Concentrations of Progesterone (P4), Anti-Müllerian Hormone (AMH), and Haptoglobin (Hp) in Pregnant and Non-Pregnant Ewes and Their Association with Fetal Mortality, Maternal Weight, and Twinning Rate

The study groups (n = 39) included ewes with ongoing pregnancy (P+; n = 19), with fetal death (FD; n = 12), and that were not pregnant (P-; n = 8). Blood samples were taken on days 10, 20, 30, 40, 60, 80, and 150 post-mating. Ultrasonography (USG) controls started on day 30. The P4 concentrations differed significantly between P+ and P- on all days (p < 0.001). Regarding AMH concentrations, a significant difference was observed between P+ and P- on day 30. P4 increased significantly from day 60 to 80 and remained elevated until day 150 in P+, while remaining basal in P-. In FD and P- groups, P4 reached its lowest concentrations. A rapid decrease in P4 was observed in P- from day 20 onwards. A statistically significant difference in P4 was also noted between P+ and FD. Additionally, P4 concentrations differed between singleton and twin pregnancies, especially on days 20 and 40. Statistically significant differences in AMH were found between P+ and FD on days 10, 20, and 30. In P+ sheep, P4, AMH, and Hp concentrations varied by season. A significant relationship was found between AMH and Hp concentrations and body weight. In conclusion, P4 stands out as the primary marker for distinguishing pregnancy status and detecting embryonic loss, while AMH provides complementary support, particularly in identifying fetal death. Seasonal changes were reflected across P4, AMH, and Hp concentrations, with AMH and Hp also showing significant associations with BW.

In utero heat stress compromises whole-body growth and mammary development from postweaning through puberty

Late-gestation in utero heat stress derails organ development and growth, leading to reduced first-lactation milk yield. Yet, carry-over effects of in utero heat stress on peripubertal heifers remain unexplored. This study investigated the long-term effects of in utero heat stress on body growth, mammary gland (MG) development, and ovarian function in peripubertal heifers. Dry, pregnant cows were housed in freestall barns and provided only shade or shade plus evaporative cooling for the last 54 ± 5 d of gestation during a subtropical summer. The resulting in utero cooled (IUCL, n = 21) and in utero heat-stressed heifers (IUHT, n = 19) were raised as a single cohort until 12 mo of age. Body weight, hip height (HH), chest girth (CG), body length (BL), withers height (WH), head circumference (HC), and MG macrostructure was recorded monthly from 3 to 12 mo. Once puberty was confirmed with 2 consecutive weeks of plasma progesterone (P4) concentrations >1 ng/mL, heifers were assigned to a protocol for the synchronization of estrus (D-7: GnRH + CIDR, D-2: PGF2α, D-1: PGF2α + CIDR removal). Blood and MG biopsies were collected on d 0 (high estradiol [E2]/low P4) and d 13 (low E2/high P4) to quantify mammogenic hormones and MG microstructure. Ovarian ultrasounds were conducted on d 0, 9, and 13 to analyze the cross-sectional area and volume of the dominant follicle and corpus luteum. Data were analyzed in SAS. A treatment by month interaction was observed for BW and CG, whereby IUHT heifers were lighter (3, 7, and 8 mo) and had smaller CG (3, 4, and 8 mo). Additionally, IUHT heifers had shorter HH (114.8 vs. 117.5 ± 0.6 cm; IUHT vs. IUCL), BL (100.6 vs. 102.2 ± 0.5 cm), and WH (108.3 vs. 110.4 ± 0.6 cm) and smaller HC (74.9 vs. 75.8 ± 0.3 cm). The distance between the teats and width of the MG did not differ, but teat lengths were shorter in IUHT heifers (front teats: 25.5 vs. 28.3 ± 0.6 mm; rear teats: 22.1 vs. 24.4 ± 0.6 mm). At 12 mo, MG length was shorter in IUHT than IUCL heifers (78.5 vs. 85.5 ± 1.4 cm). Fewer proliferating (0.38 vs. 0.85 ± 0.10%) and ERα-positive cells (10.1 vs. 12.8 ± 0.7%) were observed in IUHT heifers. In the MG fat pad, IUHT heifers had more adipocytes, particularly on d 13 (47.7 vs. 33.9 ± 3.3 cells). Although systemic P4 was similar, E2 concentrations were reduced in IUHT heifers on d 0 (3.8 vs. 5.0 ± 0.3 pg/mL). Additionally, IUHT heifers had a smaller follicle diameter and volume (diameter: 13.5 vs. 15.5 ± 0.6 mm; volume: 1,468.0 vs. 2,208.5 ± 262.0 mm3) and a smaller corpus luteum diameter and volume (diameter: 22.2 vs. 26.9 ± 0.7 mm; volume: 6,170.4 vs. 10,506.0 ± 617.7 mm3). Overall, exposure to in utero heat stress had lasting implications, leading to a disruption in the crosstalk between the MG and ovaries during the peripubertal phase. The observed effects during peripuberty may provide insight into the reduced lactation performance at maturity for in utero heat-stressed heifers.

Comparative Analysis of Anti-Müllerian Hormone Concentration in Two Indigenous Slovenian Sheep Breeds

Anti-Müllerian hormone (AMH), produced only by granulosa cells, is a biomarker for ovarian reserve in sheep. This study compared AMH levels in two Slovenian breeds: Istrska pramenka (IP), a seasonal breeder, and Jezersko-Solčava (JS), which reproduces year-round. Blood serum samples from 78 sheep were analyzed during the estrus period using an ovine AMH ELISA. JS sheep were grouped by age (1-3, 4-6, ≥ 7 years), while the majority of IP sheep were ≥7 years. AMH levels differed significantly between breeds (p < 0.001), with JS sheep showing higher concentrations. No age-related differences were found within the JS breed (p = 0.752), but JS sheep ≥ 7 years had higher AMH than IP sheep of the same age (p < 0.001). AMH levels were also higher in ewes lambing two lambs (p < 0.001) and were positively correlated with litter size, particularly in the JS sheep ≥ 7 years (p < 0.001). These findings suggest AMH is a useful fertility marker in sheep, although breed-specific reference values are essential for an accurate interpretation. The study highlights the influence of breed and age on AMH levels and its potential role in predicting reproductive performance.

Association of phenotypic traits and fertility in Holstein heifers: Body condition score, body weight, antral follicle count, anti-Müllerian hormone, and anogenital distance

The aim of this cross-sectional observational study was to assess whether nulliparous Holstein heifer fertility is associated with (1) energy reserve-related traits, such as BCS and BW; (2) ovarian reserve-related traits, such as anti-Müllerian hormone (AMH) and antral follicle count (AFC); and (3) development-related traits, such as anogenital distance (AGD) and vulval length (VUL). From August 2022 through July 2023, we used a prospective approach in which the phenotypic traits (BCS, AMH, AFC, AGD, BW, and VUL) of 698 Holstein heifers were measured once at approximately 12 mo of age (at the beginning of the breeding program). All heifers were submitted to the herd reproductive management from 367 ± 3 d of age and 297 kg of BW until 570 d of age, or 5 breedings. Fertility outcomes (age at first service, pregnancy per artificial insemination [P/AI] at first service, age at conception, and number of services per conception) were retrieved from software records. Pearson correlations were performed among phenotypic traits collected. The strongest correlations (r >0.5) observed were for AGD with VUL and AMH with AFC. Associations of phenotypic traits with fertility outcomes were determined using generalized linear models. Body condition score was the phenotypic trait most associated with fertility outcomes. Associations of AMH, AFC, AGD, BW, and VUL with fertility were not observed or were very weak. Furthermore, we divided the data into BCS tertiles and performed association analyses by category. The top BCS tertile was associated with greater BW (365.7 ± 1.8 vs. 356.0 ± 1.5 kg), greater P/AI at first service (65.0% ± 4.0% vs. 52.0% ± 4.0%), and fewer number of services per conception (1.5 ± 0.10 vs. 1.8 ± 0.09) compared with the bottom tertile. Moreover, AGD was greater in the top and bottom tertiles compared with the middle tertile. Finally, BCS was associated with time to conception based on the Cox proportional hazards survival analysis, indicating that heifers with greater BCS became pregnant earlier. Based on the results observed in the current study, we would expect benefits for fertility by improving management practices that result in heifers with greater BCS at first service, but ovarian reserve-related traits (AMH, AFC) and developmental traits (AGD, VUL) were not associated with fertility outcomes in our study.

Anti-mullerian hormone in felids: A systematic review

Anti-Müllerian hormone (AMH) is a dimeric glycoprotein that belongs to the transforming growth factor-β (TGF-β) superfamily. This hormone that is produced by gonadal Sertoli cells in males and granulosa cells in females has been extensively studied in humans, rodents, and livestock species. Research on AMH in felids began in 2011 and given the increasing number of studies over recent years, an updated literature review is necessary to clarify and organize future research directions. The objective of this article was to conduct a systematic review of AMH in domestic and wild felids. From a literature search of international publications, 23 were selected for inclusion. AMH determinations were performed using commercial enzyme-linked immunosorbent assays (ELISA) and electrochemiluminescence immunoassays (EQLIA). In female felids, AMH concentrations decrease with age, along with follicular reserve diminution. AMH can also be used to diagnose granulosa cell ovarian tumors and cryptorchidism in females and males, respectively. This hormone serves as a marker for reproductive status and can reflect gonadal function in both genders. Furthermore, AMH may prove to be a valuable predictive tool for reproductive biotechnologies in both domestic and wild felids. Several aspects of this hormone still remain to be elucidated, including its variations throughout the estrous cycle and the effect of photoperiod. Finally, standardization of assays and the establishment of reference ranges for both domestic and wild animals are necessary for widespread clinical application and future research development.

