Spreading hydrated lime where cows lay has been a common practice in the battle against mastitis since the 1940s. This form of disinfecting and drying the area below the bedding barrier to protect teats and udders from pathogens worked very well in a 1960s-style tiestall barn.
The lime that was kicked out by the cow went directly into the gutter, then to the manure pile and eventually out onto the soil. It was a win-win.
Unfortunately, it is becoming more noticeable that in modern freestall facilities, this non-soluble and inorganic mineral-based material is remaining on the grooves and textured surfaces that were placed in these concrete floors to provide firm traction for cows as they conduct their daily activities.
This buildup makes floors appear to be wearing down, but in fact, the lime is filling up the grooves and textures; thus, it is creating a flat, smooth, slippery surface. As a result, cows may be injured due to falls, and the herd may struggle with heat detection due to poor confidence in footing.
In some facilities, the floor textures, imprints or grooves that have traditionally lasted a decade or more are now being compromised in only a couple of years. This has begged the questions: Why? What has changed?
Pressure washing to expose the surface on these floors has highlighted an obvious visual change in the coloration, particularly in low areas where liquids tend to sit and the evaporation process takes place. Concrete exposed to only manure and urine takes on a dark brown appearance. However, the floors in question are gray in color and have become exceptionally smoother than others examined.
Upon closer inspection, this gray material can be seen as a coating over the top of the original concrete.
The visible ribs and aggregates on a textured barn floor provide the traction cows need to prevent slips and falls while ensuring solid footing for daily activities like walking and showing signs of heat. Photo courtesy of Tom Woodall.Note the definite ribs and aggregate in the concrete that can be seen in Photo 1 (above). Photo 2, the picture below, is the same floor on the same farm two years later.
Just two years later, the same floor in that barn is smooth and slippery. This is due to the buildup of lime on the floor’s surface. Photo courtesy of Tom Woodall.
It is an interesting fact that if normal clean concrete is heated with a torch, there is very little change in appearance, texture or color until the heated area explodes due to the vaporized moisture in the concrete turning into steam with nowhere to escape.
When lightly dried with a propane torch, this gray material seems to swell, yet it remains adhered to the concrete. It takes very extensive scraping on the floor with hardened tools to remove even a small sample of this residue, as opposed to organic material that will simply burn off, leaving bare and clean concrete.
On normal, clean concrete, heating the surface with a torch produces very little change in appearance, color or texture. Organic material simply burns away. However, if lime has created a residue on the floor, it swells, turns white and hardens upon heating, adhering tightly to the floor. NOTE: Be sure to wear safety glasses if trying this yourself. Photo courtesy of Tom Woodall.
A lab analysis of this gray residue has consistently shown the composition to be 89% to 90% calcium and 4% to 5% magnesium. This is the same ratio of ingredients in quicklime, hydrated lime and crushed limestone. The remaining 5% to 6% is comprised of potassium, phosphorus and sodium, which are all elements naturally found in manure and fertilizer.
Hydrated lime is the key ingredient for concrete, cement powder and mortar. Why are dairy producers being advised to add the equivalent of cement powder to barn floors several times a week and not expect the floors to become smoother over time?
This could be costing some dairies thousands of dollars in livestock injury and losses as well as the expense of trying different methods to regain traction and create a safe environment for their cows.
While liming the stalls may be practiced as a form of mastitis prevention, the problem of mastitis is not necessarily in the bedding. The issue is the dampness that allows bacteria to grow below that barrier – on the surface of the stall. Many things can contribute to the existence of these wet conditions, and lime will have limited effectiveness at best.
Lime is not the silver bullet to solve problems of barn design, stall size, cow density and ventilation. These factors all need to be considered and addressed if there is a serious problem with moisture in cow beds.
Sawdust, straw, peat moss and bedding recovery material are all effective bedding barriers that prevent moisture and pathogens. They are organic material that will not permanently pack in or settle out during evaporation on the floor surface.
If they do stick to the floor, these materials can be removed simply using water. On the contrary, bedding materials and additives like lime, gypsum and recycled drywall will not release when water is added. Water-based liquids actually increase the strength of the bond to concrete.
The current use and overuse of lime in freestalls is costing the industry an untold amount of money due to injuries, lost milk production and challenged reproduction. These things can become constant, reoccurring expenses in an attempt to reduce losses.
The minimal gains observed in many studies of using lime for mastitis control must be balanced with the detriments resulting from lime adhering to the floors and creating a slippery surface. Cows depend on a safe pathway for eating, drinking, milking and regular activities on the dairy.
There are effective antibacterial methods and moisture-absorbent materials available that do not reverse the traction benefits of the floor that we are observing with lime.
In the words of Temple Grandin, Ph.D., professor of animal science, “Nothing is free. There is a price to pay for every action taken.” For dairy producers, that means being informed and aware that there are serious trade-offs in a practice they have been advised to do on a regular basis, and they have not known of the associated problems and costs until now.
