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Ovum pick-up (OPU) followed by intracytoplasmic sperm injection (ICSI) is increasingly used in horses, yet embryo production rates remain variable, potentially reflecting differences in oocyte developmental competence at the time of aspiration. We investigated whether the stage of the follicular wave, growth phase (GP) versus atresia phase (AP), and associated endocrine profiles in mares, influence oocyte developmental competence. Mares underwent follicular ablation to synchronize follicular waves, and oocytes were aspirated during GP or AP for in vitro production of embryos. Serum concentrations of progesterone (P4), luteinizing hormone (LH), follicle-stimulating hormone (FSH), inhibin A, inhibin B, and anti-Müllerian hormone (AMH) were measured daily. Oocyte maturation rate was higher in AP than in GP (62.8% vs. 17.1%; P < 0.01). Blastocyst formation per recovered oocytes was numerically higher in AP than GP, although the difference was not significant (20.0% vs 7.3%; P = 0.34). At the mare level, 4/6 AP mares (66.7%) vs 1/7 GP mares (14.3%) produced ≥1 blastocyst, but not statistically significant (P = 0.091). Chromatin analysis revealed a higher proportion of non-matured oocytes in post-germinal-vesicle stages in AP than in GP (30.8% vs. 2.9%, P < 0.01). Endocrine analyses revealed lower P4 and higher inhibin A concentrations in AP mares (P < 0.01). LH, FSH, and inhibin B exhibited significant group-by-day interactions (P < 0.05), characterized by higher LH and inhibin B and lower FSH in AP mares. These findings demonstrate that follicular physiological status at the time of aspiration influences oocyte competence in mares and suggest that targeting follicles entering early atresia may improve outcomes of equine OPU-ICSI programs.
Ovarian tissue vitrification holds great promise as a preservation technique for endangered wild felids; however, the development of an optimal protocol remains desired. One potential factor affecting success is the equilibration temperature and its impact on follicular survival. We hypothesised that optimizing the equilibration conditions at low temperatures would enhance vitrification yield in domestic cat. To test this, we first optimised the equilibration time in a four-step protocol involving progressively decreasing temperatures. We then validated this approach through a comparative study against a room-temperature equilibration protocol. Contrary to our expectations, the cold equilibration strategy did not improve follicular survival, challenging previous assumptions about its potential benefits. This study provides new insights into the role of equilibration temperature in feline ovarian tissue vitrification and contributes to refining cryopreservation strategies for felids.
Tay-Sachs disease (TSD) is a fatal neurodegenerative lysosomal storage disease. The Jacob sheep is the only large-animal model of TSD, yet ocular pathology and the therapeutic potential of gene therapy remain poorly defined. Sheep cohorts included normal controls (n = 3); untreated TSD-affected (n = 4); intravenous AAV9-Bic_HexA/HexB-treated (n = 3); and intracerebroventricular, cisterna magna, and lumbar intrathecal AAV9- Bic_HexA/HexB-treated sheep (cerebrospinal fluid [CSF] therapy; n = 7). Retinal histopathology and immunohistochemistry, retinal whole-mount analyses for retinal ganglion cell (RGC) morphology and density, optic nerve evaluation with p-phenylenediamine (PPD )semi-thin sections, qPCR assessment for vector genomes, and RNAscope probes for transgene expression were performed. Untreated TSD sheep exhibited RGCs with abundant microvesicular cytoplasmic expansion and optic nerve spheroids, with storage material variably staining with periodic acid-Schiff. Marked astrocytosis, microgliosis, and GM2 accumulation within RGCs were present. Optic nerve axon counts and RGC density were significantly reduced, and optic nerve damage scores increased, in untreated and IV-treated sheep but were rescued with short-term CSF therapy. GM2 volume and signal intensity per RGC were significantly reduced following short-term CSF therapy. Minimal but detectable retinal vector genomes and transgene expression were observed. These findings demonstrate retinal and optic nerve pathology in Jacob sheep with TSD and AAV9 therapy.