Transcriptomic analysis of heifers according to antral follicle count

While antral follicle count (AFC) has been associated with higher pregnancy rates, at present, our understanding of it as a reproductive parameter remains incomplete. This study aimed to characterize gene expression profile of oocytes from crossbred Bos taurus x Bos indicus heifers with high and low AFCs. Crossbred Nelore-Angus heifers (n = 50) with a mean (SD) age of 9.6 ± 0.55 months, a weight of 295.4 ± 32.6 kg, and a BCS of 3.44 ± 0.41 were studied in a feedlot system. The heifers received a hormonal protocol based on injectable progesterone and estradiol cypionate administered 12 days apart, and ovarian ultrasonography (US) was performed 12 days after to assess the AFC. Based on AFC, heifers were divided into low (≤14 follicles) and high (≥31 follicles) AFC, groups.Forty-five days after US, 14 heifers were slaughtered, and their ovaries were collected for morphological analysis and follicle aspiration. Cumulus-oocyte complexes (COCs) from the high and low AFC groups were graded according to their quality. Only best-quality COCs were stored for RNA-seq analysis. No differences were found in the presence or diameter of the dominant follicle and corpus luteum in the US, nor in the volume of the dominant follicle postmortem. The quantity of COCs recovered from high-AFC heifers was higher than that from low-AFC heifers (P < 0.05), and a tendency (P = 0.07) toward a higher amount of grade II COCs was observed. Thirty-two genes were differentially expressed between the groups, of which 30 were up-regulated and two down-regulated in the low AFC group. Among these, 22 % (7/32) were associated with fertility (CAB39, SLC2A6, CITED2, FDX1, HSD11B2, CD81, and PLA2G12B). Moreover, 9 and 2 exclusive genes were identified in the high and low AFC groups, respectively. Enrichment analyses showed that genes exclusive to oocytes from low-AFC heifers were associated with fundamental cellular processes, such as biosynthesis/biogenesis of ribosomes, peptides, amides, and nucleotides, and also with autophagy, mitophagy and mTOR signalling pathways.On the other hand, only one pathway was enriched in the high AFC group, but this cannot be related to the events studied No differences were observed in the ovarian structures after pre-synchronization of the estrus cycle of young Crossbred Nelore-Angus heifers. However, a tendency of a higher amount of grade II COCs was observed in heifers with high AFC than in those with low AFC. RNA sequencing results indicated that the main differences between high and low AFC heifers were not reflected in the genes directly related to fertility.

Depletion of Fkbp5 Protects Against the Rapid Decline in Ovarian Reserve Induced by Prenatal Stress in Female Offspring of Wild-Type Mice

Prenatal stress (PNS) impairs offspring ovarian development by exerting negative long-term effects on postnatal ovarian function and folliculogenesis. FKBP51 is a stress-responsive protein that inhibits glucocorticoid and progesterone receptors. We hypothesize that FKBP51 contributes to impaired ovarian development and folliculogenesis induced by PNS. Timed-pregnant Fkbp5+/+ (wild-type) and Fkbp5-/- (knockout) mice were randomly assigned to either the undisturbed (nonstress) or PNS group, with exposure to maternal restraint stress from embryonic days 8 to 18. Ovaries from the offspring were harvested and stained, and follicles were counted according to their stages. Ovarian expressions of FKBP51 were evaluated by immunohistochemistry and Fkbp5 and steroidogenic enzymes were evaluated by qPCR. Compared to controls, Fkbp5+/+ PNS offspring had increased peripubertal primordial follicle atresia and fewer total follicles in the adult and middle-aged groups. In adult Fkbp5+/+ offspring, PNS elevated FKBP51 levels in granulosa cells of primary to tertiary follicles. Our results suggest that PNS administration increased FKBP51 levels, depleted the ovarian reserve, and dysregulated ovarian steroid synthesis. However, these PNS effects were tolerated in Fkbp5-/- mice, supporting the conclusion that FKBP51 contributes to reduced ovarian reserve induced by PNS.

Beef cows with larger vulvar width have greater antral follicle count, viable oocytes, and higher circulating AMH

Owing to the low heritability of reproductive traits, the search for markers and their interrelationship that could indicate reproductively superior individuals is important in the selection process for bovine reproductive efficiency. This study aimed to investigate the possible interrelationships between the antral follicle count (AFC), vulvar-width (VW), anti-Müllerian hormone (AMH) concentrations, fertility in Bos Taurus and Bos Indicus females. Brahman (Bos Taurus-Indicus, n = 126) and Simmental and Angus (Bos Taurus-Taurus, n = 155) cows were classified as having large (≥86 mm) and small (<86 mm) VW. From each group, one blood sample per animal was collected to determine the AMH serum concentrations. The GLIMMIX procedure in SAS® was used to determine whether vulva width (VW) and AMH classes, associated or not with breed, could influence the age at first calving (FCA), calving to first service interval (CFSI), calving interval (CI), number of services per pregnancy (SP), and number of viable oocytes (VO). Antral follicle count (AFC) (36.10 ± 1.90 vs. 22.78 ± 1.64, for large and small VW, respectively), AMH (1.17 ± 0.07 vs. 0.48 ± 0.007 ng/mL), and viable oocytes or VO (18.86 ± 1.76 vs. 10.15 ± 1.49) were greater (P < 0.05) in the large VW than in the small VW. Brahman cows had greater AFC (36.30 ± 1.34 vs. 22.09 ± 1.67), VW (106.94 ± 15.83 vs. 69.78 ± 14.11 mm), and AMH (1.18 ± 0.07 vs. 0.42 ± 0.05 ng/mL) compared to that of taurine cows. In conclusion, VW was an efficient predictor of AFC and AMH concentrations in both genetic groups, but under the conditions of this trial no link could be detected between these variables and the reproductive indices studied.

Unraveling the Clinical FSH Conundrum: Insights From the Small Ovarian Reserve Heifer Model

High doses of follicle stimulating hormone (FSH) are used during ovarian stimulation to maximize the number of oocytes recovered for in vitro fertilization (IVF) during assisted reproductive technology (ART) in women. Whether high FSH doses are detrimental to embryo viability remains controversial. Evidence from many clinical studies revealed that FSH dose is inversely correlated with live birth rate in women. The mechanistic basis for this effect has been elusive. This review summarizes over 20 years of work using a unique biomedical model, the small ovarian reserve heifer (SORH). Those studies revealed that excessive FSH doses can disrupt gene expression via multiple cell-signaling pathways in ovarian cells, resulting in follicular hyperstimulation dysgenesis (FHD). This compromises the capacity of ovulatory-size follicles to respond to gonadotropins, produce estradiol and ovulate, causes premature cumulus expansion and oocyte maturation, and impairs the fertilizability of oocytes. The SORH model has thus provided new insights into the nature and mechanisms of the deleterious effects of excessive FSH doses during ovarian stimulation. The SORH model has been and remains valuable for basic research and for the discovery of ways to optimize FSH dosing clinically to improve IVF success and ART outcomes.

Folicular dynamics, endocrine profiles and endometrial gene expression in fertile and subfertile cows

Context Subfertility has a negative impact on the productivity of beef cow herds; thus, it is relevant to unravel the mechanisms. Aims To study follicular development, body composition, concentrations of progesterone and metabolic hormones and their gene expression in the endometrium during the oestrus cycle. Methods Fertile and subfertile Hereford cows were classified at 25 (n =84) and 60 (n =25) months old, as (1) fertile, pregnant at first insemination at 25months, that became pregnantmore than three of five times at 60months (n =5), or (2) subfertile, i.e. failed to became pregnant during three inseminations at 25months, that became pregnant at fewer than two of the five opportunities at 60months (n =6). Key results Fertile cows had greater concentrations of insuling-like growth factor 1 (IGF-1), leptin and adiponectin (P P P P P Conclusions Differences in progesterone and metabolic hormones in plasma and follicular fluid and their endometrial expression are associated with the success of pregnancy in beef cows. Implications Strategies to improve the follicle and endometrial microenvironments are needed to improve the productivity of beef herds.

Anti-Müllerian Hormone Concentrations Can Be Reliably Determined by a Single Measurement, Irrespective of Cycle, in Synchronised Ewes During Non-Breeding Season

Improvement of yield characteristics in animal breeding is important in terms of increasing animal production and sustainability. Fertility is one of the most important yield traits affecting economic gain in sheep breeding. Anti-Müllerian Hormone (AMH) is widely recognised as a dependable biomarker for assessing ovarian reserves and fertility potential. The aim of this study was to evaluate the dynamics of AMH during different phases of the sexual cycle in Norduz ewes the non-breeding season. Additionally, the study sought to assess the effects of age and body condition score (BCS) on AMH concentrations during these phases. A total of 32 Norduz ewes with a body condition score (BCS) of 3-4.5 and aged between 2 and 4 years were used as animal material in the study. All experimental procedures were carried out outside the breeding season and when the ewes were lactating. In all ewes in anestrus, intravaginal sponges (Esponjavet, 60 mg MAP, Hipra, Turkey) were kept in the vagina for 7 days for estrus synchronisation. Intramuscular injections of PMSG (Oviser, 500 IU, Hipra, Turkey) and PGF2α analog (Gestavet, 50 μg, Hipra, Turkey) were administered 48 h prior to sponge removal. Twenty-four hours after sponge removal, ewes were exposed to the ram for estrus detection. Since 5 ewes did not show estrus, blood samples were collected regularly from animals (n = 27) in which estrus was detected at three different stages: one just before the insertion of vaginal sponges (anestrus), another when heat was detected exposing to the ram (estrus), and the final one 10 days after estrus (diestrus). The serum samples were assessed for the levels of AMH and progesterone through the electrochemiluminessence immunoassay technique (ECLIA). The results of the analyses showed that serum AMH concentration did not vary between anestrus, estrus and diestrus phases of the sexual cycle of Norduz ewes outside the breeding season (p > 0.05). Furthermore, age and BCS had no effect on progesterone and AMH levels in different phases of the sexual cycle (p > 0.05). In conclusion, this study shows that serum AMH levels are constant at any stage of the estrus cycle. This suggests that phenotypic evaluation of ewes can be performed with a single measurement and that AMH is a reproducible and dependable biomarker that can be measured at any stage of the estrus cycle at an arbitrary time point.

Delayed endometrial preparation for the induction of luteolysis as a potential factor for improved reproductive performance in Angus beef heifers with high antral follicle counts†

Antral follicle count (AFC) and anti-Müllerian hormone (AMH) concentrations are reflective for ovarian reserve and have been associated with improved reproductive performance in cattle. Key events for regulation of uterine receptivity are orchestrated by progesterone. As progesterone concentrations are greater in animals with high than low AFC, we tested the hypothesis, if the resulting improved uterine environment will lead to improved conceptus elongation and endometrial response to interferon tau. For four years, 10 heifers with lowest and highest AFC, respectively, were selected from 120 heifers. Reproductive tracts and blood samples for progesterone and AMH analysis were collected after synchronization and insemination. For a recovered conceptus, length was determined, and interferon tau (IFNT) transcript abundance was analyzed. Endometrial transcript abundance of interferon-stimulated gene 15 (ISG15) and oxytocin receptor (OXTR) were analyzed. Progesterone concentrations did not differ between low and high AFC groups (P = 0.1). A difference in conceptus length was not observed. Endometrial abundance of ISG15 did not differ between pregnant low and high AFC heifers. Abundance of OXTR was greater in open low AFC than open high AFC heifers (P < 0.01). Interaction of AMH and pregnancy status was determined, with greater AMH in pregnant than open high AFC heifers (P < 0.05). Improved uterine environment in high vs. low AFC heifers did not result in longer conceptuses or improved endometrial response. As the increase in OXTR transcript abundance was only detected in low AFC heifers, reported differences in reproductive performance might be associated with earlier initiation of luteolysis.

