V. G. Pinheiro

São Paulo State University, São José do Rio Preto, Estado de Sao Paulo, Brazil

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Publications (10)10.22 Total impact

  • [show abstract] [hide abstract]
    ABSTRACT: The objective was to evaluate when the LH reserve was re-established in postpartum Nellore (Bos indicus) cows by evaluating the response of the hypothalamic-pituitary axis responsiveness to exogenous GnRH or estradiol benzoate (EB). Additionally, we tested the influence of dietary supplementation (SUPL) and calf removal (CR) on the duration of postpartum anestrus. Ninety multiparous lactating Nellore cows were randomly assigned to eight groups. The EB and GnRH groups received 1.0 mg EB (N = 7), and 50 μg lecireline (N = 16), respectively. Additional cows were given the same hormones, and subjected to either nutritional supplementation (EB-SUPL, N = 9; GnRH-SUPL, N = 16), or calf removal at 72 hours after calving (EB-CR, N = 4; GnRH-CR, N = 13). The remaining two groups were the LH (12.5 mg, N = 14) and control groups (saline, N = 11). Hormones were administered weekly from 7 (±5) days postpartum to first ovulation (detection of a CL during a weekly ultrasonographic examination). Blood samples were collected just before and 2 hours (GnRH, LH, and control groups) or 18 hours (EB groups) after hormone or saline (control) administration. Ovulation occurred as early as 15 days postpartum in the GnRH group. The mean ± SEM intervals (days) from calving to first ovulation were EB, 87.7 ± 4.2; EB-CR, 20.3 ± 1.2; EB-SUPL, 60.3 ± 3.2; GnRH, 40.4 ± 2.1; GnRH-CR, 21.0 ± 1.1; GnRH-SUPL, 26.4 ± 1.1; LH, 35.6 ± 1.1; and control, 60.9 ± 2.1. We concluded that there was sufficient LH in the pituitary gland (of Nellore cows) from the second week postpartum to induce ovulation in response to exogenous GnRH. Additionally, calf removal and nutritional supplementation reduced, by 2 to 4 weeks, the interval from calving to an LH increase and ovulation induced by GnRH or EB.
    Theriogenology 01/2013; · 2.08 Impact Factor
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    ABSTRACT: The presence of calf, body condition score, energy balance, number of births (multiparous vs primiparous) and breed are factors that influence the duration of postpartum anoestrus in beef cows. The objective of the present study was to evaluate, during early postpartum, the time of re-establishment of pituitary LH stocks, measured by the hypothalamic-pituitary-axis responsiveness to exogenous administration of gonadotropin-releasing hormone (GnRH) or oestradiol benzoate (EB). Multiparous lactating Nellore cows (Bos indicus, n=65) were randomly allocated into 6 groups, according to the hormonal treatment: EB group (1.0mg of EB, IM, n=7), GnRH group (50μg of lecireline, IM, n=16). The EB-supplemented (SUP; n=9) and GnRH-SUP (n=16) groups received the same treatments specified above and were SUP with a balanced diet, based on cotton meal and ground corn (3.5kgcow(-1) per day). Additionally, animals from EB-calf removed (CR; n=4) and GnRH-CR (n=13) groups received the same treatments of EB and GnRH group, respectively and had their CR shortly after parturition. The hormones were administered weekly, from 7 days postpartum (±5 days) until the occurrence of the first ovulation, which was determined by the presence of corpus luteum during ovarian ultrasonography performed weekly. Blood samples were collected just before and 2h (GnRH groups) or 18h (EB groups) after hormone administration, in order to determine LH concentration by radioimmunoassay. Data were analysed by ANOVA. Mean values in days (± standard error of the means) for the first postpartum LH surge were EB (73.0±5.2); EB-CR (16.7±5.8); EB-SUP (41.7±6.7); GnRH (32.3±3.0); GnRH-CR (11.0±3.5); GnRH-SUP (15.6±2.8). There were significant differences (P<0.05) between groups EB vs EB-CR; EB vs EB-SUP; BE vs GnRH; GnRH vs GnRH-CR; GnRH vs GnRH-SUP and a tendency between EB-SUP vs EB-CR (P<0.10). Results indicate that from the second week postpartum, there is sufficient LH in the pituitary to induce ovulation after GnRH or EB administration. However, the cows from the EB group ovulated later than animals from the other groups, possibly due to the sensitivity of the hypothalamus to negative feedback of estrogens, inhibiting the pre-ovulatory LH surge. Additionally, CR and food SUP reduced in 2 to 4 weeks the time of the first postpartum LH surge induced by GnRH or EB in Nellore cows.
    Reproduction Fertility and Development 12/2011; 24(1):144. · 2.58 Impact Factor
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    ABSTRACT: The objective was to evaluate the effects of plasma progesterone (P4) concentrations and exogenous eCG on ovulation and pregnancy rates of pubertal Nellore heifers in fixed-time artificial insemination (FTAI) protocols. In Experiment 1 (Exp. 1), on Day 0 (7 d after ovulation), heifers (n = 15) were given 2 mg of estradiol benzoate (EB) im and randomly allocated to receive: an intravaginal progesterone-releasing device containing 0.558 g of P4 (group 0.5G, n = 4); an intravaginal device containing 1 g of P4 (group 1G, n = 4); 0.558 g of P4 and PGF(2α) (PGF; 150 μg d-cloprostenol, group 0.5G/PGF, n = 4); or 1 g of P4 and PGF (group 1G/PGF, n = 3). On Day 8, PGF was given to all heifers and intravaginal devices removed; 24 h later (Day 9), all heifers were given 1 mg EB im. In Exp. 2, pubertal Nellore heifers (n = 292) were treated as in Exp. 1, with FTAI on Day 10 (30 to 36 h after EB). In Exp. 3, pubertal heifers (n = 459) received the treatments described for groups 0.5G/PGF and 1G/PGF and were also given 300 IU of eCG im (groups 0.5G/PGF/eCG and 1G/PGF/eCG) at device removal (Day 8). In Exp. 1, plasma P4 concentrations were significantly higher in heifers that received 1.0 vs 0.588 g P4, and were significantly lower in heifers that received PGF on Day 0. In Exp. 2 and 3, there were no significant differences among groups in rates of ovulation (65-77%) or pregnancy (Exp. 2: 26-33%; Exp. 3: 39-43%). In Exp. 3, diameter of the dominant ovarian follicle on Day 9 was larger in heifers given 0.558 g vs 1.0 g P4 (10.3 ± 0.2 vs 9.3 ± 0.2 mm; P < 0.01). In conclusion, lesser amounts of P4 in the intravaginal device or PGF on Day 0 decreased plasma P4 from Days 1 to 8 and increased diameter of the dominant follicle on Day 9. However, neither of these nor 300 IU of eCG on Day 8 significantly increased rates of ovulation or pregnancy.
    Theriogenology 01/2011; 75(1):17-23. · 2.08 Impact Factor
  • L. A. Lima, V. G. Pinheiro, J. R. Cury, C. M. Barros
    Reproduction Fertility and Development - REPROD FERT DEVELOP. 01/2010; 22(1).
  • Reproduction Fertility and Development - REPROD FERT DEVELOP. 01/2010; 22(1).
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    ABSTRACT: The study evaluated, in early post-partum anoestrous Nelore cows, if the increase in plasma oestradiol (E2) concentrations in the pre-ovulatory period and/or progesterone priming (P4 priming) preceding ovulation, induced by hormonal treatment, reduces the endogenous release of prostaglandin PGF(2)α and prevents premature lysis of the corpus luteum (CL). Nelore cows were subjected to temporary calf removal for 48 h and divided into two groups: GPE/eCG group (n = 10) and GPG/eCG group (n = 10). Animals of the GPE/eCG group were treated with a GnRH agonist. Seven days later, they received 400 IU of eCG, immediately after PGF(2)α treatment, and on day 0, 1.0 mg of oestradiol benzoate (EB). Cows of the GPG/eCG group were