Adrenocorticotropin administration during early gestation on conceptus development in swine

The purpose of this study was to examine the effect of exogenous adrenocorticotropin (ACTH), administered to gilts during early stages of gestation, upon fetal survival and various maternal and conceptus parameters. Forty-eight gilts of approximately 6-7 months of age were bred by means of artificial insemination after detection of the second estrus and randomly allotted to one of 12 treatment-period groups. Treatment consisted of a daily intramuscular injection of 0, 40 or 80 U.S.P. units of a long acting ACTH preparation for a period of five days. The injection periods were 1-5, 6-10, 11-15 or 16-20 days of gestation with day one corresponding to 48 hours post-estrus detection. All gilts were slaughtered at approximately 37 days of gestation. Forty-two of the 48 inseminated gilts conceived. Conception rate was not different (P>.10) among the 12 treatment-period combinations. Percent fetal survival was greater (P<.09) in gilts receiving 80 U.S.P. units of ACTH (82 +/- 4.3%; X +/- SEM ) than in gilts receiving 40 U.S.P. units of ACTH (68.8 +/- 4.5%). The percent fetal survival in the control group (71.7 +/- 3.9%) was not different (P>.10) from either of the two ACTH treatment groups. A significant (P<.05) treatment by period interaction for percent fetal survival was observed. The lowest percent fetal survival (48.0 +/- 9.0%) was observed in gilts receiving 40 U.S.P. units of ACTH on day 11-15 of gestation. No significant (P>.10) differences were detected among the 12 treatment-period combinations for any of the maternal or conceptus parameters measured.     

Comparison of cleft palate induction by Nicotiana glauca in goats and sheep

The induction of cleft palate by Nicotiana glauca (wild tree tobacco) during the first trimester of pregnancy was compared between Spanish-type goats and crossbred western-type sheep. Cleft palate was induced in 100% of the embryonic/fetal goats when their pregnant mothers were gavaged with N. glauca plant material or with anabasine-rich extracts from the latter, during gestation days 32-41. Seventy-five percent of newborn goats had cleft palate after maternal dosing with N. glauca during gestation days 35-41, while no cleft palates were induced when dosing periods included days 36-40, 37-39, or day 38 only. The induced cleft palates were bilateral, involving the entire secondary palates with complete detachment of the vomer. Eleven percent of the newborn goats from does gavaged during gestation days 32-41 had extracranial abnormalities, most often contractures of the metacarpal joints. Most of these contractures resolved spontaneously by 4-6 weeks postpartum. One newborn kid also had an asymmetric skull due to apparent fetal positioning. No cleft palates were induced in lambs whose mothers were gavaged with N. glauca plant or anabasine-rich extracts during gestation days 34-41, 35-40, 35-41, 36-41, 35-51, or 37-50. Only one of five lambs born to three ewes gavaged with N. glauca plant material during gestation days 34-55 had a cleft palate, but all five of these lambs had moderate to severe contractures in the metacarpal joints. The slight to moderate contracture defects resolved spontaneously by 4-6 weeks postpartum, but the severe contractures resolved only partially. Embryonic/fetal death and resorption (determined by ultrasound) occurred in 25% of pregnant goats fed N. glauca compared to only 4% of pregnant sheep. Nicotiana glauca plant material contained the teratogenic alkaloid anabasine at 0.175% to 0.23%, dry weight, demonstrating that Spanish-type goats are susceptible to cleft palate induction by the natural toxin anabasine, while crossbred western-type sheep are resistant. However, clinical signs of toxicity were equally severe in goats and sheep, even though maternal alkaloid tolerance was generally lower in sheep. We postulate that an alkaloid-induced reduction in fetal movement during the period of normal palate closure is the cause of the cleft palate and multiple flexion contractures. Teratology 61:203-210, 2000. Published 2000 Wiley-Liss, Inc.     

