scholarly journals Follicular growth patterns in repeat breeder cows

2012 ◽  
Vol 48 (No. 1 - 2) ◽  
pp. 1-8
Author(s):  
Pérez CC ◽  
I. Rodríguez ◽  
F. Espańa ◽  
J. Dorado ◽  
M. Hidalgo ◽  
...  
Keyword(s):  
Artificial Insemination ◽  
Follicular Development ◽  
Growth Patterns ◽  
Follicular Growth ◽  
Development Patterns ◽  
Follicular Waves ◽  
Repeat Breeder

The aim of this study was to examine follicular development patterns in eighteen repeat breeder cows through natural oestrus cycles. Ovarian ultrasonographic examinations over 32 days after artificial insemination revealed that two follicular waves were the predominant patterns in animals with this syndrome (72.2%). Cycles with one or four waves rarely appeared. The ovulatory follicular diameter (day 0) was larger (P < 0.01) in cycles with a small number of waves; no differences were detected between ovulatory and anovulatory dominant follicles. Progesterone plasmatic concentrations were determined by RIA and differences were not significant when cycles with two or three waves were compared. The number of follicular waves was higher (2 or 3 waves) with longer interovulatory intervals (22.3 ± 1.89 vs 23.0 ± 2.0; n.s.) and older cows (7.0 ± 2.64 vs. 4.38 ± 1.66 years; P < 0.05). Mean ovulatory follicular diameter was 1.78 ± 0.36 cm. It can be concluded that cows with the RBC syndrome more frequently present two follicular waves, corresponding to longer cycles.  

1 PROGESTERONE AS THE DRIVING REGULATORY FORCE BEHIND SERUM FSH CONCENTRATIONS AND ANTRAL FOLLICULAR GROWTH IN CYCLIC EWES

2010 ◽  
Vol 22 (1) ◽  
pp. 159
Author(s):  
T. E. Baby ◽  
P. M. Bartlewski
Keyword(s):  
Treatment Group ◽  
Estrous Cycle ◽  
Luteal Phase ◽  
Follicular Development ◽  
Serum Levels ◽  
Time Frame ◽  
Corpora Lutea ◽  
Research Station ◽  
Follicular Growth ◽  
Follicular Waves

Ovarian antral follicles in sheep grow in an orderly succession, producing typically 3 to 4 follicular waves per 17-day estrous cycle. Each wave is preceded by a transient increase in circulating FSH concentrations. The mechanism controlling the number of recurrent FSH peaks and emerging follicular waves remains unknown. During the ewe's estrous cycle, the time between the first 2 FSH peaks and days of wave emergence is longer than the intervals separating the ensuing FSH peaks and follicular waves. The prolonged inter-peak/inter-wave interval occurs early in the luteal phase when low levels of progesterone are secreted by developing, or non-fully functional, corpora lutea. The purpose of the present study was to determine the effect of varying progesterone (P4) levels on circulating concentrations of FSH and antral follicular development in sheep. Exogenous P4 (15 mg per ewe i.m.) was administered twice daily to 6 cycling Rideau Arcott × Dorset ewes from Day 0 (ovulation) to Day 4 (the mean duration of the inter-wave interval); 6 animals served as controls. Follicular growth was monitored in all animals by daily transrectal ultrasonography (Days 0 to 9). Jugular blood samples were drawn twice a day from Day 0 to 4 and then daily until Day 9 to measure systemic concentrations of P4 and FSH. The first FSH peak post-ovulation was detected on Day 1.4 ± 0.2 and 4.0 ± 0.2 in treated and control ewes, respectively (P < 0.05). The next FSH peak(s) occurred on Days 3.4 ± 0.3 and 5.2 ± 0.2 in the treatment group and on Day 5.5 ± 0.3 in controls. Consequently, the treatment group had, on average, 3 follicular waves emerging on Days 0, 3, and 6, whereas the controls produced 2 waves emerging on Days 0 and 5 (P < 0.05).We then retrospectively analyzed and compared daily serum concentrations of P4 and FSH obtained in cyclic Western White Face ewes (Columbia × Rambouillet) that had 3 (n = 10) or 4 (n = 19) follicular waves per cycle. Mean P4 concentrations were greater (P < 0.05) in sheep with 4 waves per cycle compared with their counterparts, which had 3 waves of follicular growth. Interestingly, the ewes with 3 waves exceeded (P < 0.05) all animals with 4 follicular waves in mean serum FSH concentrations on Days 0 to 2, 6 to 7, and 9 to 15 post-ovulation. In summary, creation of mid-luteal phase levels of P4 in metestrus shortened the time to the first post-ovulatory FSH peak in ewes, resulting in emergence of one more follicular wave compared with control animals during the same time frame. The ewes exhibiting 4 waves of follicular emergence had greater serum levels of P4 but lower FSH concentrations compared with sheep with 3 waves per cycle. Therefore, progesterone appears to be a key endocrine signal governing the control of periodic increases in serum FSH concentrations and the number of follicular waves in cyclic sheep. This study was funded by OMAFRA and NSERC grants. Appreciation is extended to Norman C. Rawlings, Susan Cook, and Sekallu Srinivas (University of Saskatchewan) and the staff at Ponsonby Sheep Research Station.

