Bale Size and TMR Mixers: How Bale Characteristics Impact Efficiency and Nutrition

As we enter this year’s haying season, it’s important to think beyond just how big a bale your tractor can carry. If you’re feeding baled forage using vertical TMR mixers, the size and characteristics of your bales can directly influence mixer performance, feed batching, and ultimately, herd nutrition.

Traditionally, cow-calf operations focused on producing the largest bales possible (often 6’x5’) to reduce costs tied to twine, wrap, labor, handling, and weathering losses. However, with TMR feeding systems, the goal shifts from “biggest bale possible” to “optimal bale size for nutrition and efficiency.” Smaller bales or pre-chopped forages may be more efficient for mixing, allow full bales to be fed, reduce capital investment in mixer size, and improve the precision of your rations.

Why Bale Size Matters in TMR Feeding

When working with vertical TMR mixers, bale size must align with the capacity of the mixer. Mixer capacity is measured in cubic feet (cubic ft.) and influenced by both bale weight and hay density.

• Average hay density: Long hay = 3 lbs./cubic ft.
• After processing (cut below 6”): Density doubles to about 6–7 lbs./cubic ft.

For example, a 1,000 lb. round bale of dry hay occupies roughly 330 cubic ft. before processing. During initial mixing, hay tends to clump at the ends of the mixer, which can require up to 50% additional volume to prevent spillage. That means a 450–500 cubic ft. mixer is often needed to process a single 1,000 lb. bale efficiently. Smaller mixers (around 350 cubic ft.) may manage with care or extensions but require more time and effort.

The Physics of Processing Bales

Mixing performance decreases as more bales are added:

• First bale: Adds ~6 minutes to mixing time.
• Second bale: Adds ~10 minutes.
• Third bale: Can add 20–40 minutes, making it slower than mixing two smaller loads.

Why? Long hay floats on denser, processed forage, delaying cutting and circulation. In most cases, two bales are the practical limit for efficient mixing.

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Factors That Affect Bale Weight and Mixer Choice

The weight of a bale depends on size, density, and moisture content.

• Standard balers pack dry hay at 10–12 lbs./cubic ft.
• High-density balers (especially with knives) can pack up to 16–18 lbs./cubic ft.
• Wet bales (baleage) have higher total weight, but their moisture helps them settle faster in the mixer.

Hay Equivalent (HE) calculation for wet bales:

HE = Wet bale weight × (Dry matter % ÷ 100) ÷ 0.85

Choosing the Right Mixer for Bale Size

The physical design of the mixer also plays a role. If space between the auger and wall is too narrow, bales will “ride” instead of dropping into the knives, slowing down processing. Twin auger mixers help with flow but still face the same hay-equivalent limits.

• 300–400 cubic ft. mixers: Best for 4×4 bales or equivalent hay amounts.
• 450–600 cubic ft. mixers (single/twin): Can handle most 4×4 and 4×5 bales, and lighter 4×6 bales.
• 650+ cubic ft. twin auger mixers: Needed for dense 4×6 and most 5×6 bales.

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Optimizing Bale Size for Nutrition and Cost

Many smaller operations still produce 5×6 bales to cut production and handling costs. But when feeding through a TMR system, this often means investing in a larger, more expensive twin-auger mixer than what’s truly needed for the herd’s ration.

By shifting to smaller bales or using a knife-equipped baler, producers can:

• Match bale size with the optimal mixer capacity.
• Lower equipment costs. Improve ration consistency.
• Reduce processing time and labor.
• Better meet the nutritional needs of dairy cows and beef herds.

Final Thoughts

Choosing the right bale size isn’t just about field efficiency; it’s about ensuring your TMR feeding system works at its best. By aligning bale size, density, and mixer capacity, you can improve efficiency, reduce costs, and deliver rations that keep your herd productive and healthy.

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