Estudo comparativo da composição protéica de explantes endometriais de fêmeas bovinas tratadas ou não com 17b-estradiol no 17º dia do ciclo estral

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Suplementação de gordura protegida na produção de progesterona, momento da luteólise e prenhez em vacas nelore

Pós-graduação em Zootecnia - FMVZ

Uso do ácido mefenâmico em receptoras de embriões equinos

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

Efeito da aspiração folicular sobre a concentração de progesterona plasmática em éguas cíclicas

Pós-graduação em Medicina Veterinária - FMVZ

Resgate da função luteal em bovinos após desafio com cloroprostenol sódico

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeito de tratamentos com progesterona e/ou estradiol na incidência de regressão prematura do corpo lúteo após a primeira ovulação em vacas nelore pós-parto

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

Características e cronologia do parto induzido com cloprostenol ou d-cloprostenol em associação a carbetocina em cabras saanen

Pós-graduação em Medicina Veterinária - FMVZ

Efeito do tratamento superovulatório com extrato de pituitária ou FSH purificado equino sobre a concentração plasmática de progesterona durante a luteólise induzida com dinoprost trometamina em éguas

Pós-graduação em Medicina Veterinária - FMVZ

Avaliação funcional de estruturas luteais formadas após aspiração folicular em éguas

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

Função luteal e luteólise em cadelas: aspectos morfo-funcionais

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

Resposta luteal à PGF2α (Dinoprost Trometamina) durante as fases de luteogênese e manutenção do corpo lúteo em éguas

Pós-graduação em Medicina Veterinária - FMVZ

Calcium potentiates the effect of estradiol on PGF2a production in the bovine endometrium

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

Prostaglandin treatment at the onset of norgestomet and estradiol-based synchronization protocols did not alter the ovarian follicular dynamics or pregnancy per timed artificial insemination in cyclic Bos indicus heifers

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

The physiology and impact on fertility of the period of proestrus in lactating dairy cows

In cattle, proestrus begins with the initiation of luteolysis and ends with initiation of estrus and the GnRH/LH surge. This period is marked by a dramatic decrease in circulating progesterone (P4) that reaches a nadir by about 36-48 h in cows undergoing natural or prostaglandin F2 alpha (PGF)-induced luteolysis. Inadequate luteolysis is a cause of reduced fertility particularly in timed AI programs with small elevations in circulating P4 reducing fertility. Increasing circulating estradiol (E2) during proestrus is dependent on presence, size, and function of the dominant follicle and this varies during natural proestrus, due to whether animals have two or three follicular waves, and during PGF-induced proestrus, according to stage of the follicular wave at time of PGF treatment. Inadequate circulating E2 can limit fertility and increase pregnancy loss in some specific circumstances such as in cows with low BCS and in cows during heat stress. Thus, studies to optimize the length of proestrus and the concentrations of E2 and P4 during proestrus could produce substantial improvements in fertility and reductions in pregnancy loss.

The role of proestrus on fertility and postovulatory uterine function in the cow

Modern protocols to synchronize ovulations for timed artificial insemination and timed embryo transfer that include manipulations in the proestrus period (i.e., between luteolysis and estrus) affect fertility in cattle. Specifically, stimulating pre-ovulatory follicle growth and exposure to estrogens after CL regression increase the proportion of cows pregnant and decrease late embryo mortality. Such effects may be due to both preovulatory actions of estrogens and post-ovulatory actions of progesterone, as concentrations of the later hormone may be changed in response to manipulations conducted during proestrus. In the first portion of this paper we describe strategies used recently to manipulate the proestrus period in protocols for synchronization of ovulation, and to present evidence of their effects on fertility. Manipulations of timing and prominence of sex steroids during the proestrus and early diestrus that affect fertility may act on targets such as the endometrium. This tissue expresses receptors for both estrogens and progesterone and these hormones change endometrial function to support conceptus growth and pregnancy maintenance. However, specific cellular and molecular mechanisms through which fertility is affected via manipulations of the proestrus are poorly understood. In the second portion of this paper we describe a well-defined animal model to study changes in endometrial function induced by manipulations conducted during the proestrus. Such manipulations induced endometrial changes on sex steroid receptors expression, cell proliferation, oxidative metabolism and eicosanoid synthesis in the uterus, but not on glucose transport to uterine lumen. In summary, evidence is accumulating to support a positive role of increasing duration and estrogen availability during the proestrus on fertility to synchronization protocols. Such positive effects may be through changes in endometrial function to stimulate conceptus growth and survival.