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The male effect as an alternative to eCG in oestrus induction and synchronization treatment in ewes
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Edité par CCSD ; Wageningen Academic -
Session 79. Théâtre 8 : Improved insight into the reproductive physiology of livestock. International audience. We tested if the male effect (ME) can be an alternative to eCG in oestrus induction treatment used prior to artificialinsemination (AI) in ewes. Two groups of 50 Arles Merino (M) (2021) or Lacaune dairy (L) (2022) ewes weremonitored during anoestrus season: (1) FGA group: ewes were treated with intra-vaginal sponges impregnated withprogestagen for 14 days prior to ME; (2) C group: ewes received no hormonal treatment before ME. First, ME wasperformed for 14 days with 4 vasectomized rams equipped with the electronic oestrus detectors to monitor oestruskinetics and introduced with the ewes on the day of sponge removal (D0). Then, the ewes were mated with 4 entire ramsfor 17 days. Progesterone was measured before FGA treatment to determine the cyclic status of the ewes prior to MEand for 11 days from D0 to characterise the ovulatory response to ME. We observed a high percentage of cyclic ewesbefore ME (from 46 to 74%). Most cyclic and non-cyclic ewes ovulated after ME in FGA and C groups (respectively98 and 68% for M ewes; 98 and 63% for L ewes). The FGA treatment suppressed short cycles in response to ME (0vs 12% for M ewes; 0 vs 6,1% for L ewes, P<0.01). The percentage of ewes in oestrus from D0 to D14 was higherin the FGA group than in the C group (96 vs 44% for M ewes; 96 vs 68% for L ewes; P<0.001). The onset of oestrusafter D0 was earlier and better grouped in the FGA group (Median=34.34 h [Q1=31.08 h, Q3=43.25 h] for M ewes;42.16 h [33.73 h, 56.85 h] for L ewes) compared to the C group (137.83 h [71.61 h, 246.74] for M ewes; 147.14 h[51.02 h, 232.35 h] for L ewes) (P<0.001). Our previous results showed a higher fertility rate for ewes inseminatedbetween 0 and 35 h after the onset of oestrus . In the present study, 90% of M ewes and 68% of L ewes in the FGAgroup came into oestrus within a time window compatible with AI performed 53 h (M ewes) or 60 h (L ewes) aftersponge removal, compared to 4% (M) and 10% (L) in the C group (P<0.001). The combination of ME and FGA pretreatmentis an alternative method to the use of eCG in AI protocols with a unique and fixed timing of insemination.
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