Orientador: Flavia Thomaz Verechia Pereira / Banca: Cristiana Andrighetto / Banca: Vanessa Gomes Ueno / Resumo: A utilização da transgenia com a proteína fluorescente verde (GFP) como marcador de células de origem fetal nas placentas de clones bovinos servirá de modelo inédito para estudo morfofisiológico e imunológico da interação materno-fetal, visto que possibilitará o seu mapeamento, diferenciando as células fetais das maternas. Tal modelo terá aplicação direta, principalmente porque estes são animais que apresentam problemas em relação ao seu desenvolvimento. Com o auxílio deste modelo, pretende- se verificar o transporte de substâncias entre a mãe e o feto via endocitose, pela imunolocalização das proteínas chamadas de caveolinas. Para tanto foram utilizados 06 bovinos clonados e 30 bovinos de inseminação artificial (IA) com idade até 90 dias de gestação, os quais tiveram seu desenvolvimento interrompido mediante abate humanitário das receptoras e ovariosalpingohisterectomia, com posterior recuperação do útero gestante. Foram coletados os placentônios e o cório. Uma parte das amostras foi recortada e fixada, por imersão, em solução de parafolmaldeído a 4% ou formoldeído a 10% em tampão fosfato de sódio (PBS) a 0,1M pH 7.4, solução de Zamboni (4% de paraformoldeído, 15% de ácido pícrico, em tampão fosfato de sódio a 0,1M pH 7.4), metacarn (60% de metanol, 30% de clorofórmio, e 10% de ácido acético glacial), para verificação da morfologia e realização de imuno-histoquímica para as proteínas caveolinas -1 e -2 (CAV -1 e CAV-2). As caveolinas -1 foram localizadas nos vilos fetais e maternos, mas sua marcação mais forte foi observada no estroma endometrial. As caveolinas -2 tiveram marcação positiva no trofoblasto e membrana corioalantoide, e, especificamente em célula trofoblástica gigante binucleada. Sendo assim, os resultados mostram que a proteína CAV-1 teve uma maior expressão em relação a proteína CAV-2 e que as proteínas CAV-1 e -2 são parte da composição das cavéolas, sendo . / Abstract: The transgenic application of green fluorecent protein (GFP) as fetal cell marker on cattle cloned placenta could provide an exclusive model for studying the morphologic and immunologic maternal-fetal interactions, providing information about its mapping, distinguishing the fetal from maternal cells. This model will have direct application, mainly because these are animals that present problems during its development. With this model's support, we intend to verify the substances transport between mother and fetus during endocytocis, through the immunolocalization of protein named caveolae. For these, we used 06 cloned bovine and 30 cattle samples of artificial insemination (AI) with 90 days of pregnancy, which had been their development interrupted by humanitarian slaughter of the recipient and recovery of the pregnant uterus. We collected the placentome and the chorion. A part of the samples will be cutted and fixed, by immersion, on a solution containing 4% of parafomaldehyde or 10% of formaldehyde on a sodium phosphate buffer (PBS) at 0,1M pH 7.4, Zamboni solution (4% of paraformaldehyde, 15% of picric acid, on sodium phosphate buffer 0,1M pH 7.4), metacarn (60% of metanol, 30% of chloroform, and 10% glacial acetic acid), for morphologic and immunohistochemistry verification for caveolinas proteins -1 and -2 ( -1 CAV and CAV- 2). The caveolinas -1 were found in fetal and maternal villi , but its strongest staining was observed in the endometrial stroma . The caveolinas -2 had positive staining in trophoblast and chorioallantoic membrane , and specifically in giant trophoblastic binucleated cell . therefore the results were compared between cloned cattle and from AI or natural mating, for assisting on detection of the reason of many placental alterations, embryonic losses, spontaneous abortion, post-natal mortality and large offspring syndrome on laboratory-manipulated animals. The result suggests that the proteins caveolins -1 and ... / Mestre

