Comparison between indicine and taurine cattle DNA methylation reveals epigenetic variation associated to differences in morphological adaptive traits

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.

Effect of growth rates on hormonal and pubertal status in Nellore heifers early weaned

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.

Implications of growth rates and compensatory growth on puberty attainment in Nellore heifers

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.

49 The dynamic changes in uterine morphology and function during the proestrus-diestrus transition in beef cattle

In cattle, early development of the non-attaching embryo depends exclusively on the biochemical properties of the intrauterine milieu. As the embryo transitions from the oviduct to the tip of the uterine horn around 4 days after oestrus, little is known about uterine functions that modulate the milieu composition and potentially determine pregnancy success. The objective was to characterise changes in uterine luminal fluid (ULF) accumulation and absorption, endometrial vascularity, and endometrial thickness in response to progesterone fluctuations during the peri-ovulatory period in beef heifers. Fourteen Bos indicus heifers that presented a prostaglandin F2α (PGF2α) responsive CL received 500µg of PGF2α analogue i.m. (PGF) and were examined daily by rectal B-mode and pulse-wave colour-Doppler ultrasonography until the fifth day after oestrus (oestrus=Day 0). Plasma progesterone (P4) concentrations were measured daily. Uterine luminal fluid score was given based on the accumulation of fluid throughout the entire organ (0, no fluid, to 4). Measurement of the main ovarian structures, endometrial thickness, uterine luminal fluid score, and luminal fluid area of the cranial portion of the uterine horn ipsilateral to the preovulatory follicle and subsequent CL were executed by B-mode ultrasonography and endometrial vascularity by colour Doppler. The fixed effect of day was analysed by ANOVA. There was an effect of day on endometrial vascularity, endometrial thickness, and uterine luminal fluid score (P≤0.01) as well as uterine luminal fluid area (P≤0.05). Endometrial vascularity and endometrial thickness increased after PGF injection to peak on Day −1, whereas uterine fluid score peaked on Day 0. Interestingly, cranial uterine luminal fluid area peaked twice, on Day −1 and Day 5. Vascularity, thickness, and fluid accumulation decreased gradually from Day 0 to Day 5. There was a negative correlation (r=−0.55) between the sum of daily P4 concentrations during proestrus (i.e. from PGF to oestrus) and the greatest ULF score measured (P=0.05). Length of proestrus was correlated negatively (r=−0.69) with the increase in uterine body thickness during proestrus (P=0.03). The sum of daily luminal fluid scores, from PGF injection to Day 5, was double for heifers grouped within the upper third for that variable compared with those grouped within the lower third. In conclusion, peri-ovulatory transformations in uterine morphology and function are dramatic and vary in duration and in intensity among animals. Temporal changes in intraluminal fluid accumulation and absorption at the site of embryo arrival may change its biochemical composition. Potential implications for embryo receptivity and reproductive outcomes deserve further investigation.

