Search

Contents Strategic supplementation of P4 may be used to increase conception rates in cattle, but timing of supplementation in relation to ovulation, mass of supplementary P4 and formulation of the P4-containing supplement has not been determined for beef cattle. Effects of supplementation of long-acting progesterone ( P4) on Days 2 or 3 post-ovulation on development, function and regression of corpus luteum ( CL) were studied in beef cattle. Cows were synchronized with an oestradiol/ P4-based protocol and treated with 150 or 300 mg of long-acting P4 on Day 2 or 3 post-ovulation (6-7 cows/group). Colour- doppler ultrasound scanning and blood sample collection were performed from Day 2-21.5. Plasma P4 concentrations were greater (p < 0.05) from Day 2.5-5.5 in the Day 2-treated groups and from Day 3.5-5.5 in the Day 3-treated cows than in the control group. CL area and blood flow during Day 2-8.5 did not differ (p > 0.05) among groups, suggesting no effect of P4 treatment on luteal development. The frequency of cows that began luteolysis before Day 15 was greater (p < 0.04) in cows treated with 300 mg than in the controls, but there were no differences between non-treated and 150 mg-treated cows. The interval from pre-treatment ovulation to functional and structural luteolysis was shorter (p < 0.01) in the combined P4-treated groups than in the control cows. In conclusion, was showed for the first time that long-acting P4 supplementation on Day 2 or 3 post-ovulation increases P4 concentrations for ≥3 day, has no effect on luteal development, but anticipates the beginning of luteolysis in beef cattle. [ABSTRACT FROM AUTHOR]

Transitioning from a fossil-based to a bio-based economy is crucial to climate action and achieving neutrality in greenhouse gas (GHG) emissions. Biofuel production is an essential land-based GHG mitigation alternative. However, it raises concerns about biodiversity conservation, competition with food production, and net GHG emissions associated with direct land-use change (dLUC). This study aims to assess how the location and conversion routes influence GHG emissions for sugarcane expansion in Brazil to supply ethanol demand projections for 2030. A consistent and significant reduction in GHG emissions is achievable by implementing a strategy that prioritizes the spatial distribution for ethanol biorefinery expansions based on georeferenced life cycle emissions, including dLUC emissions associated with sugarcane production. Because of conservative zoning for sugarcane expansion, dLUC emissions are not an overriding factor, representing less than 9.1 % of the total GHG mitigation potential. Despite that, accounting for georeferenced dLUC emissions when prioritizing expansion facilities leads to spatial differences. Regarding conversion routes and land requirements, using cellulosic biorefineries could meet future projected demand based on sugarcane production from 3.1 million hectares, mostly in currently degraded pastureland. Conventional refineries would require 5.5 million hectares to meet the same demand of 71 billion liters. Despite the 77 % higher land demand to produce the same volume of ethanol, conventional refineries with straw recovery could be considered if electricity generation is a priority. This study illustrates how Brazil can achieve GHG mitigation targets while attending to future energy demand and protecting areas with high biodiversity., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Alongside the concerns of waste management, plastic production represents a future problem for managing greenhouse gas emissions. Advanced recycling and bio-based production are paramount to face this challenge. The sustainability of bio-based polyethylene (bioPE) depends on the feedstock, avoiding stress on natural resources. This work discusses Brazil's potential to meet future global bioPE demand by 2050, using sugarcane as feedstock and considering environmental sustainability for production expansion. From the assessed 35.6 Mha, 3.55 Mha would be exempt from trade-offs related to land use change (dLUC), biodiversity, and water availability. The scenario with the highest circularity efficiency would require 22.2 Mha to meet the global demand, which can be accommodated in areas with positive impacts in carbon stocks, neutral impacts in water availability, and medium impacts on biodiversity. Here, we show that dropping demand is essential to avoid trade-offs and help consolidate bioPE as a sustainable alternative for future net-zero strategies., (© 2024. The Author(s).)

This study aimed to evaluate the feasibility of performing multiple testicular biopsies in rams using Tru-cut® needles, assessing histological structure, gene expression, and potential complications such as effects on semen quality, testicular blood flow, and ultrasonographic echotexture. In Exp. 1, six mature rams underwent testicular biopsies at intervals (0, 3, 6, 12, 24, and 48 h) using a 16 G Tru-cut® needle, with alternating testes for each collection. Benzathine benzylpenicillin and flunixin meglumine were administered for infection and inflammation control. Local anesthesia and post-biopsy care included lidocaine, digital pressure, and ice application. Testicular samples were analyzed for gene expression related to inflammation, oxidative stress, and steroidogenesis. Semen quality was assessed pre-biopsy and 28 days post-biopsy. Ultrasonographic evaluations of the scrotum and testes were conducted before biopsies and on days 5, 9, 13, 17, and 21 post-biopsies. In Exp. 2, a second group of six mature rams underwent biopsies using 14 G needles, with two samples taken from each testis. Samples were histologically examined for structural preservation. Scrotal skin temperature was measured using infrared thermography, and testicular blood flow was assessed via color Doppler ultrasonography, with measurements taken before and on days 1, 2, 4, 6, 8, 10, 25, 50, 75, and 100 post-biopsies. Semen collection followed the same schedule as in Exp. 1. In Exp. 3, biopsies were performed on different testicular regions (upper, middle, lower) using 12 G, 14 G, and 16 G needles to compare structural preservation. Samples were histologically analyzed. No clinical signs of injury, inflammation, or fluid accumulation were observed. Scrotal pain, increased temperature, swelling, and bleeding were absent, and behavioral signs indicative of pain were not detected. Gene expression remained unchanged, and no significant alterations in seminal characteristics or testicular echogenicity were observed. A slight increase in resistivity and pulsatility indices was noted in Exp. 2. Biopsies with 14 G and 16 G needles resulted in structural disruptions, while 12 G needles better preserved testicular parenchyma. Multiple testicular biopsies using Tru-cut® needles did not cause significant morphological changes, alter transcriptional profiles, or affect semen or ultrasonographic characteristics, demonstrating that this method is viable for monitoring acute molecular changes in the testes., Competing Interests: Declaration of competing interest The authors declare that no conflict of interest could be perceived as prejudicing the impartiality of the research reported., (Copyright © 2024 Elsevier Inc. All rights reserved.)

The increasing use of plastics in rural environments has led to concerns about agricultural plastic waste (APW). However, the plasticulture information gap hinders waste management planning and may lead to plastic residue leakage into the environment with consequent microplastic formation. The location and estimated quantity of the APW are crucial for territorial planning and public policies regarding land use and waste management. Agri-plastic remote detection has attracted increased attention but requires a consensus approach, particularly for mapping plastic-mulched farmlands (PMFs) scattered across vast areas. This article tests whether a streamlined time-series approach minimizes PMF confusion with the background using less processing. Based on the literature, we performed a vast assessment of machine learning techniques and investigated the importance of features in mapping tomato PMF. We evaluated pixel-based and object-based classifications in harmonized Sentinel-2 level-2A images, added plastic indices, and compared six classifiers. The best result showed an overall accuracy of 99.7% through pixel-based using the multilayer perceptron (MLP) classifier. The 3-time series with a 30-day composite exhibited increased accuracy, a decrease in background confusion, and was a viable alternative for overcoming the impact of cloud cover on images at certain times of the year in our study area, which leads to a potentially reliable methodology for APW mapping for future studies. To our knowledge, the presented PMF map is the first for Latin America. This represents a first step toward promoting the circularity of all agricultural plastic in the region, minimizing the impacts of degradation on the environment., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

The objective of this study was to verify the causes of the lower response of primiparous Bos indicus cows to the ovulation synchronization protocol. Two experiments were performed to evaluate the biochemical profile, oocyte and follicular cell quality (Experiment 1) and pregnancy (Experiment 2). In Experiment 1, suckled primiparous (n = 24) and multiparous cows (n = 24) were submitted to ovum pick up (OPU). On Day 0 (D0), all cows received 2 mg of estradiol benzoate (EB) and an intravaginal progesterone insert (P4). Five days (D5) after the first hormonal administration (EB + P4), all follicles larger than 3 mm were counted on each ovary, and ovum pick-up (OPU) was performed. On day 12 (D12), the intravaginal progesterone insert was removed, and measurement and aspiration of the largest follicle were performed. Blood samples were collected on D5 and D12 to evaluate the concentrations of glucose, cholesterol, NEFA, IGF-1 and insulin. In Experiment 2, suckled primiparous (n = 50) and multiparous (n = 50) cows were subjected to an ovulation synchronization protocol based on E2/P4 (D0: 2 mg EB plus P4 intravaginal insert; D8: 500 μg of cloprostenol, 1 mg cypionate estradiol and 300UI of eCG; D10: artificial insemination). In addition, blood samples were collected on D10 for evaluation of the same hormones and metabolites described in Experiment 1. In all studies, calves remained with the cows during the experimental period. In experiment 1, the number of oocytes grade 1 (P = 0.83), grade 2 (P = 0.23) and grade 3 (P = 0.51), total number of retrieved oocytes (P = 0.14), oocyte quality index (P = 0.93) and total viable oocytes (P = 0.38) did not differ between primiparous and multiparous cows. The number of follicles at the time of follicular aspiration (20.7 ± 1.5 vs. 18.0 ± 1.9; P = 0.05) and the diameter of the largest follicle on D12 (13.5 ± 0.6 vs. 11.4 ± 0.6; P = 0.04) were greater in multiparous cows, and the number of degenerated oocytes was greater in primiparous cows (1.9 ± 0.7 vs. 1.2 ± 0.3; P = 0.05). On D5, the concentrations of IGF-1 (P = 0.47), insulin (P = 0.08), total cholesterol (P = 0.47), NEFA (P = 0.77) and glucose (P = 0.55) in the blood and IGF-1 (P = 0.97) and insulin (P = 0.11) in the follicular fluid did not differ between parity groups. On D12, there was no difference in the concentrations of IGF-1 (P = 0.26), total cholesterol (P = 0.32), NEFAs (P = 0.31) and glucose (P = 0.93) in the blood between primiparous and multiparous cows, however, the serum insulin concentration (P = 0.04) was higher in primiparous cows. There was no correlation between serum and follicular fluid insulin concentrations (r = 0.17; P = 0.31), however, there was a low correlation between serum and follicular fluid IGF-1 concentrations (r = 0.47; P = 0.002). Quantification of transcripts did not differ between parity groups. In experiment 2, concentrations of NEFA (P = 0.12) and insulin (P = 0.16) in the blood and P/AI (P = 0.93) did not differ between parity [60 % (30/50) primiparous vs. 60 % (30/50) multiparous]. In contrast, blood concentrations of IGF-1 (P = 0.0001), total cholesterol (P = 0.005) and glucose (P = 0.01) were greater in primiparous cows. It was concluded that the oocyte quality and expression of the genes evaluated in the granulosa cells were not different between primiparous and multiparous cows. Unexpectedly, the pregnancy rate did not differ between parity. Nevertheless, the blood concentrations of IGF-1, total cholesterol and glucose were greater in primiparous cows., (Copyright © 2024 Elsevier Inc. All rights reserved.)