Orientador: José Luiz Moraes Vasconcelos / Banca: João Carlos Pinheiro Ferreira / Banca: Mario Binelli / Resumo: O presente estudo avaliou se a concentração de P4 durante o desenvolvimento do folículo ovulatório em protocolo a base de P4/BE e com uma aplicação de GnRH em seu início interfere na prenhez à IATF em vacas Holandesas em lactação. A hipótese é que vacas com maior P4 no dia da aplicação da 1ª dose de PGF2α terão maior fertilidade. Para alterar a P4 os animais (n=594) foram distribuídos aleatoriamente em dois grupos para receberem um ou dois dispositivos intravaginais de P4 (CIDR®, Zoetis, SP, Brasil). O protocolo utilizado foi: no d-11 inserção de 1 CIDR (novo ou previamente usado por 9 dias) + aplicação de 2mg i.m. de BE (Gonadiol®, Zoetis, SP, Brasil) + 100mcg i.m. de GnRH (Cystorelin®, Merial, SP, Brasil); d-4, aplicação de 25mg i.m. de Dinoprost (Lutalyse®, Zoetis, SP, Brasil); d-2, aplicação de 25mg i.m. de Dinoprost + 1mg i.m. de ECP (ECP®, Zoetis, SP, Brasil) + retirada do dispositivo de P4; d0, IATF. Os animais do grupo 2CIDR receberam um CIDR adicional no d-11, o qual foi retirado no d-4. Nos d-11 (n= 117), d-4 (n= 351), d0 (n= 214) e d10 (n= 72) foram colhidas amostras de sangue para determinação da concentração de P4. A P/IA foi determinada através de US nos d32 (DG1) e d60 (DG2). Dados binários foram analisados pelo PROC GLIMMIX, e os dados contínuos pelo PROC MIXED do SAS (foi considerada diferença significativa se P<0,05 e tendência se P<0,1). A P4 não diferiu entre os tratamentos no d-11 (1CIDR= 4,2±0,4 ng/ml; 2CIDR= 4,5± 0,4ng/ml; P>0,1), e no d-4 (1CIDR= 3,5±0,2ng/ml; 2CIDR= 3,8±0,2 ng/ml; P>0,1), porém foi detectada interação entre tratamento e presença de CL no início do protocolo na P4 no d-4 (sem presença de CL e 1CIDR= 2,7±0,3ng/ml; 2CIDR= 3,6±0,3ng/ml, com presença de CL e 1CIDR= 4,3±0,3ng/ml; 2CIDR= 4,0±0,3ng/ml; P<0,05). Não houve diferença na prenhez a IATF e nas perdas gestacionais entre os tratamentos [DG1: 1CIDR= 20,0 ... / Abstract: The present study evaluated if P4 concentration during ovulatory follicle development in a timed artificial insemination (TAI) protocol based on P4/E2 affects pregnancy per AI in lactating Holstein cows. Our hypothesis is that cows that present higher P4 concentration at PGF2α administration have also higher fertility. To alter P4, animals (n=594) were randomly assigned to receive one or two intravaginals devices of P4 (CIDR®, Zoetis, SP, Brazil). TAI protocol utilized was: d-11 intravaginal device of P4 (new or previously used by 9 days) + 2mg im EB (Gonadiol®, Zoetis, SP, Brazil) + 100mcg im GnRH (Cystorelin®, Merial, SP, Brazil); d-4, 25mg im Dinoprost (Lutalyse®, Zoetis, SP, Brazil); d-2, 25mg im Dinoprost + 1mg im ECP (ECP®, Zoetis, SP, Brazil) + CIDR removal; d0, TAI. Animals in the group 2CIDR received an adicional CIDR at d-11, which was removed at d-4. At d-11 (n=117), d-4 (n=351), d0 (n=214) and d10 (n=72), blood samples were taken from cows for P4 concentration measurements. Pregnancy per AI was determined by ultrasound at d32 (DG1) and d60 (DG2). The binomial data were analyzed using PROC GLIMMIX and continuous data using PROC MIXED of SAS. An effect was considered significant when P<0.05 and tendency when P<0.1. P4 did not differ among treatments at d-11 (1CIDR=4.2±0.4ng/ml; 2CIDR=4.5±0.4ng/ml; P>0.1), and at d-4 (1CIDR=3.5±0.2ng/ml; 2CIDR=3.8±0.2 ng/ml; P>0.1). An interaction was detected between treatment and CL presence at the beginning of TAI protocol in P4 at d-4 (without CL and 1CIDR=2.7±0.3ng/ml; 2CIDR= 3.6±0.3ng/ml, with CL and 1CIDR=4.3±0.3ng/ml; 2CIDR= 4.0±0.3ng/ml; P<0.05). There was no difference among treatments in pregnancy per AI and pregnancy loss between DG1 and DG2 [DG1: 1CIDR= 20,0% (81/310) vs. 2CIDR= 15,7% (65/284); DG2: 1CIDR= 18,2% (74/310) vs. 2CIDR= 13,8% (57/283); Pregnancy loss: 1CIDR= 14,1% (7/81) vs. 2CIDR= 11,5% (7/64); P>0,1]. 37,0% (28/63)... / Mestre

Orientador: Wilter Ricardo Russiano Vicente / Banca: Ana Paula Coelho Ribeiro / Banca: Maria Isabel de Mello Martins / Banca: Maria Denise Lopes / Banca: Paulo Henrique Franceschini / Resumo: O objetivo deste estudo foi avaliar a taxa de concepção em cadelas após inseminação artificial intrauterina por videolaparoscopia. Um total de 20 cadelas foram inseminadas, sendo 10 com sêmen fresco e 10 com sêmen congelado. Os animais se encontravam em estro natural e sob acompanhamento da citologia vaginal. Quando aproximadamente 90% das células se apresentaram cornificadas, foram realizadas dosagens séricas de progesterona afim de se determinar o momento exato da inseminação. Três machos foram utilizados como doadores de sêmen e as coletas foram realizadas por manipulação digital. Após coleta o ejaculados foram analisados quanto ao volume, motilidade, vigor e