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G. C. Lamb - One of the best experts on this subject based on the ideXlab platform.

  • Contrasting effects of progesterone on fertility of dairy and Beef Cows.
    Journal of dairy science, 2016
    Co-Authors: J.s. Stevenson, G. C. Lamb
    Abstract:

    The role of progesterone in maintaining pregnancy is well known in the bovine. Subtle differences exist between dairy and Beef Cows because of differing concentrations of progesterone during recrudescence of postpartum estrous cycles, rate of follicular growth and maturation, proportions of 2- and 3-follicular wave cycles, and other effects on pregnancy outcomes per artificial insemination (P/AI). Because proportions of anovulatory Cows before the onset of the artificial insemination (AI) period are greater and more variable in Beef (usually ranging from 30 to 70%) than dairy (25%) Cows, AI programs were developed to accommodate anovulatory and cycling Beef Cows enrolled therein. Incorporating a progestin as part of an AI program in Beef Cows improved P/AI by reducing the proportion of Cows having premature luteal regression and short post-AI luteal phases. In both genotypes, prolonged dominant follicle growth in a reduced progesterone milieu resulted in increased (1) LH pulses, (2) preovulatory follicle diameter, and (3) concentrations of estradiol and a subsequently larger corpora lutea (CL). In contrast, the progesterone milieu during growth of the ovulatory follicle in an ovulation control program does not seem to affect subsequent P/AI in Beef Cows, whereas in dairy Cows follicle development in an elevated compared with a low progesterone environment increases P/AI. Progesterone status in Beef Cows at the onset of ovulation synchronization is not related to P/AI in multiparous Cows, whereas P/AI was suppressed in primiparous Cows that began a timed AI program in a low-progesterone environment. In timed AI programs, elevated concentrations of progesterone just before PGF2α and reduced concentrations at AI are critical to maximizing subsequent P/AI in dairy Cows, but seemingly much less important in Beef Cows. By inducing ancillary CL and increasing concentrations of progesterone, human chorionic gonadotropin may increase P/AI when administered to Beef Cows 7d after AI or at embryo transfer, and its success seems to depend on induction of ancillary CL, whereas in dairy Cows increased fertility was detected in Cows with multiple CL, human chorionic gonadotropin-enhanced progesterone from original CL, or both. Pregnancy losses after AI are less frequent in Beef Cows and are not associated with pre-AI progesterone or cycling status, whereas losses in dairy Cows are inversely related to progesterone and adversely affected in anovular dairy Cows. Genotype and nutritional management likely influence several physiological differences including circulating concentrations of progesterone and responses to supplemental progesterone.

  • progesterone based estrous synchronization protocols in non suckled and suckled primiparous bos indicus Beef Cows
    Animal Reproduction Science, 2010
    Co-Authors: O Sa G Filho, G. C. Lamb, C C Dias, Jose Luiz Moraes Vasconcelos
    Abstract:

    Abstract In Experiment 1, effects of an intravaginal progesterone insert (CIDR) for synchronization of estrus in non-suckled cycling primiparous Bos indicus Beef Cows were evaluated. Cows received either no treatment (Control), prostaglandin F 2α (PGF), or CIDR (6 d) + prostaglandin F 2α (CIDR + PGF). There were greater ( P 2α  + 48 h temporary weaning (CIDR + PGF + TW) associated or not with equine chorionic gonadotropin (eCG) for synchronization of estrus in suckled primiparous B. indicus Beef Cows was evaluated. Cows were assigned to receive either no treatment (Control), CIDR + PGF + TW, CIDR + PGF + TW + 200 IU of eCG, or CIDR + PGF + TW + 400 IU of eCG. There were greater ( P P

  • progesterone based estrous synchronization protocols in non suckled and suckled primiparous bos indicus Beef Cows
    Animal Reproduction Science, 2010
    Co-Authors: O Sa G Filho, G. C. Lamb, C C Dias, Jose Luiz Moraes Vasconcelos
    Abstract:

    In Experiment 1, effects of an intravaginal progesterone insert (CIDR) for synchronization of estrus in non-suckled cycling primiparous Bos indicus Beef Cows were evaluated. Cows received either no treatment (Control), prostaglandin F(2alpha) (PGF), or CIDR (6 d) + prostaglandin F(2alpha) (CIDR + PGF). There were greater (P < 0.05) percentages of Cows inseminated and pregnant in 4 d of breeding season in CIDR + PGF (81.6%; 48.7%) than in PGF (53.8%; 32.5%) and Control Cows (14.6%; 8.5%). In Experiment 2, efficacy of a treatment with CIDR (6 d) + prostaglandin F(2alpha) + 48 h temporary weaning (CIDR + PGF + TW) associated or not with equine chorionic gonadotropin (eCG) for synchronization of estrus in suckled primiparous B. indicus Beef Cows was evaluated. Cows were assigned to receive either no treatment (Control), CIDR + PGF + TW, CIDR + PGF + TW + 200 IU of eCG, or CIDR + PGF + TW + 400 IU of eCG. There were greater (P < 0.05) percentages of insemination and pregnancy in 4 d of breeding season in treatment groups (47.0%; 27.5%) than in Control Cows (4.5%; 3.0%) and in Cows treated with eCG (50.9%; 29.4%) than in Cows treated only with CIDR + PGF + TW (39.4%; 23.7%). No effects of eCG dosage were detected. The percentage of Cows inseminated and pregnant in a 30 d breeding season were greater (P < 0.05) in Cows assigned to synchronization treatments (53.3%; 37.2%) than in Control Cows (35.3%; 21.4%). In the beginning of the BS, non-suckled primiparous Cows treated with CIDR + PGF with estrous cycles having been initiated following calving had greater estrous detection and pregnancy rates than PGF and Control Cows, and suckled primiparous Cows had improved estrous detection and pregnancy rates when eCG was associated with CIDR + PGF + TW.

  • Postpartum endometrial cytology in Beef Cows
    Theriogenology, 2008
    Co-Authors: Natalia R. Santos, G. C. Lamb, David R. Brown, Robert O. Gilbert
    Abstract:

    Abstract The objectives were to characterize postpartum endometrial cytology and to determine the prevalence of subclinical endometrial inflammation and its impact on reproduction in Beef Cows. Samples for endometrial cytology (low-volume uterine lavage) were obtained from 135 of 137 Angus Cows (2–87d postpartum) in northern Minnesota, 26d before breeding started. Agreement between examiners for subjective inflammation scores was very high (kappa=0.971); the correlation between these scores and PMN counts was high ( r =0.83; P P P >0.10). Although inflammation later in the postpartum period apparently impaired subsequent reproduction in dairy Cows, in Cows >50 d postpartum at sample collection in the present study, no cytological parameter significantly predicted final pregnancy status or day of conception. Previous twinning increased the risk of subclinical endometritis ( P =0.02), but not the probability of becoming pregnant ( P =0.14). In conclusion, we inferred that Beef Cows had the ability to clear uterine inflammation after resumption of ovarian cyclicity.

  • supplemental norgestomet progesterone or melengestrol acetate increases pregnancy rates in suckled Beef Cows after timed inseminations
    Journal of Animal Science, 2003
    Co-Authors: J.s. Stevenson, Sandra K. Johnson, G. C. Lamb, M A Medinabritos, David M Grieger, Keith R Harmoney, J A Cartmill, S Z Elzarkouny, C R Dahlen, T.j. Marple
    Abstract:

    In Exp. 1, 187 lactating Beef Cows were treated with injections of GnRH 7 d before and 48 h after prostaglandin F2alpha (PGF2alpha; Cosynch) or with Cosynch plus a 7-d treatment with an intravaginal progesterone (P4)-releasing insert (CIDR-B; Cosynch + CIDR). In Exp. 2, 183 lactating Beef Cows were treated with the Cosynch protocol or with Cosynch plus a 7-d treatment with norgestomet (Cosynch + NORG). In Exp. 1 and 2, blood samples for later P4 analyses were collected on d -17, -7 (first GnRH injection), 0 (PGF2alpha injection), and at timed artificial insemination (TAI; 48 h after PGF2alpha). In Exp. 3, 609 lactating Beef Cows were treated with the Cosynch + CIDR protocol or were fed 0.5 mg of melengestrol acetate (MGA) per day for 14 d before initiating the Cosynch protocol 12 d after the 14th d of MGA feeding (MGA + Cosynch). Blood samples were collected as in Exp. 1 and 2, plus additional samples on d -33 and -19 before PGF2alpha. In Exp. 4, 360 lactating Beef Cows were treated with a Cosynch + CIDR protocol, with TAI occurring at either 48 or 60 h after PGF2alpha, while receiving either GnRH or saline to form four treatments. Blood samples were collected as in Exp. 1 and 2. In Exp. 1, addition of P4 reduced the ability of the first GnRH injection to induce ovulation in anestrous Cows with low P4 before PGF2alpha but improved (P = 0.06) pregnancy rates (61 vs 66%). In Exp. 2, the addition of NORG mimicked P4 by likewise increasing (P < 0.01) pregnancy rates (31 vs 51%) beyond those after Cosynch. In Exp. 3, the Cosynch + CIDR protocol increased (P < 0.001) pregnancy rates from 46 to 55% compared to the MGA + Cosynch protocol. In Exp. 4, administration of GnRH at TAI improved (P < 0.05) pregnancy outcomes (50 vs 42%), whereas timing of TAI had limited effects. We conclude that a progestin treatment concurrent with the Cosynch protocol improved pregnancy outcomes in all experiments, but pretreatment of Cows with MGA was not as effective as the CIDR insert or NORG implants in this Cosynch-TAI model. Most of the improvement in pregnancy rates was associated with the increase in pregnancy rates of anestrous Cows, regardless of whether ovulation was successfully induced in response to GnRH 7 d before PGF2alpha. Injection of GnRH at TAI following the Cosynch + CIDR protocol increased pregnancy rates in cycling Cows with high P4 before the PGF2alpha injection and in anestrous Cows with low P4 before PGF2alpha injection.

