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Campo Grande, Brazil

Sa Filho M.F.,University of Sao Paulo | Penteado L.,FIRMASA IATF | Siqueira G.R.,APTA | Soares J.G.,University of Sao Paulo | And 3 more authors.
Theriogenology | Year: 2013

The present study evaluated the effect of the type of norgestomet ear implant (new vs. used) on the ovarian follicular response (experiment 1) and pregnancy per artificial insemination (AI) (P/AI; experiment 2) of beef heifers subjected to an estradiol plus progestin timed artificial insemination (TAI) program. In experiment 1, 57 cyclic beef heifers were randomly assigned to one of two groups according to the type (new or previously used for 9 days) of norgestomet ear (NORG) implant. At the time of NORG implant insertion, the heifers were treated with 2 mg of intramuscular estradiol benzoate. Eight days later, the NORG implants were removed, and the heifers received an intramuscular administration of 150 μg of d-cloprostenol, 300 IU of equine chorionic gonadotropin, and 0.5 mg of estradiol cypionate. The heifers had their ovaries scanned every 12 hours from the time of NORG implant removal to 96 hours after verifying the occurrence and timing of ovulation. No difference (P = 0.89) was observed in the ovulation rates between the two treatments (new = 80.0%; 24/30 vs. used = 81.5%; 22/27). However, the heifers treated with a used NORG implant had (P = 0.04) higher proportion (36.4%; 8/22) of early ovulation (between 36 and 48 hours after NORG implant removal) compared with the heifers treated with a new NORG implant (8.3%; 2/24). In experiment 2, at the beginning of the synchronization protocol, 416 beef heifers were randomly assigned into two groups, as described in the experiment 1. Two days after the NORG implant removal, the heifers were reassigned to be inseminated at 48 or 54 hours after NORG implant removal. There was an interaction (P = 0.03) between the type of NORG implant and the timing of TAI on P/AI. The timing of insemination only had an effect (P = 0.02) on the P/AI when the heifers were treated with a used NORG implant [(TAI 54 hours = 41.9% (44/105) vs. TAI 48 hours = 58.6% (58/99)]. In conclusion, beef heifers synchronized with a used NORG implant plus estradiol exhibited a higher proportion of earlier ovulations, and TAI in these heifers should be performed 48 hours after removal of used NORG implants. © 2013 Elsevier Inc. Source

Baruselli P.S.,University of Sao Paulo | Ferreira R.M.,University of Sao Paulo | Filho M.F.S.,University of Sao Paulo | Nasser L.F.T.,FIRMASA IATF | And 2 more authors.
Reproduction, Fertility and Development | Year: 2010

Numerous studies have shown that it is possible to manipulate follicular and luteal dynamics, thereby eliminating the need for oestrus detection in embryo transfer (ET) programmes. Fixed-time ET (FTET) protocols are based on the use of gonadotrophin-releasing hormone (GnRH) and prostaglandin (PG) F or progesterone/progestogen (P4)-releasing devices and oestradiol. The FTET protocols increases the proportion of recipients transferred, and therefore pregnancy rates, compared with the use of PGF followed by ET 7 days after oestrus. Furthermore, the addition of equine chorionic gonadotrophin (eCG) to the P4 and oestradiol-based FTET protocols results in an even higher proportion of recipients transferred, and thus higher pregnancy rates. The beneficial effect of eCG treatment may be related to increased growth of the dominant follicle and increased plasma P4 concentrations during the subsequent luteal phase. In Bos taurus Bos indicus recipients, pregnancy rates were positively correlated with the diameter of the corpus luteum (CL) and the number of CL at ET. When repeat-breeder Holstein cows were used as recipients, FTET protocols increased number of recipients transferred and pregnancy rates compared with the traditional PGF-based synchronisation protocols. In conclusion, the use of FTET protocols eliminates the need for the detection of oestrus and results in a greater proportion of recipients transferred and satisfactory pregnancy rates. Thus, FTET optimises the use of recipients, reducing labour and animal handling and facilitating the use of ET. © 2010 IETS. Source

Sa Filho M.F.,University of Sao Paulo | Torres-Junior J.R.S.,Federal University of Maranhao | Penteado L.,FIRMASA IATF | Gimenes L.U.,University of Sao Paulo | And 5 more authors.
Animal Reproduction Science | Year: 2010