Epidemiological data on the distribution of oral and maxillofacial diseases present in early childhood are scarce in the literature. This study analyzed the frequency of lesions biopsied in this region in children aged 0 to 3 years and sent for histopathological analysis in a reference oral pathology laboratory . Histopathological diagnostic data, lesion location, sex, and age were collected. Of the total of 93,950 records, 250 cases (0.27%) belonged to the age group from 0 to 3 years old. The most frequently diagnosed oral alterations were: mucocele (34/250; 13.6%); papilloma (11/250; 4.4%), giant cell fibroma (6/250; 2.4%), pyogenic granuloma (5/250; 2%) and hemangioma (3/250; 1.2%). The lip was the most affected site, followed by the gingiva and the tongue. These results generate information on the lesions most frequently diagnosed in early childhood, which facilitates the process of diagnosis and, consequently, treatment., (© 2023 Wiley Periodicals LLC.)

Indicine and taurine subspecies present distinct morphological traits as a consequence of environmental adaptation and artificial selection. Although the two subspecies have been characterized and compared at genome-wide level and at specific loci, their epigenetic diversity has not yet been explored. In this work, Reduced Representation Bisulphite Sequencing (RRBS) profiling of the taurine Angus (A) and indicine Nellore (N) cattle breeds was applied to identify methylation differences between the two subspecies. Genotyping by sequencing (GBS) of the same animals was performed to detect single nucleotide polymorphisms (SNPs) at cytosines in CpG dinucleotides and remove them from the differential methylation analysis. A total of 660,845 methylated cytosines were identified within the CpG context (CpGs) across the 10 animals sequenced (5 N and 5 A). A total of 25,765 of these were differentially methylated (DMCs). Most DMCs clustered in CpG stretches nearby genes involved in cellular and anatomical structure morphogenesis. Also, sequences flanking DMC were enriched in SNPs compared to all other CpGs, either methylated or unmethylated in the two subspecies. Our data suggest a contribution of epigenetics to the regulation and divergence of anatomical morphogenesis in the two subspecies relevant for cattle evolution and sub-species differentiation and adaptation.

Although the use of different estradiol esters has been extensively studied in hormonal protocols in cows, such information is lacking in mares. The present study aimed to assess the effects of treatment with the same doses and administration frequency of estradiol cypionate, estradiol benzoate and 17β estradiol on plasma estradiol (E2) concentrations of acyclic mares and correlate the E2 profile to the endometrial edema score. Sixteen treatments were performed in 14 mares randomly divided into three groups: EB (n = 5), EC (n = 5), and 17β (n = 6), receiving 10 mg on day 0 (D0), 6 mg on D1, and 4 mg on D2 of estradiol benzoate, estradiol cypionate, and estradiol 17β, respectively. Blood samples, rectal palpations, and ultrasound evaluations were performed once daily, starting before the first estradiol treatment (D0) until edema disappearance or D8. Moderate to high edema was observed in all groups 24 hours after the first estradiol administration. Edema persisted above score 2 until D7, D5, and D4 in groups EC, EB, and 17β, respectively. Higher edema was found on D2 in EB group compared to 17β, on D6 and D7 in EC compared to 17β, and on D8 in EC compared to EB (p ≤ .05). Maximum E2 concentrations were detected on D1 in groups: EB, showing a sharp decrease from D2 to D3 (p < .0001); and 17β, where no differences were observed between treatment days (p ≥ .05). In the EC group, maximum concentrations were observed on D2, which remained high from D2 to D4 compared to the other days (p < .0001). Plasma concentration of E2 was higher in EB than the other groups on D0 and D1, and EB>EC>17β on D2. Plasma E2 concentrations and edema score were positively correlated, being moderate in groups EB and EC and weak in the 17β group. In conclusion, the most pronounced plasma E2 concentration was observed in EB group 24 hours after the administration of the first dose. Estradiol concentrations peaked 48 hours after EC administration, while a distinct peak was not observed in a 24h interval evaluation in the 17β group. Moreover, high edema does not necessarily reflect on high E2 concentrations in acyclic mares., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

This study aimed to determine the effect of growth rates on the hormonal status and puberty onset. Forty-eight Nellore heifers were weaned at 3.0 ± 0.1 (means ± standard error of the mean) months old were blocked according to body weight at weaning (84 ± 2 kg) and randomly assigned to treatments. The treatments were arranged in 2 × 2 factorial according to the feeding program. The first program was high (H; 0.79 kg/day) or control (C; 0.45 kg/day) average daily gain (ADG) from 3 rd to 7 th month of age (growing phase I). The second program was also high (H; 0.70 kg/day) or control (C; 0.50 kg/day) ADG from the 7 th month until puberty (growing phase II), resulting in four treatments: HH (n = 13), HC (n = 10), CH (n = 13), and CC (n = 12). To achieve desired gains, heifers in high ADG program were fed ad libitum dry matter intake (DMI), and the control group was offered around 50% of ad libitum DMI of high group. All heifers received a diet with similar composition. Puberty was assessed weekly by ultrasound examination, and the largest follicle diameter was evaluated every month. Blood samples were collected to quantify leptin, insulin growth factor-1 (IGF1) and luteinizing hormone (LH). At 7 months of age, heifers in high ADG were 35 kg heavier than the control. Heifers in the HH had greater DMI compared with CH in phase II. The puberty rate at 19 months old was greater in the HH treatment (84%) than in the CC (23%), but there was no difference between HC (60%) and CH (50%) treatments. Heifers from HH treatment had greater serum leptin concentration than others at 13 months old, and serum leptin was greater in HH compared with CH and CC at 18 months old. High heifers in phase I had greater serum IGF1 concentration than the control. In addition, HH heifers had a greater diameter of the largest follicle than CC. There was no interaction between phases and age in any variable relative to the LH profile. However, the heifers' age was the main factor that increased the frequency of LH pulse. In conclusion, increasing ADG was associated with greater ADG, serum leptin and IGF-1 concentration, and puberty onset; however, LH concentration was affected mainly by age of the animal. The increasing growth rate at younger age made heifers more efficient., (© 2023. The Author(s), under exclusive licence to Springer Nature B.V.)

