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1.
This study was designed to examine the effects of oestradiol (E2) on sperm transport in the swine uterus. The bicornuate swine uterus is optimal for the study of the uterine transport and peristalsis because the influence of various factors can be examined on each uterine horn independently. Forty swine uteri (with or without ovarectomy) were perfused for a period of up to 7 h. Two different E2 concentrations (3 or 30 pg/ml) in the perfusion medium were administered for 30 min unilaterally. Through an intracervical catheter 1 ml of a high concentrated dextran blue solution was administered directly in the upper part of the cervix. After bilateral perfusion of the swine uterus with a bolus of 0.3 IU oxytocin the distribution of coloured particles was assessed macroscopically before and after incision of the uterine horns. Coloration was evaluated by two observers blinded to the site-specific administration of E2. In the 10 ovarectomized uteri with the 3 pg/ml E2 concentration a unilateral distribution towards the side of oestradiol administration was observed in six uteri, in four it was a bilateral distribution. In the 10 non-ovarectomized uteri with the 3 pg/ml E2 concentration a uni- and ipsilateral coloration was observed in five uteri, in five it was a bilateral distribution. In the 20 uteri with 30 pg/ml E2, a unilateral coloration of the uterus horns was observed in all uteri. Oestradiol is one of the main factors, which influences the direction of the sperm transport in a dose-dependent manner, in the perfused swine uterus.  相似文献   

2.
OBJECTIVE: To evaluate methods for on-farm measurements of uterine contractility in postpartum dairy cows by comparing data simultaneously recorded by use of 2 intrauterine pressure (IUP) devices and quantified electromyographic (EMG) signals. ANIMALS: 5 cows during the first 48 hours after parturition. PROCEDURE: 2 EMG electrodes were implanted on the surface of the gravid uterine horn. Parturition was induced by injection of a prostaglandin F2alpha analogue at day 274 of gestation. An open-tip catheter and pressure microtransducer were transcervically inserted and affixed to a caruncle immediately after calving. Changes in IUP were recorded concurrent with EMG recordings during 2-hour periods at 2, 6, 12, 18, 24, 36, and 48 hours after parturition. Novel acquisition and analysis software programs were used with a digital data-filtering capability for evaluation of IUP and EMG signals. RESULTS: The method for intrauterine fixation of the 2 pressure measurement instruments was effective and allowed easy, externally guided removal of the devices 48 hours after parturition. There was a high correlation between the data obtained by the 2 pressure measuring systems. Good correlation was also found between pressure data obtained by the open-tip catheter system and EMG signals. Although the quantified IUP and EMG signals were highly comparable, synchronization was not always evident during visual inspection of these signals. CONCLUSIONS AND CLINICAL RELEVANCE: The open-tip IUP catheter system with a special fixation method is suitable for use in on-farm studies. It will enable investigators to record natural and pharmacologically influenced uterine contractility in early postpartum dairy cows.  相似文献   

3.
The uteri of 22 Holstein heifers were monitored during 58 interovulatory intervals by transrectal ultrasonographic imaging. The ultrasonographic appearance of the uterus was influenced by the stage of the estrous cycle. Profound changes in characteristics visualized by ultrasonography included thickness of the uterine body, ultrasonographic evidence of edema, and accumulation of intravaginal and intrauterine fluids. Scores representing intravaginal fluid, intrauterine fluid, ultrasonographic texture, and number of gray-scale zones (comprising the image of the uterus) increased before ovulation, then decreased until approximately day 3 to day 6 (ovulation = day 0). The scores for uterine shape and number of cross sections of a uterine horn in one 5-MHz field began to increase before ovulation, reached a high plateau during the period associated with maximal progesterone production, and decreased before the time associated with estrus and ovulation.  相似文献   

