Inferences of body energy reserves on conception rate of suckled Zebu beef cows subjected to timed artificial insemination followed by natural mating

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

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.

Predicting embryo presence and viability

Pregnancy establishment, followed by birth of live offspring, is essential to all mammals. The biological processes leading up to pregnancy establishment, maintenance, and birth are complex and dependent on the coordinated timing of a series of events at the molecular, cellular, and physiological level. The ability to ovulate a competent oocyte, which is capable of undergoing fertilization, is only the initial step in achieving a successful pregnancy. Once fertilization has occurred and early embryonic development is initiated, early pregnancy detection is critical to provide proper prenatal care (humans) or appropriate management (domestic livestock). However, the simple presence of an embryo, early in gestation, does not guarantee the birth of a live offspring. Pregnancy loss (embryonic mortality, spontaneous abortions, etc.) has been well documented in all mammals, especially in humans and domestic livestock species, and is a major cause of reproductive loss. It has been estimated that only about 25-30 % of all fertilized oocytes in humans result in birth of a live offspring; however, identifying the embryos that will not survive to parturition has not been an easy task. Therefore, investigators have focused the identification of products in maternal circulation that permit the detection of an embryo and assessment of its well-being. This review will focus on the advances in predicting embryonic presence and viability, in vivo.

The manipulation of progesterone profiles during progesterone + estradiol timed ai protocols in dairy cattle: effects on fertility

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

Estratégias para aumento da concentração de progesterona durante o desenvolvimento do folículo ovulatório em vacas holandesas em lactação submetidas à inseminação artificial em tempo fixo

Pós-graduação em Zootecnia - FMVZ

Influence of sire and sire breed (Gyr versus Holstein) on establishment of pregnancy and embryonic loss in lactating Holstein cows during summer heat stress

Heat stress has negative effects on pregnancy rates of lactating dairy cattle. There are genetic differences in tolerance to heat stress; Bos taurus indicus (B. t. indicus) cattle and embryos are more thermotolerant than Bos taurus taurus (B. t. taurus). In the present study, the effects of sire and sire breed on conception and embryonic/fetal loss rates of lactating Holstein cows during the Brazilian summer were determined. In Experiment 1, cows (n = 302) were AI after estrus detection or at a fixed-time with semen from one Gyr (B. t. indicus) or one Holstein sire (B. t. taurus). Pregnancy was diagnosed 80 days after AI. In Experiment 2, cows (n = 811) were AI with semen from three Gyr and two Holstein sires. Pregnancy was diagnosed at 30-40 and at 60-80 days after AI. Cows diagnosed pregnant at the first examination but non-pregnant at the second were considered as having lost their embryo or fetus. Data were analyzed by logistic regression. The model considered the effect of sire within breed, sire breed, days postpartum, period of lactation, and AI type (AI after estrus versus fixed-time). There was no effect of the AI type, days postpartum or milk production on conception or embryonic loss rates. The use of Gyr bulls increased pregnancy rate when compared to Holstein bulls [9.1% (60/657) versus 5.0% (23/456), respectively, P = 0.008; data from Experiments 1 and 2 combined]. Additionally, in Experiment 2, cows inseminated using semen from sire #4 (Gyr) had lower embryonic loss (10%) when compared with other B. t. indicus (35.3% and 40%) or B. t. taurus sires (18.2% and 38.5%, P = 0.03). In conclusion, the use of B. t. indicus sires may result in higher conception rates in lactating Holstein cows during summer heat stress. Moreover, sire can affect embryonic loss and selection of bulls according to this criterion may result in higher parturition rates in lactating Holstein cows. (c) 2006 Elsevier B.V. All rights reserved.

Effects of exposure to cigarette smoke prior to pregnancy in diabetic rats

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

The influence of chronic stress imposed on pregnant rats on the induced bone loss in their adult offspring

Background and objective: Stress during pregnancy may alter offspring susceptibility to diseases during adulthood. In the present study, female Lewis rats were subjected to chronic stress during the gestational period, and the effect of this stress was evaluated histometrically on the progression of ligature-induced bone loss in their adult offspring.Material and methods: After confirming pregnancy, half of the pregnant rats were randomly designated as control animals (no stress regimen was imposed), and the other half was submitted to a chronic stress model (immobilization at cold temperature) between the 7th and the 18th gestational day. After birth, 12 male rats delivered by stressed mothers - Group 1 (G1) - and 12 male rats delivered by non-stressed mothers - Group 2 (G2) - were selected. When birthed rats reached 250 g of body weight, a silk ligature was placed around their maxillary right second molar in order to induce bone loss. The non-ligated left side served as a control. Sixty days later, these animals were sacrificed by anaesthetic overdose. After routine laboratorial processing, images of the histological sections were digitized and submitted for histometric measurement using two parameters: histological attachment loss and bone loss.Results: on the ligated side, G1 presented with greater histological attachment and bone loss than G2 (p < 0.05). on the non-ligated control side, neither of the groups presented with alterations in these parameters (p > 0.05).Conclusion: The chronic stress regimen imposed on pregnant rats produced a greater progression of ligature-induced bone loss in their adult offspring. (C) 0 2011 Elsevier Ltd. All rights reserved.

