Effect of chronic treatment with bromocryptine on the corpus luteum function of the cow

Six heifers received an intramuscular injection of 15 mg bromocryptine twice daily from day 1 (the day of standing oestrus was defined as day 0) until 50 h after the start of luteal regression. The overall mean level of prolactin was 0.22 ±0.01 μg/l (SEM; N=6) in the bromocryptine-treated group and 10.7±2.7 μg/1 (SEM; N=6) in the control group. No significant differences in the overall mean level of progesterone and LH, the mean length of the early-luteal phase, the luteal phase and the period of luteal regression were measured between the two groups. The results provide strong evidence that prolactin has no luteotrophic properties in the cow during the oestrous cycle

Superovulation of cows with PMSG: Variation in plasma concentrations of progesterone, oestradiol, LH, cortisol, prolactin and PMSG and in number of preovulatory follicles

Forty-two heifers, exhibiting normal oestrous cycles, were treated with 2500 I.U. PMSG and 2 ml prostaglandin (PG) at day 10 and 12 of the oestrous cycle, respectively. In ten heifers progesterone, oestradiol, LH, prolactin, cortisol and PMSG levels were estimated until 10 days after the initiation of superovulation. In 32 heifers the occurrence of the LH surge was determined with a rapid radioimmunoassay, and 22–30 h after the LH surge the heifers were ovariectomized. The numbers of large follicles (> 10 mm) and ovulations on the collected ovaries were counted and the levels of progesterone, oestradiol, PMSG and LH in the peripheral blood where estimated. The sum of large follicles and ovulations was assumed to represent the number of preovulatory follicles. In 16.7% of the heifers no LH surge was detected. This failure of the LH surge after superovulation appeared not to be caused by significantly different levels of cortisol, prolactin and PMSG as compared to those of cows responding with an LH surge. There was quite some variability in the interval between the PG injection and the maximum of the LH surge. The mean interval was 43.9 ± 1.5 h (SEM; n = 28). This interval PG-LH was negatively correlated with the number of preovulatory follicles (r= −0.483; P < 0.01). The interval between the onset of oestrus and the maximum of the LH surge was 1.96 ± 0.54 h (n = 22). The oestradiol concentration during the preovulatory LH surge and the number of preovulatory follicles were positively correlated (r= 0.732; P < 0.01). Progesterone levels were significantly increased after the initiation of superovulation. There was no significant correlation between the progesterone level before or after the administration of PMSG and the number of preovulatory follicles. This number was also not correlated with the concentration of PMSG in the peripheral blood shortly after injection of PMSG or shortly after injection of PG. The results indicate that the marked variability in response to PMSG/PG superovulation is not due to variations of hormone concentrations during the stages of preovulatory follicular development

Environment of oocyte and embryo determines heath of IVP offspring

In vitro embryo production (IVP) enhances the number of offspring from a single female and offers the possibility of accelerated genetic progress in animal husbandry. However, it also leads to a low but unacceptable percentage of anomalies in the offspring. The aim of this paper is to introduce the three speakers at this afternoon session who will speak about the demands of culture conditions and the endometrial environment to support normal embryonic development without effects on the embryonic genome. It will be argued that the in vitro conditions should mimic precisely the oviductal contributions to homeostatic mechanisms within the embryo. The further normal development can be guaranteed at synchrony in development of both endometrium and embryo. If that is not the case one can expect disturbances of gene expression, in particular of imprinted genes. However, it cannot be excluded that some processes might have started already in the cytoplasm of the oocyte. Since the oocyte was not planned to be a separate subject in this symposium, this introduction is also aimed to ask attention for the selection of cumulus-oocyte-complexes (COCs) and the conditions around oocyte maturation in vitro. The optimal quality of both the oocyte and maturation medium are prerequisites for an undisturbed cytoplasmic maturation. It has been argued that the exclusion of COCs from atretic follicles, the abjuration of the use of serum and high O2 tension in the gas phase might help to reduce the proportion anomalies in the offspring after synchronous transfers. In human IVF, in vivo matured oocytes are used with no great problems. But before IVP, including oocyte maturation in vitro (IVM) and a longer lasting embryo culture (IVC), will be introduced into the human assisted reproduction, it is important to think about the ins and outs of the potential causes for deviations