Developmental abnormalities of female sexual organs in swine. A post-mortem examination of the genital tract in 1,000 gilts

One thousand reproductive organs from gilts were collected during the period March-August at a slaughterhouse in central Sweden. The organs were inspected in respect of congenital defects and certain reproductive physiological data. The results are recorded in Tables 1–6. Figs. 1–7 show some types of malformations.The total frequency of malformations was 22.1 %, of which 14 % cysts in mesosalpinx and 4.1 % partial duplication of the vagina. The remainder consisted of general developmental defects and of local defects in the tubular genital tract. Malformations with presumed effect on fertility were found in 4.5 % of all organs examined, of which 0.8 % presumably caused permanent sterility and 3.7 % lowered fertility (small litters).Hydrometra was found in 33 cases, 2 of which in sexually mature gilts.The left ovary contained more corpora lutea than the right, and the mean weight of the left ovary was greater than that of the right, both in sexually mature and prepuberal gilts. Of 202 sexually mature gilts examined 16.9 % had cystic corpora lutea in their ovaries as a rule 2–4 in each ovary.     

Evaluation of protective immunity in gilts inoculated with the NADC-8 isolate of porcine reproductive and respiratory syndrome virus (PRRSV) and challenge-exposed with an antigenically distinct PRRSV isolate.

OBJECTIVES: To determine whether intrauterine inoculation of porcine reproductive and respiratory syndrome virus (PRRSV) interferes with conception and whether exposure to one strain of PRRSV provides protection against challenge-exposure (CE) with homologous or heterologous strains of PRRSV. ANIMALS: 40 gilts. PROCEDURE: Gilts were inoculated by intrauterine administration of a PRRSV isolate (NADC-8) at breeding. Inoculated and noninoculated gilts were exposed oronasally to homologous (NADC-8) or heterologous (European isolate) PRRSV during late gestation. Specimens from gilts and fetuses were tested against CE virus. Lack of virus in gilts indicated protective immunity for the dam, in fetuses indicated protection of gilt from reproductive losses, and in both groups indicated complete protection. RESULTS: In the homologous CE group, interval from inoculation to CE ranged from 90 to 205 days, and protection was complete. In the heterologous CE group, interval from inoculation to CE ranged from 90 to 170 days, and protection was incomplete. The CE virus was detected in gilts necropsied 134 to 170 days after CE and in a litter necropsied 170 days after CE. CONCLUSIONS: Homologous protection can be induced in gilts by exposure to live PRRSV. Heterologous protection from reproductive losses can be induced in gilts by exposure to live PRRSV; however, this protection is incomplete and may have a shorter duration than homologous protection. CLINICAL RELEVANCE: Exposure of swine to enzootic PRRSV will provide protection against homologous PRRSV-induced reproductive losses. Extent and duration of protection against heterologous PRRSV may be variable and dependent on antigenic relatedness of the virus strains used for inoculation and CE.     

Bovine viral diarrhea infection in pregnant swine

Twenty pregnant gilts (5 groups of 4) were infected experimentally with 1 of 4 strains of bovine viral diarrhea virus (BVDV) administered intranasally-orally. Blood specimens were taken from the gilts on postinfection day (PID) 7 and cultured for virus. Serum specimens, obtained on PID 21 and at termination of the experiment, were tested for neutralizing antibodies. At 90 to 112 days of gestation, the gilts were euthanatized and their fetuses were examined for evidence of intrauterine infection. Evidence of infection was demonstrated in all of the gilts, either by isolation of BVDV at PID 7 or subsequently by detection of neutralizing antibody titers. Intrauterine infection was confirmed in one of 20 gilts by isolation of BVDV, detection of neutralizing antibodies, and demonstration of microscopic lesions in the fetuses. The microscopic lesions were characterized as nonsuppurative meningitis and choroiditis. Clinical signs of disease were not seen in the infected fetuses. Of 8 gilts exposed to strains of BVDV pathogenic for cattle, 1 gilt developed intrauterine infection, 2 gilts were found barren, and 3 gilts had significantly fewer fetuses than copora lutea.     

Effect of prepubertal feeding regimen on reproductive development of gilts.