Jose Luiz Moraes Vasconcelos - One of the best experts on this subject based on the ideXlab platform.

  • use of bovine pregnancy associated glycoproteins to predict late embryonic mortality in postpartum nelore Beef Cows
    Theriogenology, 2016
    Co-Authors: K G Pohler, R F G Peres, Jonathan A Green, H B Graff, T Martins, Jose Luiz Moraes Vasconcelos, M F Smith
    Abstract:

    Abstract The primary objective was to determine if circulating concentration of bovine pregnancy-associated glycoproteins (bPAGs) on Day 30 after artificial insemination (AI) may serve as a marker of late embryonic mortality in Bos indicus (Nelore) Beef Cows. In experiment 1, postpartum Nelore Beef Cows (n = 56) were artificially inseminated at a fixed time (Day 0) after synchronization of ovulation. Serum samples were collected on Days 0, 21, 24, 27, and 30 after AI. The first significant increase (P

  • progesterone based estrous synchronization protocols in non suckled and suckled primiparous bos indicus Beef Cows
    Animal Reproduction Science, 2010
    Co-Authors: O Sa G Filho, G. C. Lamb, C C Dias, Jose Luiz Moraes Vasconcelos
    Abstract:

    Abstract In Experiment 1, effects of an intravaginal progesterone insert (CIDR) for synchronization of estrus in non-suckled cycling primiparous Bos indicus Beef Cows were evaluated. Cows received either no treatment (Control), prostaglandin F 2α (PGF), or CIDR (6 d) + prostaglandin F 2α (CIDR + PGF). There were greater ( P 2α  + 48 h temporary weaning (CIDR + PGF + TW) associated or not with equine chorionic gonadotropin (eCG) for synchronization of estrus in suckled primiparous B. indicus Beef Cows was evaluated. Cows were assigned to receive either no treatment (Control), CIDR + PGF + TW, CIDR + PGF + TW + 200 IU of eCG, or CIDR + PGF + TW + 400 IU of eCG. There were greater ( P P

  • progesterone based estrous synchronization protocols in non suckled and suckled primiparous bos indicus Beef Cows
    Animal Reproduction Science, 2010
    Co-Authors: O Sa G Filho, G. C. Lamb, C C Dias, Jose Luiz Moraes Vasconcelos
    Abstract:

    In Experiment 1, effects of an intravaginal progesterone insert (CIDR) for synchronization of estrus in non-suckled cycling primiparous Bos indicus Beef Cows were evaluated. Cows received either no treatment (Control), prostaglandin F(2alpha) (PGF), or CIDR (6 d) + prostaglandin F(2alpha) (CIDR + PGF). There were greater (P < 0.05) percentages of Cows inseminated and pregnant in 4 d of breeding season in CIDR + PGF (81.6%; 48.7%) than in PGF (53.8%; 32.5%) and Control Cows (14.6%; 8.5%). In Experiment 2, efficacy of a treatment with CIDR (6 d) + prostaglandin F(2alpha) + 48 h temporary weaning (CIDR + PGF + TW) associated or not with equine chorionic gonadotropin (eCG) for synchronization of estrus in suckled primiparous B. indicus Beef Cows was evaluated. Cows were assigned to receive either no treatment (Control), CIDR + PGF + TW, CIDR + PGF + TW + 200 IU of eCG, or CIDR + PGF + TW + 400 IU of eCG. There were greater (P < 0.05) percentages of insemination and pregnancy in 4 d of breeding season in treatment groups (47.0%; 27.5%) than in Control Cows (4.5%; 3.0%) and in Cows treated with eCG (50.9%; 29.4%) than in Cows treated only with CIDR + PGF + TW (39.4%; 23.7%). No effects of eCG dosage were detected. The percentage of Cows inseminated and pregnant in a 30 d breeding season were greater (P < 0.05) in Cows assigned to synchronization treatments (53.3%; 37.2%) than in Control Cows (35.3%; 21.4%). In the beginning of the BS, non-suckled primiparous Cows treated with CIDR + PGF with estrous cycles having been initiated following calving had greater estrous detection and pregnancy rates than PGF and Control Cows, and suckled primiparous Cows had improved estrous detection and pregnancy rates when eCG was associated with CIDR + PGF + TW.

