Spontaneous reduction of advanced twin embryos: its occurrence and clinical relevance in dairy cattle

Twin pregnancies represent a management problem in dairy cattle since the risk of pregnancy loss increases, and the profitability of the herd diminishes drastically as the frequency of twin births increases. The aim of this study was to monitor the development of 211 twin pregnancies in high producing dairy cows in order to determine the best time for an embryo reduction approach. Pregnancy was diagnosed by transrectal ultrasonography between 36 and 42 days after insemination. Animals were then subjected to weekly ultrasound examination until Day 90 of gestation or until pregnancy loss. Viability was determined by monitoring the embryonic/fetal heartbeat until Day 50 of pregnancy, and then by heartbeat or fetal movement detection. Eighty-six cows (40.8%) bore bilateral and 125 (59.2%) unilateral twin pregnancies. Embryo death was registered in one of the two embryos in 35 cows (16.6%), 33 of them at pregnancy diagnosis. Pregnancy loss occurred in 22 of these cows between 1 and 4 weeks later. Thus, 13 (6.2% of the total animals) cows, carrying one dead of the two embryos, maintained gestation. Total pregnancy loss before Day 90 of pregnancy (mean 69 +/- 14 days) was registered in 51 (24.2%) cows: 7 (8%) of bilateral pregnancies and 44 (35.2%) of unilateral pregnancies, and it was higher (P = 0.0001) for both right (32.4%, 24/74) and left (39.2%, 20/51) unilateral than for bilateral (8.1%, 7/86) twin pregnancies. The single embryo death rate was significantly (P = 0.02) lower for cows with bilateral twins (9.3%, 8/86) than for total cows with unilateral twins (21.6%, 27/125). By way of overall conclusion, embryo reduction can occur in dairy cattle, and the practical perspective remains that most embryonic mortality in twins (one of the two embryos) occurs around Days 35-40 of gestation, the period when pregnancy diagnosis is generally performed and when embryo reduction could be tried.     

Relationship between heat stress during the peri-implantation period and early fetal loss in dairy cattle

The aim of the present study was to establish whether temperature-humidity index values, as a measure of heat comfort, from Days 1 to 40 of gestation could be associated with the pregnancy loss rate in high producing dairy cows. Data from 1391 pregnancies were recorded. Pregnancy was diagnosed by transrectal ultrasonography between Days 34 and 45, and again 90 days after insemination. Pregnancy loss was assumed when the second pregnancy diagnosis on Day 90 proved negative and was registered in 7.8% (108/1391) of pregnancies. Mean and maximum temperature-humidity index values were established for each cow for Days 0 (day of insemination), 1, 2 and 3 after insemination, and averages established for Days 0-3, 0-10, 11-20, 21-30 and 31-40 after insemination. Cow and management variables previously found to be significantly correlated with the early fetal loss in the same geographical area were also recorded. The relative contribution of each factor to the probability of pregnancy loss was determined using logistic regression models. Based on the odds ratio, a strong association with pregnancy loss of the factors warm period of pregnancy (warm period-May to September versus cool-October to April), twin pregnancy (as negative factors: odds ratios 3.1 and 3.4, respectively) and an additional corpus luteum (as a positive factor: odds ratio 0.32) was confirmed. The likelihood of pregnancy loss increased by a factor of 1.05 for each additional unit of the mean maximum temperature-humidity index from Days 21 to 30 of gestation. Logistic regression analysis revealed no significant effects of temperature-humidity index values for the remaining gestation periods. Our results indicate that heat stress can compromise the success of gestation during the peri-implantation period, such that high temperature-humidity index values for the period 21-30 days of gestation are a risk factor for subsequent early fetal loss.     