Follicular waves are associated with transient fluctuations in FSH but not oestradiol or inhibin-A concentrations in anoestrous ewes

2001 ◽  
Vol 72 (3) ◽  
pp. 547-554 ◽  
Author(s):  
A.C.O. Evans ◽  
P. Duffy ◽  
K. M. Quinn ◽  
P. G. Knight ◽  
M. P. Boland
Keyword(s):  
Breeding Season ◽  
Follicular Fluid ◽  
Follicular Development ◽  
Transrectal Ultrasonography ◽  
Ultrasound Scanning ◽  
Follicular Growth ◽  
Inhibin A ◽  
Blood Samples ◽  
Follicular Waves

AbstractThe aim was to examine statistically the changes among days in the numbers of follicles relative to the growth of large follicles to test the hypothesis that follicular development occurs in a wave-like fashion in anoestrous ewes. The relationships among the patterns of circulating concentrations of FSH, oestradiol and inhibin-A and the pattern of follicular growth as well as relationships among follicular fluid steroid and inhibin-A concentrations were also studied. The ovaries of 11 ewes were examined daily using transrectal ultrasonography for 14 days and blood samples were collected every 8 h for 9 days. Five ewes were ovariectomized on the last day of ultrasound scanning. One to three identified follicles (a cohort) emerged every 2 to 5 days (mean 2·9 (s.e. 0·2) days) in individual ewes. The numbers of 4 and 5 mm follicles were fewest (P < 0·05) before and greatest (P < 0·05) 1 day after cohort emergence. This change in the numbers of follicles indicates a wave-like pattern of follicular growth. FSH concentrations were greatest (P < 0·05) on the day before wave emergence and lowest (P < 0·05) on the day of wave emergence. Peripheral concentrations of oestradiol and inhibin-A did not fluctuate (P > 0·05) in association with the emergence of follicular waves. The follicles that were collected at ovariectomy originated from one of three different waves. Oestradiol and inhibin-A concentrations in follicular fluid and the oestradiol-to-progesterone ratio were not different among the largest follicles of successive waves, when follicles were collected at the same time, indicating that new waves of follicles developed before the demise of old waves.In conclusion, waves of follicles emerged about every 3 days in anoestrous ewes (defined as significant changes in numbers of follicles) and were associated with fluctuations in FSH concentrations but not peripheral oestradiol or inhibin-A concentrations. New follicular waves also emerged in the presence of steroidogenically active (positive oestradiol-to-progesterone ratio), inhibin-A producing follicles from a previous wave suggesting that follicles do not exert functional dominance during the non-breeding season.

Pituitary and ovarian response to transient doe-litter separation in nursing rabbits

Reproduction ◽  
2000 ◽  
pp. 361-366 ◽  
Author(s):  
E Ubilla ◽  
PG Rebollar ◽  
D Pazo ◽  
AI Esquifino ◽  
JM Alvarino
Keyword(s):  
Pituitary Gland ◽  
Litter Size ◽  
Artificial Insemination ◽  
Ovarian Response ◽  
Major Effect ◽  
Free Access ◽  
Plasma Prolactin ◽  
Follicular Waves ◽  
Higher Sensitivity

