Manipulation of ovarian and uterine function to increase conception rates in cattle

In cattle, embryonic and fetal losses are the major causes of reproductive failure. Losses associated with failure in the process of maternal recognition of pregnancy can amount to as much as 30%. Successful estabblishment of pregnancy depends on a delicate balance between luteolytic mechanisms inherent to the endometrium at the end of diestrus and antiluteolytic mechanisms, orchestrated by the conceptus to change endometrial function and ultimately, block luteolysis. Antiluteolytic strategies are pharmacological, mechanical, nutritional and management manipulations of the process of maternal recognition of pregnancy that aim to increase the probability of succssful gestations. Objective of the present paper is to review the recent literature on antiluteolytic strategies in cattle. Specifically, we focused on strategies to simulate production of progesterone, strategies to reduce production of estradiol and other strategies. Future directions for research in this area are propose

Effect of eCG or estradiol benzoate associated with norgestomet on the conception rate of beef cows submitted to FTAI in the postpartum

Este estudo objetivou comparar as taxas de concepção, em vacas de corte no período pós-parto (PPP), tratadas com Gonadotrofina Coriônica Eqüina (eCG) ou Benzoato de Estradiol (BE), após o uso de Norgestomet submetidas à inseminação artificial em tempo fixo (IATF). A hipótese é que a administração de eCG ou BE aumenta as taxas de concepção. Vacas Nelore (n=138) e Brangus (n=63), lactantes, entre 26 e 118 dias do PPP, foram divididas em três grupos homogêneos e dentro de cada grupo subdivididas em dois blocos, um com um PPP < 45 dias (PPP1; n=107) e outro > 45 dias (PPP2; n=94). Todas as fêmeas receberam um implante auricular contendo 3mg de Norgestomet (Crestar®), seguido pela administração de 5mg de Valerato de Estradiol. Os implantes auriculares foram mantidos durante 10 dias. Na retirada dos implantes, as fêmeas receberam 1mL de solução fisiológica (n=68; Grupo Controle) ou 500UI de eCG (Folligon®; n=67; Grupo eCG) ou 1mg de Benzoato de Estradiol (Index; n=66; Grupo BE) 24 horas após a retirada do implante. A IATF foi realizada 54 horas após a retirada do implante. O diagnóstico de gestação foi realizado por ultra-sonografia 30 dias após a IATF. Houve interação entre os tratamentos e o PPP. No PPP1, a taxa de concepção foi maior no grupo eCG comparado ao BE (47,22% vs. 15,38%; P<0,01). No PPP2, as taxas de concepção dos grupos eCG e BE foram maiores que no grupo controle (41,93%, 44,44% vs. 22,22%; P<0,01). Conclui-se que vacas, com até 45 dias do PPP, o eCG associado ao Norgestomet aumenta as taxas de concepçãoThis study aimed to compare conception rates at the postpartum period (PPP) in beef cows which were administered either Equine Chorionic Gonadotrophin (eCG) or Estradiol Benzoate (EB) after Norgestomet and submitted to fixed-time artificial insemination (FTAI). The hypothesis was that the administration of eCG or EB enhances the conception rate. Lactating Nelore cows (n=138) and Brangus (n = 63), between 26 and 118 days of post partum period (PPP) were divided into three homogeneous groups, and subdivided in two blocks, inside each group one of them with a PPP = 45 days (PPP1; n=107) and another with a PPP > 45 days (PPP2; n=94). All cows received an auricular implant containing 3mg Norgestomet (Crestar®), followed by the administration of 5mg Estradiol Valerate. The auricular implants were kept during 10 days. Cows received 1mL saline solution (n=68, Control Group) or 500IU eCG (Folligon®; n=67; eCG Group) or 1mg Estradiol Benzoate (Index, n=66; EB Group) 24 hours after the removal of the implant. FTAI was made 54 hours after the implant removal. The pregnancy diagnosis was carried through ultrasonography 30 days after FTAI. There was an interaction between treatments and PPP. In the PPP1, the conception rate was higher in the eCG Group than in the EB Group (47.22% vs. 15.38%; P=0.01). In the PPP2, the conception rates of the eCG and EB Groups were higher than in the Control Group (41.93%, 44.44% vs. 22.22%: P=0.01). It was concluded that in cows up to 45 days of PPP, the eCG associated with Norgestomet enhances the conception rate

