Coxiella burnetii and Reproductive Disorders in Cattle: A Systematic Review.

Coxiellosis or Q fever is an infectious zoonotic disease caused by the bacterium Coxiella burnetii. A systematic review using bibliographic research was carried out, and the focus was the relationship between C. burnetii infection and reproductive disorders in cattle [abortion/stillbirth/perinatal morality/weak calves (ASPW complex); retained foetal membranes (RFMs); metritis/endometritis; and infertility/sub-fertility]. The bibliographical search yielded 443 results from databases, but only 61 were deemed eligible. For each disorder, summary tables were prepared, and a scientific evidence score was calculated for each study based on four criteria to help assess the level of evidence for the impact of C. burnetii on the reproductive disorders assessed: type of publication (peer-reviewed or other); type of study (case-control/cohort or other); type of C. burnetii test (direct or indirect); and comparative statistical analysis (yes or no). In addition, summary tables also included information on the study population, country, authors and year of publication, key findings and an assessment of the evidence for an association. For the ASPW complex, RFMs, metritis/endometritis and infertility/sub-fertility, 43, 9, 8 and 19 studies provided data, respectively. On a scale of four, nearly 50% of all study citations had evidence scores of three or four. For ASPW, RFMs and infertility/sub-fertility, there is a significant body of evidence to support a deleterious role for Q fever. In contrast, for metritis/endometritis, the evidence is unclear. It is concluded that there is a substantial need for further research, particularly involving larger animal populations in more controlled settings. To provide more consistency, it is recommended that authors follow more precise definitions of reproductive parameters and more robust diagnostic methodologies.

Cow and management factors and their association with estimates of uterine size and position at the time of insemination of dairy cattle.

This study examines factors affecting uterine size and position determined at 30-36 days postpartum in dairy cattle. The final study population consisted of 328 dairy cows, all calving during the warm season. Uterus position (pelvic, pelvic-abdominal, abdominal) and uterus size (small, medium, large) was measured by ultrasound on Day 30-36 postpartum. Multiparous cows had a larger uterus positioned in the abdominal cavity (p = .03) and a male newborn was associated with a larger uterus (p = .022). The number of cows with the uterus in the abdominal cavity was higher among multiparous and high producer (p < .0001) cows. High producers were 0.41 times more likely to have a small uterus in a pelvic position. The most important finding of this study was that the delivery of a male dairy, rather than beef, calf was related to the least optimal maternal uterus size and position.

Effect of Genetic and Environmental Factors on Twin Pregnancy in Primiparous Dairy Cows.

Twin pregnancies are highly undesirable in dairy cattle; they compromise the health and wellbeing of a cow and dramatically impair the farm economy. Recently, a genomic prediction for twin pregnancies has been developed. The objective of this study was to assess environmental and management risk factors affecting the incidence of twin pregnancies in high-producing dairy cows in their first lactation, with a special emphasis placed on the genomic prediction values of twin pregnancy. Our study population of primiparous cows proved valuable in identifying factors other than genomic predictive values that influence twin pregnancy rates. The odds ratio for twin pregnancies was 0.85 (p < 0.0001) for each unit of a prediction value increase, 3.5 (p = 0.023) for cows becoming pregnant during the negative photoperiod, and 0.33 (p = 0.016) for cows producing ≥42 kg of milk at AI, compared with the remaining cows who produced <42 kg of milk. As a general conclusion, the practical implication of our findings is that genomic prediction values can identify the risk of twin pregnancy at a herd level. Given the cumulative effect of genomic selection, selecting animals with a reduced genetic risk of twin pregnancies can contribute to reducing the incidence of twin pregnancies in dairy herds.

Sexing of Embryos at the Time of Twin Reduction: A Clinical Approach.

This study provides new unique information on bovine twin pairs during the late embryonic period (28-34 days of pregnancy) in relation to (1) a predictive ultrasound measurement that was differential for sexing heterosexual twins; (2) intrauterine embryonic growth patterns in twin pairs; and (3) a higher vulnerability of female embryos compared to males following an induced embryo reduction in heterosexual twins. The study population comprised 92 dairy cows carrying bilateral twins. A length difference between co-twins equal to or greater than 25% in around 50% of pregnancies served to determine the sex of embryos with 100% accuracy in heterosexual twins, which was assessed four weeks later on the remaining fetus after twin reduction. The apparent rates of growth of twin pairs and of individual male and female embryos from day 28 to 34 of gestation were similar to established growth pattern standards for singletons. Mean embryo sizes in relation to gestational age were smaller by some 5 days' growth equivalent in twins compared to singletons. After the reduction in the female embryo in heterosexual twins, the risk of male embryo loss was null. This new information allowed for sex selection at the time of twin reduction.

