Morphological and functional characteristics of the dominant follicle and corpus luteum in cattle and their influence on ovarian function

2001 ◽  
Vol 56 (4) ◽  
pp. 569-576 ◽  
Author(s):  
A Ali ◽  
A Lange ◽  
M Gilles ◽  
P.S Glatzel
Keyword(s):  
Corpus Luteum ◽  
Ovarian Function ◽  
Dominant Follicle ◽  
Functional Characteristics

4 Induction of ovulation by kisspeptin in llamas

2019 ◽  
Vol 31 (1) ◽  
pp. 127 ◽  
Author(s):  
R. A. Carrasco ◽  
C. E. Leonardi ◽  
K. D. Hutt ◽  
J. Singh ◽  
G. P. Adams
Keyword(s):  
Body Weight ◽  
Corpus Luteum ◽  
Repeated Measures ◽  
Ovarian Function ◽  
Gnrh Receptor ◽  
Response To Treatment ◽  
Transrectal Ultrasonography ◽  
Control Group ◽  
Gnrh Analogue ◽  
Dominant Follicle

After mating, female camelids ovulate in response to nerve growth factor (NGF) present in semen (formerly referred to as ovulation-inducing factor). The ovulatory effect appears to be induced by stimulation of hypothalamic gonadotropin-releasing hormone (GnRH) neuronal activity and LH secretion. Recent studies have identified kisspeptin as an important mediator of GnRH secretion in several species. In the present study, we tested the hypothesis that kisspeptin is involved in the ovulatory pathway in llamas and investigated the mechanism of this effect. In Experiment 1, ovarian function in non-pregnant, non-lactating adult female llamas was synchronized by intramuscular administration of a GnRH analogue (50µg of gonadorelin acetate; Fertiline, Vetoquinol, Quebec, QC, Canada). When a growing dominant follicle ≥8mm in diameter was detected, llamas were assigned randomly to 3 treatment groups and given an intravenous dose of purified seminal NGF (1mg, single dose; n=5), kisspeptin (0.1mg kg−1 of body weight, 2 doses 1h apart; n=5), or PBS (n=4). The bioactive 10 amino acid fragment of murine kisspeptin was used. Ovulation and corpus luteum development were assessed by transrectal ultrasonography every other day from the day of treatment (Day 0) to Day 8. In Experiment 2, ovarian function among female llamas was synchronized, as in Experiment 1. When a growing dominant follicle ≥8mm in diameter was detected, llamas were given kisspeptin (0.1mg kg−1 of body weight IV, 2 doses 1h apart) beginning 2h after pretreatment with either a GnRH receptor blocker (cetrorelix acetate, 1.5mg per llama IV; Sigma, Oakville, ON, Canada; n=6) or saline (n=6). Llamas were examined 48h later by transrectal ultrasonography to detect ovulation and 8 days later to determine the presence of a corpus luteum. Chi-square tests were used to compare ovulation rates, and ANOVA for repeated measures was used to compare diameter profiles of the corpus luteum. In Experiment 1, ovulation rate did not differ between the NGF and kisspeptin groups (5/5 in each; 100%) and was greater than in the control group (0/4; 0% P<0.05). Corpus luteum diameter did not differ between llamas that ovulated in response to treatment with NGF or kisspeptin (13.2±0.8 and 14.0±1.2mm on Day 8, respectively). In Experiment 2, none of the llamas pretreated with cetrorelix ovulated in response to kisspeptin treatment (0/6; 0%), whereas all of the llamas pretreated with saline ovulated in response to kisspeptin treatment and had a corpus luteum at Day 8 (6/6; 100%; P<0.05). Results supported the hypothesis that kisspeptin induces ovulation in llamas. Because a GnRH receptor antagonist blocked ovulation, our interpretation is that the site of action of kisspeptin is upstream of the pituitary gland and involves control of GnRH release from the hypothalamus. These findings raise the possibility that kisspeptin mediates the ovulation-inducing effect of NGF. Research was supported by the Natural Sciences and Engineering Research Council of Canada.