Clinical implications of induced twin reduction in dairy cattle

Embryo reduction may prevent the negative effects of twinning in dairy cattle; however, the technique may carry an additional risk of pregnancy loss. The aim of this study was to evaluate the effect on pregnancy maintenance of embryo reduction by manual amnion rupture in unilateral and bilateral twin pregnant cows. A secondary objective was to examine the dynamics of endocrine factors following the treatment. On Day 35-41 of gestation 55 cows bearing two live twin embryos (28 bilateral, 27 unilateral) were randomly assigned to a twin reduction group (n = 27; cows fitted with a progesterone releasing intra-vaginal device for 21 days after manual amnion rupture) or control group (n = 28; untreated cows). Pregnancy loss before Day 90 was recorded in nine control and eleven twin reduction cows (32.1% vs 40.7%, respectively, p = 0.508). Logistic regression models indicated that laterality was the only variable significantly affecting pregnancy loss. The pregnancy loss risk was 8.7 times higher for unilateral than for bilateral twin pregnancies (59.3% vs 14.3%, respectively, P < 0.001) yet was similar in the unilateral control and unilateral twin reduction cows (62.3% vs 53.8%, respectively, P = 0.581). In contrast, four of 14 cows with bilateral twin pregnancies undergoing twin reduction lost their pregnancies while no losses were recorded in control cows with bilateral pregnancies (P = 0.049). A rise in plasma progesterone concentration was detected on the day following treatment in the twin reduction group and concentrations remained high within the first week of treatment. Plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations fell between Day 35-41 and Day 42-48, regardless of treatment. Our findings indicate that embryo reduction by manual amnion rupture did not carry an additional risk of pregnancy loss for unilateral twin pregnancies, whereas it increased the risk of pregnancy failure in bilateral twin pregnancies. However, benefits of preventing cows from delivering twins might also be considered when assessing the success of embryo reduction in bilateral twin pregnancies.     

Factors affecting pregnancy loss for single and twin pregnancies in a high-producing dairy herd

Our objective was to determine the magnitude of, and factors affecting, pregnancy loss for lactating Holstein cows on a commercial dairy farm when diagnosed with twin (n = 98) or single (n = 518) pregnancies using transrectal ultrasonography. Pregnancy losses were assessed with records of non-viable embryos at first pregnancy examination and embryo losses between the first (25-40 d after AI) and second (48 and 82 d after AI) post-breeding pregnancy examinations. Among cows diagnosed with single pregnancies, 3.7% were diagnosed with a non-viable embryo at first pregnancy examination, and 4.6% of those diagnosed with a viable embryo underwent pregnancy loss by the second examination. A total of 11.2% of cows diagnosed with twins experienced a single embryo reduction, whereas 13.3% lost both embryos. Overall, the total proportion of cows experiencing pregnancy loss or experiencing embryo reduction was greater for cows diagnosed with twin than single pregnancies (odds ratio; OR = 3.6), resulting in an embryo survival rate of 91.9% for cows diagnosed with single compared to 75.5% for cows diagnosed with twin pregnancies. Season of breeding and milk production were associated with pregnancy loss for single pregnancies, whereas CL number was associated negatively with embryo reduction and pregnancy loss for twin pregnancies. The risk of twinning and double ovulation among pregnant cows increased with days in milk (DIM), and the risk of double ovulation was greater for cows diagnosed with ovarian cysts and lacking a CL at initiation of an Ovsynch protocol. We concluded that in this herd, embryo reduction and pregnancy loss during early gestation was greater for lactating Holstein cows diagnosed with twin compared to single pregnancies. In addition, cows diagnosed with ovarian cysts and lacking a CL had an increased risk for double ovulation.     

Factors affecting pregnancy loss from gestation Day 38 to 90 in lactating dairy cows from a single herd

The present study was designed to establish whether factors such as previous estrus synchronization, corpus luteum and embryo number at the time of pregnancy diagnosis, changes in body condition score, milk production, clinical disease (mastitis or lameness) and the inseminating bull affect pregnancy loss from 38 to 90 days of gestation. We derived data from 601 pregnant lactating dairy cows from a single herd. Pregnancy diagnosis was performed by ultrasonography between Day 38 and 44 following insemination. We also recorded corpus luteum and embryo number at this time. Pregnancy loss was defined as a negative pregnancy diagnosis on the second palpation per rectum undertaken between 90 and 96 days after insemination. Data were analyzed using multiple logistic regression methods. Cows that had an additional corpus luteum were eight times less likely to miscarry. The risk of pregnancy loss was 3.1 times higher in cows bearing twins. A one unit reduction in body condition score from previous partum to 30 days postpartum resulted in a 2.4-fold increase in pregnancy loss. We noted a higher incidence of pregnancy loss in cows inseminated using semen from one of the six bulls used. This particular bull led to a 3.4-fold increase in the rate of pregnancy loss. Logistic regression analysis showed no significant effects of previous estrus synchronization, milk production, clinical disease, body condition at previous partum or at pregnancy diagnosis, or body condition change between previous partum and pregnancy diagnosis. Our findings indicate a positive relationship between the presence of an additional corpus luteum and the maintenance of gestation. Risk factors for pregnancy loss were twin pregnancy, reduced body condition after previous parturition and the inseminating bull.     