This study investigated the effect of semen collection timing (06:00-08:00 h [morning] vs. 12:00-14:00 h [afternoon]) on semen quality in Thai native bulls under tropical heat stress conditions. Physiological responses, endocrine profiles, and sperm lipid peroxidation were also evaluated. Nine bulls were subjected to a multiple crossover design, with semen collection alternated between morning and afternoon periods across 12 sessions per animal. Environmental parameters, including temperature-humidity index (THI), were continuously monitored. Afternoon collections occurred under higher ambient temperature and THI (>81) than morning collections (77-80), accompanied by increased heart rate (93.88 vs. 79.75 beats/min; P < 0.001) and elevated average scrotal surface temperature (35.08 vs. 33.90 °C; P < 0.001). Serum cortisol concentrations did not differ between collection periods (2.36 vs. 2.18 ng/mL; P > 0.05), whereas testosterone levels were significantly higher in the afternoon (2.23 vs. 1.99 ng/mL; P < 0.05). Afternoon-collected semen exhibited higher total motility (82.80% vs. 76.02%; P < 0.05) and viability (83.68% vs. 77.24%; P < 0.05). However, acrosome integrity was significantly lower in afternoon collections than in morning collections (83.90% vs. 87.40%; P < 0.05), accompanied by higher malondialdehyde concentrations (1.15 vs. 0.84 µM/mL; P < 0.05). Midpiece abnormalities and bent tails with retained droplets were more prevalent in afternoon samples. These findings suggest a physiological trade-off between enhanced sperm motility and increased structural damage to sperm during afternoon semen collection under tropical heat stress. Morning collection may better preserve acrosome integrity and sperm morphology despite lower motility.
As a member of the Groucho/TLE family, Transducin-like enhancer of split 3 (TLE3) functions as a transcriptional co-repressor that is highly expressed in the testis. It recruits histone deacetylases (HDACs) and binds histones to mediate chromatin remodeling, thereby regulating gene expression. To investigate the physiological function of TLE3 in spermatogenesis, we generated germ cell-specific conditional knockout (cKO) mouse models using Stra8-Cre and Vasa-Cre drivers. However, Tle3 cKO male mice exhibited grossly normal development and fertility. Histological examination revealed intact testicular architecture and normal spermatogenic progression in the knockout mice. Moreover, immunofluorescence analyses of key germ cell marker proteins, including DDX4 (pan-germ cell), PLZF (undifferentiated spermatogonia), c-Kit (differentiating spermatogonia), γH2AX (meiosis recombination initiation) and PNA (acrosome in spermatids), showed normal germ cell distribution and differentiation. Furthermore, TUNEL assays for apoptosis detection revealed no significant difference between control and cKO mice. Collectively, our findings demonstrate that TLE3 is dispensable for male germ cell development and spermatogenesis.
Improving fecundity and growth is a major goal in sheep breeding. Here, we established a zygote electroporation platform to deliver base editor ribonucleoproteins (BE RNPs) targeting the fecundity-associated BMPR1B(FecB) and growth-associated SOCS2 loci. Single-target validation achieved high editing efficiencies (95.0% for BMPR1B and 65.0% for SOCS2) without compromising embryonic development in vitro, although bystander edits were prevalent. However, dual-target editing introduced guide RNA (gRNA) crosstalk between co-delivered adenine base editor (ABE) and cytosine base editor (CBE) RNPs in preimplantation embryos. We obtained three live lambs after transfer of dual-editing blastocysts. Although all lambs carried the intended BMPR1Bp.Q249R mutation, these mutations were consistently accompanied by bystander edits. One lamb exhibited additional gRNA crosstalk at the BMPR1B locus. This lamb also harbored an unintended 13-bp frameshift deletion at the SOCS2 locus, replacing the desired point mutation with a predicted null allele. These results demonstrate that multiplex BE RNP electroporation in sheep zygotes generates unpredictable genomic outcomes, including bystander edits, gRNA crosstalk, and unintended indels. Consequently, current multiplex base editing systems, as implemented via co-electroporation of ABE and CBE RNPs, face significant challenges for routine application in sheep breeding.
