Sincronização de cio de vacas mertolengas e inseminação artificial a tempo fixo com sémen de touro brahman

O maior rendimento num efectivo de bovinos de carne são os vitelos. O cruzamento de Bos indicus com Bos taurus tem vindo a ser praticado em vários Países como os EUA e o Brasil. A descendência daqui resultante mostra vantagens em relação às raças puras, desde a sua criação, que exige poucos custos, até ao maior lucro proveniente da sua venda. Assim, torna-se interessante explorar esta prática em Portugal onde o custo de produção é significativamente mais alto. A fim de evitar perdas de tempo na detecção de cio e permitir a aplicação de Inseminação Artificial a Tempo Fixo, hoje em dia são frequentemente utilizados protocolos de sincronização de cio e ovulação. Este trabalho teve como objectivo avaliar a influência da gonadotrofina coriónica equina, associada a uma progesterona e prostaglandina na sincronização do estro e da ovulação, sobre a taxa de sincronização e fertilização em vacas de carne Mertolengas (Bos taurus) IATF com sémen de touro de Brahman (Bos indicus). Foram seleccionadas 20 vacas Mertolengas cíclicas e com uma condição corporal entre 2 e 3,5 (escala de 1 a 5, Houghton et al., 1990). No dia 0 foi implantado a todos os animais um implante intravaginal de progesterona (CIDR®; 1,9g; Pfizer). No dia 8 administrou-se prostanglandina F2α (Dinolytic®; 5ml; IM; Pfizer). No dia 9 foi aplicada Gonadotrofina Coriónica (Intergonan® 6000UI; IM; Intervet) e o CIDR® (Pfizer) foi retirado. No dia 11 de tratamento, em horário pré-estabelecido, 48horas após a injecção de eCG foi realizada inseminaçao artificial de todos os animais com sémen de touro Brahman. A sincronização de cio neste estudo teve uma taxa de sucesso de 90% (18/20) e uma taxa de concepção de 40% (8/20). Com o cruzamento destas duas raças é esperado criar uma descendência capaz de produzir vitelos de boa qualidade e com o menor custo possível.

Comparison of three protocols for superovulation of brown brocket deer (Mazama gouazoubira)

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Função ovariana de novilhas Nelore alimentadas com dieta suplementada com gordura protegida ruminal

O objetivo deste trabalho foi avaliar o efeito da suplementação alimentar com gordura protegida ruminal sobre as estruturas ovarianas e sobre a concentração sérica de progesterona, em novilhas Nelore mantidas em pasto. Quarenta novilhas foram divididas em dois grupos: um suplementado com gordura protegida Megalac-E (G); e outro sem suplementação de gordura (C). O grupos foram avaliados em delineamento crossover. Utilizaram-se dietas isoenergéticas e isoproteicas. Após 15 dias de suplementação, os animais foram submetidos a um protocolo hormonal, para avaliação da influência da suplementação com gordura no metabolismo da progesterona. Para isto, em um dia aleatório do ciclo (D0), inseriu-se um implante intravaginal de liberação de progesterona (CIDR), e aplicou-se prostaglandina F2α (PGF2α, i.m.). No D7, o implante foi retirado, e outra aplicaηão de PGF2α foi realizada. No D18, foi feita uma nova aplicaηão de PGF2α e, então, foram observados diariamente os exames ultrassonográficos ovarianos e a ocorrência de estro. Para o ensaio com progesterona, colheu-se sangue 4 dias após a inserção do implante e, novamente, 7 e 14 dias após a ovulação. A concentração de progesterona sérica no D4 foi maior no grupo G. Não houve diferença nas concentrações séricas de progesterona 7 e 14 dias após a ovulação, nem no diâmetro do folículo ovulatório, nem no volume luteal. A suplementação com Megalac-E altera o metabolismo de progesterona, mas não altera a função ovariana em novilhas zebuínas em pasto.

