Effect of progesterone on the immune system in consideration of bovine placental retention

Effects of progesterone on the immune system of different species are presented by a literature study. Elevated progesterone concentrations in blood result in more severe course and longer persistence of bacteria in infectious diseases and decrease of the clearance of antibody-coated erythrocytes in vivo. Progesterone suppresses specific components of the immune system and natural killer (NK) cell activity while it has a mainly positive influence on other nonspecific components. It suppresses blastogenesis and cytotoxicity of lymphocytes and increases synthesis of asymmetric antibodies without effector function to block fetal antigens. Progesterone increases the concentration of leucocytes in blood, random migration and chemotactic ability, synthesis of reactive oxygen intermediates (ROI) and antibody-dependent cellular cytotoxicity of polymorphonuclear leucocytes (PMN) and expression of complement receptors, synthesis of ROI and phagocytosis of peritoneal macrophages. In the uterus mainly immunosuppressive effects of progesterone are described (decreased migration of PMN into the gravid uterus, persistence of bacteria or transplants, synthesis of immunosuppressive uterine milk proteins, decreased random migration of PMN) except for an increased content of IgA in the secretory products indicating a significance of progesterone in the pathogenesis of endometritis mainly in the cow and bitch. No correlation could be found between blood concentrations of progesterone and placental retention in cattle. Progesterone takes part in avoiding immunologic aggression of the maternal organism against the semiallogenic conceptus by suppressing specific components of the immune system and NK cell activity. Positive effects on nonspecific components of the immune system could be regarded as compensatory mechanisms to maintain the efficiency of the complete immune system.     

影响牛胚胎移植妊娠率的因素分析

奶牛胚胎移植技术是目前国内奶牛繁殖领域中比较先进的生物技术,作为一项成熟的高新技术已广泛应用于家畜的繁育中,成为提高良种繁殖效率、迅速扩散优良基因的重要手段。但胚胎移植技术在生产中还存在诸多不足,突出表现为妊娠率较低,一般仅为40％-60％,成为制约胚胎移植工作的主要瓶颈,影响其产业化发展。     

The effect of bovine interferon-alpha I1 on pregnancy rate in heifers.

Bovine interferon-alpha I1 (bIFN-alpha) may be useful for enhancing fertility in sheep and cattle because it has extensive sequence homology with ovine and bovine trophoblast protein-1 and, like those proteins, extends corpus luteum lifespan. To test the effectiveness of bIFN-alpha to enhance fertility, several experiments were performed in which inseminated heifers were given i.m. injections of bIFN-alpha approximately at the time of embryo-mediated signals that result in maintenance of the corpus luteum. In Exp. 1, heifers given 20 mg of bIFN-alpha daily from d 14 to 17 tended (P less than .07) to have lower pregnancy rates at d 110 to 112 of gestation (36/75; 48% vs 43/72; 60%). Similar results were obtained in Exp. 2 when heifers received a single injection of 40 mg of bIFN-alpha or placebo at d 13 after estrus; pregnancy rates at d 42 were 39/104 (38%) for bIFN-alpha and 47/98 (48%) for placebo. In Exp. 3, heifers were given gradually increasing doses of bIFN-alpha or placebo from d 11 to 19, because such a regimen had been shown to reduce the number of heifers experiencing hyperthermia after bIFN-alpha injection. Pregnancy rates were 42/95 (44%) for bIFN-alpha and 62/111 (56%) for placebo. Across all three experiments, pregnancy rates were lower (P less than .01) for heifers treated with bIFN-alpha (117/274; 43%) than for heifers treated with placebo (152/281; 54%). In conclusion, these results demonstrate that, under the administration systems used, bIFN-alpha does not increase pregnancy rate, but rather tends to reduce it.     

Effect of pregnancy on clinical manifestation of bovine trypanosomiasis

Four groups of non-pregnant, first second and third trimester pregnant Zebu heifers were used to study and compare the clinical manifestations of Trypanosoma vivax infection. All the infected heifers developed clinical trypanosomiasis manifested by massive parasitaemia, fluctuating pyrexia, anaemia, dull hair coat, emaciation, jugular pulse and enlarged superficial lymph nodes. There were group variations in the severity of signs shown. Infected non-pregnant heifers and heifers in the third trimester of pregnancy developed a more severe form of the disease than pregnant heifers in the first and second trimesters of pregnancy.     