4.
Ultrasonically detectable characteristics of the uterus and embryo and palpable uterine tone were assessed in 10 postpartum mares. A bright fern-like pattern of ultrasonic uterine echogenicity, outlining the endometrial folds, was observed for an average of 2.1 ±0.2 days following parturition (range, 1 to 3 days). Unexpectedly, the uterus was quiescent throughout the postpartum interval, based on daily one-minute contractility scans. Contractility was maximal on Days 12 to 15 of pregnancy in both postpartum (n=7) and nonparturient (n=7) mares. The mean diameter of ultrasonically detectable intrauterine fluid collections increased (P<0.05) abruptly between days 1 and 2 postpartum and gradually decreased (P<0.05) between days 4 and 7; no collections were detected after day 16. There was no effect of day on echogenicity of the intrauterine fluid collections; on all days, fluid was relatively black or nonechogenic, suggesting that puerperal endometritis was not a problem in this group. Because the increase in intraluminal fluid occurred after parturition and in temporal association with a decrease in diameter and tone of the uterus, the fluid collections apparently represented a physiologic influx from the involuting uterus rather than residual placental fluid. Involution of the horns was completed by day 27 (formerly nongravid horn) and day 31 postpartum (formerly gravid horn), based on failure to detect further significant decreases in diameter. However, the formerly gravid horn was larger (P<0.05) in diameter than the formerly nongravid horn on each of Days 1 to 35 postpartum (end of experiment), indicating residual effects on uterine size. When averaged over both horns, uterine diameters were larger on Days 0 to 24 (Day 0=day of ovulation) of pregnancy in postpartum mares than in nonparturient mares; by Day 25, diameters were similar between statuses. By approximately Day 6 of pregnancy, uterine contractility and ultrasonic endometrial exhotexture were similar between postpartum mares and nonparturient mares. Uterine tone was greater (P<0.05) in postpartum mares than in nonparturient mares on all days between Day 0 and 25. An unexpected, transient increase in uterine tone was detected on Day 5 of pregnancy in both postpartum mares and nonparturient mares. No differences were found between reproductive statuses in patterns of embryo mobility, the day of fixation of the embryonic vesicle (postpartum, Day 15.3 ±0.4; nonparturient, Day 15.0 ±0.3), and diameter of the embryonic vesicle on the day of fixation (postpartum, 22.1 ±1.4 mm; nonparturient, 19.4 ±l.6mm). However, mean uterine tone and mean horn diameters on the side of fixation were greater (cranial and middle cornual segments; P<0.05) or tended to be greater (caudal segment; P<0.1 ) on the day of fixation in postpartum mares than in nonparturient mares. In all postpartum mares, fixation occurred in the formerly nongravid horn. Enhanced uterine tone in postpartum mares may account for the occurrence of fixation on the same day for the two reproductive statuses, despite the larger uterus in postpartum mares.  相似文献   

5.
Mechanisms of intrauterine migration were examined in 55 ewes. In the first experiment, corpora lutea were removed from unilaterally ovariectomized ewes on d 4 (d 0 = estrus) and pregnancy was maintained by giving exogenous progesterone. In Exp. 2, the reproductive tract was altered surgically such that embryos initially entered the uterine horn contralateral to the site of ovulation. In Exp. 3, ewes received beads of silastic polydimethylsiloxane that released either cholesterol or estradiol-17 beta in an attempt to mimic embryonic synthesis of estradiol. In the fourth experiment, unilaterally ovariectomized ewes were superovulated and spacing of embryos within the uterus was then examined. In all experiments, ewes were slaughtered on d 15 and recovery of embryos or beads from each uterine horn indicated that migration had occurred. All ewes in Exp. 1 and 2 that had two conceptuses experienced embryonic migration. Beads impregnated with estradiol migrated farther (P less than .01) than cholesterol-containing beads (27.6 +/- 4.3 vs 12.5 +/- 1.6 cm, respectively). In Exp. 4, only one conceptus had migrated into the contralateral horn in all ewes. These results demonstrated that 1) embryonic migration was not affected by local vs systemic exposure to progesterone, 2) embryos migrated into the unoccupied horn, regardless of the initial horn of entry, 3) estradiol may stimulate embryonic migration, and 4) conceptuses were not equally distributed between horns.  相似文献   

