Q. I have been researching different types of salt and mineral blocks available for horses. I’m trying to determine if one kind is better than another, but there are quite a few different types! Is there one type I should choose over the others?

A. There are a large number of different types of salt and mineral blocks available at feed stores. Here in California, I most commonly see plain white salt blocks, red mineralized salt blocks, and rock salt on a rope. However, in certain parts of the country, other salt blocks that contain supplemental selenium, cobalt, or sulfur are common, as well.

Despite being visually quite different and having names that suggest significantly different nutritional compositions, all these salt sources have the similarity that they are all predominantly sodium chloride—more than 92% sodium chloride, based on the analysis I found.

Many people rely on the brown trace mineralized blocks as a trace mineral supplement to their horse’s forage. However, the amounts of key trace minerals such as zinc and copper are likely not being consumed at high enough quantities to ensure the horse’s needs are being met or the diet’s trace mineral profile is well balanced.

The assumption with trace mineral blocks is that your horse will consume their daily sodium needs from the block and, at the same time, consume the other minerals. While they are of course consuming trace minerals from these blocks as they consume the salt it may not be enough to meet their needs.

For example, a 1,100-pound horse has a daily maintenance sodium requirement of just under 10 grams of sodium, which can be met by consuming about an ounce of sodium chloride salt. Based on one commercially available trace mineralized block, if your horse consumed an ounce (28.3 grams) of salt he would also consume 100 mg of zinc and 8.5 mg of copper. This will most likely not be enough to meet the shortfall remaining after consuming 1.5 to 2% of body weight as hay or pasture. Natural rock salt often contains even lower amounts of essential trace minerals.

Because these forms of salt are often more expensive than plain white blocks and do not ensure adequate trace mineral nutrition, my preference is to save money and just buy the plain white salt block.

Of course, the other issue is that not all horses will consume an ounce of salt from a block each day despite the fact that they do have a desire to consume sodium. This results in an even lower trace mineral intake. Many times I go in stalls and the salt block is in the corner covered with bedding, dust, and possibly manure. Clearly they are not being licked on a daily basis.

While the rock salt and trace mineralized salt might not fully meet your horse’s nutritional needs, some horses appear to prefer their taste, preferentially consuming them over a plain white salt block. In this case the extra expense might be worthwhile and the trace minerals that are consumed are unlikely going to negatively impact the overall diet if you are providing other source of trace minerals in the ration.

My preference is to give loose salt in their feed at a rate of 1 tablespoon per 500 pounds of body weight, along with additional salt block access. This way I know they are consuming their maintenance sodium requirement and have additional sat available should they desire.

To insure trace mineral needs are met I find feeding a ration balancing feed or supplement that is designed to provide those nutrients that might be missing or deficient in a forage based diet to be more successful than relying on a trace mineralized salt block.