Livestock manure can improve the nitrogen level of your soil. With that said, the diet of livestock is hay that is full of weed seeds which have the potential to germinate in your garden. Horse manure for example adds organic matter and nutrients to the soil but as it is also full of material like dried hay it will remove nitrogen when it decomposes and you’ll have to add more fertilizer to correct that.
Using manure is fine but make sure it is a year or two old before applying it to your garden. This will ensure it is fully decomposed and that the salts have come out. Too much salt can be harmful to plants.
Quality compost or completely decomposed manure should be dark brown with little original material visible. Most people are not aware, that that it should not smell fresh of the ranch. The good manure should have an earthy smell to it.