concentração espermática. Para a inseminações utilizando sêmen fresco, a coleta foi realizada momentos antes do procedimento, e o sêmen acondicionados em banho-maria a 37°C até o momento da inseminação. Amostras destinadas a inseminação com sêmen descongelado, obtiveram mesmo processo de análises após coleta, seguindo para o processo de congelação, permanecendo congeladas por no mínimo uma semana, e então descongeladas momentos antes do procedimento. De acordo com os concentrações séricas de progesterona, as inseminações intrauterinas por videolaparoscopia foram realizadas, sendo cada corno uterino inseminado com 1mL de sêmen, em concentração de 250x106 espermatozóides/mL nas cadelas inseminadas com sêmen fresco e 80x106 espermatozóides/mL naquelas inseminadas com sêmen congelado. Após 7 dias as cadelas foram ováriosalpingohisterectomizadas, sendo o lúmen das tubas e cornos uterinos lavados com solução de PBS. Embriões foram encontrados nos lavados de 7 cadelas inseminadas com sêmen fresco, e em 5 inseminadas com sêmen descongelado. Concluiu-se que o procedimento de inseminação artificial intrauterina... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The objective of this study was to evaluate the fertility in bitches after intrauterine artificial insemination by videolaparoscopy. A total of 20 bitches were inseminated, being 10 with fresh semen and 10 with frozen. The animals were in natural oestrus, and their vaginal cytology was followed. When approximately 90% of the cells were cornificated, evaluation of serum levels of progesterone was performed, with the objective to determinate the exact moment of the artificial insemination. Three males were used as donors, and the samples collection was performed by digital manipulation. After collection the ejaculates were analysed considering volume, motility, vigor and sperm concentration. For the inseminations using fresh semen the collection was performed minutes before the process, and the semen sample was maintained at 37°C. Samples destined to inseminations using frozen semen were submitted to the same analysis process after collection, followed by the freezing process, being frozen during a minimum period of one week, and thawing moments before the procedure. According to the serum levels of progesterone, the intrauterine inseminations by videolaparoscopy were performed, being each uterine corn inseminated with 1 mL of semen, with 250x106 espermatozoa/mL in bitches with fresh semen and 80x106 espermatozoa/mL in bitches with frozen semen. After 7 days the bitches were ovariohysterectomized, and the lumen of the uterine tube and corns were flushed with PBS solution. Embryos were found in 7 bitches inseminated with fresh semen, and in 5 inseminated with frozen semen. It was concluded that the intrauterine artificial insemination by videolaparoscopy seems to be an interesting reproductive biotechnology method, especially in what refers to the use of frozen semen. / Doutor

Orientador: Cezinande de Meira / Banca: João Carlos Pinheiro Ferreira / Banca: Cássia Maria Barroso Orlandi / Resumo: Estudos recentes têm demonstrado diferentes respostas do CL quando da administração de prostaglandina F2α em diferentes doses e momentos. O objetivo deste trabalho foi avaliar o efeito do tratamento com baixas doses de PGF2α sobre características funcionais e estruturais de CLs em fases distintas do diestro em éguas. As éguas foram distribuídas aleatoriamente em 8 grupos: D2-NaCL (n=6; 2 mL de solução de NaCl à 0,9%); D2-Pgf (n=9; 10 mg de Dinoprost Trometamina); D2-1/10Pgf (n=6; 1 mg de Dinoprost Trometamina); D2-1/20Pgf (n=6; 0,5 mg de Dinoprost Trometamina); D8-NaCl (n=7; 2 mL de solução de NaCl à 0,9%); D8-Pgf (n=6; 10 mg de Dinoprost Trometamina); D8-1/10Pgf (n=7; 1mg Dinoprost Trometamina); D8-1/20Pgf (n=7; 0,5 mg de Dinoprost Trometamina). A área total do CL (AT), a perfusão sanguínea objetiva (PVO) e subjetiva (PVS) do CL e as concentrações plasmáticas de progesterona (P4) foram avaliados a cada 6 horas durante 48 horas (H0 = momento imediatamente antes do tratamento). A AT não sofreu interferência da dose de PGF2α independente do dia de tratamento. A P4 apresentou uma correlação positiva com a PVO e PVS, sendo esta última mais sensível na detecção das alterações de P4. O tratamento no D2 não foi capaz de induzir a luteólise completa em nenhuma égua enquanto que o tratamento no D8 promoveu