The effects of a transient doe-litter separation on plasma prolactin, FSH and oestradiol concentrations, as well as the effect on LH response to exogenous GnRH administered at the time of artificial insemination, were determined in nursing rabbits. The effects on fertility, and litter size after parturition, as well as litter survival after doe-litter separation, were also studied. Control does (n = 12) had free access to nursing, whereas biostimulated does (n = 12) were separated from their litters for 48 h before artificial insemination. Plasma prolactin concentrations were decreased 24 h after the doe-litter separation (P < 0.05). The response of prolactin to suckling reached 10 times the basal values measured on day 10 after parturition (P < 0.0001). Increased oestradiol concentrations were found during the 48 h after the doe-litter separation: at 0 h, before artificial insemination (P< 0. 0001), 1.0-2.0 h after artificial insemination (P < 0.001), at 2.5 h (P < 0.05), 3.0 h (P < 0.01), and at 3.5 h (P < 0.05) after artificial insemination. Exogenous GnRH administered at the time of artificial insemination caused a greater LH response in does previously separated from their litters during 48 h (P < 0.01). The transient doe-litter separation did not affect plasma FSH concentrations, fertility, litter size or litter survival. These results suggest that a transient separation of nursing does from their litters before artificial insemination results in a decrease in plasma prolactin concentrations that could promote growth of follicular waves, and high steroidogenesis activity, leading to increased oestradiol concentrations and inducing higher sensitivity of the pituitary gland to exogenous GnRH. These findings associated to the absence of suckling episodes would lead to higher LH response and, therefore, exert a major effect on fertility.

scholarly journals Endometrial Inflammation at the Time of Insemination and Its Effect on Subsequent Fertility of Dairy Cows

Animals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1858
Author(s):  
Karen Wagener ◽  
Marc Drillich ◽  
Christine Aurich ◽  
Christoph Gabler
Keyword(s):  
Immune Response ◽  
Dairy Cows ◽  
Mrna Expression ◽  
Reverse Transcription ◽  
Artificial Insemination ◽  
Cox Regression ◽  
Related Factor ◽  
Subsequent Fertility ◽  
Cxcl8 Mrna ◽  
Repeat Breeder

Our objective was to investigate the level of endometrial immune response at artificial insemination (AI) and to relate it to subsequent fertility. From 71 healthy cows, endometrial cytobrush samples were taken at the first AI for cytological and mRNA analyses. Total RNA isolated from the cytobrushes was used for reverse transcription qPCR for selected transcripts. Animals were grouped into pregnant (PREG; n = 32) and non-pregnant (non-PREG; n = 39) cows following their first AI. The mRNA abundance of the neutrophil-related factor CEACAM1 and the chemokine CXCL5 was 1.2- (p = 0.03) and 2.0-fold (p = 0.04) greater in PREG than in non-PREG cows, respectively. Animals were further subdivided according to the number of inseminations until pregnancy (PREG1, n = 32; PREG2-3, n = 19) and in repeat breeder cows (RBC, n = 13). CEACAM1 and CXCL8 mRNA expression was 1.7- (p = 0.01) and 2.3-fold (p = 0.03) greater in PREG1 than in RBC, respectively. Cox regression showed that cows with PMN ≥ 1% had a 1.8-fold increased chance of pregnancy within 150 days postpartum compared with cows with fewer PMNs. We conclude that a certain level of inflammation before the stimulus of AI might be beneficial for subsequent fertility.

scholarly journals Effect of progesterone, human chorionic gonadotropin and progesterone + human chorionic gonadotropin treatment on conception rates in repeat breeder cows

2020 ◽  
Vol 89 (4) ◽  
pp. 307-315
Author(s):  
Hasan Alkan ◽  
Huseyin Erdem
Keyword(s):  
Pregnancy Rate ◽  
Chorionic Gonadotropin ◽  
Human Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Group 4 ◽  
Prostaglandin F ◽  
Repeat Breeder ◽  
Group 1

