The effect of oxytocin and oestradiol on the action of conceptus secretory protein in progesterone-treated ovariectomized ewes

Monitoring of embryonic and fetal losses in different breeds of goats using real-time B-mode ultrasonography

Compared to cattle and sheep, few studies had been undertaken to evaluate the incidence of embryonic and fetal losses (EFL) in goats. The objectives of the present study were to characterize the timing of EFL and to identify the factors that are associated with EFL in goats such as breed, age, parity, method of estrous synchronization, and breeding. Moreover, this study aimed to ensure whether a relationship existed between serum progesterone (P4) and EFL. Goats (n = 151) of different breeds (70 Zaraiebi, 42 Damascus, and 39 Cross goats [Baladi × Damascus]) were evaluated by ultrasonography to monitor EFL during different stages of gestation (D20-23, D26-29, D33-36, D40-45, and D47-54 after breeding). Blood samples were collected at D7, D20, and at each ultrasonographic scanning to clarify changes of serum P4 levels concurrently with EFL. Results revealed that 45 of 109 goats (41.28%) were exposed to EFL. A higher EFL % was observed between D20 to 23 and D47 to 54 (19.61%) compared with D47 to 54 to birth (11.76%). Moreover, a higher EFL % was observed in Zaraiebi goats compared with others. Age and goat parity had no significant effect on the EFL % in all goats. A high EFL % were observed in goats synchronized by P4 sponge, as well as artificially inseminated goats compared with goats with spontaneous estrus, and bred by natural mating, respectively. Serum P4 at D7 or D20 after breeding showed nonsignificant difference between normal pregnant goats and goats that experienced EFL. Unlike goats that experienced partial EFL, goats that experienced total EFL between D20 to 23 and D26 to 29 showed an abrupt P4 reduction (85.06%; P < 0.01) suggesting the probability of endocrine disruption of the CL. However, goats that were exposed to total EFL between D26 and 29 to D33 to 36 showed a low P4 reduction (24.90%; P < 0.05), which might be considered as an effect rather than a cause of EFL. In conclusion, different factors such as breed, estrous synchronization, breeding, and stage of pregnancy may be involved in EFL in goats. Therefore, improvement of the goat management in the early stage of pregnancy is important to decrease EFL % in goats. Although the P4 did not show any significant difference between normal pregnancy goats and goats that experienced EFL, CL disruption should be taken into the consideration, at least, in goats exposed to total embryonic losses.

Embryonic mortality in buffaloes synchronized and mated by AI during the seasonal decline in reproductive function

The aim was to determine the factors that contribute to embryonic mortality in buffaloes mated by AI during a period of increasing day length which corresponds to a natural decline in reproductive activity. Italian Mediterranean buffalo cows (n=243) showing regular estrous cycles were synchronized using the Ovsynch-TAI program and mated by AI at 16 and 40 h after the second injection of GnRH. Blood samples were collected on Days 10 and 20 after the first AI and assayed for progesterone (P4). Pregnancy diagnosis was undertaken on Days 26 and 40 after the first AI using rectal ultrasonography. Buffaloes with a conceptus on Day 26 but not on Day 40 were judged to have undergone embryonic mortality and for these animals uterine fluid was recovered by flushing and analysed for common infectious agents. Estrus synchronization was achieved in 86% of buffaloes and the pregnancy rate on Day 40 was 34%. Embryonic mortality between Days 26 and 40 occurred in 45% of buffaloes and was associated with the presence of significant infectious agents in only 10 buffaloes (8%). Concentrations of P4 on Day 10 after AI were higher (P<0.05) in buffaloes that established a pregnancy than in buffaloes that showed embryonic mortality that was not associated with infectious agents. Similarly, on Day 20 after AI P4 concentrations were higher (P<0.01) in pregnant buffaloes compared with non-pregnant buffaloes and buffaloes that had embryonic mortality. It is concluded that a reduced capacity for P4 secretion can explain around 50% of embryonic mortalities in buffaloes synchronised and mated by AI during a period of low reproductive activity and that other as yet unidentified factors also have a significant effect on embryonic survival.

The role of luteal oxytocin in episodic secretion of prostaglandin F2alpha at luteolysis in the ewe

The role of luteal oxytocin in the generation of luteolytic episodes of prostaglandin F2alpha at luteolysis was investigated. On day 10 of the cycle Dorset ewes underwent either surgical removal of the corpora lutea (lutectomy; n = 4) or sham operation (sham; n = 4). Lutectomised ewes were then administered progesterone by twice daily i.m. injection in corn oil (20 mg/day) until day 14 when treatment was ceased to simulate luteolysis. The concentration of 13, 14 dihydro-15-keto prostaglandin F2alpha (PGFM) was measured in peripheral blood samples collected at 20-min intervals for 8 h on days 12-16 of the cycle. Progesterone and oestradiol concentrations were similar in the two groups over the whole experimental cycle while oxytocin fell dramatically following lutectomy. No prostaglandin F2alpha release episodes were seen on day 12 or 13, while from days 14-16 both groups exhibited a similar episode frequency (lutectomy 0.9/ewe/8 h; sham 0.8/ewe/8 h). Analysis of episode characteristics revealed lower episode amplitude (p<0.05) but longer episode duration (p<0.05) in the lutectomy group. The results demonstrate that a normal frequency of prostaglandin F2alpha release episodes occurs independently of luteal oxytocin secretion. However, luteal oxytocin is involved in regulating the pattern of release, perhaps causing the release of episodes of the magnitude required for the successful completion of luteolysis.