Early disruption of pregnancy as a manifestation of seasonal infertility in pigs

All gilts and sows in production from which the detailed production information was available in a 160-sow unit were included to the study. In winter-spring, there were complete data available from 47 animals and in summer-autumn from 64 animals. The farm had a consistent history of the seasonally reduced farrowing rate in summer-autumn. Success of inseminations was monitored during a 4-month breeding period in winter-spring and in summer-autumn. Each animal was bled twice a week for 6 weeks starting a day before insemination and the blood samples were assayed to determine serum progesterone concentration. The blood samples were also assayed for cortisol to detect any acute infectious response. Starting on day 18, animals were pregnancy tested by transcutaneous real time ultrasound twice a week. In winter-spring, the farrowing rate was 72% (58 inseminations, 1.2 inseminations/sow) and in summer-autumn 63% (81 inseminations, 1.3 inseminations/sow). In winter-spring, there was only one detected case of early disruption of pregnancy (EDP), whereas nine such cases were recognised in summer-autumn. Five out of those nine animals returned to oestrus with a mean insemination to oestrus interval of 25.8+/-1.6 days. One sow returned to oestrus 35 days after insemination and three sows did not return to oestrus within 45 days. However, two of these sows had progesterone profiles that indicated an undetected oestrus around day 25. In those nine animals, no acute phase infectious response as indicated by a rise in serum cortisol was evident. Serum progesterone concentrations in the animals eventually loosing the pregnancy tended to be lower on day 13 (no significant difference) and were significantly lower on day 20 when compared with animals remaining pregnant. There was no difference in serum progesterone levels of pregnant animals between winter-spring and summer-autumn. Litter size was not affected by the season. The weaning to oestrus interval tended to be longer in summer-autumn. This study showed that the seasonally decreased farrowing rate is partly caused by EDP. The lowered progesterone concentrations in summer-autumn were demonstrable only in "problem animals".     

Effect of feeding level on progesterone concentration in early pregnant multiparous sows

The effect of three feeding regimens on progesterone level was tested during early pregnancy in multiparous sows. A total of eighteen sows in their eighth parity (8.1 +/- 2.8, mean +/- S.D.) were used. During lactation the sows were fed to appetite and after weaning they received 4 kg (52 MJ) a commercial feed per day. Following ovulation, sows were allocated to one of three treatment groups and fed 2 kg/day (low feeding, LLL) or 4 kg/day (high feeding, HHH) throughout the trial or 2 kg/day for 11 days, 4 kg/day for 10 days, and 2 kg/day for the remaining days of the study (modified feeding, LHL). Blood for progesterone and cortisol analyses was collected daily throughout the study, and for luteinizing hormone (LH) assay for 12 h at 15 min intervals on days 14 and 21 of pregnancy. An adrenocorticotropic hormone (ACTH) challenge test was performed on all sows day 28 of pregnancy. Dietary treatment did not significantly affect hormonal parameters. However, progesterone concentration tended to be lower (P = 0.08) in the HHH group than in the LLL group. In the LHL group venous progesterone concentration seemed to fluctuate. No effects of feeding were observed on progesterone concentration in allantoic fluid on day 35 of pregnancy. Venous cortisol level was significantly higher (P < 0.05) during proestrus and oestrus in all groups and there was no significant difference between groups in response to ACTH challenge. The mean amplitude of LH pulses decreased significantly (P < 0.01) from days 14 to 21 of pregnancy in all groups. In addition, an interaction was found between feeding level and baseline LH concentration and also between feeding level and mean LH concentration. Embryonic recovery was highest in the LLL (69%), lowest in the HHH (45%) and moderate in the LHL (55%) group. Neither high feeding nor modified feeding provided any benefits for reproductive performance in multiparous sows. A low feeding regimen thus appears optimal for multiparous sows in early pregnancy at least with the management regime described.     