Effect of maternal heat stress at different stages of pregnancy on the reproductive performance and antral follicle count of the progeny of Holstein cows

The objective was to evaluate the effect of maternal exposure to heat stress conditions at different stages of pregnancy on the reproductive performance and antral follicle count of progeny. The study was conducted at five commercial dairy farms located in southeastern Brazil. Retrospective data (2002 and 2015) on reproductive indices of daughters of Holstein cows that were exposed to heat stress conditions in the first (n = 447), second (n = 729) or third (n = 746) trimester of pregnancy and daughters of cows not exposed to heat stress (n = 359) were analyzed. Antral follicle count (AFC) and ovarian size were determined in a subgroup of animals (n = 242) by transrectal ultrasound. Statistical analysis was performed using the SAS GLIMMIX procedure. The number of services after first calving was lower in daughters of cows not exposed to heat stress conditions than in those exposed during different trimesters of pregnancy (P = 0.03). The calving interval was longer for daughters of cows exposed to heat stress conditions in the second and third trimesters of pregnancy than for those not exposed to heat stress (P = 0.01). In addition, the probability of pregnancy at first AI, (P = 0.01) and the AFC (P = 0.001) were greater in daughters of cows not exposed to heat stress conditions than in those exposed during the different phases of the gestational period. These findings indicate that maternal heat stress in different stages of pregnancy negatively affect the future fertility and AFC of bovine offspring.

Effects of Intrauterine Isoproterenol Administration on Ovarian Follicular Development in Cows

BACKGROUND

Isoproterenol (ISO) is a nonselective beta-adrenergic receptor agonist known for its vasodilatory effects. This experiment aims to investigate whether intrauterine ISO administration could alter vascular indices and follicular development in postpartum Holstein cows.

OBJECTIVES

The objectives are to evaluate the effects of intrauterine ISO administration on vascular changes and its impact on follicular development compared to placebo groups.

STUDY DESIGN

This randomized controlled study was conducted on 36 Holstein cows selected based on their health status, including only those free from reproductive, metabolic and infectious disorders.

METHODS

The cows (n = 36) were divided into two groups as control received distilled water alone (CON, n = 18) and experiment received 4 mg ISO in 40 mL distilled water (ISO, n = 18) and four subgroups as CON-I (n = 9), CON-II (n = 9), ISO-I (n = 9) and ISO-II (n = 9) according to days of intrauterine administration (I or II represents to 1 or 2 days after ovulation, respectively). Uterine and ovarian artery blood flows were assessed before and after administration by Doppler ultrasonography. Blood samples were collected both before and after administration (on Day 1 or 2) and on Days 3, 6 and 9 post-ovulation for hormonal analysis. Antral follicle count (AFC) was recorded on the blood sampling days. Data were analysed via mixed model ANOVA.

RESULTS

Intrauterine ISO administration significantly increased the pulse rate (PR) in the ovaries (89.4 vs. 65.5 bpm, p < 0.0001) and uterus (90.6 vs. 64.2 bpm, p < 0.0001). Early AFC (1-2.9 mm) decreased, whereas small AFC (3-4.9 mm) increased in the ISO groups. The weighted average antral follicle size (WAAFS) significantly increased in the ISO group but remained unchanged in the controls. Hormonal analysis revealed elevated levels of FSH (626 vs. 468 mIU/mL), AMH (61.3 vs. 46.4 ng/L), E2 (138 vs. 122 ng/L), P4 (15.3 vs. 10.6 ng/mL), IGF-1 (62.6 vs. 25.1 ng/mL) and IGFBP-3 (28.4 vs. 16.5 ng/mL) in the ISO groups (p < 0.0001).

CONCLUSIONS

The findings indicate that intrauterine administration of ISO on Day 1 post-ovulation could be a promising 'adjunct technique' for future research focussed on minimizing dependence on exogenous hormones or improving the sensitivity of follicles to endogenous hormonal signals, thereby potentially enhancing oocyte yield.

Assessment of anti-Müllerian hormone levels as a reproductive indicator in Japanese Black cattle

The size of the ovarian reserve, an indicator of the number of primordial follicles, varies widely among individuals, and declines with age. However, the association between the ovarian reserve and fertility remains unclear. Therefore, in the present study, we analyzed the relationship between plasma concentrations of anti-Müllerian hormone (AMH), a marker of ovarian reserve, and reproductive outcomes in Japanese Black cattle. AMH level quartiles were positively associated with pregnancy following artificial insemination (AI), and the median number of days to pregnancy in Q4 (13 days, 95% confidence interval [CI] = 7-18 days) was significantly shorter than that in Q1 (21 days, 95% CI = 15-46 days). The odds ratio for the predicted pregnancy rate by logistic regression analysis in Q4 (4.06, 95% CI = 1.54-10.67) was also significantly higher than that in Q1. Plasma AMH concentrations were significantly higher in summer (June-August) than in winter (December-February). Furthermore, a strong correlation (r = 0.856, P < 0.001) was observed between plasma AMH concentrations at 2 and 14 months of age. Calves with plasma AMH concentrations of > 700 pg/ml at 2 months old showed a transient increase and maximum AMH concentration within 5 months of birth. Overall, the results of this study indicate that the plasma AMH concentration serves as a predictive marker for the probability of conception following AI in Japanese Black cattle. The current findings contribute to the reliable assessment of AMH production and the early prediction of reproductive performance in sexually mature heifers.

Transcriptomic analysis of luteal tissue supports the earlier onset of luteolysis in heifers with diminished ovarian reserve

Context Antral follicle count (AFC) is reflective of ovarian reserve and linked to reproductive performance in mammalian females. We previously demonstrated earlier upregulation of endometrial oxytocin receptor transcription in heifers with low AFC, indicating an earlier onset of luteolysis. Aims We aimed to support the earlier onset of luteolysis in non-pregnant heifers with a low number of antral ovarian follicles (Open Low AFC) and hypothesized a reduced abundance of luteinizing hormone/choriogonadotropin receptor (LH/CG-R ) and increased abundance of thrombospondin-1 (THBS1 ) in luteal tissue of those heifers. We further investigated if classical interferon stimulated genes (ISGs) are already upregulated in response to conceptus-derived interferon tau. Methods For 4years, 10 heifers with the highest (High AFC) and 10 heifers with the lowest AFC (Low AFC) of the population (n =120/year) were selected, synchronized and inseminated. On day 15 or 16 after insemination, reproductive tracts were collected, and pregnancy status was determined. Corpora lutea were isolated, weighed and underwent transcriptomic analysis. Key results Transcript abundance of LH/CG-R was lower in Open Low AFC heifers compared to all other subgroups. Transcript abundance of THBS1 was upregulated in Open vs Pregnant heifers and showed greater abundance in Low vs High AFC heifers. Luteal weights and abundance of ISGs did not differ between heifers of differing AFC groups or pregnancy status. Conclusions The patterns of luteal LH /CG-R and THBS1 abundance support the concept of earlier onset of luteolysis in Open heifers with diminished AFC. Implications This may result in a shorter window for maternal recognition of pregnancy and contribute to inferior reproductive performance.

The impact of enhanced early postnatal nutrition on the histomorphological features of the ovaries in fat-tailed Sanjabi ewe lambs

This study aimed to investigate whether providing additional ad libitum feeding could improve reproductive characteristics in prepubertal ewe lambs. Twelve Sanjabi ewe lambs, approximately one-month-old and with an average initial weight of 11.6 ± 1.3 kg, were monitored over a 3-month period, which was divided into three distinct periods of 30 days each. The first period spanned from the lambs' age of one to two months, the second period covered their age range of two to three months, and the third period encompassed their age range of three to four months. The lambs were randomly assigned to either a control group (C) or a treatment group (T). The control group received a basal diet consisting of hay and milk, whereas the treatment group received an enhanced diet comprising hay, milk, and concentrate. Live weight (LW) and average daily gain (ADG) were measured weekly, and blood samples were collected from the jugular vein at days 30, 60, and 90 of the experiment to determine the concentrations of progesterone (P4) and estrogen (E2). Following the 90-day experiment, the lambs were humanely euthanized in accordance with established protocols. Subsequently, both ovaries from each animal were removed, weighed and subjected to a comprehensive histological analysis. The ovaries underwent fixation, embedding, and sectioning procedures, followed by staining with hematoxylin and eosin (H&E) to facilitate microscopic examination. Ovary microscopic sections from both C and T groups were examined to assess follicles at various developmental stages, including primordial follicle number (PreFN) and diameter (PriFD), primary follicle number (PriFN) and diameter (PriFD), secondary follicle number (SFN) and diameter (SFD), antral follicle number (AFN) and diameter (AFD), and granulosa layer thickness of secondary (GLTSF) and antral follicles (GLTAF). The impact of diet and three experimental periods on ADG and LW exhibited significant variations. There was a significant increase (P < 0.05) in LW in the T group compared to the T group, with noticeable differences in LW fluctuations observed during distinct periods. However, ADG was more prominent in the initial and second observation periods than in the third. The impact of diet and experimental periods on P4 and E2 concentrations was found to be negligible. The T group showed significant improvements (P < 0.05) in PreFD, PriFN, and GLTAF compared to the C group. This study suggests that ad libitum concentrate feeding may promote reproductive characteristics in prepubertal ewe lambs. Further research is needed to explore its potential impact on the age of puberty.

Relationship between plasma anti-Müllerian hormone concentrations in female Holstein calves immediately after birth and milk yield and composition in dams during early to mid gestation

The energy status of dams during the early stages of gestation may affect ovarian reserves. It was hypothesized that greater milk yield and composition during the early stages of gestation may suppress the number of primordial follicles in the fetuses of dairy cattle. This study aimed to evaluate the anti-Müllerian hormone (AMH), used as an indicator of ovarian reserves, in female Holstein calves immediately after birth. It also examined the relationship between AMH concentrations and the milk yield and composition of dams during early pregnancy. A total of 85 female Holstein calves (born to first-calving cows [nulliparous heifers], n = 31; second-calving [primiparous] cows, n = 22; and third- or subsequent-calving [multiparous] cows, n = 32) were examined. Blood samples were collected from the female calves after birth and before the first colostrum feeding for the analysis of plasma AMH concentrations. Data on daily milk yield and monthly milk composition during the first to sixth month of pregnancy were additionally collected from milking dams. The plasma AMH concentrations ranged from 0.106 to 1,542.3 pg/mL, with an average of 291.6 ± 30.5 pg/mL. No significant differences were observed among the plasma AMH concentrations in female calves born from nulliparous heifers, primiparous cows, or multiparous cows. Primiparous cows exhibited numerous negative correlations between the plasma AMH concentrations of their female calves immediately after birth and the daily milk yield and milk composition from the first to the fourth month of pregnancy; however, no correlation was observed in multiparous cows. Overall, large individual variations were observed in the plasma AMH concentrations immediately after birth. Both milk yield and the amount of milk components strongly influenced plasma AMH concentrations in calves immediately after birth in primiparous cows in the growth phase. These factors, conversely, did not affect the plasma AMH concentrations of calves in multiparous cows. The results of this study suggest that high-producing pregnant primiparous cows devote more energy to their growth and lactation, potentially compromising the reproductive potential of their offspring. Thus, improving the feeding management of primiparous cows with the goal of increasing the fertility of their progeny will help high-yielding dairy cows reproduce more successfully.