Effect of exogenous circulating anti-bPL antibodies on bovine placental lactogen measurements in foetal samples

Background

The involvement of placental lactogen (PL) in the regulation of foetal growth has been investigated in different species by in vivo immunomodulation techniques. However, when circulating antibodies are present together with the hormone, the procedure for hormonal measurement becomes considerably complex. The aim of this study was the immunoneutralization of bovine placental lactogen (bPL) concentrations in bovine foetal circulation by direct infusion of rabbit anti-bPL purified immunoglobulins (IgG) via a foetal catheter (in vivo study). The ability of a RIA based on guinea pig anti-bPL antiserum, for the measurement of bPL concentrations in samples containing exogenous rabbit anti-bPL immunoglobulins, was also analyzed in in vitro and in vivo conditions.

Methods

Six bovine foetuses were chronic cannulated on the aorta via the medial tarsal artery. Infusion of rabbit anti-bPL IgG was performed during late gestation. Pooled rabbit anti-bPL antisera had a maximal neutralization capacity of 25 μg bPL/mL of immunoglobulin. Interference of rabbit anti-bPL immunoglobulin with radioimmunoassay measurement using guinea pig anti-bPL as primary antibody was first evaluated in vitro. Polyclonal anti-bPL antibodies raised in rabbit were added in foetal sera to produce 100 samples with known antibodies titers (dilutions ranging from 1:2,500 till 1:1,280,000).

Result(s)

Assessment of the interference of rabbit anti-bPL antibody showed that bPL concentrations were significantly lower (P < 0.05) in samples added with dilutions of rabbit antiserum lower than 1:80,000 (one foetus) or 1:10,000 (four foetuses). It was also shown that the recovery of added bPL (12 ng/mL) was markedly reduced in those samples in which exogenous rabbit anti-bPL were added at dilutions lower than 1:20,000. Concentrations of foetal bPL were determined in samples from cannulated foetuses. In foetuses 1 and 6, bPL concentrations remained almost unchanged (<5 ng/mL) during the whole experimental period. In Foetus 3, bPL concentrations decreased immediately after IgG infusion and thereafter, they increased until parturition.

Conclusion(s)

The use of a bPL RIA using a guinea pig anti-bPL as primary antiserum allowed for the measurement of bPL concentrations in foetal plasma in presence of rabbit anti-bPL IgG into the foetal circulation. Long-term foetal catheterization allowed for the study of the influence of direct infusion of anti-bPL IgG on peripheral bPL concentrations in bovine foetuses.     

Effect of pregnancy on gravid sclerosis of bovine uterine arteries

Gravid sclerosis of the uterine artery was histologically examined in multiparous cows. This sclerosis was characterized by a thickening of the intima and a lamination of the internal elastic lamina. It was clearly observed at non-pregnant and early-pregnant stages and in the late postpartum period, but it could not be detected at term-pregnant stages and in the early postpartum period. These results suggest that the gravid sclerosis disappears during pregnancy and re-establishes after parturition. The importance of local factors, e.g. hemodynamics, in the cyclic appearance of gravid sclerosis is discussed.     

Effect of post-insemination progesterone supplementation on pregnancy rate in dairy cows

Progesterone plays an important role in maintenance of pregnancy. It is hypothesized that insufficient progesterone early in pregnancy may result in embryonic loss, and that supplemental progesterone would decrease pregnancy loss in dairy cows. In Experiment 1, 84 cows and 16 heifers from a single dairy operation were selected randomly. Within each age category, controlled internal drug release (CIDR) devices were inserted into the vagina of every other female on Day 4 post-insemination and removed on Day 18 post-insemination. Transrectal ultrasonography was performed to determine pregnancy at 4 time periods [days 30 to 37 (week 5), days 44 to 51 (week 7), days 58 to 65 (week 9), and days 86 to 93 (week 13)]. Progesterone supplementation had no effect on pregnancy rate. In Experiment 2, there were no differences in progesterone concentrations between cows that did and did not receive a CIDR. Further, cows receiving CIDR devices did not have an increase in circulating progesterone concentrations 30 min or 1 h after CIDR insertion. It appears that progesterone supplementation does not increase circulating levels of progesterone in the early pregnant lactating dairy cow. Alterative methods to influence progesterone concentrations and/or early embryonic loss need to be investigated.     