T. W. Geary - One of the best experts on this subject based on the ideXlab platform.

  • preovulatory estradiol and the establishment and maintenance of pregnancy in suckled Beef Cows
    Journal of Animal Science, 2013
    Co-Authors: E M Jinks, K G Pohler, M F Smith, G. A. Perry, M D Macneil, J A Atkins, A J Roberts, R C Waterman, L J Alexander, T. W. Geary
    Abstract:

    In postpartum Beef Cows, GnRH-induced ovulation of small dominant follicles decreased pregnan- cy rates and increased late embryonic/fetal mortality. In Exp. 1, single ovulation reciprocal embryo transfer (ET) was used to examine the relationship between preovula- tory serum concentrations of estradiol at GnRH-induced ovulation in donor and recipient Cows and establishment and maintenance of pregnancy. Suckled Beef Cows (n = 1,164) were administered GnRH (GnRH1, 100 μg) on d -9 (GnRH1), PGF 2α on d -2, and GnRH2 (GnRH2, 100 μg) on d 0 (CO-Synch protocol) either with (donors; n = 810) or without (recipients; n = 354) AI. Single embryos (n = 394) or oocytes (n = 45) were recovered from the donor Cows (d 7; ET) and all live embryos were trans- ferred into recipients. Serum concentration of estradiol at GnRH2 was positively correlated with follicle size at GnRH2 (r = 0.45, P < 0.01) and progesterone at ET (r =0.34, P < 0.01). Donor Cows with greater estradiol at GnRH2 were more likely to yield an embryo than an unfertilized oocyte (P < 0.01). Donor and recipient Cows were retrospectively divided into 4 groups (low estradiol (<8.4 pg/mL) or high estradiol (≥8.4 pg/mL)) based on serum concentration of estradiol at GnRH2. Pregnancy rate at d 27 for low-low (n = 78), low-high (n = 80), high-low (n = 91), and high-high (n = 101) groups (donor-recipient, respectively) was 45, 65, 43, and 61% respectively (P < 0.02). Because recipient Cows with greater estradiol concentration at GnRH2 had greater pregnancy rates in Exp. 1, the objective of Exp. 2 was to evaluate the effect of estradiol supplementation on pregnancy rate. Ovulation was synchronized in suckled Beef Cows (n = 600) using the CO-Synch protocol with the insertion of a controlled internal drug release (CIDR; intravaginal progesterone supplement) from d -9 until d -2. Approximately one-half of the Cows (n = 297) received an injection of estradiol cypionate (ECP; 0.5 mg intramuscularly) 24 h before AI. Compared with the no treatment (Control) Cows, ECP treatment increased (P < 0.01) pregnancy rates of Cows induced to ovulate smaller dominant follicles (<12.2 mm). In conclusion, GnRH-induced ovulation of small dominant follicles was associated with reduced serum estradiol, fertiliza- tion rate (donor Cows), and pregnancy establishment (recipient Cows). Furthermore, ECP supplementation during the preovulatory period increased pregnancy rates in Cows induced to ovulate smaller dominant follicles.

  • effect of ovulatory follicle size and expression of estrus on progesterone secretion in Beef Cows
    Journal of Animal Science, 2008
    Co-Authors: D C Busch, T. W. Geary, J A Atkins, J F Bader, D J Schafer, David J Patterson, M F Smith
    Abstract:

    Induced ovulation of small dominant follicles (SF, 12 mm). Experiment 1 characterized P4 concentrations from ovulation to subsequent estrus among GnRH-in- duced or spontaneously ovulated SF (≤ 11 mm) or LF (≥ 12 mm) to determine if P4 secretion by CL formed from GnRH-induced SF remains lower postovulation in nonlactating Beef Cows. Nonlactating Beef Cows were induced to ovulate 48 h after PGF2α (CO-Synch; GnRH on d −9, PGF2α on d −2, and GnRH on d 0) or exhibited estrus and spontaneously ovulated after PGF2α. Follicle size was measured at the second GnRH in Cows induced to ovulate or ∼3 h after the onset of estrus for Cows that ovulated spontaneously. Cows were classified into 1 of 4 groups: 1) GnRH-induced ovulation-SF (≤ 11 mm; Ind- SF; n = 9); 2) GnRH-induced ovulation-LF (≥ 12 mm; Ind-LF; n = 16); 3) spontaneous ovulation-SF (≤ 11 mm; Spon-SF; n = 8); 4) spontaneous ovulation-LF (≥ 12 mm; Spon-LF; n = 22). Serum concentrations of P4 from d 3 to 15 were reduced in the Ind-SF compared with the Ind-LF (P = 0.05), Spon-SF (P = 0.07), and Spon-

