Induction of parturition in the sow with a prostaglandin analogue (I.C.I. 80996)

Summary Parturition was induced in 112 gilts and sows on day 111, 112, and 113 of gestation by means of a single intramuscular injection of 175 mcg of a prostaglandin F2α analogue (Cloprostenol, I.C.I. 80996). No side effects were detected immediately after injection and the course of the induced parturition was normal. The interval between injection and parturition was approximately 28 hours. Induction of parturition on day 113 resulted in a significant shortening of this interval as compared with day 111 and 112. The average weights of the piglets at birth and at 5 weeks were within the normal range. The percentage of stillbirths and the loss of piglets up to weaning did not differ significantly between control and experimental groups. The practical applications of induction of parturition are discussed.     

Incidence and Prevention of Early Parturition in Sows

A retrospective study, based on 60 990 farrowing records from 35 commercial herds, was performed to determine the incidence of early parturition (<114d) and to investigate the relationship between early parturition and total number of piglets born, number of piglets born alive and percentage of stillborn piglets per litter. The mean gestation length was 115.4 ± 1.62d, and early parturition occurred in 10% of all farrowing records. Sows with early parturition had significantly more stillborn piglets and a larger litter size compared to sows with a normal gestation length (114–117d). Sows with a gestation length <114d were 1.2 times (95% CI: 1.19–1.21; p < 0.001) more likely to have an early parturition at the subsequent parity. A second study was performed in four herds (n = 329) to investigate the efficacy of altrenogest administration on 110–112d (T112) or 111–113d (T113) of gestation for preventing early parturition and to investigate the effect of this treatment on the reproductive performance of sows. The interval between the last altrenogest treatment and the onset of parturition was 3.3 ± 1.32 (T112) or 2.0 ± 0.89 (T113) days. The gestation length of sows of the altrenogest group (T112 + T113) (115.3 ± 1.23d) was significantly longer compared to gestation length of the non‐treated sows (114.7 ± 1.69d) (p < 0.01). Altrenogest treatment had no negative effect on the reproductive performances of the sows. In conclusion, the administration of altrenogest in late gestation is an effective and safe method to prevent early parturition and can counteract the reproductive losses because of premature farrowing, which may occur in a substantial part of the farrowing events.     

Control of the time of parturition in sows with prostaglandin F2alpha.

Pregnant gilts and sows were given a single intramuscular injection of from 5-10 mg of prostaglandin F2alpha-tromethamine salt (dependent on liveweight) on day 111, 112 or 113 of pregnancy (first day of estrus = day 0) to induce parturition. When injected on day 111, 44% of the pigs farrowed within 40 hours compared with 93% injected on days 112 or 113. The mean time to the induced parturition was 27.3 +/- 4.7 hours. Signs of discomfort were observed during the first hour posttreatment but there were no apparent effects on lactation or on the mothering ability of the dams after farrowing.     

Control of parturition in swine. 2. Study results of parturition synchronization in swine with the prostaglandin analog cloprostenol (I.C.I. 80.996: Estrumate)

Premature parturition was induced in 115 of 121 sows (95%) that had been given injections of 150 microgram or 200 microgram of "Estrumate", a prostaglandin analogues, on the 112th and 113th days of gestation. The average time that elapsed between injection and parturition of those 115 animals was 27.2 +/- 7.7 hours, with no difference being observed between gilts, on the one hand, and old sows, on the other. The time of gestation of the treated animals was shortened with significance from 114.6 +/- 1.6 days for the controls to 113.2 +/- 0.4 days. The average duration of parturition proper was 3.7 +/- 2.2 hours, the average litter being 11.2 +/- 3.3 piglets. The total number of piglets born was 1,320, with stillbirths accounting for 4.17%. The average weight at birth, 1,330 +/- 210 g, and the weight at weaning did not differ from weight figures recorded from the controls. The courses of parturition and puerperium were in agreement with normal biological standards. The sows treated were tested for their blood counts close to full term and for their endometrial histomorphology after weaning, with no side effects of "Estrumate" treatment being established. The behaviours of progesterone, 17-beta oestradiol, and cortisol in serum of "Estrumate"-treated sows were investigated, and congruence was established between spontaneous and prostaglandin-induced parturitions, which was in agreement with international literature. The conclusion is that 150 micrograms of 'Estrumate", administered to swine, after the 11th day of gestation has very good labour-inducing effects and ensures normal physiological parturition and piglet development.     

