We consider the problem of symbolic integration of G(x, y(x))dx where G is rational and y(x) is a non algebraic solution of a differential equation y ′ (x) = F (x, y(x)) with F rational. As y is transcendental, the Galois action generates a family of parametrized integrals I(x, h) = G(x, y(x, h))dx. We prove that I(x, h) is either differentially transcendental or up to parametrization change satisfies a linear differential equation in h with constant coefficients, called a telescoper. This notion generalizes elementary integration. We present an algorithm to compute such telescoper given a priori bound on their order and degree ord, N with complexity Õ(N ω+1 ord ω−1 + Nord ω+3 ). For the specific foliation y = ln x, a more complete algorithm without an a priori bound is presented. Oppositely, non existence of telescoper is proven for a classical planar Hamiltonian system. As an application, we present an algorithm which always finds, if they exist, the Liouvillian solutions of a planar rational vector field, given a bound large enough for some notion of complexity height.