Prospects and limitations of the rosette inhibition test to detect activity of early pregnancy factor in the pig

After preincubation of lymphocytes in serum of non-pregnant pigs and using a standard anti-pig-lymphocyte serum the upper limit of the 99.9% confidence interval of rosette inhibition titres (RIT) for pig serum was calculated to be 11.4 and all titres greater than 12 were defined as a proof of early pregnancy factor (EPF)-activity. The reproducibility of the RITs with serum samples of pregnant pigs was considered satisfactory (interassay coefficient of variation 23.8%), whereas their reproducibility was considered good with sera taken from non-pregnant animals (interassay coefficient of variation 6.5%). Problems of the test were particularly evident due to the absence of increased RITs after previous incubation of lymphocytes in serum of pregnant pigs. Therefore, all EPF-negative samples were reanalyzed up to two times; pregnancy was then correctly diagnosed for 88.7% of sows. There were 8.6% false positive results (N = 70) and 12.2% false negative results (N = 205). During the first half of pregnancy RITs displayed periodic fluctuations which resembled the physiological cycle interval of the pig. Between Weeks 5 and 9 of pregnancy greater numbers of EPF-negative sows were detected. Subsequently, a continuous increase of mean RITs occurred, which then declined gradually from Day 80 of pregnancy. Similar changes were observed for progesterone values in the dialysed serum samples. However, highest progesterone concentrations always followed elevated RITs with a delay of 1.5-4 days. A subthreshold cyclicity of ovarian and luteal function probably persists despite pregnancy.     

Pregnancy diagnosis in swine by palpation and by amplitude-depth ultrasound scanning

The relative accuracy of two pregnancy testing methods for swine were compared in a field study. The procedures used were manual palpation and amplitude-depth ultrasonic scanning. A total of 369 sows were examined by both methods. Seven additional gilts were examined by ultrasound only and 46 sows by palpation per rectum only. The number of correct positive and negative diagnoses made by both methods were calculated, and determination of accuracy as well as comparison between the tests were made on this basis. The relative accuracy was 97.6% for the manual method and 96.8% for the ultrasound method. Both tests had a high sensitivity, 99.2 and 98.9%, respectively. The ability of the tests to detect the non-pregnant animals was not as high, which is reflected by a lower specificity. No significant differences were noted between the two methods. A lower specificity and a lower negative predictive value were provided by ultrasound scanning as compared with those acquired by manual palpation. Both procedures were considered to be quick and convenient to perform. It was concluded that in spite of the new pregnancy testing methods introduced in the swine industry, manual palpation remains the most practical in terms of its accuracy, ease, and the minimal requirement for equipment. In gilts, palpation is unsuitable and ultrasonography currently remains the best choice for the diagnosis of pregnancy.     

Use of milk progesterone enzyme immunoassay for early pregnancy diagnosis in cows

An enzyme immunoassay using beta-galactosidase as the tracer was applied to determine milk progesterone level in cows. The novel method was reliable and practicable and required only a spectrophotometer and a centrifuge as major equipment. The milk progesterone enzyme immunoassay successfully diagnosed early pregnancy in cows. Milk samples were collected from 268 Holstein-Friesian cows in commercial dairy herds on 20, 21 or 22 days(usually 21 days) after insemination. Progesterone level in skim milk higher than 1.0 ng/ml indi-cated pregnancy. Pregnancy was confirmed by rectal palpation on 60 to 120 days after insemination. The accuracy of the milk progesterone test was 60.0 % (132 220 ) for a positive diagnosis and 100 % (48 48 ) for a negative result. A high incidence of embryonic death, 27.9 % (51 183 ), may have reduced accuracy for a positive test result. The enzyme immunoassay may be an alternative to radioimmunoassay in milk progesterone analysis for pregnancy diagnosis.     

Milk progesterone measurement in dairy cows: Correlation with estrus and pregnancy determination

Progesterone levels in fore milk, determined by a highly specific radioimmunoassay, were compared for the assessment of estrus by a veteran herdsman and an experienced inseminator, in cows presented for insemination. In addition, an examination was made of the relative accuracy of using milk progesterone levels for the determination of pregnancy at 24, 40 and 44 days after insemination, as compared with rectal palpation at 45–50 days post-breeding.Fat-free fore milk progesterone levels were similar to jugular plasma levels at 24 days post-insemination and reached roughly 60% of the level of unextracted fore milk at this time. Accuracy of estrus diagnosis by herdsman, inseminator and milk progesterone level was 84%, 93% and 96%, respectively. For pregnancy diagnosis, milk progesterone determination in 85 cows showed 78% accuracy in predicting pregnancy and 100% accuracy in predicting non-pregnancy. At 40 days post-insemination false positives dropped to 10% and at 44 days only 7% of the cows were incorrectly diagnosed as pregnant. The false positives in this study were largely due to embryonic mortality as reflected by abnormal intervals of return to estrus. Two milk progesterone determinations, at 24 and either 40 or 44 days post-insemination ensure maximum reliability for early pregnancy diagnosis.     