Induced Parturition in Swine Herds

Intramuscular injections of various levels of prostaglandin F(2alpha) were administered to 116 pregnant swine in three commercial herds and the University research unit on Day 111, 112 or 113 of gestation. Sixty-three percent of the treated animals farrowed during the working day immediately following treatment. The parturition time, birth weight, litter size, number of piglets weaned, growth of the piglets to weaning and subsequent rebreeding of the dams were comparable with the expected performance in the herds. The results indicated that prostaglandin F(2alpha) in doses ranging from 5 to 12.5 mg per animal were effective for induction of parturition in a substantial proportion of the treated animals. Successful induction of parturition could reduce the farrowing interval for batches, allow more supervision of farrowing, facilitate transfer of piglets from large to small litters and generally increase efficiency in the farrowing unit. This technique could have practical application in intensive swine production units.     

Farrowing induction induces transient alterations in prolactin concentrations and colostrum composition in primiparous sows

Hormonal changes involved in the farrowing process partly control the initiation of lactation. Inducing farrowing by injection of PG may alter the normal prepartum hormonal cascade. The aim of the study was to investigate the consequences of farrowing induction on colostrum yield and composition, as well as newborn piglet growth. Gilts were treated with 2 mg of alfaprostol on d 113 of gestation (induced farrowing, IF, n = 9) or were injected with 1 mL of a saline solution (natural farrowing, NF, n = 11). Colostrum production was estimated during 24 h, starting at the onset of parturition, based on piglet BW gains. Colostrum samples were collected during the 36 h after the onset of parturition. Blood samples were collected from sows as of d 112 of pregnancy until d 2 postpartum (d 0 being the day of parturition). Piglet blood samples were obtained at birth, on d 1, and on d 21. Litter size and litter weight at birth did not differ between groups (P > 0.10). Farrowing induction did not influence (P > 0.10) colostrum yield (3.96 ± 0.20 kg) or piglet BW gain during d 1 postpartum (116 ± 8 g). At the onset of farrowing (T0), lactose content in colostrum was greater in IF sows than in NF sows (P < 0.05), whereas colostrum ash and protein contents were less (P < 0.05) in IF sows. Concentrations of IgG in colostrum were similar in both groups of sows, whereas concentrations of IgA at T0 were less in IF than in NF sows (P < 0.01). Overall, endocrine changes in blood from d -2 until d 2 (cortisol, prolactin, progesterone, and estradiol-17β) were not altered by farrowing induction (P > 0.10), but 1 h after the injection of alfaprostol, IF sows had greater circulating concentrations of prolactin (P < 0.01) and cortisol (P < 0.10) than NF sows. The greater concentration of lactose in colostrum from IF sows could be attributed to this transient increase in prolactin and cortisol. At birth, concentrations of white blood cells were less in piglets born from IF sows (P < 0.01). On d 1 and 21, piglets from IF sows had similar IgG concentrations in plasma to piglets from NF sows (P > 0.1). In conclusion, farrowing induction at 113 d of pregnancy induced transient hormonal changes in sows and alterations in colostrum composition, without significantly affecting colostrum yield. It also modified some hematological variables of piglets at birth.     

Effect of dosage of cloprostenol on induction of farrowing and body temperature of sows

In an experiment involving 161 farrowings, cloprostenol was injected on day 112 or 113 of gestation at the recommended dosage (175 μg) or a lower dosage (125 μg). Cloprostenol treatment did not result in abnormally high body temperatures of sows at parturition. Farrowing began within 29 hours of injection in 94% and 88% of the sows treated with 175 μg and 125 μg cloprostenol respectively, as compared to 15% of saline-injected controls. The duration of farrowing and number stillborn were not affected by treatment. Sows farrowing within 19 hours of treatment tended to have a large number of piglets and a higher body temperature postpartum.     

Reproductive efficiency and incidence of MMA after controlled farrowing using a prostaglandin analogue, cloprostenol