Buckwheat ( Fagopyrum esculentum Moench) belongs to the Polygonaceae family and has been widely cultivated due to its high nutritional, nutraceutical, and medicinal properties. Brazil ranks seventh-largest producer, with 66,000 tons produced in 2018. Buckwheat is also valued for its adaptability as a cover crop, in grain fields of soybean ( Glycine max (L.) Merr., maize ( Zea mays L.), and sorghum ( Sorghum bicolor (L.) Moench) (Görgen et al. 2016, Babu et al. 2018) especially in fields highly infested with plant-parasitic nematodes (PPN). PPN cause severe root damage, suppressing plant development and yield production. In October 2018, six samples of roots and soil were collected in symptomatic patches of buckwheat, in Guaíra SP (20° 19' 32"S 48° 13' 15.4"W). Samples were analyzed in the Nematology Laboratory (LabNema), UNESP, Jaboticabal, SP, BR. Plants presented symptoms of yellow leaves and galled and volume-reduced roots. Meloidogyne sp. was found, comprising 6,320 eggs and second-stage juveniles (J2s) from 10 g of root and 1,628 J2s in 100 cm³ of soil. Adult morphological characteristics, isoenzyme phenotype of esterase, and molecular analysis were performed to identify the Meloidogyne species. The perineal patterns presented high and trapezoidal dorsal arch (n=15), and the males showed a trapezoidal labial region, including a high head cap formed by a large round labial disc that is raised above the medial lips and centrally concave (n=15) (Eisenback and Hirscmann 1981). These characteristics are typical in Meloidogyne incognita (Kofoid and White, 1912) Chitwood, 1949 (Nascimento et al., 2020; Eisenback and Hirschmann 1981; Netscher and Taylor 1974). The enzymatic phenotype was performed with females (n=8), and the phenotype I1 was verified, described by Esbenshade and Triantaphyllou (1985) as typical for M. incognita . To confirm the species DNA samples were extracted from individual females (n=6) and PCR with specific primers for M. incognita ( Mi -F 5'- GTGAGGATTCAGCTCCCCAG-3' and Mi -R 5'-ACGAGGAA CATACTTCTCCGTCC-3') and M. javanica (Treub) Chitwood 1949 (Fjav 5'-GGTGCGCGATTGAACTGAGC-3' and Rjav 5'-CAG GCCCTTCAGTGGAACTATAC-3') that amplify SCAR markers described by Meng et al. (2004) and Zijlstra et al. (2000), respectively, and specific primers for M. enterolobii Yang & Eisenback 1983 that amplify rDNA-IGS2 region ( Me -F 5'-AACTTTTG TGAAAGTGCCGCTG-3' and Me -R 5'-TCAGTTCAGGCAGG ATCAACC-3') described by Long et al. (2006) were tested. A fragment of 955 pb DNA size was amplified in Mi -F/R primer, which confirmed the M. incognita identification (Meng et. al., 2004). The original population was used to execute pathogenicity test. In a greenhouse, single buckwheat seeds (cv. IPR 91 Baili) were sown in six 5L pots filled with autoclaved-soil and inoculated with 3,000 eggs and J2s per pot (n=6) and control (n=6). After 60 days, the nematodes were extracted from roots and the M. incognita was confirmed. An average of 15,738 eggs and J2s were recovered, (reproductive factor = 5.24), which confirmed buckwheat as a host to M. incognita . The inoculated plants showed symptoms as those observed in the field. No symptom or nematode was noted on the control. Meloidogyne incognita has been reported causing high damage to the F. esculentum in California (Gardner and Caswell-Chen 1994) plus several crops in Brazil (Nascimento et al., 2020). However, this is the first report of this nematode infecting buckwheat in Brazil. Given the importance of buckwheat in Brazil, with extensive use as forage, cover crop, and its nutritional properties, this report is essential to specific management measures are adopted to avoid further losses.

In cattle, uterine luminal fluid (ULF) is the main source of molecules that support embryo development and survival during the peri-implantation period. Our overarching hypothesis is that peri-estrus changes in uterine function, including ULF accumulation and absorption, are uneven among individuals, and affect ULF composition and fertility. Our objectives were (1) to characterize temporal and spatial changes in ULF volume, endometrial and luteal blood perfusion, endometrial and luteal size, and circulating progesterone concentrations during the peri-estrus period in beef heifers and (2) to associate such changes with the metabolite composition in the ULF, 4 days after estrus (d 0). Fourteen Bos indicus heifer that presented a PGF2α responsive CL received 500 μg PGF2α analog i.m. and were examined daily by rectal B-mode and pulse-wave color-Doppler ultrasonography until the fifth day after estrus (d 5). The composition of the ULF was analyzed by targeted mass spectrometry on d 4. Multivariate analyses clustered heifers according to ovarian, uterine, and hormonal variables in clusters A (n = 5) and B (n = 8 heifers). Concentrations of Pro, Ala, Leu, Gly, Val, Lys, Ile, Phe, Asp, Orn, Tyr, Arg, Trp, Suc, Cit, ADMA, the sum of essential Amino Acids (AA), sum of nonessential AA, sum of aromatic AA, and total AA were greater in cluster A (FDR ≤ 0.05). ULF volume dynamics and uterine, ovarian, and hormonal variables during the peri-estrus period presented a concerted variation among heifers within clusters, which was associated with the ULF composition 4 days after estrus., (© The Author(s) 2021. Published by Oxford University Press on behalf of Society for the Study of Reproduction. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

This study investigated the effects of growth rates and compensatory growth on puberty attainment in Nellore heifers. Nellore heifers (n = 120), weaned at 8 ± 0.75 mo of age, were blocked by sire and BW (180 ± 8.6 kg) and assigned randomly to receive 1 of 4 treatments over a 10-mo period. Treatments included ad libitum feeding (high gain, HG), feed intake to gain 0.6 kg/d (medium gain, MG), restricted feeding (0.2 kg/d) for 4 mo followed by ad libitum feeding for 6 mo (compensatory gain, CG), and alternating periods of ad libitum and restricted feeding for 2 mo each throughout the trial (alternated CG, ACG). Puberty was assessed weekly by transrectal ultrasonography. Blood samples were collected at 8, 11, and 18 mo of age and at puberty to determine circulating concentrations of leptin. At 18 mo of age, nonpubertal heifers were treated with a puberty induction protocol using an intravaginal progestin device. There was no treatment effect (P = 0.17) on the percentage of heifers pubertal by 18 mo of age (HG: 66, MG: 40, CG: 58, and ACG: 52%), BW at puberty, and age at puberty. However, HG heifers had higher ADG (P < 0.01), dry matter intake (P < 0.01), and leptin concentrations (P = 0.03) than heifers from other groups. The response to the puberty induction protocol was similar (P = 0.90) among treatments. Regarding sire effects (genetic effects), there was an effect (P = 0.03) on the percentage of heifers pubertal by 18 mo of age and a tendency (P = 0.07) of sire effect in response to the puberty induction protocol. Compensatory growth appears to be an effective managerial approach to decrease feeding costs and stimulate puberty in Nellore heifers., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Insulin-like growth factor 1 (IGF-1) activity is established by the regulation of IGF binding protein activity, which blocks IGF-1 functions, whereas pregnancy-associated plasma protein-A (PAPP-A) improves IGF-1 bioavailability and facilitates binding to IGF receptors. To further extend our understanding of the effect of exogenous PAPP-A on bovine embryo production, we added this protein during in vitro maturation of cumulus-oocyte complexes (COCs); moreover, we assessed its effects on IGF-1 quantity in the maturation medium, embryonic yield and postwarming survival, blastocyst quality, and transcript abundance. Bovine COCs were matured in a serum-free medium, either with PAPP-A supplementation (100 ng/ml) or without (control). The treatment group produced higher IGF-1 concentrations in the maturation medium; however, showed no difference on cleavage, blastocysts rates, and embryonic survival 3 and 24 hr postcryopreservation. Regarding gene expression, VNN1 was upregulated, whereas AGPAT9, FASN, EGFR, HAS2, and IMPDH1 were downregulated in PAPP-A treated. PAPP-A treated, CPT2, DNMT3A, and TFAM were upregulated, whereas ATF4 and IFITM3 were downregulated. We concluded that although the addition of PAPP-A did not affect embryo yield and blastocyst survival, higher IGF-1 levels may affect embryo competence through differential expression of genes involved in lipid metabolism, oocyte competence, and mitochondrial function., (© 2019 Wiley Periodicals, Inc.)

To evaluate the effects of moderate dietary restriction and lipid supplementation on ovarian follicular development, hormonal and metabolic profile, thirty-five prepuberal ewe lambs were blocked by body weight and randomly assigned to treatments: ALUS (control) - unsupplemented-diet ad libitum (3.5% ether extract, n = 9); R-US - intake restricted to 85% of the ALUS diet (n = 9); AL-LS - lipid-supplemented-diet ad libitum (9.8% ether extract, n = 8); R-LS - intake restricted to 85% of the ALLS diet (n = 9), from 95 ± 8 days of age until estrus or 7 months of age. Lipid supplementation did not reduce dry matter intake. Daily weight gain was greater in lambs fed ad libitum. Plasma glucose was greater in the RLS treatment group, while serum insulin was less with lipid supplementation. There was a treatment by age interaction on total cholesterol, HDL cholesterol and triglyceride serum concentrations. Estrus was detected in 43% of the animals and the overall ovulation rate was 60%. The number of follicles, diameter of the largest follicle, body weight, age and serum progesterone at puberty did not differ among treatment groups. The mean diameter of the largest follicle was greater in lambs having than in those not having ovulations and increased with age in both groups. There was an interaction between the effects of occurrence of ovulation and age on the number of follicles between 3 and 5 mm and > 5 mm. Lipid supplementation and dietary restriction altered the metabolic profile in ewe lambs with no concomitant changes in values for reproductive variables., (Copyright © 2019 Elsevier B.V. All rights reserved.)

