Horse vs. Cow Manure: While both horse and cow manure can be used, they have distinct characteristics. Horse manure often possesses a finer texture due to their digestion process and can sometimes be less prone to certain contaminants than cow manure. However, both can produce robust mycelium growth if prepared correctly.

Horse manure usually scores slightly better in all categories with a 1.5–1.0–1.5 N-P-K rating and a shorter composting time. However, unlike cow manure, you can’t buy it bagged. Although horse manure breaks down faster than cow manure, it still should be well composted before using it on a garden during the growing season.

Horse manure has a higher nitrogen and nutrient content than cow dung. Moreover, ​​horse waste contains significantly less water than cow manure; therefore, it can include up to twice as much nitrogen when dried. Horse manure requires composting or aging to kill weed seeds, larvae, and pathogens.

Horse manure slightly outpaces cow manure in some, but not all, nutrients. Getty Horse and cow wastes are both valuable garden amendments. While neither has the high amounts of nutrients found in bat guano, for example, both manures are useful -- and inescapable -- byproducts of farming and ranching.