An average-sized horse requires about 1 to 2 ounces of salt per day, depending on body weight, weather, and work level. | Photo: The Horse Staff

Q. I started feeding my horses 2 tablespoons of salt each day added to their rations. However, one of my horses won’t eat it. I’ve also noticed he uses much less of his salt block than my other horses. Why is he consuming less salt, and how can I make sure he’s getting enough?

A. An average-sized horse requires about 1 to 2 ounces of salt per day, depending on body weight, weather, and work level. Heavily working horses will require more than this. Horse sweat contains a lot of electrolytes, so if not replenished, body stores can decline. Because sodium is so important, the body has several mechanisms to conserve sodium when horses aren’t consuming enough.

Blood volume drops when sodium levels drop because fluid and sodium tend to follow each other. This reduction in blood volume causes decreased blood pressure, which triggers baroreceptors—mechanoreceptors (a sense organ or cell that responds to mechanical stimuli) that sense pressure changes in arterial walls. When blood pressure drops, they stimulate the nervous system as well as hormones that act on the kidneys to reduce sodium excretion through urine. Because sodium and water move together, urine with lower sodium content will be more concentrated because it also contains less water. This is why when you are dehydrated, your urine is more concentrated and a darker yellow. The darker your urine, the more dehydrated you are