The main objective of this study was to evaluate the effect of intramuscular (I.M.) administration of different doses of kisspeptin (Kp) on the pattern of luteinizing hormone (LH) release in Bos taurus and Bos indicus prepubertal heifers. Holstein heifers weighing 215.1 ± 38.6 kg (n = 24; aged 5-8 mo) and Gyr heifers weighing 215.4 ± 31.4 kg (n = 24; aged 6-10 mo) were enrolled in this study. The animals were confirmed as non-cyclical by absence of a corpus luteum (CL) as determined by ultrasound scanning of the ovaries and low circulating P4 concentrations (<1.0 ng/mL) evaluated at a 10-day interval (on day -10 and day 0). For each genetic group, heifers were randomly assigned to one of four treatments: Kp at 2.5 μg/kg body weight (Kp2.5), Kp at 5.0 μg/kg (Kp5), Kp at 10 μg/kg (Kp10), or gonadotropin-releasing hormone (GnRH) agonist (0.01 mg of buserelin acetate per heifer), all administered by I.M. injection. All animals responded to the treatments with an LH surge (P < 0.01). There was an effect of breed (P < 0.01) on induced LH release, with Holstein heifers having a greater area under the curve for LH (AUC; P < 0.01) and greater LH peak amplitude (P < 0.01) than Gyr heifers. Nevertheless, greater AUC for LH occurred in Kp10 heifers for both breeds. There was no effect of breed on LH AUC or LH peak amplitude after GnRH agonist treatment. For both breeds, heifers treated with Kp displayed an earlier (P < 0.01) LH peak with a reduced amplitude of the LH peak (P < 0.01) and reduced LH AUC (P < 0.01) compared to heifers treated with GnRH agonist. Thus, both zebu and taurus immature heifers treated with I.M. Kp injection responded with a rapid and dose-dependent LH surge, although even large doses of the native Kp-10 did not mimic the magnitude or duration of the LH surge produced by the GnRH agonist. The early onset of the LH surge after Kp treatment and the short duration suggest that the effects of Kp were likely due to pituitary rather than hypothalamic action. Finally, there seems to be a greater responsiveness to Kp in Bos taurus than in Bos indicus prepubertal heifers, although LH release after GnRH agonist treatment was similar for the two breeds., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Antral follicular population (AFP) and anti-Müllerian hormone (AMH) concentration are strongly associated. Thus, analyzing AMH concentration is a reliable method to predict animals with high AFP, an important feature to select donor cows for embryos and oocytes. However, not much is known about this parameter in heifers, particularly in crossbred animals. The aim of this study was to assess AFP in heifers and cows and its relation to serum AMH levels. Bos taurus indicus cows (36-60-months-old; n = 30) and heifers (12-14-months-old; n = 17) of the same breed were evaluated. A single procedure of follicular counting was performed by ultrasound for each animal. Random sampling was performed to analyze serum AMH concentration. Cows showed higher AFP than heifers; nonetheless, plasma AMH concentration did not differ between the categories. A high correlation of AFP with plasma AMH concentration was observed in Girolando heifers. Thus, it is suggested that AMH concentration could be a reliable and less invasive method for selecting heifers with high AFP.

Nelore heifers usually begin their reproductive life at ⩾24 months of age mainly due to suboptimal nutritional conditions and genetics. This study aimed to determine the effect of expected progeny difference (EPD) for age at first calving and average daily gain (ADG) on puberty in Nelore (Bos taurus indicus) heifers. A total of 58 weaned heifers (initial BW=174±6 kg; age=9±1 months) were allocated into 28 feedlot pens. Heifers were born from four sires, of which two had low EPD for age at first calving (L; n=33) and two had high EPD for age at first calving (H; n=25). Then, heifers of each EPD were randomly assigned to high ADG (HG; 0.7 kg) or low ADG (LG; 0.3 kg), resulting in four treatments: heifers from L sires were submitted to either HG (LHG; n=17) or LG (LLG; n=16), and heifers from H sires were submitted to either HG (HHG; n=12), or LG (HLG; n=13). The HG heifers were fed a 75% grain diet, whereas the LG heifers received 93% of forage in their diet. Blood samples were collected at 9, 14, 18, 24 and 28 months of age for IGF1 and leptin determination. There was a treatment effect (P<0.01) on the proportion of heifers that attained puberty by 18 (62%, 0%, 0% and 0%), 24 (100%, 6%, 54% and 0%) or 36 (100%, 100%, 100% and 38%) months of age for LHG, LLG, HHG and HLG treatments, respectively. In addition, mean age at puberty was different across treatments (P<0.01). Heifers from the LHG achieved puberty at the earliest age when compared with cohorts from other treatments (18.1, 28.9, 23.9 and 34.5 months for LHG, LLG, HHG and HLG, respectively). Serum IGF1 concentrations were higher for L heifers compared with H cohorts at 9, 14, 18, 24 and 28 months of age (P<0.01; treatment×age interaction), whereas circulating leptin concentrations were higher (P<0.01; age effect) as heifers became older, regardless of the treatments. In conclusion, only Nelore heifers with favorable genetic merit for age at first calving were able to attain puberty by 18 months of age. In heifers with unfavorable genetic merit for age at first calving, supplementary feeding to achieve high ADG was unable to shift the age at puberty below 24 months.

The objectives of this study were 1) to monitor corpus luteum (CL) dynamics after two different protocols of ovulation induction in prepubertal Nellore heifers, and 2) to determine differences in luteal function. Fifty-seven heifers (weight 289.61 ± 32.28 kg, BCS 5.66 ± 0.65, age 17.47 ± 0.81 months) were divided into two groups: GP4+GnRH received a progesterone (P4) device of 3rd use for 10 days, followed by the administration of 0.02 mg buserelin acetate (GnRH) 48 h after removal of the device, and GGnRH received only GnRH. The CLs formed were monitored by ultrasonography every 2 days until their functional regression (decrease in the color Doppler signal and serum P4 concentration < 1 ng/mL), determining their diameter and area, numerical pixel value (NPV), pixel heterogeneity, and vascularization percentage. The peak systolic velocity, end diastolic velocity, resistivity index and pulsatility index (PI) of the ovarian artery and serum P4 concentration were also measured. A lifespan of the CL of more than 16 days was classified as normal-function and of less than 16 days as premature regression. The variables were compared between treatments, CL categories (normal-functional, prematurely regressed or non-functional), days of evaluation, and their interactions using the MIXED procedure of the SAS program (p ≤ 0.05). Three animals of each group (6/57 = 11%) did not respond to treatment, corresponding to an ovulation rate of 89%. There was a higher percentage of normal-function CLs in GP4+GnRH (81%) and a higher percentage of non-functional CLs in GGnRH (52%; P4 concentration < 1 ng/mL in all assessments). Normal-function CLs exhibited a greater area, vascularization percentage and P4 concentration than prematurely regressed and non-functional CLs. Lower diameter, area, NPV and P4 concentration were observed for non-functional CLs, but there was no difference in vascularization percentage compared to prematurely regressed CLs. Progesterone concentration was efficient in diagnosing CL function and was positively correlated with CL area (r = 0.62; p < 0.001) and vascularization percentage (r = 0.38; p < 0.001). Diameter and PI were important for the early diagnosis of non-functional and prematurely regressed CLs, respectively. In conclusion, luteal function differed for the first CL that develops after ovulation induction in prepubertal heifers. Ultrasonographic parameters (diameter, area, NPV, vascularization percentage, and PI) can be used to predict CL function., (Copyright © 2017 Elsevier Inc. All rights reserved.)

This study evaluated the effects of differing circulating progesterone (P4) levels on the luteinizing hormone (LH) surge profile following treatment with gonadotropin releasing hormone (GnRH) in B. indicus (Nelore, n = 13) and B. taurus (Holstein, n = 16) heifers. All heifers were synchronized with a hormonal protocol to induce either a Low or High circulating P4 environment at the time of GnRH treatment. Heifers were randomly assigned to a 2 × 2 factorial design composed by two genetic groups (B. indicus and B. taurus) and two levels of circulating P4 concentrations (Low or High). Blood samples were collected every 30 min from -30 to 210 min and at 270 min after GnRH treatment. As expected, mean P4 concentration was greater for cows in the High than in the Low P4 group (P = 0.0008) and in Bos indicus than in Bos taurus heifers (P = 0.06). Despite genetic group, the area under the curve of LH release was greater in the Low-P4 than in High-P4 concentration group (P < 0.0001). Interestingly, it appears that High P4 concentrations had a more pronounced effect on LH peak in B. indicus than in B. taurus heifers, as indicated by the interaction (P = 0.01) between genetic group and P4 levels. In conclusion, circulating P4 concentration have a great impact on the GnRH-induced LH surge of both B. indicus and B. taurus heifers, but it does not explain the much lower LH peak in B. indicus with low circulating P4. Thus, more studies are essential to uncover some of the underlying physiological factors other than circulating P4 that are limiting LH release following a GnRH treatment in B. indicus cattle., (Copyright © 2017 Elsevier Inc. All rights reserved.)

In cattle, early diestrus progesterone (P4) supplementation modulates endometrial function to exert pro- and anti-pregnancy establishment effects; specifically, P4 stimulates conceptus growth, but also induces early onset of luteolysis. This paradoxical effect is frequently related to the inconsistent fertility outcomes that result from P4 supplementation experiments. Aim was to investigate the impact of exogenous estradiol (E2) treatment at the end of timed fixed AI (TAI) on frequency of early luteolysis and pregnancy of beef cows supplemented with P4. Ovulations (D0 of study) of suckled multiparous (n = 643) and primiparous (n = 193) Nelore cows (Bos indicus) were synchronized with an E2/P4-based protocol for TAI and assigned to receive 1.0 mg of estradiol cypionate (CP) or nothing (NoCP) on D-2 and 150 mg of injectable long-acting P4 (iP4) or Placebo (NoiP4) on D4 on a 2 × 2 factorial arrangement. On D15, the iP4 supplementation increased (P < 0.05) the frequency of early luteolysis (NoCP + iP4: 26.0%; [13/50] vs. NoCP: 8.0% [4/50]), but CP prevented this effect (CP + iP4: 8.3% [4/48] and CP: 6.4% [3/47]). The CP improved pregnancy/AI (P/AI) of multiparous (CP: 51.6% [165/320] and NoCP: 35.0% [113/323]; P < 0.001) and primiparous cows (CP: 40.4% [40/99] and NoCP: 24.5% [23/94], P < 0.05), regardless of iP4 treatment. The iP4 supplementation affected P/AI of CP and NoCP treated cows according to follicle size at TAI. For the CP treated cows, the iP4 supplementation improved P/AI of sub-populations of cows with follicles <12.35 mm (42.0% [34/81] vs. 53.1% [34/64]), while for NoCP treated cows, the improvements occurred in subpopulations of cows with follicles ≥12.35 mm (46.1% [35/76] vs. 58.7% [37/63]). In conclusion, strategies associating E2 and P4 supplementation decrease the incidence of early onset of luteolysis and improve P/AI of suckled beef cows with smaller follicles., (Copyright © 2017 Elsevier Inc. All rights reserved.)