Effect of nutrient intake during pregnancy on fetal and placental growth and vascular development

Remarkable diversity of size and health of offspring exists after normal pregnancies. When pregnancies are complicated by an extrinsic variable such as inappropriate maternal nutrition, birth weight and health of the neonate are substantially affected. The placenta is the organ through which respiratory gases, nutrients, and wastes are exchanged between the maternal and fetal systems. Thus, transplacental exchange provides for all the metabolic demands of fetal growth. Transplacental exchange is dependent upon uterine and umbilical blood flow, and blood flow rates are in turn dependent in large part upon vascularization of the placenta. Therefore, factors that influence placental vascular development will have a dramatic impact on fetal growth and development, and thereby on neonatal mortality and morbidity. Recent work from our laboratories has focused on the effects of nutrient intake during pregnancy on placental growth and vascular development. Both nutrient restriction of the adult dam and overnourishment of the adolescent dam during pregnancy suppress placental cell proliferation and vascularity. Furthermore, placental expression of angiogenic factors and their receptors, factors that are known to affect vascular growth, are perturbed by level of nutrition. Studies in this area will lead to improved methods to manage nutritionally-compromised pregnancies.     

Effects of the dam on equine chorionic gonadotropin concentrations during pregnancy

Breeding trials were designed to determine the influence of the mare on serum concentrations of equine chorionic gonadotropin (eCG) from Day 39 to Day 104 of gestation. Sires were ranked according to mean eCG concentrations found in the groups of randomly selected mares to which they were mated in 1983. Mares were ranked according to their mean eCG concentrations on Days 55, 71 and 85 of gestation (Day 0 = mating), in 1983 and 1985. In the 1986 breeding season, mares that had pregnancies characterized by high eCG levels were mated to sires previously associated with low eCG concentration pregnancies and low producing mares were mated to sires associated with high eCG concentration pregnancies. The highest eCG concentrations (12.8 ug/ml serum) were detected on Day 55 of gestation in mares mated to the low-ranked sire (P<0.01), indicating an influence of the mare on serum eCG concentration. A comparison of eCG production by individual mares in 1985, 1986 and 1987 showed that mares retained the same rank (P<0.001), regardless of the rank of the sire to which they were mated. It was concluded that the influence of the mare predominates in determining eCG concentration. In 1987, the highest ranked sire was mated to the highest eCG producing mares (ranked 1–20) and the second highest ranked sire was mated to mares ranked 21–40. Two distinct subgroups resulted, suggesting that the selection of sires and mares could be used to maximize the production of eCG.     

Plasma bovine placental lactogen concentration throughout pregnancy in the cow; relationship to stage of pregnancy,fetal mass,number and postpartum milk yield

This study characterized the peripheral plasma placental lactogen (bPL) profile throughout gestation and examined the relationship between the stage of gestation, fetal mass, number, and postpartum lactation with circulating levels of bPL in Holstein cows after nonsurgical embryo transfer. Cows (n = 12) were divided into two groups: Group 1 = single embryo recipient cows (n = 5); Group 2 = twin embryo recipient cows (n = 7). Blood was collected about every third day from Day 0 (Day 0 was defined as the first day of standing estrus), then daily for the last 10 d of gestation, and sampling was stopped 1 d postpartum. The cows were milked twice daily at 0800 and 1800 hr. Two twin-embryo recipient cows had abnormal pregnancies; therefore, their data were excluded from that of the group and reported separately. The time trend concentrations of plasma bPL were significantly affected by the stage of gestation (P < 0.01) but not fetal number (P < 0.21). In both groups bPL levels remained low during the first two trimesters, then increased rapidly (P < 0.01) to peak concentrations between Days 200 and 220, and stabilized at this elevated level until parturition. Postpartum milk yields were indistinguishable between the singleton and twin-bearing cows. Calf birth weight and postpartum lactation were both correlated (P < 0.01) to peripheral bPL concentration in singleton cows, however, this relationship decreased with a subsequent increase in fetal number. Cows giving birth prematurely to stillborn calves or to a schistosomus reflexus calf exhibited a deviating bPL profile. These results indicate that peripheral bPL levels are positively associated with the stage of gestation but not with fetal number. Otherwise, the peripheral pattern of bPL is a valuable index for predicting feto-placental viability.     

