producing 32kg of milk, a 10% reduction in dry matter intake could equate to approximately 5.3kg less milk per day. In a 200-cow herd, this could represent as much as 1,000kg of lost milk daily before taking into account the additional reduction in nutrient density that occurs as feed heats and deteriorates.

Cool-It has been developed to help minimise these losses by maintaining freshness, improving trough life, reducing mycotoxicosis and conserving nutrients for better livestock performance. At the recommended average feeding rate of 500g/cow/day based on UFAC calculations, this can provide an additional 12MJ of metabolisable energy and support an additional 2.26kg of milk per cow per day and an ROI of 1.95:1.

As summer temperatures rise, managing TMR heating can be just as important as managing heat stress itself.