Bovine milk progesterone concentration as a method of early diagnosis of pregnancy (author's transl)]

With the purpose of obtaining an early indicator of pregnancy in bovines, excretion levels of milk progesterone were determined by a simple radioimmunological method. In the pregnant group, progesterone concentration was significantly (p less than 0,001) greater than in non-pregnant ones. In some cases (20-25%) there was no difference in values, resulting a method efficiency of 75-80%. Milk must be processed a few hours after collection since a decrease in progesterone values is observed within a few days. Easy obtention of this biological matherial, without special technical requirements as well as the simple dosification method make this test a practical index for establishing early diagnosis of pregnancy in bovines.     

Concentrations of progesterone in milk as a monitor of early pregnancy diagnosis in dairy cows

The objectives of the experiment were to evaluate the efficacy of using progesterone concentrations in milk and palpation per rectum on days 21 or 22 postbreeding to estimate pregnancy and evaluate management practices; and to investigate physiological occurrences leading to incorrect diagnosis of pregnancy when serial samples of milk were collected. Of particular interest were indications of early embyronic death and insemination of cows not in estrus. Milk samples were collected at the afternoon milking of days 0 or 1 (day 0 = day of estrus), 9 or 10, 21 or 22 and 27 or 28 following breeding in 200 lactating dairy cows. Tentative diagnosis of pregnancy was made based on concentrations of progesterone in milk on days 21 and 22 alone and on days 21 or 22 and 27 or 28. In addition all cows were palpated per rectum on days 21 or 22 postbreeding and a tentative pregnancy diagnosis was made. Pregnancy was confirmed by examination of the genital tract per rectum between 35 and 50 days after breeding. Values of 4 ng/ml or greater and/or the presence of a mature corpus luteum were considered positive signs of pregnancy. Progesterone in milk ranged from 0.1 to 18 ng/ml. On days 0 or 1, 9 or 10, 21 or 22 and 27 or 28 concentrations of progesterone in milk averaged 1.5 +/- 0.3, 11.1 +/- 0.5, 12.0 +/- 0.4 12.5 +/- 0.5 ng/ml for pregnant cows. Corresponding samples from nonpregnant cows averaged 1.2 +/- 0.2, 10.3 +/- 0.4, 3.0 +/- 0.4, 6.8 +/- 0.6 ng/ml, respectively. Ninety-six and 104 cows were classified as pregnant and nonpregnant on days 21 or 22 as compared to 78 and 118 cows diagnosed as pregnant and nonpregnant on days 21 or 22 and 27 or 28 combined. Pregnancy detection by progesterone in milk on days 21 or 22 with pregnancy determined via rectal palpation 35 to 50 days postbreeding was 77 and 100% accurate for positive and negative diagnosis, respectively. The percent agreement using progesterone in milk on days 21 or 22 and 27 or 28 combined was 95 and 100%, respectively, for positive and negative diagnosis. Diagnosis based on rectal palpation 21 or 22 days postbreeding was 63 92 (69%) and 76 88 (87%) for pregnant and nonpregnant cows, respectively. Ten of the 200 cows had progesterone concentratins in milk of > 4 ng/ml at the time of breeding. Six of these cows were pregnant from a previous insemination. The other four cows were nonpregnant and were inseminated during the luteal phase of the cycle. In conclusion, measurement of progesterone in milk is a useful tool in early detection of pregnant and nonpregnant cows and may be useful in detecting reproductive problems in a dairy herd. It will probably be most useful when used in combination with later pregnancy diagnosis per rectum .     