Dietary regulation of maternal and fetal cholesterol metabolism in the guinea pig

Studies to determine the effects of pre-natal interventions on maternal and fetal cholesterol homeostasis were carried out in the guinea pig. Guinea pig dams were fed either non-purified guinea pig diet or diet supplemented with either 1.1% of the bile acid binding resin cholestyramine or 0.25% cholesterol. Whole body rates of endogenous cholesterol synthesis were determined by quantitation of [3H]water incorporation into digitonin precipitable sterols in non-pregnant animals and at 40 and 60 days of gestation in the dam and fetus. Maternal hepatic cholesterol synthesis was reduced 87% by dietary cholesterol and was increased 3.5-fold with cholestyramine feeding. Fetal hepatic and peripheral tissue cholesterol synthesis rates peaked at 40 days gestation when peripheral tissue cholesterol synthesis was 5.7-fold higher and hepatic synthesis 6.2-fold greater than the near adult levels observed at 60 days. Cholesterol synthesis in the fetus was relatively insensitive to dietary manipulations; however, maternal cholestyramine treatment did result in a 1.4-fold increase in fetal carcass cholesterol synthesis at 60 days gestation. These data demonstrate that maternal cholesterogenic systems maintain responsiveness to dietary regulation during pregnancy; whereas fetal cholesterol homeostasis is relatively insensitive to dietary cholesterol throughout gestation yet may respond to induction by maternal cholestyramine treatment during the late gestation period.     

Endocrine profiles during the estrous cycle and pregnancy in the Baird's tapir (Tapirus bairdii)

Serum samples were collected 1–3 times weekly from two Baird's tapirs (Tapirus bairdii) for 6 months in 1987–1988, and for more than 3 consecutive years beginning in 1989 to characterize hormone patterns during the estrous cycle and pregnancy. Based on serum progesterone concentrations, mean (±SEM) duration of the estrous cycle (n = 20) was 30.8 ± 2.6 days (range, 25–38 days) with a luteal phase length of 18.1 ± 0.4 days (range, 15–20 days). Mean peak serum progesterone concentrations during the luteal phase were 1.35 ± 0.16 ng/ml, and nadir concentrations were 0.19 ± 0.03 ng/ml during the interluteal period. Distinct surges of estradiol preceded luteal phase progesterone increases in most (14/20) cycles. Gestation length was 392 ± 4 days for three complete pregnancies. Mean serum progesterone concentrations increased throughout gestation and were 1.83 ± 0.13, 2.73 ± 0.13, and 4.30 ± 0.16 ng/ml during early, mid- and late gestation, respectively. Serum estradiol concentrations began to rise during mid-gestation, increasing dramatically during the last week of pregnancy. Patterns of serum estriol and estrone secretion during pregnancy were similar to that observed for estradiol. In contrast to progesterone and estrogens, serum cortisol concentrations were unchanged during pregnancy or parturition. Females resumed cycling 16.2 ± 2.0 days after parturition (n = 4) and, on two occasions, females became pregnant during the first postpartum estrus. These data suggest that the tapir cycles at approximately monthly intervals and that increases in serum progesterone are indicative of luteal activity. The interluteal period is relatively long, comprising approximately 40% of the estrous cycle. During gestation, progesterone concentrations are increased above luteal phase levels, and there is evidence of increased estrogen production during late gestation. The absence of increased cortisol secretion at the end of gestation suggests that this steroid does not play a major role in initiating parturition in this species. © 1994 Wiley-Liss, Inc.     

Rh isoimmunization during pregnancy: antenatal prophylaxis.

Of 3533 Rh-negative women who began a pregnancy without detectable Rh antibodies, 62 (1.8%) demonstrated evidence of Rh isoimmunization during pregnancy or within 3 days after delivery. All denied transfusions as well as abortions or previous pregnancies not followed by the administration of Rh immune globulin. Rh isoimmunization during pregnancy or within 3 days after delivery, which will not be prevented by the administration of Rh immune globulin after delivery, is the most important cause of residual Rh isoimmunization. A clinical trial of antenatal administration of Rh immune globulin, initially at 34 weeks''s and subsequently at 28 and 34 weeks'' gestation, in 1357 Rh-negative pregnant women who were delivered of Rh-positive babies, was effective in preventing the development of Rh isoimmunization during pregnancy or within 3 days after delivery. Antenatal prophylaxis with Rh immune globulin will be necessary if the incidence of Rh isoimmunization is to be reduced to its lowest possible level. Antenatal prophylaxis at 28 weeks'' gestation is now an insured service in Manitoba.     