128 Evidence that Pregnancy-Associated Serum Protein A (PAPP-A) Plays Role on Bovine In Vitro Embryo Production

The aim of present work was to assess the effects of pregnancy-associated serum protein A (PAPP-A) during oocyte in vitro maturation (IVM) on meiosis progression, DNA fragmentation, IGF-1 free bioavailability, as well as effects on embryo yield and transcriptional profile of matured cumulus–oocyte complexes (COC). First, the COC from a local abattoir were submitted to IVM for 24 h with TCM-199 serum-free medium supplemented with PAPP-A (100 ng mL−1: P100 group) or not (control group). The matured oocytes were submitted to evaluation of DNA fragmentation (TUNEL assay) and meiosis progression (Hoechst 33342; n = 5 replicates; 20 COC/replicate per group), and maturation medium was collected to measure levels of free IGF-1. Then, the oocytes were separated from their respective cumulus cells and followed for the transcriptional profile of 96 genes (3 reference genes; ACTH, GAPDH, PPIA) by RT-qPCR using Taqman® assays in the HD-Biomark System® (Fluidigm Corp., South San Francisco, CA, USA). Further, the matured oocytes were submitted to in vitro fertilization followed by in vitro culture for 7 days. On Days 3 and 7, the cleavage and blastocyst (BL) rates were verified. On Day 7, BL (3 BL/pool; control: n = 4 pools; P100: n = 5 pools) were collected to analyse the transcriptional pattern of 96 genes (4 reference genes; ACTH, GAPDH, PPIA, and SDHA) as described above for COC. The DNA fragmentation, meiosis progression, cleavage, and BL rates were calculated as percentages and transformed to arcsine. The mRNA abundance of target genes was normalized by geometric mean of reference genes and data were transformed to fold change. The free IGF-I concentration also was transformed to fold change. All data were tested by ANOVA and means were compared with t-test or Wilcoxon tests using JMP software (SAS Institute Inc., Cary, NC, USA). Differences were considered significant when P ≤ 0.05. The addition of PAPP-A increased free IGF-I concentration 1.27-fold in IVM medium. There were no alterations in the percentage of oocytes in metaphase II or oocyte DNA fragmentation. In cumulus cells, the genes BCL2, GPX1, RPLP0, and RPS25 (anti-apoptotic and anti-oxidative stress) was higher in the P100 group, whereas DICER, GREM1, GUCY1B3, and FOXO3 (cell proliferation, cumulus expansion, cGMP regulator, and apoptotic initiator, respectively) were higher in the control group. In oocytes, the mRNA relative abundance of ACACA, BCL2, H1FOO, TXNRD1, and VCAN (related with fatty acid synthesis, anti-apoptotic effect, chromatin regulation, oxidative stress processes, and cell proliferation, respectively) was higher in the P100 group. There was no difference in cleavage rate or embryo yield. The mRNA abundance of genes related to cellular stress (ATF4, GPX4, and HIF1A) and lipid metabolism (FASN and SREBF1) was lower in embryos of the P100 group. On the other hand, genes involved in cellular proliferation/differentiation (MAPK1) and pluripotency (POU5F1) were up-regulated in embryos of the P100 group. In conclusion, the addition of PAPP-A during the IVM increased free IGF-I and modulates the gene expression in COC and blastocysts, which could modify oocyte competence and embryo development.

Impact of estradiol cypionate prior to TAI and progesterone supplementation at initial diestrus on ovarian and fertility responses in beef cows

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.

211 PRODUCTION OF PROGESTERONE FROM CANINE CUMULUS CELLS MATURED IN VITRO WITH STEROIDS AND GONADOTROPIN

The canine reproductive physiology is distinct from other mammals, especially concerning the role of progesterone in ovulation, oocyte maturation, and fertilisation. In vitro maturation of canine oocytes is challenging mostly due to the culture conditions required for this species and the lack of knowledge about the factors involved in meiotic resumption and complete maturation. To obtain more information about this physiological phenomenon, the present study was designed to investigate the ability of canine cumulus cells to secrete progesterone in the maturation medium during in vitro culture for up to 96 h. Ovaries were collected from 18 bitches at different reproductive status (follicular, luteal, and anestrous stages; various breeds, age 1–7 years) by routine ovariohysterectomy and sliced in PBS-polyvinyl alcohol (PVA) to release the cumulus‐oocyte complexes (COC). A total of 896 COC grade I (2 or more dense layers of cumulus cells and darkly pigmented cytoplasm) were selected for culture. Oocytes were randomly allocated in 2 media consisting of TCM-199 (Sigma Chemical Co., St. Louis, MO, USA) with antibiotics, 10% FBS, 2.2 mg mL–1 sodium bicarbonate, and 20 μL mL–1 pyruvic acid (control) and control + hormones (25 IU mL–1 hCG (Sigma), 1 mg mL–1 progesterone (Sigma), 1 mg mL–1 estradiol (E2; Sigma). The COC were incubated at 38°C, 5% CO2 in air and cultured for 24, 48, 72, and 96 h. Maturation medium for in vitro culture of COC was collected at 0, 24, 48, 72, and 96 h and checked for progesterone content by radioimmunoassay (RIA). Maturation rates (meiotic configuration) were also evaluated at each culture period by using Hoechst 33342 (Sigma). Polynomial regression analysis was applied to assess variation of progesterone concentration in the maturation medium during the 96 h of IVM. Progesterone was detected in the control and hormonal media; however, in the control medium the concentration was <0.5 ng mL–1. In the hormonal medium, there was a decrease in progesterone concentration at 24 h in all groups (ranged from 461.8 to 587.2 ng mL–1) followed by a progressive increase until 72 h in follicular group (1371.4 ng mL–1) and until 96 h in luteal and anestrous groups (934.4 and 669.4 ng mL–1, respectively). Maturation rates (metaphase II oocytes) were higher at 72 h and decreased at 96 h in all groups. The results of this study suggest that hormonal supplementation is necessary for canine oocyte to resume meiosis and to cumulus cells be capable of producing progesterone. Moreover, progesterone secretion by cumulus cells seems to be related to the reproductive status of the donor bitch once higher concentration of progesterone was detected in medium from follicular group and lower in anestrous group.