Direct transfer of a single frozen-thawed in vitro-produced embryo to avoid twin pregnancy in dairy cows.

Fertility of cow receiving fixed-time artificial insemination (FTAI) was compared with cow in which a single frozen-thawed in vitro-produced (IVP) embryo was fixed-time transferred (FTET) to avoid twin pregnancy. The study population was comprised of 596 lactating dairy cows synchronized for oestrus: 440 were fixed-time inseminated (AI cows), and 156 were given GnRH treatment at the time of embryo transfer (ET cows) 8 days post-oestrus. Of the 596 cows, 235 (39.4%) became pregnant: 175 (39.8%) AI cows and 60 (39.8%) ET cows. Twin pregnancy was recorded in 16% of the AI pregnant cows (28/175), whereas no ET cows had twins (0/60). Significant interaction (p < .01) was observed between breeding technique (FTAI vs FTET) and repeat (RB) or not repeat breeding (NRB) for the likelihood of pregnancy. This meant that using RB AI cows as reference, the odds ratio for pregnancy in RB ET cows was 2.2 (p = .04). In conclusion, transfer of a frozen IVP embryo proved useful to prevent the risk of twin pregnancy without affecting fertility.

Twin reduction in the late embryonic period prevents the condition of freemartin in dairy cattle.

The condition of freemartinism occurs in the bovine heterosexual twin foetuses and refers to the resulting infertile female. Vascular anastomoses of the foetal membranes are the major reason of this anomaly. This study examines whether single born heifers following induced twin reduction at 28-34 days of pregnancy could develop normal reproductive functions. The study population derived from 367 lactating dairy cows carrying: unilateral twins (n = 178), bilateral twins (n = 174) or triplets (n = 15), in which manual embryo reduction was performed. The final study population was constituted of 95 single born twin females that reached 12 months of life and entered into the AI period. Of these heifers, 40 have had one unilateral co-twin, 49 one bilateral co-twin, and 6 two contralateral co-twins. A total of 1688 heifers inseminated during the same period were used as controls to compare the rates of pregnancy at 15 months of age, culling due to infertility and birth before the age of 24 months. No differences were detected between groups. With an accepted incidence rate of 50% heterosexuality for all twin sets, we should assume that half of our study population had a male co-twin. Our results indicate lack of effect of the male co-twin on normal development of the gonads and genital tract of his female partner during the late embryonic period.

Clinical Overview of Luteal Deficiency in Dairy Cattle.

Luteal deficiency is defined as reduced progesterone (P4) steroidogenesis by the corpus luteum (CL), either in the amount or duration, or both. This work provides a clinical overview of the current understanding of luteal deficiency and its association with low fertility in dairy cows. Low plasma P4 concentrations during the luteal phase post-artificial insemination (AI) are associated with lower conception rates. Treatments post-AI with P4, gonadotropin-releasing hormone (GnRH) or human chorionic gonadotropin (hCG) improve fertility in some conditions. Sub-luteal function during the late embryonic period (at pregnancy diagnosis, i.e., 28-34 days post-AI), is just one factor among other factors associated with pregnancy loss. Treatment with P4 in cows with one CL favors pregnancy maintenance, while GnRH treatment does the same in cows carrying twins. The diagnosis of sub-luteal function can be made clinically on the basis of plasma or milk P4 concentrations. Automated in-line milk P4 analysis systems to diagnose luteal activity emerge as a very interesting tool in dairy herds. Monitoring plasma or milk P4 concentrations with the help of Doppler ultrasonography to assess the CL function would allow individualizing the luteal phase support.

Follicular Size Threshold for Ovulation Reassessed. Insights from Multiple Ovulating Dairy Cows.

