Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of sodium selenate as a nutritional feed additive for ruminants, when used via an intraruminal bolus in ruminants. The EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) Panel concludes that based on (i) the estimation of the release of selenium from the bolus, (ii) the similarities in bioavailability with sodium selenite, (iii) the experience with the use of boluses in ruminant nutrition and (iv) the wide margin of safety compared with the maximum tolerable levels of selenium in ruminants, the additive is safe for ruminants. The use of sodium selenate by bolus administration providing a selenium intake not exceeding that resulting from the maximum authorised EU level of total selenium in feed presents no concerns for consumer safety. The additive does not pose a risk to users by inhalation and is considered as non-corrosive but irritant for the skin and the eyes. The FEEDAP Panel considers the additive as a skin sensitiser and respiratory sensitiser. The additive under assessment, in its intended use as complementary feed for ruminants in the form of boluses, is a substitute for other authorised selenium additives and will not further increase the environmental burden of selenium. Based on two studies submitted in cattle and sheep and studies from the literature, the FEEDAP Panel concludes that sodium selenate delivered by a bolus to ruminants is an efficacious source of selenium in meeting the animals' requirements. The Panel posed some recommendations regarding the use of the bolus, especially in small size ruminants. The Panel also posed a remark, concerning the zinc content of the bolus from which the additive is delivered.