6.
Uteroferrin,also known as type 5 tartrate resistant acid phosphatase ( ACP5 ) or TRAP,is an iron-containing glycoprotein secreted by uterine gland epithelium (GE) in response to progesterone and transported across the placental areoalae into the fetal circulation and allantoic fluid to deliver iron and to stimulate hematopoeisis in pigs.This study determined if ACP5 was expressed in the ovine uterus in response to pregnancy,progesterone,interferon tau,placental lactogen,and placental growth hormone.ACP5 protein was present in uterine GE of cycfic and early pregnant ewes,particularly between days 18 and 120 of pregnancy.ACP5 mRNA was expressed in uterine GE of cyclic and pregnant ewes in the same temporal and cell-specific manner.ACP5 was present in secretions from uterine glands,i.e.,uterine milk,and aUantoic fluid from days 40 to 80 of pregnancy,and in uterine flushings from cyclic and early pregnant ewes.Progesterone induced expression of ACP5 mRNA and intrauterine infusion of recombinant ovine interferon tau further stimulated ACP5 expression in uterine GE of ewes,but intrauterine injections of ovine placental lactogen and ovine growth hormone had no effect on ACP5 expression in uterine GE.These results indicate that ACP5 is:1 ) expressed only in GE in response to progesterone ;2 ) secreted into the uterine lumen and transported into the conceptus via plaeental areolae during pregnancy;and 3) present in secretions from uterine GE and in allantoic fluid.The roles of ACP5 in the ovine uterus may include transport of iron across the placenta and stimulation of hematopoiesis.  相似文献   

7.
8.
The fertility was compared between ejaculated and cauda epididymal sperm sensitized with prostatic fluid in dog after freeze-thawing using the fertility of ova from the contralateral ovary after injection (2 × 10(8) sperm) into dog uterus on the unilateral ovariectomized side, on the basis of the presence or absence of conception. No significant difference was observed in sperm quality after freeze-thawing between the two groups and conception rates were equivalent and low. Therefore, to achieve a high fertility by intrauterine insemination of canine frozen-thawed ejaculated and cauda epididymal sperm, intrauterine insemination on both sides is recommended, rather than insemination with a lot of sperm of the uterine horn on one side.  相似文献   

9.
In horses, limited data is found regarding the vascular events during uterine involution at the puerperal period. Thus, we aimed to evaluate the morphological aspects (size of uterus and intrauterine fluid content) and the hemodynamics (endometrial and mesometrial vascular perfusion) of the uterus during its postpartum involution process. Ten mares were daily scanned by transrectal color Doppler ultrasonography from the first day postpartum (d1) to the 16th day after first postpartum ovulation (D0 = ovulation). The formerly gravid horn (GH) and formerly nongravid horn (NH) were individually evaluated. A reduction (P < .05) in the uterine diameter was observed during the first 7 days postpartum, and the rate of uterine involution decreased after this period. The involution was completed on d21 and d24 for the NH and GH, respectively. Presence of intrauterine fluid was present in large amounts between d1 and d2 postpartum, followed by a decrease (P < .05) between d4 and d7. No fluid was observed after d16 postpartum or after the third day postovulation (D3). During the early postpartum period, an increase (P < .05) in the endometrial and mesometrial vascularization was detected, respectively, between d1 and d4, and between d1 and d2. The vascular perfusion did not differ after d4 for endometrial tissue, whereas was reduced (P < .05) between d2 and d10 for mesometrium. After the first postpartum ovulation, an increase (P < .05) in vascular perfusion was observed from D0 to D5, followed by a decrease (P < .05) between D5 and D11 and an increase (P < .05) between D11 and D14. The novel vascular perfusion profile here described in the endometrium and mesometrium after ovulation is similar to the uterine vascular profile observed during estrous cycles and early pregnancy, indicating a fast return of the mare's uterus to cycling postpartum conditions.  相似文献   