Mixture of vitamin C, hesperidin and piperidol exposure in pregnancy: Maternal-fetal repercussions

To evaluate the reproductive performance and the development of their offspring on rat pregnancy. Wistar pregnant rats were gavaged with 0 mg/kg wb/day (control group, n = 20) and 166.5 mg/kg/day of a mixture of vitamin C, hesperidin and piperidol (experimental group, n = 20) during the organogenic period (from day 5 to 14 of pregnancy; positive vaginal smear = day 0). The female rats were killed on day 21 of pregnancy. The number of implantations, resorptions (dead embryos), and live/dead fetuses were counted for the analysis of the postimplantation loss rates. There was neither alteration in maternal reproductive performance, but it was verified an increase of the number of fetuses presenting dilated urether, hydronephrosis, and reduced ossification of skull due to the treatment of female rats with a mixture of vitamin C, hesperidin and piperidol, these abnormalities were considered transitory and may not interfere on offspring development. It was not verified other type of major malformation neither the appearance of fetuses presenting atrophy of upper limbs that it could be associated to use of this drug.

Use of cooled bull semen as a strategy to increase the pregnancy rate in fixed-time artificial insemination programs-case report

Semen cryopreservation is still considered suboptimal due to lower fertility when compared to fresh semen. The reasons for the loss of fertility are various and related to irreversible damage caused to the cells during the freeze-thaw process. An alternative to conventional cryopreservation represents the use of chilled bull semen, preventing the damage associated with freezing, thereby guaranteeing greater sperm viability. The aim of this study was to describe the use of cooled bull semen as a strategy to increase the pregnancy for Fixed-Time Artificial Insemination (FTAI) of Nellore (Bos indicus) cows. One ejaculate of a select Nellore bull obtained by electroejaculation was used; the semen sample was fractioned into two aliquots: one diluted in Botu-Bov® extender containing 6.4% glycerol for cryopreservation (BB-F, frozen group) and one diluted in the same extender, free from cryoprotectants and used for cooling (BB-C, cooled semen group). The samples in the BB-C group were chilled to 5°C using an isothermic box and maintained for 24 h prior to use. A total of 349 lactating Nellore cows (70-90 days after birth) were synchronized by the insertion of a progesterone releasing device (1.0 g) and estradiol benzoate (2.0 mg i.m.) on a random day of the estrous cycle (Day 0); FTAI was performed 44-48 h after the removal of the device. The pregnancy rates were 45.71 and 61.49% (P<0.05), respectively, for the cryopreserved or chilled bovine semen groups. In conclusion, the use of bull semen cooled for 24 h represents an alternative to conventionally cryopreserved semen, as determined by the increase the pregnancy per artificial insemination in bovine herds. © 2012 Science Publication.

Effect of exercise on the maternal outcome in pregnancy of spontaneously hypertensive rats

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

Interleukin 10 and tumor necrosis factor-alpha in pregnancy: aspects of interest in clinical obstetrics

The purpose of this study was to review the literature regarding the action of the cytokines interleukin 10 (IL-10) and tumor necrosis factor-alpha (TNF-α) in pregnancy and to emphasize the factors that are of interest to clinical obstetrics. The literature highlights several actions of IL-10 and TNF-α during pregnancy. The actions of these cytokines seem to be antagonistic and dependent on the balance between them, which is orchestrated by the specific immunosuppressive action of IL-10. TNF-α has a characteristic inflammatory action, and it is an additional diabetogenic factor in pregnancy. The loss of the control of the production of these cytokines, with increase of TNF-α, is related to the risk for developing obstetric complications, particularly recurrent fetal loss, gestational diabetes mellitus, hypertensive syndromes, and fetal growth restriction. However, study results are controversial and are not clearly defined. These issues are attributed to the heterogeneity of the studies, particularly regarding their sample sizes and sources, the evaluation methods, and the multiplicity of factors and conditions that influence cytokine production. These questions are fundamental and should be addressed in future investigations to obtain more consistent results that can be applied to obstetric practice.

Comparative efficacy of exogenous eCG and progesterone on endogenous progesterone and pregnancy in Holstein cows submitted to timed artificial insemination

Coordenação de Apoio de Pessoal de Nível Superior (CAPES)