The accuracy of enzyme-linked immunosorbent assay and latex agglutination progesterone test for the validation of estrus and early pregnancy diagnosis in dairy cattle

The accuracy of the enzyme-linked immunosorbent assay (ELISA) and the latex agglutination (LA) on-farm progesterone kit for detecting estrus and diagnosing early pregnancy was investigated in this study. Italian Friesian dairy cows (n=82) from 6 dairy herds were used for the collection of foremilk samples at the time of breeding and at 19, 21, and 23 days post insemination. Pregnancy status was ascertained by uterine palpation per rectum 40 to 60 days post insemination. Progesterone levels were affected by herd, percentage of milk fat, and the day of testing x diagnosis interaction. Validation of estrus by qualitative on-farm tests was 74.6% (LA) and 100.0% (ELISA) accurate using 0.5 ng/ml of progesterone as the RIA estimate for estrus. The accuracy rate for early pregnancy diagnosis by RIA was 68.4 to 83.8% for day 19 and day 21, respectively, while the detection rate for nonpregnancy was 84.6 to 100% on day 19 and day 21, respectively, as compared with uterine palpation per rectum. The average accuracy rate for early pregnancy diagnosis ranged from 84.7 to 92.3% for the LA and ELISA tests, respectively; the nonpregnancy rate was correctly predicted 93.9% to 68.2% for the LA and ELISA tests, respectively.     

Supplemental progesterone during early pregnancy exerts divergent responses on embryonic characteristics in sows and gilts

Progesterone (P4) plays a key role in pregnancy establishment and maintenance; during early pregnancy, P4 stimulates the production and release of uterine secretions necessary for conceptus growth prior to implantation; therefore, exogenous P4 supplementation may improve embryo development. This study evaluated the effects of supplementation during early pregnancy with long-acting injectable progesterone or altrenogest on embryonic characteristics of sows and gilts. Thus, a total of 32 sows and 16 gilts were used. On day 6 of pregnancy sows and gilts were allocated to one of the following groups: non-supplemented; supplemented with 20 mg of altrenogest, orally, from days 6 to 12 of pregnancy; supplemented with 2.15 mg/kg of long-acting injectable progesterone on day 6 of pregnancy. Animals were killed on day 28 of pregnancy, and ovulation rate, embryo survival, embryo weight, crown-to-rump length, uterine glandular epithelium and endometrial vascularization were assessed. Treatments had no effect on pregnancy rate, embryo survival or endometrial vascular density (P > 0.05). Non-supplemented gilts presented larger and heavier embryos compared to gilts from supplemented groups (P < 0.05). Sows in the altrenogest group presented larger and heavier embryos compared to non-supplemented sows and sows supplemented with long-acting injectable progesterone. In conclusion, supplementation of sows and gilts with progestagen from day 6 of pregnancy can be used as a means to improve embryo survival without deleterious effects.     

Direct estimation of urine estrone conjugate for a rapid pregnancy diagnosis in sows

A rapid and direct radioimmunoassay of urine estrone conjugate (E₁C) was developed. Urine samples were taken from Large White sows by inserting sponges in the vagina which were expelled during micturition. Analysis of samples collected daily from 13 sows between 2 and 40 days after service showed that high urine E₁C levels occurred between day 20 and 30 after insemination in pregnant sows; maximum concentrations were observed on day 25 (79.4 ± 11.7 ng/ml, $\text{X}\text{± s.e.m.}$). In this period E₁C levels never exceeded 1 ng/ml in nonpregnant sows. A single urine sample was then taken from 84 sows, 25 days after insemination, to check the accuracy of E₁C estimation as a test for early pregnancy diagnosis. Seventy-six of the examined animals were correctly diagnosed, giving an overall accuracy of 90.4%. No relationship was found between litter size and urine E₁C levels.     