Effects of extending the length of pro-oestrus in an oestradiol- and progesterone-based oestrus synchronisation program on ovarian function, uterine environment and pregnancy establishment in beef heifers

2018 ◽  
Vol 30 (11) ◽  
pp. 1541 ◽  
Author(s):  
J. J. de la Mata ◽  
R. Núñez-Olivera ◽  
F. Cuadro ◽  
D. Bosolasco ◽  
V. de Brun ◽  
...  
Keyword(s):  
Ovarian Function ◽  
Progesterone Receptors ◽  
Fixed Time ◽  
Conventional Group ◽  
Dominant Follicle ◽  
Beef Heifers ◽  
Serum Progesterone ◽  
Ovulatory Follicle ◽  
Sexual Steroid ◽  
Uterine Environment

The aim of the present study was to investigate the effects of a strategy for extending pro-oestrus (the interval between luteolysis and ovulation) in an oestrus synchronisation protocol (named J-Synch) in beef heifers on follicular growth, sexual steroid concentrations, the oestrogen receptor ERα and progesterone receptors (PR) in the uterus, insulin-like growth factor (IGF) 1 and pregnancy rates. In Experiment 1, heifers treated with the new J-Synch protocol had a longer pro-oestrus period than those treated with the conventional protocol (mean (± s.e.m.) 93.7 ± 12.9 vs 65.0 ± 13.7 h respectively; P < 0.05). The rate of dominant follicle growth from the time of progesterone device removal to ovulation was greater in heifers in the J-Synch than conventional group (P < 0.05). Luteal area and serum progesterone concentrations were greater in the J-Synch Group (P < 0.05) for the 12 days after ovulation. Progesterone receptor (PGR) staining on Day 6 after ovulation in the uterine stroma was lower in the J-Synch than conventional group (P < 0.05), and the expression of PR gene (PGR) and IGF1 gene tended to be lower in J-Synch-treated heifers (P < 0.1). In Experiment 2 (n = 2349), the pregnancy rate 30–35 days after fixed-time AI (FTAI) was greater for heifers in the J-Synch than conventional group (56.1% vs 50.7% respectively). In conclusion, our strategy for extending pro-oestrus (i.e. the J-Synch protocol) significantly improves pregnancy establishment in beef heifers. This improvement was related to an increased rate of growth of the dominant ovulatory follicle, greater progesterone concentrations during the ensuing luteal phase and different uterine patterns of PGR and IGF1, which may have favoured embryo development and pregnancy establishment.

Studies on Ovarian Follicular Dynamics and Steroid Profiles in Sahiwal Cattle

2021 ◽  
Author(s):  
Vinny Dodiyar ◽  
Parkash Singh Brar ◽  
Narinder Singh ◽  
Mrigank Honparkhe
Keyword(s):  
Corpus Luteum ◽  
Estrous Cycle ◽  
Maximum Diameter ◽  
Endocrine Regulation ◽  
Dominant Follicle ◽  
Estrous Cycles ◽  
Significant Difference ◽  
Sahiwal Cattle ◽  
Sahiwal Cows ◽  
Follicular Dynamics

Background: Understanding of ovarian follicular dynamics and endocrine regulation is essential to design and use interventions to optimize reproductive efficiency. Bos indicus and Bos taurus cows have some differences in their follicular dynamics and ovarian steroidal hormones. The present study was planned to understand follicular dynamics vis-a-vis ovarian steroids profiles in Sahiwal cattle. Methods: The study was conducted in normal cyclic, pluriparous, non-lactating Sahiwal cows (n=7). Trans-rectal ultrasonography was performed to record the location, size, number of follicles and size of corpus luteum (CL) from the beginning, till the end of experiment. The dataset was used to characterize the follicular wave emergence, growth, regression, time of selection and ovulation of the dominant follicle in each cow. Result: Three Sahiwal cows showed two wave and four cows showed three wave estrous cycles with mean interovulatory length of 20.33±0.33 and 22.50±0.28 days, respectively. No significant difference was recorded in the maximum diameter of corpus luteum, P4 and E2 plasma levels between 2-wave and 3-wave estrous cycles. The peak progesterone values of 6.00±0.91 and 6.2±1.2 ng/ml and peak estradiol values of 15.83±0.60 and 14.31±0.44 ng/ml were recorded in 2-wave and 3-wave estrous cycle, respectively. The results showed that Sahiwal cows had 2-wave and 3-wave estrous cycle and the 3-wave estrous cycle had comparatively longer inter-ovulatory period and smaller maximum diameter of second wave dominant follicle than 2-wave estrous cycle.

