The improvement of neonatal viability by maternal nutrition during gestation has been widely studied in numerous species. Recent investigations have explored the role of long chain omega-3 essential fatty acids (EFAs) in maternal diets during pregnancy. These are the major fatty acids, docosahexaenoic acid (DHA) in particular, in brain and nervous tissue, with specific roles in neural development and cognitive function. Studies in monogastric species have shown that supplementing maternal gestation diets with EFAs positively influences neonatal survival and growth (Rooke et al., 2001), but work in ruminant species is scarce. Previous investigations have predominantly used fish oil as the source of omega-3 EFAs but alternative, more sustainable, sources are desirable. To date, the effect of period of inclusion of EFAs in gestation diets has not been thoroughly explored. The period of rapid brain growth in the ovine foetus occurs between 10 and 6 weeks prior to birth (Turley et al., 1996). This study explored the effects of feeding an algal source of EFAs, with a high content of DHA, during different time periods on measures of lamb viability.