Orientador: Hélio Takachi Okuda / Banca: Sony Dimas Bicudo / Banca: Edson Guilherme Vieira / Resumo: A sincronização do estro e a interrupção temporária do aleitamento visam antecipar o restabelecimento da atividade ovariana pós-parto. Este estudo teve por objetivo avaliar o efeito de um protocolo da sincronização do estro associado à interrupção temporária do aleitamento durante o período pós-parto em fêmeas primíparas da Raça Nelore (Bos taurus indicus). O lote (80 animais) recebeu os seguintes tratamentos: T1 - Testemunha / Controle (20 animais), T2 - Interrupção temporária do aleitamento (20 animais), T3 - Protocolo de sincronização de estro - Crestar (20 animais), T4 - Associação dos tratamentos T2 e T3 (20 animais). Os dados coletados foram: data do parto, sexo do bezerro, data do estro, avaliação reprodutiva (corpos lúteos, folículos, condição corporal, involução uterina, animais em anestro), pesos, escores, dosagem de progesterona, data de inseminação, data do implante, data da retirada do implante, resultado do diagnóstico de gestação. O peso médio, o escore corporal médio e o ganho de peso médio em T3 e T4 foram respectivamente 332,85 Kg, 340,83 Kg, , 4,5 e 4,0 e 0,10 Kg/cab/dia. A manifestação do estro em T3 e T4 foi respectivamente 21,05% e 55,55%. O Intervalo Parto - 1º Estro em T3, diferiu significativamente (Duncan p<0,05) em relação aos outros tratamentos. A taxa de gestação em T3 e T4 foi de 15,78 %. A taxa de gestação das vacas primíparas foi baixa. / Abstract: The syncronization of estrous and temporary interruption of suckling aim restablishment of the post-partum ovarian activity. The objective of this study was to evaluate the effect of the syncronization protocol associated with the temporary interruption of suckling during post-calving period in Nelore Breed primiparous females (Bos taurus indicus). The lot (80 animals) received the following treatments: Treatment 1 - Control (20 animals), Treatment 2 - Temporary Interruption of Suckling (20 animals), Treatment 3 - Syncronization Protocols - Crestar (20 animals), Treatment 4 - Association of treatment T3 and T4 (20 animals). The collected data were: calving date, calf sex, estrous date, reproductive evaluation (corpus luteum, follicles, body score condition, uterine involution, anestrous animals), progesterone dose, insemination date, implant date, implant removing date, pregnancy rate. The mean body weigth, the mean body condition score and mean weigth gain in T3 and T4 respectively were 332,85 Kg and 340,83 Kg, 4,5 and 4,0 e 0,10 Kg/cab/day. The estrous rate in T3 and T4 respectively were 21,05% and 55,55%. The calving - first estrous period in T4 was significanthy different (Duncan p<0,05) in relation to the other treatments. The pregnancy rate in T3 and T4 were 15,78%. The pregnancy rate of primiparous cows were lower. / Mestre

Made available in DSpace on 2014-06-11T19:27:42Z (GMT). No. of bitstreams: 0 Previous issue date: 2006-04-24Bitstream added on 2014-06-13T20:36:09Z : No. of bitstreams: 1 meneghetti_m_me_botfmvz.pdf: 184024 bytes, checksum: b833a6860023243a1fd026c9cdb4eef2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / O objetivo deste estudo foi avaliar o efeito do mês de parição na condição corporal (CC) no início de estação de monta e na resposta a dois protocolos de inseminação artificial em tempo fixo (IATF) em vacas primíparas de corte. No experimento I (exp. I) foi avaliado a alteração da CC pré e pós-parto em 87 novilhas Nelore e 68 u sangue Red Angus, inseminadas para parir de Setembro a Dezembro. A CC foi avaliada mensalmente no pré e pós-parto de Junho a