Wikipedia

"Boar taint is the offensive odor or taste that can be evident during the cooking or eating of pork or pork products derived from non-castrated male pigs once they reach puberty. Boar taint is found in around 20% of entire male finishing pigs. … Studies show that about 75% of consumers are sensitive to boar taint, leading pork producers to control this in order to maximize profits. …

Boar taint is caused by the accumulation of two compounds – androstenone and skatole – in the fat of male pigs. Androstenone (a male pheromone) is produced in the testes as male pigs reach puberty and gives the meat a urine or sweat flavour, while skatole (a byproduct of intestinal bacteria, or bacterial metabolite of the amino acid tryptophan) is produced in both male and female pigs and gives the meat a 'fecal' flavour. …"