Mesenchymal stromal cells from equine ovarian follicular aspirates represent a promising source for cell-based therapies. However, the age of the donor mare may alter their biological properties and therapeutic potential. This study aimed to evaluate the effect of age on MSCs from ovarian follicular aspirates of young (< 10 years, n = 5) and aged (≥ 18 years, n = 5) mares. MSCs were isolated, expanded, cryopreserved at passage 3, and subsequently thawed to evaluate proliferation, immunophenotype, differentiation capacity, and gene expression profiles. Proliferation rates, total cell yield, and mean time to reach 80% confluence showed no significant differences between the age groups. Flow cytometry analysis confirmed uniform expression of MSC-associated positive markers (CD90, CD29) and absence of CD45, CD19 and MHC-II in both groups. Trilineage differentiation assays demonstrated that cells retained trilineage differentiation capacity at a qualitative level regardless of donor age. However, transcriptomic analysis using RT2 Profiler PCR Array and qPCR validation revealed substantial differences in gene expression. MSCs from young mares exhibited significant upregulation (fold change ≥ 2; p < 0.05) of stemness-related genes (LIF, POU5F2), regulators of adipogenic and chondrogenic differentiation (PPARγ, SOX9), and cell migration-associated markers (MCAM, VCAM). Conversely, MSCs from young mares showed decreased expression (fold change ≤ 0.5; p < 0.05) of lineage-specific differentiation genes (TBX5, SLC2A4), inflammatory mediators (IL6), and senescence-associated markers (ITGAX, BMP4, SMAD3). These findings suggest that, although some MSC characteristics are preserved, donor age significantly alters the transcriptomic profile of equine follicular MSCs, which could affect their therapeutic efficacy.
While fast in vitro embryo development has been associated with improved outcomes, the relationships of slow in vitro embryo development and vitrified versus fresh in vitro produced (IVP) embryo transfer to foaling percentage and foal sex are less explored. To determine the relationships of (1) day of blastocyst formation (D7-11 after intracytoplasmic sperm injection (ICSI)) and (2) vitrification and warming method (one- and three-step) versus fresh transfer with pregnancy, early pregnancy loss (EPL), foaling percentage and foal sex. Retrospective clinical study. Blastocysts (n = 201) were collected on days 7-11 after ICSI of in vitro matured oocytes from Warmblood mares and transferred either fresh or vitrified-warmed into recipient mares on day 4 after ovulation. Pregnancy, EPL, foaling percentage, and foal sex were compared using multivariable generalised linear mixed-effects logistic regression models. Day of blastocyst formation was significantly associated with pregnancy outcome at D14 (p = 0.048), D42 (p = 0.046) and foaling percentage (p < 0.001). The odds of foaling decreased with developmental age, with significantly lower odds after D11 blastocyst transfer (OR = 0.0045, 95% CI 0.00034-0.061; p < 0.0001). Slow embryo development was associated with a significantly higher proportion of female offspring. The odds of obtaining a filly versus a colt were 5.6-fold higher for D10 blastocysts than D7 (95% CI 1.14-25.0; p = 0.034). Transfer of fresh versus vitrified-warmed blastocysts, using a one- or three-step protocol, did not significantly affect pregnancy or foaling outcome. Small sample size per day of blastocyst formation. Slow in vitro embryo development is associated with decreased pregnancy and foaling outcomes following transfer of D11 IVP blastocysts. Transfer of D10 IVP blastocysts yields acceptable foaling percentages and is associated with a higher proportion of female offspring. Vitrification is effective for preserving equine embryos and allows the use of a simplified one step warming protocol.