In Bos. taurus cattle, follicular deviation to dominance begins when the selected ovulatory follicle reaches a mean diameter of 8.5 mm. The dominant follicle acquires the capacity to ovulate when it reaches a diameter of about 10 mm. In this study, data derived from 148 cows in estrus with one follicle of ovulatory size and another of 7-9 mm, reveal that the small follicle has the capacity to ovulate alone or with the dominant follicle; thus, giving rise to a single or twin pregnancy. This indicates that a follicle of deviation size may ovulate in the presence of a follicle of ovulatory size.

Transfer of a single fresh in vitro-produced embryo may prevent twin pregnancy without compromising the fertility of the cow.

This study examines whether the transfer of a fresh in vitro-produced (IVP) embryo can avoid the risk of twin pregnancy without reducing the fertility of a cow. The study population was comprised of 416 lactating dairy cows synchronized for oestrus: 294 were fixed-time inseminated (AI cows), and 122 were given GnRH treatment at the time of embryo transfer (ET) an IVP embryo (ET cows). Of the 416 cows, 167 (40.1%) became pregnant. Twin pregnancy was recorded in 20.8% of the AI pregnant cows (21/101), whereas no ET cows had twins (0/66). Significant interaction (p < .01) was observed between breeding technique and the period of the year for the likelihood of pregnancy. This meant that using AI cows during the warm period (May-September) as reference, the odds ratio for pregnancy in ET cows during the warm period was 3.4 (p = .001). In conclusion, transfer of a single fresh IVP embryo proved useful to prevent the risk of twin pregnancy without affecting fertility.

Effects of Heat Stress on Follicular Physiology in Dairy Cows.

Follicular organization starts during mid-to-late fetal life with the formation of primordial follicles. The bilateral interplay between the oocyte and adjoining somatic cells during follicular growth and ovulation may be sensitive to heat stress (HS). Mechanisms giving rise to pre-ovulatory temperature gradients across reproductive tissues are mostly regulated by the pre-ovulatory follicle, and because the cooling of the gonads and genital tract depends on a counter-current transfer system of heat, HS may be considered a major factor impairing ovulation, fertilization and early embryo development. There is evidence of a long-lasting influence of HS on oogenesis and final follicular maturation. Follicular stages that are susceptible to HS have not been precisely determined. Therefore, the aim of this review was to describe the influence of HS during the staged follicular development in dairy cattle, from the activation of primordial follicles to ovulation. Some clinical prospects are also considered.

Unilateral twin pregnancy: A non-infectious factor required for the etiological diagnosis of abortion in dairy herds.

Twin pregnancies are classified into bilateral (one fetus in each uterine horn: 44%) and unilateral (both fetuses in the same uterine horn, right or left: 56%). The incidence of abortion during mid- to late gestation is approximately 1% in cows carrying bilateral twins and more than 40% in cows carrying unilateral twins. In this period, abortion seems most commonly associated with infectious agents. However, although this imbalanced abortion rate may imply that unilateral twin pregnancy is a non-infectious abortion factor, few available data can describe the cause of abortions in twin pregnancies. The current findings suggest that unilateral twin pregnancy is a non-infectious factor required for the etiological diagnosis of abortion in dairy herds.

Cervix-rectum temperature differential at the time of insemination is correlated with the potential for pregnancy in dairy cows.

This study sought to establish whether temperature gradients between the cervix, vagina, and rectum at and 7 days post-artificial insemination (AI) were associated with the incidence of pregnancy in lactating dairy cows (Experiment I; n = 90 ovulating cows) and to evaluate temperature gradient dynamics from the time of insemination to 7 days post-AI under heat stress conditions (Experiment II; n = 16 ovulating and 4 non-ovulating cows). In Experiment I, 39 cows (43.3%) became pregnant. The odds ratio for pregnancy was 2.5 for each one-tenth of a degree drop in cervical temperature with reference to the control rectal temperature at the time of AI (P = 0.01), whereas the same decrease in the cervix-rectum temperature differential 7 days post-AI resulted in an odds ratio of 0.44 (P = 0.02). In Experiment II, 5 of the ovulating cows (31.3%) became pregnant. The mean values of the vagina-rectum, vagina-cervix, and cervix-rectum temperature differentials at AI (day 0), 8 h, 24 h, and 7 days post-AI changed significantly from day 0 to day 7 (within-subject effect; P < 0.02) in ovulating cows but not in non-ovulating cows. Temperature differentials on days 0 and 7 were similar between ovulating cows and cows of Experiment I. Overall, our findings support the notion that a temperature differential between the caudal cervical canal and rectum at AI may be an indicator of the likelihood of pregnancy. Possible prospects of confirming estrus at the herd-level are also suggested.