The aim of this study was to investigate the effects of hormonal support on the pregnancy rate in repeat breeder cows. Prostaglandin F2α + Ovsynch oestrus synchronization protocol was applied to the cows. Following the fixed time insemination (day 0), the cows were divided into 4 groups. In Group 1 (n = 42), progesterone releasing intravaginal device (PRID) was placed vaginally at 84 h and removed on the 9th day after the artificial insemination. In Group 2 (n = 40), the cows were administered human chorionic gonadotropin (hCG) on the 7th day. Group 3 (n = 45) was applied a combination of progesterone and hCG. Group 4 (n = 42) was not given any treatment. Blood samples were collected from all cows 4 times on days 3.5, 7, 12, and 18 to evaluate progesterone concentrations. The pregnancy rates were 40.47%, 37.50%, 44.44%, and 30.95% in Group 1, 2, 3, and 4, respectively (P > 0.05). In addition, in cows with progesterone concentrations <2 ng/ml on day 3.5, the pregnancy rates were found to be lower than in the cows with progesterone concentrations >2 ng/ml in Group 4 (P < 0.05). Progesterone supplementation in cows with progesterone concentrations < 2 ng/ml appeared to increase pregnancy rates (P < 0.05) in Groups 1 and 3. As a result, post-insemination hormonal applications in the repeat breeder cows did not increase the pregnancy rate. However, it was concluded that determination of progesterone concentrations on day 3.5 following artificial insemination and then hormonal support in the cows with low concentrations would increased the pregnancy rate.

scholarly journals The Role of Androgens in Mammals Folliculogenesis

2018 ◽  
Vol 44 (1) ◽  
pp. 15
Author(s):  
Livia Brunetti Apolloni ◽  
Jamily Bezerra Bruno ◽  
Benner Geraldo Alves ◽  
José Ricardo de Figueiredo
Keyword(s):  
Androgen Receptor ◽  
In Vitro Culture ◽  
Steroid Hormones ◽  
Oocyte Maturation ◽  
Follicular Development ◽  
Follicular Growth ◽  
Preantral Follicles ◽  
Ovarian Cells

Introduction: Steroid hormones production is a physiological process termed steroidogenesis. An important stage of this process is the conversion of androgens into estrogens through aromatase enzyme. Furthermore, androgens are important in the process of folliculogenesis, promoting follicular growth in different species. Thus, the aim of this review was to present the process of synthesis, mechanism of action, and importance of androgens in folliculogenesis. Additionally, the main results of in vitro culture of ovarian cells in the presence of these hormones were emphasized.Review: Folliculogenesis begins in prenatal life in most of species and can be defined as the process of formation, follicular growth, and oocyte maturation. Preantral follicles represent 95% of the follicular population and assisted reproductive technologies have been developed (e.g., Manipulation of Oocytes Enclosed in Preantral Follicles - MOEPF) in order to avoid the great follicle loss that occurs naturally in vivo by atresia. The MOEPF aim to obtain a large number of competent oocytes from preantral follicles and then subject to in vitro maturation, fertilization, and culture for embryo production. However, the development of an efficient medium to ensure the follicular survival and oocyte maturation is the major challenge of this biotechnology. To achieve the success on in vitro culture, the effects of substances as androgens on follicular development have been evaluated. Androgens are steroid hormones produced in theca cells (TC) that are fundamental for follicular growth. These cells provide all the androgens required by the developing follicles for conversion into estrogens by the granulosa cells (GC). Androgens receptors (AR) are localized in cell cytoplasm of all follicular categories, being more expressed in preantral follicles. The androgen pathway initiates through its connection to its receptor, making a complex androgen-AR, that in the nucleus helps on the process of gene transcription related with follicular survival. This mechanism is androgen receptor genomic activity. In addition to genomic action, there is an androgen receptor non-genomic activity. This occurs through activation of AR and its interaction with different signaling molecules located on the cell membrane, triggering events that aid in the follicular development. Regardless of the androgens actions, ovarian cells of several species subjected to in vitro culture have shown the importance of these hormones on the follicle development. Recent studies demonstrated that androgens addition on the culture medium stimulated the activation of preantral follicles (bovine and caprine), antrum formation (swine), survival (non-primate), and oocyte maturation (antral follicles; bovine). Also, some studies suggest that the addition of these hormones on in vitro culture is dose-dependent and species-specific.Conclusion: This review shows the role of androgens in different stages of follicular development and its action as a substrate for steroidogenesis and transcription of genes related to follicular survival and oocyte maturation. However, when these hormones should be added during in vitro follicular culture and which concentration is required remains unclear, being necessary more studies to elucidate these aspects.