A multiple pregnancy register in the north of England.

A regional population-based Multiple Pregnancy Register was established in 1998, with the aim of collecting detailed information on multiple pregnancies to enable research into mortality and morbidity in multiples. Multiple pregnancies are notified to the Register as soon as they are detected, irrespective of whether they resulted in a spontaneous abortion, termination of pregnancy or registered birth. Nine hundred and twenty-six twin pregnancies were recorded during 1998-99, giving a twinning rate of 14.8 per 1000 maternities (rate at birth 13.0 per 1000 maternities). Sixty one per cent of twin pregnancies were detected before 13 weeks of gestation. Chorionicity was determined in 82.6% of 849 twin maternities with at least one stillbirth or livebirth. The fetal loss rate before 24 weeks of gestation was 10.5% (194/1852). The perinatal and infant mortality rates were 40.6 per 1000 births and 32.6 per 1000 livebirths respectively. A prospective Multiple Pregnancy Register not only allows monitoring of trends in multiple birth rates and mortality, but also etiological research and long-term follow-up studies.     

Progesterone supplementation during the early fetal period reduces pregnancy loss in high-yielding dairy cattle

It was hypothesized that sub-optimal progesterone concentrations during the late embryo and early fetal period may act to compromise conceptus development in dairy cattle. The aim of the present study was to test this hypothesis by supplementing pregnant cows with exogenous progesterone following pregnancy diagnosis. The study population consisted of 1098 pregnant lactating cows. Pregnancy was diagnosed by transrectal ultrasonography between 36 and 42 days after insemination. Animals found to be pregnant were randomly assigned to the Control (untreated cows, n = 549) or Treatment (n = 549) groups. Cows in group Treatment were fitted at pregnancy diagnosis with a progesterone releasing intravaginal device (PRID) containing 1.55 g of progesterone, for 28 days. Cows were then subjected to a further diagnosis by palpation per rectum on Day 90 of gestation. Pregnancy loss was registered in 95 (8.7%) cows on Day 90 of pregnancy: 66 (12%) in group Control and 29 (5.3%) in group Treatment. Logistic regression analysis indicated that there were no significant effects of herd, bull, milk production, service number, days in milk at pregnancy and lactation number. Based on the odds ratio, treated cows were 2.4 (1/0.41) times less likely to miscarry, whereas the risk of pregnancy loss was 1.6 times higher in cows that became pregnant during the warm period in comparison to the cool period. These results support the hypothesis that sub-optimal progesterone concentrations in high producer dairy cows may compromise conceptus development. Under these conditions, intra-vaginal progesterone supplementation has the potential to reduce the incidence of pregnancy loss during the early fetal period.     

Ultrasonographic and hormonal monitoring of pregnancy in the saddle back tamarin,Saguinus fuscicollis

Ultrasonography was used in six saddle back tamarin females (Saguinus fuscicollis) to diagnose pregnancy, monitor the patterns of uterine growth and embryonic/foetal development and examine the incidence loss of single embryos/foetuses. Pregnancy was reliably diagnosed 17 days after conception, 10 days earlier than by plasma progesterone measurement. The patterns of uterine and embryonic/foetal growth paralleled those reported for the common marmoset, including a delay in embryonic development. The results support the hypothesis of retardation of organogenesis in most callitrichid species. Individual embryos could be reliably identified from day 50 of pregnancy; a loss of single embryos/foetuses after this stage did not occur. All pregnancies were carried to term, resulting in five times twins and one singleton. The smaller litter size compared to the common marmoset may be due to loss of single embryos at earlier stages of pregnancy or to a lower ovulation rate.     

Factors affecting retention of early pregnancy in dairy cattle

Potential factors affecting retention of pregnancy during weeks 5-9 of gestation were studied in dairy cows and heifers (N = 211) on two farms. Cows were examined by ultrasonography for presence of a viable embryo, and sizes of the corpus luteum (CL) and of follicles > or = 5mm were recorded. Blood samples were taken at each examination and assayed for progesterone and estradiol. Overall pregnancy loss was 11.4%. Cows with two CL did not have greater concentrations of progesterone than cows with one CL and they retained fewer pregnancies (P < 0.01; 73% versus 91%). Pregnancy retention was associated positively with concentrations of progesterone and estradiol during week 5 (P < 0.05). Embryos that were lost apparently died before CL regression. Retention of pregnancy declined in cows with high body condition and as age of the cow increased. Pregnancy retention was lower in cows bred to one of four frequently-used service sires (P < 0.05). Days postpartum, milk production, parity, service number, inseminator, synchronization of estrus, diameter of follicles and size of CL did not affect pregnancy retention. In conclusion, retention of pregnancy during placentation varied with concentrations of progesterone and estradiol, age of cow, body condition and service sire.     