88 CHANGING MATERNAL NUTRITION IN EARLY PREGNANCY MODIFIES FETAL OVARY DEVELOPMENT IN NELLORE COWS

Environmental influences such as nutritional restriction during early gestation in cattle may impair fetal development and compromise functions in adulthood. During the first trimester of gestation fetal gonads are formed. We hypothesised that either restriction or excess of nutrients ingested by cows during the first third of pregnancy interferes with fetal body weight (BW) and ovary development. Twenty-one uniparous Nelore cows (BW = 488 ± 24 kg, body condition score, BCS = 3.1 ± 0.1) were subjected to timed AI with sexed semen (female) of a single bull and individually allocated to different diets. The diet of the control group (C) met the maintenance requirements, and the groups of high (A) and low (B) were either 180% or 60% of maintenance respectively. Live weight and BCS were assessed weekly to adjust the diet according to the individual weight of each animal. At 60 days of gestation, 9 fetuses (3/group) were removed by colpotomy (accessed through vagina), weighed, and their ovaries were dissected and weighed. One fetal ovary (of each pair) was analysed by RNA-seq (mRNA). The effects of treatments on both ovarian and fetal weight were compared by ANOVA (proc GLM, SAS 9.3, SAS Institute Inc., Cary, NC, USA). During the 60 days of treatment, cows from Group A gained 66 kg (from 474 ± 6 kg to 541 ± 10 kg) and 1.25 points in BCS (from 3.0 to 4.25), whereas the cows in group B lost 61 kg (from 458 ± 3 kg to 397 ± 6 kg) and 1 point in BCS (from 3.2 to 2.2). Fetal ovary weight (sum of the two) was lower in group B (0.007 ± 0.001 g; P < 0.04) than in groups A (0.02 ± 0.004 g) and C (0.013 ± 0.007 g), which did not differ (P > 0.08) between each other. Fetuses in group B weighed less (12.8 ± 1.14 g; P < 0.006) than in groups A (20.56 ± 2.2 g) and C (20.03 ± 0.8 g). Maternal nutritional status during the first 60 days of gestation changed the transcriptome of fetal ovaries. There were differences in the pattern of gene expression between the control, high, and low intake groups. A total of 79 genes out of 20 657 showed differential expression between treatments (false discovery rate 0.05), some of which were related to embryonic and ovarian development. Thus, we conclude that changing maternal nutrition during the first 60 days of gestation will change the transcriptomic profile of fetal ovaries. Poor maternal nutrition jeopardizes ovarian size and weight and fetal weight, suggesting impairment on the production of ovarian follicles. This is a critical period in fetal ovarian development, as oocytes grow and differentiate, and need to escape from degenerative processes to remain in the ovaries. Thus, the developmental impairment at the beginning of meiosis could reduce the number of oocytes in the fetal ovary. Histological examination of fetal ovaries is underway to evaluate the number of oocytes.Funding provided by FAPESP 2011/50839-1; CNPq 487036/2013-3, CAPES.

Corpus luteum development and function after supplementation of long-acting progesterone during the early luteal phase in beef cattle

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.

Nursing regimens: effects on body condition, return to postpartum ovarian cyclicity in Santa Ines ewes, and performance of lambs

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.

Effects of two estradiol esters (benzoate and cypionate) on the induction of synchronized ovulations in Bos indicus cows submitted to a timed artificial insemination protocol

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.

Effects of flunixin meglumine, recombinant bovine somatotropin and/or human chorionic gonadotropin on pregnancy rates in Nelore cows

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.

