Comparison of purebred and crossbred embryos through time lapse

Crossbred embryos have been reported to present higher and faster rates of development in vitro than purebred ones. The objective of the present study was to compare the development of purebred and crossbred embryos through the time lapse of their development. Material and methods: The embryos were produced in vitro from bovine slaughterhouse oocytes and frozen thawed semen. Purebred Embryos (PE) were produced from Holstein (H) and Montbeliard (M) oocytes inseminated with Holstein (H) or Montbeliard (M) semen (PE = HH and MM embryos). Crossbred Embryos (CE) were produced from Holstein (H) and Montbeliard (M) oocytes inseminated with Montbeliard (M) or Holstein (H) semen (CE = HM and MH embryos). Semen of 3 bulls of each breed were used. We performed four sessions of 32 embryos (8HH, 8MM, 8HM, 8MH) incubated individually in microwells placed under a microcamera (PrimovisionTM). Pictures were taken every 15 minutes until 192 h of development. The media and atmospheric conditions were previously described (Grimard et al., 2013). Development rates and the timing of reaching the 2, 4, 8 cells, morula and blastocyst stages were registered. Development rates of CE and PE groups were compared using the X2 test. Fixed effects of oocyte and semen breed and crossbreeding on embryo kinetic parameters were tested by multivariate analysis taking into account the random effect of IVF session. Results and conclusion: 128 embryos were produced. The 2 cells development rate was significantly lower in the CE than in the PE group. No differences were observed for 4, 8 cells, morula and blastocyst rates (78,1 vs 92,2% ; 67,2 vs 75% ; 53,1 vs 46,9% ; 45,3 vs 40,6% ; 31,3 vs 35,9%, CE vs PE, respectively, p>0,05). The timing of development was similar in both groups (p>0,05). On average, CE and PE groups reached 2, 4, 8 cells, morula and blastocyst stages at 31,8h +5,9 and 31,6h +6,0; 42,9h +6,7 and 43,2h +7,8; 63,9h +19,9 and 59,9h +18,6; 109,3h +10,4 and 108,4 +11,3;152,3h +17,7 and 150,6h +15,1; respectively. Under our conditions, crossbreeding had a negative effect on the development rate observed at the 2 cells stage but no significant effeossbreeding did not affect the timing of development observed during the time lapses.