Parasite load in guinea pig foetus with real time PCR after maternofoetal transmission of Toxoplasma gondii

Parasite loads of different tissues were assessed in guinea pig foetus after maternal infection. Twelve female guinea pigs were infected with 100 cysts of the 76 K strain of Toxoplasma gondii by the oral route. Inoculation was performed 20 +/- 5 days (G20) or 40 +/- 5 days (G40) after the beginning of gestation. Gestational age was determined by progesterone assay. Maternal and foetal organ samples were taken 60 days after the beginning of gestation. Parasite loads (from placenta, amniotic fluid (AF), cord blood (CB), foetal brain, liver, lung and spleen) were assessed by a real-time PCR quantification using fluorescence resonance energy transfer (FRET) hybridization probes on the Light Cycler. Congenital transmission was proven by the presence of parasites in blood or tissue samples of the foetus in 84.6% (11/13) and 100% (16/16) of cases after inoculation on G20 and G40, respectively. The quantitative analysis of our results after inoculation at G20 and G40 has allowed us to determinate the positive parasitic loads as a function of the origin of the sample and the period of inoculation. The parasite loads expressed as log (parasite/g) were low in AF and CB samples: 1.49 +/- 0.50 and 1.05 +/- 0.10 at G20 and 1.21 +/- 0.36 and 1.20 +/- 0.42 at G40 respectively. In contrast the placenta and the different foetal tissues had higher parasite burdens: 2.89 +/- 0.54 to 5.30 +/- 0.51 at G20 and 2.81 +/- 0.71 to 3.65 +/- 0.59 at G40. All the placentae were positive for parasites even in the two cases with no proven transmission. Real time quantitative PCR using the hybridization probe was a very sensitive and reproducible technique to study the kinetics of congenital toxoplasmosis in the guinea pig model wich is close to that of humans.     

Accuracy of canine parturition date prediction using fetal measurements obtained by ultrasonography

The length of canine gestation is 65 days from the luteinizing hormone (LH) surge. Early and accurate determination of canine gestational age is useful for predicting and managing parturition. We performed a retrospective study on fetal measurements obtained by transabdominal ultrasonographic examination of 83 bitches (32 breeds) to estimate gestational age. Gestational age was estimated using two published tables correlating either (1). embryonic vesicle diameter (EVD), crown-rump length (CRL), body diameter (BD), and biparietal diameter (HD) to the LH surge in mid-gestational beagles or (2). BD and HD to parturition in late-gestation retrievers. Parturition date was predicted by obtaining the difference between the gestational age estimate and 65 days. Bitches were divided into four body weight (BW) groups based on nonpregnant body weight: small (9-20 kg), large (>20-40 kg), and giant (>40 kg). Mean+/-S.D. litter size (LS) was calculated for each BW group. The BW groups were then divided into small, average, or large LS groups. The accuracy of the prediction was not affected by LS but was affected by maternal body weight for small and giant BW groups only. When adjusted for weight, the accuracy of prediction within +/-1 day and +/-2 day intervals was 75 and 87%, respectively. Using stepwise logisitic regression, the most accurate prediction of parturition date was obtained when fetuses were measured at 30 days after the LH surge, regardless of body weight or LS. Parturition date predictions made after 39 days of gestation using only biparietal and BD fetal measurements were <50% accurate within +/-2 days.     

