Reproductive cycles in sheep

Bartlewski, Pawel M.; Baby, Tanya E.; Giffin, Jennifer L.

doi:10.1016/j.anireprosci.2011.02.024

Cited by 119 publications

(102 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Indeed, the melatonin concentration detected in this study was increased dramatically during the gestation period (the darkest period) and had started decreasing in kidding period and had reached the lowest concentration in the end of the lactation period. Data related to melatonin hormone observed in this study are in harmony with the findings obtained in sheep and goat breeds (Dicks, 1994;Gebbie et al, 1994;Malpaux et al, 1994;Gebbie et al, 1999;Fatet et al, 2011;Bartlewski et al, 2011).…”

Section: Discussionsupporting

confidence: 78%

Annual Change of Reproductive Hormones in Female Angora Goats

Pehlivan

Polat

Dellal

2017

Turkish JAF Sci.Tech.

View full text Add to dashboard Cite

In this research, annual changes of melatonin, gonadotropin-releasing hormone, follicle stimulating hormone, luteinizing hormone, estrogen, testosterone and progesterone were studied on 6 heads of 1.5 years old female Angora goat. To determine hormones concentrations, blood samples were taken from jugular vein of each goat in every month for a year. The blood samples were centrifuged at 4000xg for 5 min. and serum was stored at -20°C until analyses time. Hormones analyses in the serum were performed by enzyme immunoassay (EIA) method. Monthly climatic values and photoperiod were obtained from the Turkish State Meteorological Service and temperature-humidity index was calculated with climatic values. In the study, in order to determine any possible differences in the observed hormones concentrations with respect to months, repeated measures ANOVA analysis was performed. As a result of statistical analysis, there were no significant differences among the months for gonadotropin-releasing hormone, follicle stimulating hormone and testosterone concentration, while significant differences were found among the months for melatonin, luteinizing hormone and progesterone, and estrogen concentration in female Angora goats. According the results of this study, could be concluded that the releases of reproductive hormones examined in female Angora goats was seasonally dependent.

show abstract

Section: Discussionsupporting

confidence: 78%

Annual Change of Reproductive Hormones in Female Angora Goats

Pehlivan

Polat

Dellal

2017

Turkish JAF Sci.Tech.

View full text Add to dashboard Cite

show abstract

“…Ewes are seasonally polyestrous with an estrous cycle spanning approximately 17 days [40,41]. At the time of AI, ewes are in the estrus phase, which is characterized by surges of FSH and LH from the anterior pituitary gland.…”

Section: Structural Elements Of the Ovine Cervix At Various Reproductmentioning

confidence: 99%

A Review of Advances in Artificial Insemination (AI) and Embryo Transfer (ET) in Sheep, with the Special Reference to Hormonal Induction of Cervical Dilation and its Implications for Controlled Animal Reproduction and Surgical Techniques

Candappa¹,

Bartlewski²

2011

TORSJ

View full text Add to dashboard Cite

Artificial insemination (AI) and embryo transfer (ET) play an important role in the genetic improvement of sheep herds. This review primarily describes the methods that have recently been researched and/or adapted to circumvent the problematic anatomy of the ovine cervix, which prevents the widespread application of transcervical AI and ET in this species. A mechanism of cervical ripening at parturition and the endocrine influences on cervical tone are described as a backdrop to understanding the action of various pharmacological agents used to induce cervical dilation. Although several catheters have been designed to penetrate the ovine cervix, and a specific protocol has been developed for TCAI in sheep (Guelph Method), penetration rates and resulting pregnancy/lambing rates are still inconsistent and unpredictable. Hormonal dilation of the cervix may significantly improve the ease with which the ovine cervix can be traversed. Treatment with Cervidil ® , a dinoprostone-containing vaginal insert with a slow release mechanism, currently used to induce labor in women, could significantly improve cervical penetration in ewes without adverse effects on uterine contractility. This mode of drug delivery holds promise to result in the development of a safe method to induce cervical dilation for a broad range of transcervical reproductive manipulations in mammalian species including, but not limited to, AI, ET, embryo and oocyte recovery, treatment of ringwomb and transcervical surgical procedures. However, more studies are needed to evaluate the effects of hormonal methods on cervical morphology/pathomorphology, sperm/embryo transport and viability, and fertility in both cyclic and seasonally anovular ewes.

show abstract

“…The duration of ovarian folliculogenesis (period of follicular growth from the primordial to the preovulatory stage) takes approximately 175 days in women (Gougeon, 1986;Wallace & Kelsey, 2010) and 170 days in ewes (Cahill & Mauleon, 1980;Bartlewski et al, 2011). The primordial follicles, as well as the oocytes contained within, have similar diameters in both ewes and women, as depicted on Table 1.…”

Section: Comparison Of the Main Ovarian Features Between Women And Ewesmentioning

confidence: 76%

“…In response to the preovulatory gonadotropin surge occurring in each reproductive cycle, the Graafian follicle ovulates to release the mature oocyte ready to be potentially fertilized. However, throughout antral development, the majority of follicles undergo degeneration or atresia -the process responsible for the depletion of most of the ovarian follicles present in the ovary (Mcgee & Hsueh, 2000;Balasch et al, 2010;Bartlewski et al, 2011).…”

Section: Comparison Of the Main Ovarian Features Between Women And Ewesmentioning

confidence: 99%