1,721,012 research outputs found
Association between numbers of ovarian follicles in the first follicle wave and superovulatory response in ewes
No full textThe aim of this study was to examine the variability in the number of ovarian follicles in sheep and to determine if the average number of follicles per day influences the response to superovulation and resulting embryo quality. Ewes (n=83) were synchronized and the number of follicles (> or =2 mm diameter) in the ovaries were counted daily between Days 0 and 4 of the oestrous cycle using transrectal ultrasonography. Fourteen to 21 days later, 47 ewes were randomly chosen from the group and were treated with an intravaginal progestagen pessary for 12 days and superovulated with 1500 IU eCG administered as a single injection 10 days after sponge insertion. Ewes were mated and reproductive tracts were recovered after slaughter on Day 6 of pregnancy. The number of corpora lutea was counted, uterine horns were flushed and the morphology and developmental stage of the recovered oocytes/embryos was assessed. The mean daily number (+/-S.D.) (> or =2 mm diameter) of follicles per ewe was 8.5+/-2.8 (ranging between 3 and 16). After superovulation animals with few follicles (Low group: or =8 follicles/day; n=23). No difference was found in the proportion of good quality embryos (relative to the total number; Low 0.68+/-0.11 versus High 0.79+/-0.08; P=0.21) between the two groups, or the recovery rate, the number of unfertilized oocytes or the number of poor quality embryos per animal. We conclude that ewes with a higher number of follicles (> or =8) during the first follicular wave had a better superovulatory response (in terms of corpora lutea and high quality embryos) 2-3 weeks later; however, there was no relationship between the number of follicles and the proportion of good quality embryos per animal
Early nutritional programming and progeny performance: Is reproductive success already set at birth?
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Comparison of ovarian follicles at follicle wave emergence between heifers with high versus low numbers of follicles
No full textComparison of ovarian follicles at follicle wave emergence between heifers with high versus low numbers of follicles
AE Zielak1, F Ward1, N Forde1, F Mossa1, P Lonergan1, JJ Ireland2, and ACO Evans1
School of Agriculture Food Science and Veterinary Medicine, University College Dublin, Belfield, Dublin 4, Ireland and 2Department of Animal Science, Michigan State University, East Lasting, Michigan 48824,USA (E-mail [email protected])
Introduction. Recent studies in cattle demonstrate that the numbers of antral follicles during follicular waves vary greatly among animals, but are highly repeatable within individuals. Although relatively high numbers of antral follicles are positively associated with fertility in numerous species, the causes and physiological significance of the high variation in follicle number during follicular waves in cattle is not known. The purpose of this study was to compare follicular fluid steroid concentrations, and mRNA levels for aromatase and LH and FSH receptors in follicles from heifers with low versus high numbers of follicles.
Materials and Methods. Cross-bread beef heifers (n=32) were synchronized with two injections of prostaglandin (PG) given 11 days apart. Ovarian follicle development was monitored on a daily basis in each heifer by transrectal ultrasonography. Heifers were then assigned into three groups based on the peak number of follicles (≥3 mm in diameter) per wave: Low (≤14 follicles, n=5), Intermediate (15≥26 follicles, n=22) or High (≥27 follicles, n=5). Animals in the Low and High group were slaughtered at emergence of the first follicle wave (12 to 24 hrs after ovulation). Pairs of ovaries were collected and weight. All follicles ≥3 mm were dissected from both ovaries and diameter was measured. Follicular fluid and granulosa and theca cells were isolated. Follicles were classified either individually within animal (F1 to F6 based on follicle diameter: when two follicles had the same diameter they were classified based on follicular fluid oestradiol concentrations) or in one of three size classes (4-4.5 mm, 5-5.5 mm and ≥6 mm). Oestradiol and progesterone concentrations in follicular fluid were measured by RIA and levels of mRNA were measured by Q-RT-PCR (and were expressed relative to β-Actin).