Impact of antral follicle count on follicular-luteal characteristics, superovulatory response, and embryo quality in Sahiwal cows

The study aimed to evaluate the effect of antral follicle count (AFC) on follicular and luteal development during the estrous cycle and superovulatory period, as well as on superovulatory response and in vivo embryo quality within the MOET program. A total of 48 estrus-induced (500 μg PGF2α, Single dose, IM) Sahiwal cows (Bos indicus) with a BCS between 3.5 and 4.0 were selected for the study. On the day of wave emergence, the animals were divided into two groups based on the AFC, i.e., low AFC (≤18) and high AFC (>18). Both the groups were monitored daily using B-mode ultrasonography (USG) for one cycle, and the superovulation protocol was initiated on the 9th day of the subsequent estrous cycle. A total of 240 μg of FSH in eight divided doses were given in a tapering sequence for 4 days and simultaneous administration of 500 μg PGF2α, along with the fifth dose of FSH. Donors were inseminated at superovulatory estrus using double straws of high-quality frozen semen thrice at 12-h intervals, and non-surgical flushing was performed on day 7 of the superovulatory estrus followed by embryo searching and evaluation under a stereo zoom microscope. Ovulatory waves of the high-AFC Sahiwal cows have significantly (p ≤ 0.05) larger sizes of preovulatory follicles (POF) (12.06 ± 0.19 mm vs 11.56 ± 0.16 mm) and corpus luteum (CL) (19.57 ± 0.28 mm vs 18.26 ± 0.35 mm), as compared to low AFC. The ovarian size was significantly (p < 0.0001) larger in cows with high AFC during the superovulatory protocol. The number of large, medium, and small follicles was significantly (p < 0.0001) high on the day of superovulatory estrus (SOE), PGF2α administration, and initiation of superovulatory protocol, respectively, in high AFC. Donors with high AFC had a notably greater (p < 0.0001) count of CL and embryos retrieved per flushing, including excellent and fair-quality embryos. A strong association (p < 0.0001) between high AFC and ovarian size (r = 0.9136), superovulatory response (r = 0.9350), and embryo quality (x2 = 8.788; p = 0.032) and number (r = 0.9858) were also recorded. Based on these results, AFC is considered a dependable indicator for forecasting reproductive capacity. Bos indicus donors with an average AFC of 30 or higher are recommended.

Evaluation of Anogenital Distance and Anti-Müllerian Hormone Plasmatic Concentration as Potential Phenotypes to Predict Reproductive Performance in Holstein Heifers

Anogenital distance (AGD) is a marker of the degree of prenatal exposure to androgens in multiple species, and it has been suggested that there is an inverse association between AGD and fertility. Therefore, the aim of this study was to determine the usefulness of AGD and anti-Müllerian hormone (AMH) concentrations, an indirect marker of the follicular population, as predictors of future reproductive potential in Holstein cattle. The AGD was measured in 566 females from 9 dairy farms in Galicia (Spain). A group of 172 females underwent a second measurement 9 months after. Additionally, data on the age at first insemination (1stAI age), number of AI (AI-PREG), age at first pregnancy (1stPREG age), age at first calving (1stCAL age), and calving-pregnancy (CAL-PREG) and calving-calving (CAL-CAL) intervals were collected. Blood samples were collected from 80 heifers to determine AMH concentrations. Our results showed that AGD varied minimally with age, and that cows with short AGD had earlier 1stAI age, 1stPREG age, and 1stCAL age (p < 0.05) than cows with long AGD. No significant differences were observed for the CAL-PREG and CAL-CAL intervals. Additionally, no significant association was found between AMH concentration and AGD or reproductive parameters. Consequently, the results suggest the possibility of using AGD as a marker of future reproductive performance in Holstein heifers. However, there was insufficient evidence to associate AMH concentrations and reproductive performance, underlining the need for further studies with larger sample sizes.

Expression and localization of anti-Müllerian hormone and its receptors in bovine corpus luteum

Although anti-Müllerian hormone (AMH) is involved in the regulation of granulosa cell function in female animals, its role in tissues other than ovarian follicles remains poorly understood. It has also been suggested that cows with high circulating AMH concentrations have increased fertility; however, the mechanism has not been elucidated. This study was conducted to identify the presence of the AMH-signaling system and its target cells in the bovine corpus luteum formed from an ovulated follicle. Immunoblotting revealed that the proteolytically cleaved C-terminal region in AMH (AMHC), a biologically active peptide, was present in trace amounts in the early corpus luteum and significantly increased during the mid to regressed stages. AMHC and cleaved N-terminal region (AMHN) in AMH generate a noncovalent isoform that improves the activity of AMH signaling. An immunohistochemical analysis revealed that AMHC, AMHN, and type II AMH receptor (AMHR2) were localized to luteal cells during the entire estrous cycle. AMH in the corpus luteum seemed to be newly synthesized since AMH expression was detected. These findings suggest that AMH signaling is involved in the regulation of luteal cell function through an autocrine and post-translational processing mechanism. The level of AMHR2 and mRNA expression of AMHR2 and type I AMH receptors (activin-like kinase 2, 3, and 6) were highest in the mid stage. Thus, AMH signaling in the corpus luteum may also be regulated by changes in the receptor levels. Since the transforming growth factor-beta superfamily, to which AMH belongs, is a multifunctional polypeptide growth factor, further studies are needed to evaluate whether AMH signaling has a role in facilitating or inhibiting luteal cell functions.

Serum anti-Müllerian hormone is an indirect predictor of ovarian reserve in domestic cats

Anti-Müllerian hormone (AMH) serves as an indirect marker for predicting primordial follicles that are representative of ovarian reserve. In this study the possibility of using AMH and age to predict the ovarian reserve in domestic cats. Ovaries and blood were collected from 30 cats undergoing routine ovariohysterectomy. The animals were divided into three age groups: prepubertal (<4 mo, n = 10), adult (1-5 y, n = 10), and senior (>5 y, n = 10). Blood was collected at surgery for serum AMH measurements using the AMH Gen II ELISA kit. The intra-assay coefficient of variation (CV) and inter-assay CV were 3.56 % and 7.68 %, respectively. One side of the ovary was processed to determine AMH localization using immunohistochemistry and for a histological count of follicles, which is the gold standard. The expression of AMH protein was quantified from the contralateral ovary by Western blot analysis. Primordial follicles exhibited the most pronounced inverse relationship with age (rho = -0.779, P < 0.05), followed by a positive association with serum AMH concentration (rho = 0.490, P < 0.05), indicating that both age and AMH are potential markers indicative of primordial follicles. Furthermore, secondary (rho = 0.651, P < 0.05) and small antral follicles (rho = 0.648, P < 0.05) were identified as the major sources of circulating AMH, as indicated by the stronger correlation with serum AMH concentrations compared with primary follicles. However, there was no significant correlation between the expression of AMH protein and other factors, including age, primordial follicles, primary follicles, secondary follicles, small antral follicles, and serum AMH concentration. A model for predicting primordial follicle number using serum AMH concentration (AIC = 672.66, P < 0.05) and age (AIC = 668.93, P < 0.05) was established. In conclusion, both serum AMH concentration and age may serve as comparable markers of ovarian reserve in domestic cats. Moreover, AMH is particularly useful in situations where age information is not available.

Puberty in beef heifers: effects of prenatal and postnatal nutrition on the development of the neuroendocrine axis

Reproductive maturation is a complex physiological process controlled by the neuroendocrine system and is characterized by an increase in gonadotropin-releasing hormone (GnRH) and luteinizing hormone (LH) pulsatile secretion. Nutrition during early development is a key factor regulating puberty onset, which is defined as first ovulation in females. In heifers, nutrient restriction after weaning delays puberty, whereas elevated levels of nutrition and energy reserves advance reproductive maturation. Recent studies in cattle and other animal models have shown that the dam's nutrition during gestation can also program the neuroendocrine system in the developing fetus and has the potential to alter timing of puberty in the offspring. Among the metabolic signals that modulate brain development and control timing of puberty is leptin, a hormone produced primarily by adipocytes that communicates energy status to the brain. Leptin acts within the arcuate nucleus of the hypothalamus to regulate GnRH secretion via an upstream network of neurons that includes neurons that express neuropeptide Y (NPY), an orexigenic peptide with inhibitory effects on GnRH secretion, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide with excitatory effects on GnRH neurons. Another important population of neurons are KNDy neurons, neurons in the arcuate nucleus that co-express the neuropeptides kisspeptin, neurokinin B, and dynorphin and have strong stimulatory effects on GnRH secretion. Our studies in beef heifers indicate that increased nutrition between 4 to 8 months of age advances puberty by diminishing NPY inhibitory tone and by increasing excitatory inputs of αMSH and kisspeptin, which collectively lead to increased GnRH/LH pulsatility. Our ongoing studies indicate that different planes of nutrition during gestation can alter maternal leptin concentrations and promote changes in the fetal brain. Nonetheless, at least in Bos indicus-influenced heifers, deficits programmed prenatally can be overcome by adequate postnatal nutrition without negatively impacting age at puberty or subsequent fertility.

Selecting oocyte donors based on anti-Müllerian hormone (AMH) concentrations: A critical analysis of using cutoff values as exclusion criterion for an in vitro embryo production program in Gir cattle

The aims of this study were to determine anti-müllerian hormone (AMH) cutoff values for selecting Gir (Bos taurus indicus) oocyte donors and estimate the impact of using AMH concentrations as a selection criterion. In Exp. 1, Gir heifers (n=120) were sampled for AMH analysis and submitted to ovum pick-up and in vitro embryo production (OPU-IVEP). AMH cutoff values were calculated using ROC analysis or, alternatively, by the successive exclusion of heifers with the lowest AMH values. The correlations between AMH and OPU-IVEP outcomes were significant (P<0.001), though low or moderate (r= 0.34-0.52). We estimated an improvement (P<0.05) after the use of AMH cutoff values to select donors of +15.3% for total oocyes, +19.4% for viable COC, and +23.4% for blastocysts. This selection pressure, however, led to the exclusion of 32.8%, 37.9%, and 50.0% of the initial potential donors, respectively. In Exp. 2, we analyzed data from OPU-IVEP sessions of 658 Gir donors with known genomic values for predicted transmitting ability for milk (GPTAm) and age at first calving (GPTAafc). The selection based on the number of oocytes recovered had no effect (P>0.05) on the average GPTAm nor GPTAafc values of the remaining donors. In summary, plasma AMH ≥700 pg/mL is a cutoff value that can be used to select Gir heifers with a greater potential as oocyte donors. Nevertheless, this selection leads to the exclusion of up to 50% of potential donors. Finally, exclusion of poor responders had no effect on mean genomic estimates for milk production or age at first calving in the selected subset of donors.