10.
The uterus of Miniopterus fraterculus (Thomas & Swan 1906) is bicornuate and asymmetrical, the right uterine horn being larger than the left in parous and nulliparous females. Ovarian and uterine function is asymmetrical; 94% of observed ovulations originated in the left ovary and all implantations occurred in the right uterine horn. Growth and development of ovarian follicles follow the typical eutherian mammalian pattern. The preovulatory Graafian follicle differs from that of most hibernating verspertilionids in that the cumulus oophorus is relatively small. Two types of follicular atresia occur. The first type, in which the stratum granulosum degenerates before degeneration of the oocyte, occurs in multilaminar follicles. The second type occurs in primary and early secondary follicles and is characterized by the oocyte showing the first signs of regression.  相似文献   

11.
To clarify the mechanism of implantation, relationship between positioning of the mouse embryo in the uterus and distribution of uterine glands along the long axis of the uterine horn was examined by three-dimensional remodelling of the uterine endometrium. There were two unique regions in the endometrium. Uterine glands were distributed widely from mesometrial to anti-mesometrial side in one region. It was localized from lateral to anti-mesometrial side in another. These different regions were alternately aligned throughout the uterine horn. The number and position of embryos was consistent with that of the latter region. This study suggests that the type of distribution of uterine glands is closely related to the positioning of the embryo in mice.  相似文献   

12.
The aim of the study was to localize oxytocin receptors (OTR) and measure mRNA expression of OTR in the canine uterus with and without the influence of progesterone. Uterine samples were taken from nine anoestrous and eight dioestrous bitches during ovariohysterectomy. Histological changes were evaluated in haematoxylin and eosin (HE)‐stained samples. Purified polyclonal antibody for OTR was used in immunohistochemistry to localize receptors in uterine layers. Relative mRNA concentration of OTR was evaluated with real‐time PCR from full‐thickness uterine samples taken from the middle horn and the body. Myometrial smooth muscle cells, endometrial luminal epithelium (LE) and deep and superficial glandular epithelium were positively stained for oxytocin receptors in non‐pregnant animals. No significant difference in staining intensity was detected between uterine middle horn and body. However, the staining intensity of LE was significantly higher in dioestrous than in anoestrous uteri (p < .05). Leucocytes and endothelium of blood vessels were also positively stained for OTR. Real‐time PCR showed no significant differences in OTR mRNA expression between the middle horn and the body of the uterus, or between anoestrous and dioestrous uterus. No correlation was noted between OTR mRNA expression and blood progesterone concentration. In conclusion, despite the apparent inactivity, the uterus of the non‐pregnant bitch expresses OTR. The distribution or relative expression of OTR does not differ between uterine horn and body in dioestrus or anoestrus except in LE. LE may have more oxytocin‐dependent activity during dioestrus than anoestrus.  相似文献   

13.
A growing body of evidence indicates that intrafollicular progesterone receptor signaling pathways are obligatory for follicle rupture. However, the intrafollicular localization and regulation of progesterone receptor expression during the periovulatory period in cattle are not known. In this study, we determined the effect of the preovulatory gonadotropin surge on localization and expression of progesterone receptor mRNA in bovine periovulatory follicular and luteal tissue. Ovaries containing preovulatory follicles or new corpora lutea (CL) were collected at approximately 0, 6, 12, 18, 24 (preovulatory follicles) and 48 h (CL) after a GnRH-induced LH surge (n=5-8 per timepoint). Expression of progesterone receptor mRNA was detected in periovulatory follicular and luteal tissue at all timepoints examined. Relative levels of progesterone receptor mRNA were dramatically upregulated within 6h after the LH surge compared to all other time points (P<0.0001). In situ hybridization analysis revealed that the significant increase in progesterone receptor mRNA expression was localized to the granulosal layer of preovulatory follicles. Our results indicate that progesterone receptor mRNA expression is upregulated specifically in the granulosal layer of bovine preovulatory follicles following the LH surge. Progesterone receptor signaling pathways may help mediate the effects of the preovulatory LH surge on follicle rupture in cattle.  相似文献   