The worldwide climate is thought to be drastically changing as a result of the global temperatures, a phenomenon known as "global warming". Thermal stress is a crucial obstacle facing buffalo cyclicity. Investigation of the molecular regulation concerning proliferation and apoptosis of corpus luteum (CL) is not fully comprehended in buffaloes. We aimed to (1) study mRNA expression of candidate genes related to proliferation (PGR, AGTR1, and LHCGR) and apoptosis (TNFα, BAX, FASLG, CASP3, AGTR2 and PTGS2), (2) explore effect of thermal stress on the expression of HSP70, NOS1, NOS2 mRNAs, NO and SOD concentrations in CL homogenate during different stages of CL. For this, ovaries (n = 70) were collected in pairs from buffaloes during cold and hot seasons. According to morphology of CL, samples were divided into: early, mid, and late. For RNA isolation, NO and SOD concentrations, small sections from CL stages were frozen in - 80 °C. The results showed that PGR, AGTR2, TNFα, BAX, cALP2beta and PTGS2 mRNAs decreased (P < 0.001) at different stages of CL at hot season. The decline of AGTR2 associated with decreased NOS2 mRNA, which consequently affected TNFα, BAX, and CASP3 mRNAs. Apoptosis might be affected by direct effect of AGTR2 on CASP3 during thermal stress. We supposed that NO had a regulatory role during early and late stages of CL. It could be concluded that thermal stress (THI > 68) changed the expression of proliferation and apoptosis genes of CL in Egyptian buffaloes. Finally, the thermal stress in cold or hot seasons has marked impact on CL dynamics.
This study examined the impact of nutritional supplementation with chitosan oligosaccharides (COS) on the laying performance, egg quality, and serum biochemical markers of aged laying hens. A total of 192 aged laying hens with 80-week-old were randomly assigned to a baseline diet (CON) or a basal diet with 200, 400, or 800 mg/kg COS. Trial lasted 8 weeks. Compared to CON, the 200 mg/kg COS group showed numerical improvements in most parameters, but statistically significant enhancements were observed starting from 400 mg/kg. COS supplementation at 400 and 800 mg/kg significantly increased hen-day egg production, weight, mass, and improved feed conversion ratio (FCR: 2.52, 2.41, 2.24, 2.27 kg/kg egg mass for CON, COS200, COS400, COS800, respectively) compared to the CON group (P < 0.05). COS-supplemented groups showed increased egg quality, including thickness, strength, albumen height, Haugh unit, yolk color, and index (P < 0.05). Serum analysis showed COS supplementation decreased total cholesterol, triglycerides, and LDL-C while raising HDL-C (P < 0.05). COS-treated aged laying hens had higher total protein, albumin, and globulin and lower aspartate aminotransferase (AST) and alanine aminotransferase (ALT) compared to the control. Additionally, COS supplementation increased serum total antioxidant capacity (T-AOC), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) activities and decreased malondialdehyde (MDA) levels (P < 0.05); these antioxidant indicators exhibited a dose-dependent rise from 200 to 400 mg/kg, reaching a plateau at 800 mg/kg (e.g., SOD: 116.4, 132.7, 141.8, 139.6 U/mL). COS groups showed improved immune function, with greater serum immunoglobulin A (IgA), immunoglobulin G (IgG), and immunoglobulin M (IgM) levels (P < 0.05). The results showed that aged laying hens fed 400-800 mg/kg COS had superior laying performance, egg quality, lipid metabolism, antioxidant status, and immunological function, suggesting it could boost productivity and health.
Conventional milk indicators such as somatic cell count (SCC) and pH have limited specificity for monitoring caprine mastitis, particularly under non-antibiotic treatment protocols. This exploratory study evaluated the temporal behavior of milk N-acetyl-β-D-glucosaminidase (NAGase), SCC, total bacterial count (TBC), pH, and selected electrolyte indicators (Na, K, and Na/K ratio) across sequential non-antibiotic phases, including milk microbiota transplantation (MMT), Resilience (washout), and 7-epiclusianone, in an experimental Staphylococcus warneri mastitis model in goats. Using a paired-udder longitudinal design in six goats, treated udders showed sustained sodium elevation, potassium depletion, and increased Na/K ratio, indicating persistent blood-milk barrier disturbance across phases, whereas pH and TBC showed more variable responses. NAGase activity correlated positively with SCC and sodium and negatively with potassium, consistent with its association with mammary epithelial injury and inflammation. These findings suggest that NAGase, together with Na, K, and the Na/K ratio, may help characterize biomarker dynamics during non-antibiotic treatment. Given the exploratory design and small sample size, these findings require validation in larger studies before routine application.
