Eficiência do protocolo superestimulatório P36, associado à administração de eCG ou LH, em animais da raça Nelore

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Taxas de prenhez em vacas nelore, em pós-parto recente, tratadas com protocolos hormonais à base de progesterona associados ou não a remoção temporária de bezerros(RTB) e ou eCG

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Efeito de suplementação para matrizes brangus de primeira cria

Pós-graduação em Zootecnia - FMVZ

Efeito de protocolos de sincronização de ovulação na taxa de prenhez em vacas leiteiras mestiças mantidas a pasto no verão

Pós-graduação em Zootecnia - FMVZ

Taxas de ovulação e prenhez em novilhas nelore cíclicas após utilização de protocolos para insiminação artificila em tempo fixo (IATF), com diferentes concentrações de progesterona, associadas ou nao a aplicação de eCG

Pós-graduação em Medicina Veterinária - FMVZ

Eficiência do protocolo superestimulatório P-36, associado à administração de eCG ou LH, em animais da raça Nelore

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

Suplementação com monensina pré e pós-parto associada a estratégias de sincronização da ovulação em vacas Nelore

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

Avaliação da taxa de prenhez em novilhas tratadas com protocolo GnRH-PGF2'alfa' -Benzoato de Estradiol (GPE) e em vacas submetidas a tratamentos hormonais com progesterona associados ou não a remoção temporária de bezerros

Pós-graduação em Medicina Veterinária - FMVZ

Desempenho reprodutivo e produtivo de ovelhas deslanadas mantidas em regime de pasto e suplementadas

Pós-graduação em Medicina Veterinária - FCAV

Relationships between growth of the preovulatory follicle and gestation success in lactating dairy cows

This report summarizes three studies conducted with lactating dairy cows aiming to increase pregnancy rates to fixed time artificial insemination (TAI) protocols. Experiment 1 was designed to determine if changing the timing of PGF2 alpha treatment during an E2/P4-based program would affect fertility to TAI or fixed-time embryo transfer (TET). In experiment 2, pregnancy rates to AI were compared following synchronized ovulation using two protocols that have been developed to reduce the period between follicular wave emergence and TAI. The Ovsynch-type protocol utilizes GnRH to synchronize the follicular wave by inducing ovulation of a dominant follicle at the beginning of the protocol, and to synchronize ovulation at the end of the protocol allowing TAI. In contrast, E2/P4-based protocols utilize E2 products in the presence of P4 to induce atresia of antral follicles and synchronize emergence of a new follicular wave. At the end of E2/P4-based protocol another E2 treatment in the absence of P4 is used to induce LH release and synchronize ovulation and allow TAI. Experiment 3 was designed to determine whether increasing the length time interval with reduced circulating P4 (proestrus) would increase fertility in a TAI program that utilized E2 and P4 to synchronize ovulation of cycling, lactating dairy cows. The overall conclusions are that circulating concentrations of progesterone and estradiol prior to and circulating concentrations of progesterone following ovulation can affect fertility in cattle. In addition, small increases in P4 concentrations near the time of AI, due to lack of complete CL regression, result in reductions in fertility. Earlier treatment with PGF2 alpha should allow greater time for CL regression, an increase in estradiol and subsequent reductions in circulating P4 that could be critical for fertility. Optimization of follicle size in TAI programs is clearly an intricate balance between oocyte quality, adequate circulating E2 near AI, and adequate circulating P4 after AI.

Incidence of subclinical endometritis and its effects on reproductive performance of crossbred dairy cows

In dairy cattle, uterine infections are not life threatening and often unavoidable; however, they reduce fertility and increase the production costs of properties. The aim of this study was to evaluate the incidence of subclinical endometritis from 32 to 70 days in milk (DIM) and its effects on the reproductive performance of crossbred dairy cows. Lactating cows (Holstein/Gir; n = 172), with no history of retained placenta, without clinical signs of uterine infection were used. The body condition score (BCS) was evaluated on a scale from 1 to 5. Ultrasound examination was performed to evaluate uterine lining and ovarian activity, while vaginal mucus was analyzed by gloved hand. The diagnosis of subclinical endometritis was performed by endometrial cytobrush technique. The samples were collected, stained, and examined microscopically; positive cases for subclinical endometritis were considered with the presence of a parts per thousand yen5 % of neutrophils. Later, the cows were submitted to conventional artificial insemination or timed artificial insemination. The incidence of subclinical endometritis in the herd was 26 %, and this was not affected by the season of calving, presence of corpus luteum, DIM, and parity. Cows with a BCS a parts per thousand currency sign2.50 had a higher incidence of subclinical endometritis. The conception rate to first insemination and pregnancy rate at 150 days postpartum were not influenced by the presence of subclinical endometritis in crossbred dairy cows.

Effect of glycerol on the viability and fertility of cooled bovine semen

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

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.

Técnicas associadas à biotecnologia da reprodução para minimizar os efeitos do estresse térmico e aumentar a fertilidade em vacas leiteiras de alta produção

The dairy sector has undergone considerable economic losses due to low fertility rates due to adverse effects of heat stress on reproduction of cows. Genetic selection for increased production, coupled with the expanding dairy to tropical areas of the planet, and global warming has further aggravated the problem of heat stress. The effects of heat stress are multifactorial and act directly or indirectly at various levels of reproductive tissues, resulting in low fertility of cows, which in practice, results in reduced reproductive efficiency in the property, reducing the producers’ profit. Some strategies related to breeding biotechnology such as fixed-time artificial insemination, embryo transfer and use of BST, can minimize these effects and improve the reproductive efficiency of the herd

Uso de LH ou eCG no último dia do protocolo superovulatório em bovinos

In the last decades several hormonal treatments to induce multiple ovulation and embryo transfer (MOET) have been developed. Tight control of the time of ovulation allowed the use of fixed-time artificial insemination (FTAI) in bovine embryos donors, facilitating animal management. Although, protocols that allow FTAI have evolved and yield as much embryo as conventional protocols that requires estrus detection, substantial increase in viable embryo production has not been observed in superestimulated bovine cattle. The present review put emphasis on superestimulatory protocols in wich the last two doses of pFSH are replaced by eCG or LH. Recent results indicate that an extra LH stimulus (using eCG or LH), on the last day of P-36 superestimulatory treatment, seems to improve transferable embryo yield in both Bos taurus and Bos indicus cattle.