Effects of ethanol on synthesis of prostaglandin F2α in bovine females

Ethanol stimulates the production of prostaglandins in many species. The purpose of this study was to verify the effect of ethanol on the production of prostaglandin F2α (PGF2α) and luteolysis in bovine females. In the first experiment, Holstein cows at day 17 of the oestrous cycle were treated with 100% ethanol (0.05 ml/kg of body weight, IV; n = 5), saline (0.05 ml/kg of body weight, IV; n = 4) or synthetic prostaglandin (150 μg of D-cloprostenol/cow, IM; n = 4). The plasma concentrations of 13, 14-dihydro-15-keto PGF2α (PGFM; the main metabolite of PGF2α measured in the peripheral blood) were assessed by radioimmunoassay (RIA). There was an acute release of PGFM in response to ethanol comparing to other treatments (p ≤ 0.05). However, only cows treated with PGF2α underwent luteolysis. In the second experiment, endometrial explants of cross-bred beef cows (n = 4) slaughtered at day 17 of the oestrous cycle were cultured for 4 h. During the last 3 h, the explants were cultured with medium supplemented with 0, 0.1, 1, 10 or 100 μl of 100% ethanol/ml. Medium samples were collected at hours 1 and 4 and concentrations of PGF2α were measured by RIA. Ethanol did not induce PGF2α production by the endometrium. In conclusion, ethanol does not cause luteolysis in cows because it stimulates production of PGF2α in extra-endometrial tissue

Quantification of interferon-tau during the maternal recognition of pregnancy in Bos taurus indicus cows

Durante o período crítico do reconhecimento materno, compreendido entre o 15° e 19° dias da gestação, o concepto deve sintetizar competentemente moléculas capazes de bloquear a síntese de prostaglandina F2a (pGF2a) e a luteólise. Em bovinos, a principal macromolécula protéica envolvida em tal bloqueio é o interferon-tau (IFN-r). Durante o período crítico, falhas neste reconhecimento determinam à mortalidade embrionária em até 40% das fêmeas inseminadas. Informações sobre o IFN-r em animais Bos taurus indicus, ainda são restritas. Este estudo objetivou uma avaliação quantitativa do IFN-r durante o período crítico do reconhecimento materno, em lavados uterinos obtidos por sonda de Foley (dias 14, 16 e 18 pósestro) oupost-mortem (dia 18 pós-estro). Para tanto, foram utilizadas fêmeas multíparas azebuadas (Bos taurus indicus), cíclicas ou prenhes, nos dias 14, 16 e 18 pós-estro. Para a obtenção dos lavados, os úteros foram infundidos com solução de Ringer Simples. Os lavados foram concentrados por ultra-f1ltração e liofilizados. As macromoléculas protéicas foram separadas por Eletroforese Unidimensional SDSPAGE, em gel com 15% de poliacrilamida. A quantificação do IFN-r nos lavados uterinos foi realizada por Western-Blotting e densitometria. Tanto nos lavados obtidos por sonda de Foley quanto nos post-mortem foi possível observar bandas de proteínas que apresentaram reação cruzada com os anticorpos utilizados no WesternBlotting. O IFN-T foi detectado apenas nos lavados uterinos post-mortem de vacas prenhes (P<0,05). A densidade óptica não foi afetada pelo dia do período crítico, estado (cíclico ou prenhe) ou interação dia x estado. Nos lavados post-mortem não houve efeito de peso do concepto ou concentração de progesterona plasmática no dia do lavado na densidade da banda protéica referente ao IFN-T . Concluiu-se que a detecção e quantificação do IFN-T no ambiente uterino de vacas azebuadas, nestas condições ) condições experimentais, é possível apenas em lavados uterinos obtidos post-mortemDuring the critical period of the maternal recognition, which occurs between days 15 and 19 of pregnancy, the conceptus must competendy synthesize molecules capable of blocking the synthesis of prostaglandin F2a (pGF2a) and luteolysis. In canle, the major macromolecule involved in suck blockage is the protein interferontau (IFN-i). During the critical period, failures in the recognition of pregnancy determine embryonic mortality on up to 40% of inseminated cows. Data about IFN-i in Bos taurus indicus are still scarce. Objective of this studywas to quantitatively evaluate the presence of IFN-i during the critical period for maternal recognition of pregnancy in uterine flushings obtained in vivo by Foley catheter (Days 14, 16 and 18 post estrus) or post-mortem (Day 18 post estrus). Multiparous, cyclic or pregnant zebu cows (Bos taurus indicus) on days 14,16 and 18 post estrus were used for in vivo or post mortem uterine flushing collection. In both cases, a Ringer solution was used to wash the uterus of cows. Uterine flushings were concentrated by ultra@tration and lyophilized. Prateins were separated by one-dimensional electrophoresis (SDS-PAGE) in a 15% polyacrilamide geL Interferontau quantification in uterine flushings was performed by western blotting and densitometry. Non-specific protein bands were observed in both in vivo and post mortem uterine flushings. Interferon-tau was detected only in uterine flushings obtained fram pregnant cows post-mortem (p<0.05). Optical density of protein bands was not affected by the day of the critical period, state (cyclic ar pregnant) or interaction day x state. There was no effect of the conceptus weight or progesterone concentration on the day of uterine flushing collection in the optical density of the IFN-i pratein bando It was concluded that the detection and quantification of IFN-i in the uterine environment of zebu cows, in these experimental? conditions, is only possible in uterine flushings obtained post-mortemFAPES