Mastitis remains a significant health challenge affecting dairy cows, with implications for animal welfare, milk production, and farm profitability. In Nigeria, there are limited large-scale studies that have systematically investigated the multifactorial risk factors for mastitis across diverse production systems and geographical locations. This study aimed to assess the prevalence of mastitis and identify its risk factors using a hierarchical mixed effects logistic regression, block-wise analytical approach. A cross-sectional survey was conducted across 298 dairy farms in North-Central Nigeria. Data were collected on farm demographics, animal characteristics, housing and management practices, water and feeding routines, milking hygiene, and mastitis management. Mastitis was defined at the herd level as the occurrence of at least one farmer-reported case within the current lactation cycle. Because mastitis diagnosis relied on farmer-reported cases rather than laboratory confirmation (e.g., California Mastitis Test, CMT, or somatic cell count, SCC), the possibility of misclassification bias cannot be excluded and should be considered when interpreting the findings. Univariable and multivariable mixed-effects logistic regression models were fitted for each conceptual block of variables, accounting for clustering at the local government area (LGA) level using random intercepts. Model performance was evaluated using likelihood ratio tests, intraclass correlation coefficients (ICCs), and diagnostic plots of residuals. The prevalence of reported mastitis in the current year was 59.4% (95% CI: 53.7-64.9). Final multivariable models revealed significant associations between mastitis and herd size, presence of working bulls, milking hygiene (e.g., teat dipping and use of separate cleaning cloths), and mastitis treatment practices. Notably, large cattle herds had significantly higher odds of mastitis (adjusted OR = 6.56, 95% CI: 1.99-21.62), while post-milking teat dipping (OR = 0.013, 95% CI: 0.000-0.797) was strongly associated with lower odds. The ICC values across models ranged from 0.58 to 0.83, indicating substantial variation at the LGA level. Mastitis is highly prevalent in Nigerian dairy farms, with multivariable risks: herd demographics, management practices, and hygiene behaviours. Interventions promoting evidence-based milking hygiene and targeted herd-level management could substantially reduce mastitis burden. The hierarchical modeling approach provides a comprehensive framework for identifying context-specific risk factors and guiding regionally appropriate control strategies.
Granulosa cells (GCs) play a crucial role in maintaining follicular homeostasis and supporting the acquisition of oocyte developmental competence. Disruption of GC function may therefore impair oocyte maturation and subsequent embryo development. Although anti-inflammatory drugs are widely used in cattle, their potential direct effects on follicular function and reproductive competence remain poorly understood. The aim of this study was to evaluate whether exposure of bovine GCs to non-steroidal anti-inflammatory drugs (NSAIDs) and a steroidal anti-inflammatory drug (SAID) affects GC viability and morphology, and whether these alterations influence oocyte maturation and embryo developmental competence in vitro. Bovine GCs were exposed to Meloxicam, Flunixin, and Ketoprofen (NSAIDs) or Dexamethasone (SAID) at different concentrations and exposure times. Cell viability and morphology following treatment were evaluated by acridine orange and MTT test. Functional consequences were investigated using a GC-oocyte transwell co-culture system to assess oocyte maturation through first polar body extrusion and subsequent embryo development in vitro. Dexamethasone induced the most pronounced alterations in GC morphology and monolayer integrity. All drug treatments significantly reduced (P < 0.05) the percentages of matured oocytes and blastocyst formation on day 7 compared with controls. On day 11 of embryo culture, Flunixin (5 μM, 8 h) and Ketoprofen (10 μM, 48 h) exerted the most severe effects, as no hatched blastocysts were observed. GC alterations were associated with impaired oocyte developmental competence and reduced embryo developmental potential. These findings suggest that exposure to anti-inflammatory drugs disrupts GC function and impairs oocyte developmental competence and embryo development in vitro.