Assisted hatching of poor-quality bovine embryos increases pregnancy success rate after embryo transfer

Embryos of good, fair and poor quality were collected from superovulated cows and subjected to zona cutting (ZC) treatment using a needle under either an inverted microscope or a stereomicroscope. One (single transfer) or 2 (twin transfer) embryos with or without prior ZC treatment were transferred nonsurgically to recipients. Without the ZC treatment, lower embryonic quality resulted in lower pregnancy success rates. However, the ZC treatment increased the pregnancy success rate following transfer of poor-quality embryos, but not the pregnancy rate after transfer of good- or fair-quality embryos. No differences were observed between the pregnancy success rates after the transfer of embryos treated under the inverted microscope and those after transfer of embryos treated under the stereomicroscope, and this was the same after single and twin transfer. Moreover, ZC treatment of embryos prior to transfer did not result in an increased abortion rate, irrespective of the number of transferred embryos. In conclusion, ZC treatment improves pregnancy success rates following transfer of poor-quality embryos. Moreover, the results indicate that ZC treatment by using a stereomicroscope is practical for on-farm application.     

Effect of delaying the time of insemination with sex-sorted semen on pregnancy rate in Holstein heifers

The objective of the study was to evaluate the interval from onset of oestrus to time of artificial insemination (AI) to obtain the optimum pregnancy rate with sex-sorted semen in Holstein heifers. Heifers in oestrus were detected and inseminated only by using heat–rumination neck collar comprised electronic identification tag at the age of 13–14 months. Heifers (n = 283) were randomly assigned to one of three groups according to the timing of insemination at 12–16 hr (G1, n = 97), at 16.1–20 hr (G2, n = 94) and at 20.1–24 hr (G3, n = 92) after reaching the activity threshold. The mean duration of oestrus was 18.6 ± 0.1 hr, and mean peak activity was found at 7.5 ± 0.1 hr after activity threshold. The mean interval from activity threshold to ovulation was 29.4 ± 0.4 hr. The overall pregnancy per AI (P/AI) was 53.0% at 29–35 days and 50.9% at 60–66 days after AI. There was a significant reduction between G1 (13.8 ± 1.4 hr) and G3 (7.9 ± 1.4 hr) related to the intervals from AI to ovulation time. Sex-sorted semen resulted in significantly higher P/AI at 29–35 days when heifers inseminated in G3 (60.9%) after oestrus than those inseminated in G1 (49.5%) and G2 (48.9%). In terms of fertility, when the temperature–humidity index (THI) was below the threshold value (THI ≤65) at the time of AI, there was a tendency (≤65; 57.2% vs. > 65; 47.1%) for high pregnancy rate. There was no effect of sire on P/AI. In addition, the interaction of the technician with the time of AI was found significant, and three-way interaction of technician, sire and time of AI was tended to be significant on pregnancy rate. Thus, in addition to delaying the time of insemination (between 20.1 and 24 hr) after oestrous detection, THI and experienced technician were also found to be critical factors in increasing fertility with the use of sex-sorted semen in Holstein heifers.     