In a herd of sows 106 sows having 4.3 litters on aver., were over a period of 10 weeks treated on Thursdays with 0.175 mg of cloprostenol on the 111th to 114th day of gestation; 93--95% of the sows treated on the 112th and 113th day farrowed within 33 hours after treatment, 73% after treatment on the 111th day (Table I); the mean period of gestation after treatment was 113.4 +/- 0.9 days. 8 sows that only farrowed 2--5 days after the treatment, had on 21 previous farrowings proved to have significantly longer mean periods of gestation, 115.6 days, than the 112 sows in the control group, having 3.6 litters on average, that farrowed in the same period and section of the piggery as the sows treated with cloprostenol. In total 32 weekend-farrowings occurred in the observation period including 7 farrowings after a period of gestation of 110--113 days, 6 cases of unsuccessfully induced parturition and 19 farrowings on the 114th to 119th day that could have been programmed to occur on Fridays; the number of weekend-farrowings, which for this herd in connection with the weaning procedure normally accounted for about 40--45% of farrowings, could thus be reduced to 7% of farrowings (Table II). Cloprostenol treatment on the 111th day resulting in farrowing on the 112th day leads to a significantly higher rate of piglet mortality after 3 weeks compared with the results after farrowing for control sows that farrowed on the 112th day (Table III); this category of control sows had on previous farrowings proved to have a significantly shorter mean period of gestation, 112.7 days, than that of the sows in the cloprostenol group farrowing on the 112th day which had been 114.3 days on previous farrowings. Farrowing and weaning results after induced parturition resulting in farrowing on the 113th to 115th day showed no significant differences from the results for control sows farrowing spontaneously on the 112th to 115th day of gestation. The incidence of MMA (Table II) was not influenced by the cloprostenol treatment, nor by the number of litters, the length of the period of gestation, or by the piling of farrowings on Fridays.     

Effects of oral caffeine administration to sows with induced parturition on hypoxia in piglets

To counteract the effects of perinatal hypoxia in piglets, the oral administration of caffeine to sows with induced parturition was evaluated. On day 113 of gestation 9 sows received 27 mg/kg body weight (BW) of caffeine mixed with 200 g of standard diet. The same amount of feed without the addition of caffeine was administered to 9 control sows. Additionally, on day 113 of gestation, all sows were treated by two injections in the perianal area of 1 mg of alfaprostol (at 8:00 am and 14:00 pm), and on the morning of farrowing by 14 IU of oxytocin in the perianal area. Caffeine did not affect BW of piglets and size of litters; however piglets from treated sows showed a higher capacity to adapt to extra-uterine life. Particularly, they showed a greater thermoregulatory ability (P<0.001) and a higher percentage of viability score≥7 compared to piglets from control sows (92% vs. 75%, respectively; P=0.030). Caffeine furthermore reduced the frequency of high serum biopterin values (>80 nmol/L) in piglets born from treated sows (P=0.001). In conclusion, the caffeine orally administered to sows with induced parturition showed a protective effect on the consequences of neonatal hypoxia in tissue ischemia–reperfusion injury in piglets.     

Attempts to influence birth in swine with dexamethasone. 2. Effect of DXMS on adrenal mass and cell nuclear volume of the fascicular zone in piglets

The adrenal weights of spontaneously born piglets, immediately after parturition, were significantly higher than those of piglets from sows in whom parturition had been induced by DXMS. The differences between mean values went down with DXMS treatment started later in advanced pregnancy. Mean absolute and relative adrenal weights of the DXMS groups came closer to those of the untreated controls on the tenth day of piglet age. Cell nucleus volumes of the zona fasciculata were normal in all groups and did not reveal any influence of DXMS treatment in any of the newborn piglets. The mean values were 89.9 micron3 in the control group and 87.6 micron3 in experimental group V (75 mg DXMS per animal and die on 109th through 111th days of pregnancy).     

氯前列烯醇诱导母猪同步分娩的效果

选择 2～ 4胎龄施格母猪 1 32头 ,分为 2组。对照组 ( 6 5头 )不做任何处理 ,试验组 ( 6 7头 )又分妊娠 1 1 2d组 ( 34头 )、1 1 3d组 ( 33头 )。用氯前列烯醇 ( 0 .1 g/L)分 0 .5m L/头、1 m L/头 2个剂量组分别处理上述各试验组母猪 ,观察母猪的分娩情况。结果 ,处理至分娩开始的间隔 ,1 1 2 d组为 2 8.72 h,1 1 3d组为 2 3.34 h,2组差异极显著 ( P<0 .0 1 ) ;分娩产程 ,1 1 2 d组为 3.0 8h比对照组长 4 .2 min,1 1 3d组为 2 .31 h比对照组短4 2 min,无显著性差异 ( P>0 .0 5) ;而白天分娩率经χ2 检验有显著性差异 ,1 1 2 d、1 1 3d组分别有 6 1 .76 %和78.78%的母猪在白天分娩 ,而对照组仅为 4 6 .1 5% ( P<0 .0 5)。1 1 2 d组、1 1 3d组母猪的生产成绩 ,死胎率分别为 2 .2 7%和 2 .0 8%比对照组低 1 .82 %、2 .0 1 % ( P<0 .0 5) ;初生窝重分别为 1 1 .56、1 0 .55kg,分别比对照组高 0 .0 8kg和低 0 .0 7kg( P>0 .0 5) ;2 0日龄窝重 ,1 1 2 d组平均为 33.56 kg比对照组低 1 .9kg,1 1 3d组为2 9.30 kg比对照组高 1 .77kg( P>0 .0 5) ;断奶个体重 ,1 1 2 d组平均为 8.1 4 kg比对照组低 0 .2 7kg,1 1 3d组平均为 9.2 7kg比对照组高 0 .85kg( P>0 .0 5)。结果表明 ,氯前列烯醇能有效控制母猪分娩时间集     