Fevereiro. No exp. II as 155 vacas do exp. I foram sincronizadas entre 29 e 129 dias pós-parto (DPP), com o protocolo: remoção dos bezerros (RB) por 48 h antes do primeiro GnRH (100 mcg, Fertagyl®, INTERVET) e foi inserido dispositivo intravaginal de progesterona (CIDR®, Pfizer, 1,9 g). Após 6,5 dias, foi feita nova RB por 46h; o CIDR® foi removido; e foi aplicado prostaglandina 2 (PGF2 ) (25 mg, Lutalyse®, Pfizer). Entre 42 e 46h após a PGF2 as vacas receberam nova aplicação de GnRH e foram inseminadas. No exp. III, 538 primíparas de duas fazendas (60 Nelore e 123 u sangue Red Angus na fazenda 1 e 355 Nelore na fazenda 2), entre 33 e 104 DPP foram sincronizadas com o protocolo: inserção do CIDR® junto à de Benzoato de Estradiol (2,0 mg, Estrogin®, Farmavet), No dia 7 foi aplicado PGF2 (12,5 mg, Lutalyse®, Pfizer). No dia 9 foi retirado o CIDR®, foi feita RB e aplicado 0,5 mg de Cipionato de Estradiol (E.C.P.®, Pfizer). A IATF foi realizada 46 a 52 h após a retirada do CIDR®. A taxa de sincronização foi avaliada (exceto na fazenda 2 do exp. III) por dois exames de ultra-som (Aloka SSD-500, 5,0 MHz) e determinada pela presença e ausência de folículo dominante na IATF e 48 h após. O diagnóstico de gestação foi feito por ultra-som 28 dias após a IATF. A análise estatística do exp. I foi feita no PROC MIXED e dos exp. II e III no PROC LOGISTIC do SAS... / The aim of this study was to evaluate the calving date effect on body condition score (BCS) at the beginning of breeding season and on the response to a two timed artificial insemination (TAI) protocols in first-calf beef heifers. In experiment I (exp. I) was evaluated the BCS change pre and post-partum. Eighty seven Nelore heifers and 68 u blood Red Angus were inseminated to calve from September to December. The BCS were monthly measured from June to February, during the pre and post-partum of these animals. In exp. II, the cows from exp. I were TAI when they were between 29 and 129 days post-partum (DPP) with the protocol: calf removal (CR) for 48 h before the first GnRH (100 mcg, Fertagyl®, INTERVET) and an insertion of an intravaginal progesterone device (1.9 g, CIDR®, Pfizer). After 6,5 days a new CR was performed, the CIDR® was removed and was injected prostaglandin F2? (PGF2?) (25 mg, Lutalyse®, Pfizer). Between 42 and 46 h after PGF2? was injected a new GnRH and cows were TAI. In exp. III, 538 primiparous cows from two herds (60 Nelore and 123 u blood Red Angus from farm 1 and 355 Nelore from farm 2), between 33 and 104 DPP were synchronized with the protocol: day 0, insertion of a CIDR® and a injection of 2.0 mg of estradiol benzoate (Estrogin®, Farmavet), on day 7 was injected PgF2? (12.5 mg, Lutalyse®, Pfizer), in the CIDR® withdraw (Day 9) was injected estradiol cipionate (0.5 mg, E.C.P.®, Pfizer) and a CR was done, the TAI was preformed 46 to 52 hours after the device withdraw. In the TAI moment and 48 hours later a ultrasound scan (Aloka SSD-500, 5.0 MHz) was performed to determine the ovulation rate (except in the farm 2 of exp. 3). The pregnancy diagnosis was made by ultrasound 28 days after the TAI. The statistic analysis in exp. I was performed with PROC MIXED and in exp.II and III with PROC LOGISTIC from SAS... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:28:24Z (GMT). No. of bitstreams: 0 Previous issue date: 2005-12Bitstream added on 2014-06-13T18:34:31Z : No. of bitstreams: 1 biluca_df_me_botfmvz.pdf: 232011 bytes, checksum: 5f66e2b253e27ff8acb7ace15eb4f40e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Universidade Estadual Paulista (UNESP) / O objetivo deste estudo foi avaliar o efeito da suplementação com monensina, em vacas nelore paridas a pasto, em anestro, nas concentrações plasmáticas de AGNE, IGF-1, no diâmetro de maior folículo e na capacidade de resposta desse folículo a um estímulo ovulatório hormonal (GnRH). Nesse estudo foram usadas 302 vacas (123 primíparas e 179 multíparas) que foram divididas em dois tratamentos, proporcionalmente, onde o lote controle recebeu apenas suplementação mineral e o lote tratado recebeu suplementação monensina (110mg/vaca/dia). Os tratamentos se iniciaram 30 dias pré-parto, onde avaliou-se o ECC pré-parto, até 90 dias pós-parto. Todas as vacas, em média aos 54 dias pós-parto, receberam um estímulo hormonal ovulatório (administração de 50 mcg de GnRH), foram avaliadas para o escore de condição corporal (escala de 1 a 5), colhido sangue para análise de IGF-1 e AGNE e foram avaliadas para o do diâmetro folicular através de ultra-sonografia (US). Após 7 dias nova US foi realizada para verificar a taxa de ovulação. As variáveis foram submetidas à análise de variância pelo GLM do SAS. O ECC pós-parto foi maior (p<0,01) em vacas tratadas com monensina (3,11) que vacas controle (3,00); além disso, vacas tratadas não perderam ECC no período periparto enquanto vacas controle perderam 0,19 pontos. Vacas suplementadas com monensina (883,9 mmol/l) tiveram concentração plasmática de AGNE menor (p<0,01) que vacas controle (1013,8 mmol/l), caracterizando, junto com a ECC, menor mobilização de reservas. Já a concentração plasmática de IGF-1 foi maior (p<0,01) nas vacas tratadas (118,5 ng/ml) que vacas controle (85,1 ng/ml). Primíparas (118,0 ng/ml) apresentaram IGF-1 maior (p<0,01) que multíparas (84,8 ng/ml). Vacas tratadas (10,07mm) apresentaram folículo maior que vacas controle (9,58mm) e multíparas (10,35mm) maior que primíparas (9,30mm)... / The objective of this trial was to evaluate the effects of monensin supplementation in suckled anestrous Nellore cows on IGF-1 and NEFA concentrations, follicular diameter and GnRH ovulatory response. In this trial were used 302 cows (123 primiparous and 179 multiparous) divided in two treatments. The control group received only mineral supplementation and the treated group received monensin supplementation (110 mg/cow/day). The treatments began 30 days prepartum to 90 days postpartum. All cows, at average of 54 days postpartum, received hormonal ovulatory stimulation (50 mcg GnRH), BCS were evaluated (1 to 5 scale), blood samples were collected to IGF-1 and NEFA analysis and follicular diameter was measured by ultrasound (US). Seven days later ovulation rate was evaluated. Cows that received monensin had higher postpartum BCS (3.11) and lost less BCS at peripartum than control cows (3.00). Treated cows had lower (P<0.01) NEFA plasmatic concentration (883.9 mmol/l) than control cows (101.8 mmo/l), which associated with BCS suggests less reserve mobilization. IGF-1 plasmatic concentration was higher in treated cows (11.5 ng/ml) than control cows (85.1 ng/ml). Primiparous (118.0 ng/ml) had higher IGF-1 than multiparous (84.8 ng/ml). Treated cows had higher follicular diameter (10.07mm) than control cows (9,58mm) and multiparous (10.35mm) higher than primiparous (9.30mm). The hormonal ovulatory stimulation (GnRH) response is follicle diameter dependent and treated cows had higher response (35.9%) than control cows (31.5%). Monensin supplementation is a good strategy to improve energy status due to decrease in BCS loss and reduction of NEFA concentration. Monensin supplementation also increased IGF-1 plasmatic concentration, follicular diameter and hormonal (GnRH) ovulatory response.