Direct ELISA for estrone measurement in the feces of sows: prospects for rapid, sow-side pregnancy diagnosis

Both free and conjugated fecal estrogens were surveyed in sows by means of RIA's after extraction and column chromatography. Six different RIA's were performed using the same fecal suspension. Based on differences in concentration in feces from 6 pregnant and 4 nonpregnant sows, estrone (E1) was selected for the development of a homologous, competitive ELISA for pregnancy diagnosis purposes. Polyclonal antibodies were raised against 6-keto-E1-carboxymethyloxime coupled to BSA. Biotinylated E1 was used as the competitive agent and was detected with a streptavidin-peroxidase conjugate. Tetramethylbenzidine was used as chromogen. Validation of this direct, easy to perform ELISA showed satisfactory specificity, accuracy, precision and sensitivity. Comparison of the assay with a validated RIA (including extraction and column chromatography) resulted in a linear regression equation of ELISA = 0.88 RIA - 0.72 (r = 0.95; n = 24 fecal samples). The E1 values in feces from 11 pregnant sows during the first 40 d of gestation compared with values from 10 nonpregnant sows showed significant differences between Days 23 and 35 of pregnancy (P < 0.05). The highly significant difference in E1 concentrations (P < 0.0012) between Days 27 and 30 in particular offers promise for pregnancy diagnosis.     

In vitro contractile activity of porcine myometrium during luteolysis and early pregnancy: effect of oxytocin and progesterone

The present study was undertaken to elucidate the role of OT in myometrial contractility in sows. Spontaneous and OT-stimulated contractions of the inner circular (CM) and outer longitudinal (LM) layers isolated from cyclic (Days 14-16) and early pregnant (Days 14-16) sows were examined in six cyclic and six pregnant sows. In addition, the role of P(4) in the modulation of OT-induced uterine contractions was investigated. The contractile activity of the LM and CM layers was recorded in a tissue chamber filled with Krebs-Ringer solution. Myometrial contractility was expressed as area under the contractility curve (AUC) and frequency of contractions. Myometrial longitudinal and circular muscles exhibited spontaneous contractility in sows during both luteolysis and early-pregnancy. The mean AUC was higher (p<0.05) in the LM layer compared to the CM layer in both cyclic and pregnant animals. In addition, pregnant sows were characterized by higher AUC in both LM and CM layers in comparison to cyclic sows. The CM layer was unresponsive to examined treatments. Oxytocin (1-3x10(-8) and 1-3x10(-7)M) increased the AUC and frequency of contractions of the LM layer in both examined animal groups, being more effective during luteolysis (p<0.001) than early pregnancy (p<0.01). Response of the LM layer to OT appeared to be clearly related to the initial spontaneous level of contractility. This response to OT was inhibited (p<0.05) in the presence of OT antagonist (10(-6)M). Moreover, in pregnant sows, OT-stimulated contractile activity of myometrium was inhibited (p<0.05) by P(4) (10(-5)M). In conclusion, OT receptors present in myometrial cells (especially in the LM layer) are involved in the regulation of contractile activity of porcine myometrium during luteolysis and early-pregnancy. In addition, progesterone appears to be involved in this regulation.     

The use of plasma progesterone profiles to predict the reproductive status of anestrous gilts and sows

A plasma progesterone profile obtained from three consecutive blood samples with an interval of 7 days was evaluated for usefulness as the basis for the diagnosis and treatment of anestrous gilts and sows. Four reproductive statuses were categorized based on the plasma progesterone levels and pathological examination of the reproductive organs from 25 gilts and 12 sows with anestrus. Category 1: fluctuating (at least one sample <2.5 ng/ml and one >10 ng/ml) with normal ovary; Category 2: sustained low (<2.5 ng/ml) with inactive ovary; Category 3: persistent high (>5 ng/ml) with normal sized or cystic corpora lutea; and Category 4: animals not included in the categories mentioned, such as pigs with luteinized cysts and follicular cysts. Using the plasma progesterone profiles and this categorization, the reproductive status of 54 gilts and 38 sows with anestrus was predicted. Hormonal treatments were performed with moderate to high success. Results from this study indicate that plasma progesterone profiles can be useful for the determination of estrus status, for the diagnosis of the causes of anestrus, and for the prediction of the next estrus for an appropriate hormonal treatment in anestrous gilts and sows.     