GnRHa for trigger and luteal phase support in natural cycle frozen embryo transfer – A proof of concept study

We aimed to explore whether ovulation induced by a GnRH analogue (GnRHa), followed by daily GnRHa luteal support provides an efficient platform for natural cycle frozen embryo transfer (NC-FET).In this cohort study, included were normo-ovulatory women who underwent NC-FET cycles, under the age of 40, with an antral follicle count > eight. Ovulation was triggered with triptorelin (0.2 mg Decapeptyl; Ferring), and luteal support was initiated two days later, using a Nafarelin inhaler (Synarel, Pfizer), 200 μg twice daily. Main outcome measures were luteal estradiol and progesterone levels (three to five days following ovulation), implantation rate, ongoing pregnancy rate, early pregnancy loss rate, and live birth rate.Fifty-one patients treated between 2017 and 2018 were included. Mid luteal progesterone levels among study patients, were non-significantly different between patients who achieved pregnancy and those who did not, but differed significantly on day 14 following ovulation (86.0 ± 31.3 vs. 9.8 ± 9.5 nmol/L, respectively, p < 0.001). Twenty-three patients achieved a clinical pregnancy (45.1 %); interestingly, there were no chemical pregnancies. Three pregnancies ended in an early abortion at 6–7 weeks gestation, and 20 pregnancies continued as ongoing pregnancies (39.2 %). One patient had a late abortion at 16 weeks gestation, and 14 had a live birth.In conclusion, in this proof of concept study, inducing ovulation with a bolus of GnRHa in NC-FET, followed by repeated daily GnRHa administration, resulted in satisfactory luteal phase steroid levels and high ongoing pregnancy and live birth rates.     

The effects of GnRH treatment at the time of AI and 12 days later on reproductive performance of high producing dairy cows during the warm season in northeastern Spain

It was hypothesized that gonadotropin-releasing hormone (GnRH) treatment at the time of insemination and 12 days later increases conception rates. The aim of the present study was to evaluate the effects of GnRH treatment at the time of insemination or at the time of insemination and 12 days later on reproductive performance during the warm season in high producing dairy cows. The effect of GnRH treatment on the incidence of subsequent twin pregnancies and pregnancy losses was also evaluated. Data were analyzed using logistic regression methods. Of the entire series of 1289 AI, 373 (29%) resulted in pregnancy. Three study groups were established to evaluate the effects of treatment on the conception rate: control (untreated cows, n=431), GnRH-0 (cows receiving GnRH at AI, n=429) or GnRH-0+12 (cows receiving GnRH at AI and at AI+12 days, n=429). Conception rates were 20.6% (89/431), 30.8% (132/429) and 35.4% (152/429) for animals receiving no treatment, GnRH at AI, and GnRH at AI and 12 days later, respectively. Based on the odds ratio, the probability of pregnancy was 0.80 and 0.46 times less likely for cows receiving treatment GnRH-0 and no treatment, respectively, than for cows receiving treatment GnRH-0+12 (reference). Of the 373 pregnant animals, 326 (87.4%) bore singletons and 47 (12.6%) carried twins. The effects of treatment on the dependent variables: twin pregnancy, additional corpus luteum and pregnancy loss were analyzed. Pregnancy loss between 38 and 90 days after insemination was registered in 30 (8%) cows: 17 (5.2%) in single and 13 (27.7%) in twin pregnancies. Fifty-six (15%) cows had an additional corpus luteum. No pregnancy losses were recorded in these cows. Treatment had no effect on the twin pregnancy rate. The treatment GnRH at AI and 12 days later increased the chances of an additional corpus luteum by a factor 3.7 (using the control group as reference). In conclusion, our results support the hypothesis that GnRH treatment at the time of insemination and 12 days later increases the conception rate in high producing dairy cows during the warm season. Although lower than double treatment, strong benefits were also registered following a single GnRH treatment at insemination. Under these conditions, treatment fails to affect the twin pregnancy rate yet increases the incidence of an additional corpus luteum in pregnant cows.     