This study explored the development of salicylic acid-conjugated chitosan nanoparticles (SACNs) and their effectiveness in enhancing the cryopreservation of buffalo sperm. The assessment focused on post-thaw sperm quality and kinematics, microbiota profiles, oxidative stress markers, acrosome integrity, apoptosis, and docking analysis. Semen was collected from eight fertile buffalo bulls via an artificial vagina. Samples were diluted with a Tris-based extender and supplemented with SACNs at concentrations of 0 μM (SACNs0), 5 μM (SACNs5), 10 μM (SACNs10), 20 μM (SACNs20), and 40 μM (SACNs40). Following a standard freezing procedure, sperm quality and kinematic parameters significantly improved in the SACNs10, SACNs20, and SACNs40 groups, with the greatest improvement in the SACNs40 group (p < 0.05). Acrosome integrity was significantly improved in all SACNs-treated semen samples compared with the SACNs0 treatment (p < 0.05). Additionally, total antioxidant capacity and catalase activity were improved, while hydrogen peroxide and MDA levels were noticeably diminished in all SACNs-treated groups (p < 0.05). Although all SACNs concentrations markedly reduced apoptotic markers, caspase-3 activity, and reactive oxygen species, it showed the lowest levels in the SACNs40 group (p < 0.05). Salicylic acid exhibited strong docking interactions with key regulators of mitochondrial function and sperm motion, including UCP1, HSP70, cytochrome c, and the tubulin-colchicine complex, suggesting a multi-target mechanism of action. Furthermore, supplementation with SACNs at 10, 20, and 40 μM significantly declined coliform and total bacterial counts compared with the SACNs0 treatment (p < 0.05). These findings show that SACNs, acting as nano-antioxidant additives, enhance the cryoresistance of buffalo sperm, suggesting their potential to improve assisted reproductive technologies.
Sperm acquire fertility ability during epididymal maturation mainly in the epididymal caput and corpus, and once matured, are stored in the epididymal cauda. During storage, interactions with cauda epididymosomes (epEVs) may influence sperm fertility potential; however, the role of such interactions on sperm fertility remains elusive. To investigate the effect of epEVs on sperm fertility potential using the bovine model. A pool of epEVs from cauda epididymal fluid of five bovine males was characterized regarding size, concentration, morphology, and specific markers. To determine the sperm-epEVs interaction protocol, green-labeled epEVs (PKH67) were incubated with post-thawed cauda epididymal sperm from three bovine males at ratios of 500, 1000, or 2000 epEVs/sperm, and for incubation periods of 1.5, 3, or 6 h. After that, Hoechst-stained sperm were analyzed by flow cytometer. Green fluorescence percentage and intensity of 5000 positive Hoechst events were considered as sperm-epEVs interacting. Controls were performed by incubating sperm with PKH67 in PBS. A total of 49 microRNAs (out of 380 investigated) were found detected in the epEVs and the top five were investigated in sperm by quantitative polymerase chain reaction (qPCR) following sperm-epEVs interaction. Subsequently, sperm that interacted with epEVs were used to produce embryos by in vitro fertilization. epEVs displayed 114.20 ± 3.60 nm, 3.48 × 109 ± 1.84 × 108 particles/mL, a cup-shaped morphology, and positivity for ALIX, CD-81, and CD-63 markers. Following determination of the protocol (1000 epEVs/sperm for 3 h), two microRNAs (miR-935 and -421) previously detected in epEVs, were found in sperm. Finally, sperm incubated with epEVs resulted in higher (p = 0.04) blastocyst rates (epEVs: 38.9% ± 7.3%; 58/149; control: 26.6% ± 5.6%; 40/145). Incubation of sperm with 1000 epEVs/sperm for 3 h promoted sperm-epEVs in vitro crosstalk that enhanced blastocyst rates. These findings suggest that epEVs modulate paternal contribution to development and provide valuable insights to promote a fast and dynamic control of male fertility.
The corpus luteum (CL) is a transient endocrine gland responsible for progesterone synthesis, and its proper function depends on coordinated regulation of angiogenesis, proliferation, apoptosis, and autophagy. Spexin (SPX), a pleiotropic neuropeptide/adipokine acting via galanin receptors (GALR2/GALR3), has recently been implicated in CL physiology; however, its role in luteal-cell survival and vascular regulation remains unclear. In this study porcine luteal cells were treated with SPX (0.1-10 nM) for 24 and 48h. Angiogenic, apoptotic, and autophagy-related markers were evaluated at the mRNA and protein levels, together with cell viability, proliferation and autophagosome formation. The role of signalling pathways involved in SPX action was examined using pharmacological inhibition of GALR2 receptor and MAP3/1, AKT, and STAT3 kinases. The results demonstrated that SPX increased VEGFA secretion and VEGFA mRNA expression, elevated VEGFR1, and decreased FGFR2 protein and reduced iNOS secretion. Luteal-cell viability decreased after 48 h at 10 nM of SPX, and proliferation declined at all doses, with reduced PCNA protein at doses 0.1 and 1 nM. Apoptotic signalling was enhanced, as shown by increased BAX and CASP3 and decreased BCL2 mRNA and protein levels. SPX also stimulated autophagosome formation, increased beclin-1 level and elevated LC3 protein. These effects on VEGFA, BECN1 mRNA expression and luteal cell viability were mediated via GALR2, MAP3/1, AKT, and STAT3 pathways. Collectively, these findings identify SPX as a novel regulator of key processes involved in CL remodeling and luteal homeostasis, including markers of angiogenesis, apoptosis, and autophagy.
