A study on ghrelin and LH secretion after short fasting and on ghrelin levels at perioestrual period in dairy cattle

In two experiments, we studied (a) the changes of LH secretion in heifers under different feeding schedules and (b) total ghrelin concentration at oestrus in cows and heifers. In experiment one, synchronized heifers were allocated in three groups (R, regularly fed controls; F, fasted; and F-F fasted-fed). One day after the completion of the oestrous induction protocol, group F and F-F animals stayed without feed for 24 hr; thereafter, feed was provided to R and F-F cattle; 2 hr later, GnRH was administered to all animals. Blood samples were collected for ghrelin, progesterone, LH and cortisol concentrations. Fasting caused increased ghrelin concentrations in groups F and F-F, while in response to GnRH, LH surge was significantly attenuated in groups F and F-F compared to R. In experiment 2, lactating cows and heifers were used. On day 9 of a synchronized cycle, PGF2α was administered, and blood samples were collected twice daily until the third day after oestrus and analysed for progesterone, estradiol, ghrelin, glucose and BHBA concentrations. No difference was recorded between groups in steroids and BHBA concentrations. In comparison to mid-luteal values, ghrelin concentrations significantly increased at perioestrual period in cows, but not in heifers. This study provides evidence that starving-induced elevated ghrelin concentrations can have suppressing effect on LH secretion, even after ghrelin's restoration to basal values and that during oestrus, ghrelin secretion is differently regulated in cows and heifers, likely being independent from oestradiol concentrations. Further research is required to identify the determining factors that drive the different regulation of ghrelin secretion in cows and heifers. © 2018 Blackwell Verlag Gmb

Plasminogen activator activity and plasminogen activator inhibition in the uterus of ewes after the induction of oestrus synchronization or superovulation, involving eCG

During the preimplantation period, early mammalian embryos largely depend on uterine environment. Concurrently, uterine architecture undergoes substantial growth and remodeling under the influence of ovarian steroids. Plasminogen activators/plasmin proteolytic system that is implicated in tissue remodeling is affected by reproductive hormone variations. Thus, hormone treatments for reproductive function control possibly influence proteolytic enzyme activity in the reproductive tract and its study in uterine fluid and endometrium could demonstrate possible changes in uterine environment. This work examines (a) the effect of hormone treatment involving eCG in the dosage used for oestrus synchronization or for superovulation on plasminogen activator activity (PAA) and plasminogen activator inhibition (PAI) in the uterus of ewes before maternal recognition of pregnancy and (b) the possible relationships among blood ovarian steroid concentration, proteolytic enzyme activity and ovarian response/embryo yield. Chios ewes (n = 24) were treated with progestagen intravaginal sponges for 12 days and eCG (500 or 1000 IU) at sponge removal; ewes at the second oestrus after synchronization were used as controls. On day 6 of the oestrous cycle, after slaughter, ovarian response was assessed and embryos were collected; uterine horn flushings (UHF), caruncular endometrium (CE) and intercaruncular (ICE) endometrium samples were collected, for PAA and PAI photometrical assessment. Oestradiol-17β (E2) and progesterone (P4) concentration was assessed in blood serum samples collected before slaughter by a radioimmunoassay. A significant increase of PAA in the UHF was observed after treatment; PAA in UHF was significantly associated with the number of embryos or high-quality embryos, while PAA in UHF per embryo or high-quality embryo was not affected by treatment. No significant effect of treatment was noticed on PAA or PAI in the endometrium (CE, ICE). In UHF and in ICE, PAI against tissue-type PA had a significant positive relationship with PAI against urokinase-type PA. PAI against tissue-type PA in CE had significant negative relationship with E2 concentration. In conclusion, hormone treatment involving eCG in the dosage used for superovulation and, to a lesser degree, in the dosage used for oestrus synchronization affected PAA in the uterus of Chios ewes, before maternal recognition of pregnancy, but did not seem to disturb reproductive function. © 2022 Elsevier B.V

Effect of equine chorionic gonadotropin on glycosidase activity in the reproductive tract of ewes, in relation to ovarian response and embryo yield

The aim of this study was to investigate a) the effect of equine Chorionic Gonadotropin (eCG), in the dosage used for oestrus synchronization or for superovulation, on the activity of α-mannosidase (α-MAN) and β-N-acetyloglucosaminidase (β-NAGASE) in the genital tract of ewes before maternal recognition of pregnancy and b) the possible relationships among ovarian steroids concentration, glycosidase activity and embryo yield and quality. Twenty-four Chios ewes were treated with progestagen intravaginal sponges for 12 days and eCG [superovulation (SOV), n = 7, 1000 IU; oestrus synchronization (OS), n = 7, 500 IU; controls (C), n = 10, 0 IU] at sponge removal. Ovarian response was assessed and embryos were collected on day 6 of the oestrous cycle, after slaughter. Oestradiol-17β and progesterone concentrations were determined in blood serum samples collected before slaughter using a radioimmunoassay. The activities of α-MAN and β-NAGASE were assayed, photometrically, in uterine horn flushing (UHF) samples, caruncular endometrium (CE) and intercaruncular (ICE) endometrium samples, collected after slaughter. Alpha-MAN activity was higher in the UHF, CE and ICE of SOV ewes, as well as in the UHF and ICE of OS ewes, compared to controls. Beta-NAGASE activity in the UHF and in the ICE of SOV ewes was lower than in C ewes. Alpha-MAN activity in the UHF was positively correlated with the response to superovulation in terms of total recovered structures, embryos or high-quality embryos collected from the ewes. Beta-NAGASE activity in the CE correlated to the number of corpora lutea observed on the ovaries, at the day of embryo collection. Beta-NAGASE activity in UHF and α-MAN activity in the ICE were negatively related to oestradiol-17β concentration in blood serum; β-NAGASE activity in UHF and in ICE was negatively related to progesterone concentration in blood serum. In conclusion, eCG in the dosage used for superovulation and, in a lesser degree, in the dosage used for oestrus synchronization affects glycosidase activity in the genital tract of Chios breed ewes, before maternal recognition of pregnancy; glycosidase activity in the genital tract correlate to ovarian response and embryo yield. Further research is necessary to fully clarify the interrelationship between ovarian steroids concentration and glycosidase activity in the genital tract of ewes after hormonal treatment. © 2020 Elsevier B.V