Effects of ingestion of ponderosa pine needles by late-pregnant cows on uterine blood flow and steroid secretion.

Consumption of Ponderosa pine needles by late-pregnant beef cows results in the premature delivery of a viable calf. We have demonstrated the presence of a factor(s) in plasma from cows fed pine needles that specifically increased uterine arterial tone (i.e., decreased arterial diameter) in vitro. This study was designed to investigate changes in uterine blood flow and steroid secretion/uptake by the gravid uterus of cows fed pine needles to induce premature parturition. Sixteen beef cows were laparotomized on d 240 of gestation, and an electromagnetic blood-flow probe was placed around the uterine artery supplying the gravid horn. Cows were randomly assigned on d 250 of gestation to a control (n = 8; 8.2 kg/d of alfalfa hay) or pine needle (n = 8; 2.7 kg/d of pine needles + 5.5 kg/d of alfalfa hay) diet. Uterine blood flow was monitored, and systemic blood (uterine arterial and[or] jugular venous) and uterine venous blood samples were collected daily between 0630 and 0800, just before feeding. Five of eight cows fed pine needles calved prematurely (average day of gestation = 260.2 +/- .6) compared with cows fed the control diet, which calved on 287.6 +/- 3.4 d of gestation. Uterine blood flow in the control cows remained constant from d 250 through the day of parturition. In contrast, uterine blood flow of cows fed pine needles that calved early decreased progressively (P less than .01), declining to 25.2% of its original value by the day of parturition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Specific effects of blood plasma from beef cows fed pine needles during late pregnancy on increasing tone of caruncular arteries in vitro.

Consumption of Ponderosa pine needles by cows during late pregnancy results in the premature delivery of viable calves. Previous observations made at necropsy suggested that vascular insufficiency in the caruncular bed was associated with this induced parturition. The present studies used the perfused caruncular arterial bed of an isolated bovine placentome to determine whether blood plasma collected from cows fed pine needles contained a vasoactive factor(s). Changes in caruncular arterial tone (i.e., long-term changes in vessel diameter) and phasic contractility (i.e., transient reductions in vessel diameter) were evaluated. Tone was quantified as the pressure exerted against a constant intraluminal flow and as the force of contraction during K(+)-stimulated depolarization of membranes. Phenylephrine, an alpha 1-adrenergic agonist, was used to stimulate a phasic contractile response. Jugular blood was collected from beef cows fed pine needles (n = 4) or a control diet (n = 4), during the last 3 d of gestation, and plasma was used for two studies. In Study 1, placentomes were perfused with decreasing dilutions (1:150 to 1:40) of plasma pooled over the last 3 d of pregnancy from cows fed pine needle or control diets. Caruncular arterial perfusion pressures and responses to K+ progressively increased (P less than .05) with decreasing dilutions of plasma from cows fed pine needles, and responses to phenylephrine remained constant. Caruncular arterial perfusion pressures and responses to K+ and phenylephrine remained constant during perfusion of plasma from cows fed the control diet. In Study 2, the changes in vasoactivity of plasma (1:60 dilution) from cows fed pine needles was evaluated during the last 3 d of pregnancy.(ABSTRACT TRUNCATED AT 250 WORDS)     

Use of ultrasonic Doppler waveforms to estimate changes in uterine artery blood flow and vessel compliance

Previous data from our laboratory have demonstrated that uterine blood flow (UBF) and uterine arterial smooth muscle tone vary regularly during the estrous cycle of the cow. Uterine blood flow is highest and uterine arterial tone is lowest at estrus, whereas UBF is lowest and uterine arterial tone is highest during the luteal phase of the cycle. Blood flow through arteries is highly pulsatile; changes in arterial wall properties affect shape of the velocity waveform. This study was conducted to evaluate changes in uterine arterial velocity waveforms throughout the estrous cycle of the cow and to relate these changes to fluctuations in UBF and concentrations of estrogen and(or) progesterone in systemic blood. Pulsatile velocity waveforms were obtained daily from pulsed-wave ultrasonic probes placed surgically on the middle uterine artery of five beef cows exhibiting estrous cycles of normal duration (d 0 = day of estrus). Velocity waveforms varied regularly during the estrous cycle of each cow in association with changes in UBF and steroid concentrations. Further, two distinct velocity waveform shapes were observed during the estrous cycle. The first waveform shape, which was observed during periods of high UBF (d -4 to +4 of the estrous cycle), was characteristic of a highly compliant vessel and was associated with a high estrogen:progesterone ratio. The second waveform shape, which was observed from d 7 to 14 of the estrous cycle, was characteristic of a less compliant vessel and was associated with a depressed estrogen:progesterone ratio. These data suggest that compliance of the uterine artery changes during the estrous cycle in association with the changing estrogen:progesterone ratio in blood.     