The production of mixed-species Bos taurus-Bos indicus twin calves

Bos taurus-Bos indicus twin calves were produced by transferring Day 6–8 Bos indicus or Bos taurus embryos to previously inseminated Bos taurus or Bos indicus cows. Embryos were transferred to 112 recipients of which 64 (57.1%) were diagnosed as pregnant by rectal palpation at 7–8 weeks gestation. Twin foetuses were diagnosed in 38 (65.5%) of 58 cows in which the location and number of foetuses was recorded. Substantial foetal losses occurred after 7–8 weeks and only 44 cows calved giving 21 sets of twins and 23 singletons. Six of the single calves were from transferred embryos. The duration of gestation of the twin pregnancies (282 days) was similar to that of single Bos taurus pregnancies (282 days for Jerseys and 286 days for Friesians) and 14 days shorter than single Bos indicus pregnancies (296 days). Consequently Bos indicus members of mixed-species twins were premature at birth and required intensive care to ensure their survival.     

Factors affecting spontaneous reduction of corpora lutea and twin embryos during the late embryonic/early fetal period in multiple-ovulating dairy cows

Spontaneous reduction of advanced twin embryos has been described in high-producing, Holstein-Fresian (Bos taurus) dairy herds. The first objective of the current study was to determine whether management and cow factors could have an effect on such a reduction in twin pregnancies during the early fetal period. Because loss of a corpus luteum was noted in cows suffering twin reduction, we expanded our study to include multiple-ovulating cows carrying singletons. Pregnancy was diagnosed and confirmed from Days 28 to 34 and 56 to 62 postinsemination. Sixty-nine (23.5%) of 293 pregnant cows with two corpora lutea carrying singletons and 132 (28.4%) of 464 twin pregnancies recorded on first pregnancy diagnosis subsequently lost one of the corpora lutea or one of the embryos, respectively. Thirty-four (25.8%) of the 132 twin pregnancies suffering embryo reduction lost one corpus luteum along with the embryo. Corpus luteum reduction always occurred in the ovary ipsilateral to the gravid horn suffering embryo reduction. Binary logistic regressions were performed considering corpus luteum and embryo reduction as dependent variables in single and twin pregnancies, respectively, and several management- and cow-related factors as independent variables. In cows carrying singletons, the risk of corpus luteum reduction was 14.3 (1/0.07) times lower for a given herd, whereas the interaction season by laterality significantly affected corpus luteum reduction such that in cows with two corpora lutea ipsilateral to the horn of pregnancy, the risk of reduction decreased during the winter period. In cows carrying twins, ipsilateral twin pregnancies were 3.45 (1/0.29) times more likely to undergo the loss of one embryo than bilateral twin pregnancies. As an overall conclusion, both corpora lutea and embryos were vulnerable to the effects of stress factors during the early fetal period in cows maintaining their pregnancies. A strong unilateral relationship between the corpus luteum and the conceptus was also observed.     

Plasma concentrations of pregnancy-associated glycoprotein-1 (PAG-1) in high producing dairy cows suffering early fetal loss during the warm season

The present study was designed to establish whether plasma pregnancy-associated glycoprotein-1 (PAG-1) measurements during the early fetal period can be associated with early fetal loss. Blood samples were obtained and ultrasound controls performed on days 35, 42, 49, 56, and 63 of gestation or until pregnancy loss from 98 lactating dairy cows. Radioimmunoassay systems were used to determine PAG-1 and progesterone concentrations. Of the 98 pregnancies investigated 18 (18.4%) suffered early fetal loss: 15 (18.5%) in cows carrying singletons, and 3 (16.7%) in twin pregnancies. In cows suffering pregnancy loss, all living embryos registered on day 35 seemed normal in size and development in all weekly ultrasound controls before fetal expulsion. Using analysis of variance, plasma PAG-1 and progesterone values were not different between no loss and fetal loss groups for every gestation period. Based on the odds ratio, and considering only PAG-1 values obtained on day 35 of gestation, the risk of fetal loss was 10 and 6.8 times more likely in cows with low (<2.5 ng/ml) and high (>4 ng/ml) PAG-1 values, respectively, than in cows with medium PAG-1 values, used as reference. Of the 10 inseminating bulls included in the study, one was related to increased fetal loss by odds ratio of 21.7, whereas one bull was attributed fetal loss rate reduced by odds ratio of 12.5 (1/0.08) These findings can have a clear clinical application: PAG-1 measurements from one single sample taken on day 35 of gestation provided more useful information than a series of values obtained from day 35 to 63 of gestation, and can be indicators of subsequent fetal loss.     