Made available in DSpace on 2014-06-11T19:29:39Z (GMT). No. of bitstreams: 0 Previous issue date: 2002-03-18Bitstream added on 2014-06-13T19:38:55Z : No. of bitstreams: 1 moraes_tt_me_ilha.pdf: 118193 bytes, checksum: 381cadf1263c24dace3cfe7601d90d6d (MD5) / A sincronização do estro e a interrupção temporária do aleitamento visam antecipar o restabelecimento da atividade ovariana pós-parto. Este estudo teve por objetivo avaliar o efeito de um protocolo da sincronização do estro associado à interrupção temporária do aleitamento durante o período pós-parto em fêmeas primíparas da Raça Nelore (Bos taurus indicus). O lote (80 animais) recebeu os seguintes tratamentos: T1 - Testemunha / Controle (20 animais), T2 - Interrupção temporária do aleitamento (20 animais), T3 - Protocolo de sincronização de estro - Crestar (20 animais), T4 – Associação dos tratamentos T2 e T3 (20 animais). Os dados coletados foram: data do parto, sexo do bezerro, data do estro, avaliação reprodutiva (corpos lúteos, folículos, condição corporal, involução uterina, animais em anestro), pesos, escores, dosagem de progesterona, data de inseminação, data do implante, data da retirada do implante, resultado do diagnóstico de gestação. O peso médio, o escore corporal médio e o ganho de peso médio em T3 e T4 foram respectivamente 332,85 Kg, 340,83 Kg, , 4,5 e 4,0 e 0,10 Kg/cab/dia. A manifestação do estro em T3 e T4 foi respectivamente 21,05% e 55,55%. O Intervalo Parto - 1º Estro em T3, diferiu significativamente (Duncan p<0,05) em relação aos outros tratamentos. A taxa de gestação em T3 e T4 foi de 15,78 %. A taxa de gestação das vacas primíparas foi baixa. / The syncronization of estrous and temporary interruption of suckling aim restablishment of the post-partum ovarian activity. The objective of this study was to evaluate the effect of the syncronization protocol associated with the temporary interruption of suckling during post-calving period in Nelore Breed primiparous females (Bos taurus indicus). The lot (80 animals) received the following treatments: Treatment 1 - Control (20 animals), Treatment 2 – Temporary Interruption of Suckling (20 animals), Treatment 3 – Syncronization Protocols - Crestar (20 animals), Treatment 4 - Association of treatment T3 and T4 (20 animals). The collected data were: calving date, calf sex, estrous date, reproductive evaluation (corpus luteum, follicles, body score condition, uterine involution, anestrous animals), progesterone dose, insemination date, implant date, implant removing date, pregnancy rate. The mean body weigth, the mean body condition score and mean weigth gain in T3 and T4 respectively were 332,85 Kg and 340,83 Kg, 4,5 and 4,0 e 0,10 Kg/cab/day. The estrous rate in T3 and T4 respectively were 21,05% and 55,55%. The calving - first estrous period in T4 was significanthy different (Duncan p<0,05) in relation to the other treatments. The pregnancy rate in T3 and T4 were 15,78%. The pregnancy rate of primiparous cows were lower.

The main aim of the diploma work is to evaluation the reproduction level and the milk performance level of the concrete herd of cattle Holstein breed. The evaluation took place in family farm of Vladimír Pešta. The farm manages 73 hectares of soil and keeps 40 cows with closed herd turnover. Collection of input data took place in the years 2004 - 2007. There were monitored basic indicators of milk performance, indicators of reproduction and the development of body condition score (BCS) during the lactation period. The increasing milk production of the groups with performance to 7000 kg, 7000 {--} 8000 kg and over 8000 kg of milk affected negatively indicators of reproduction and there were the statistically demonstrable differences between groups. The duration of service period (SP) of groups by performance was 154, 165 and 175 days. Order of lactation period had no effect on reproduction. The milk production was by 1st lactation period 6 909 kg, by 2nd lactation period 8 435 kg and by 3rd lactation period 7 894 kg. There was the higher milk production by the dairy cows, which were calved in spring and in autumn, and it was 7 822kg and 7 898 kg. The dairy cows, which were calved in winter and in summer, had the performance lower by 400 kg. There were reached the better reproduction results by the dairy cows calved in winter and in spring, SP 164 and 153 days. The dairy cows calved in summer and in autumn had SP 174 and 182 days. The differences between the groups by season of year were not statistically demonstrable, neither at reproduction nor at milk production. The size of body framework of cattle had no effect on the milk production. The average value of body condition score on the beginning of lactation period was 3.59 points. The value of BCS was decreasing until 6th month of lactation period on 2.43 points. In the next months the BCS was slowly improving. The values of BCS oscillated during different phases of lactation period in range of 2 points. In the days of gestation the value of BCS was 2.65 points. The rate of the milk component fat/protein was on the beginning of lactation period 1.75, until 4th month of lactation period decreased on 1.35 and in the next months the rate was oscillated between 1.3 and 1.4. The average age by first calving was 834 days (27.4 months). By increasing age by first calving the subsequent performance sloped down. But this relationship was not statistically demonstrable. The average tallness in the small of the back amounted by cows, which are calving for the first time, to 149.8 cm. The attained milk performance was satisfactory. The reproduction results were less favourableness. From recognized relationships we can draw conclusions, that on the production and reproduction of the monitored herd the breeding conditions, the nutrition, the health state and the herd management have an mainly influence. By improvement of these factors we can achieve the better reproduction results. The influences like the season of year or the body framework of cattle are not too important.