Abortifacient effects of a unique class of vasoactive lipids from Pinus ponderosa needles.

Pinus ponderosa needle (PN) ingestion by late pregnant cows results in decreased uterine blood flow, premature parturition, and retained placentae. Further, plasma from PN-fed cows increases caruncular arterial tone (i.e., induces prolonged contraction) in an isolated perfused bovine placentome. A novel class of vasoactive lipids was isolated and identified using a bovine placentome assay-guided fractionation of CH2Cl2 extracts of PN. Placentome perfusion tests indicated that 1-12-dodecanedioyl-dimyristate (14-12-14) was the most potent of the PN lipids for increasing caruncular arterial tone. Late pregnant guinea pigs (GP) were used to evaluate the abortifacient activity of these vasoactive lipids. In Study 1, on d 50 of gestation, part of the control diet was replaced with chopped PN (Diet A) or chopped PN subjected to sequential extraction with diethyl ether (Et2O; Diet B); Et2O and CH2Cl2 (Diet C); and Et2O, CH2Cl2, and methanol (Diet D). The GP on Diets A and B exhibited shorter (P<.01) gestation lengths and reduced (P<.01) pig birth weights than GP on the control diet or Diets C and D. Further, only GP on Diets A and B exhibited retained placentae. In Study 2, on d 50 of gestation, part of the control diet was replaced with chopped PN that had been subjected to exhaustive CH2Cl2 extraction and then infiltrated with either CH2Cl2 alone (Diet E), CH2Cl2 containing 14-12-14 (Diet F), or CH2Cl2 containing isocupressic acid (Diet G); then solvents were evaporated. The GP consuming Diet F had shorter (P<.05) gestation lengths and reduced (P<.05) pig birth weights than did GP consuming Diets E or G. The GP consuming Diet F also exhibited a high incidence of retained placentae. These data provide evidence that a unique class of vasoactive lipids in PN exhibit abortifacient activity in guinea pigs.     

Evaluation of histopathologic and physiologic changes in cows having premature births after consuming Ponderosa pine needles

Premature calving, typified by early expulsion (17 to 43 days) of weak or dead calves and accompanied by retained placentas, was induced in 8 of 9 pregnant cows fed a mixture of Ponderosa pine needles and alfalfa hay. Five control cows of comparable gestation age fed only alfalfa hay maintained normal pregnancies until they were euthanatized at the time the pine needle-treated cows were producing premature calves. Serum specimens from all cows were assayed for progesterone concentration and ovaries and placentomes were examined for histopathologic changes. There were no bacterial, fungal, chlamydial, or viral agents determined to be associated with the premature births. Serum progesterone concentration in the treated cows decreased progressively and were 0.4 to 1.5 ng/ml at the time of premature calving. Histopathologic changes were evident in the placenta and corpora lutea of treated cows only. The number of binucleate trophoblastic giant cells in placentomes was less than normal and the number of necrotic luteal cells in corpora lutea was greater than normal.     

Ponderosa pine needle-induced parturition in cattle.

Needles of the Ponderosa pine (Pinus ponderosa) induce premature parturition in cattle when ingested during late pregnancy, especially during the third trimester. The closer to term, the more likely that pine needles will induce parturition. Experiments were designed to describe the clinical signs and behavior associated with ingestion of pine needles. Pine needles adversely affected only pregnant cows and did not seem to affect nonpregnant, cycling cows, sheep, goats, or rabbits. Premature parturition was more likely if cows ingested the needles after the 8th mo of pregnancy, if they ingested pine needles over a period of 3 d or more, and if cows ate a relatively large amount of pine needles (about 2.2 to 2.7 kg/d). A synthetic progesterone, melangesterol acetate, and a prostaglandin inhibitor (ketoprofen) seemed to be of some prophylactic benefit; however, further research is required to assess the practicality of the approach and the magnitude of the benefit. Ponderosa pine bark and new-growth branch tips, which seem to be more potent inducers of premature parturition, may be useful in the extraction and identification of the parturifacient component(s).     