Advances in recombinant gonadotropin production for use in bovine superovulation

Bovine ovarian hyperstimulation is a process that currently relies on pituitary-derived follicle stimulating hormone (FSH) to facilitate the maturation of multiple follicles to achieve dominance and eventual ovulation. The prevalence of this process, also called superovulation, has more than doubled in the past 10 years, but the efficiency of recovered transferable embryos has remained low at ~6 per collection. The use of pituitary-derived products presents other problems including contamination from other hormones, inconsistencies within and among batches, and the possibility of the spread of disease-transmitting agents. Recombinant gonadotropins have been engineered to yield varieties of FSH and luteinizing hormone from a myriad of heterologous hosts with the resulting products demonstrating various levels of biological activity. Research has also been devoted to alternative delivery methods to reduce the frequency of injections required in current superovulatory protocols. Together, recombinant gonadotropins and alternative delivery approaches potentially provide an economical alternative to the use of pituitary-derived products.     

Effect of flunixin meglumine treatment during and after embryo transfer on the pregnancy rate in cattle

This study aimed to determine the effect of flunixin meglumine treatment during and after the transfer of in vivo produced embryos to Angus (cows) and Holstein (cows and heifers) breeds of cattle on pregnancy rate. Holstein cows were used as donors in the study. A double dose of prostaglandin F2α was administered to the recipient animals for synchronization. Uterine flushing was performed in donors on day 7 after artificial insemination. A total of 295 transferable embryos were obtained. These embryos were transferred to Angus cows (n = 85), Holstein heifers (n = 80) and Holstein cows (n = 130). After the transfer, these animals were divided into three subgroups. The first subgroup (TI) was administered flunixin meglumine during embryo transfer, and the second subgroup (TII) was administered flunixin meglumine both during embryo transfer and on days 8 and 9 after the transfer. The third subgroup (TIII) was not administered anything and it was considered the control group. Pregnancy examination of the recipients was performed on days 30–35 after the transfer using real-time ultrasonography. The pregnancy rates after embryo transfer were found to be 43.52% in Angus cows, 42.5% in Holstein heifers, and 24.61% in Holstein cows (p < .05). When the animals were not classified according to breed, the pregnancy rates in subgroups TI, TII and TIII were found to be 29.29%, 45.10% and 29.79%, respectively (p < .05). In addition, the pregnancy rates were higher in TII and TIII subgroups of Angus cows and Holstein heifers compared to that of Holstein cows (p < .05). As a result, the pregnancy rates obtained after embryo transfer in Angus cows and Holstein heifers were found to be higher than that in Holstein cows. In addition, it was concluded that the administration of flunixin meglumine during and during/after embryo transfer has a positive effect on pregnancy rates in Angus cows and Holstein heifers.     

Effect of age of equine embryos and method of transfer on pregnancy rate

A 2 X 2 cross-classified experiment was conducted to investigate the effect of age of equine embryo (7 vs 8 d postovulation) and method of transfer (surgical vs nonsurgical) on pregnancy rates at 50 d of gestation. Embryos were recovered 7 or 8 d postovulation using a Foley catheter and 3 liters of modified Dulbecco's phosphate-buffered saline (PBS). Upon identification, the embryos were placed in millipore-filtered PBS containing 20% heat-inactivated steer serum and maintained at room temperature until transferred. At the time of recovery, embryos were randomly assigned to be transferred either nonsurgically using a sterile insemination pipette or surgically via a flank incision. For nonsurgical transfer, the embryo was deposited into the uterine body; whereas, in surgical transfer, the embryo was placed in the uterine horn ipsilateral to the corpus luteum. Recovery rates for embryos collected on d 7 (75.5%) or 8 (81.9%) were similar (P greater than .05). Age of embryo did not affect (P greater than .05) pregnancy rate. At 50 d, pregnancy rates were 60 and 57% for mares receiving d 7 or 8 embryos. However, more (P less than .05) pregnancies were obtained after transfer of embryos surgically (72%) than nonsurgically (45%). More (P less than .05) pregnancies were obtained after transfer of d 8 embryos surgically (75%) compared with nonsurgically (40%). Within method of transfer, pregnancy rates were similar (P less than .05) for surgical transfer of d 7 and 8 embryos (69 and 75%), but tended (P less than .25) to be higher for nonsurgical transfer of d 7 embryos (50%) compared with d 8 embryos (40%).(ABSTRACT TRUNCATED AT 250 WORDS)