Mule deer are an important rangeland grazer, large prey species, and game animal for the state of Utah, so herd size is monitored and managed actively. A significant cause of population decline is poor overwintering survival, including from the lack of available forage during winter months. Mule deer energy storage is correlated with greater overwintering success, so physical estimates of energy storage including body condition score (BCS), rump fat (RF), and loin thickness (LT), can be used to track and predict a herd's health. Current methods of collecting deer information are costly, time consuming, and cause physical stress to deer, so here we sought to test if a microbiome analysis could be used to predict deer overwintering success. We analyzed nearly 1000 fecal samples collected from deer in Utah over a five-year period. We found that the microbiome composition of these samples shared characteristics with published reports of other reported ruminant species. Also, the location and time when the samples were collected significantly influenced mule deer microbiota composition and abundance. We found that there is a relationship between microbes and health measures (BCS, RF, LT), including some microbial abundances that could predict the health measures of mule deer several months ahead of time. There were also microbial groups whose abundances were significantly correlated with the latitude and elevation of the deer. Finally, a longitudinal analysis on a subset of sampled deer produced slightly different results than the broad analysis of all samples, including suggesting that some of the differences in microbiota composition with time may have been related more to sampling distinct deer at different time points, rather than that the deer microbiota composition changed with time. . These results suggest possible candidate microbial taxa for use in developing assays to replace current methods of measuring and tracking deer health.

No description available.

This dissertation documents efforts to evaluate metabolic variables and the fecal microbiome in adult horses fed grass hay. In the first study, eight Arabian geldings limit-fed an 18% vs. 12% non-structural carbohydrate (NSC) hays in a cross-over design during two 28-day periods were included to evaluate the influence of grass hay NSC on serum insulin and plasma glucose concentrations. Serum insulin concentrations was higher in geldings fed the 18% NSC hay; however, this difference was only detected on day 7 and none of the geldings developed hyperinsulinemia. Blood glucose concentrations did not differ between hay groups. The second and third studies were extensions of the first and were conducted to use denaturing gradient gel electrophoresis (DGGE) and real-time PCR in evaluating the effect of forage carbohydrates on equine fecal bacteria diversity and abundance, respectively. Fecal microbiomes were similar (80.5-87.9%) between geldings. The abundance of bacteria belonging to the Firmicutes phylum increased (p = 0.02) in the feces of geldings fed 12% NSC hay (mean 8.06 range [8.03-8.11] log10 copies/g feces) compared to the feces of the same geldings when fed the 18% NSC hay (7.97 [7.97-7.98] log₁₀ copies/g feces). The Firmicutes (43.7%), Verrucomicrobia (4.1%), Proteobacteria (3.8%), and Bacteroidetes (3.7%) phyla dominated the fecal microbiomes. This work was the first to report the presence of the Actinobacteria, Cyanobacteria, and TM7 phyla in the equine fecal or gut microbiome. There was a high abundance (38%) of unclassified bacterial sequences in the gelding fecal microbiome. In the fourth study, 5 overweight adult mixed-breed mares and 5 adult mixed-breed mares in moderate condition, limit-fed a grass hay, were used to evaluate the effect of body condition on diet digestibility, plasma and fecal volatile fatty acid (VFA) concentrations, and fecal bacterial abundance. Hay, fecal, and blood samples were taken daily for 4 days after a 10 day adaptation period. A difference in hay digestibility, fecal VFA concentration, or bacterial abundance was not detected between overweight mares and mares in moderate condition. Plasma acetate, a product of microbial fermentation of fiber, was higher in the overweight mare group. / Ph. D.