Effect of altrenogest and Lutalyse on parturition control, plasma progesterone, unconjugated estrogen and 13,14-dihydro-15-keto-prostaglandin F2 alpha in sows

To investigate control of parturition time, 154 sows farrowing 220 litters at three locations were treated with altrenogest and Lutalyse (PG). The four treatment groups were: 1) no treatment (control group); 2) an im injection of 15 mg of PG at 1000 on d 111, 112 or 113 of gestation (d 0 = first day of estrus and gestation); 3) altrenogest (20 mg X sow-1 X d-1) fed twice daily for 4 d starting on d 109, 110 or 111; and 4) altrenogest and an injection of PG at 1000 on the day after the last feeding of altrenogest. Control sows at the University of Delaware (UD), University of Maryland (UM) and USDA, Beltsville Agricultural Research Center (BARC) had mean gestation lengths of 113.5, 114.2 and 115.7 d and live pigs/litter were 10.5, 11.0 and 7.4, respectively. Altrenogest started by d 110 prevented unscheduled early farrowing and increased (P less than .01) gestation length by 1.7 and 1.1 d, respectively, at UD and UM, but had not effect at BARC. The time from PG to parturition was 24.3, 22.6 and 34.4 h, respectively, at UD, UM and BARC. More sows at UD and UM farrowed between 0700 and 1700 on the expected day of parturition after injection of PG (59.3%) than with no PG (20.7%; P less than .05). The high incidence of small litters (less than six pigs) from sows inseminated with frozen semen at BARC resulted in negative correlations of live pigs/litter with gestation length (r = -.533, P = .0001) and with time from PG injection to birth of first pig (r = -.425, P = .017); these correlations were not significant at UD and UM where only natural service was used.(ABSTRACT TRUNCATED AT 250 WORDS)     

Milk Production in Sows after Spontaneous Delivery and after Delivery Induced by PGF2α Analogs

In this study the amount of milk produced during the first week of lactation was compared in sows with induced parturition and sows which delivered spontaneously (with special attention to sows showing MMA symptoms). Fifteen sows (L X LW) were used from a pig farm in which MMA was seen in 20 to 25% of all farrowings. The animals were divided into three groups of 5 each. Group A and B were treated with two different PGF ₂ α analogs (2 mg of alfaprostol or 0.45 mg of tiaprost) on 111 day of pregnancy, and group C (control) with 2 ml of saline solution. Treatment with PGF analogs induced parturitions 24 to 30 h later, controls delivered spontaneously on day 114. Litters were equalized to nine piglets per sow. The milk yield of each sow was calculate using the method of weighing piglets before and after each suckling. Piglets were allowed to suckle 12 times in the first 24 h after parturition, then 8 or 9 times in the next 24 h and from 48 h onwards 8 times during 24 h, until the end of the 7 day observation period. During the first day after parturition the control group appeared to produce slightly more milk than groups A and B whereas from 24 to 48 h, milk yields decreased in all animals. From 48 onwards milk production increased in all groups. Between 72–96 h, two sows of the control group showed symptoms of MMA and their piglets developed diarrhea. Microbiological analysis confirmed the presence of haemolytic Streptococci. The lactation curves of treated and untreated sows with no signs of MMA were very similar; the pattern was more erratic in sows with MMA. The total milk yields during the first week of lactation did not differ between groups; there were no significative difference in the weight gain of the piglets in groups A, B and C. The difference recorded in milk yield and release patterns between sows with or without MMA opens new aspects with regard to the aetiology of a syndrome that not only involves the sows health, but produces intestinals disease in their piglets.     

