That wasn't the only Pig War, though. Although somewhat misnamed due to the lack of any actual warfare, there was another Pig War some fifty years later that, although a bit more boring, was one of the most important events of the twentieth century.
Austria-Hungary had been using Serbia as a sort of client state since the end of the first Pig War mentioned above. By 1903, about 90% of Serbia's foreign trade was conducted with Austria-Hungary, mostly in livestock such as pork. This isn't to say that Serbia didn't benefit from this trade, but in the minds of many Serbians they could have benefitted a lot more if Austria-Hungary left them alone. Also, Serbia had gotten it in their collective head that they might ought to establish an ethnically based state for Slavs, an idea that the Austro-Hungarians didn't like at all, since it would probably entail a large loss of Austro-Hungarian population and territory to this new hypothetical Pan-Slavic state.
So in 1904, in a move apparently meant to test Austrian determination to keep Serbia economically subordinate, Serbia stopped importing Austrian munitions and started importing French ones instead. After getting away with that, Serbia fell in with those Bulgarians, whom Austria-Hungary felt were a bad influence. When Serbia and Bulgaria formed a trade union that year, it put Austrian goods at a strong disadvantage to others because of the higher tariffs on them. Predictably, Austria-Hungary didn't like this and so they decided to do something about it in 1906, when they totally stopped the importation of Serbian pork.
Serbia just smiled grimly in the manner of an action hero and asked not to be made to laugh. Displaying remarkable adaptability, Serbia then snared some French investors to help them build the infrastructure required for international meat trading. When that had been completed, they started pressuring the then Austrian provinces of Bosnia and Herzegovina for an outlet to the Adriatic. They also opened trade relations with Turkey, Egypt, Germany, and Greece. Serbian products found ripe markets in all of these places and the Serbian economy boomed, much to the chagrin of the Vienna government, who had been hoping to reduce Serbian independence and by doing so put an end to the Pan-Slavic movements of the day.
Serbia couldn't have done all of this without powerful friends, chief among which was Russia. As noted before, Pan-Slavism was fairly popular at the time and Russia was Slavic just like Serbia, so it was fairly natural for them to ally. Of course, this meant that Russia would have been dragged into any actual fighting wars that may have developed over this issue, but Tsarist Russia was nothing if not belligerent at this time, so they didn't mind. War almost did flare up over this between Austria-Hungary and Russia, but a German ultimatum in 1909 (presumably, although not certainly, to back Russia and Serbia against Austria-Hungary) brought an end to the Pig War by forcing Austria-Hungary to accept the changes in their relationship with their former client state. A new trade agreement between Austria-Hungary and Serbia was put into place in 1909.
Although the series of diplomatic maneuvers on all sides had ended, the social forces that brought the situation into being would last for years to come. Eventually, Pan-Slavism would lead to the assassination of a certain Archduke and throw everyone involved back into conflict, except this time things wouldn't be so easily resolved. It took the worst flu outbreak in history to stop the war that would result. According to CrazyIvan's writeup here, it was a form of swine flu.
Sources: http://www.worldwar1.com/tlpwars.htm,
http://www.onwar.com/aced/nation/yak/yugoslavia/fpigwar1906.htm