Effect of pre-synchronisation with progestogen and eCG on reproductive activity in synchronised ewes during...

The objective of the study was to investigate the effect of pre-synchronisation on the occurrence of the oestrus and pregnancy rate after fixed time artificial insemination (FTAI) in synchronised ewes during the anoestrous season. Kivircik ewes (n = 84) were randomly assigned to one of the two treatment groups with (PRE; n = 42) or without (SYN; n = 42) pre-synchronisation. In the SYN group, the ewes were subjected to a 7-d short-term protocol (P4 insertion-6d-PGF2α-1d-P4 removal + eCG). In the PRE group, the same short-term protocol as in the SYN group was applied with 7 days apart for a pre-synchronised synchronisation protocol. A cervical FTAI was performed with fresh semen at 54 h after sponge removal. At the beginning of the synchronisation protocol, the oestrous response (66.7% vs. 0.0%) and cyclicity rates (64.3% vs. 14.3%) based on progesterone (P4) were higher in the PRE group compared to those in the SYN group, respectively (P < 0.01). However, the oestrous response after synchronisation was lower within 96 h (57.1% vs. 95.2%; P < 0.01) in the PRE group compared to that in the SYN group. Although the pregnancy rate after the FTAI was significantly (P < 0.05) lower in the PRE group (14.3%) than the SYN group (35.7%), the overall pregnancy rate after natural mating was not different (95.2%) between the groups. In conclusion, the pre-synchronisation decreased the oestrous response leading to a lower pregnancy rate after the FTAI in the synchronised ewes during the anoestrous season. Thus, attention should be paid to two consecutive administrations of eCG in a pre-synchronisation and synchronisation protocol in ewes.