276 research outputs found
The effect of the local administration of FSH and /or Misoprostol on cervical penetration in the ewe during the peri-ovulatory period
No full textThe expression of oxytocin receptor, c Phospholipase A2 and Cyclooxgenase 2 in the cervix of ewes during the oestrous cycle
No full textRegulation of folliculogenesis and the determination of ovulation rate in ruminants
No full textThe paper presents an update of our 1993 model of ovarian follicular development in ruminants, based on knowledge gained from the past 15 years of research. The model addresses the sequence of events from follicular formation in fetal life, through the successive waves of follicular growth and atresia, culminating with the emergence of ovulatory follicles during reproductive cycles. The original concept of five developmental classes of follicles, defined primarily by their responses to gonadotrophins, is retained: primordial, committed, gonadotrophin-responsive, gonadotrophin-dependent and ovulatory follicles. The updated model has more extensive integration of the morphological, molecular and cellular events during folliculogenesis with systemic events in the whole animal. It also incorporates knowledge on factors that influence oocyte quality and the critical roles of the oocyte in regulating follicular development and ovulation rate. The original hypothetical mechanisms determining ovulation rate are retained but with some refinements; the enhanced viability of gonadotrophin-dependent follicles and increases in the number of gonadotrophin-responsive follicles by increases in the throughput of follicles to this stage of growth. Finally, we reexamine how these two mechanisms, which are thought not to be mutually exclusive, appear to account for most of the known genetic and environmental effects on ovulation rate.R. J. Scaramuzzi, D. T. Baird, B. K. Campbell, M.-A. Driancourt, J. Dupont, J. E. Fortune, R. B. Gilchrist, G. B. Martin, K. P. McNatty, A. S. McNeilly, P. Monget, D. Monniaux, C. Viñoles and R. Web
Effect of infusion of glucose and hemi-ovariectomy on ovarian follicles and hormonal levels in sheep
No full textFollicular development and plasma concentrations of LH and prolactin in anestrus female dog treated with the dopamine agonist cabergoline.
No full textThe effect of a daily administration of a dopamine agonist (cabergoline, 5 μg/kg) for 4 weeks, starting about 95 days after the end of estrus on follicular development and its relationship with LH and prolactin secretion has been investigated in two groups of anestrous bitches (Beagles and Greyhounds). Pro-estrus was detected in 80% (8/10) of beagles and 50% (3/6) of treated greyhounds. The mean inter-estrus interval of treated animals was 132 ± 5.0 and 169 ± 7.0 days for beagles and greyhounds, respectively, and in both this differed significantly from the cycle preceding treatment (192 ± 9.0 and 198 ± 12.0 days) and from that in untreated bitches (194 ± 11.0 and 196 ± 11.0 days for beagles and greyhounds, respectively (all comparisons at P < 0.001). The interval from the beginning of treatment to pro-estrus in responding animals was 13.3 ± 1.90 days in beagles and 20.3 ± 1.70 days in greyhounds. Cabergoline increased (P < 0.001) the length of pro-estrus (10.6 ± 0.50 and 11.7 ± 0.50 days) in the treated estrus cycle compared to the previous estrus cycle (8.4 ± 0.30 and 8.8 ± 0.40 days for in beagles and greyhound, respectively). Ovarian enlargement and follicle development was detected by ultrasound in 90% of treated beagles and in 83% of greyhound between the second and third weeks of treatment, but only 80% of beagles and 66% of treated greyhound displayed pro-estrus and estrus. In the treated bitches, mean plasma LH increased (P < 0.001) before pro-estrus. There was high variability in mean plasma prolactin levels between animals. These data indicate that the administration of the dopamine agonist cabergoline to anestrous bitches increases mean LH plasma levels and induces follicular development shortly before pro-estrus but this activity is not always followed by pro-estrus and estrus. Finally, prolactin per se does not have a prominent role in the control of folliculogenesis in the bitch. © 2007 Elsevier Inc. All rights reserved
Causes of declining fertility in dairy cows during the warm season
