Dairy cattle manure is generally a better quality product for plant growing purposes. Rabbit and poultry manures are fine. Watch weed seed problems from horse or sheep manures. Compost is perhaps the best organic amendment. While you can purchase compost, home composting recycles yard prunings and clippings and keeps them out of the landfill.
Compost promotes microbiological activity in soils so necessary for healthy plant growth.
Consider composting to meet your soil improvement needs if you don't already. For more information on soil improvement and how to compost at home, contact your local nursery or garden center, Cooperative Extension office, or botanic gardens. When you do fertilize, there are some points to keep in mind. The predominant reaction of Front Range soils is alkaline or basic. With eastern, acid soils, epsom salts, magnesium sulfate, can be added to promote healthier growth of plants such as tomatoes.