  • ability of intravaginal progesterone inserts and melengestrol acetate to induce estrous cycles in postpartum Beef Cows
    Journal of Animal Science, 2004
    Co-Authors: M F Smith, George Perry, T. W. Geary
    Abstract:

    Postpartum anestrous interval in Beef Cows is a major factor contributing to reproductive failure during a defined breeding season. Our objectives were to determine the ability of a controlled internal drug-releasing device (CIDR, 1.9 g of progesterone), a normal dose of melengestrol acetate (MGA, 0.5 mg x cow(-1) x d(-1)), or a high dose of MGA (4.0 mg x cow(-1) x d(-1)) to induce ovulation and to eliminate short estrous cycles. Multiparous Beef Cows (n = 100) were equally assigned to one of four treatments: CIDR, normal MGA, high MGA, or control by age, days postpartum, body condition, and body weight. All Cows were fed carrier (0.9072 kg x cow(-1) x d(-1)) with (normal MGA, 0.55 mg/kg; high MGA, 4.41 mg/kg) or without MGA for 7 d (d -6 to 0). On d -6, CIDR were inserted and then removed on d 0. Estrous behavior was monitored continuously from d -6 until 29 using HeatWatch electronic mount detectors. Blood was collected on d -13, and three times weekly from d -6 to 29. Treatment influenced (P = 0.03) the percentage of Cows that were detected in standing estrus. Beginning on d 2, more CIDR-treated Cows had exhibited standing estrus compared with high MGA-treated or control Cows, but CIDR- and normal MGA-treated Cows did not differ. The percentage of CIDR-treated Cows that had ovulated was greater (P 1 ng/mL for > or = 10 d) was greater (P < 0.01) in CIDR-treated Cows (14.0 +/- 0.8 d; 20/20, 100%) compared with normal MGA-treated (6.2 +/- 1.0 d; 3/13, 23%), high MGA-treated (9.6 +/- 1.0 d; 8/14, 57%), or control Cows (6.1 +/- 0.9 d; 4/17, 24%), and greater (P < 0.03) in high MGA-treated Cows than in normal MGA-treated or control Cows. In the present study, treatment of early postpartum suckled Beef Cows with CIDR induced ovulation and initiated estrous cycles with a normal luteal life span in more Cows than did treatment with MGA. Treatment with MGA (normal or high dose) did not induce ovulation earlier than in control Cows, but a high dose of MGA increased the percentage of Cows with normal luteal life spans following the first ovulation postpartum.

  • Ability of CIDRs or Melengestrol Acetate to Initiate Estrous Cycles in Early Postpartum Beef Cows
    2004
    Co-Authors: G. A. Perry, T. W. Geary
    Abstract:

    Postpartum anestrous interval in Beef Cows is a major factor contributing to reproductive failure during a defined breeding season. Our objectives were to determine the ability of a controlled internal drug-releasing device (CIDR), or melengestrol acetate (MGA) to induce ovulation and to eliminate short estrous cycles. Multiparous Beef Cows (n = 75) were equally assigned by age, days postpartum, body condition, and body weight to one of three treatments: CIDR, MGA, or control. All Cows were fed carrier (2 lbs•cow•day) with MGA (0.25 mg/lb) or without MGA for 7 days (day -6 to 0). On day -6, CIDR were inserted and were removed on d 0. Estrous behavior was monitored continuously from day -6 until 29 using HeatWatch electronic mount detectors. Blood was collected three times weekly from day -6 to 29. Treatment influenced (P = 0.03) the percentage of Cows that were detected in standing estrus. Beginning on d 2, more CIDRtreated Cows had exhibited standing estrus compared to control Cows, but CIDRand MGAtreated Cows did not differ. The percentage of CIDR-treated Cows that had ovulated was greater (P 1 ng/mL for ≥ 10 d) was greater (P < 0.01) in CIDR-treated Cows (14.0 ± 0.8 days; 20/20, 100%) compared with MGA(6.2 ± 1.0 days; 3/13, 23%), or control-treated Cows (6.1 ± 0.9 days; 4/17, 24%). In the present

  • effects of a timed insemination following synchronization of ovulation using the ovsynch or co synch protocol in Beef Cows
    The Professional Animal Scientist, 1998
    Co-Authors: T. W. Geary, J C Whittier, F A Thrift, S L Dolezal
    Abstract:

    Abstract This study compared pregnancy rates of suckled Beef Cows that were time inseminated following synchronization of ovulation using the Ovsynch protocol. Multiparous Beef Cows (n=771) within each of three locations were stratified by breed type, age, postpartum interval, and AI sire, and randomly allotted to receive either the Ovsynch or CO-Synch protocol. The Ovsynch protocol consisted of an injection of GnRH (100 μg) on d 0, an injection of PGF 2α on d 7, another injection of GnRH (100 μg) on d 9, and timed insemination on d 10. The CO-Synch protocol consisted of the same hormone injection schedule as the Ovsynch protocol, but Cows were time inseminated on d 9, when the second GnRH injection was administered. Pregnancy rates did not differ between treatments at each location ( P >0.1). However, when data were pooled across location, pregnancy rate was higher ( P =0.02) for Cows that received the Ovsynch protocol (57%) than for Cows that received the CO-Synch protocol (49%). No difference ( P >0.1) in pregnancy rate due to cow age, postpartum interval, body condition score, age by treatment, or postpartum interval by treatment was detected among pooled data. Among Cows with a body condition score of 6.0 or greater, pregnancy rates were higher ( P =0.04) for Ovsynch treated Cows (72%) than for CO-Synch treated Cows (53%). These data demonstrate that the Ovsynch and CO-Synch protocols result in acceptable pregnancy rates to a timed insemination in Beef Cows. Whether the increase in pregnancy rates obtained using the Ovsynch protocol will warrant handling Cows a fourth time for insemination will likely vary by management intensity.

O Sa G Filho - One of the best experts on this subject based on the ideXlab platform.

  • progesterone based estrous synchronization protocols in non suckled and suckled primiparous bos indicus Beef Cows
    Animal Reproduction Science, 2010
    Co-Authors: O Sa G Filho, G. C. Lamb, C C Dias, Jose Luiz Moraes Vasconcelos
    Abstract:

    Abstract In Experiment 1, effects of an intravaginal progesterone insert (CIDR) for synchronization of estrus in non-suckled cycling primiparous Bos indicus Beef Cows were evaluated. Cows received either no treatment (Control), prostaglandin F 2α (PGF), or CIDR (6 d) + prostaglandin F 2α (CIDR + PGF). There were greater ( P 2α  + 48 h temporary weaning (CIDR + PGF + TW) associated or not with equine chorionic gonadotropin (eCG) for synchronization of estrus in suckled primiparous B. indicus Beef Cows was evaluated. Cows were assigned to receive either no treatment (Control), CIDR + PGF + TW, CIDR + PGF + TW + 200 IU of eCG, or CIDR + PGF + TW + 400 IU of eCG. There were greater ( P P

  • progesterone based estrous synchronization protocols in non suckled and suckled primiparous bos indicus Beef Cows
    Animal Reproduction Science, 2010
    Co-Authors: O Sa G Filho, G. C. Lamb, C C Dias, Jose Luiz Moraes Vasconcelos
    Abstract:

    In Experiment 1, effects of an intravaginal progesterone insert (CIDR) for synchronization of estrus in non-suckled cycling primiparous Bos indicus Beef Cows were evaluated. Cows received either no treatment (Control), prostaglandin F(2alpha) (PGF), or CIDR (6 d) + prostaglandin F(2alpha) (CIDR + PGF). There were greater (P < 0.05) percentages of Cows inseminated and pregnant in 4 d of breeding season in CIDR + PGF (81.6%; 48.7%) than in PGF (53.8%; 32.5%) and Control Cows (14.6%; 8.5%). In Experiment 2, efficacy of a treatment with CIDR (6 d) + prostaglandin F(2alpha) + 48 h temporary weaning (CIDR + PGF + TW) associated or not with equine chorionic gonadotropin (eCG) for synchronization of estrus in suckled primiparous B. indicus Beef Cows was evaluated. Cows were assigned to receive either no treatment (Control), CIDR + PGF + TW, CIDR + PGF + TW + 200 IU of eCG, or CIDR + PGF + TW + 400 IU of eCG. There were greater (P < 0.05) percentages of insemination and pregnancy in 4 d of breeding season in treatment groups (47.0%; 27.5%) than in Control Cows (4.5%; 3.0%) and in Cows treated with eCG (50.9%; 29.4%) than in Cows treated only with CIDR + PGF + TW (39.4%; 23.7%). No effects of eCG dosage were detected. The percentage of Cows inseminated and pregnant in a 30 d breeding season were greater (P < 0.05) in Cows assigned to synchronization treatments (53.3%; 37.2%) than in Control Cows (35.3%; 21.4%). In the beginning of the BS, non-suckled primiparous Cows treated with CIDR + PGF with estrous cycles having been initiated following calving had greater estrous detection and pregnancy rates than PGF and Control Cows, and suckled primiparous Cows had improved estrous detection and pregnancy rates when eCG was associated with CIDR + PGF + TW.

M F Smith - One of the best experts on this subject based on the ideXlab platform.

