Answer:
Steers are male cattle castrated before sexual maturity and raised for beef. While they are being raised, they generate plenty of digestive waste - manure (although the manure is usally also mixed with the bedding material spread in the stalls where the steers are kept and which the manure lands on). Fortunately this manure is very useful for fertilizing soil and thus is collected and sold to those who want to use it to enrich their soil with the nutrients and plant materials contained in the manure - thus helping to offset the cost of raising the steers.
Some other common terms for manure are: cow dung, cow pies, cow chips, organic fertilzer, and muck