A total of 177 Nelore heifers were examined by ultrasonography to determine the presence or absence of a corpus luteum (CL) and received a 3 mg norgestomet ear implant plus 2 mg of estradiol benzoate i.m. On Day 8, implants were removed and 150 μg of d-cloprostenol i.m. was administered. At the time of norgestomet implant removal, heifers with or without CL at the time of initiating treatment were assigned equally and by replicate to be treated with 0 IU (n = 87) or 400 IU (n = 90) eCG i.m. All heifers received 1 mg of EB i.m. on Day 9 and were submitted to fixed-time artificial insemination (FTAI) 30-34 h later. The addition of eCG increased the diameter of the largest follicle (LF) at FTAI (10.6 ± 0.2 mm vs. 9.5 ± 0.2 mm; P = 0.003; mean ± SEM), the final growth rate of the LF (1.14 ± 0.1 mm/day vs. 0.64 ± 0.1 mm/day; P = 0.0009), ovulation rate [94.4% (85/90) vs. 73.6% (64/87); P = 0.0006], the diameter of the CL at Day 15 (15.5 ± 0.3 mm vs. 13.8 ± 0.3 mm; P = 0.0002), serum concentrations of progesterone 5 days after FTAI (6.6 ± 1.0 ng/ml vs. 3.6 ± 0.7 ng/ml; P = 0.0009), and pregnancy per AI [P/AI; 50.0% (45/90) vs. 36.8% (32/87); P = 0.04]. The absence of a CL at the beginning of the treatment negatively influenced the P/AI [30.2% (16/53) vs. 49.2% (61/124); P = 0.01]. Therefore, the presence of a CL (and/or onset of puberty) must be considered in setting up FTAI programs in heifers. In addition, eCG may be an important tool for the enhancement of follicular growth, ovulation, size and function of the subsequent CL, and pregnancy rates in progestin-based FTAI protocols in Bos indicus heifers. © 2009 Elsevier B.V. All rights reserved. Source

Ayres H.,University of Sao Paulo | Ferreira R.M.,University of Sao Paulo | Demetrio C.G.B.,University of Sao Paulo | Sa Filho M.F.,University of Sao Paulo | And 4 more authors.
Theriogenology | Year: 2014

The influence of body condition score (BCS), rump fat thickness (RFAT), and live weight (LW), and the changes in these parameters during the interval from 165 of prepartum (i.e., 125days of prior gestation) to 112 postpartum on first service conception and pregnancy rates were investigated in suckled Zebu (Bos indicus) beef cows (n=266) subjected to timed artificial insemination (TAI) followed by natural mating. The aforementioned parameters were recorded at 165±14days (mean±standard error) prepartum (concurrent with the weaning of previous calf), at parturition, and at 42±7days (at the onset of the synchronization of ovulation protocol), 82±7days (30days after TAI), and 112±7days (60days after TAI) postpartum. At the start of the breeding season (BS), cows were subjected to a synchronization of ovulation program for TAI. Bulls were placed with cows 10days after TAI and remained until the end of the study (112days postpartum). Cows with the highest BCS at parturition had an increased probability of first service conception rate at 60days after TAI (P=0.02) and a reduced probability of occurrence of pregnancy loss (P=0.05). Also, cows had a greater likelihood of conceiving postpartum if they had greater RFAT and BCS at 165±14days prepartum (P=0.01 and P=0.03, respectively) and at parturition (P=0.0007 and P=0.003, respectively). Cows that had an increase in RFAT and BCS during the dry period (i.e., interval from weaning of the previous calf to parturition) also had a greater likelihood of conceiving (P=0.03 and P=0.06, respectively) during the BS. Among the different time points, RFAT and BCS at parturition had the largest impact on risk of conception during the BS. The LW was a poor predictor of conception during the BS (P=0.11-0.68) except for LW at 165±14days prepartum (P=0.01). Collectively, the findings indicated that the likelihood of conception during the BS was highest in cows that had an improvement in RFAT and BCS during the dry period. Therefore, assuring a good nutritional status in the dry period (BCS≥3.0 at 165±14days prepartum and ≥3.25 at parturition) is an important aim to optimize the postpartum conception rate of suckled Zebu beef cows subjected to TAI followed by natural mating. © 2014 Elsevier Inc. Source

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