scholarly journals Prolactin independent rescue of mouse corpus luteum life span: identification of prolactin and luteinizing hormone target genes

2009 ◽  
Vol 297 (3) ◽  
pp. E676-E684 ◽  
Author(s):  
Anne Bachelot ◽  
Julie Beaufaron ◽  
Nathalie Servel ◽  
Cécile Kedzia ◽  
Philippe Monget ◽  
...  
Keyword(s):  
Luteinizing Hormone ◽  
Corpus Luteum ◽  
Molecular Mechanisms ◽  
Target Genes ◽  
Ovarian Function ◽  
De Novo ◽  
Embryo Implantation ◽  
Receptor Expression ◽  
Corpora Lutea ◽  
Mrna Expression Profiling

The corpus luteum (CL) plays a central role in the maintenance of pregnancy in rodents, mainly by secreting progesterone. Female mice lacking prolactin (PRL) receptor (R) are sterile due to a failure of embryo implantation, which is a consequence of decreased luteinizing hormone (LH) receptor expression in the CL and inadequate levels of progesterone. We attempted to treat PRLR−/− females with human chorionic gonadotropin (hCG) and showed a de novo expression of LHR mRNA in the corpora lutea. Binding analysis confirmed that the LHR in hCG-treated PRLR−/− animals was functional. This was accompanied with increased expression of steroidogenic enzymes involved in progesterone synthesis. Despite these effects, no embryo implantation was observed because of high expression of 20α-hydroxysteroid dehydrogenase. To better appreciate the molecular mechanisms underlying maintenance of the CL, a series of mRNA expression-profiling experiments was performed on isolated corpora lutea of PRLR−/− and hCG-treated PRLR−/− mice. This approach revealed several novel candidate genes with potentially pivotal roles in ovarian function, among them, p27, VE-cadherin, Pten, and sFRP-4, a member of the Wnt/frizzled family. This study showed the differential role of PRL and LH in CL function and identified new targets of these hormones in luteal cells.

Elements of functional genital asymmetry in the cow

2014 ◽  
Vol 26 (4) ◽  
pp. 493 ◽  
Author(s):  
B. Trigal ◽  
C. Díez ◽  
M. Muñoz ◽  
J. N. Caamaño ◽  
F. Goyache ◽  
...  
Keyword(s):  
Corpus Luteum ◽  
Ovarian Function ◽  
Pregnancy Rates ◽  
Actin Binding ◽  
Complement Factor ◽  
Follicle Diameter ◽  
Ovulatory Follicle ◽  
The Right ◽  
Uterine Proteins

Asymmetry in the cow affects ovarian function and pregnancy. In this work we studied ovarian and uterine asymmetry. Synchronised animals, in which in vitro-produced embryos (n = 30–60) had been transferred on Day 5 to the uterine horn ipsilateral to the corpus luteum (CL), were flushed on Day 8. Ovulatory follicle diameter, oestrus response and total protein flushed did not differ between sides. However, a corpus luteum in the right ovary led to plasma progesterone concentrations that were higher than when it was present in the left ovary. Fewer embryos were recovered from the left than the right horn. Among 60 uterine proteins identified by difference gel electrophoresis, relative abundance of nine (acyl-CoA dehydrogenase, very long chain; twinfilin, actin-binding protein, homologue 1; enolase 1; pyruvate kinase isozymes M1/M2 (rabbit); complement factor B Bb fragment ; albumin; fibrinogen gamma-B chain; and ezrin differed (P < 0.05) between horns. Glucose concentration was higher, and fructose concentration lower, in the left horn. In a subsequent field trial, pregnancy rates after embryo transfer did not differ between horns (51.0 ± 3.6, right vs 53.2 ± 4.7, left). However, Day 7 blood progesterone concentrations differed (P = 0.018) between pregnant and open animals in the left (15.9 ± 1.7 vs 8.3 ± 1.2) but not in the right horn (12.4 ± 1.3 vs 12.4 ± 1.2). Progesterone effects were independent of CL quality (P = 0.55). Bilateral genital tract asymmetry in the cow affects progesterone, proteins and hexoses without altering pregnancy rates.