Factors affecting folliculogenesis in ruminants

1999 ◽  
Vol 68 (2) ◽  
pp. 257-284 ◽  
Author(s):  
R. Webb ◽  
R. G. Gosden ◽  
E. E. Telfer ◽  
R. M. Moor
Keyword(s):  
New Technologies ◽  
Ovarian Function ◽  
Major Gene ◽  
Follicular Development ◽  
Oocyte Quality ◽  
Ovulation Rate ◽  
Follicular Growth ◽  
Stages Of Development ◽  
Hormone Production ◽  
Factors Affecting

AbstractThis review addresses the reasons for the lack of progress in the control of superovulation and highlights the importance of understanding the mechanisms underlying follicular development. The present inability to provide large numbers of viable embryos from selected females still restricts genetic improvement, whilst variability in ovarian response to hormones limit the present capacity for increasing reproductive efficiency.Females are born with a large store of eggs which rapidly declines as puberty approaches. If these oocytes are normal then there is scope for increasing the reproductive potential of selected females. Oocytes must reach a certain size before they can complete all stages of development and the final changes that occur late in follicular development. It is likely that oocytes that do not produce specific factors at precise stages of development will not be viable. Hence, it is important to characterize oocyte secreted factors since there are potential indicators of oocyte quality.The mechanisms that determine ovulation rate have still not been fully elucidated. Indeed follicular atresia, the process whereby follicles regress, is still not known. A better understanding of these processes should prove pivotal for the synchronization of follicular growth, for more precise oestrous synchronization and improved superovulatory response.Nutrition can influence a whole range of reproductive parameters however, the pathways through which nutrition acts have not been fully elucidated. Metabolic hormones, particularly insulin and IGFs, appear to interact with gonadotrophins at the level of the gonads. Certainly gonadotropins provide the primary drive for the growth of follicles in the later stages of development and both insulin and IGF-1, possibly IGF-2, synergize with gonadotrophins to stimulate cell proliferation and hormone production. More research is required to determine the effects of other growth factors and their interaction with gonadotropins.There is evidence, particularly from studies with rodents, that steroids can also modulate follicular growth and development, although information is very limited for ruminants. There may be a rôle for oestrogens in synchronizing follicular waves, to aid in oestrous synchronization regimes and for removing the dominant follicle to achieve improved superovulatory responses. However more information is required to determine whether these are feasible approaches.Heritability for litter size is higher in sheep than in cattle. Exogenous gonadotropins are a commercially ineffective means of inducing twinning in sheep and cattle. Although there are differences in circulating gonadotropin concentrations, the mechanism(s) responsible for the high ovulation appear to reside essentially within the ovaries. The locus of the Booroola gene, a major gene for ovulation rate, has been established but not specifically identified. However sheep possessing major genes do provide extremely valuable models for investigating the mechanisms controlling ovulation rate, including a direct contrast to mono-ovulatory species such as cattle.In conclusion, the relationship between oocyte quality, in both healthy follicles and those follicles destined for atresia, must be resolved before the future potential for increasing embryo yield can be predicted. In addition, a greater understanding of the factors affecting folliculogenesis in ruminants should ensure that the full benefits ensuing from the precise control of ovarian function are achieved. The improved use of artificial insemination and embryo transfer that would ensue from a greater understanding of the processes of folliculo genesis, coupled with the new technologies of genome and linkage mapping, should ensure a more rapid rate of genetic gain.

173 THE EFFECT OF EXERCISE ON FOLLICULOGENESIS IN MARES

2009 ◽  
Vol 21 (1) ◽  
pp. 185 ◽  
Author(s):  
D. E. Kelley ◽  
J. R. Gibbons ◽  
S. E. Pratt ◽  
R. L. Smith ◽  
C. J. Mortensen
Keyword(s):  
Growth Rate ◽  
Heat Stress ◽  
Transrectal Ultrasound ◽  
Follicular Development ◽  
Control Group ◽  
Follicular Growth ◽  
Embryo Recovery ◽  
Conditioning Period ◽  
Before And After ◽  
The Impact