A solid-phase radioimmunoassay for progesterone and its application to pregnancy diagnosis in the cow

A solid-phase radioimmunoassay using antibody-coated tubes and ¹²⁵I-progesterone label was developed to provide an alternative to the conventional aqueous method of assaying progesterone in milk for early pregnancy diagnosis. The accuracy of diagnoses made using the solid-phase assay of progesterone in milk was assessed by comparison with diagnoses made using an aqueous assay of serum progesterone. Both methods agreed in the thirteen cows that were diagnosed. When “fat-free” milk was assayed by both aqueous (x) and solid-phase (y) methods, the progesterone values which resulted showed a high correlation (r = .94) and a linear relationship of y = 1.67x ? 0.68. Milk samples, in which the fat concentration ranged from 0.20 to 4.04%, were assayed by the solid-phase method and no relationship between milk fat and progesterone concentration was observed. Pregnancy diagnosis from solid-phase assay of milk samples collected on the day of breeding, 21 and 23 days following breeding was performed on 62 Holstein cattle. The accuracy of “non-pregnant” diagnoses was 95% to 100% and the accuracy of “pregnant” diagnoses was 80% if breeding day values were used and 72% if these values were excluded.The accuracy of this assay in diagnosing pregnancy was equal to that of previously published assays and provided the advantages of requiring less technical time and equipment. In addition, foremilk, composite or stripping samples can be accomodated in this assay since the estimates of progesterone are not affected by the concentration of milk fat.     

Serum progesterone levels as an index of pregnancy in buffaloes

Higher levels of serum progesterone on the 20th or 23rd day following impregnation were indicative of establishment of pregnancy in buffaloes. Buffaloes with serum progesterone levels of 1 ng/ml or more on these days were taken as pregnant. The accuracy of this test for diagnosing pregnancy was 75% on the 20th and 83.3% on the 23rd day after artificial insemination. The non-pregnancy diagnosis by this test was 100% accurate on both days of the test. Subclinical endometritis and/or early embryonic deaths seem to interfere with the exact diagnosis of pregnancy.     

Effects of progesterone antagonist, lilopristone (ZK 98.734), on induction of menstruation, inhibition of nidation, and termination of pregnancy in bonnet monkeys

The effects of a progesterone antagonist, lilopristone (ZK 98.734), on induction of menstruation, inhibition of implantation or pregnancy, and termination of early and mid-pregnancy were studied in bonnet monkeys. In the regularly menstruating animals, administration of lilopristone (25 mg/day, s.c.) during the mid-luteal phase (Days 20-22 of the menstrual cycle) induced menstruation within 2-4 days after the initiation of treatment. A premature drop in circulating progesterone levels was also observed. The luteolytic effect of lilopristone was prevented by exogenous treatment with hCG; however, the animals showed premature menstruation, in spite of high progesterone levels (above 4 ng/ml). Treatment around the time of implantation (between Days 8 and 12 after the mid-cycle peak in estradiol levels) in mated animals provided 100% pregnancy protection. Treatment of pregnant animals on Days 30-32 of the menstrual cycle, i.e. about Day 20 after the estradiol peak, induced abortion in 8 of 10 animals. A significant (p less than 0.05) decrease in serum progesterone levels was observed on Day 3 after the initiation of treatment. However, the decrease was slower (slope: -0.36, r: 0.96) compared to that observed in nonpregnant animals (slope: -0.72, r: 0.95). In the other two animals, pregnancy was not affected. However, when the treatment was delayed until about Day 50 after the estradiol peak, all four animals aborted. This study suggests that lilopristone is a progesterone antagonist with a potential to induce menstruation, inhibit nidation, and terminate pregnancy. The antifertility effects are mediated through blocking progesterone action at the endometrium as well as decreasing progesterone bioavailability, which appears to be due to its effects on gonadotropin release.     