The aim of this diploma thesis is to evaluate the data about holstein dairy cow body condition at calving and to review its effect on ketones blood level and its relation to incidence of ketosis. The monitoring took place in a selected dairy farm from October 2017 to February 2019. Body condition of 280 cows was evaluated on the day of calving by assessing the body condition score (BCS) and later on 10 days in milk the blood level of B-hydroxybutyrate was measured. Furthermore, parity, body weight in calving day, body weight on 10 days in milk, content of milk fat and protein on 10 days in milk and milk yield on 10 days in milk were monitored. Average BCS of the herd was 3,7, the maximum measured BCS value was 5, the minimum was 2. Total incidence of ketosis on herd level was 21,07 % considering ketosis if BHB 1,0 mmol.l-1. 62,7 % of that was a subclinical form of ketosis while the remaining 37,3 % was the clinical form of ketosis. Correlation analysis of the relation between parity and level of BHB in blood showed positive correlation (r=0,15, p=0,00), when cows on higher lactation had higher level of blood BHB. Positive correlation between fat/protein ratio in milk and level of BHB in blood was evaluated by correlation analysis (r=0,31 , p=0,00). The BCS at calving and BHB level on 10 days in milk showed positive correlation (r=0,14 , p=0,02). As far as negative energy balance is taken into account, the positive correlation between BCS at calving and body weight loss was confirmed (r=0,17 , p=0,00). The fact that heavier cows and cows with higher BCS mobilise more body fat reserves was confirmed by positive correlation between the body weight at calving and the body weight loss (r=0,47, p=0,00) and between the body weight at calving and the fat/protein ratio in milk (r=0,27, p=0,00). Body weight at calving had provable positive impact on the milk yield (r=0,19, p=0,00).

A presente tese foi dividida em 5 Experimentos. Os objetivos do Experimento 1 foram avaliar a utilização da gonadotrofina coriônica equina (eCG) e/ou do cipionato de estradiol (ECP) na dinâmica folicular e taxa de concepção de vacas holandesas submetidas a inseminação em tempo fixo (IATF). No D0, todos os animais (n = 782) receberam 2 mg de benzoato de estradiol (BE) e um dispositivo intravaginal de progesterona (CIDR). Oito dias depois, o CIDR foi retirado e todos os animais receberam PGF2?. Simultaneamente, os animais foram divididos em 4 grupos: G1) eCG + ECP no Dia 8; G2) eCG no Dia 8 + GnRH após 48h; G3) ECP no Dia 8; G4) GnRH após 48h. Amostras de sangue e exames utlra-sonográficos foram realizados frequentemente em um subgrupo de animais (n = 96). As análises estatísticas de todos os experimentos foram efetuadas com o proc GLIMMIX e proc MIXED do SAS. O uso de eCG e o escore de condição corporal (ECC) dos animais afetaram as concentrações circulantes de progesterona no diestro. Os animais do G2 apresentaram maior taxa de concepção que os do G4 (33,8% vs. 28,9%). Além disso, para animais de menor ECC, ficou evidente o benefício da aplicação de eCG (G2 = 44,4% vs. G4 = 6,1%). No Experimento 2 (n = 26), o objetivo foi comparar o efeito da administração da eCG no dia da remoção do CIDR em animais de menor (2,0-2,5) ou maior (3,0-3,5) ECC. Foram avaliadas algumas características do corpo lúteo (CL) como o volume e histologia, assim como as concentrações plasmáticas de progesterona no diestro. Independentemente da condição corporal dos animais, a eCG aumentou o volume do CL e a concentração plasmática de progesterona no diestro. O ECC afetou negativamente o volume e concentração de progesterona sérica no diestro. Não foi encontrado diferença na proporção de células