Synonyms for Diestrual (same or very similar meaning)
WordNet sense 1 ((of animals that have several estrous cycles in one breeding season) in a period of sexual inactivity):
diestrous, dioestrous, dioestrualWordNet sense 2 ((of lower mammals) not in a state of estrus; not in heat):
anestrousFrom the ODE community, based on WordNetadd/edit