Maternal and fetal influences on uterine and conceptus development in the cow: II. Blood flow and nutrient flux

Objectives of this study were to evaluate maternal and fetal influences on uterine and umbilical blood flows and nutrient fluxes of gravid uterine tissues of cows. Brahman cows with Brahman or Charolais fetuses and Charolais cows with Brahman or Charolais fetuses were used. Indwelling catheters were placed into a uterine artery and vein, an umbilical vein, and a fetal femoral artery and vein at 220 +/- .4 d after mating. Uterine and umbilical blood flows (liters/min) and net uptakes of oxygen, glucose, lactate, alpha-amino N, urea N, ammonia N, and estrone sulfate by the gravid uterus, fetus, and uteroplacenta were determined on d 227 +/- .4. Uterine blood flows in Brahman cows with Brahman (5.01) or Charolais (4.66) fetuses were similar but less (P less than .001) than in Charolais cows with Brahman (7.14) or Charolais fetuses (9.24), which differed (P less than .01). Umbilical blood flows of Charolais (3.78) were greater (P less than .01) than those of Brahman (2.29) fetuses. Rate of placental D2O clearance as well as net fetal uptake of oxygen, glucose, and alpha-amino N, gravid uterine uptake of alpha-amino N, and uteroplacental uptake of glucose and release of estrone sulfate were greater with Charolais than with Brahman fetuses. Gravid uterine oxygen uptake and estrone sulfate release and gravid uterine and uteroplacental lactate output were influenced by the interaction between cow and fetal breed. It is suggested that fetal growth may be limited by uterine blood flow and by function of the uteroplacenta, particularly in late gestation.     

Nutrition, body condition and reproduction in beef cows: fetal and placental development, and estrogens and progesterone in plasma

Mature, pregnant Hereford cows (n = 17) were used to determine the effect of nutrition and body energy reserves on fetal development, concentrations of nutrients and estrogens in placental fluids, and on progesterone, estrogens and placental lactogen in maternal plasma. On d 145 of gestation, cows were assigned by breeding date to two groups and fed to achieve either a thin (TH; n = 8) or a moderate (M; n = 9) body condition score (BCS) by d 195 of gestation. Body weights, BCS, estrogens, placental lactogen and progesterone in plasma were determined weekly between d 200 and 256 of gestation. Cows were slaughtered on d 259 +/- 1 of gestation, and amnionic and allantoic fluids were sampled and analyzed for concentrations of protein, fructose and estrogens. Body weights and BCS were less (P less than .01) for TH (419 kg; 3.7) than for M (511 kg; 5.7) cows at slaughter. Uterine weights were less (P less than .07), but chorioallantoic weights were greater (P less than .07) in TH than in M cows. Cotyledonary weights were greater (P less than .05) for TH than for M cows, and total fructose in amnionic fluid was reduced (P less than .01) in TH compared with M cows. Concentrations of estradiol, estrone and placental lactogen were greater between d 240 and 256 of gestation for TH than for M cows. We conclude that nutrient intake and(or) BCS of beef cows during late gestation influence placental weight, fructose in amnionic fluid, and placental lactogen, estrone and estradiol in plasma.     

Premature bovine parturition induced by ponderosa pine: effects of pine needles, bark and branch tips