Tropically adapted Bos taurus breeds are descended from the cattle which were brought from the Iberian Peninsula to Latin America by the colonizers and which adapted over time to local conditions. These breeds have become a genetic treasure that must be preserved. The objective of this study was to characterize ovarian follicular emergence and divergence in tropically adapted B. taurus cows and heifers. Cyclic heifers (n = 11) and nonlactating, multiparous cows (n = 11) were examined at 8-hour intervals using ultrasonography starting on the day following the final application of PGF 2α , which was used to synchronize the estrous cycle, and ending 5 days after ovulation. Blood samples were collected immediately following the ultrasonographic examinations in order to evaluate FSH and estradiol-17β (E 2 ) concentrations. The interval between ovulation and follicular wave emergence (11.6 ± 3.3 hours vs. 20.3 ± 2.5 hours, P < 0.05) and ovulation and follicular wave divergence (52.4 ± 5.2 hours vs. 71.8 ± 4.1 hours, P < 0.05) was shorter in the cows than in the heifers, respectively. Plasma FSH concentrations increased (P < 0.05) and serum E 2 concentrations decreased earlier in cows than in heifers before ovulation. Following follicular wave emergence, no difference in follicular development was found between the cows and the heifers. Consequently, following follicular wave emergence, the data from both the cows and the heifers were combined and categorized by dominant follicle (DF) and second largest follicle (SF). The DF and SF were identified at the same time (P > 0.05). The mean number of small (≤4 mm, 7.2 ± 5.1) and medium (4 to ≤ 8 mm, 6.8 ± 3.5) follicles was greater than that of large follicles (≥8 mm, 0.6 ± 0.5) from ovulation until 5 days after ovulation. The DF diameter (8.1 ± 1 mm) did not differ (P = 0.09) from SF diameter (7.6 ± 0.9 mm) at the time of follicular divergence (around 45 hours after follicular emergence). The DF and SF growth rates were similar (P > 0.05) until follicular divergence, at which point the SF growth rate decreased, whereas the DF growth rate remained constant. Serum E 2 concentrations did not change (P > 0.05) during the divergence period, whereas FSH concentrations decreased between 48 and 32 hours before follicular wave divergence. In conclusion, cows and heifers differed only in the interval from ovulation to follicular wave emergence and divergence, which was confirmed by the different patterns of FSH and E 2 concentrations., (Copyright © 2016 Elsevier Inc. All rights reserved.)

The objectives were to evaluate the effects of the administration of either eCG or progesterone (P4) alone or combined on endogenous P4 concentrations and pregnancy per AI in lactating dairy cows. Cows received a P4-releasing intravaginal device (PRID) and estradiol benzoate on D-8. The PRID was removed and a PGF2α injection was given on D-3. An estradiol cypionate was given on D-2 and TAI was performed on D0. On D-2, cows were randomly allocated to treatments in a 2×2 factorial design: Control-saline solution on the D-2 and D+3 (n=104), eCG - 400IU eCG on D-2 (n=93), P4 - 600mg of P4 on D+3 (n=106), and eCG+P4 - 400IU eCG on D-2 and 600mg of P4 on D+3 (n=95). Blood samples were collected on days three, four, and thirteen and pregnancy diagnoses were performed at 32 and 46 days after AI. There was no interaction between eCG and P4 injection. Cows treated with eCG and with P4 injection had higher serum P4 on Day +4. On Day +13 serum P4 was lower in eCG-untreated primiparous cows (Interaction eCG×parity). Cows with serum P4<4.57ng/mL on Day +13 had lower probability to be pregnant on day 32. P/AI on days 32 and 46 and embryonic losses were not influenced by eCG and P4 injection. In conclusion, the addition of 400IU of eCG on D-2 and/or 600mg of P4 on D+3 to the present TAI protocol did not increase P/AI., (Copyright © 2015 Elsevier B.V. All rights reserved.)

We aimed to evaluate the effect of supplementation with sunflower seed on blood concentrations of progesterone and cholesterol and on the pregnancy rate in beef cattle subjected to timed artificial insemination (TAI) and timed embryo transfer (TET). In experiment 1, cows were received 22-day supplements containing (sunflower, n = 66) sunflower seed or not (control, n = 67) immediately after a progesterone/estradiol-based TAI protocol (Day 0). The cholesterol concentration on Day 21 and the pregnancy rate were greater (P < 0.03) in the sunflower group (148.2 ± 6.1 mg/dL and 66.7%) than those in the control group (116.0 ± 6.4 mg/dL and 47.8%). In experiment 2, heifers received an in vitro-produced embryo 7 days after the expected time of the synchronized ovulation. Heifers were separated into two supplementation groups (sunflower, n = 106 and control, n = 111) for 22 days. The plasma progesterone concentration on Day 7 was not different between the groups. However, on Day 19, the plasma progesterone concentration was greater (P < 0.0001) in the sunflower group (5.8 ± 0.4 ng/mL) than that in the control group (3.5 ± 0.4 ng/mL). A greater (P < 0.05) cholesterol concentration was observed in the sunflower group than that in the control group on Days 7 (306.0 ± 11.6 vs. 277.1 ± 11.9 mg/dL, respectively) and 19 (260.5 ± 8.0 vs. 232.0 ± 8.0 mg/dL, respectively). The pregnancy rate was greater (P = 0.01) in the sunflower-treated heifers (55.7%) than that in control-treated heifers (36.9%). Results indicate that sunflower seed supplementation increases the circulating cholesterol concentrations and potentially impacts the pregnancy rate in suckled beef cattle subjected to TAI or TET., (Copyright © 2015 Elsevier Inc. All rights reserved.)

The plasma levels of corticosteroids and sex steroids during pregnancy are key indicators of mammalian placental function and the onset of parturition. Steroid hormones are believed to be disturbed in pregnancies produced using assisted reproductive technologies (ARTs) due to placental dysfunction and the frequently observed lack of parturition signals. To elucidate the plasma steroid dynamics, a liquid chromatography-tandem mass spectrometry method was developed and used to determine the levels of corticosteroids (corticosterone, 11-deoxycortisol, and cortisol) and their direct precursors (progesterone and 17α-OH-progesterone) as well as sex steroids (androstenedione, estrone, estrone sulfate, testosterone, and 17β-estradiol) in bovine plasma. The levels of these 10 steroids in recipient cows carrying naturally conceived (control), in vitro fertilized (IVF), or cloned (somatic cell nuclear transfer) conceptuses were compared during late-term pregnancy (30 days before parturition), during near-term pregnancy (1 day before parturition), and on the day of parturition (day 0). Significant differences were observed among the corticosteroid levels: higher levels of corticosterone, 11-deoxycortisol, and cortisol were detected in cloned pregnancies at day 30; lower levels of corticosterone were observed in ART-derived pregnancies at days 1 and 0; and estrone and estradiol levels were higher in IVF pregnancies throughout the final development. These results suggested an upregulation of the P450C11 and P450C21 enzymes 30 days before parturition in somatic cell nuclear transfer pregnancies and an overactivation of the aromatase enzyme in IVF pregnancies. Taken together, the monitoring of multiple steroid hormones revealed that the pregnancies obtained using ART exhibited plasma steroid concentration dynamics compatible with the dysregulation of steroidogenic tissues.

In beef cattle, the ability to conceive has been associated positively with size of the preovulatory follicle (POF). Proestrus estradiol and subsequent progesterone concentrations can regulate the endometrium to affect receptivity and fertility. The aim of the present study was to verify the effect of the size of the POF on luteal and endometrial gene expression during subsequent early diestrus in beef cattle. Eighty-three multiparous, nonlactating, presynchronized Nelore cows received a progesterone-releasing device and estradiol benzoate on Day-10 (D-10). Animals received cloprostenol (large follicle-large CL group; LF-LCL; N = 42) or not (small follicle-small CL group; SF-SCL; N = 41) on D-10. Progesterone devices were withdrawn and cloprostenol administered 42 to 60 hours (LF-LCL) or 30 to 36 hours (SF-SCL) before GnRH treatment (D0). Tissues were collected at slaughter on D7. The LF-LCL group had larger (P < 0.0001) POF (13.24 ± 0.33 mm vs. 10.76 ± 0.29 mm), greater (P < 0.0007) estradiol concentrations on D0 (2.94 ± 0.28 pg/mL vs. 1.27 ± 0.20 pg/mL), and greater (P < 0.01) progesterone concentrations on D7 (3.71 ± 0.25 ng/mL vs. 2.62 ± 0.26 ng/mL) compared with the SF-SCL group. Luteal gene expression of vascular endothelial growth factor A, kinase insert domain receptor, fms-related tyrosine kinase 1, steroidogenic acute regulatory protein, cytochrome P450, family 11, subfamily A, polypeptide 1, and hydroxy-delta-5-steroid dehydrogenase, 3 beta- and steroid delta-isomerase 7 was similar between groups. Endometrial gene expression of oxytocin receptor and peptidase inhibitor 3, skin-derived was reduced, and estrogen receptor alpha 2, aldo-keto reductase family 1, member C4, and lipoprotein lipase expression was increased in LF-LCL versus SF-SCL. Results support the hypothesis that the size of the POF alters the periovulatory endocrine milieu (i.e., proestrus estradiol and diestrus progesterone concentrations) and acts on the uterus to alter endometrial gene expression. It is proposed that the uterine environment and receptivity might also be modulated. Additionally, it is suggested that increased progesterone secretion of cows ovulating larger follicles is likely due to increased CL size rather than increased luteal expression of steroidogenic genes., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Sixty female Wistar rats were submitted to a daily intake of ration doped with uranium from weaning to adulthood. Uranium in bone was quantified by the SSNTD (solid state nuclear track detection) technique, and bone mineral density (BMD) analysis performed. Uranium concentration as a function of age exhibited a sharp rise during the first week of the experiment and a drastic drop of 70% in the following weeks. Data interpretation indicates that uranium mimics calcium. Results from BMD suggest that radiation emitted by the incorporated Uranium could induce death of bone cells., (© 2013 Elsevier Ltd. All rights reserved.)