The effects of exercise on follicular development in mares have not been well established; however, a combination of exercise and heat stress can negatively affect embryo recovery rate in mares. The purpose of this research was to examine the effects of exercise, independent of heat stress, on follicular development in mares. One thoroughbred and 12 quarter horse mares, aged 3 to 15 years, were used in this study. Mares were assigned to the control group or exercised at 0700 h, 6 days a week, as follows: warmed up 5 min at a walk for 3 m s–1 and then exercised 30 min, 9 m s–1 for 10 min, 13 m s–1 for 5 min, 9 m s–1 for 5 min, 13 m s–1 for 5 min, and 9 m s–1 for 5 min. Exercised mares were given a 1-month conditioning period. Rectal temperatures were recorded immediately before and after exercise. The mean rectal temperature of mares increased by 0.85°C during exercise, whereas control mares under the same environmental conditions did not experience temperature increases. Individual mares underwent a daily transrectal ultrasound examination with a 7.5-MHz linear rectal probe to monitor follicular development. Estrous cycles were normalized to 17 days for linear follicular growth analysis. Exercise had a significant impact on follicular growth at deviation, with a greater diameter of the largest (P < 0.05) and second largest (P < 0.01) follicles in exercised v. control mares (Table 1). Additionally, growth rate of the second largest follicle was greater in the exercised group (P < 0.01). Deviation was observed in 13 of 14 cycles in control mares, whereas in exercised mares, it was clear in only 11 of 16 cycles (χ2, P = 0.086). Time of deviation was defined as the day when a difference in the growth rate between the dominant and largest subordinate follicle of a wave was first observed. The largest subordinate follicle either declined in growth rate or regressed. At Day –5 (relative to ovulation), exercised mares had significantly greater follicle diameters in both the largest and second largest follicle (P < 0.05). Exercised mares had double ovulations in 4 of 16 cycles when compared with control mares, which had double ovulations in 1 of 14 cycles. No differences were found between groups in the length of the estrous cycle or ovulatory follicular diameter. Exercised mares exhibited larger diameter follicles and an increased growth rate of the largest subordinate follicle, suggesting that exercise delayed deviation. Further research is needed to assess the impact of exercise, independent of heat stress, on fertility. Table 1.Follicle dynamics in exercised v. non-exercised mares

175 FOLLICULAR DEVELOPMENT AND OVARIAN BLOOD FLOW IN MARES WITH EARLY OR LATE OVULATION POSTPARTUM

2015 ◽  
Vol 27 (1) ◽  
pp. 178
Author(s):  
K. M. Lemes ◽  
L. A. Silva ◽  
E. C. C. Celeghini ◽  
M. A. Alonso ◽  
G. Pugliesi ◽  
...  
Keyword(s):  
Blood Flow ◽  
Postpartum Period ◽  
Follicular Development ◽  
Ovarian Activity ◽  
Follicle Development ◽  
Follicular Growth ◽  
Dominant Follicle ◽  
Vascular Perfusion ◽  
Early Postpartum ◽  
Linear Probe

The postpartum period is characterised by the rapid uterine involution process and return of ovarian activity (foal heat), resulting in a fertile oestrus in most of the mares. However, the follicular development and selection processes during this period are not completely known in horses. We aimed to study the characteristics of follicular growth and vascular perfusion in the ovary during the early postpartum period in mares that demonstrated oestrous behaviour and had early (<10 days) or late (≥10 days) ovulation. Ten mares were scanned daily from the first day postpartum (Day 1) until the day of the first postpartum ovulation (Day 0). The animals were split in the early (n = 3) and late (n = 7) ovulation groups (averaged interval between parturition and ovulation: 8.0 ± 0.0 and 14.7 ± 1.2 days, respectively). For ultrasound exams a Duplex B-mode and colour Doppler instrument (M5VET®, Mindray, Shenzhen, China) was used with a multifrequency linear probe. Data were analysed for the main effects of group, day, and their interaction using the PROC MIXED procedure of SAS software (version 9.3, SAS Institute Inc., Cary, NC, USA). For the follicular growth, no difference (P > 0.05) was detected between the groups when the data were analysed for the days relative to ovulation (from Day 7 to Day 1). However, the dominant follicle was larger (P < 0.05) in the early-ovulated group (37.2 ± 1.6 v. 21.9 ± 1.1) in all days during early postpartum (Day 1 to Day 7). The number of follicles with >25 mm diameter was also greater (P < 0.05) in the early-ovulated group (1.1 ± 0.1 v. 0.1 ± 0.1) during the first 3 days postpartum. In addition, the late-ovulated mares showed greater number of follicles with 20–25 mm during Day 4 to Day 7 (2.0 ± 0.2 v. 0.7 ± 0.1). For the blood flow characteristics, no difference (P > 0.05) was detected in the coloured signals of blood flows in the follicular wall of the dominant follicle or in the ovarian pedicle ipsilateral to the largest follicle. Therefore, the characteristics of the follicle growth on the preceding days of ovulation were similar between the early- and late-ovulated mares and consistent with the follicular dynamics expected in non-pregnant and non-lactating mares. However, when the data were analysed for the days relative to parturition, a greater follicle development was present in mares that ovulate earlier during the postpartum period (<10 days). In conclusion, the results suggest that important events may occur previous to the parturition, resulting in an early follicle development, mainly in those mares that show heat signs and ovulate within 10 days postpartum. Research was supported by FAPESP process number 2010/10692-9 and CNPq process number 135954/2011-8.