Mês de parição, condição corporal e resposta ao protocolo de inseminação artificial em tempo fixo em vacas de corte primíparas

No experimento I, foi avaliada a alteração da condição corporal (CC) pré e pós-parto em 155 novilhas inseminadas para parir de setembro a dezembro. A CC foi avaliada mensalmente no pré e pós-parto, de junho a fevereiro. No experimento II, 538 vacas primíparas foram sincronizadas com o protocolo de inseminação artificial em tempo fixo (IATF) que usou estradiol junto ao dispositivo intravaginal de progesterona (CIDR®). As taxas de ciclicidade, sincronização e concepção foram avaliadas por ultra-som. No experimento I, os animais que pariram primeiro tiveram maior (P<0,001) redução na CC pós-parto. No experimento II, foi observado maior CC (P<0,0001) nos animais com menor número de dias pós-parto, maior (P<0,05) taxa de sincronização nas vacas de melhor CC e aumento (P<0,0001) na taxa de concepção proporcional ao aumento na CC (incremento médio na concepção de seis pontos percentuais para cada 0,25 ponto na CC). Não se deve antecipar a parição de novilhas de corte quando se pretende realizar IATF no início da estação de monta subseqüente.

Strategies to improve fertility in Bos indicus postpubertal heifers and nonlactating cows submitted to fixed-time artificial insemination

Two experiments were designed to evaluate strategies to increase fertility of Bos indicus postpubertal heifers and nonlactating cows submitted to a fixed-time artificial insemination (TAI) protocol consisting of an intravaginal device containing 1.9 g of progesterone (CIDR) insertion + estradiol benzoate on Day 0, CIDR withdrawal + estradiol cypionate on Day 9, and TAI on Day 11. In Experiment 1, heifers (n = 1153) received a new or an 18-d previously used CIDR and, on Day 9, prostaglandin F(2 alpha) (PGF(2 alpha)) + 0, 200, or 300 IU equine chorionic gonadotropin (eCG). Heifers treated with a new CIDR had greater (least squares means +/- SEM) serum concentration of progesterone on Day 9 (3.06 +/- 0.09 ng/mL vs. 2.53 +/- 0.09 ng/mL; P < 0.05) and a smaller follicle at TAI (11.61 +/- 0.11 nim vs. 12.05 +/- 0.12 mm; P < 0.05). Heifers with smaller follicles at TAI had lesser serum progesterone, concentrations on Day 18 and reduced rates of ovulation, conception, and pregnancy (P < 0.05). Treatment with eCG improved (P < 0.05) follicle diameter at TAI (11.50 +/- 0.10 mm, 11.90 +/- 0.11 mm, and 12.00 +/- 0.10 mm, for 0, 100, and 200 IU, respectively), serum progesterone concentration on Day 18 (2.77 +/- 0.11 ng/mL, 3.81 +/- 0.11 ng/mL, and 4.87 +/- 0.11 ng/mL), and rates of ovulation (83.8%, 88.5%, and 94.3%) and pregnancy (41.3%, 47.0%, and 46.7%). In Experiment 2, nonlactating Nelore cows (n = 702) received PGF(2 alpha) treatment on Days 7 or 9 and, on Day 9, 0 or 300 IU cCG. Cows receiving PGF(2 alpha) on Day 7 had lesser serum progesterone concentrations on Day 9 (3.05 +/- 0.21 ng/mL vs. 4.58 +/- 0.21 ng/mL; P < 0.05), a larger follicle at TAI (11.54 +/- 0.21 mm vs. 10.84 +/- 0.21 mm; P < 0.05), and improved (P < 0.05) rates of ovulation (85.4% vs. 77.0%), conception (60.9% vs. 47.2%), and pregnancy (52.0% vs. 36.4%). Treatment with eCG improved (P < 0.05) serum progesterone concentration on Day 18 (3.24 +/- 0.14 ng/mL vs. 4.55 +/- 0.14 ng/mL) and the rates of ovulation (72.4% vs. 90.0%) and pregnancy (37.5% vs. 50.8%). In conclusion, giving PGF(2 alpha) earlier in the protocol in nonlactating cows and eCG treatment in postpubertal heifers and nonlactating cows improved fertility in response to a TAI (progesterone + estradiol) protocol. (C) 2009 Elsevier B.V. All rights reserved.