luteólise completa em todas as éguas do grupo controle positivo e parcial e completa em algumas éguas dos grupos D8-1/10Pgf e D8-1/20Pgf. Resposta dose-dependente da PGF2α foi observada, ou seja, quanto menor a dose aplicada menor as quedas em PVS e P4. Conclui-se que a resposta do CL ao tratamento com diferentes doses de PGF2α depende da fase de desenvolvimento do CL / Abstract: Recent studies have demonstrated different response of the CL to different doses of prostaglandin F2α on differente moments. The present experiment aims to evaluate the effect of treatments with PGF2α low doses over functional e structural characteristics of the CLs at two distintic stages. Mares were randomly assigned into groups: D2-NaCL (n=6; 2 mL of saline solution); D2-Pgf (n=9; 10 mg of Dinoprost Tromethamine); D2-1/10Pgf (n=6; 1 mg of Dinoprost Tromethamine); D2-1/20Pgf (n=6; 0,5 mg of Dinoprost Tromethamine); D8-NaCl (n=7; 2 mL of saline solution; D8-Pgf (n=6; 10 mg of Dinoprost Tromethamine); D8-1/10Pgf (n=7; 1mg of Dinoprost Tromethamine); D8-1/20Pgf (n=7; 0,5 mg of Dinoprost Tromethamine). Total area (AT), objective (PVO) and subjective (PVS) vascular perfusion of the CL and plasmatic progesterone (P4) were evaluated every six hours for 48h after treatment (H0 = immediately before treatment). PGF2α did not influenced on AT or day of treatment. P4 showed a positive correlation to PVO and PVS, and PVS was strongly correlated to P4. Treatment on D2 was not able to induce total luteolysis in any mare while treatment on D8 promoted total luteolysis in all mares in group D8-Pgf and 29% and 14% of the mares for the groups D8-1/10Pgf and D8-1/20Pgf, respectively. Parical luteolysis were also detected in groups on D8. The response to PGF2α seems to be dose-dependent, the decrease in PGF2α dose proportionally decreases PVS and P4. It is concluded that CL response to treatment with different doses of PGF2α depends os the CL developmental stage / Mestre

Orientador: Maria Denise Lopes / Banca: Frederico Ozanan Papa / Banca: Gilson Hélio Toniollo / Banca: Isabel Candia Nunes da Cunha / Banca: Fabiana Ferreira de Souza / Resumo: A inseminação artificial (IA) utilizando sêmen congelado é uma ferramenta importante na reprodução de cães, visa o melhoramento genético e melhor aproveitamento do reprodutor. Além disso, a melhor metodologia para avaliar o potencial fecundante de uma amostra de sêmen é o teste in vivo. Por isso, os objetivos deste trabalho foram determinar a taxa de gestação de cadelas, utilizando sêmen congelado em meio diluente TRIS/OEP/Frutose/8%Glicerol, e comparar duas técnicas de IA: intra-uterina, por laparotomia e intravaginal. O sêmen foi colhido de um único macho, por manipulação digital do pênis e analisado, imediatamente, após a colheita e após a descongelação a 70°C, por 8 segundos. A cinética do movimento foi verificada pelo CASA (Computer Assisted Semen Analyzer), e a integridade das membranas por: sondas fluorescentes (iodeto de propídio e carboxifluoresceína), pelo teste supra vital com a coloração de eosina, e pela associação de sondas (iodeto de propídio, JC-1 e FITC-PSA). A morfologia espermática foi avaliada por meio de esfregaços corados com Karras. A congelação do sêmen foi realizada pelo método descrito por Chirinéa et al. (2006). As fêmeas foram monitoradas desde o início da fase do proestro utilizando a citologia vaginal seriada e a dosagem de progesterona sérica, a cada 48 horas. Para as inseminações, as cadelas foram divididas em dois grupos: Grupo 1 (n=6) inseminadas uma única vez, via intra-uterina, por laparotomia, com uma dose inseminante de 160 x 106 espermatozóides/2mL; e Grupo 2 (n=6) inseminadas duas vezes, via intravaginal com uma dose inseminante de 160 x 106 espermatozóides/2 mL por inseminação. Os resultados das análises do sêmen pré e pós-descongelação não apresentaram diferenças significativas, com exceção da morfologia espermática e da associação de sondas fluorescentes... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Artificial insemination (AI) using frozen semen is an important tool on dog's reproduction, aiming to genetic improvement and better use of a stud. Besides, the better way to evaluate the fecundate potential of a semen sample is an in vivo test. That way, the aim of this work was to determine the pregnancy rate in bitches, using TRIS/OEP/Fructose/8%Glycerol as the diluent medium, and to compare two AI techniques: intrauterine and intravaginal. Semen was collected from one male only, by digital manipulation. Semen was analyzed immediately after collection and after thawed at 70°C for 8 seconds. Movement kinetics were analyzed by CASA (Computer Assisted Semen Analyzer), membrane integrity using fluorescents probes (propidium iodide and carboxyfluorescein), supravital test, eosin staining, integrity of plasmatic, nuclear and mitochondrial membranes using the association of fluorescent probes (FITC-PSA, propidium iodide and JC-1) and sperm morphology. Semen was frozen using the method described by Chirinéa, 2006. Females were monitored since the beginning of proestrus, using vaginal smear and progesterone measurement, each 48hours. To inseminations, bitches were divided into two groups: Group 1, composed by 6 females, which were inseminated just once via intrauterine, with an insemination dose of 160 x 106 spermatozoids/2mL and Group 2 constituted by 6 females, which were inseminated twice, via intravaginal, using an insemination dose of 160 x 106 spermatozoids/2 mL/insemination. Results from semen analyses made before and after freezing did not show any difference, except for sperm morphology and association of fluorescents probes. Pregnancy rate was 66,6% (4/6) on Group 1 and 16,6% (1/6) on Group 2. In conclusion, the success of artificial insemination depends not only on semen quality after thawed, but also on the AI technique used. In our work, intrauterine technique by laparotomy was better than intravaginal. / Doutor

MSCAGR (Animal Science) / Department of Animal Science / The aims of the study were to evaluate the effects of dilution and chilled storage time on the quality of semen, and of different artificial insemination techniques on fertility in artificially inseminated indigenous Venda does. Fresh semen was collected using an artificial vagina from three Boer bucks aged 4±1.55 years once every four days during July and August 2016. Semen was pooled and samples were divided into two equal parts, which were extended using Biladyl® extender at ratios of 1:5 and 1:10 v/v (semen to extender), before refrigeration for 120 hours at 5 °C. The fresh undiluted semen and freshly extended semen were evaluated in six replicates for sperm motility, live-dead and sperm morphology using the Sperm Class Analyzer (SCA). Extended semen continued to be evaluated at 24 hour intervals for 120 hours. Ninety indigenous Venda does were obtained from different flocks in the Vhembe district and kept intensively in one 10 m x 40 m pen at the University of Venda experimental farm in the goat feedlot. The does were fed and watered ad libitum. After acclimatization for 14 days, estrus was synchronized using a controlled internal drug release (CIDR) containing 0.3 g of progesterone. Upon removal of the CIDR, does were injected 10 mg of PGF2α (Lutalyse® dinoprost tromethamine) Sterile Solution. At 24 hours after the removal of the CIDR, the does were injected intramuscularly with 300 international units (IU) of equine chorionic gonadotrophin (eCG). Forty eight hours after the removal of the progesterone, freshly collected and diluted (1:5 ratio ~150x106 sperm/ml), five day-stored semen were used to inseminate the does using cervical (CAI), trans-cervical (TAI), and laparoscopic artificial (LAI) insemination methods in a complete randomized design (CRD) with a 2 X 3 factorial arrangement of the treatments with 15 replications per treatment. The does were tested for pregnancy after 30 days using ultrasonography. Analyses of variance was performed on the pregnancy, kidding rates and on prolificacy using the GLM procedure of Minitab (Minitab 2013). Significant differences in all motility parameters were observed between the extension ratios and storage time (P<0.01). There were significant interactions between the extension ratio and storage time (P<0.05) on the sub-population of sperm cells with non-progressive motility (NON-P). Significant (P<0.01) interaction was observed between the semen extension ratio and storage time on medium and slow spermatozoa (P<0.01). The method of insemination did not (P>0.05) affect fertility, though both pregnancy and kidding rates numerically decreased in the order laparoscopic insemination (LAI)≥ trans-cervical insemination (TAI)≥ cervical insemination (CAI). Overall, 71% kidding rate was achieved.