Effects of leptin on fetal plasma adrenocorticotropic hormone and cortisol concentrations and the timing of parturition in the sheep

We investigated whether leptin can suppress the prepartum activation of the fetal hypothalamus-pituitary-adrenal (HPA) axis and delay the timing of parturition in the sheep. First, we investigated the effects of a 4-day intravascular infusion of recombinant ovine leptin (n = 7) or saline (n = 6) on fetal plasma adrenocorticotropic hormone (ACTH) and cortisol concentrations, starting from 136 days gestation (i.e., at the onset of the prepartum activation of the fetal HPA axis. The effects of a continuous intrafetal infusion of leptin (n = 7) or saline (n = 5) from 144 days gestation on fetal plasma ACTH and cortisol concentrations and the timing of delivery were also determined in a separate study. There was an increase in fetal plasma ACTH (P < 0.01) and cortisol (P < 0.001) concentrations when saline was infused between 136-137 and 140-141 days gestation. Plasma ACTH and cortisol concentrations did not rise, however, when leptin was infused during this period of gestation. When leptin was infused after 144 days gestation, there was no effect of a 4- to 5-fold increase in circulating leptin on fetal ACTH concentrations. In contrast, leptin infusion from 144 days gestation suppressed (P < 0.05) fetal plasma cortisol concentrations by around 40% between 90 and 42 h before delivery. There was no difference, however, in the length of gestation between the saline- and leptin-infused groups (saline infused, 150.2 +/- 0.5 days; leptin infused, 149.8 +/- 1.0 days). In saline-infused fetuses, there was a significant negative relationship between the plasma concentrations of cortisol (y) and leptin (x) between 138 and 146 days gestation (y = 81.4 - 7.7x, r = 0.38, P < 0.005). This study provides evidence for an endocrine negative feedback loop between leptin and the HPA axis in fetal life.     

The development of corticosteroid binding globulin-like activity in fetal sheep blood.

Parturition in sheep is initiated by the fetus and is preceded by a rise in fetal cortisol and corticosteroid-binding globulin (CBG) late in gestation. In this study plasma cortisol and CBG concentrations were measured in fetal and maternal circulation from 40 days gestation to early post-partum. The fetal cortisol profile was shown to be triphasic in nature; being high in both the first and last trimester but low in the middle period of gestation. In the last trimester, total cortisol increased steadily, reaching it's highest level just prior to parturition (145 days gestation), before falling to maternal levels over the first 10 days post-partum. The changes seen in CBG concentrations throughout gestation and post-partum mirrored the triphasic nature seen in cortisol levels. CBG was significantly higher at 40, 56 and 140 days gestation than at mid-gestation (77 and 90 days). However, at 145 days gestation there was a significant fall in CBG levels. CBG levels were higher at 1 day post-partum when compared to 145 days gestation, the former rapidly falling to maternal levels over the subsequent 9 days. The maximum binding capacity at 40, 56, 70 and 90 days gestation exceeds the total serum cortisol concentration. However at 140 and 145 days gestation and 1 day post-partum the total serum cortisol exceeds the Bmax. The highest cortisol:Bmax ratio is seen at 145 days gestation due to the fall of CBG binding capacity at this time.(ABSTRACT TRUNCATED AT 250 WORDS)     

Studies with timed-pregnant squirrel monkeys (Saimiri sciureus).

Timed-pregnant monkeys were produced in a large nonhabituated colony of Saimiri sciureus of Bolivian origin. In a colony of 373 females and 40 males, 277 females (74%) were considered to be inseminated, based on microscopic observation of sperm and/or detection of a coagulum (plug) in the vagina. Forty-six full-term progeny were delivered. The mean gestational period was 152.5 days (SD = 3.9 days). For continuous cohabitation, the median time to insemination was five days, with 75% of inseminations occurring within eight days. Pregnancy evaluation (mouse bioassay) indicated a high level of resorptions within the first 50 days of gestation. This may help explain the low birth rates reported for other nonhaibuated colonies.     

Effects of cumulative stressful and acute variation episodes of farm climate conditions on late embryo/early fetal loss in high producing dairy cows

