Response of rams to electroejaculation following the administration of oxytocin and cloprostenol with or without GnRH.

The present study aims to evaluate the effect of administering prostaglandin (250 µg cloprostenol) and oxytocin (10 UI) or a GnRH agonist (4.2 µg buserelin acetate) on rams' physiological responses to electroejaculation and the ejaculate's characteristics. The study was performed with a 2 × 2 factorial arrangement, according to whether it used oxytocin and prostaglandin (OXPGF) or GnRH. Therefore, there were four treatments: GControl = saline; GOXPGF = administration of PGF2α and oxytocin; GGnRH = administration of GnRH; administration of GOXPGF + GnRH = GnRH and PGF2α + oxytocin. An interaction between the hormonal treatments in the heart rate occurred: while the heart rate decreased when using OXPGF alone (control: 113.7 bpm vs. GOXPGF: 103.5 bpm, pooled SEM; P = 0.02), it did not modify when applying both treatments simultaneously and administering GnRH (GGnRH: 109.1 bpm vs. GOXPGF + GnRH: 111.5 bpm respectively, pooled SEM = 4.5). The respiratory rate also decreased with the administration of OXPGF (38.7 vs. 46.3 with and without OXPGF, pooled SEM = 10.0, P = 0.003). Administering OXPGF also tended to decrease the temperature (38.77 °C vs. 38.94 °C, with and without OXPGF, respectively, pooled SEM = 0.06; P = 0.056). Blood glucose increased with the administration of OXPGF from 58.7 mg/dL to 62.4 mg/dL (pooled SEM = 1.3, P = 0.014) and varied with time. CK concentrations increased from 641.8 mg/dL to 881.7 mg/dL (pooled SEM = 50.6) with the administration of OXPGF. GnRH administration decreased cortisol concentration from 7.3 ng/mL to 2.1 ng/mL (pooled SEM = 1.4; P = 0.04). The treatments had no effects on the time required for EE, the pulse at which the animals began and ended the ejaculation, or the vocalizations emitted during EE. There were no effects in any evaluated sperm variable. The research concluded that the administration of oxytocin and analogs of PGF2alpha decreased the stress response to electroejaculation, as well as administering GnRH agonist was slightly effective as it only decreased cortisol concentration. Also, these treatments, either alone or combined, did not affect the characteristics of the ejaculate collected.

Efficiency of different hormonal treatments for estrus synchronization in tropical Santa Inês sheep.

The aim of this study was to evaluate the effect of (i) the duration of hormone treatment with progestogen sponges during the seasonal anestrus and (ii) the administration of two doses of prostaglandin at 7 days apart during the breeding season on reproductive parameters of Santa Inês ewes. In experiment 1, 32 ewes received intravaginal MAP sponges for 6 (G6 days), 9 (G9 days), or 12 (G12days) days and 75 µg D-cloprostenol i.m. and 300 IU eCG i.m. 1 day before sponge removal. In experiment 2, 23 ewes received two doses of 0.48-mg sodium cloprostenol i.m. 7 days apart. Ovarian follicular dynamic was assessed through transrectal ultrasonography. Blood samples were collected daily to determine progesterone concentrations. In experiment 1, estrus and ovulation rates did not differ (P > 0.05) among protocols and between cyclic and acyclic ewes at the beginning of the experiment. The G9 days treatment showed a lower dispersion of ovulations in relation to onset of estrus when compared to G6 days and G12 days. In experiment 2, all ewes exhibit estrus and ovulated after the second dose of prostaglandin, although ewes that were in diestrus at D0 showed subluteal concentrations of progesterone during the follicle development stage of the treatment. In conclusion, the use of progestogen device during 9 days promotes lower dispersion of ovulation when compared to its use for 6 or 12 days, and the protocol of two doses of prostaglandin 7 days apart synchronizes estrus efficiently but results in follicular development under low progesterone concentrations.