The induction of parturition in sows using prostaglandin F2auml;

Intramuscular injections (10mg) of prostaglandin F2ä were administered to 19 pregnant sows in one herd on either the 112th or 113th day of gestation and a similar number of untreated sows served as controls. Induced sows for up to 6h after injection generally showed/more walking, drinking defaceating and postural changes. Over the last 20h prepartum they spent more time lying and urinated more frequently. Mean interval from injection to onset of parturition in treated sows was 24.5h and 16 of them commenced farrowing during the working day, compared with 6 in the control group. Induction of parturition did not influence litter size at birth, piglet bodyweights at birth or 14 days of age, the incidence of the mastitis, metrititis agalactae syndrome, re-breeding interval of the sow or size of the subsequent litter at birth. Farrowing time was significantly longer (6.48h v 4.08h) for treated sows and litter pre-weaning mortality was higher but not significantly so. Most piglet deaths in each group resulted from overlaying or starvation but mortality from anaemia and septicaemia occurred only in the treated group. It is considered that the technique could have practical application on well-managed intensive pig units.     

Altrenogest Treatment Associated with a Farrowing Induction Protocol to Avoid Early Parturition in Sows

This study investigated the effect of altrenogest treatment on the farrowing development of sows, and birth weight (BW) and piglet survival until the third day of life. Three control groups were used: (i) sows that farrowed spontaneously before 114 day of gestation (CONT <114); (ii) sows that spontaneously farrowed at ≥114 day of gestation (CONT ≥114); (iii) sows that farrowed at ≥114 day with cloprostenol treatment (CONTCLOPR). Other sows were treated with altrenogest (Regumate^®) for 3 days (days 111, 112 and 113 of gestation): one group gave birth spontaneously (ALT) and the other group received altrenogest until day 113 and cloprostenol on day 114 (ALTCLOPR). There were no differences (p > 0.05) in farrowing duration, BW, coefficient of variation (CV) of BW, stillborn piglets, mummified foetuses, percentage of light piglets and survival until Day 3 between sows with and without cloprostenol treatment, in both control (CONT ≥114 vs CONTCLOPR) and altrenogest‐treated sows (ALT vs ALTCLOPR). Further comparisons were performed taking into account three groups: sows with early delivery (CONT <114 – farrowing before 114 days of gestation; n = 56), sows with longer gestation (CONT ≥114 – with and without cloprostenol treatment sows; n = 103) and ALT sows (with and without cloprostenol treatment; n = 105). Gestation length of CONT ≥114 and ALT sows was similar (p > 0.05), but higher than in CONT <114 sows. There were no differences (p > 0.05) between groups in farrowing duration, CV of BW, and percentages of stillborn piglets and mummified foetuses. Sows of CONT <114 group had a larger litter size and a lower BW than sows of the other two groups (p < 0.05). Sows of CONT <114 group had a higher percentage of lighter piglets and a lower piglet survival rate (p < 0.05) than ALT sows. In conclusion, altrenogest treatment proved to be an efficient method to avoid early parturition in 3–5 parity sows resulting in heavier piglets at birth.     

Control of swine parturition. 1. Results of clinical, histological and hematological studies of parturition induction in swine using prostaglandin F2 alpha

Parturition was induced to 23 sows on the 112th day of pregnancy by intramuscular injection of 7.5 mg PGF2 alpha (Dinoprost-Upjohn Co.). Onset of parturition was achieved within 27 hours and 52 minutes +/- four hours and 54 minutes in 21 animals (91.3 per cent). Average litter size was 11.33 piglets, with parturition time per litter having been five hours and 45 minutes +/- two hours and 39 minutes. Stillbirths accounted for 6.3 per cent. The average birth weight, 1.245 g +/- 264 g did not differ with significance from that of the controls. The physiological process accompanying parturition is described in greater detail. Unobstructed re-intergration with further reproduction of animals which had received PGF2 alpha treatment is established with hard evidence on the basis of clinical examination of oestrus, ovulation, conception, and farrowing rates as well as by histological examination of the endometrium. Alterations in the blood state recorded from animals with PGF2 alpha treatment close to full term were identical with those recorded from untreated animals.     