Elecsys® AMH assay: Determination of Anti-Müllerian hormone levels and evaluation of the relationship between superovulation response in Holstein dairy cows

BACKGROUND

Anti-Müllerian Hormone (AMH) serves as a crucial parameter in assessing the reproductive herd life and ovarian reserve in cattle. Consequently, extensive research is conducted on AMH levels. Various measurement methods can be employed to determine AMH levels. However, to our knowledge, no study has been conducted on Holstein donors using the Elecsys® AMH kit.

OBJECTIVE

This study was designed to determine AMH levels in donors utilising the Elecsys® AMH kit and to evaluate the relationship between superovulation response parameters and AMH levels.

METHODS

In this study, we measured the serum AMH levels of 36 cows using the Elecsys® AMH automated assay before the superovulation protocol (1st sample) and FSH injections (2nd sample). The cows were categorised into three groups based on their AMH levels: low, medium, and high AMH.

RESULTS

Positive correlations were identified between AMH and parameters associated with superovulation response. The high AMH level group exhibited significantly greater numbers of corpus luteum, total embryos, transferable embryos, and grade 1 embryos compared to the medium and low AMH groups (p < 0.05) There was no significant difference between AMH levels before the superovulation protocol and FSH injections(p > 0.05). Body condition score and parity did not significantly affect AMH levels in cows (p > 0.05). Also, AMH cut-off values for the number of corpus luteum, total embryo, and transferable embryos were detected as 234, 227, and 210 pg/mL, respectively.

CONCLUSION

These findings demonstrate that a high serum AMH level has a positive influence on the superovulation response. AMH can be used as a reliable marker for the selection of donors in Holstein cows.

Effect of serum anti-Müllerian hormone levels on the superovulation response in Holstein heifers

BACKGROUND

Anti-Müllerian hormone (AMH) holds potential as a biomarker for assessing the superovulation (SO) response in cattle. Nonetheless, there exists scant information regarding this aspect in the literature concerning dairy heifers. Given this gap, our objective is to explore the viability of AMH as an indicator for gauging the SO response specifically in Holstein heifers. Furthermore, our aim encompasses examining the variations in AMH levels within the same individuals before and after undergoing SO.

METHODS

The study included 41 Holstein heifers. All heifers were superovulated and blood samples were taken both before and after the SO protocol.

RESULTS

The findings revealed that the mean values of serum AMH concentrations before and after SO were 0.122 ng/mL (0.093-0.248 ng/mL) and 0.119 ng/mL (0.084-0.170 ng/mL), respectively. AMH concentrations in heifers were stratified into low (<0.106 ng/mL), medium (0.107-0.126 ng/mL) and high (>0.127 ng/mL) categories both before and after SO.

CONCLUSIONS

There was no significant correlation between AMH levels in the heifers both before and after SO treatment with the number of follicles, corpora lutea, total embryos collected or embryos transferred (p > 0.05). Furthermore, this study showed that serum AMH concentrations in Holstein heifers did not change after SO treatment. In this study, as AMH levels in Holstein heifers were in a narrow range, a relationship between AMH and SO response could not be determined. In future studies, we believe that it would be more useful to plan more studies in Holstein donor heifers, taking into account the number of animals and AMH levels.

Developmental programming of production and reproduction in dairy cows: IV. Association of maternal milk fat and protein percentage and milk fat to protein ratio with offspring's birth weight, survival, productive and reproductive performance and AMH concentration from birth to the first lactation period

Although the association of maternal milk production with developmental programming of offspring has been investigated, there is limited information available on the relationship of maternal milk components with productive and reproductive performance of the offspring. Therefore, the present study was conducted to analyze the association of maternal milk fat and protein percentage and milk fat to protein ratio with birth weight, survival, productive and reproductive performance and AMH concentration in the offspring. In study I, data of birth weight, milk yield and reproductive variables of offspring born to lactating dams (n = 14,582) and data associated with average maternal milk fat percentage (MFP), protein percentage (MPP) and fat to protein ratio (MFPR) during 305-day lactation were retrieved. Afterwards, offspring were classified in various categories of MFP, MPP and MFPR. In study II, blood samples (n = 339) were collected from offspring in various categories of MFP, MPP and MFPR for measurement of serum AMH. Maternal milk fat percentage was positively associated with birth weight and average percentage of milk fat (APMF) and protein (APMP) and milk fat to protein ratio (FPR) during the first lactation, but negatively associated with culling rate during nulliparity in the offspring (P < 0.05). Maternal milk protein percentage was positively associated with birth weight, APMF, APMP, FPR and culling rate, but negatively associated with milk yield and fertility in the offspring (P < 0.05). Maternal FPR was positively associated with APMF and FPR, but negatively associated with culling rate, APMP and fertility in the offspring (P < 0.05). However, concentration of AMH in the offspring was not associated with MFP, MPP and MFPR (P > 0.05). In conclusion, the present study revealed that maternal milk fat and protein percentage and their ratio were associated with birth weight, survival, production and reproduction of the offspring. Yet it was a preliminary research and further studies are required to elucidate the mechanisms underlying these associations.

Phenotypic and genetic relationships among anogenital distance, anti-Müllerian hormone, and in vitro embryo production in Gyr dairy cattle

Anti-Müllerian hormone (AMH) concentration and number of recovered oocytes (ROOC) are phenotypic parameters associated with in vitro embryo production (IVEP). More recently, anogenital distance (AGD) has been proposed as a proxy for fertility in dairy cattle that is easy to collect at a low cost. The aim of this study was to characterize the AGD and its phenotypic and genetic associations with AMH and IVEP in Bos indicus Gyr dairy cattle. The hypothesis was that the number of ROOC, in vitro-produced embryos, and AMH concentration would increase as the AGD decreases. From July to December 2021, a single morphometrical measurement of AGD was collected in 552 donors from 6 herds in Brazil. A subset of donors had AMH assayed on the same day. Only ovum pick-up events that occurred up to 12 mo preceding and 7 mo succeeding the AGD measurement were used to assess the association between AGD, AMH, and IVEP. Thus, 472 donors (1,551 ovum pick-up events and 140 donors with AMH) were considered in the analysis. A raw average was calculated for each individual donor's ROOC, viable oocytes, total produced embryos, viability rate, and embryo rate (defined as total produced embryos/viable oocytes). Comparisons were conducted within the age categories of 3 to <6 yr or 6 to <10 yr. Phenotypic associations were performed in SAS software (SAS Institute Inc., Cary, NC). Genetic correlations were estimated using the BLUPF90 family of programs. The AGD (128.7 mm ± 14; mean ± standard deviation) had a normal distribution and was highly variable (83 to 172 mm) among the Gyr population. Our experimental hypothesis was partially supported by a phenotypic association of a greater number of total produced embryos (R2 = 0.023) as AGD decreased. Our results failed to support an increase in AMH concentration along with a decrease in AGD. In addition, positive and low genetic correlations were observed between AGD and viable oocytes (r = 0.08), and embryo rate (r = 0.20). A greater number of viable oocytes and embryos were observed in donors in the high compared with intermediate and low ROOC categories within both age categories. The age interval of 3 to <6 yr showed a greater number of recovered and viable oocytes for the high AMH compared with the low category, but no differences were observed among the AGD categories. In summary, for the Gyr breed, AGD was phenotypically inversely associated with a quantity-related parameter, such as the total number of produced embryos. In contrast, AGD showed a low genetic correlation with qualitative-related outcomes such as viable oocytes and embryo rate. Further studies should be performed to validate these retrospective analyses and to better understand the association between AGD and IVEP.

Reduced embryo yield obtained from superstimulated ewes with low circulating AMH concentration is improved by lengthening the FSH treatment

The aim of the present study was to evaluate: 1) the association between AMH, AFC, superovulatory response and embryo yield in sheep; and 2) the effect of FSH treatment length during superstimulation of the first follicular wave on ovarian response and embryo yield, particularly in ewes with low and high AMH. The experiment was performed on 63 Polled Dorset ewes that received an ovarian superstimulatory treatment during the first follicular wave (Day 0 protocol). Ewes were administered a total dose of 240 mg of FSH distributed in six (6-dose regimen, n = 30) or eight (8-dose regimen, n = 33) decreasing doses administered 12 h apart. On Day -9 (random stage of the estrous cycle) and Day 0 (day of the first FSH dose) ovarian ultrasonography was performed and blood samples were collected for AFC and AMH determinations, respectively. A weak positive correlation between AMH and small AFC (follicles <4 mm) was observed (r = 0.23; P = 0.07), and AMH concentration was positively correlated (r = 0.29; P < 0.05) with the number of corpora lutea (CL) determined at embryo collection (i.e., 6 d after insemination). The length of FSH treatment tended (P = 0.06) to affect the ovarian response, such that the number of CL was greater in 8-dose than 6-dose treated ewes, while no differences (P > 0.10) in embryo yield outcomes were observed. For further analysis, ewes were classified into low (<7 ng/mL) and high (>10 ng/mL) serum AMH. In high AMH ewes, there were no differences (P > 0.05) in the number of CL nor embryo yield between the 6-dose and 8-dose treatment (e.g., 7.8 ± 2.4 and 8.3 ± 2.5 transferable embryos, respectively; P = 0.92). Conversely, for low AMH ewes, fertilized ova and embryo yield were greater (P ≤ 0.05) for ewes receiving the 8-dose than the 6-dose superstimulatory treatment (e.g., 8.4 ± 2.8 vs. 2.7 ± 0.9 transferable embryos, respectively, P ≤ 0.05). In conclusion, embryo production in poor responding ewes with low low circulating AMH is improved by extending the superstimulatory treatment length from 6 to 8 FSH doses.