Reproductive performance of prepubertal Bos indicus heifers after progesterone-based treatments

The objective was to evaluate the effects of exogenous progesterone (P4) on reproductive performance of prepubertal Bos indicus heifers. Prepubertal Nelore heifers (n = 589; 24.0 +/- 1.13 mo; 298.0 +/- 1.89 kg; body condition score of 3.2 +/- 0.26; mean +/- SEM) were randomly assigned to receive, between experimental Days -12 and 0: no treatments (CIDR0; n = 113); a new intravaginal insert (CIDR) containing 1.9 g of P4 (CIDR1; n = 237); or a similar insert previously used three times, with each use occurring for 9 d (CIDR4; n = 239). An additional treatment group was pubertal heifers given 12.5 mg dinoprost tromethamine im on Day 0 (PGF; n = 346), and used as controls for evaluation of conception rates. on Day 0, transrectal palpation was done for uterine score evaluation (UtS; 1-3 scale), blood samples were taken for serum P4 concentrations, and follicle diameter (FD) was measured. The breeding season started on Day 1 and consisted of AI after detection of estrus between Days I and 45, and exposure to bulls between Days 46 and 90. There were effects of treatment (P < 0.05) on serum concentrations of P4 on Day 0 (0.37 +/- 0.16, 2.31 +/- 0.11, and 1.20 +/- 0.11 ng/mL for CIDR0, CIDR1, and CIDR4, respectively; mean SEM), FD on Day 0(9.45 +/- 0.24, 9.72 +/- 0.17, and 11.42 +/- 0.16 mm), UtS on Day 0 (1.49 +/- 0.06, 1.88 +/- 0.04, and 2.24 +/- 0.04), estrus detection rates at 7 d (19.5, 42.6, and 38.3%) and 45 d (52.2, 72.1, and 75.3%) of the breeding season, and on pregnancy rates at 7 d (5.3, 14.3, and 18.4%), 45 d (27.4, 39.2, and 47.7%) and 90 d (72.6, 83.5, and 83.7%) of the breeding season. Conception rate 7 d after the start of the breeding season was greater (P < 0.05) in heifers from the CIDR4 (46.8%) and PGF (43.8%) groups than in the CIDR0 (27.3%) and CIDR1 (33.7%) groups. In conclusion, exogenous P4 hastened puberty and improved pregnancy rates at the beginning of the breeding season in prepubertal Bos indicus heifers. Furthermore, previously used CIDR inserts were better than new inserts. (C) 2010 Elsevier B.V. All rights reserved.

Progesterone-based estrous synchronization protocols in non-suckled and suckled primiparous Bos indicus beef cows

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(2 alpha) (PGF), or CIDR (6 d)+prostaglandin F(2 alpha) (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(2 alpha)+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+IW+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. (C) 2009 Elsevier B.V. All rights reserved.

Progesterone concentrations, exogenous equine chorionic gonadotropin, and timing of prostaglandin F-2 alpha treatment affect fertility in postpuberal Nelore heifers

Two experiments were performed to test the hypothesis that elevated progesterone concentrations impair pregnancy rate to timed artificial insemination (TAI) in postpuberal Nelore heifers. In Experiment 1, postpuberal Nelore heifers (n = 398) received 2 mg estradiol benzoate (EB) and either a new progesterone-releasing intravaginal device containing 1.9 g of progesterone (CIDR) (first use) or a CIDR previously used for 9 d (second use) or for 18 d (third use) on Day 0, 12.5 mg prostaglandin F-2 alpha (PGF(2 alpha)) on Day 7, 0.5 mg estradiol cypionate (ECP) and CIDR withdrawal on Day 9, and TAI on Day 11. Largest ovarian follicle diameter was determined on Day 11. The third-use CIDR treatment increased largest ovarian follicle diameter and pregnancy rate. Conception to TAI was reduced in heifers with smaller follicles in the first- and second-use CIDR treatments, but not in the third-use CID treatment. In Experiment 2, postpuberal Nelore heifers received the synchronization treatment described in Experiment 1 or received 12.5 mg PGF2. on Day 9 rather than Day 7. In addition, 50% of heifers received 300 IU equine chorionic gonadotropin (eCG) on Day 9. Heifers were either TAI (Experiment 2a; n = 199) or Al after detection of estrus (Experiment 2b; n = 125 of 202). In Experiment 2a, treatment with cCG increased pregnancy rate to TAI in heifers that received PGF2. on Day 9 but not on Day 7 and in heifers that received a first-use CIDR but not in heifers that received a third-use CIDR. Treatments did not influence reproductive performance in Experiment 2b. In summary, pregnancy rate to TAI in postpuberal Nelore heifers was optimized when lower concentrations of cxogcnous progesterone were administered, and eCG treatment was beneficial in heifers expected to have greater progesterone concentrations. (C) 2009 Elsevier B.V. All rights reserved.