14.
The effects of luteolytic doses of PGF2 alpha (25 mg Dinoprost) and its synthetic analogues Cloprostenol (500 micrograms), Luprostiol (15 mg) and Tiaprost (525 micrograms) on bovine myometrial activity were investigated using a miniature pressure transducer placed in one uterine horn. The compounds were administered intravenously to 4 lactating cyclic cows at diestrus, proestrus, estrus and metestrus. Intrauterine pressure changes were assessed by computerized planimetry of the pressure tracings 30 minutes before and 60 minutes after treatment. Baseline intrauterine pressure was set at zero and treatment effects were expressed as percent change from an equivalent control period (= 100%). Following administration of Dinoprost there was a significant increase of uterine contractility in diestrus (515%), proestrus (198%) and metestrus (256%), but not in estrus. In comparison to PGF2 alpha the analogues Luprostiol and Tiaprost were less effective (Luprostiol: 195% and 154% in diestrus and proestrus resp., Tiaprost: 215% during diestrus), while Cloprostenol did not cause a significant change of intrauterine pressure in any stage of the estrous cycle. The results indicate that the myotonic effects which F2 alpha-prostaglandins exert on the uterus of cycling cows is affected both by the type of prostaglandin and the stage of the estrous cycle.  相似文献   

15.
An experiment was performed to evaluate the effect of the side of ovulation with respect to the previously gravid uterine horn on fertility of cows inseminated at one of two periods postpartum. All cows were treated with an intravaginal progesterone insert for 7 d and received estradiol benzoate (2 mg, i.m.) at the time of device insertion, prostaglandin F2alpha (25 mg, i.m.) at the time of device removal, and estradiol benzoate (1 mg, i.m.) 30 h after device removal. All cows were inseminated 28 to 30 h after the second treatment with estradiol benzoate, regardless of observed estrus. Cows treated in Period 1 received inserts at 16 to 20 d postpartum and were inseminated at 25 to 29 d postpartum. Cows treated in Period 2 received inserts at 26 to 30 d postpartum and were inseminated at 35 to 39 d postpartum. Diameter of the largest follicle at insert removal was greater in cows treated in Period 2 (10.1 +/- 0.3; mm +/- SEM) than in cows treated in Period 1 (9.1 +/- 0.3; P < .05). Diameter did not differ with the side of ovulation in respect to the previously gravid uterine horn. Diameter was greater in cows 5 to 9 (10.3 +/- 0.3) than in cows 3 to 4 (9.0 +/- 0.3) or 10 to 13 (9.4 +/- 0.6) yr of age (P < .01). The proportion of cows that ovulated from the ovary contralateral to the previously gravid uterine horn was greater (P < .05) than of those that ovulated from the ipsilateral ovary, and the incidence of ovulation was reduced in cows 3 to 4 yr of age (P < .01). Conception rate tended to be greater for ovulation from the ipsilateral compared with the contralateral ovary, relative to the previously gravid uterine horn (P < .10) and for ovulation from the right than the left ovary (P < .06). Conception rate was less if cows ovulated a follicle that was < 9 mm than a follicle > or = 9 mm in diameter at insert removal (P < .01) and was greater in cows inseminated in June than in April or May (P < .05). In conclusion, in cows in which estrus was synchronized at 25 to 39 d postpartum, ovulation from either the ovary ipsilateral to the previously gravid uterine horn, or the right ovary, tended to increase fertility.  相似文献   

16.
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.  相似文献   

17.
Uterine activity was monitored in three, 2-year-old nulliparous Ayrshire heifers using intrauterine balloon-tipped catheters and pressure transducers during the oestrous cycle, after ovariectomy and following the intravenous infusion of progesterone and oestradiol-17 beta. During the oestrous cycle uterine activity, as measured by the frequency and amplitude of contractions, was greatest around oestrus and declined during the luteal phase of the cycle; there was a close correlation with peripheral progesterone concentrations. In two animals after bilateral ovariectomy spontaneous uterine activity persisted, whilst in the third animal the uterus was quiescent. In the first two heifers intravenous progesterone infusions reduced the spontaneous uterine activity, eventually completely abolishing it. There was evidence of a dose response effect at the two infusion rates. Oestradiol benzoate infusions initially inhibited spontaneous uterine activity before stimulating contractions with some evidence of a dose relationship. As demonstrated in normal cyclical and steroid-infused animals, uterine activity appears to be under the influence of both hormones although the influence of progesterone is greater.  相似文献   