The aim of this study was to determine possible relationships between farm climate conditions, recorded from day 0 to day 40 post-artificial insemination (AI), and late embryo/early fetal loss in high producing dairy cows. Pregnancy was diagnosed by rectal ultrasonography between 28 and 34 days post-AI. Fetal loss was registered when a further 80- to 86-day diagnosis proved negative. Climate variables such as air temperature and relative humidity (RH) were monitored in the cubicles area for each 30-min period. Temperature-humidity indices (THI); cumulative stressful values and episodes of acute change (defined as the mean daily value 1.2 times higher or lower than the mean daily values of the 10 previous days) of the climate variables were calculated. The data were derived from 759 cows in one herd. A total of 692 pregnancies (91.2%) carried singletons and 67 (8.8%) carried twins. No triplets were recorded. Pregnancy loss was recorded in 6.7% (51/759) of pregnancies: 5.6% (39/692) in single and 17.9% (12/67) in twin pregnancies. Using logistic regression procedures, a one-unit increase in the daily cumulative number of hours for the THI values higher than 85 during days 11–20 of gestation caused a 1.57-fold increase in the pregnancy loss, whereas the likelihood of fetal loss increased by a factor of 1.16 for each additional episode of acute variation for the maximum THI values during gestation days 0–40. THI values higher than 85 and episodes of acute variation for the maximum THI values were only recorded during the warm and cool periods, respectively. The presence of twins led to a 3.98-fold increase in pregnancy loss. In conclusion, our findings show that cumulative stressful and episodes of acute variation of climatic conditions can compromise the success of gestation during both the cool and warm periods of the year. Twin pregnancy was confirmed as a main factor associated with pregnancy loss.     

Prenatal and postnatal development of the small intestine in the insectivore Suncus murinus

The development of the small intestine in the insectivore Suncus murinus was noted during the period from 21 days' gestation to 20 days after birth. At 21 days of gestation, the proximal small intestine exhibited the beginning of villus formation, whereas the distal small intestine preserved the stratified epithelium. Stratified epithelium in the distal small intestine changed into a single layer by 24 days' gestation. At 26 days' gestation, each epithelial cell was immature; but by 28 days mature-looking epithelial cells were found. The shape of the villi changed from cuboid to columnar during the same period. The connective-tissue cores of the villi began to develop at 7 days after birth in the proximal small intestine and at 15 days after birth in the distal small intestine. Crypts appeared at 15 days after birth. Endocytosis of epithelial cells took place at 28 days of gestation. In the proximal small intestine, supranuclear vesicle clusters were observed first at birth; they began to decrease both in number and size at 10 days' gestation and then disappeared completely by 20 days after birth. In the distal small intestine, large supranuclear vacuoles were observed first at 28 days of gestation. Although these vacuoles invariably were found up to 15 days after birth, they also disappeared completely by 20 days. Epithelial cells showed a structure similar to those of the adult after weaning.     

Intraovarian adrenergic nerves in the guinea-pig: Development from fetal life to sexual maturity

Summary The development of the intraovarian adrenergic nervous system was investigated in the guinea-pig by use of chemical determination of catecholamines with high performance liquid chromatography (HPLC) and with the formaldehyde-induced fluorescence method for visualization of adrenergic nerves (Falck-Hillarp technique). Ovaries from fetuses (39–40, 45–50, 55–57, 60–63 days of gestation) and young animals (1, 2, 3, 7, 14, 30, 40–45 days of age) were included in the study. The noradrenaline concentration was low in the ovaries from the youngest fetuses but increased with age, reaching a maximum level at 2 days post partum. A marked decrease in noradrenaline concentration from the second to the third day of life was found as a consequence of the rapid increase in the ovarian weight during this time. A similar decrease in ovarian noradrenaline concentration after a period of rapid ovarian growth was noted at 30 days of age. Measurable amounts of adrenaline were found in the ovary only in the fetal stages; the highest concentration (0.73 g) was detected at 55–57 days of gestation.     

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.     

Development of myometrial electrical activity during the first half of pregnancy in the sheep

Uterine myoelectrical activity was recorded in seven pregnant sheep covering the period between 13 and 75 days post-coitum. Activity in the myometrium was present at day 13 and took the form of intermittent spikes of low amplitude. Bursts of spikes of irregular duration became noticeable between days 25 and 40 but most were not coordinated throughout the myometrium. Coordinated bursts of myoelectrical activity, which could be recorded at several sites simultaneously, first appeared between 40 and 65 days. These bursts had similar characteristics to the myoelectrical activity associated with uterine contractions during the last third of gestation. The myoelectrical activity showed a progressive increase in amplitude during the first half of gestation. There was no relationship between plasma progesterone levels and the increase in amplitude or appearance of coordinated bursts of uterine activity.     