Hormonal profiles and embryo survival of sows subjected to induced stress during days 13 and 14 of pregnancy

Group housing of sows during the mating and gestation period has become the overall common management practice in Sweden. Loose housing is probably less stressful for the animals because it allows them more opportunities to behave naturally, but mixing unfamiliar sows does create a stressful situation due to aggressive interactions, which can lead to food deprivation. The objective of the present study was to investigate and compare the effects of stress in form of food deprivation and ACTH administration at days 13 and 14 of pregnancy (day 1, first day of standing oestrus) in sows. The hormonal secretion of the sows and foetal survival by day 30 of pregnancy was, therefore, studied in 17 crossbred multiparous sows. The sows were randomly allocated into three different groups: one control (C-) group; one food deprived (FD-) group, which was deprived of food from the morning of day 13 of pregnancy until the evening meal on day 14; and a third group (A-), which was given intravenous injections of synthetic ACTH (Synachten Depot), at a dose of 0.01 mg/kg body weight every sixth hour from 6 a.m. on day 13 until 6 a.m. on day 15 of pregnancy. All sows were slaughtered at 30 +/- 2 day of pregnancy and the genital tracts recovered. Total number of corpora lutea (CL), total number of viable or nonviable embryos and foetal survival rates were determined. Samples from the peripheral blood circulation were collected four times a day from day 12 until slaughter, except during days 13-15 when blood was collected every second hour. The blood samples were analysed for cortisol, progesterone, oestrone, prostaglandin F(2alpha)-metabolite, oestrone-sulphate, insulin, free fatty acids and triglycerides. FD-sows had increased levels of cortisol, free fatty acids and progesterone, as well as a lowered level of insulin in the peripheral blood plasma, while A-group sows had increased levels of both cortisol and insulin compared with the C-group. Treatment with ACTH seemed to cause a 2-day delay in the increase of oestrone, from day 19, as seen in the FD- and C-group, to day 21 of pregnancy. At the time of slaughter, there were no significant differences among groups in terms of total number of foetuses and foetal survival rate. The results of the present study suggest a capacity of the sow to compensate for the influence of induced moderate stress at the time of pregnancy when maternal recognition occurs.     

A comparison between plasma oestrone sulphate concentration and doppler ultrasound as methods for pregnancy diagnosis in sows

Plasma oestrone sulphate (E(1)S) concentration and doppler ultrasound as methods of pregnancy diagnosis in sows were compared. Using either method, pregnancy was accurately detected (test sensitivity > 94% for pregnant sows). E(1)S was a better predictor of nonpregnant animals (test specificity 78 vs 66%, respectively; P < 0.01) and could be used at least 1 wk earlier than doppler ultrasound (24 to 30 d vs 35 d postservice, respectively). E(1)S concentration was not an accurate predictor of litter size.     

Some Factors Influencing Pregnancy Rate and Subsequent Litter Size in Primiparous Sows

The pregnancy rate and the subsequent litter size were studied in 332 Swedish Yorkshire primiparous sows, fed according to a commercial Swedish feeding regime during lactation. The sows were weighed and backfat depth was recorded at the first farrowing, at weaning, and at mating. Oestrous detection was performed once daily after weaning, and the interval from weaning to first oestrus (IWO) was recorded. Blood samples for determination of plasma progesterone were drawn regularly after the first weaning. Statistical analyses were only performed on sows with an IWO of 3-8 days. Of these 206 sows were mated on their first (OE1 sows) and 87 sows on their second (87 OE2 sows) oestrus after weaning. The pregnancy rate was 85.4% for OE1 sows and 75.9% for OE2 sows (p=0.048). There was no significant difference in pregnancy rate between OE1 sows with an IWO of 3-5 days and OE1 sows with an interval of 6-8 days. OE2 sows with an IWO of 6-8 days, on the other hand, had a significantly lower pregnancy rate compared with OE2 sows with an interval of 3-5 days. The pregnancy rate in sows that lost more than 30 kg during the first lactation period did not differ from that of sows losing less than 30 kg. In sows with a first litter size of more than 9 piglets alive at birth, the pregnancy rate decreases significantly if mating is delayed until the second oestrus after weaning. OE2 sows had a significantly larger second litter size at birth than OE1 sows (+ 2.0). The litter size at six weeks did not, on the other hand, differ significantly (+ 0.4). There was a positive correlation between the IWO and 2nd litter size, although significant only for OE1 sows between the IWO and litter size alive at birth. In the OE1 group, sows losing 20 kg or less during lactation had significantly larger second litters at birth than the sows losing 21-30 kg, but not significantly larger than the sows losing more than 30 kg. One piglet more, at birth, in the first litter resulted in 0.25 piglet more in the second litter. For sows with a large first litter there was a low probability of also having a large second litter.