Postpartum suppression of ovarian activity with a Deslorelin implant enhanced uterine involution in lactating dairy cows

Holstein cows received, subcutaneously a non-degradable implant containing 5 mg of the GnRH agonist Deslorelin (DESL) or no implant (CON) at 2 ± 1 days postpartum (dpp). All cows were injected with PGF2α at 9 dpp. Previous pregnant (PPH) and non-pregnant uterine horns (PNPH) were determined by palpation per rectum. In Experiment 1, cows [DESL implant (n = 10) and CON (n = 9)] were examined by ultrasonography to record ovarian structures (23, 30 and 37 dpp) and uterine horn and cervical diameters (16, 23, 30 and 37 dpp). Uterine tone was scored before ultrasonography. Vaginoscopy was conducted just after ultrasonography examination to assess cervical discharge and color of the external cervical os. Blood samples were collected on a weekly basis for hormonal analyses. In Experiment 2, cows [DESL implant (n = 77) and CON (n = 70)] were palpated per rectum and vaginoscopy at 30 dpp for scoring of uterine tone, uterine horns, cervical diameter, and discharge. Blood samples were collected only at 9 dpp. In Experiment 1, DESL-implant-treated cows had more Class 1 follicles (P < 0.01), less Class 2 (P < 0.01) and Class 3 follicles (P < 0.01) and no corpus luteum (CL) formation (P < 0.01). In CON cows, six of nine animals had visible CL at 25 ± 7 dpp. At 9 dpp plasma concentration of E2, P4 (P < 0.01) and PGFM (P < 0.05) were less in the DESL-implant treatment group. Diameter of PPH (P < 0.01), PNPH (P < 0.01) and cervix (P = 0.08) were less in the DESL-implant treatment associated with greater uterine tone (P = 0.07). The DESL-implant cows had a greater frequency of clear cervical discharge (P = 0.09) and pink cervical os (P = 0.06). In Experiment 2, plasma concentrations of PGFM were less at 9 dpp in DESL-implant treatment (P < 0.01). Diameters of the PPH (P < 0.01) and PNPH (P < 0.01) were less and more uterine tone (P < 0.01) in the DESL-implant treatment. Diameter of cervix and frequency of a cervical discharge score did not differ between treatments. Treatment with non-degradable Deslorelin (5 mg) implant during postpartum: (1) suppressed ovarian follicular development, (2) enhanced physical involution of the uterus and cervix, (3) increased tone of the uterine wall, (4) decreased frequency of purulent cervical discharges, and (5) reduced inflammatory processes of the reproductive tract.