Superovulating cows with follicle stimulating hormone and pregnant mare's serum gonadotrophin

A total of 511 embryos was recovered non-surgically from nearly 100 superovulated or untreated donors. Superovulation with FSH-LH resulted in more corpora lutea, recovered ova, and pregnancies (P<.01) than superovulation with PMSG. No differences were observed in numbers of ovulations, embryos recovered, or pregnancies per donor when prostaglandin F_2α was given to donors 2 versus 3 days following gonadotrophin treatment.Pregnancy rates of 12, 31, 58, and 63% were obtained from groups of embryos classified morphologically as poor, fair, good, and excellent (P<.05). Morphologically normal embryos collected and transferred at 5 to 6 days of gestation resulted in more (P<.05) fetuses (75%) than morphologically normal embryos at 8 to 9 days of gestation (56%), but neither was significantly different from morphologically normal embryos at 6.5 to 7.5 days of gestation (61%). There was no difference (P>.05) between pregnancy rates when retarded embryos from untreated donors (12%) were compared to retarded embryos from superovulated donors (22%). However, a higher proportion of morphologically normal embryos from untreated donors developed into fetuses (71%) than did morphologically normal embryos from superovulated donors (59%, P<.05).     

Spontaneous abortion and preterm labor and delivery in nonhuman primates: evidence from a captive colony of chimpanzees (Pan troglodytes)

Background

Preterm birth is a leading cause of perinatal mortality, yet the evolutionary history of this obstetrical syndrome is largely unknown in nonhuman primate species.

Methodology/Principal Findings

We examined the length of gestation during pregnancies that occurred in a captive chimpanzee colony by inspecting veterinary and behavioral records spanning a total of thirty years. Upon examination of these records we were able to confidently estimate gestation length for 93 of the 97 (96%) pregnancies recorded at the colony. In total, 78 singleton gestations resulted in live birth, and from these pregnancies we estimated the mean gestation length of normal chimpanzee pregnancies to be 228 days, a finding consistent with other published reports. We also calculated that the range of gestation in normal chimpanzee pregnancies is approximately forty days. Of the remaining fifteen pregnancies, only one of the offspring survived, suggesting viability for chimpanzees requires a gestation of approximately 200 days. These fifteen pregnancies constitute spontaneous abortions and preterm deliveries, for which the upper gestational age limit was defined as 2 SD from the mean length of gestation (208 days).

Conclusions/Significance

The present study documents that preterm birth occurred within our study population of captive chimpanzees. As in humans, pregnancy loss is not uncommon in chimpanzees, In addition, our findings indicate that both humans and chimpanzees show a similar range of normal variation in gestation length, suggesting this was the case at the time of their last common ancestor (LCA). Nevertheless, our data suggest that whereas chimpanzees'' normal gestation length is ∼20–30 days after reaching viability, humans'' normal gestation length is approximately 50 days beyond the estimated date of viability without medical intervention. Future research using a comparative evolutionary framework should help to clarify the extent to which mechanisms at work in normal and preterm parturition are shared in these species.     

High rates of pregnancy loss by subordinates leads to high reproductive skew in wild golden lion tamarins (Leontopithecus rosalia)

Across taxa, cooperative breeding has been associated with high reproductive skew. Cooperatively breeding golden lion tamarins (Leontopithecus rosalia) were long thought to have a monogynous mating system in which reproduction was limited to a single dominant female. Subordinates with few reproductive opportunities delayed dispersal and remained in the natal group to provide alloparental care to siblings, thus allowing dominant reproductive females to meet the energetic needs associated with high rates of reproduction and successful infant rearing. The goal of this study was to re-assess monogyny in wild golden lion tamarin groups based upon pregnancy diagnoses that used non-invasive enzyme immunoassay for progesterone and cortisol, combined with weekly data on individual weight gain, bi-annual physical examinations noting pregnancy and lactation status and daily behavioral observations. We established quantitative and qualitative criteria to detect and determine the timing of pregnancies that did not result in the birth of infants. Pregnancy polygyny occurred in 83% of golden lion tamarin groups studied. The loss of 64% of subordinate pregnancies compared to only 15% by dominant females limited reproductive success mainly to dominant females, thus maintaining high reproductive skew in female golden lion tamarins. Pregnancy loss by subordinate adults did not appear to result from dominant interference in subordinate hormonal mechanisms, but more likely resulted from subordinate abandonment of newborn infants to mitigate dominant aggression.     