Developmental programming of reproduction in the female animal

Successful reproduction is a cornerstone in food animal industry in order to sustain food production for human. Therefore, various methods focusing on genetics and postnatal environment have been identified and applied to improve fertility in livestock. Yet there is evidence indicating that environmental factors during prenatal and/or neonatal life can also impact the function of reproductive system and fertility in the animals during adulthood, which is called the developmental programming of reproduction. The current review summarizes data associated with the developmental origins of reproduction in the female animals. In this regard, this review focuses on the effect of plane of nutrition, maternal body condition, hypoxia, litter size, maternal age, parity, level of milk production and milk components, lactocrine signaling, stress, thermal stress, exposure to androgens, endocrine disrupting chemicals, mycotoxins and pollutants, affliction with infection and inflammation, and maternal gut microbiota during prenatal and neonatal periods on the neuroendocrine system, puberty, health of reproductive organs and fertility in the female offspring. It is noteworthy that these prenatal and neonatal factors do not always exert their effects on the reproductive performance of the female by compromising the development of organs directly related to reproductive function such as hypothalamus, pituitary, ovary, oviduct and uterus. Since they can impair the development of non-reproductive organs and systems modulating reproductive function as well (e.g., metabolic system and level of milk yield in dairy animals). Furthermore, when these factors affect the epigenetics of the offspring, their adverse effects will not be limited to one generation and can transfer transgenerationally. Hence, pinpointing the factors influencing developmental programming of reproduction and considering them in management of livestock operations could be a potential strategy to help improve fertility in food animals.

Effects of maternal antral follicle count in Bos taurus indicus cattle on the genetic merit of male offspring and antral follicle count of female offspring

This study evaluated the effects of antral follicle count (AFC) in female cattle on offspring characteristics. Recently calved multiparous Bos indicus cows (Nelore; n = 222) were evaluated using ultrasonography on random days of their estrous cycle to determine the AFC and were classified into "low" (≤15 follicles), "intermediate" (≥16 and ≤ 29 follicles), and "high" (≥30 follicles) AFC groups. Weight and scrotal circumference (SC) of male offspring from these cows (n = 127) were determined from 20 to 27 months, and the data were added to a genetic evaluation program (economic total genetic merit, MGTe and TOP value) that uses the kinship matrix to evaluate the genetic relationship between animals. The AFC of female offspring from these cows (n = 95) was evaluated to analyze the relationship between the AFC of mothers and daughters. The effects of maternal AFC on the genetic merit of male and female offspring were analyzed using GLIMMIX and GLM, respectively. Correlations were assessed using the Pearson's coefficient. Male offspring of cows with high AFC had superior MGTe (P = 0.005) and TOP values (P = 0.01) than those from cows with low AFC. Additionally, the AFC of mothers was positively correlated with MGTe (R = 0.33; P < 0.0001) and negatively correlated with TOP values (R = -0.32; P < 0.0001). The SC (P = 0.01), but not body weight of the offspring (P = 0.46) was affected by maternal AFC. The daughters' AFC were correlated (R = 0.29; P = 0.004) with mothers' AFC and were influenced by maternal (P = 0.05) but not paternal (P = 0.77) effect. In conclusion, cows with high AFC produced males with greater MGTe, superior TOP values and higher SC. Maternal AFC did not influence the weight of male offspring but was correlated with the AFC of daughters.

Developmental programming of production and reproduction in dairy cows: III. Association of level of maternal milk production with offspring's birth weight, survival, productive and reproductive performance and AMH concentration from birth to the first lactation period

Although some studies investigated the relationship of dam milk production (DMP) with offspring birth weight and productive performance, limited information is available on the association of level of DMP with reproductive performance in dairy cows. Therefore, the present study was conducted to understand whether dams with various levels of milk production produce offspring with different fertility. In study I, offspring were classified based on the level of DMP into five categories, including DMP1 (dams with <10.00 × 103 kg of 305-day milk production), DMP2 (dams with ≥10.00 × 103 kg and <12.00 × 103 kg of 305-day milk production), DMP3 (dams with ≥12.00 × 103 kg and <14.00 × 103 kg of 305-day milk production), DMP4 (dams with ≥14.00 × 103 kg and <16.00 × 103 kg of 305-day milk production) and DMP5 (dams with ≥16.00 × 103 kg of 305-day milk production). In study I, data of birth weight, milk yield and reproductive variables of 14,536 offspring born to lactating dams and corresponding data of DMP were retrieved. In study II, blood samples (n = 339) were collected from offspring in various categories of DMP for measurement of serum AMH. Offspring were heavier at birth in DMP4 and DMP5 categories than DMP1 and DMP2 categories (P < 0.05). Milk yield of offspring increased as DMP elevated (P < 0.05); however, offspring in DMP1 and DMP2 categories produced higher milk as compared with their dams during primiparity (P < 0.05) whereas offspring in DMP3, DMP4 and DMP5 categories produced less milk as compared with their dams during primiparity (P < 0.05). Milk fat to protein ratio during the first month of lactation was greater in DMP4 and DMP5 categories than DMP1 category (P < 0.05). Offspring of DMP4 and DMP5 categories were inseminated and conceived at younger ages than offspring of DMP1 category during nulliparity (P < 0.05). Calving to conception interval was longer in DMP5 than DMP1 category in primiparous offspring (P < 0.05), but concentration of AMH did not differ among various categories of DMP (P > 0.05). In conclusion, dams with greater level of milk production produced heavier offspring with higher milk yield but worse transgenerational improvement in milk production and diminished reproductive performance, which were seemingly under higher pressure of negative energy balance during the first month of lactation.

Evaluation of serum anti-Müllerian hormone concentrations following treatment with vitamin D in Holstein Friesian heifers

Anti-Müllerian hormone (AMH) levels in the blood of dairy cattle are associated with the count of antral follicles (AFC), ovarian function. Numerous studies, particularly in human medicine, have shown that vitamin D3 (Vit D3) has a positive effect on AMH levels. To our knowledge, the effects of Vit D3 on serum AMH levels in heifers have not been investigated. The goal of the current study was to evaluate the concentrations of serum AMH in dairy heifers following Vit D3 treatment. The study included 20 healthy non-pregnant Holstein Friesian heifers. These animals came to estrus at least once. All heifers received a single intramuscular dosage of 5 million IU Vit D3 (Cholecalciferol). Blood samples were collected from the coccygeal veins of all animals before and after Vit D3 injection (days 7, 14, and 28) for the measurement of AMH and 25(OH)D concentrations. In our analysis, we observed that after exogenous Vit D3 administration, circular 25(OH)D increased constantly (up to day 28 after Vit D3 injection) in all animals. On day 28, AMH concentrations saw a 10% increase in comparison with those measured the day before the Vit D3 injection. However, a comparison of AMH concentrations measured across days did not reveal statistically significant differences between Day 0, 7, 14, and 28 levels (p = .10). Furthermore, no statistical correlation was observed between the pairs (age-AMH) and (weight-AMH). Considering all times, no correlation was found between 25(OH)D and blood AMH levels. These findings demonstrated that exogenous Vit D3 did not affect serum AMH in Holstein Friesian heifers.

Oocyte quality in adapted Bos taurus taurus cows

The objective of the current study was to determine the performance of creole cows of the Chino Santandereano breed in the ultrasound-guided follicular aspiration technique (OPU) and the quality of oocytes recovered. A total of 15 multiparous cows were selected from a herd located in the department of Santander with tropical climate. The cows were submitted to 5 sessions of follicular aspiration with an interval of 45 days. In each aspiration session, 7.9 ± 0.7 oocytes were recovered per cow, with a recovery rate of 64.9% ± 0.5 and a rate of viable and non-viable oocytes of 64.3% ± 0.6 and 35.7% ± 0.7, respectively. A difference (P < 0.05) in oocyte quality was presented for grades I, II and III (7.7 ± 0.4, 19.8 ± 0.5 and 36.8 ± 0.5, respectively). The results suggest that Chino Santandereano cows submitted to the OPU technique have a higher percentage of grade III oocytes recovered.

Ovarian stimulation with excessive FSH doses causes cumulus cell and oocyte dysfunction in small ovarian reserve heifers

Excessive FSH doses during ovarian stimulation in the small ovarian reserve heifer (SORH) cause premature cumulus expansion and follicular hyperstimulation dysgenesis (FHD) in nearly all ovulatory-size follicles with predicted disruptions in cell-signaling pathways in cumulus cells and oocytes (before ovulatory hCG stimulation). These observations support the hypothesis that excessive FSH dysregulates cumulus cell function and oocyte maturation. To test this hypothesis, we determined whether excessive FSH-induced differentially expressed genes (DEGs) in cumulus cells identified in our previously published transcriptome analysis were altered independent of extreme phenotypic differences observed amongst ovulatory-size follicles, and assessed predicted roles of these DEGs in cumulus and oocyte biology. We also determined if excessive FSH alters cumulus cell morphology, and oocyte nuclear maturation before (premature) or after an ovulatory hCG stimulus or during IVM. Excessive FSH doses increased expression of 17 cumulus DEGs with known roles in cumulus cell and oocyte functions (responsiveness to gonadotrophins, survival, expansion, and oocyte maturation). Excessive FSH also induced premature cumulus expansion and oocyte maturation but inhibited cumulus expansion and oocyte maturation post-hCG and diminished the ability of oocytes with prematurely expanded cumulus cells to undergo IVF or nuclear maturation during IVM. Ovarian stimulation with excessive FSH is concluded to disrupt cumulus cell and oocyte functions by inducing premature cumulus expansion and dysregulating oocyte maturation without an ovulatory hCG stimulus yielding poor-quality cumulus-oocyte complexes that may be incorrectly judged morphologically as suitable for IVF during ART.

Effects of postpartum diseases on antral follicle count and serum concentration of Anti-Müllerian hormone in dairy cows

The antral follicle count (AFC) and Anti-Müllerian hormone (AMH) concentration are validated markers for ovarian reserve in cattle, but their use as fertility markers is controverse. Here we assessed the effects of postpartum diseases on AFC and AMH concentration, as well as the influence of parity and breed on these parameters. Cows (n = 513, mostly Holstein Friesian and Brown Swiss, parity 3.0 ± 1.8) underwent a single ultrasonography examination 28-56 days after parturition and categorized as having low (n ≤ 15 follicles), intermediate (n = 16-24 follicles), or high (n ≥ 25 follicles) AFC based on objective video analysis of recorded sequences. Blood samples for AMH determination were collected at the time of examination and animals divided into low (< 0.05 ng/ml) and high AMH (≥ 0.05 ng/ml) group, respectively. No effects of postpartum diseases or breed on either AFC or AMH groups could be observed. There was a strong interaction between parity and AFC, primiparous cows having less follicles (13.6 ± 6.2 vs. 17.1 ± 7.0, P < 0.001) than pluriparous cows. The AFC did not affect reproductive parameters or productivity of the cows. In comparison, pluriparous cows with high AMH concentration had shorter calving to first service (86.0 ± 37.6 vs. 97.1 ± 46.7 days, P < 0.05) and calving to conception (123.8 ± 51.9 vs. 135.8 ± 54.4 days, P < 0.05) intervals, but lower milk yield (8440.3 ± 2292.9 vs. 8927.9 ± 2192.5 kg, P < 0.05) compared to cows with low AMH. In conclusion, no effect of postpartum diseases on AFC or AMH concentration of dairy cows could be observed. However, an interaction between parity and AFC, as well as associations of AMH with fertility and productivity in pluriparous cows, were demonstrated.