Age at first calving (AFC) is an important indicator of reproductive efficiency in beef cattle. Studies that simultaneously estimate genetic parameters for reproductive traits and neonatal performance in Zebu populations are still scarce. This study aimed to estimate variance components and genetic parameters for AFC, calving interval (CI), longevity (LONG), productive life (PL), neonatal vigor (VIG), and pre-weaning mortality (MT) in Nellore cattle. Data from 33,445 animals were analyzed, with a pedigree of 67,970 animals and genotypes of 2623 individuals evaluated using a medium-density SNP panel. Single-trait linear and threshold animal models and two-trait models were fitted using Bayesian inference. The posterior heritability estimates were 0.19 ± 0.03 for AFC, 0.13 ± 0.02 for CI, 0.23 ± 0.03 for LONG, 0.17 ± 0.03 for PL, 0.31 ± 0.07 for VIG, and 0.14 ± 0.04 for MT, indicating low heritability for most traits, except for VIG, but with sufficient genetic variability to allow selection response. Posterior estimates of genetic correlation coefficients between AFC and the other traits were 0.35 ± 0.13 (AFC-CI), -0.27 ± 0.11 (AFC-LONG), -0.28 ± 0.15 (AFC-PL), -0.19 ± 0.16 (AFC-VIG), and 0.47 ± 0.13 (AFC-MT), indicating that females with a lower AFC tend to have shorter first calving intervals, remain productive in the herd for longer, and produce calves with lower mortality before four months of age. These results pointed out that management and selection strategies aimed at reducing age at first calving may contribute to more efficient and economically sustainable production systems.
Ovarian stimulation using exogenous follicle-stimulating hormone may enhance follicular recruitment; however, in the context of artificial insemination, it does not substantially improve pregnancy rates. Moreover, such physiological stimulation may impair oocyte developmental competence. To investigate the underlying metabolic mechanisms, the present study employed targeted metabolomics to compare the amino acid profiles in the follicular fluid of dairy cows during the natural estrous cycle (control group) and following ovarian stimulation (treated group). In total, 21 differentially abundant amino acids were identified: 7 were significantly upregulated, and 14 were significantly downregulated in the treatment group. Among the downregulated amino acids, L-serine was identified as a candidate hub metabolite via network analysis. Kyoto Encyclopedia of Genes and Genomes pathway enrichment analysis revealed that these differentially abundant amino acids were primarily enriched in the metabolic pathways of glycine, serine, and threonine, as well as in monocyclic lactam and arginine biosynthesis. Supplementation with 25-μM L-serine in the in vitro maturation medium significantly improved the oocyte maturation rate, cleavage rate, and blastocyst rate of oocytes from dairy cows undergoing ovarian stimulation. Additionally, supplementation promoted cumulus cell expansion and reduced the apoptosis rate of the formed blastocyst cells. The in vitro culture of bovine granulosa cells further demonstrated that L-serine could significantly promote cell proliferation and increase the estradiol to progesterone ratio (E2/P4). Real-time quantitative PCR analysis revealed that L-serine significantly upregulated the mRNA expression of key functional genes, including aromatase (CYP19A1), steroidogenic acute regulatory protein (STAR), and proliferating cell nuclear antigen (PCNA). These findings suggest a potential role for L-serine in supporting oocyte and embryo development, offering metabolic insights for further optimization of ovarian stimulation protocols.