The induction of parturition in sows using prostaglandin F2alpha

Intramuscular injections (10 mg) of prostaglandin F2alpha were administered to 19 pregnant sows in one herd on either the 112th or 113th day of gestation and a similar number of untreated sows served as controls. Induced sows for up to 6h after injection generally showed more walking, drinking defaceating and postural changes. Over the last 20 h prepartum they spent more time lying and urinated more frequently. Mean interval from injection to onset of parturition in treated sows was 24.5 h and 16 of them commenced farrowing during the working day, compared with 6 in the control group. Induction of parturition did not influence litter size at birth, piglet body-weights at birth or 14 days of age, the incidence of the mastitis, metrititis agalactae syndrome, re-breeding interval of the sow or size of the subsequent litter at birth. Farrowing time was significantly longer (6.48 h v 4.08 h) for treated sows and litter pre-weaning mortality was higher but not significantly so. Most piglet deaths in each group resulted from overlaying or starvation but mortality from anaemia and septicaemia occurred only in the treated group. It is considered that the technique could have practical application on well-managed intensive pig units.     

15-ketodihydro-PGF2 alpha, progesterone and cortisol profiles in heifers after induction of parturition by injection of dexamethasone.

In order to study rapid changes in 15-ketodihydro-PGF2 alpha, cortisol and progesterone in the period preceding parturition in cattle, pre-term parturition was induced in 4 late pregnant heifers. Parturitions were induced by 2 intramuscular injections of 20 mg dexamethasone with a 24-h interval. The first injection was made on days 254, 258, 264 and 265 in gestation, respectively. Twenty-four h before the first injection an intravenous polyurethane cannula was inserted. Blood samples were collected at least every hour until 12 h after parturition and during the second stage of labour at least 6 times per hour. Plasma was analysed for 15-ketodihydro-PGF2 alpha and progesterone by radioimmunoassays, and for cortisol by an ELISA. The average time from injection to parturition was 7.7 (6.6-8.9) days (mean (range)). Two of the heifers had retained foetal membranes (RFM). At the start of the experiment the levels of PGF2 alpha metabolite were low (< 300 pmol/L) and increased slowly to levels between 1000 and 2000 pmol/L at one day before parturition. During the last day, however, the levels increased rapidly and the highest levels (> 10,000 pmol/L) were reached at the time of delivery. No pulsatile release was seen. Immediately after foetal expulsion the PG-metabolite levels decreased rapidly in all animals. In the 2 animals with RFM, however, this decline ceased within a few h. The PG-metabolite levels in these animals then started to increase and reached levels as high as during parturition. Luteolysis occurred between 1.6 and 0.4 days before parturition in all animals. The cortisol profile showed a distinct peak at the time of parturition in the RFM heifers. This peak was absent in the non-RFM heifers. This study shows that the PGF2 alpha release at prepartal luteolysis and parturition is not pulsatile in cattle and that cortisol profiles in heifers with retained foetal membranes might differ from the profiles in non-RFM heifers at the time of parturition.     

诱导妊娠母猪白天分娩及其机理的研究

用氯前列烯醇对妊娠后期母猪作一次性肌注，从注射前至分娩开始，以１２小时为间隔采血，然后用放射免疫法分析血样，发现注射前血浆孕酮含量较高（１５．９５ｎｇ／ｍｌ），以后逐渐显著下降，分娩时降低到最低（５．３９ｎｇ／ｍｌ）。这说明外源性氯前列烯醇对母猪分娩前妊娠黄体有溶解作用，可导致母猪分娩提前发动。实验发现，在妊娠期１１０天、１１１天和１１２天处理母猪的白天分娩率分３１１为９０％（１８／２０）、８８．２４％（１５／１７）和７５％（１２／１６）；不同处理剂量（０．０５ｍｇ。０．１ｍｇ、０．２ｍｇ）的白天分娩率分别为８６．９６％（２０／２３）、８７．５％（１４／１６）和７８．５７％（１１／１４）；实验组的平均白天分娩率（８４．９１％，４５／５３）显著高于对照组（４５．６５％，２１／４６）；处理至分娩间隔时间平均为２４小时２４分钟。     

前列腺素诱导母猪分娩时的内分泌状态

选用５头妊娠后期母猪,于妊娠１１１ｄ上午９∶００肌肉注射氯前列烯醇（ＰＧ）０．２０ｍｇ。５头母猪皆于次日白天分娩。从注射前至分娩结束,在整个诱导过程中多次采血,监测了血清中孕酮（Ｐ４）、硫酸雌酮（Ｅ１Ｓ）、催乳素（ＰＲＬ）和皮质醇（ｃｏｒｔｉｓｏｌ）４种激素浓度的变化。结果表明,诱导分娩过程中各种激素的变化和自然分娩基本一样。这就解释了用国产前列腺素诱导母猪分娩,只要处理时间合适（妊娠１１１ｄ或１１２ｄ）,就会有良好效果,不会产生不良副作用。