The effects of nursing regimens on the body condition, onset of ovarian cyclicity postpartum and weaning weight of lambs were assessed in Santa Ines ewes. Thirty-two ewes were blocked according to parity, number of lambs, and body weight at lambing and within each block randomly allocated to treatments: continuous nursing (CN), controlled nursing (CN2) with two daily feedings for an hour after the 10th day postpartum, or early weaning (EW) with total separation from the lambs after the 10th day. The animals were evaluated from the 12th day postpartum until the first estrus or until 60th day. The dry matter and nutrients intake did not differ among treatments (P>0.05) but did differ over time (P<0.01). The weight, body condition score, serum concentrations of non-esterified fatty acids and prolactin, the percentages of ewes in estrus, of ewes that ovulated within 60th day and had ovulation silent, the period from lambing to estrus, ovulation and follicle with a diameter ≥5mm and the maximum follicular diameter did not differ (P>0.05) among the treatments. The percentage of ovulation until 30th day was greater (P<0.05) in the EW group. The percentage of short luteal phases was higher in the CN2 and EW groups (P=0.07) and normal luteal phases were higher in the CN group (P=0.01). Lamb weight weaning was lower in the EW group (P<0.05). It is possible to use CN to obtain lambing periods less than eight months in Santa Ines ewes, with the advantages of simpler management and higher lamb weaning weights., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The effects of estradiol benzoate (EB) and estradiol cypionate (EC) on induction of ovulation after a synchronized LH surge and on fertility of Bos indicus females submitted to timed AI (TAI) were evaluated. In Experiment 1, ovariectomized Nelore heifers were used to evaluate the effect of EB (n = 5) and EC (n = 5) on the circulating LH profile. The LH surge timing (19.6 and 50.5 h; P = 0.001), magnitude (20.5 and 9.4 ng/mL; P = 0.005), duration (8.6 and 16.5 h; P = 0.001), and area under the LH curve (158.6 and 339.4 ng/mL; P = 0.01) differed between the EB and EC treatments, respectively. In Experiment 2 (follicular responses; n = 60) and 3 (pregnancy per AI; P/AI; n = 953) suckled Bos indicus beef cows submitted to an estradiol/progesterone-based synchronization protocol were assigned to receive one of two treatments to induce synchronized ovulation: 1 mg of EB im 24 h after progesterone (P4) device removal or 1 mg of EC im at P4 device removal. There was no difference (P > 0.05) between EB and EC treatments on follicular responses (maximum diameter of the ovulatory follicle, 13.1 vs. 13.9 mm; interval from progesterone device removal to ovulation, 70.2 vs. 68.5 h; and ovulation rate, 77.8 vs. 82.8%, respectively). In addition, P/AI was similar (P < 0.22) between the cows treated with EB (57.5%; 277/482) and EC (61.8%; 291/471). In conclusion, despite pharmacologic differences, both esters of estradiol administered either at P4 device removal (EC) or 24 h later (EB) were effective in inducing an LH surge which resulted in synchronized ovulations and similar P/AI in suckled Bos indicus beef cows submitted to TAI., (Copyright © 2012 Elsevier Inc. All rights reserved.)

The objective was to compare pharmacological strategies aiming to inhibit prostaglandin F2 alpha (PGF(2α)) synthesis (flunixin meglumine; FM), stimulate growth of the conceptus (recombinant bovine somatotropin; bST) and progesterone (P(4)) synthesis (human chorionic gonadotropin; hCG), as well as their combinations, regarding their ability to improve pregnancy rates in beef cattle. Lactating Nelore cows (N = 975), 35 to 70 days postpartum, were synchronized and inseminated by timed artificial insemination (TAI) on Day 0. On Day 7, cattle were allocated into eight groups and received one of the following treatments: saline (S) on Days 7 and 16 (Group Control); S on Day 7 and FM on Day 16 (Group FM); bST on Day 7 and S on Day 16 (Group bST); bST on Day 7 and FM on Day 16 (Group bST + FM); hCG on Day 7 and S on Day 16 (Group hCG); hCG on Day 7 and FM on Day 16 (Group hCG + FM); bST and hCG on Day 7 and S on Day 16 (Group bST + hCG), or bST and hCG on Day 7 and FM on Day 16 (Group bST + hCG + FM). The aforementioned treatments were administered at the following doses: 2.2 mg/kg FM (Banamine®; Intervet Schering-Plough, Cotia, SP, Brazil), 500 mg bST (Boostin®; Intervet Schering-Plough), and 2500 IU hCG (Chorulon®; Intervet Schering-Plough). Pregnancy diagnosis was performed 40 days after TAI by transrectal ultrasonography. Pregnancy rates were not significantly different among treatments. However, there was a main effect of hCG treatment to increase pregnancy rates (63.0 vs. 55.4%; P = 0.001). Concentrations of P(4) did not differ significantly among groups on Day 7 or on Day 16. However, consistent with the higher pregnancy rates, hCG increased P(4) concentrations on Day 16 (10.6 vs. 9.6 ng/mL, respectively; P = 0.05). We concluded that hCG treatment 7 days after TAI improved pregnancy rates of lactating Nelore cows, possibly via a mechanism leading to induction of higher P(4) concentrations, or by reducing the luteolytic stimulus during maternal recognition of pregnancy., (Copyright © 2011 Elsevier Inc. All rights reserved.)

Nine heifers were pre-synchronized (PGF2α, 12 days) and assigned into three groups with 6 repetitions each: (1) CL (∼8 days old, n=13); (2) DIB+CL (n=18); (3) DIB+EB (150 μg of PGF2α and 2mg estradiol benzoate, n=18). After progesterone (P4) device removal (8 days) and/or final PGF2α, heifers were injected with either GnRH or EB in a 3×2 factorial totalling 49 observations (5 were excluded). The blood sampling schedule: every 12 h during P4 period; for LH pulse frequency on Days 3-5, every 15 min for 6 h during P4 period; after P4 removal and EB treatment, samples were collected every 3 h for 24 h or after GnRH every 1 h for 10 h. Ovarian follicle number and diameter were evaluated by ultrasonography every 12 h until the last blood sample and then 24 h and 48 h later. After device insertion (12 h), the DIB+CL group had a lesser LH concentration than the DIB+EB group. After 36 h, all DIB+CL-treated heifers had less LH than CL-heifers, and after 60 h, the DIB+EB group had less LH than the CL-group. Considering all P4 groups combined, LH peak amplitude was greater after GnRH compared to EB treatment but total area of LH peak amplitude and time to first peak was less. The CL-group had fewer follicles and a greater largest follicle diameter than DIB+CL and DIB+EB groups. When treated with EB, the DIB+CL group had a lesser ovulation rate at 24 h than the CL- and DIB+EB-groups. Fixed time artificial insemination (FTAI) protocols promoted a pre-ovulatory LH peak, independent of previous exposure to the DIB coupled with a CL or not. The progesterone excess interfered with FSH and LH secretion, follicular development and ovulation within 24 h., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Changes in luteinizing hormone (LH) secretion after 17β-estradiol (E(2)) injection were evaluated during sexual maturation in 10 prepubertal Nelore heifers. Heifers were divided into 2 groups: intact (I) and ovariectomized (OVX). 17β-estradiol (2 μg/kg) was administered to both groups at 10, 13, and 17 mo of age. Only at 10 mo of age was there a greater mean LH concentration in OVX heifers (1.33 ± 0.29 ng/mL) compared with the I group (0.57 ± 0.15 ng/mL). At 13 and 17 mo of age there was no significant difference between the 2 groups in any of the evaluated variables (number of peaks, total peak area, greatest peak area, and time to greatest peak occurrence). This suggests a decrease in negative E(2) feedback associated with an increase in positive feedback to LH secretion during sexual maturation, and these were likely the key factors that determined the time of first ovulation in Nelore heifers.

The objectives of this study were to determine the interval from ovulation to deviation and the diameter of the dominant (DF) and largest subordinate (SF) follicles at deviation in buffalo (Bubalus bubalis) heifers. Two methods of evaluation (observed vs. calculated) were used. FSH and LH profiles encompassing follicle deviation (Experiment 1), and the follicular diameter when the DF acquired ovulatory capacity (Experiment 2) were also determined. The time of deviation and the diameter of the DF and the largest SF at deviation did not differ between observed and calculated methods. Overall, follicle deviation occurred 2.6 ± 0.2d (mean ± SEM) after ovulation, and the diameters of the DF and SF at deviation were 7.2 ± 0.2 and 6.4 ± 0.2mm, respectively. No changes in plasma levels of FSH or LH were observed (P=0.32 and P=0.96, respectively). Experiment 2 was conducted in two phases according to the diameter of the DF during the first wave of follicular development at the time of LH challenge (25mg of pLH). In the first phase, follicles ranging from 5.0 to 6.0mm (n=7), 6.1 to 7.0mm (n=11), or 7.1 to 8.0mm (n=9) were used, and in the second phase, follicles ranging from 7.0 to 8.4mm (n=10), 8.5 to 10.0mm (n=10), or 10.1 to 12.0mm (n=9) of diameter were used. After the pLH treatment, the DF was monitored by ultrasonography every 12h for 48h. No ovulations occurred in heifers in the first phase. However, in the second phase, an effect of follicular diameter was observed on ovulation rate [7.0-8.4mm (0.0%, 0/10), 8.5-10.0mm (50.0%, 5/10), and 10.0-12.0mm (55.6%, 5/9)]. In summary, follicle deviation occurred 2.6d after ovulation in buffalo (B. bubalis) heifers, when the diameters of the DF and SF were 7.2 and 6.4mm, respectively. No significant changes in plasma concentrations of FSH or LH were detected. Finally, the acquisition of ovulatory capacity occurred when the DF reached 8.5mm in diameter., (Copyright © 2010 Elsevier B.V. All rights reserved.)