Fertility-associated antigen on Nelore bull sperm and reproductive outcomes following first-service fixed-time AT of Nelore cows and heifers

The objective was to determine whether the presence of fertility-associated antigen (FAA) on sperm collected from Nelore (Bos indicus) bulls can be used to assess potential fertility of sperm for use at first-service fixed-time AI (TAI). Six Nelore bulls were selected based on FAA status (FAA-negative: N = 3; FAA-positive: N = 3) and the ability to produce neat semen with >= 70% morphologically normal sperm and 60% estimated progressive motility before cryopmservation. In Experiment 1, suckled multiparous Nelore cows (N = 835) were evaluated for body condition score (BCS) and received an intravaginal progesterone device (CIDR) and 2.0 mg of estradiol benzoate (Day 0). on Day 9 the CIDR was removed, 12.5 mg of PGF(2 alpha) and 0.5 mg of estradiol cypionate were administered, and calves were removed for 48 h. All cows received TAI on Day II (48 h after CIDR removal). Pregnancy per TAI (P/TAI) was not different between FAA-positive and FAA-negative bulls (41.5% vs. 39.3%, respectively). There was an effect of AI technician on P/TAI (36.0% vs. 43.9%; P < 0.05) and BCS tended to affect P/TAI (P = 0.09), as cows with BCS >= 2.75 were 1.4 times more likely to become pregnant compared with cows with BCS < 2.75. In Experiment 2, nulliparous Nelore heifers (N = 617) were evaluated for BCS and received a CIDR and estradiol benzoate (2.0 mg) on Day 0. on Day 7, all heifers received PGF(2 alpha) (12.5 mg). on Day 9, CIDR inserts were removed and all heifers received estradiol cypionate (0.6 mg) and 200 IU eCG. All heifers received TAI on Day 11 (48 h after CIDR removal). Pregnancy/TAI was different (P = 0.04) between FAA-positive and FAA-negative bulls (33.7% vs. 40.7%, respectively). Presence of FAA on sperm was unsuccessful in assessing the potential fertility of sperm for use in TAI. (C) 2012 Elsevier B.V. All rights reserved.

Fixed-time artificial insemination with estradiol and progesterone for Bos indicus cows I: Basis for development of protocols

Five experiments were conducted on commercial farms in Brazil aiming to develop a fixed-time artificial insemination (TAI) protocol that achieved pregnancy rates between 40% and 55% in Bos indicus cows. These studies resulted in the development of the following protocol: insertion of all intravaginal device containing 1.9 g of progesterone (CIDR) plus 2.0 mg im estradiol benzoate on Day 0; 12.5 mg im dinoprost tromethamine on Day 7 in cycling cows or oil Day 9 in anestrous cows; CIDR withdrawal plus 0.5 mg im estradiol cypionate plus temporary calf removal on Day 9; TAI (48 h after CIDR withdrawal) plus reuniting of calves with their dams on Day 11. Reduced dose of prostaglandin F(2 alpha) (PGF(2 alpha): 12.5 mg im dinoprost tromethamine) effectively caused luteolysis. In cycling cows, fertility was greater when the treatment with PGF(2 alpha) was administered on Day 7 than oil Day 9, but in anestrous cows, no effects of time of the PGF(2 alpha) treatment were found. Estradiol cypionate effectively replaced estradiol benzoate or gonadotropin-releasing hormone as the ovulatory stimulus, reducing labor and cost. In this protocol, CIDR inserts were successfully used four times (9 d each use) with no detrimental effects on fertility. (C) 2009 Elsevier B.V. All rights reserved.