164 EFFECT OF OVULATION-INDUCING FACTOR (OIF) ON OVARIAN FUNCTION IN CATTLE

2008 ◽  
Vol 20 (1) ◽  
pp. 162 ◽  
Author(s):  
M. D. Van Steelandt ◽  
V. M. Tanco ◽  
M. H. Ratto ◽  
G. P. Adams
Keyword(s):  
Seminal Plasma ◽  
Ovarian Function ◽  
Bos Taurus ◽  
Suppressive Effect ◽  
Positive Control ◽  
Negative Control ◽  
Dominant Follicle ◽  
Wave Dynamics ◽  
Follicular Wave ◽  
As Species

Systemic administration of ovulation-inducing factor (OIF), discovered recently in seminal plasma of llamas, alpacas (induced ovulators), and cattle (spontaneous ovulators), stimulated ovulation in >90% of female llamas and alpacas. The objective of the present study was to test the hypothesis that purified OIF from llama seminal plasma would induce ovulation in cattle. Peripubertal heifers, weighing 323 � 27 kg, were used to minimize the confounding effect of spontaneous ovulation. Heifers (n = 11/group) were treated intramuscularly with 1.0 mg/100 kg of purified OIF, 100 µg of GnRH (positive control), or 2.5 mL of phosphate-buffered saline (negative control). Ovarian dynamics were monitored daily by transrectal ultrasonography for 10 days post-treatment. Blood samples were collected at 0.5- to 1-h intervals for 8 h, beginning at the time of treatment. Ovulation occurred in 9/11 (82%) of GnRH-treated heifers and in 1/11 (9%) heifers in each of the OIF- and saline-treated groups (P < 0.05). A surge in plasma LH concentration was detected within 30 min of treatment in the GnRH group (2.2 � 0.1 ng mL–1; P < 0.05), but remained at the basal level in the OIF- and saline-treated groups (0.3 � 0.1 and 0.2 � 0.1 ng mL–1, respectively). The onset of regression of the dominant follicle present at the time of treatment was earlier (P < 0.05) in OIF- v. saline-treated heifers (3.1 � 0.6 days v. 6.0 � 0.7 days). The interval from treatment to follicular wave emergence was shorter (P < 0.05) in GnRH- and OIF-treated heifers than in those treated with saline (1.1 � 0.4 days, 1.5 � 0.3 days, and 3.1 � 0.3 days, respectively). A similar pattern was observed for emergence of the second follicular wave (5.1 � 0.7 days, 4.6 � 0.5 days, and 6.6 � 0.4 days, respectively). Purified OIF did not induce ovulation in heifers but hastened both the regression of the extant dominant follicle and follicular wave emergence. Results provide a rationale for the hypothesis that OIF from seminal plasma is involved in controlling follicular wave dynamics in spontaneously ovulating species (e.g., Bos taurus) through a suppressive effect on the dominant follicle. The mechanism of action on ovarian follicular wave dynamics, as well as species specificity, remains to be elucidated.

179 CORPUS LUTEUM DEVELOPMENT AFTER FOLLICLE ASPIRATION IS RELATED TO CHARACTERISTICS OF THE ASPIRATED FOLLICLE IN DAIRY COWS

2013 ◽  
Vol 25 (1) ◽  
pp. 238
Author(s):  
A. Vernunft ◽  
J. M. Weitzel ◽  
T. Viergutz
Keyword(s):  
Corpus Luteum ◽  
Cross Section ◽  
Quality Parameter ◽  
Preovulatory Follicle ◽  
Dominant Follicle ◽  
Cross Section Area ◽  
Section Area ◽  
Luteal Tissue ◽  
The Cross ◽  
Follicle Aspiration