Two experiments were designed to evaluate strategies to increase fertility of Bos indicus postpubertal heifers and nonlactating cows submitted to a fixed-time artificial insemination (TAI) protocol consisting of an intravaginal device containing 1.9 g of progesterone (CIDR) insertion+estradiol benzoate on Day 0, CIDR withdrawal+estradiol cypionate on Day 9, and TAI on Day 11. In Experiment 1, heifers (n=1153) received a new or an 18-d previously used CIDR and, on Day 9, prostaglandin F(2 alpha) (PGF(2 alpha))+0, 200, or 300 IU equine chorionic gonadotropin (eCG). Heifers treated with a new CIDR had greater (least squares means+/-SEM) serum concentration of progesterone on Day 9 (3.06+/-0.09 ng/mL vs. 2.53+/-0.09 ng/mL; P<0.05) and a smaller follicle at TAI (11.61+/-0.11 mm vs. 12.05+/-0.12 mm; P<0.05). Heifers with smaller follicles at TAI had lesser serum progesterone concentrations on Day 18 and reduced rates of ovulation, conception, and pregnancy (P<0.05). Treatment with eCG improved (P<0.05) follicle diameter at TAI (11.50+/-0.10mm, 11.90+/-0.11 mm, and 12.00+/-0.10mm for 0, 100, and 200 IU, respectively), serum progesterone concentration on Day 18 (2.77+/-0.11 ng/mL, 3.81+/-0.11 ng/mL, and 4.87+/-0.11 ng/mL), and rates of ovulation (83.8%, 88.5%, and 94.3%) and pregnancy (41.3%, 47.0%, and 46.7%). In Experiment 2, nonlactating Nelore cows (n=702) received PGF(2 alpha) treatment on Days 7 or 9 and, on Day 9, 0 or 300 IU eCG. Cows receiving PGF(2 alpha) on Day 7 had lesser serum progesterone concentrations on Day 9 (3.05+/-0.21 ng/mL vs. 4.58+/-0.21 ng/mL; P<0.05), a larger follicle at TAI (11.54+/-0.21 mm vs. 10.84+/-0.21 mm; P<0.05), and improved (P<0.05) rates of ovulation (85.4% vs. 77.0%), conception (60.9% vs. 47.2%), and pregnancy (52.0% vs. 36.4%). Treatment with eCG improved (P<0.05) serum progesterone concentration on Day 18 (3.24+/-0.14 ng/mL vs. 4.55+/-0.14 ng/mL) and the rates of ovulation (72.4% vs. 90.0%) and pregnancy (37.5% vs. 50.8%). In conclusion, giving PGF(2 alpha) earlier in the protocol in nonlactating cows and eCG treatment in postpubertal heifers and nonlactating cows improved fertility in response to a TAI (progesterone+estradiol) protocol.

The main objective of this study was to evaluate a recumbent left flank approach to bilateral ovariectomy in prepubertal heifers and to develop an optimal surgical technique for this procedure. Both ovaries were removed from 6 Nelore heifers by left flank approach without any complications, except in 1 heifer, which was believed to have had only 1 ovary based on ultrasound and exploration during surgery, but was later found to have a remaining functional ovary. Ovariectomy via left flank approach in recumbent prepubertal heifers is feasible and technically easy. This procedure does not involve special instrumentation and, despite the invasive approach, it allows optimal visualization of the ovaries and uterus.

Escherichia coli samples isolated from female patients with cystitis were characterized with regard to the presence of virulence factors associated with biofilm formation and phylogenetic groupings. Polymerase chain reaction results demonstrated that all the samples were positive for the gene fimH (type 1 fimbriae), 91 for fliC (flagellins), 50 for papC (P fimbriae), 44 for kpsMTII (capsules) and 36 for flu (antigen 43). The results from assays to quantify the biofilm formation demonstrated that 44 samples produced biofilm on polystyrene microplates and 56 samples produced weak or no biofilm. We also confirmed that Escherichia coli samples were present in phylogenetic groups B2 and D.

The objective of the present study was to characterize ovarian follicular dynamics and hormone concentrations during follicular deviation in the first wave after ovulation in Nelore (Bos indicus) heifers. Ultrasonographic exams were performed and blood samples were collected every 12h from the day of estrus until 120-144 h after ovulation in seven females. Deviation was defined as the point at which the growth rate of the dominant follicle became greater than the growth rate of the largest subordinate follicle. Deviation occurred approximately 65 h after ovulation. Growth rate of the dominant follicle increased (P<0.05) after deviation, while growth rate of the subordinate follicle decreased (P<0.05). Diameter of the dominant follicle did not differ from the subordinate follicle at deviation (approximately 5.4mm). The dominant follicle (7.6mm) was larger (P<0.05) than the subordinate follicle (5.3mm) 96 h after ovulation or 24h after deviation. Plasma FSH concentrations did not change significantly during the post-ovulatory period. The first significant increase in mean plasma progesterone concentration occurred on the day of follicular deviation. In conclusion, the interval from ovulation to follicular deviation (2.7 days) was similar to that previously reported in B. taurus females, but follicles were smaller. Diameters of the dominant follicle and subordinate follicle did not differ before deviation and deviation was characterized by an increase in dominant follicle and decrease in subordinate follicle growth rate. Variations in FSH concentrations within 12-h intervals were not involved in follicular deviation in Nelore heifers.

The accumulation and microdistribution of uranium in the bone and marrow of Beagle dogs were determined by both neutron activation and neutron-fission analysis. The experiment started immediately after the weaning period, lasting till maturity. Two animal groups were fed daily with uranyl nitrate at concentrations of 20 and 100 microg g(-1) food. Of the two measuring techniques, uranium accumulated along the marrow as much as in the bone, contrary to the results obtained with single, acute doses. The role played by this finding for the evaluation of radiobiological long-term risks is discussed. It was demonstrated, by means of a biokinetical approach, that the long-term accumulation of uranium in bone and marrow could be described by a piling up of single dose daily incorporation.

Puberty in Zebu heifers follows a pattern characterized by a decrease in the steroid feedback mechanism and an increase in LH concentration, which result in the first ovulation followed by a short estrous cycle and the onset of normal cycles thereafter. These events are similar to those observed in Bos taurus cattle but occur at a later age. The late onset of puberty is both genetic and environmental in origin and is reflected by the age at first calving that can be at 40 months of age or older in these animals. Age at puberty in Zebu heifers has been shown to have a high heritability. Consequently, selecting precocious heifers may be an effective means of reducing age at puberty in these animals and this approach is being adopted in commercial practice. Genetic selection is not the sole solution to the problem because environmental improvements are necessary, particularly in terms of improved nutrition. South American Zebu cattle are usually subject to sub-optimum nutritional and management conditions and, hence, exhibit late onset of puberty. Hybrids of Zebu and Bos taurus cattle exhibit heterosis in respect of the age of puberty with earlier onset than expected in crossbred animals. Recently, purebred South American Zebu cattle have been shown to have Bos taurus genes, indicating that there have been previous attempts to improve their productivity using this approach. It was concluded that the age at first calving in South American Zebu cattle can be reduced by exposing well-fed, yearling heifers to bulls and selecting, over several generations, those animals that become pregnant at an early age.

Twelve female ponies were examined daily for 30 days and classified as ovulating (OV; N = 6; 197 +/- 6 kg) or prepubertal (PP; N = 6; 196 +/- 9 kg). Follicles were detected by ultrasound and gonadotropins quantified by radioimmunoassay. The mean diameter of the largest follicles was significantly larger in OV (38 +/- 1 mm) than in PP (26 +/- 2 mm) but there was no difference between groups in the size of the second largest follicle. There were more small follicles (<24 mm) in the PP than in the OV group, but PP fillies had a smaller number of follicles >29 mm than the OV fillies. Follicle-stimulating hormone (FSH) levels did not differ between groups but PP fillies had lower luteinizing hormone (LH) peak (8 +/- 1 ng/ml) and basal (4 +/- 0.5 ng/ml) levels, lower peak magnitude (2 +/- 0.2 ng/ml) and period average (5 +/- 0.6 ng/ml) than OV fillies (32 +/- 4.5, 8 +/- 1.2, 17.1 +/- 6, and 15 +/- 2.3 ng/ml, respectively). The PP group, in contrast to the OV group, showed no relationship between FSH surge and follicle wave emergence. We conclude that an LH concentration higher than 8 ng/ml is needed for follicle growth to a preovulatory size. Wave emergence and FSH secretion seem to be independent events, probably due to an inhibitory neural system in these PP animals. PP fillies may provide a physiological model for the study of follicle wave emergence which apparently does not depend on gonadotropin levels.