Comparison of progesterone-based protocols with gonadotropin-releasing hormone or estradiol benzoate for timed artificial insemination or embryo transfer in lactating dairy cows

The objective was to compare two protocols for synchronizing ovulation in lactating Holstein cows submitted to timed AI (TAI) or timed ET (TET). Within each farm (n = 8), cows (n = 883; mean +/- SEM 166.24 +/- 3.27 d postpartum, yielding 36.8 +/- 0.34 kg of milk/d) were randomly assigned to receive either: 1) an intravaginal progesterone insert (CIDR (R)) with 1.9 g of progesterone + GnRH on Day -10, CIDR (R) withdrawal + PGF2 alpha on Day -3, and 1 mg estradiol cypionate on Day -2 (treatment GP-P-E; n(TAI) = 180; n(TET) = 260); or 2) a CIDR (R) insert + 2 mg estradiol benzoate on Day -10, PGF2 alpha on Day -3, CIDR (R) withdrawal + 1 mg estradiol cypionate on Day -2 (treatment EP-P-E; n(TAI) = 174; n(TET) = 269). Cows were subsequently randomly assigned to receive either TAT on Day 0 or TET on Day 7. Serum progesterone concentration on Day -3 was greater in GP-P-E than in EP-P-E (2.89 +/- 0.15 vs 2.29 +/- 0.15 ng/mL; P < 0.01), with no significant effect of group on serum progesterone on Day 7. Compared to cows submitted to TAI, those submitted to TET had greater pregnancy rates on Day 28 (44.0% [233/5291 vs 29.7% [105/354]; p < 0.001) and on Day 60 (37.6% [199/529] vs 26.5 [94/354]; P < 0.001). However, there were no effects of treatments (GP-P-E vs EP-P-E; P > 0.10) on synchronization (87.0% [383/440] vs 85.3% [378/443]), conception (TAI: 35.3% [55/156] vs 33.8% [50/148]; TET: 50.7% [115/227] vs 51.3% [118/230]) and pregnancy rates on Days 28 (TAT: 30.5% [55/180] vs 28.7% 150/174]; TET: 44.2% [115/260] vs 43.9% [118/2691) and 60 (TAI: 27.2% [49/80] vs 25.9% [45/174]; TET: 38.8% [101/260] vs 36.4% [98/269]). In conclusion, GP-P-E increased serum progesterone concentrations on Day -3, but rates of synchronization, conception, and pregnancy were not significantly different between cows submitted to GP-P-E and EP-P-E protocols, regardless of whether they were inseminated or received an embryo. (c) 2011 Elsevier B.V. All rights reserved.

Effect of progesterone and/or estradiol treatments prior to induction of ovulation on subsequent luteal lifespan in anestrous Nelore cows

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Strategies to improve fertility in postpartum multiparous Bos indicus cows submitted to a fixed-time insemination protocol with gonadotropin-releasing hormone and prostaglandin F-2 alpha

In Exp. 1, we evaluated the effects of 2 lengths of progesterone exposure [CIDR (controlled intravaginal drug release); 7 vs. 14 d] before a modified CO-Synch protocol [50.0-mu g injection of GnRH 6.5 d before a 25.0-mg injection of PGF(2 alpha) followed by another injection of GnRH and fixed-time AI (TAI) 2 d after PGF(2 alpha)], with or without temporary weaning (TW) before GnRH treatments, on fertility of suckled multiparous Bos indicus cows (n = 283) and on calf performance. Timed AI pregnancy rates for cows receiving 7 d CIDR + TW, 7 d CIDR, 14 d CIDR + TW, and 14 d CIDR were 53, 47, 46, and 41%, respectively (P > 0.10). Calves submitted to two 48-h TW 6 d apart had decreased mean BW at 240 d (187.9 +/- 2.7 vs. 195.5 +/- 2.7 kg; P < 0.05), but BW at 420 d was not affected by TW (240.1 +/- 5.1 kg). In Exp. 2, we evaluated the effect of no treatment and treatment with or without a CIDR insert between GnRH and PGF(2 alpha) treatments of a modified CO-Synch protocol on pregnancy rate to TAI, and throughout a 90-d breeding season in suckled multiparous Bos indicus cows (n = 453). The inclusion of a CIDR between first GnRH and PGF(2 alpha) treatments of a modified CO-Synch protocol did not improve pregnancy rate (29 and 33% for cows receiving CO-Synch + CIDR and CO-Synch protocol, respectively), and cycling cows had poorer TAI pregnancy rates than anestrous cows treated with either synchronization protocol (21.7 vs. 40.7%; P < 0.05). However, regardless of treatment with CIDR, cows submitted to TAI protocol had greater (P < 0.05) pregnancy rates at 30 (54.8 vs. 11.2%), 60 (72.1 vs. 38.8%), and 90 d (82.0 vs. 57.9%) of breeding season than untreated cows.