The aim of this study was to investigate whether morphology or function of a corpus luteum (CL), which developed after an aspiration of a preovulatory follicle, is related to follicular characteristics such as size or steroid content. If so, CL morphology or function could be used as a retrospective quality parameter for the aspirated follicle or the follicular characteristics as a prospective parameter for the quality of the developing CL. Therefore, 44 aspiration sessions were performed using 18 cows between 26 and 121 days after parturition during the first lactation. Heat was induced in mid-dioestrus with Cloprostenol. A GnRH analogon (Depherelin) were administrated 54 h later. The dominant follicle was aspirated 21 h after administration of the GnRH analogue. The diameter of the dominant follicle at aspiration and the cross-section area of the resulting luteal tissue 14 days later were measured by ultrasound. Concentrations of progesterone (P4) and 17-β-oestradiol (E2) in blood and follicular fluid (FF) were determined by H3-RIA. A CL development occurred in 82% of aspiration sessions after aspirating the dominant follicles. The interval of time between parturition and follicle aspiration did not affect variables investigated. As expected, cross-section area of the luteal tissue was positively correlated with plasma P4 concentration on Day 14 after follicle aspiration (r = 0.54; P < 0.01). The diameter of the aspirated follicle was positively correlated with the plasma P4 concentration on Day 14 after follicle aspiration (r = 0.52; P = 0.02), but the diameter was not correlated with the cross-section. Comparing the FF of follicles that originated a CL after aspiration with follicles that did not, both types had comparable P4 concentrations (578 ± 79 ng mL–1 v. 398 ± 84 ng mL–1; P = 0.2), but the former type presented higher E2 concentrations (206 ± 23 ng mL–1 v. 64 ± 29 ng mL–1, P < 0.01) compared with the latter. The P4 concentrations in FF of follicles that originated a CL after aspiration were positively related to cross-section area of the CL (r = 0.48; P = 0.04), but neither P4 nor E2 concentrations in the FF of preovulatory follicles could be used as a predictor for the plasma P4 concentration at day 14. In conclusion, CL development after follicle aspiration can be used as a retrospective quality parameter of aspirated dominant follicles. Preovulatory follicle diameter as well as cross-section area of the luteal tissue could be used prospectively to identify cows with high plasma P4 levels, and this may help to identify suitable recipients for embryo transfer. This study was supported by the German Research Foundation (DFG WE 2458/7-2).

IN-VITRO STEROIDOGENESIS OF NEWLY FORMED CORPORA LUTEA AND THE NON-LUTEAL OVARY IN THE RAT, RABBIT, HAMSTER AND GUINEA-PIG

1980 ◽  
Vol 84 (1) ◽  
pp. 101-108 ◽  
Author(s):  
P. F. TERRANOVA ◽  
S. K. SAIDAPUR ◽  
G. S. GREENWALD
Keyword(s):  
Guinea Pig ◽  
Corpus Luteum ◽  
Ovarian Function ◽  
Serum Testosterone ◽  
The Other ◽  
Corpora Lutea ◽  
Serum Progesterone ◽  
Antral Follicles ◽  
Baseline Levels