Analysis of several factors of variation of gestation loss in breeding mares

The files for ultrasound diagnosis of gestating mares belonging to the French equine herd recorded for 3 consecutive years were joined with the files for foal birth of these same mares, allowing the statistical analysis of factors of pregnancy loss. For 28 872 positive diagnoses of gestation, 2898 losses were recorded, that is, a global rate of gestation interruption of 9.12%. The etiology of these interruptions is mainly extrinsic: the year and month of insemination, as well as region for climatic reasons. The intrinsic causes that are implicated are breed of the father (heavy breeds except the hypermetric ones lose fewer pregnancies than warm-blooded breeds), age of the mother (losses are lower in mares of 7 to 10 years of age) and status (mares with foals have fewer pregnancy losses than mares not having foaled the previous year), as well as fetuses with consanguinity (when this increases, the pregnancy losses increase as well). However, the additive genetic effect is extremely low; it corresponds to heritability below 5% and few effects of the environment, common to the offspring of the same mare, were identified. This therefore gives little hope of being able to select against the ‘gestation loss’ trait.     

Effect of exogenous progesterone on pregnancy rates after surgical embryo transfer in mares

A completely randomized experimental design was used to investigate the effect of supplemental progesterone on pregnancy rates of recipient mares. Every other recipient mare received daily 200 mg progesterone in oil beginning the day of surgical embryo transfer and lasting until either Day 120 of pregnancy or until pregnancy failure was confirmed by ultrasound. Progesterone supplementation did not affect pregnancy rate (P > 0.05). Overall, embryos that did not result in pregnancy were of greater mean diameter than embryos that resulted in pregnancy (P < 0.05). Pregnancy rates tended (P < 0.1) to be greater in recipients that were detected to be ovulating the same day or prior to that of the donor and that had been supplemented with progesterone (75 %) as opposed to untreated control mares of the same synchrony group (40 %). Progesterone supplementation did not affect the incidence of embryonic loss; however, there was a slightly higher loss of pregnancies between Day 15 and 30 in treated versus untreated recipients. There was no effect (P > 0.05) of treatment on pregnancy rate for embryos recovered from fertile versus subfertile donor mares. However, overall, there tended (P < 0.1) to be fewer pregnancies with embryos recovered from subfertile (50 %) as compared to fertile donors (75 %). It was concluded that supplemental progesterone at the dosage and frequency described was not beneficial in improving pregnancy rates in cyclic recipient mares after surgical embryo transfer.     

Impact of maternal heat stress at insemination on the subsequent reproductive performance of Holstein, Brown Swiss,and their crosses

Heat stress in hot environments is one of the major factors that can negatively affect milk production, reproduction, and the health of dairy cows. The aim of this study was to evaluate the impact of maternal heat stress at insemination on the subsequent reproductive performance of the pure Holstein (HO), Brown Swiss (BS), and their F₁ crossbred (BF) cows, under subtropical Egyptian conditions. The influence of temperature–humidity index (THI) on the pregnancy rate, fetal loss rate, calving traits, and reproductive indices were investigated. Fetal loss rate of pure HO was significantly increased from 17.1% at low THI to 24.9% at greater THI (odds ratio = 2.09; P = 0.032). Furthermore, abortion and stillbirth rates of pure HO were significantly increased from 3.6% and 3.8%, respectively, at low THI to 7.2% and 5.9%, respectively, at greater THI (odds ratio = 2.17 and 2.58; P = 0.037 and 0.031, respectively). In contrast, BS and BF cows can tolerate the heat stress, as there were no differences in the fetal loss, abortion, and calving difficulty rates at the different levels of THI. Pure HO cows had a significant longer calving interval and days open at high THI (449 and 173 days, respectively), compared with low THI (421 and 146 days, respectively). On the contrary, BS and BF cows had no difference in the calving interval at the different levels of THI. Our results indicate that pure BS and BF cows have a better adaptability and competent reproductive performance than pure HO under subtropical conditions.