  • use of bovine pregnancy associated glycoproteins to predict late embryonic mortality in postpartum nelore Beef Cows
    Theriogenology, 2016
    Co-Authors: K G Pohler, R F G Peres, Jonathan A Green, H B Graff, T Martins, Jose Luiz Moraes Vasconcelos, M F Smith
    Abstract:

    Abstract The primary objective was to determine if circulating concentration of bovine pregnancy-associated glycoproteins (bPAGs) on Day 30 after artificial insemination (AI) may serve as a marker of late embryonic mortality in Bos indicus (Nelore) Beef Cows. In experiment 1, postpartum Nelore Beef Cows (n = 56) were artificially inseminated at a fixed time (Day 0) after synchronization of ovulation. Serum samples were collected on Days 0, 21, 24, 27, and 30 after AI. The first significant increase (P

  • preovulatory estradiol and the establishment and maintenance of pregnancy in suckled Beef Cows
    Journal of Animal Science, 2013
    Co-Authors: E M Jinks, K G Pohler, M F Smith, G. A. Perry, M D Macneil, J A Atkins, A J Roberts, R C Waterman, L J Alexander, T. W. Geary
    Abstract:

    In postpartum Beef Cows, GnRH-induced ovulation of small dominant follicles decreased pregnan- cy rates and increased late embryonic/fetal mortality. In Exp. 1, single ovulation reciprocal embryo transfer (ET) was used to examine the relationship between preovula- tory serum concentrations of estradiol at GnRH-induced ovulation in donor and recipient Cows and establishment and maintenance of pregnancy. Suckled Beef Cows (n = 1,164) were administered GnRH (GnRH1, 100 μg) on d -9 (GnRH1), PGF 2α on d -2, and GnRH2 (GnRH2, 100 μg) on d 0 (CO-Synch protocol) either with (donors; n = 810) or without (recipients; n = 354) AI. Single embryos (n = 394) or oocytes (n = 45) were recovered from the donor Cows (d 7; ET) and all live embryos were trans- ferred into recipients. Serum concentration of estradiol at GnRH2 was positively correlated with follicle size at GnRH2 (r = 0.45, P < 0.01) and progesterone at ET (r =0.34, P < 0.01). Donor Cows with greater estradiol at GnRH2 were more likely to yield an embryo than an unfertilized oocyte (P < 0.01). Donor and recipient Cows were retrospectively divided into 4 groups (low estradiol (<8.4 pg/mL) or high estradiol (≥8.4 pg/mL)) based on serum concentration of estradiol at GnRH2. Pregnancy rate at d 27 for low-low (n = 78), low-high (n = 80), high-low (n = 91), and high-high (n = 101) groups (donor-recipient, respectively) was 45, 65, 43, and 61% respectively (P < 0.02). Because recipient Cows with greater estradiol concentration at GnRH2 had greater pregnancy rates in Exp. 1, the objective of Exp. 2 was to evaluate the effect of estradiol supplementation on pregnancy rate. Ovulation was synchronized in suckled Beef Cows (n = 600) using the CO-Synch protocol with the insertion of a controlled internal drug release (CIDR; intravaginal progesterone supplement) from d -9 until d -2. Approximately one-half of the Cows (n = 297) received an injection of estradiol cypionate (ECP; 0.5 mg intramuscularly) 24 h before AI. Compared with the no treatment (Control) Cows, ECP treatment increased (P < 0.01) pregnancy rates of Cows induced to ovulate smaller dominant follicles (<12.2 mm). In conclusion, GnRH-induced ovulation of small dominant follicles was associated with reduced serum estradiol, fertiliza- tion rate (donor Cows), and pregnancy establishment (recipient Cows). Furthermore, ECP supplementation during the preovulatory period increased pregnancy rates in Cows induced to ovulate smaller dominant follicles.

  • effect of ovulatory follicle size and expression of estrus on progesterone secretion in Beef Cows
    Journal of Animal Science, 2008
    Co-Authors: D C Busch, T. W. Geary, J A Atkins, J F Bader, D J Schafer, David J Patterson, M F Smith
    Abstract:

    Induced ovulation of small dominant follicles (SF, 12 mm). Experiment 1 characterized P4 concentrations from ovulation to subsequent estrus among GnRH-in- duced or spontaneously ovulated SF (≤ 11 mm) or LF (≥ 12 mm) to determine if P4 secretion by CL formed from GnRH-induced SF remains lower postovulation in nonlactating Beef Cows. Nonlactating Beef Cows were induced to ovulate 48 h after PGF2α (CO-Synch; GnRH on d −9, PGF2α on d −2, and GnRH on d 0) or exhibited estrus and spontaneously ovulated after PGF2α. Follicle size was measured at the second GnRH in Cows induced to ovulate or ∼3 h after the onset of estrus for Cows that ovulated spontaneously. Cows were classified into 1 of 4 groups: 1) GnRH-induced ovulation-SF (≤ 11 mm; Ind- SF; n = 9); 2) GnRH-induced ovulation-LF (≥ 12 mm; Ind-LF; n = 16); 3) spontaneous ovulation-SF (≤ 11 mm; Spon-SF; n = 8); 4) spontaneous ovulation-LF (≥ 12 mm; Spon-LF; n = 22). Serum concentrations of P4 from d 3 to 15 were reduced in the Ind-SF compared with the Ind-LF (P = 0.05), Spon-SF (P = 0.07), and Spon-