Three components of Ponderosa pine trees were administered via gavage to pregnant cows to determine their ability to induce premature parturition. When tips of branches, bark or needles were administered (2.7 kg/day) starting at 250 d of pregnancy, early parturition was induced in an average of 3.4, 5.0 and 9.1 d, respectively, compared to 31.8 d for water gavaged controls (P less than 0.01). Less pine material was required to induce parturition with tips and bark (9.4 and 11.2 kg/cow, respectively) than with needles (25.0 kg/cow P less than 0.05). Cows fed pine material retained fetal membranes longer after parturition; 13.0 d for needles, 10.5 d for bark and greater than 3.0 d for tips versus less than 0.5 d for controls (P less than 0.01). However, 2 of the cows fed tips died within 48 hours after parturition with fetal membranes intact and the other 2 cows fed tips became depressed, pyrexic and emaciated. They survived after extended veterinary care with antibiotic and fluid therapy. Administration of pine materials modified serum progesterone concentration profiles; there was significant elevation in progesterone 1-3 days after pine material was administered. Subsequently, pine material induced a premature decline in progesterone levels prior to parturition, which occurred more rapidly in cows fed bark and tips suggesting a dose response relationship. Pine material also modified serum cortisol concentration profiles; the main difference was a prolonged elevation in cows receiving tips. Branch tips and bark from Ponderosa pine are more potent in inducing parturition than needles.     

Supplementation of distiller's grains during late gestation in beef cows consuming low‐quality forage decreases uterine,but not mammary,blood flow

Positive effects have been observed in offspring from beef cows supplemented with corn dried distillers grain with solubles (DDGS) during late gestation. The hypothesis of this study was that late gestational DDGS supplementation to beef cows would increase blood flow (BF) to the gravid uterus and mammary gland thus impacting birthweight and post‐natal growth of the offspring. Experiment 1 investigated mammary gland BF in multiparous cows during late pregnancy. Beef cows were fed a control (CON1) diet of low‐quality hay (n = 5) or a supplement diet (SUP1) of low‐quality hay with DDGS [1.7 g/kg of body weight (BW); n = 6]. In Experiment 2, multiparous late pregnant beef cows were fed either a control (CON2) diet of a low‐quality hay (n = 4) or a supplement diet (SUP2) of low‐quality hay with DDGS (1.7 g/kg of BW; n = 5). Uterine and mammary gland BF were recorded every 21 days during late gestation. In Experiment 1, there were no effects of diet or day on mammary gland hemodynamics. In Experiment 2, total and ipsilateral uterine BF was less (p ≤ 0.04) in SUP2 vs. CON2 cows and similar BF to contralateral horns. Mammary gland BF was unaltered by maternal supplementation. Even when measured in two different years in two different environments, mammary gland BF remained unaltered to DDGS supplementation. Investigations on the mechanism that may impact uterine BF during late gestation remain to be known.     

Blood flow and steroid and nutrient uptake of the gravid uterus and fetus of sows

Uterine and umbilical blood samples and blood flow (BF) measurements were obtained from one uterine horn and a single fetus of sows at d 70, 90 and 110 of gestation. Concentrations of O2 in blood and of estrogen (E), progesterone (P), glucose, alpha-amino nitrogen (N) and urea N in plasma were determined. Fetal weights were .267 +/- .018, .633 +/- .019 and 1.208 +/- .073 kg on d 70, 90 and 110, respectively. Uterine and umbilical BF remained constant with day of gestation, averaging 1.51 +/- .06 and .31 +/- .02 liters/min. Uptake of P by a uterine horn and fetus remained constant, but secretion of E by a uterine horn and uptake of E by a fetus increased (P less than .05) with stage of gestation. Uterine and fetal uptake of O2, glucose and alpha-amino N did not change and uptake of O2, glucose and alpha-amino N per kg fetus decreased (P less than .01) as gestation advanced. Secretion of urea N from the uterus was observed, with a concentration gradient from the fetal to the uterine circulations. Uterine and fetal respiratory quotients for glucose were .79 and .38, respectively. Thus, although glucose potentially served as a major energy source, a large portion of the energy requirements of the fetal pig were met by catabolism of other substrates. The decrease in umbilical BF and uptake of nutrients per kg fetus with day of gestation suggested that porcine fetal metabolism declined as pregnancy advanced.     