Changing prognosis for babies of less than 28 weeks' gestation in the north of England between 1983 and 1994. Northern Neonatal Network.

OBJECTIVE: To investigate the changing prognosis for babies of less than 28 weeks'' gestation. DESIGN: A prospective, collaborative, population based survey. SETTING: The former Northern Regional Health Authority. SUBJECTS: All the births between 1983 and 1994 at 22 to 27 completed weeks'' gestation to women normally resident in the region. MAIN OUTCOME MEASURES: Miscarriage, stillbirth, death in the first year of life, and disability in survivors. RESULTS: There were 479070 registered births in the study period. No baby of 22 weeks'' gestation survived; only eight (4%) of the 197 babies of 23 weeks who were alive at the onset of labour survived for a year-a proportion that did not change during the study period. Survival among other babies of less than 28 weeks improved progressively between 1983-6 and 1991-4, but administration of artificial surfactant to babies requiring ventilation from mid-1990 was associated with further improvement in survival only in those over 25 weeks'' gestation. Babies of 24 weeks required three times as much high dependency care per survivor as babies of 27 weeks (76 v 26 days). The rate of severe disability in the one year survivors of less than 26 weeks'' gestation (30/123; 24%) was similar to that seen in the sampled survivors of 26 and 27 weeks (29/108; 27%); the proportion disabled did not change significantly during the study period. All the children born in 1983, 1987, and 1991 were later reassessed in greater detail: 10% (13/136) seemed destined for a continuing life of total dependency. CONCLUSIONS: Gestation, if accurately assessed, can give a woman facing very preterm delivery a clear indication of the prognosis for her baby and help her judge the appropriateness of accepting obstetric intervention and sustained perinatal support.     

Embryonic and calving losses in bovine mixed-breed twins induced by transfer of in vitro-produced embryos to bred recipients

One or two in vitro-produced (IVP) Japanese Black (JB) cattle embryos at 8 days after in vitro fertilization were transferred to the contralateral uterine horn of previously bred Japanese Shorthorn (JSH) or JSH-JB cross recipients, and then the occurrence of early embryonic death, abortion during mid- and late gestation, and calving loss were recorded. The survival rate of embryos, including indigenous ones, was not affected by the number of embryos transferred, and a significantly higher twinning rate (68% of pregnant recipients at 80 days after transfer) was achieved when two IVP embryos were transferred, as compared with the rate when one IVP embryo was transferred (24%). In late ET (recipients at 8.5-9.0 days after the onset of oestrus), the embryo survival rate (22%) and the pregnancy rate (42%) at 80 days after ET were significantly lower than those rates in the synchronous ET (recipients at 8.0 days after the onset of oestrus; 47 and 79%, respectively). In the early ET (recipients at 6.0-7.5 days after the onset of oestrus), no significant differences from the synchronous ET were detected in these rates. Twenty-six percent of twin pregnant recipients were aborted during mid- or late-pregnancy, and 39% of twin calves were stillborn. The mean gestation length of the twin-bearing JSH dams (276 days) was 1 week shorter than that of the single-bearing JSH dams, and it was 2 weeks shorter than that of the JB dams bearing a single JB calf derived from the IVP embryos. The longer gestation length of single JB calves derived from IVP embryos resulted in a significantly higher mean birth weight than that of in vivo control calves with the standard length of gestation. In conclusion, the number of embryos to be transferred did not affect the embryo survival rate, and the transfer of two IVP embryos to previously inseminated recipients induced a significantly higher twinning rate during early pregnancy than that of one IVP embryo transfer. The incidence of embryonic losses during early pregnancy increased when Day 8 embryos were transferred to the recipients later in the oestrous cycle (>8.0 days). The results suggested that one cause of the high rate of abortions and stillbirths in twin-bearing dams is the difference in the mean gestation length between the native JSH and JB foetuses derived from transferred IVP embryos.     