grandes/pequenas, assim como no fluxo sanguíneo no CL entre os grupos experimentais. No Experimento 3, foi comparado a taxa de concepção em vacas de leite de alta produção (n = 388) após o uso do protocolo G2 do Experimento 1 (Capítulo I), com ou sem adição de ECP no momento da retirada do CIDR (novo ou usado). Não foi verificado efeito da adição do tratamento com ECP e nem do tipo do dispostivo na taxa de concepção. No Experimento 4 (n = 199), apesar no aumento verificado no diâmetro folicular no grupo tratado com GnRH 56h (17,8 mm) comparado com GnRH 48h (16,5 mm); e do atraso no momento da ovulação após a retirada do CIDR (GnRH 56h = 75,3h; GnRH 48h = 79,8h) não foi constatado qualquer diferença na concepção ao se atrasar a aplicação do GnRH de 48h para 56h em vacas inseminadas 16h depois do GnRH. No Experimento 5 (n = 185), a taxa de concepção não diferiu em animais que receberam o GnRH 48h ou 56h (momento da IATF) após a retirada do CIDR, indicando a possibilidade do emprego de um protocolo com apenas 3 manejos em vacas de leite de alta produção. / The current thesys has been divided in 5 Experiments. Objectives of Experiment 1 were to evaluate the effects of equine chorionic gonadotropin (eCG) and/or estradiol cypionate (ECP) on follicular dymanics and conception rate in Holstein cows receiving fixed timed artificial insemination (TAI). On D0, all cows (n = 782) received 2 mg of estradiol benzoate (EB) and one intravaginal progesterone device (CIDR). Eight days later, CIDR was removed and all animals were treated with PGF2?. Simultaneously, animals were divided in 4 groups: G1) eCG + ECP on Day 8; G2) eCG on Day 8 + GnRH 48h later; G3) ECP on Day 8; G4) GnRH 48h later. Blood samples and ultrasound exams were frequently performed in a subset of the animals (n = 96). All the statistical analyses for all experiments were performed with proc GLIMMIX and proc MIXED of SAS. Equine chorionic gonadotropin (eCG) treatment and body condition score (BCS) affected circulating progesterone in the diestrus. Cows in G2 had greater conception rates than cows in G4 (33,8% vs. 28,9%). In addition, in cows with lower BCS, eCG seems to be even more affective (G2 = 44,4% vs. G4 = 6,1%). In Experiment 2 (n = 26), the objective was to compare the effect of eCG the day of CIDR removal in animals with lower (2,0-2,5) or higher (3,0-3,5) BCS. Some variables such as corpus luteum (CL) volume, histology and circulating progesterone concentration in the diestrus were evaluated. Regardless of the body condition of the animals, eCG increased CL volume and circulating progesterone concentration in the diestrus. BCS negatively affected CL volume and circulating progesterone. There were no differences in large/small CL cell ratio, as well as CL blood flow between experimental groups. In Experiment 3, it was compared conception rate in dairy cows (n = 388) after using the same protocol G2 from Experiment 1 (Chapter I), with or without an ECP treatment at the time of CIDR (new or used) removal. Both ECP treatment and type of CIDR did not significantly affected conception rates. In Experiment 4 (n = 199), despite the fact that follicular diameter was increased in group GnRH 56h (17,8 mm) compared with GnRH 48h (16,5 mm); and of the delayed time of ovulation after CIDR removal (GnRH 56h = 75,3h; GnRH 48h = 79,8h), there were no differences in conception rates after delaying the GnRH treatment from 48h to 56h in cows inseminated 16h after GnRH. In Experiment 5 (n = 185), conception rate did not differ in animals that received GnRH 48h or 56h (at the time of TAI) after CIDR removal, indicating the possibility of using a protocol with only 3 handlings in high producing dairy cows.