Effects of presynchronization and eCG on pregnancy rates to GnRH-based, fixed-time artificial insemination in beef heifers

2010 ◽  
Vol 90 (1) ◽  
pp. 23-34 ◽  
Author(s):  
J A Small ◽  
M G Colazo ◽  
J P Kastelic ◽  
N E Erickson ◽  
R J Mapletoft
Keyword(s):  
Chorionic Gonadotropin ◽  
Artificial Insemination ◽  
Follicular Development ◽  
Fixed Time ◽  
Pregnancy Rates ◽  
Preovulatory Follicle ◽  
Beef Heifers ◽  
Plasma Progesterone ◽  
Follicle Diameter ◽  
Equine Chorionic Gonadotropin

Three experiments were conducted to determine the effects of presynchronization and treatment with equine chorionic gonadotropin (eCG) on corpus luteum (CL) and ovarian follicular development, plasma progesterone concentrations, and pregnancy rates in beef heifers subjected to a gonadotropin releasing hormone (GnRH)-based, fixed-timed AI (TAI) protocol. All heifers were given GnRH on day 0, prostaglandin F2α (PGF) on day 7, and a second GnRH on day 9 concurrent with TAI (54 h after PGF). In exp. 1 (N = 148), presynchronization with PGF (days -22 and -11) decreased the percentage of heifers with non-luteal plasma progesterone concentrations on day 0 (5.4 vs 29.7%) and day 7 (0 vs 11.6%; P < 0.05), but not on day 9 (74.3 vs. 66.2%; P > 0.20), and reduced the number of heifers in estrus and bred before TAI (P < 0.05). Although presynchronization reduced preovulatory follicle diameter (12.9 ± 0.3 vs. 14.9 ± 0.3 mm; mean ± SEM; P < 0.01), it did not affect TAI pregnancy rates (36.5 vs. 29.7%; P > 0.20). In exp. 2, heifers (N = 128) were presynchronized with melengestrol acetate (MGA) (days -27 to -12), and received a controlled internal drug release (CIDR) on day 0; on day 7, half were given 300 IU of eCG at CIDR removal. Treatment with eCG tended to increase preovulatory follicle diameter in heifers that did not ovulate to GnRH on day 0 (P = 0.06), but did not affect the percentage of heifers with non-luteal plasma progesterone concentrations on day 9 (57.8 vs. 57.8%) or TAI pregnancy rates (48.4 vs. 53.1%; P > 0.20). Experiment 3 was a 2 × 2 factorial arrangement of presynchronization (PGF concurrent with a CIDR on day -7) and eCG treatments (on day 7) applied to heifers in three herds (A, N = 150, B, N = 260 and C, N = 40). All heifers had a once-used CIDR from days 0 to 7. Presynchronization increased the percentage of heifers (Herd A) with low-luteal plasma progesterone concentrations on day 0 (70.7 vs. 22.7%) and day 7 (90.7 vs. 53.3%; P < 0.01), but did not affect the percentage of heifers with non-luteal concentrations of progesterone on day 9 (97.3 vs. 93.3%; P > 0.20). Combined for all herds, presynchronization reduced the prevalence of a CL on day 0 (23.5 vs. 73.7%; P < 0.01), and increased the prevalence of follicles ≥ 10 mm on day 7 (96.8 vs. 86.7%; P < 0.01); however, TAI pregnancy rates (195/439 = 44.4%) were not improved by either presynchronization or eCG treatment (P > 0.20).Key words: Presynchronization, equine chorionic gonadotropin, GnRH, fixed-time artificial insemination, progesterone

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