Results. Total weight of ovaries was greater (P0.05). The follicular fluid oestradiol concentrations of the largest (F1) and the second largest (F2) follicles were greater (P<0.05) in heifers with low versus high numbers of follicles (115.7±20.9 v 48.6±11.3; 106.1±18.6 v 40.5±10.3 ng/ml). Also heifers with low numbers of follicles had greater (P<0.05) E2:P4 ratio in the largest follicles than similar follicles in heifers with high number of follicles (4.8±1.0 v 2.3±0.9). Within different follicle size classes’ follicular fluid oestradiol concentrations were greater (P<0.05) in follicles ≥6 mm in diameter in heifers with low versus high numbers of follicles (105.3±15.9 v 41.2±10.2 ng/ml, n=10 v 7). The E2:P4 ratio was greater (P<0.05) in follicles in the 5-5.5 mm and ≥6 mm size classes in animals from the Low group compared to the High group (6.6±2.6 v 1.8±0.53, n=8 v 12; 4.0±0.7 v 1.9±0.6, n=10 v 7).
In granulosa cells, levels of mRNA for aromatase were greater (P0.05) between animals in the Low and High groups. In theca cells, mRNA levels for LH receptors were higher in the F2 (0.009±0.002 v 0.003±0.002) and F3 (0.005±0.001 v 0.014±0.004) follicles from heifers with low compared to high numbers of follicles, but there was no difference between F1 follicles (0.022±0.004 v 0.026±0.012).
Conclusion. We concluded that heifers with low numbers of ovarian follicles have smaller ovaries, and their follicles about the time of follicle wave emergence have higher follicular fluid oestradiol concentrations and more mRNA for the aromatase enzyme. The causes and significance of these differences remains to be established
Circulating electrolytes in the bloodstream of transition Sarda goats make the difference in body fluid distribution between single vs. twin gestation
No full textThe vitrification devices affect developmental competence and biochemical properties of IVM ovine oocytes
No full textRepeatability of antral follicle count during early gestation in dairy cattle
No full textIntroduction and Objectives. The number of ovarian antral follicles ≥3 mm in diameter (antral follicle count, AFC) in cattle is highly repeatable in individuals, while being highly variable among animals [1]. Furthermore, AFC is positively associated with ovarian function and fertility in cattle [2]. However, the mean numbers of follicles per month gradually decline from month 7 to month 9 of pregnancy [3]. The ability to phenotypically classify cows based on AFC with a single examination is highly desirable, hence the objective of this study was to investigate if AFC was influenced by pregnancy status and stage of gestation.
Materials and Methods. Transrectal ultrasonography of the reproductive tract was performed as part of the routine reproductive management in a commercial dairy farm on 47 pregnant dairy cows, aged from 1.3 to 4.9 years. Examinations took place before pregnancy establishment (on a random day of the cycle or at the time of artificial insemination, AI±5 days), on the day of pregnancy diagnosis (Day 27-39) and on the day fetal sex assessment (Day 58-68). Each ultrasonography was recorded and subsequently analyzed to determine AFC. The correlations between AFC during different stages of gestation and between AFC and age, parity, body condition score (BCS) were analyzed using ANOVA.
Results. Antral follicle count ranged from 5 to 39 with a mean (±SEM) of 13.21±1.02 and was not influenced by age, parity or days from calving; AFC was not related to pregnancy status, day of gestation or body condition score.
Conclusions. Antral follicle count is a phenotypic biomarker that can be reliably assessed during early gestation in cattle. Cows with high or low numbers of follicles can be reliably identified through transrectal ultrasonography performed on a single examination on a random day during the first trimester of gestation. The variation of AFC within animal during later stages of gestation remains to be determined.
References.
[1] Burns DS, Jimenez-Krassel F, Ireland JL, Knight PG, Ireland JJ. Numbers of antral follicles during follicular waves in cattle: evidence for high variation among animals, very high repeatability in individuals, and an inverse association with serum follicle-stimulating hormone concentrations. Biol Reprod. 2005;73:54-62.
[2] Ireland JJ, Smith GW, Scheetz D, Jimenez-Krassel F, Folger JK, Ireland JL, et al. Does size matter in females? An overview of the impact of the high variation in the ovarian reserve on ovarian function and fertility, utility of anti-Müllerian hormone as a diagnostic marker for fertility and causes of variation in the ovarian reserve in cattle. Reprod Fertil Dev. 2011;23:1-14.
[3] Ginther OJ, Kot K, Kulick LJ, Martin S, Wiltbank MC. Relationships between FSH and ovarian follicular waves during the last six months of pregnancy in cattle. J Reprod Fertil. 1996;108:271-9.
Acknowledments. Funded by the Italian Ministry of University and Research, Rita Levi Montalcini Grant 2010
Impact of a starch-rich maternal diet in pregnant ewes on body and testicular development in male offspring
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