2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/145000We study Dehn surgeries on null-homotopic knots that yield fibred $3$--manifolds when an additional (but natural) homological restriction is imposed. The major tool used is Gabai's theory of sutured manifold decomposition. Such surgeries are negative examples to a question of Michel Boileau. Another result we will prove is about surgeries which reduce the Thurston norm of a fibred manifold.15 pagesGeometric Topology57M99; 57R30text