  • ability of intravaginal progesterone inserts and melengestrol acetate to induce estrous cycles in postpartum Beef Cows
    Journal of Animal Science, 2004
    Co-Authors: M F Smith, George Perry, T. W. Geary
    Abstract:

    Postpartum anestrous interval in Beef Cows is a major factor contributing to reproductive failure during a defined breeding season. Our objectives were to determine the ability of a controlled internal drug-releasing device (CIDR, 1.9 g of progesterone), a normal dose of melengestrol acetate (MGA, 0.5 mg x cow(-1) x d(-1)), or a high dose of MGA (4.0 mg x cow(-1) x d(-1)) to induce ovulation and to eliminate short estrous cycles. Multiparous Beef Cows (n = 100) were equally assigned to one of four treatments: CIDR, normal MGA, high MGA, or control by age, days postpartum, body condition, and body weight. All Cows were fed carrier (0.9072 kg x cow(-1) x d(-1)) with (normal MGA, 0.55 mg/kg; high MGA, 4.41 mg/kg) or without MGA for 7 d (d -6 to 0). On d -6, CIDR were inserted and then removed on d 0. Estrous behavior was monitored continuously from d -6 until 29 using HeatWatch electronic mount detectors. Blood was collected on d -13, and three times weekly from d -6 to 29. Treatment influenced (P = 0.03) the percentage of Cows that were detected in standing estrus. Beginning on d 2, more CIDR-treated Cows had exhibited standing estrus compared with high MGA-treated or control Cows, but CIDR- and normal MGA-treated Cows did not differ. The percentage of CIDR-treated Cows that had ovulated was greater (P 1 ng/mL for > or = 10 d) was greater (P < 0.01) in CIDR-treated Cows (14.0 +/- 0.8 d; 20/20, 100%) compared with normal MGA-treated (6.2 +/- 1.0 d; 3/13, 23%), high MGA-treated (9.6 +/- 1.0 d; 8/14, 57%), or control Cows (6.1 +/- 0.9 d; 4/17, 24%), and greater (P < 0.03) in high MGA-treated Cows than in normal MGA-treated or control Cows. In the present study, treatment of early postpartum suckled Beef Cows with CIDR induced ovulation and initiated estrous cycles with a normal luteal life span in more Cows than did treatment with MGA. Treatment with MGA (normal or high dose) did not induce ovulation earlier than in control Cows, but a high dose of MGA increased the percentage of Cows with normal luteal life spans following the first ovulation postpartum.

  • Methods to Synchronize Estrous Cycles of Postpartum Beef Cows with Melengestrol Acetate12
    The Professional Animal Scientist, 2003
    Co-Authors: D.j. Patterson, F. N. Kojima, M F Smith
    Abstract:

    Abstract This review considers recently developed methods to control estrous cycles of postpartum Beef Cows with melengestrol acetate ( MGA ®, Pharmacia Animal Health, Kalamazoo, MI). Melengestrol acetate is an orally active progestin that will suppress estrus and prevent ovulation in cattle if consumed on a daily basis. The duration of feeding may vary among the various protocols that are available, but the level of feeding (0.5 mg/d per animal) is consistent and critical to success. Feeding MGA® for 14 d followed by injection of prostaglandin F 2α  ( PGF 2α ) 17 to 19 d after MGA® withdrawal was developed as an effective method of estrous cycle control for heifers. Studies in postpartum Beef Cows identified significant improvements in specific reproductive endpoints among Cows that received MGA® prior to the administration of PGF 2α  compared with Cows that received PGF 2α  only, including increased estrous response and improved synchronized conception (CR) and pregnancy (PR) rates. Recently, an improvement in synchrony of estrus was reported, without compromising fertility, in postpartum Beef Cows that were pretreated, either short- or long-term, with MGA® prior to gonadotropin-releasing hormone (GnRH) and PGF 2α . We proposed the general hypothesis that progestin (MGA®) treatment prior to the GnRH-PGF 2α  estrus synchronization protocol would successfully 1) induce ovulation in anestrous postpartum Beef Cows; 2) reduce the incidence of a short luteal phase among anestrous Cows induced to ovulate; 3) increase estrous response, synchronized CR, and PR; and 4) increase the likelihood of successful fixedtime insemination. Protocols that utilize this sequential approach to control the estrous cycle include the MGA® Select and 7-11 Synch protocols. The flexibility in matching specific protocols with the particular management system involved is a major advantage in using MGA® to control estrous cycles in Cows.