After water, pasture for the animals was the most important commodity on the trip. Without proper nourishment horses could not carry their riders, pack mules could not carry their loads, and cattle would weaken and die. Firewood was important to the colonists for warmth and for cooking, but they could survive several days without it. That was not the case with pasturage for the animals.
The Spanish word for pasturage is "pasto." (D. G.)