similarly treated as those of the GPE/eCG group, except that EB was replaced with a second dose of GnRH. All animals were challenged with oxytocin (OT) 9, 12, 15 and 18 days after EB or GnRH administration and blood samples were collected before and 30 min after OT. Irrespective of the treatments, a decline in P4 concentration on day 18 was observed for cows without P4 priming. However, animals exposed to P4 priming, treated with EB maintained high P4 concentrations (8.8 ± 1.2 ng/ml), whereas there was a decline in P4 on day 18 (2.1 ± 1.0 ng/ml) for cows that received GnRH to induce ovulation (p < 0.01). Production of 13,14-dihydro-15-keto prostaglandin F(2)α (PGFM) in response to OT increased between days 9 and 18 (p < 0.01), and this increase tended to be more evident in animals not exposed to P4 priming (p < 0.06). In conclusion, the increase in E2 during the pre-ovulatory period was not effective in inhibiting PGFM release, which was lower in P4-primed than in non-primed animals. Treatment with EB promoted the maintenance of elevated P4 concentrations 18 days after ovulation in P4-primed animals, indicating a possible beneficial effect of hormone protocols containing EB in animals with P4 priming.
    Reproduction in Domestic Animals 05/2009; 45(5):881-7. · 1.39 Impact Factor
  • Reproduction Fertility and Development - REPROD FERT DEVELOP. 01/2009; 21(1).
  • [show abstract] [hide abstract]
    ABSTRACT: The objective was to evaluate the effects of temporary calf removal (TCR), eCG administration, or both, in a progesterone-based protocol. Suckled Nellore cows (40-80 d postpartum, n=443) with body condition scores from 2.0 to 3.5 (5-point scale) on three farms were all given a synchronizing protocol (PEPE). At the start (designated Day 0), cows were given an intravaginal device (1.0 g of progesterone) and 2.5mg of estradiol benzoate (EB) im. On Day 8, the device was removed and cows were given PGF(2 alpha) (150 microg of D-cloprostenol im), followed in 24h by 1.0mg EB im, and 30-36 h thereafter, fixed-time AI. The design was a 2 x 2 factorial; main effects were TCR (54-60 h; from device removal to FTAI) and eCG treatment (300 IU im, concurrent with PGF(2 alpha)). Transrectal ultrasonography was done on Days -10 and 0 to detect anestrus (absence of a CL at both examinations) and approximately 30 d after FTAI (pregnancy diagnosis). Data were analyzed by logistic regression. The following variables did not significantly affect pregnancy rates: farm, postpartum interval, cyclicity, inseminators, and semen (sire). Overall, 77% of the cows were deemed anestrus. Pregnancy rates were similar (P>0.05) among treatment groups: Control (54/108=50.0%), TCR (44/106=41.5%), eCG (63/116=54.3%), and TCR+eCG (49/113=43.4%). Pregnancy rate was higher in multiparous than primiparous cows (186/360, 51.7% vs. 24/83, 28.9%, P<0.01), but was not significantly affected by cyclicity status or body condition score. In conclusion, temporary calf removal, eCG, or both, did not significantly increase pregnancy rate to timed-insemination in a progesterone-based synchronization protocol in postpartum Nellore cows with acceptable body condition.
    Theriogenology 10/2008; 71(3):519-24. · 2.08 Impact Factor
  • Reproduction Fertility and Development - REPROD FERT DEVELOP. 01/2006; 18(2).
  • Reproduction Fertility and Development - REPROD FERT DEVELOP. 01/2006; 18(2).

Publication Stats

9 Citations
10.22 Total Impact Points

Institutions

  • 2008–2013
    • São Paulo State University
      • • Departamento de Farmacologia
      • • Departamento de Produção Animal
      São José do Rio Preto, Estado de Sao Paulo, Brazil
  • 2011
    • University of São Paulo
      • Instituto de Biociências (IB) (São Paulo)
      São Paulo, Estado de Sao Paulo, Brazil