Ovarian morphology and follicular dynamics associated with ovarian aging in Bos indicus beef cows

This study characterizes the ovarian volume, antral follicle count (AFC), and ovarian dynamics of cows at different ages. Nellore cows (Bos taurus indicus) were used in two experiments. In Experiment 1, 57 lactating cows ranging in age from 3 to 23 years had their estrous cycle synchronized based on progesterone/estradiol treatments. The ovaries were scanned by ultrasound to record ovarian volume and AFC prior to follicle aspiration (AFC1). A second AFC (AFC2) was performed 5 days later to count only the growing antral follicles. In Experiment 2, six long-lived (14- to 23-year-old) and three young (4- to 8-year-old) non-lactating cows were submitted to daily ovarian scanning ultrasound during an interovulatory interval. Blood samples were collected during the estrous cycle to assess serum progesterone concentration. Data were analyzed using Student's t-test, ANOVA, and regression analysis tests. In Experiment 1, there were more (P < 0.05) antral follicles in AFC1 (31.4 ± 3.5) than in AFC2 (22.6 ± 2.4). In AFC1, the volume of the right ovary (6.03 ± 0.5 cm³) was greater (P < 0.01) than that of the left one (4.53 ± 0.4 cm³), although the AFC did not differ between the two ovaries (15.3 ± 1.8 and 16.3 ± 1.8, respectively). In both AFC1 and AFC2, there was a decline in the number of antral follicles as the age of the cow increased (P < 0.01). Ovarian volume (average of both ovaries) was related (P < 0.01) with AFC (R² = 0.1499) and cow age (R² = 0.0911). In Experiment 2, young and old cows under the age of 20 had a pattern of follicular growth waves, while cows over 20 years old did not have waves of follicular growth. The progesterone profiles and corpus luteum size during the estrous cycle did not differ between the groups. In conclusion, although cows had increased ovarian volume and decreased follicular population as they age, the follicular growth pattern and corpus luteum functionality appear to be unaffected by age.

Review: Environment of the ovulatory follicle: modifications and use of biotechnologies to enhance oocyte competence and increase fertility in cattle

The oocyte is the basis of life, supporting development from a fertilized cell to an independent multicellular organism. The oocyte's competence to drive the first cell cycles postfertilization are critical to embryonic survival and subsequent successful pregnancy. Coupled with the complex processes of follicle assembly, activation, differentiation, growth, and terminal maturation, oocyte developmental competence is gradually acquired during oocyte growth and meiotic maturation. Most reproduction management technologies and interventions are centered around these highly coordinated processes, targeting the ovarian follicle and the oocyte within. Thus, our objective was to highlight key aspects of oocyte and follicle development in cattle, and to discuss recent advances in oocyte and follicle-centered reproductive biotechnologies.

Review: The ovarian follicular reserve - implications for fertility in ruminants

Ruminants are born with a finite number of healthy ovarian follicles and oocytes (ovarian reserve) and germ cell proliferation in the developing foetal gonad predominantly occurs during early gestation. Two markers have been established to reliably estimate the size of the ovarian reserve in cattle: the number of antral follicles ≤3 mm in diameter recruited per follicular wave (Antral Follicle Count, AFC) and peripheral concentrations of the Anti-Müllerian hormone (AMH). Studies that used one or both indicators show that the size of ovarian reserve varies greatly among age-matched individuals, but is highly repeatable in the same animal. Conditions during prenatal life are likely among the causes of such variation in the ovarian reserve. In addition, the size of the ovarian reserve is a moderately heritable trait in cattle. The association between ovarian reserve and fertility is controversial. Several studies indicate that cattle with a low ovarian reserve have phenotypic characteristics that are associated with suboptimal fertility. On the contrary, the presence and absence of a positive association between AFC and/or AMH and fertility measures (i.e. no. on services/conception, pregnancy rates, pregnancy loss) have been equally reported in cattle. In conclusion, the size of the ovarian reserve in the progeny can be enhanced by improving management of the dam from preconception to early gestation and also through genetic selection. However, although the ovarian reserve may be among the determinants of reproductive success in ruminants, the use of AFC/AMH as reliable predictors of fertility is yet to be established. Furthermore, the possibility that there is a complex interaction of AFC, AMH and reproduction has yet to be fully characterised and exploited to improve fertility in cattle.

Review: Development, adoption, and impact of assisted reproduction in domestic buffaloes

The domestic buffalo (Bubalus bubalis), also known as water buffalo, comprises two sub-species the River buffalo (B. bubalis ssp. bubalis; 50 chromosomes) and the Swamp buffalo (ssp. carabanensis; 48 chromosomes). Domestic buffaloes are a globally significant livestock species. In South Asia, the River buffalo is a primary source of milk and meat and has a very important role in food security. The River buffalo also supports high-value, differentiated food production in Europe and the Americas. The Swamp buffalo is an important draft animal and a source of food in Southeast Asia and East Asia. The growing importance of buffaloes requires that they undergo an accelerated rate of genetic gain for efficiency of production, product quality, and sustainability. This will involve the increased use of assisted reproduction. The initial application of reproductive technology in buffaloes had variable success as it relied on the adoption of procedures developed for cattle. This included artificial insemination (AI), sperm cryopreservation, and embryo technologies such as cloning and in vitro embryo production (IVEP). Reproductive technology has been progressively refined in buffaloes, and today, the success of AI and IVEP is comparable to cattle. Ovarian follicular superstimulation (superovulation) combined with in vivo embryo production results in low embryo recovery in buffaloes and has limited practical application. The contribution of elite female buffaloes to future genetic improvement will therefore rely mainly on oocyte pickup and IVEP. This will include IVEP from females before puberty to reduce generation intervals. This review provides for the first time a clear chronology on the development, adoption, and impact, of assisted reproduction in domestic buffaloes.

Review: Gestational and postnatal nutritional effects on the neuroendocrine control of puberty and subsequent reproductive performance in heifers

Pubertal attainment is an intricate biological process that involves maturation of the reproductive neuroendocrine axis and increased pulsatile release of gonadotropin-releasing hormone (GnRH) and luteinizing hormone. Nutrition is a critical environmental factor controlling the timing of puberty attainment. Nutrient restriction during early postnatal development delays puberty, whereas increased feed intake and adiposity during this period hasten pubertal maturation by imprinting the hypothalamus. Moreover, the dam's nutrition during gestation can program the neuroendocrine system in the developing fetus and has the potential to advance or delay puberty in the offspring. Leptin, a hormone produced primarily by adipose cells, plays an important role in communicating energy status to the brain and regulating sexual maturation. Leptin's regulation of GnRH release is mediated by an upstream neuronal network since GnRH neurons do not contain the leptin receptor. Two groups of neurons located in the arcuate nucleus of the hypothalamus that express neuropeptide Y (NPY), an orexigenic peptide, and alpha melanocyte-stimulating hormone (αMSH), an anorexigenic peptide, are central elements of the neural circuitry that relay inhibitory (NPY) and excitatory (αMSH) inputs to GnRH neurons. Moreover, KNDy neurons, neurons in the arcuate nucleus that co-express kisspeptin, neurokinin B (NKB), and dynorphin, also play a role in the metabolic regulation of puberty. Our studies in beef heifers demonstrate that increased rates of BW gain during early postweaning (4-9 mo of age) result in reduced expression of NPY mRNA, increased expression of proopiomelanocortin and kisspeptin receptor mRNA, reduced NPY inhibitory inputs to GnRH neurons, and increased excitatory αMSH inputs to KNDy neurons. Finally, our most recent data demonstrate that nutrition of the cow during the last two trimesters of gestation can also induce transcriptional and structural changes in hypothalamic neurocircuitries in the heifer progeny that likely persist long-term after birth. Managerial approaches, such as supplementation of the dam during gestation (fetal programming), creep feeding, early weaning, and stair-step nutritional regimens have been developed to exploit brain plasticity and advance pubertal maturation in heifers.

Spatial distribution of preantral follicles in ovarian parenchyma of bovine species

The goal of this study was to determine the distribution of preantral follicles in bovine ovaries. Follicular distribution in the ovaries (n = 12) was evaluated in the region of the greater curvature of the ovary (GCO) and the region close to the ovarian pedicle (OP) of Bos taurus indicus heifers of the Nelore breed. Two fragments were obtained from each region of the ovary (GCO and OP). The mean weight of the ovaries was 4.04 ± 0.32 g. The mean antral follicle count (AFC) was 54.58 ± 3.55 follicles (minimum and maximum variation of 30 and 71 follicles, respectively). In total, 1123 follicles were visualized in the region of the GCO; 949 (84.5%) of them were primordial follicles and 174 (15.5%) were developing follicles. The region close to the OP contained 1454 follicles, of which 1266 (87%) were primordial follicles and 44 (12.9%) were developing follicles. The OP region showed a higher proportion of intact follicles in the primordial (P < 0.0001) and primary (P = 0.042) stages compared with the GCO region. The proportion of secondary follicles was similar in the OP and GCO regions. The ovaries of two bovine females (16%; 2/12) contained multi-oocytes follicles, which were characterized as primary follicles. Therefore, the distribution of preantral follicles in the bovine ovary was heterogeneous, with the region close to the OP containing a greater number of preantral follicles compared with the GCO region (P < 0.05).

Evidence that elevation of maternal somatic cell count could lead to production of offspring with inferior reproductive and productive performance in dairy cows during the first lactation period

Although the effect of mastitis on reproduction and production of lactating dairy cows has been vastly studied, little information is available about the association of maternal udder health status with offspring reproduction and production. Therefore, the present research was conducted to study the association between maternal average monthly somatic cell count (SCC) with reproduction, anti-Müllerian hormone (AMH) concentration, udder health status and milk production in the offspring. Based on maternal average monthly SCC (MSCC), offspring were classified into five categories including MSCC1 (SCC <200,000; n = 3005), MSCC2 (200,000 ≤ SCC <400,000; n = 252), MSCC3 (400,000 ≤ SCC <600,000; n = 103), MSCC4 (600,000 ≤ SCC <800,000; n = 40) and MSCC5 (SCC ≥800,000; n = 61). Data associated with reproduction, production and udder health status of offspring were retrieved from the herd database. In addition, blood samples were collected from a subset of offspring (n = 136) for measurement of serum AMH, as a reliable marker of ovarian reserves. Offspring in MSCC5 category had more services per conception and longer calving to conception interval than offspring in MSCC1 and MSCC2 categories (P < 0.05). The average number of SCC and risk of clinical mastitis in the offspring were not associated with MSCC (P > 0.05). But offspring in MSCC5 category produced less milk, fat and protein than offspring in MSCC1 category (P < 0.05). In addition, AMH concentration was lower in MSCC5 than MSCC1 category (P < 0.05). In conclusion, the present study showed that elevated maternal average monthly SCC could culminate in birth of offspring with inferior reproductive performance, smaller size of ovarian reserves and lower level of milk production during the first lactation period.

