Which Is the Best Manure for the Garden: Cow, Horse or Rabbit?

What Not to Use

• Not all manure is created equal. Due to the possibility of contaminating your garden with pathogens, do not use carnivore manure in your garden. This includes human, dog and cat manure as well as manure from other fish-, egg- or meat-eating animals. Additionally, avoid using raw horse and cow manure, freshly acquired from a stable or cattle rancher. Horses, cows and other grazing ungulates eat grains as well as grass and other greens. Their digestive system is not 100-percent efficient, allowing some seeds to pass through their digestive system intact. If you use raw, uncomposted manure, the unwanted seeds can germinate, requiring you to weed more often, although dairy cows that are purely grain fed will have fewer weed seeds in their manure than free-range cattle.

Cow Manure

• The composition of cow manure varies for many reasons, not the least of which is that the bedding is mixed in with the cow manure. Depending on the bedding material, your manure can be higher or lower in the big three nutrients: nitrogen, phosphorous or potassium. These nutrients are given in percent by weight. Generally speaking, cow manure contains 0.25 percent nitrogen, 0.15 percent phosphorous and 0.25 percent potassium. Because cow manure has low nutrient numbers, you can add as much as you like to dress your garden bed. In addition to the nutrients, the bedding straw or other bedding material collected with the manure will add organic matter to your garden bed, improving the drainage and lightening the soil.

Horse Manure

• As with cow manure, horse manure carries weed seeds and the composition varies with the bedding used in the horse's stall. Horse manure contains approximately 0.70 percent nitrogen, 0.30 percent phosphorous and 0.60 percent potassium by weight. Because of the higher nitrogen level, and because of the weed seeds horses ingest, you must compost horse manure before using it in the garden. This kind of manure is "hot," meaning it will burn your plants if you put it directly on the garden. Again, the bedding material will lighten the soil.

Rabbit Manure

• Rabbits mostly consume greenery such as grass, alfalfa or carrot tops and eat very little seed. Also, rabbits are often kept in cages with wire floors without bedding. This means you get nutrients that are more concentrated, and the numbers reflect that. Rabbit manure contains 2.4 percent nitrogen, 1.4 percent phosphorous and 0.6 percent potassium by weight. Because of the size of a rabbit, and how few rabbits are bred compared to cows, rabbit manure is generally not available in quantities as large as horse and cow manure.

What Is Best?

• As always, which manure is best depends on your particular situation. If you are concerned about getting weed seeds in your garden, rabbit manure is the safest product to use. It is also very high in nutrients, especially nitrogen. If you cannot wait to compost the manure first, then cow manure will safely improve your garden soil, although any manure should always be composted before use in a vegetable garden to reduce the risk of contaminating the soil with E. coli and other bacteria. If you are growing mushrooms, you want the hottest manure you can get -- horse manure. If your soil is poor in potassium, horse manure has the highest ratio of potassium to nitrogen. If your soil is poor in phosphorous, rabbit manure has the highest ratio of phosphorous to nitrogen.