OBJECTIVE: To evaluate the effectiveness of offering double intrauterine insemination (IUI) to clients in our fertility program. STUDY DESIGN: In this prospective, nonrandomized study, 595 couples with ovulatory dysfunction, endometriosis, male factor, unexplained, tubal factor and combined diagnoses utilizing clomiphene citrate-hCG (CC-hCG), CC-gonadotropin-hCG (CC-Gn-hCG), Gn-hCG, lupron-Gn-hCG (L-Gn-hCG) or luteinizing hormone (LH) surge monitoring of natural cycles were offered single or double IUI in a total of 1,276 cycles. Single IUIs were performed at 36 hours following hCG or the day following LH surge; double IUIs were performed 18 and 36 hours following hCG or the day of and day following LH surge. Single versus double IUI clinical pregnancy outcomes were compared between ovarian stimulation protocols and diagnostic categories. RESULTS: One hundred ten clinical pregnancies occurred for 508 couples in 999 single IUI cycles (fecundity, 11.0%); 45 clinical pregnancies for 174 couples occurred in 277 double IUI cycles (16.2%, p < 0.004). The single IUI group was younger than the double IUI group (32.8 vs 33.7, p < 0.004). Differences for fecundity were noted regarding diagnostic categories between single and double IUI groups (ovulation dysfunction, 12.9% vs 19.5%, p < 0.048, and male factor, 7.9% vs 17.5%, p < 0.030) and ovulation protocols (CC-Gn-hCG, 13.0% vs 21.3%, p < 0.031, and L-Gn-hCG, 4.2% vs 25.0%, p < 0.002). CONCLUSION: Double IUI is superior to single IUI overall, especially when comparing Gn-containing ovarian stimulation protocols or within the ovulatory dysfunction and malefactor diagnostic categories.

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Estrus detection programs practiced on most U.S. dairy farms are not intense enough to provide the information needed to accurately time insemination, thus preventing AI from obtaining its full conception rate potential. Herds (n = 17) participated in a trial designed to evaluate percent pregnant relative to various characteristics of estrus. Herds utilized HeatWatch® electronic estrus detection system to detect and record mounting activity for cows in estrus. Inseminations were performed daily during a three hour interval for all cows identified in estrus the previous 24 h. Model characterizing percent pregnant for cows (services = 2661) included effects of interval from first mount to AI (P < 0.01), mounts per estrus (P < 0.01), DIM at insemination (P < 0.01), herd (P <0.05), and season of AI (P < 0.05). As mounts per estrus and days in milk increased, percent diagnosed pregnant increased. Interval affected probability of pregnancy with highest odds ratios for percent pregnant occurring >4 to 16 h following onset of estrus. Model for heifers (n = 306) included linear effects of interval (P < 0.01), season (P < 0.05), and herd (P < 0.01). In dairy heifers, as interval from first mount to AI increased, percent pregnant decreased. Timing of insemination in dairy cows can now be performed relative to first mount of estrus, with highest probability of pregnancy occurring between >4 to 16 h after onset. If onset of estrus is not known, insemination should be performed at the next most convenient time within 3 h. / Master of Science