  In this paper, we work with simple and finite graphs. We study a
generalization of the \emph{Cage Problem}, which has been widely studied since
cages were introduced by Tutte \cite{T47} in 1947 and after Erd\" os and Sachs
\cite{ES63} proved their existence in 1963. An \emph{$(r,g)$-graph} is an
$r$-regular graph in which the shortest cycle has length equal to $g$; that is,
it is an $r$-regular graph with girth $g$. An \emph{$(r,g)$-cage} is an
$(r,g)$-graph with the smallest possible number of vertices among all
$(r,g)$-graphs; the order of an $(r,g)$-cage is denoted by $n(r,g)$. The Cage
Problem consists of finding $(r,g)$-cages; it is well-known that $(r,g)$-cages
have been determined only for very limited sets of parameter pairs $(r, g)$.
There exists a simple lower bound for $n(r,g)$, given by Moore and denoted by
$n_0(r,g)$. The cages that attain this bound are called \emph{Moore cages}.
