Addition of insulin like growth factor-1 during maturation and culture enhances blastocyst rate and reduces apoptosis in bovine blastocysts derived from heat stressed oocytes

Heat stress (HS) reduces bovine oocyte developmental competence. Previous research showed that the addition of insulin like growth factor-1 (IGF-1) during maturation reduced apoptosis in heat stressed oocytes with no apparent effect on blastocyst rates. We hypothesized that adding IGF-1 during maturation and culture may enhance blastocyst rate and decrease apoptosis in blastocysts derived from heat stressed oocytes. During the first 12 h of maturation, HS (40.5C) was applied while IGF-1 (100 ng/ml) was added during maturation (M), during culture (C) or during both (MC). Two control groups were included (negative-control: no HS nor IGF-1 and HS-control: HS but no IGF-1). Blastocyst rates were 27.9 ± 2.1a, 10.9 ± 1.2b, 9.7 ± 1.2b, 18.4 ± 2.4c, and 15.3 ± 1.9bc % in negative-control, HS- ontrol, M, C and MC groups, respectively (a,b,c p < 0.05). Apoptotic cell ratios (ACR) were 9.7 ± 1a, 11.8 ± 1.2a, 11.6 ± 2a, 7.8 ± 0.8b and 5.9 ± 0.7c % in negative-control, HS-control, M, C and MC groups, respectively (a,b,c p < 0.05). The addition of IGF-1 to the culture medium increased blastocyst rate in comparison to HS-control group. However, IGF-1 had more beneficial effects on ACR when added during both maturation and culture than during maturation or culture only. In conclusion, negative effects of HS on oocyte developmental competence can be reduced by adding IGF-1 during both maturation and culture