Pine needle abortion in cattle: associated changes in serum cortisol, estradiol and progesterone

Nineteen spring-calving cows were used in an experiment to study the effect of feeding pine needles on incidence of premature parturitions (abortions) and the associated changes in serum cortisol, estradiol-17 beta and progesterone. The study was conducted over 2 years (1983, seven cows fed pine needles and three controls; 1984, six cows fed pine needles and three controls). Experimental feeding started at an average of 250 d of gestation and continued until parturition. Daily blood samples were taken from the start of feeding through 2 to 4 d after parturition. Feeding pine needles shortened gestation by 16 d and induced a premature normal rise in cortisol and estradiol-17 beta associated with parturition. Cortisol concentrations were also high at the beginning of the bleeding period and remained higher in pine needle-fed cows. An abrupt rise in progesterone concentration occurred after the start of pine needle feeding which then decreased sharply for 7 to 8 d before parturition and did not decrease to control concentrations until after parturition. We conclude that feeding pine needles to pregnant cows in late gestation causes abortions and that these abortions are directly caused by or are associated with changes in steroid metabolism.     

Collateral uterine blood flow in Holstein cows during the third trimester of pregnancy

Blood flow to the gravid and nongravid uterine horns of four multiparous Holstein cows (mean +/- SD, BW=641.8 +/- 95.4 kg; age=4.8 +/- 1.2 years; parity=3.0 +/- 1.2) was measured on days 225, 248, and 266 of gestation. Surgery was conducted on day 214.5 +/- 4.0 of gestation through the flank of the standing cows. Transit-time ultrasonic flow probes (diameter 12 or 14 mm) were fitted surgically around the uterine arteries of each cow. Surgery was completed within two hours of anesthesia, and the animals recovered rapidly following surgery. Uterine blood flow (UBF, l/min) was recorded at 10 sec intervals for approximately 23.5 hours; these values were averaged to determine UBF. The mean gravid UBF was significantly (P<0.05) greater than the nongravid UBF in this study. The range of the gravid and nongravid UBFs varied from 3.61 to 14.05 and 0.72 to 6.54 l/min, respectively. There were no changes (P>0.1) in the mean gravid and nongravid UBFs from day 225 to 266 of gestation.     

Inhibitory effects of CIDR-based ovulation-synchronization protocols on uterine PGF2alpha secretion at the following luteal phase in early postpartum non-cycling beef cows

We investigated whether CIDR-based ovulation-synchronization protocols inhibit secretion of prostaglandin (PG) F2alpha from the uterus in the following luteal phase in non-cycling beef cows. Ten early (a month) postpartum non-cycling Japanese Black beef cows were treated with (1) Ovsynch (GnRH analogue on Day 0, PGF2alpha analogue on Day 7, and GnRH analogue on Day 9; n=3), (2) Ovsynch+CIDR (Ovsynch protocol plus a CIDR for 7 days from Day 0; n=4), or (3) estradiol benzoate (EB) Ovsynch+CIDR (EB on Day 0 in lieu of the first GnRH treatment followed by the Ovsynch+CIDR protocol; n=3). An oxytocin challenge was administered on Day 24 to examine uterine PGF2alpha secretion. Plasma concentrations of 13,14-dihydro-15-keto- PGF2alpha were lower at 30-120 min after oxytocin administration in the Ovsynch+CIDR group and 75 min after administration in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). Plasma progesterone concentrations were higher from Days 1 to 7 in the Ovsynch+CIDR group and from Days 1 to 5 in the EB Ovsynch+CIDR group than in the Ovsynch group (P<0.05). The progesterone concentrations were higher on Days 27 and 29 in both CIDR-treated groups than in the Ovsynch group (P<0.05). In conclusion, in non-cycling beef cows, CIDR-based ovulation-synchronization protocols inhibit uterine PGF2alpha secretion in the following luteal phase and prevent premature luteolysis as is seen with the Ovsynch protocol.     

Treatment with eCG Decreases the Vascular Density and Increases the Glandular Density of the Bovine Uterus

