1. Forage maturity:
More mature or coarser forages tend to be bulkier and more resistant to processing and mixing than less mature, finer forages. As forages mature, plants become taller, their cells increase in size, and cell walls thicken and become more lignified. This makes them tougher and more resistant to cutting. Also, as plants mature more hollow space develops, such as in hollow stems, which make the bales and forage lighter and more prone to balling, wrapping around the auger, and riding high in the mixer. This decreases cutting efficiency and increases processing time and the potential for spillage. In general, it may be that round bales of coarser forages are better handled in slightly larger mixers than are otherwise acceptable for better quality forages.
2. Forage type:
As a general rule, legumes such as alfalfa, clover and pea vine will process easier and more efficiently than grasses, with straws, a completely mature grass, being the most extreme case. This is largely due to differences in anatomical structure and distribution of fiber and lignin within the plants.
While grasses have structural fiber and lignin distributed throughout the entire plant, in alfalfa it is mainly concentrated in the stems. Alfalfa leaves are small and fragile and can make up a minimum of 35% of poor quality alfalfa bales to as much as 65% of high quality bales. In addition the stem fiber of alfalfa is more brittle than that in grasses and breaks easier when processed. Consequently, we can expect legume bales such as alfalfa hay to be heavier, have less long material, and process more rapidly than bales of grass of equal size and physiological maturity. Grass bales will generally require more room to process than similarly sized bales of alfalfa.
3. Forage moisture content:
In general, forages become more brittle and are easier to process when they are dry, especially with alfalfa and other legumes. But this is not always the case when processing with a vertical TMR mixer. As forage moisture content increases, the cells of the plants become more pliable and “plastic”, and thus more resistant to breakage and cutting. However, in a TMR mixer, the added weight of sufficient moisture, such as in silage bales, makes them heavy and prone to sinking to the bottom of the mixer where cutting is faster and more effective. It appears that the toughest forage and most resistant to processing may be high moisture grass hay, due to the combined effects of anatomy and moisture content. Adding extra moisture and weight to dry forages and high moisture hay by adding haylage, corn silage or other high moisture ingredients, or even tap water, can dramatically increase the efficiency of processing (see Adding other ingredients and Adding water, below).
4. Adding other ingredients:
When making TMR rations, long forages are ideally processed rapidly to their optimal length, and then the remaining ingredients are added as quickly as possible and mixed for a minimum amount of time. This minimizes total mixing time and prevents excessive particle size reduction. However, with round bales of long hay, and even high moisture hay, it is often advantageous to add haylage, corn silage or other high moisture ingredients, or even the grain, as soon as the round bale has been cut into large pieces and is mostly fully disassembled. This will dramatically improve product flow, the cutting rate and uniformity of particle size reduction. If particle size reduction of the haylage or corn silage is a concern, part of the final amount could be added.
5. Adding water:
Processing of dry or high moisture hay can be particularly challenging if moisture is not added. The addition of moisture weighs down the hay and reduces its tendency to bunch and climb within the mixer. This is best achieved by the addition of haylage, corn or cereal silage, or wet grains and byproducts. If these are not available addition of large volumes of tap water as a spray or using other methods of distribution also works well. As a rule of thumb, water can be added until the total mix approaches a moisture content of as much as fifty percent (50%). A minimum recommended add rate for dry hay is between one third and one half the weight of the bale. For a 1000 lb bale, this would be roughly 300 to 500 lbs, or 40 to 60 US gallons, of water. This would result in forage with a moisture content of 34% to 41%, which should be acceptable for feeding under most conditions, especially if further mixed with grain. Obviously, some adaptation is required for water addition in freezing conditions, but is readily accomplished.
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