Inducing ovulation with human chorionic gonadotrophin improves the pregnancy rate in lactating dairy cows receiving an in vitro-produced embryo.

While the global use of in vitro-produced embryos in dairy cattle is on the rise, several technical aspects of embryo transfer procedures have not yet been optimized. This study compares the effects of inducing ovulation using human chorionic gonadotropin (hCG) versus gonadotropin-releasing hormone (GnRH) at the end of a 5-day progesterone(P4)-based protocol for oestrous synchronization on the pregnancy rate of lactating dairy cow recipients of in vitro-produced embryos. Fresh embryos were transferred on Day-seven post-oestrus to ovulating cows receiving GnRH or hCG (groups GnRH and hCG, n = 60 each). Pregnancy was diagnosed by ultrasound on Day 28 post-oestrus. Forty-nine cows became pregnant: 16 in GnRH (26.7%) and 33 in hCG (55%). Taking GnRH-treated cows as reference, the odds ratio for pregnancy of hCG-treated cows was 3.3 (p = .002). In conclusion, hCG treatment given at the end of a 5-day P4-based protocol for oestrous synchronization improved the pregnancy rate in lactating dairy cows receiving an in vitro-produced embryo.

Practical Aspects of Twin Pregnancy Diagnosis in Cattle.

Twin pregnancies are an economically unwanted phenomenon in dairy cattle, not only because they increase pregnancy losses, but also because antibiotics usage and culling rate of the dam are also dramatically increased due to them, furthermore animal welfare issues are also affected through them. In cattle, under field conditions using an early pregnancy determination tool, the first accurate diagnosis from the pregnancy status is available from around day 28, although further confirmations of pregnancy are required. Twin pregnancy diagnosis is available either by rectal palpation or ultrasonography. The measurement of pregnancy specific proteins are also available to determine gestation, but there is still a long way to go to properly identify twin pregnancies. In this commentary, we compared our own results with the literature data in this field with a special emphasis on the clinical practices.

Thermal Mechanisms Preventing or Favoring Multiple Ovulations in Dairy Cattle.

While cows are predominantly monovular, over the past 30 years the incidence of multiple ovulations and thus twinning has increased considerably alongside milk production. Multiple pregnancies are not desirable as they negatively affect the health of cows and the herd economy. Although causal mechanisms associated with multiple ovulations have been extensively revised, the process of multiple ovulations is not well understood. Recent studies on the thermal biology of the reproductive system have shown how thermal mechanisms may prevent or favor multiple ovulations. This review focuses on this relationship between thermal dynamics and multiple pregnancies. Cooling of the pre-ovulatory follicle is able to regulate ovulation. In effect, pre-ovulatory local cooling of the female reproductive system favors male and female gamete maturation and promotes fertilization. Thermal stress is proposed here as a model of stress. Periods of high ambient temperature affect the processes of pre-ovulatory follicular cooling and multiple ovulations. While the ratio between unilateral and bilateral multiple pregnancies is normally close to one, under heat stress conditions, this ratio may be 1.4 favoring unilateral multiple pregnancies. A ratio approaching unity is here proposed as an indicator of cow wellbeing.

Inducing Ovulation with hCG Improves Fertility Outcomes of Co-Dominant Follicle Drainage to Avoid Twin Pregnancy in Dairy Cows.

Twin pregnancies are undesirable in dairy cattle as they dramatically compromise cow lifespan and, consequently, herd economy. Clinical problems in cows arise from the time of pregnancy diagnosis to pregnancy loss, abortion, or parturition. The drainage of co-dominant follicles in cows with two or more follicles at insemination prevents twin pregnancy. The objective of this study was to compare the effectiveness of draining the smaller of two follicles through a simplified maneuver not requiring ultrasonography in cows in their third or more lactation, and then inducing ovulation immediately before artificial insemination (AI) with GnRH or human chorionic gonadotrophin (hCG). Animals were monitored by ultrasound at AI and randomly assigned to the groups: follicular drainage and treatment with GnRH (Deph; n = 60), follicular drainage and treatment with hCG (hCG; n = 60), and non-drainage (ND; n = 60) as control cows. On the basis of odds ratios, cows treated with hCG were 2.1 times more likely to become pregnant than control animals. Our results reveal the efficacy of hCG treatment at AI in cows with two follicles of pre-ovulatory size subjected to a simple follicular drainage procedure.