The uterus plays an essential role in mammalian reproduction and is a target of several hormonal protocols used to improve fertility in cattle. Many studies highlighted the importance of eCG treatment following fixed‐time artificial insemination in improving follicular growth, ovulation and pregnancy rates in cattle. Moreover, eCG has been implicated in angiogenesis, leading to important changes in uterine blood flow and vascularisation. However, there is still a lack of information regarding the specific alterations induced by eCG upon glandular and vascular characteristics of bovine uterus. To investigate the influence of eCG on: uterine thickness and area; uterine artery diameter and area; uterine vascular and gland density; and the expression of the VEGFA‐system, the uteri of crossbred beef cows were collected. All cows were submitted to follicular wave emergence synchronization. On day four of protocol, cows submitted to superovulation (n = 6) received 2000 IU eCG, on day eight, after expected follicular deviation, cows submitted to stimulatory treatment (n = 5) received 400 IU eCG. Control cows (n = 5) did not receive eCG. On day five po cows were subjected to ultrassonographic evaluation and slaughtered for uterine tissue sampling on day six po. Uterine vessels and glands were quantified by the counting point stereological method. The VEGFA‐system was localized in different cellular types, showing no qualitative or quantitative differences in the site of expression or the intensity of the positive signal among the groups. Vascular density was decreased in the endometrium of stimulated and myometrium of superovulated cows compared with the control ones, which showed higher vascular density in the myometrium and endometrium of the ipsilateral uterine horn. The uterine gland density was higher in superovulated compared with stimulated and control cows. Thus, we can infer that stimulatory or superovulatory treatments with eCG influence the vascular density in the endometrium and myometrium in cattle.     

Cardiopulmonary effects of xylazine and acepromazine in pregnant cows in late gestation

OBJECTIVE: To determine effects of sedation achieved by xylazine (XYL) or acepromazine (ACE) on cardiopulmonary function and uterine blood flow in cows in late gestation. ANIMALS: 8 cows between 219 and 241 days of gestation. PROCEDURE: Doses of ACE (0.02 mg/kg) or XYL (0.04 mg/kg) were administered IV. Measurements were obtained to determine cardiopulmonary effects and oxygen delivery to the uterus. RESULTS: Heart rate was not significantly affected by administration of ACE, but it decreased markedly after administration of XYL. Uterine artery flow was decreased at all times by XYL and was always less than for ACE. Xylazine increased uterine vascular resistance through 30 minutes and caused reduced PaO2 and increased PaCO2 at all time periods. Acepromazine caused a 5% decrease in PaO2 only at 5 minutes. Xylazine reduced oxygen delivery by 59% at 5 minutes and 32% at 45 minutes. In contrast, ACE caused a nonsignificant reduction of oxygen delivery by 16% at 15 minutes and a return to baseline values by 45 minutes CONCLUSIONS AND CLINICAL RELEVANCE: Xylazine markedly reduces flow and availability of oxygenated blood to the uterus, which may critically impair delivery of oxygen to the fetus at a stressful and important time of development or delivery. Acepromazine was associated with slight reductions of much shorter duration. When XYL is used to sedate pregnant cows, it could impose physiologic distress on the fetus and potentially increase fetal morbidity and mortality. When sedation of the dam is desirable, ACE could be an alternative to XYL.     

Effects of feeding beef females supplemental fat during gestation on cold tolerance in newborn calves.

Effects of prepartum fat supplementation of the dam on cold tolerance of calves were determined in two studies. In Exp. 1, 22 F1, crossbred heifers gestating F2 calves received diets containing either 1.7 or 4.7% dietary fat starting at d 230+/-2d of gestation. Safflower seeds (Carthamus tinctorius) containing 37% oil with 79% linoleic acid were the supplemental fat source in isocaloric-isonitrogenous diets. Calves were separated from their dams at birth, fed pooled dairy-cow colostrum, muzzled to prevent sucking, and returned to their dams in a heated (22 degrees C) barn for 3.5 h. At 4 h of age, a jugular catheter was inserted. At 5 h of age, calves were placed in a 0 degrees C room for 140 min and rectal temperatures and blood samples were obtained at 10- and 20-min intervals. Blood was assayed for glucose, cortisol, and cholesterol. In Exp. 2, 18 multiparous, crossbred beef cows bred to Murray Grey sires were randomly assigned to receive diets containing either 1.7 or 3.1% dietary fat starting at 235+/-2 d gestation. Safflower seeds were used as the supplemental fat source in isocaloric-isonitrogenous diets. At d 260 of gestation, premature parturition was induced in one-half of the cows from each diet group by feeding Ponderosa pine (Pinus ponderosa) needles. Experimental protocols were the same as in Exp. 1, except that cold exposure was at 9 degrees C for 200 min. Rectal temperatures were affected in Exp. 1 by time and diet x time (both P < .01) and diet x calf sex (P < .05) and in Exp. 2 by calf age (P < .05), time, and calf age x time (both P < .01). Plasma cortisol concentrations were affected by time (P < .01) and calf sex x time (P < .05) in Exp. 1 and by time ( P < .01) in Exp. 2. Cholesterol concentrations in Exp. 1 were affected by diet x time (P < .05) and in Exp. 2 by time (P < .05). Plasma glucose concentrations were affected in Exp. 1 by diet (P < .05) and in Exp. 2 by calf age, time, and calf age x time (all P < .01). We conclude from Exp. 1 that feeding heifers supplemental fat during late gestation increased glucose concentrations in the newborn calf, resulting in favorable responses in body temperature in the cold-stressed newborns. This increase in substrate availability suggests a potential positive effect on heat generation in newborns during sustained periods of cold stress. In Exp. 2, premature calves had compromised cold tolerance possibly due to impaired shivering or brown adipose tissue thermogenesis.     