Serum progesterone concentration and conception rate of beef cows supplemented with ground corn after a fixed-time artificial insemination protocol

Avaliaram-se os efeitos de diferentes níveis de ingestão de suplemento com milho moído finamente (MF) em vacas de corte, mantidas em pasto, após inseminação artificial em tempo fixo (IATF), sobre a concentração sérica de progesterona (P4) no dia 7, e sobre a concepção no dia 28 pós IATF. Trezentas e sessenta e quatro vacas Brangus, multíparas lactantes, tiveram as atividades folicular e luteal sincronizadas por tratamento com benzoato de estradiol (Estrogin; 2,0mg IM) e inserção de dispositivo intravaginal de P4 (CIDR) no dia -11, seguido por tratamento com PGF2 α (Lutalyse; 25mg IM) no dia - 4, retirada do CIDR e remoção temporária de bezerros no dia -2, e tratamento com GnRH (Fertagyl; 100 µ g IM), IATF e retorno dos bezerros no dia 0. No dia 0, as vacas foram aleatoriamente distribuídas para receber um dos quatro tratamentos: G1 -2kg/dia de MF do dia 0 ao dia 21; G2 -2kg/dia de MF do dia 0 ao dia 7, e 6kg/dia de MF do dia 8 ao dia 21; G3 -6kg/dia de MF do dia 0 ao dia 7, e 2kg/dia de MF do dia 8 ao dia 21; G4 -6kg/dia de MF do dia 0 ao dia 21. Amostras de sangue foram colhidas no dia 7, e o diagnóstico de gestação foi realizado por ultrassonografia no dia 28. As vacas suplementadas com 2kg/dia de MF apresentaram maior concentração sérica de P4 no dia 7 em relação às vacas suplementadas com 6kg/dia (1,58 vs. 1,28ng/mL; P<0,01, EPM=0,08). As vacas do G4 apresentaram maior taxa de concepção em relação às vacas do G1 (58,4 vs. 41,9%, respectivamente; P<0,05). O nível de consumo do suplemento energético após a IATF é negativamente associado às concentrações séricas de P4, porém positivamente associado à taxa de concepção em vacas de corte em pasto.

Efeitos da progesterona exógena sobre o desenvolvimento folicular em ovelhas

Avaliaram-se os efeitos da progesterona (P4) sobre o crescimento folicular e na endocrinologia reprodutiva em ovelhas Bergamácia. Quatorze ovelhas sincronizadas com prostaglandinas (PGF2alfa ) foram distribuídas em dois grupos (n=7/grupo): grupo-controle e grupo tratado com progesterona (CIDR) depois da ovulação (dia zero). Desde o dia anterior à aplicação de PG até o dia 10, realizaram-se monitoramentos ultra-sonográficos para estabelecer o crescimento folicular. Amostras de sangue foram colhidas para a determinação de P4 desde o dia anterior à aplicação de PG até o dia 10 depois da ovulação. Para o perfil dos pulsos de hormônio luteinizante (LH), as colheitas de sangue ocorreram em intervalos de 30 minutos por um período de oito horas, nos dias um e seis. As taxas de crescimento diferiram (P<0,001) entre os grupos, 0,91±0,15 e 0,70±0,16mm/dia para os grupos controle e tratado, respectivamente. Os dias do platô dos animais controle e tratados foram de 1,9±0,72 e 2,9±0,45 (P<0,05), respectivamente. As concentrações médias de progesterona (P<0,001) foram diferentes entre os tratamentos. A freqüência dos pulsos diferiu no primeiro dia do ciclo (P<0,01), com valores de 2,55±0,09 pulsos/8 horas no grupo-controle e de 1,49±0,11 pulsos/8 horas no grupo tratado. No sexto dia, o grupo-controle 2,20±0,09 pulsos/8 horas apresentou maior número de pulsos (P<0,05) que o grupo tratado, 1,22±0,11 pulsos/8 horas. Os efeitos inibitórios da progesterona exógena no diâmetro do folículo dominante foram mediados pela redução na freqüência dos pulsos de LH.