18 EFFECT OF GnRH TREATMENT IN LH SECRETION IN INTACT AND OVARIECTOMIZED NELLORE HEIFERS

The gonadotropin-releasing hormone (GnRH) and its analogues become control reproductive function in farm animals. The GnRH agonist (GnRHa), which is used in veterinary practice, has a longer half-life and higher affinity to GnRH receptors than the native decapeptide. GnRH or GnRHa effects depend on the species, dose, route, and the moment of administration. As Nellore is the main bovine breed in Brazil, corresponding to 70% of Brazilian herds, more studies on its reproductive physiology are needed. The objective was to study luteinizing hormone (LH) secretion in intact (I, n = 4) and ovariectomized (Ov, n = 4) prepubertal Nellore heifers (18 months) after gonadorelin acetate administration (25 μg, iv; Lecirelina, Gestran Plus, ARSA S.R.L., Buenos Aires, Argentina) from samples collected every 15 min for 10 h. LH was quantified by RIA, with sensitivity of 0.03 ng mL-1 and CV of 11%. Maximum LH amplitude was considered as the peak for each period. Peaks were identified as an increase 2 times higher than intraassay CV and involving at least 3 samples. The time for the highest peak occurrence was determined by GraphPad Prism program (Prism 3.00 for Windows, GraphPad Software, San Diego CA, USA). Results were compared by the ANOVA followed by t-test either paired or not using GraphPad InStat (3.06 version). After GnRH treatment, maximum LH peak amplitude was higher in Ov (12.48 ± 1.41 ng mL-1) (P ≤ 0.05) than in intact heifers (6.42 ± 1.30 ng mL-1), but there was no significant difference (P ≥ 0.05) on LH pulse frequency, with only one peak in both groups during the 10-h period. Although there was a small delay in peak occurrence in I (63.75 ± 21.48 min) compared with Ov heifers (45 ± 16.43 min), there was no difference (P ≥ 0.05) between groups. The results suggested a higher hypothalamus sensitivity to GnRH in absence of gonadal steroids or a higher LH storage during the hypergonatropism period. Support by FAPESP (São Paulo, Brazil); fellowship from CAPES.

209 SEASONAL CHANGES IN CHARACTERISTICS OF THE ESTROUS CYCLE IN BOS TAURUS INDICUS (NELORE) HEIFERS

To evaluate the possible seasonal variation in estrous cycle characteristics, 8 heifers were synchronized with 2 prostaglandin injections and their estrous cycles were followed during different seasons of the year (autumn, n = 413; winter, n = 8; spring, n = 9; and summer, n = 9) with daily ultrasonographic exams to count and measure follicles ≥3 mm. Blood was collected every 12 h for luteinizing hormone (LH) and progesterone (P4), and every 3 h from estrus until ovulation to characterize the LH peak. Five ovariectomized heifers were injected with 17β-estradiol (2 μg/kg of liveweight) every season and blood samples were collected thereafter at 3 h intervals for LH quantification. The monthly body weight percentile difference (Δ%) did not vary among seasons. Average P4 concentration for the cycle was higher (P = 0.001) and follicle numbers lower during autumn (2.5 ± 0.2 ng mL-1; 7.8 ± 0.1) and summer (2.9 ± 0.3 ng mL-1; 6.8 ± 0.2; P = 0.001) compared with winter (1.4 ± 0.2 ng mL-1; 9.6 ± 0.3) and spring (1.6 ± 0.2 ng mL-1; 9.7 ± 0.3). During winter, there were more estrous cycles with 3 follicle waves (5/8) and during summer only there were cycles with 2 follicular waves (P = 0.009). Because LH secretion did not vary despite seasonal variation in P4 concentration and because there was a negative correlation between higher P4 values and daily percentile variation of photoperiod (A%; P = 0.0038; r = -0.4533), seasonal variation in the luteal cell sensitivity to LH needs to be evaluated. In the ovariectomized Nelore heifers, the LH circannual concentration without estradiol stimulus was significant (P = 0.02). The LH response to estradiol treatment was lower in summer (0.8 ± 0.2 ng mL-1 v. 1.3 ± 0.5 ng mL-1). We hypothesize that seasonal variation exists in hypothalamic sensitivity to estradiol. The present experiment provides evidence that seasonality in reproductive responses remains in Nelore heifers. FAPESP (07-53539-3), UNESP, and Devani Mariano Pinheiro.

Long‐term accumulation and microdistribution of uranium in the bone and marrow of beagle dog

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.

Long-term accumulation of uranium in bones of Wistar rats as a function of intake dosages

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.

Puberty in South American Bos indicus (Zebu) cattle

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.

Follicle profile and plasma gonadotropin concentration in pubertal female ponies

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.

Transfer coefficient measurements of uranium to the organs of Wistar rats, as a function of the uranium content in the food

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.

Dynamics of follicle populations and gonadotropin concentrations in fillies age two to ten months

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.

Temporal interrelationships among luteolysis, FSH and LH concentrations and follicle deviation in mares

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.

Role of luteinizing hormone in follicle deviation based on manipulating progesterone concentrations in mares

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.

Plasma cortisol levels in captive wild felines after chemical restraint

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.

Is the thoroughbred race-horse under chronic stress?

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.

Puberty and growth rate in thoroughbred fillies

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.