Anomalous Pregnancies during Late Embryonic/Early Foetal Period in High Producing Dairy Cows

This study analyses anomalous cases of gestation ending in pregnancy loss during the early foetal period and their effect on progesterone and plasma pregnancy-associated glycoprotein-1 (PAG-1) concentrations. Data derived from a large-scale ultrasound pregnancy diagnosis programme in high producing dairy cows. Over a 3-year period (2004–2007), a very low incidence (0.5%: 15 of 3094) of anomalous pregnancies was recorded. The results revealed that the following anomalies were detected on days 35–41 of gestation in cows carrying singletons with one single corpus luteum: embryo death in eight cows (0.3%); and embryo in the uterine horn contralateral to the corpus luteum in seven cows (0.2%). All these animals suffered pregnancy loss during the early foetal period. In cows carrying dead embryos, no signs of conceptus degeneration were observed on pregnancy diagnosis. Amnion size (approximately 25 mm diameter) and uterine horn fluid contents were estimated to be similar to those of the normal pregnant cows in this period. In the contralateral gestations, live embryos were observed in all ultrasound checks before pregnancy loss. Uterine fluid contents increased in the two cows in which gestation continued for more than a week. In the cases of embryo death but not in those of contralateral gestation, a drop in PAG-1 levels was noted prior to pregnancy loss. Two cows carrying dead embryos increased with time allantoic fluid contents. The PAG-1 values increased with time in one cow bearing a dead embryo (from 2.31 to 6.79 ng/ml) and in two of the contralateral gestations (from 1.66 to 2.33 ng/ml and from 0.39 to 6.79 ng/ml, respectively). Results of this study indicate that the foetal membranes continue to undergo some activity following embryo death, and that contralateral pregnancy may determine failure of the gestation process.     

草地植物添加剂对肉牛生长性能的影响

通过对草地植物添加剂的最佳配方、最适量以及肉牛的最佳育肥方式对肉牛日增重、屠宰率、净肉率以及肉品质和风味的影响进行研究,旨在分析草地植物添加剂对肉牛生长性能的影响。结果表明,草地植物添加剂能促进肉牛的快速生长,提高肉牛的日增重,其中对于犊牛(C)、架子牛(S)和基础母牛(B)日增重效果最明显的分别是草地植物添加剂C3(44%松针+24%艾叶+12%黄芪+8%微量元素)(P0.01)、S3(48%松针+16%艾叶+8%大蒜+10%黄芪+18%微量元素)(P0.01)和B3(36%松针+14%艾叶+10%大蒜+12%黄芪+28%微量元素)(P0.01);草地植物添加剂的最适量的筛选试验表明,各年龄段的肉牛的草地植物添加剂的添加量占日粮的3.5%育肥效果最明显(P0.01);在北方冷季最佳的育肥方式为舍饲育肥。综上,在北方的寒冷季节养殖肉牛以占日粮3.5%的第3类(C3、S3、B3)草地植物添加剂配合舍饲增肥效果最明显。     

影响子宫血流量因素的研究进展

子宫血流量(u terine b lood flow,U BF)对胎盘机能和胎儿健康都起着关键作用。在整个妊娠期间,胎儿的营养摄入主要是通过母子血液循环获得的。为保证胎儿的健康成长,了解影响子宫血流量的因素是必要的。