No full textIn the Northern Hemisphere, from June to September and in the Southern Hemisphere from December to March, there are periods of reduced fertility (sub-fertility) in dairy cows that are described as summer infertility. Several factors contribute to sub-fertility during this time, such as ambient temperature, humidity and photoperiod. During the warm season there is a reduction in feed intake that may compromise the energy balance of the cow and/or induce an imbalance in the activity of the hypothalamo-hypophyseal-ovarian axis. These factors reduce the reproductive performance of the cow and compromise the quality of oocytes, embryos and corpora lutea. This paper reviews current knowledge on the metabolic and endocrine mechanisms that induce summer infertility and describe their effects on follicle, oocyte and embryo development in dairy cows
Fertility in post-partum dairy cows in winter or summer following estrus synchronization and fixed time A.I. after the induction of an LH surge with Gonadotropin releasing hormone (GnRH) or human chorionic gonadotropin (hCG)
No full textConception rate after fixed time insemination following ovsynch protocol with and without progesterone supplementation in cyclic and non-cyclic Mediterranean Italian buffaloes (Bubalus bubalis)
No full textThe aim of this study was to test the effect of progesterone supplementation to Ovsynch protocol in cyclic and non-cyclic Mediterranean Italian buffaloes on conception rate after fixed time artificial insemination. From 169 pluriparous buffaloes, 2 groups were identified and subjected to: (1) Ovsynch protocol (OV; n = 83) and (2) Ovsynch protocol with the supplementation of progesterone from days 0 to 7 (OV + PROG.; n = 86). All cows were inseminated 16-20 h after the second GnRH administration. Within each group, non-cyclic buffaloes were identified (OV = 21 and OV + PROG. = 20). Overall conception rate was significantly higher in cyclic compared to non-cyclic buffaloes: 43.7% versus 17.0%, respectively, P = 0.001. A significant effect of progesterone supplementation on conception rate was observed in non-cyclic buffaloes (30% versus 4.7%, P = 0.04) but not in cyclic buffaloes (51.5% versus 35.7%, P = 0.077). Collectively, the presence of a large follicle (≥10 mm) detected at the beginning of the Ovsynch protocol by ultrasound significantly affected conception rate (44% versus 8%, P = 0.01). The findings of the present study suggest that (i) progesterone supplementation to the Ovsynch protocol in buffaloes increases conception rate in non-cyclic animals, (ii) the presence of a large follicle at the beginning of the Ovsynch protocol is a determining factor for a successful synchronization of ovulation and high conception rates and (iii) ultrasound monitoring can improve the overall efficiency by selectively identifying more suitable cycling animals carrying a responsive follicle at the time of first GnRH administratio
Optically Inspired Nanomagnonics with Nonreciprocal Spin Waves in Synthetic Antiferromagnets
No full textIntegrated optically inspired wave-based processing is envisioned to outperform digital architectures in specific tasks, such as image processing and speech recognition. In this view, spin waves represent a promising route due to their nanoscale wavelength in the gigahertz frequency range and rich phenomenology. Here, a versatile, optically inspired platform using spin waves is realized, demonstrating the wavefront engineering, focusing, and robust interference of spin waves with nanoscale wavelength. In particular, magnonic nanoantennas based on tailored spin textures are used for launching spatially shaped coherent wavefronts, diffraction-limited spin-wave beams, and generating robust multi-beam interference patterns, which spatially extend for several times the spin-wave wavelength. Furthermore, it is shown that intriguing features, such as resilience to back reflection, naturally arise from the spin-wave nonreciprocity in synthetic antiferromagnets, preserving the high quality of the interference patterns from spurious counterpropagating modes. This work represents a fundamental step toward the realization of nanoscale optically inspired devices based on spin waves
Reproductive endocrinology of domestic ruminants /
No full textProceedings of a symposium held at Leura, New South Wales, Australia, February, 198
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