Effect of post-mating TAK-683 (Kisspeptin analog) treatment on luteal morphology and function in suckling goats with lactational anestrus.

This study aimed to evaluate the effects of TAK-683 administered to suckling goats in lactational anestrus on the 4th day (D4) after mating on luteal function, serum progesterone (P₄) levels, and reproductive performance. Forty-five Aleppo goats were treated with intravaginal sponges containing medroxyprogesterone acetate for 7 days and were injected intramuscularly with 500 IU eCG and 75 µg d-cloprostenol on the day of sponge removal. Thirty-seven goats showed estrus and were mated with fertile bucks (D0). The mated goats were randomly divided into groups to receive subcutaneous administration of saline (Control, n = 12), 5 μg TAK-683 (TAK-5, n = 12) or 25 μg TAK-683 (TAK-25, n = 13) on D4. Transrectal ovarian ultrasonography and blood sampling were performed on D4, D7, D14, D17, and D21, and pregnancy was diagnosed on D35. Regardless of dose, TAK-683 treatment induced the formation of accessory corpora lutea (aCL) and significantly increased original CL (oCL) diameter, luteal area (LA), and Doppler area (DA) compared with controls (P < 0.001). Total LA and DA were greater (P < 0.001) in TAK-5 and TAK-25, although DA/LA ratio did not differ (P > 0.05). Serum P₄ levels were significantly higher in TAK-25 from D7 to D21 (P < 0.001), while TAK-5 showed a delayed increase from D17. Luteal morphological parameters were strongly and positively correlated with circulating P₄ levels, confirming the luteotropic effect of TAK-683. TAK-683 treatment had no significant effect on fertility parameters (P < 0.05). In conclusion, although TAK-683 treatment enhanced luteal function and increased circulating P₄ concentrations, it failed to improve fertility outcomes in suckling goats under lactational anestrus conditions.