18.
Maternal recognition of pregnancy refers to the requirement for the conceptus (embryo and its associated extra-embryonic membranes) to produce a hormone that acts on the uterus and/or corpus luteum (CL) to ensure maintenance of a functional CL for production of progesterone; the hormone required for pregnancy in most mammals. The pregnancy recognition signal in primates is chorionic gonadotrophin which acts directly on the CL via luteinizing hormone receptors to ensure maintenance of functional CL during pregnancy. In ruminants, interferon tau (IFNT) is the pregnancy recognition signal. IFNT is secreted during the peri-implantation period of pregnancy and acts on uterine epithelia to silence expression of estrogen receptor alpha and oxytocin receptor which abrogates the oxytocin-dependent release of luteolytic pulses of prostaglandin F2-alpha (PGF) by uterine epithelia; therefore, the CL continues to produce progesterone required for pregnancy. Pig conceptuses secrete interferon delta and interferon gamma during the peri-implantation period of pregnancy, but there is no evidence that they are involved in pregnancy recognition signaling. Rather, pig conceptuses secrete abundant amounts of estrogens between Days 11 to 15 of pregnancy required for maternal recognition of pregnancy. Estrogen, likely in concert with prolactin, prevents secretion of PGF into the uterine venous drainage (endocrine secretion), but maintains secretion of PGF into the uterine lumen (exocrine secretion) where it is metabolized to a form that is not luteolytic. Since PGF is sequestered within the uterine lumen and unavailable to induce luteolysis, functional CL are maintained for production of progesterone. In addition to effects of chorionic gonadotrophin, IFNT and estrogens to signal pregnancy recognition, these hormones act on uterine epithelia to enhance expression of genes critical for growth and development of the conceptus.  相似文献   

19.
A 19-year-old Quarter Horse mare was evaluated because of bloody vaginal discharge that was apparent immediately following breeding. On transrectal ultrasonography, it was evident that the uterus was filled with fluid containing echogenic particles; linear hyperechoic structures were also visible. Endoscopy was performed, which revealed a number of bones adhered to the cranial wall and floor of the right uterine horn as well as purulent fluid in both uterine horns. Bacterial endometritis and fetal maceration were diagnosed. The mare was treated with antibiotics, and the fetal bones were manually removed from the uterus. Fetal maceration with intrauterine retention of bones is rare in mares. Use of hysteroscopy supplements ultrasonography in the diagnosis of uncommon conditions of the uterus. Macerated bones may be adhered to the endometrium, thereby requiring manual removal.  相似文献   

20.
On d 7 to 10 postmating, first-litter sows were fed either a control diet or a diet containing zearalenone (ZEN; 1 mg/kg body weight). Surgery was performed on either d 9, 11 or 13 postmating to collect blastocysts and uterine flushings. The rostral and caudal portion of each uterine horn was flushed with phosphate buffered saline, and the blastocysts were separated from the recovered solution. Uterine flushings were analyzed for total Ca, Mg, Zn, estradiol-17 beta (E2 17 beta) and progesterone (P4). Administration of ZEN did not affect the number of blastocysts recovered or the position of embryos within the uterus on d 9 or 11. Blastocysts recovered on d 13 were filamentous and could not be enumerated. Total Ca in uterine flushings of control sows was higher (P less than .001) on d 11 than on d 9 or 13, but intrauterine Ca of ZEN-treated sows did not vary by sampling day (P greater than .05) and was lower (P = .01) than that of controls on d 11. Total intrauterine Mg of ZEN sows was greater (P = .002) than of control sows on d 11 and 13, and total intrauterine Zn of ZEN sows was greater than that in control sows on d 13. There were no differences in total intrauterine P4 or E2 17 beta among ZEN-treated and control sows on d 9, 11 or 13 postmating. Serum concentrations of 13, 14-dihydro-15-ketoprostaglandin F2 alpha (PGFM) increased from d 9 to 13 in control and ZEN-treated sows, but there were no differences between treatment groups.(ABSTRACT TRUNCATED AT 250 WORDS)  相似文献   

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