Transvaginal ultrasound-guided oocyte retrieval in cattle: State-of-the-art and its impact on the in vitro fertilization embryo production outcome

Transvaginal ultrasound-guided oocyte retrieval (commonly called OPU) and in vitro embryo production (IVP) in cattle has shown significant progress in recent years, in part, as a result of a better understanding of the full potential of these tools by end users. The combination of OPU and IVP (OPU-IVP) has been successfully and widely commercially used worldwide. The main advantages are a greater number of embryos and pregnancies per unit of time, faster genetic progress due to donor quick turn around and more elite sires mating combinations, larger spectrum of female age (calves, prepuberal, heifer, cow) and condition (open, pregnant) from which to retrieve oocytes, a reduced number of sperm (even sexed) required to fertilize the oocytes, among other benefits. OPU-IVP requires significant less donor preparation in comparison to conventional embryo transfer (<50% of usual FSH injections needed) to the extent of no stimulating hormones (FSH) are necessary. Donor synchronization, stimulation, OPU technique, oocyte competence, embryo performance, and its impact on cryopreservation and pregnancy are discussed.

Oocyte developmental capacity is influenced by intrinsic ovarian factors in a bovine model for individual embryo production

The ovary and its hormones may have major effects on the in vitro developmental capacity of the oocytes it contains. We related intrinsic ovarian factors namely the presence of corpus luteum (CL) and/or dominant follicle (>8 mm) and the follicular count to cumulus expansion (CE), embryo development, and blastocyst quality in a bovine model. Cumulus-oocyte-complexes (COCs) were aspirated from follicles between 4 and 8 mm in diameter. In vitro embryo production was performed in a fully individual production system. The follicular fluid from which COCs were collected was pooled (per ovary) to evaluate the estrogen, progesterone, and insulin-like growth factor-1 (IGF-1) concentrations. Cumulus oocyte complexes collected from ovaries without a CL presented a greater CE than COCs derived from ovaries bearing CL. The absence of ovarian structures increased the blastocyst rate when compared to oocytes derived from ovaries with a CL, a dominant follicle, or both. Blastocysts derived from ovaries without a dominant follicle presented higher total cell numbers and a lower proportion of apoptosis than blastocysts derived from ovaries containing a dominant follicle. Cumulus oocyte complexes collected from ovaries with high follicular count resulted in higher cleavage than from ovaries with low follicular count, but the blastocyst rate was similar between groups. Ovaries bearing a CL had greater progesterone and IGF-1 follicular fluid concentrations in neighboring follicles than ovaries without a CL. Selection for bovine ovaries without CL or dominant follicle can have positive effects on CE, embryo development, and blastocyst quality in an individual embryo production system set-up.

Anti-Müllerian hormone in queens: Serum concentrations and total ovarian follicle population

The objectives of this study were: a) To report anti-Müllerian hormone (AMH) serum concentrations in neonatal, pre and postpubertal female cats. b) To establish the relationship between serum AMH with either age and estrous cycle c) To correlate the total number of different ovarian follicle types with AMH in adult queens. A single blood sample was collected from 10 neonates (including 5 male), 15 prepubertal and 48 postpubertal female cats to measure AMH. Eight, 10, and 18 of this latter group were in follicular (FP), luteal phase (LP), and anestrus (AN), respectively. The total number of each follicle type was histologically counted using the Gougeon and Chainy (1987) formula in a subgroup of 10 adult queens. Overall AMH mean of these the female cats was 6.31 ± 0.54 ng/mL. The neonatal females had lower AMH serum concentrations than their male littermates (2.56 ± 0.49 vs. >23 ng/mL; P < 0.01). Concentrations were also higher in prepubertal than in neonatal and postpubertal cats (11.79 ± 1.36 vs. 2.56 ± 0.49 vs. 4.87 ± 0.38 ng/mL; P < 0.01). Queens below 12 mo of age had the highest AMH levels (10.41 ± 1.16; P < 0.01). Age was inversely correlated with AMH (r = -0.5; P < 0.01). Animals in FP had lower AMH concentrations than AN females (2.51 ± 0.33 vs. 5.46 ± 0.76 ng/mL; P < 0.05). No difference in the total number of each follicle type were found between either ovary (P > 0.05). A high correlation was only found between small antral follicles and AMH concentrations (r = 0.85; P < 0.01). It was concluded, that AMH can provide an indirect, reliable marker for the assessment of ovarian follicle size and functionality. Age as well as pubertal state should be considered when evaluating AMH concentrations in this species.

Repeated controlled ovarian stimulation-induced ovarian and uterine damage in mice through the PI3K/AKT signaling pathway

The effects of repeated controlled ovarian stimulation (COS) on the female reproductive system are still controversial. This study investigated the effects of repeated COS on the ovaries and uterus of mice and its possible mechanism. Female ICR (Institute of Cancer Research) mice were subjected to the COS using pregnant mare serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG) for 1, 3, 5, and 7 cycles. Serum hormone levels, reactive oxidative stress (ROS), 8-hydroxy-2'-deoxyguanosine (8-OHdG), total antioxidant capacity (T-AOC), and superoxide dismutase (SOD) in the mouse ovary and uterus were analyzed by ELISA. The morphology of the ovary and endometrium, ovarian apoptosis, and expressions of the vascular endothelial growth factor (VEGF), leukemia inhibitory factor (LIF), PI3K, AKT, Bax, and Bcl-2 in the ovarian and uterine tissues were tested by hematoxylin-eosin (HE) staining, immunohistochemistry, and western blot. The results showed that repeated COS significantly decreased the hormone level (estradiol, progesterone and anti-Müllerian hormone), high-quality of the MII oocyte ratio, oocyte and embryo number, antioxidant capacity (T-AOC, SOD activity), and the protein level of Bcl-2, LIF, and VEGF, but increased the oxidative damage (ROS, 8-OHdG content), embryo fragment ratio, and expression of pro-apoptotic protein Bax. In addition, the expressions of p-PI3K and p-AKT also decreased with the increase of COS cycle. In conclusion, repeated COS causes ovarian and uterus damage possibly through the PI3K/AKT signaling pathway, and this finding may provide some experimental basis for guiding clinical treatment.

Associations of antral follicle count with fertility in cattle: A review

Ovarian antral follicle count (AFC) is a marker of ovarian stimulatory response to superovulation protocols in cattle. This article reviews novel research from the past 10 years, focusing on the relationship between AFC and embryo production and cow fertility. Substantial evidence indicates a positive relationship between AFC with embryo production; however, conflicting findings exist regarding the relationship of AFC with conception and pregnancy rates. This lack of consistent association with pregnancy outcomes is perplexing given the differences detected in oocytes, embryos, and endometria from high- versus low-AFC animals. Those differences include markers of embryonic viability such as protein level, blastocyst development rates, cleavage rates, and blastocyst cell numbers that differ between high- and low-AFC groups, as well as differential gene expression at the cow and embryo level with genes associated with fertility. In addition, Bos indicus and Bos taurus cattle appear to have different fertility responses based on their AFC category. In summary, clearly more studies are needed to elucidate the true associations between AFC and cow fertility, but the data that have been accumulated thus far indicate that AFC has the potential to be a useful marker of lifetime cow fertility.

Effect of follicular wave stage on potential fertility predictors and their repeatability coefficient in prepubertal Bos indicus (Nellore) and Bos taurus (Caracu) heifers

In an attempt to develop accessible methods for the precocious individual selection based on phenotypic attributes related to reproductive superiority, this study evaluated the effects of follicular wave stages (emergence and dominance) and the repeatability coefficients of potential fertility predictors (vulvar morphometry, uterine biometry, echogenicity and echotexture, ovarian biometry, and antral follicle count - AFC) in two breeds of purebred prepubertal heifers. Nellore (n = 30) and Caracu (n = 28) heifers were submitted to a sequence of 11 evaluations conducted every 48 h (D0 - random day of the antral follicular wave until D20) to study potential fertility indicators under natural conditions. The data obtained were compared according to breed and follicular wave stage. Statistical analysis included the fixed effects of breed, evaluation day, and their statistical interaction and was performed using MIXED, GENMOD, GLM, and CORR procedures of the SAS program. Breed was found to influence rima height, ovarian area, and AFC, which were greater in Nellore heifers (P < 0.02). The follicular wave stage also influenced most of the potential predictors, highlighting AFC which was higher in the presence of a dominant follicle in both breeds (P < 0.0001). The repeatability coefficients for vulvar width (0.76 and 0.66), ovarian area (0.70 and 0.62), and AFC (0.76 and 0.74) were considered to be high in Nellore and Caracu heifers, respectively. Only ovarian biometry was able to predict AFC (Pearson correlation coefficient ≥ 0.66; P < 0.0001) in prepubertal heifers. The results indicate that most of the phenotypic reproductive parameters analyzed can be characterized throughout prepuberty using a single measure since they are intrinsic attributes of the individual.

Relationships between antral follicle counts and ovarian morphology of Bos indicus of different ages

ABSTRACT This study aimed to evaluate the relationship between the antral follicle count (AFC) and the ovarian morphology of Bos indicus in different age groups: 12-23 months (G1), 24-35 months (G2), 36-47 months (G3), 48-59 months (G4), and >60 months (G5). Ovaries were collected individually and sent to the laboratory, where we measured AFC, the diameter and weight of the ovaries, dominant follicle (DF, ≥8mm), corpus luteum (CL), and small follicles (SF, <8mm). AFC were classified as high, intermediate-high, intermediate-low, and low. A group of ovaries was subjected to follicular aspiration to evaluate the morphological quality of the recovered cumulus oocyte complexes (COCs). Mean AFC did not vary between ages. The morphological characteristic that was most closely correlated with AFC was the weight of the small follicles. There was no relationship between AFC and the weight and diameter of the DF and CL. Quality of the COCs was superior in ovaries in which the CL was present, but it did not vary between the AFC classes. We conclude that AFC can be performed on a single ovary, regardless of the presence, diameter, and weight of the CL and DF in zebu between 12 and 60 months old.