Groups of Wistar rats were fed with ration doped with uranyl nitrate at concentration A ranging from 0.5 to 100 ppm, starting after the weaning period and lasting until the postpuberty period when the animals were sacrificed. Uranium in the ashes of bones was determined by neutron activation analysis. It was found that the uranium concentration in the bones, as a function of A, exhibits a change in its slope at approximately 20 ppm-a probable consequence of the malfunctioning of kidneys. The uranium transfer coefficient was obtained and an analytical expression was fitted into the data, thus allowing extrapolation down to low doses. Internal and localized doses were calculated. Absorbed doses exceeded the critical dose, even for the lowest uranium dosage.

Groups of animals (Wistar rats) were fed with rations doped with uranyl nitrate at concentrations ranging from 0.5 to 100 ppm. The uranium content in the ashes of the organs was measured by the neutron-fission track counting technique. The most striking result is that the transfer coefficients, as a function of the uranium concentration, exhibit a concave shape with a minimum around 20 ppm-U for all organs. Explanations to interpret this finding are tentatively given.

Follicle populations and concentrations of circulating gonadotropins were studied during age 2-10 months in 10 spring-born pony fillies. Blood sampling and ultrasound scanning were done every 4 days and daily for four 30 day periods. During 5-12 weeks, FSH concentrations were lower in 6 fillies with follicles > or = 6 mm (mean +/- s.e. 1.4 +/- 0.1 ng/ml) than in 4 fillies with follicles < 6 mm (2.8 +/- 0.3 ng/ml). The diameters and numbers of follicles and gonadotropin concentrations increased progressively during age 2-4 months. A plateau in follicle activity and reduced levels of gonadotropins occurred during 5-7 months. During 8-10 months, follicles grew to > 10 mm and gonadotropin concentrations increased. Waves of follicular growth were identified during the 30 day periods by significant increases in the diameter of the 10 largest follicles. The waves did not partition into dominant and subordinate follicles. Results indicated an initial postnatal period of negative ovarian feedback, temporally related changes in gonadotropins and follicles for months 3-10, and development of follicles in waves.

The effect of altered LH concentrations on the deviation in growth rates between the 2 largest follicles was studied in pony mares. The progestational phase was shortened by administration of PGF2alpha on Day 10 (Day 0=ovulation; n=9) or lengthened by daily administration of 100 mg of progesterone on Days 10 to 30 (n=11; controls, n=10). All follicles > or = 5 mm were ablated on Day 10 in all groups to initiate a new follicular wave. The interovulatory interval was not altered by the PGF2alpha treatment despite a 4-day earlier decrease in progesterone concentrations. Time required for growth of the follicles of the new wave apparently delayed the interval to ovulation after luteolysis. The FSH concentrations of the first post-ablation FSH surge were not different among groups. A second FSH surge with an associated follicular wave began by Day 22 in 7 of 11 mares in the progesterone group and in 0 of 19 mares in the other groups, indicating reduced functional competence of the largest follicle. A prolonged elevation in LH concentrations began on the mean day of wave emergence (Day 11) in the prostaglandin group (19.2 +/- 2.2 vs 9.0 +/- 0.7 ng/mL in controls; P<0.05), an average of 4 d before an increase in the controls. Concentrations of LH in the progesterone group initially increased until Day 14 and then decreased so that by Day 18 the concentrations were lower (P<0.05) than in the control group (12.9 +/- 1.6 vs 20.2 +/- 2.6 ng/mL). Neither the early and prolonged increase nor the early decrease in LH concentrations altered the growth profile of the second-largest follicle, suggesting that LH was not involved in the initiation of deviation. However, the early decrease in LH concentrations in the progesterone group was followed by a smaller (P<0.05) diameter of the largest follicle by Day 20 (26.9 +/- 1.7 mm) than the controls (30.3 +/- 1.7 mm), suggesting that LH was necessary for continued growth of the largest follicle after deviation.

The effects of several doses of progesterone on FSH and LH concentrations were used to study the role of the gonadotropins on deviation in growth rates of the two largest follicles during the establishment of follicle dominance. Progesterone was given to pony mares at a daily dose rate of 0 mg (controls), 30 mg (low dose), 100 mg (intermediate dose), and 300 mg (high dose). All follicles > or = 6 mm were ablated at Day 10 (Day 0 = ovulation) to initiate a new follicular wave; prostaglandin F(2alpha) was given to induce luteolysis, and progesterone was given from Days 10 to 24. The low dose did not significantly alter any of the ovarian or gonadotropin end points. The high dose reduced (P < 0.05) the ablation-induced FSH concentrations on Day 11. Maximum diameter of the largest follicle (17.2 +/- 0.6 mm) and the second-largest follicle (15.5 +/- 0.9 mm) in the high-dose group was less (P < 0.04) than the diameter of the second-largest follicle in the controls (20.0 +/- 1.0 mm) at the beginning of deviation (Day 16.7 +/- 0.4). Thus, the growth of the two largest follicles was reduced by the high dose, presumably through depression of FSH, so that the follicles did not attain a diameter characteristic of deviation in the controls. The intermediate dose did not affect FSH concentrations. However, the LH concentrations increased in the control, low, and intermediate groups, but then decreased (P < 0.05) in the intermediate group to pretreatment levels. The LH decrease in the intermediate group occurred 2 days before deviation in the controls. The maximum diameter of the largest follicle was less (P < 0.0001) in the intermediate group (27.3 +/- 1.8 mm) than in the controls (38.9 +/- 1.5 mm), but the maximum diameter of the second-largest follicle was not different between the two groups (19.0 +/- 1.1 vs. 20.3 +/- 1.0 mm). Thus, the onset of deviation, as assessed by the second-largest follicle, was not delayed by the decrease in LH. Diameter of the largest follicle by Day 18 in the intermediate group (23.1 +/- 1.6 mm) was less (P < 0.05) than in the controls (28.0 +/- 1.0 mm). These results suggest that circulating LH was not involved in the initiation of dominance (inhibition of other follicles by the largest follicle) but was required for the continued growth of the largest follicle after or concurrently with its initial expression of dominance.

Eight Panthera onca (Po), 13 Felis concolor (Fc), 7 Felis yagouaroundi (Fy), 7 Felis tigrina (Ft) and 5 Felis pardalis (Fp) specimens from São Paulo State zoos were used. All animals were restrained with darts containing 10 mg/kg ketamine and 1 mg/kg xylazine. Venous blood samples were collected as soon as possible (within 15-20 min) and serum was frozen until the time for cortisol quantification. Cortisol was determined using a solid phase radioimmunoassay with an intra-assay coefficient of 8.51%. Data were analyzed statistically by the Kruskal-Wallis test, followed by Dunn's multiple comparisons test, and the one-sample t-test, with the level of significance set at P < 0.05. Data are reported as means +/- SEM. Cortisol levels differed among the captive felines: Po = 166 +/- 33a, Fc = 670 +/- 118b, Fy = 480 +/- 83b, Ft = 237 +/- 42ab, Fp = 97 +/- 12a nmol/l (values followed by different superscript letters were significantly different (P < 0.001)). Since most of the veterinary procedures on these species involve chemical restraint, these results show the necessity of preventive measures in order to minimize the effect of restraint stress on more susceptible species.

Thoroughbred fillies were divided into three groups according to age: group 1, 7 fillies aged 1 to 2 years (G1) starting the training program; group 2, 9 fillies aged 2 to 3 years (G2) in a full training program; group 3, 8 older fillies 3 to 4 years of age (G3) training and racing. Blood samples were collected weekly from July to December. Cortisol was quantified using a solid phase DPC kit. The intra- and interassay coefficients of variation were 12.5% and 15.65% and sensitivity was 1.9 +/- 0.2 nmol/l. The semester average of cortisol levels varied between groups: G1 = 148.8 +/- 6.7, G2 = 125.7 +/- 5.8, G3 = 101.1 +/- 5.4 nmol/l, with G3 differing statistically from the other groups. The lower cortisol levels observed in the older fillies leads us to propose that the stress stimulus, when maintained over a long period of time, may become chronic and result in a reduction of hypophyseal corticotropin-releasing hormone receptors. The secretion of endogenous opioids may also lead to low serum cortisol levels.

We measured progesterone and estradiol levels from birth to the beginning of adult life in 10 Thoroughbred fillies from the Equilia Stud Farm in Avaré SP, Brasil. The animals were measured and weighed monthly for the determination of body development and of a possible correlation between the rate of weight and height gain and the onset of detectable sex hormone levels. Jugular blood was collected twice a week and stored at -20 degrees C until assay of progesterone by a solid phase RIA with a sensitivity of 0.32 nmol L and of estradiol by liquid phase RIA adapted to low levels (3.67 pmol L ). The fillies were born with high serum levels of both hormones, which fell to undetectable levels by the first week of life. A variation in growth rate was observed, with the highest levels occurring from birth to the 3rd month of life, followed by a reduction until 15 mo of life, when fast growth was resumed. The monthly weight gain was 1.5% when the fillies reached puberty and 5.4% during the next month, (P < 0.05, Friedman test). During this second period of accelerated growth after the beginning of progesterone production at detectable levels (above 0.318 nmol L ), the parameters of skeletal growth did not differ (P > 0.05). The month of onset of puberty was the month of lowest weight gain in the life of the fillies, and it coincided with the highest insolation period. In conclusion, horses, like all other developed vertebrates, have a double pattern of development, with the acceleration observed at puberty depending on sex steroids, which in turn coincides with the highest insolation period. Gonadal activity characterized by serum progesterone levels was low from birth to the onset of puberty. After puberty the progesterone cycles were similar to those of adult animals with a mature hypothalamic-gonadal axis.