That's cool. As a collective group, the demand curve remains the same though, since only an insignificant number of customers buy more livestock when prices are higher (Ie. The customers who would rather buy a clownfish at $30 and refuse at $15).
Now, if 100% of the group is like that for livestock, then and only then would that contradict the theory.
If 100% of the people buy more livestock when prices are higher, then you have what is called a giffen good which doesn't really exist in the real world.
http://en2.wikipedia.org/wiki/Giffen_paradox
"For most products, price elasticity of demand is negative. In other words, price and demand pull in opposite directions; price goes up and quantity demanded goes down, or vice versa. Giffen goods are an exception to this. Their price elasticity of demand is positive. When price goes up the quantity demanded also goes up, and vice versa. In order to be a true Giffen good, price must be the only thing that changes to get a change in demand.
...
Despite years of searching, no generally agreed upon example has been found. "
Harvard Reference
http://ksgnotes1.harvard.edu/researc...4?OpenDocument
"Economists have long searched, unsuccessfully, for convincing evidence of a Giffen behavior, i.e., consumers who, under some circumstances, respond to an increase in the price of a good by demanding more of it."
Everything has an explanation you see. Livestock is definitely not a Giffen good. Lots of references out there for Giffen goods and the Paradox.