Benefits and Risks of Preventing Twin Pregnancies.

Clinical problems associated with twin pregnancies have been well established, and twin births are now considered undesirable or even disastrous for the dairy cattle industry and the individual cow. The high incidence of early fetal loss, abortion during the mid-lactation period, dystocia, stillbirth, and placenta retention should be considered a preventable consequence of management, as these disorders greatly compromise the welfare and productive lifespan of a cow carrying or delivering twins. The use of sexed semen generates herd replacements and additional heifers, so a proposed strategy for twin pregnancy prevention is the transfer of a single in vitro-produced female beef cow embryo to cows not suitable for producing replacements. Another proposed strategy is drainage at insemination of co-dominant follicles to prevent twin pregnancies in cows with genetic merit. As a result, embryo survival should improve, economic losses associated with twin pregnancies will be prevented, beef output from the herd will be increased, and the health and welfare of the cow will certainly benefit. In this review, the clinical prospects of preventing or avoiding twin pregnancies using both procedures are discussed.

Twin Pregnancies in Dairy Cattle: Observations in a Large Herd of Holstein-Friesian Dairy Cows.

Multiple pregnancies have devastating consequences on the herd economy of dairy cattle. This observational study examines incidence patterns based on data from the ultrasonographic examination of 1130 multiple pregnancies in cows in their third lactation or more carrying twins (98.8%), triplets (1.1%), or quadruplets (0.08%), and 3160 of their peers carrying singletons. Cows became pregnant following a spontaneous estrus with no previous hormone treatments. Irrespective of a significant decrease (p < 0.0001) in the conception rate (28-34 days post-insemination) during the warm period of the year, the multiple pregnancy rate was similar for both warm (26.5%) and cool (26.3%) periods. The incidence of unilateral multiple pregnancies (all embryos in the same uterine horn) was higher than that of bilateral pregnancies (at least one embryo in each uterine horn): 54.4% versus 45.6% (p < 0.0001). This difference rose to 17% during the warm season (p = 0.03). Pregnancy was monitored in unilateral multiple pregnancies until abortion or parturition (n = 615). In the warm period, the parturition rate was 43% compared to 61% recorded in the cool period (p < 0.0001). Thus, a warm climate is the main factor compromising the fate of multiple pregnancies. Some clinical suggestions are provided.

Effects of twin pregnancy prevention strategies such as GnRH dose and drainage of the smaller follicle on ovulation in dairy cows with two follicles of pre-ovulatory size in the same ovary.

We examined the effects of a single or 2.5-fold dose of dephereline [a gonadotropin-releasing hormone (GnRH) analogue] as well as the drainage of the smaller follicle at the time of insemination on ovulation in dairy cows with two follicles of pre-ovulatory size in the same ovary. The three study groups included 220 monovular cows (control), 110 non-drained cows with two follicles, and 110 cows with two follicles, of which one was drained. In each group, cows treated with a single dose or 2.5-fold dose of dephereline showed similar results following treatment. Ovulation failure of the non-drained follicle occurred in 29.1% of the drained cows, whereas ovulation occurred in 96% of the non-drained and control cows. Twin pregnancy was recorded in 19.4% of the pregnant non-drained cows with two follicles. In conclusion, the increased dephereline dose did not improve the ovulation rate in any group. Follicular drainage, however, prevented twin pregnancy in cows with two follicles, but also resulted in an increase in the non-drained follicle's rate of ovulation failure.

Transfer of a single embryo versus drainage of subordinate follicles to prevent twin pregnancies in dairy cows. Why not both?

In this study, we present two proposed approaches to prevent twin pregnancies in dairy cattle: 1) single, in vitro-produced embryonic transfer into a recipient cow or 2) subordinate follicle drainage at the time of insemination. Both procedures lead to improved embryonic survival. As the use of sexed semen generates herd replacements and additional heifers, we propose the transfer of a single female cattle embryo into cows that are not suitable for producing replacements, and follicular drainage in lactating cows with genetic merit. This should eliminate economic losses associated with twin pregnancies and increase cattle output of the herd.