Evaluation of bendectin embryotoxicity in nonhuman primates: I. Ventricular septal defects in prenatal macaques and baboon

Cynomolgus monkeys, rhesus monkeys and baboons were administered 10 to 40 times the human dose equivalent of Bendectin throughout the major period of organogenesis (22(+/-3)-50 days of gestation). In animals examined prenatally (100 +/- 2 days gestation) the total incidence of ventricular septal defects (VSD) was 40% in cynomolgus monkeys, 18% in rhesus monkeys, and 23% in baboons. The majority of VSD involved the muscular portion of the septum. No dose response was evident and there were no other cardiac or extracardiac defects found except for one baboon fetus with multiple defects. No defects were observed in cynomolgus monkeys administered Bendectin for 4-day periods between 22 and 41 days of gestation. There was no association of Bendectin treatment with any noncardiac defect. In cynomolgus and rhesus monkeys examined at term there was one mitral valve defect and no incidence of VSD. The increased incidence of VSD observed prenatally in all three species and the absence of defects in macaques at term suggests a delay in closure of the ventricular septum in treated animals. The Bendectin-treated monkey may be a suitable model for the study of the pathogenesis of VSD and the mechanism of spontaneous closure of the defect.     

Genetic study of gestation length in Andalusian and Arabian mares

The length of gestation in Andalusian, or Spanish Purebred (SPB) and Arabian (AB) mares reared in Spain was analysed, based on 766 spontaneous full-term deliveries appertaining to 141 mares of SPB breed and 72 mares of AB breed in 31 breeding seasons. The data were obtained from the Yeguada Militar de Jerez de la Frontera stud farm in Cádiz, Spain. The mean length of gestation was of 336.8+/-0.48 days in the SPB mares and 340.3+/-0.63 days in AB mares. To assess the accurate prediction of time of birth the potential effect of a number of factors was investigated. The influences of the breed, mare, month and year of mating, age of the mother, number of births and sex of the foal were statistically significant. The factor have the greatest influence over the gestation length was the mare itself, with a correlation among consecutive births of around 0.4. The effect of inbreeding, both of the mare and foal, was negligible. Gestation length shortened as the breeding season progressed: in both breeds, a delay of 1 month in mating corresponded to a decrease of 3 days in the gestation length. According to our results, gestation length decrease as the mare gets older, with the shortest gestation periods when the mare is 10-12 years old, and from this point on, it slowly increases. The gestation period shortens as the 4th or 5th birth approaches, and then gets progressively longer. The range of variation in gestation length due to the number of births to the mare is of 2.9 days for the AB mares, and 2.2 days for SPB mares. The heritability for the gestation length for AB and the SPB breeds was 0.2, with a repeatability of 0.36 and 0.37, for SPB and AB breeds, respectively. With the data from both breeds, and using a classical approach, the response to selection was estimated if mares with extreme gestation lengths were culled, i.e. lengths which are under 310 days, or over 360 days. According to our results, in the case of SPB, a decrease of 14-45% would occur in the number of extreme gestation lengths, while in the AB breed, this value would decrease from 2 to 39%.     

Variables associated with peripartum traits in dairy cows. I. Effect of dietary forages and disorders on voluntary intake of feed, body weight and milk yield

Daily voluntary intakes of feed by each of 89 Holstein cows were compared between day 220 of gestation and day 30 postpartum over a 21-month period. Diets designed to meet NRC requirements and which contained either chopped hay (29 cows), hay crop silage (HCS; 30 cows) or corn silage (CS; 30 cows) were compared prepartum (27 to 0 days), peripartum (1 day before to 3 days after calving) and postpartum (days 4 to 30 postpartum). Mixed rations, fed during lactation, were 60% forage and 40% concentrate dry matter (DM). Cow management was similar to commercial operations. The experimental hypothesis was that pre-disposition for partum and postpartum disorders (abnormal) could be related either to voluntary intake of different diets or to physical traits. Intakes (DM or estimated net energy) across diets decreased 30% between days 7 and 1 prepartum and averaged 18% and 20% lower peripartum and postpartum, respectively, in abnormal cows than in control cows. Seasonal effects on intakes were significant. In general, changes in body weight and condition and differences in udder edema and milk yield reflected intakes. The results support the original hypothesis.