The steroidogenic abilities of the newly formed corpus luteum (8–10 h after ovulation) and the non-luteal ovary were compared in the guinea-pig, hamster, rabbit and rat using an invitro incubation technique. Histologically, newly formed rat corpora lutea (CL) were highly luteinized whereas the CL of the rabbit and guinea-pig were only partially luteinized. The CL of the hamster showed the least amount of luteinization. Serum progesterone was highest in the rat (18 ± 3 (s.e.m.) ng/ml). In the hamster, it was about 8 ng/ml, whereas in the rabbit and guinea-pig it was about 1 ng/ml. Serum androstenedione ranged between 0·5 and 1 ng/ml. Serum testosterone was lowest in the hamster (60 pg/ml) and highest in the rabbit (470 pg/ml), whereas in the rat and guinea-pig, testosterone levels were similar (about 240 pg/ml). Serum oestrogens were at baseline levels in all species. The CL of the rat exhibited considerably greater steroidogenic ability than the CL of the other species, producing 70 ± 6 ng progesterone/mg per h, 215 ± 14 pg androstenedione/mg per h, 49 ± 3 pg testosterone/mg per h, 3 pg oestrone/mg per h and 1 pg oestradiol/mg per h. Rabbit CL produced only progesterone (7 ± 2 ng/mg per h). Newly formed hamster CL produced none of the above steroids. In general, the ability of the CL to produce progesterone in vitro correlated with the degree of luteinization found by histological observation. Guinea-pig CL were embedded deeply in the ovary and could not be obtained without damage. Consequently, a portion of the ovary containing a corpus luteum was incubated. There was no difference in the steroid production by this portion of the ovary compared with the non-luteal ovary. The non-luteal ovary of the rat produced the highest amount of progesterone (10 ± 2 ng/mg per h). The guinea-pig non-luteal ovary produced about 5 ± 2 ng progesterone/mg per h, whereas the non-luteal ovary of the rabbit did not produce any. On the other hand, the hamster non-luteal ovary lost progesterone. Non-luteal ovaries from all species produced androgens. The non-luteal ovary of the guinea-pig contained especially large numbers of atretic antral follicles. The guinea-pig non-luteal ovary produced extremely large amounts of androstenedione (1110 ± 210 pg/mg per h) and testosterone (606 ± 154 pg/mg per h) compared with the amounts produced by the non-luteal ovary of the rat, hamster and rabbit. In the non-luteal ovary, interstitium and atretic antral follicles are the probable source of androgens. Oestrogen production by the non-luteal ovary was at baseline levels in the four species studied correlating with the absence of healthy antral follicles. The results indicate the extreme species differences that exist in ovarian function in the early postovulatory period.

scholarly journals Relationship between metabolic hormones and ovulation of dominant follicle during the first follicular wave post-partum in high-producing dairy cows

Reproduction ◽  
2007 ◽  
Vol 133 (1) ◽  
pp. 155-163 ◽  
Author(s):  
Chiho Kawashima ◽  
Saori Fukihara ◽  
Mayumi Maeda ◽  
Etsushi Kaneko ◽  
Carlos Amaya Montoya ◽  
...  
Keyword(s):  
Blood Flow ◽  
Dairy Cows ◽  
Ovarian Function ◽  
Post Partum ◽  
Plasma Concentrations ◽  
Reproductive Hormones ◽  
Follicular Growth ◽  
Dominant Follicle ◽  
Follicular Wave ◽  
Igf I

Recent studies suggest that IGF-I is a crucial regulatory factor in follicular growth during earlypost-partumperiod. The aim of the present study was to determine in detail the changing profiles of metabolic and reproductive hormones in relation to ovulation of the dominant follicle (DF) of the first follicular wavepost-partumin high-producing dairy cows. Plasma concentrations of related hormones in 22 multiparous Holstein cows were measured from 4 weeks pre-partum to 3 weekspost-partum, and the development of DF was observed with colour Doppler ultrasound. Thirteen cows showed ovulation by 15.2 dayspost-partum. Anovulatory cows showed higher GH and lower IGF-I levels than those in ovulatory cows during the peri-partum period. Each DF developed similarly, and a clear blood flow in the follicle wall was observed despite ovulation or anovulation. In addition, detailed endocrine profiles were analyzed in 9 out of the 22 cows. Five cows showed an increase in plasma oestradiol-17β (E2) with follicular growth followed by E2 peak, LH surge and ovulation. In these cows, plasma IGF-I concentrations remained high until 10 dayspost-partumfollowed by a gradual decrease. Subsequently, the insulin level increased together with the E2 peak towards ovulation. These profiles were not observed in anovulatory cows. In conclusion, our data strongly support the concept that IGF-I and insulin represent ‘metabolic signals’ of the resumption of ovarian functionpost-partumin high-producing dairy cows. Moreover, we provide the first visual evidence that both ovulatory and anovulatory DFs of the first follicular wavepost-partumare similarly supplied with active blood flow.

177 EFFECTS OF MANIPULATION OF DOMINANT FOLLICLE GROWTH ON SIZE AND FUNCTION OF CORPUS LUTEUM IN BEEF CATTLE

2013 ◽  
Vol 25 (1) ◽  
pp. 237
Author(s):  
R. S. Ramos ◽  
F. S. Mesquita ◽  
G. Pugliesi ◽  
S. C. Scolari ◽  
M. L. Oliveira ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Corpus Luteum ◽  
Prostaglandin F2α ◽  
Progressive Increase ◽  
Group Effect ◽  
Dominant Follicle ◽  
Follicle Growth ◽  
Ovulatory Follicle ◽  
Conception Rates ◽  
And Function

Recent evidence indicates that the progesterone (P4) secretion by corpus luteum (CL) during early diestrus is affected by the size of ovulatory follicle and has a significant impact on embryo development and conception rates. Therefore, strategies to promote the growth of the dominant follicle and/or to stimulate the early development of the CL to increase P4 secretion become an alternative to improve conception rates in the beef cattle industry. Our aim was to study the effect of manipulations of the follicle growth on the diameter of the preovulatory follicle (POF) and subsequent size and function of the CL. Cyclic and non-lactating Nelore cows, pre-synchronized by 2 injections of prostaglandin F2α (PGF) 14 d apart, were manipulated to ovulate large or small follicles according to 3 experiments. In Experiment 1 (Exp. 1; n = 23), animals received a second-use intravaginal P4-releasing device along with an injection of oestradiol benzoate on Day –10 (Day 0 = GnRH injection). Cows were split to receive (large follicle group; LF) or not (small follicle group; SF) a PGF injection on Day –10. Progesterone devices were removed on Day –2.5 in the LF group and on Day –1.5 in the SF group. The PGF was injected at the removal of the P4 device. In Experiment 2 (Exp. 2; n = 38), cows in the LF group had the P4 device removed on Day –2.25 or Day –2, whereas in Experiment 3 (Exp. 3; n = 23), the device (first-use) was removed on Day –1.75 in the LF group and on Day –1.25 in the SF group; the other manipulations were similar to Exp. 1. Data analyses were done only on cows that had a functional CL on Day –10 (P4 > 1 ng mL–1) and that ovulated within 24 and 48 h post-GnRH (Exp. 1, n = 14; Exp. 2, n = 14; Exp. 3, n = 12). The three experiments were successful in inducing POF with different sizes, as indicated by the greater diameter of the POF in the LF group compared with SF in Exp. 1 (12.9 ± 0.5 mm v. 10.7 ± 0.6 mm; P < 0.03), Exp. 2 (14.1 ± 0.6 mm v. 11.7 ± 0.4 mm; P < 0.006), and Exp. 3 (13.8 ± 0.6 mm v. 11.7 ± 0.8 mm; P < 0.06). To evaluate the effect of POF size on size and function of the CL, a factorial analysis was performed by SAS software to test the effect of group, day, and their interaction. For CL volume, an effect of group was detected in Exp. 1 (P < 0.02) and in Exp. 3 (P < 0.06), but not in Exp. 2. The group effect represented greater average CL volume from Day 3 to Day 7 in LF (2.42 ± 0.27 and 2.5 ± 0.39 cm3) than in the SF group (1.39 ± 0.18 and 1.2 ± 0.15 cm3) for Exp. 1 and 3, respectively. For P4 concentrations, a group effect was detected only in Exp. 3 (P < 0.007), as indicated by greater average P4 concentrations from Day 3 to Day 7 in LF (2.31 ± 0.31 ng mL–1) than in the SF group (1.37 ± 0.19 ng mL–1). A day effect was detected in all experiments (P < 0.0001), as indicated by a progressive increase of CL volume and P4 concentrations from Day 3 to Day 7. Manipulation of follicle growth performed in Exp. 3 was the most efficient to modify the function and size of the CL. In conclusion, control of POF size by manipulation of P4 concentrations during growth of the dominant follicle alters the size and function of CL postovulation. CNPq, FAPESP, Ourofino, and PUSP-P.

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