The effect of prepubertal feed level on growth and reproductive development of gilts was investigated. At 13 wk. of age, white crossbred gilts were penned individually and assigned to the following treatments: Ad lib, ad libitum intake from 13 to 25 wk. of age (n = 64); Control, ad libitum intake from 13 wk. of age until 100 kg BW and then 90% of ad libitum intake until 25 wk. of age (n = 65); and Restricted, 74% of ad libitum intake from 13 wk. to 25 wk. of age (n = 64). Feed was formulated to primarily restrict energy intake. The study was replicated in two seasons. At 25 wk. of age, gilts were moved to group pens, approximately 16 gilts/pen, allowed ad libitum access to feed, and estrus detection was initiated. Gilts were mated at first estrus and those recycling were remated. After mating, gilts were moved to gestation stalls and fed 1.5x maintenance. At 30 d of gestation, reproductive tracts were harvested, and numbers of corpora lutea (CL) and live embryos were recorded. From 13 to 25 wk. of age, feed consumption was 258 for Ad lib, 251 for Control, and 189 kg/gilt for Restricted, and, from 13 wk. of age until 30 d of gestation, total feed consumption was 367 for Ad lib, 356 for Control, and 299 kg/gilt for Restricted gilts. Age at puberty (196 d) and pregnancy (200 d) was not affected (P>.18) by treatment. However, the rate at which gilts attained puberty (e.g., percentage pubertal at 28 d) was greatest in Ad lib (75) and least in Control (61) gilts. Number of CL and live embryos at 30 d of gestation/gilt assigned to the study was unaffected (P>.21) by treatment. Quantity of feed consumed from 13 wk. of age to 30 d of gestation per live embryo in gilts assigned to the study was 40.0 for Ad lib, 39.8 for Control, and 30.6 kg/gilt for Restricted gilts. These results indicate that moderate feed restriction of gilts during prepubertal development may increase efficiency of swine production without negative impact on reproductive performance through 30 d of gestation.     

Exogenous somatotropin alters IGF axis in porcine endometrium and placenta

The aim of this study was to examine whether exogenous somatotropin (ST) can alter the insulin-like growth factor (IGF) axis in the porcine epitheliochorial placenta. Crossbred gilts were injected either 6 mg of recombinant porcine ST or vehicle from days 10 to 27 after artificial insemination (term day 116). Control and ST-treated gilts were euthanized on day 28 (8 control/5 treated), day 37 (4 control/6 treated), and day 62 (4 control/6 treated) of gestation. Endometrium and placental tissue samples were collected and subjected to mRNA analyses. In control gilts, somatotropin receptor (STR) and IGF-I mRNA abundance in the endometrium decreased with gestation. Conversely, the amounts of IGF-II mRNA and of IGF binding protein (BP)-2 and -3 mRNA, which were analyzed in endometrium and placental chorion, increased with gestation. The endometrium contained less IGF-II mRNA but more IGFBP-2 and-3 mRNA than the placental chorion. In response to pST treatment, the amounts of endometrial STR and IGF-I mRNA were lower at days 28 and 37, but higher at day 62 of gestation. The content of IGF-II mRNA was higher in the endometrium of pST-treated than control gilts on day 37. The amount of IGFBP-2 mRNA was increased on day 37 in endometrium and placenta of pST-treated gilts, whereas no changes in IGFBP-3 mRNA were observed. The IGF-II/IGFBP-2 ratio was higher in the placenta in response to pST on day 28 of gestation. Results show that pST treatment of pregnant gilts during early gestation alters IGF axis in maternal and fetal placental tissues and suggest pST may exert an effect on fetal growth by altering the relative amount of IGFBPs and IGFs at the fetal-maternal interface.     

Growth characteristics, blood metabolites, and insulin-like growth factor system components in maternal tissues of gilts fed L-carnitine through day seventy of gestation

A total of 59 gilts (BW = 137.7 kg) from 3 breeding groups were used to assess the effects of feeding l-carnitine during gestation on gilt growth characteristics, blood metabolites, and uterine and chorioallantoic expression of IGF axis components at d 40, 55, and 70 of gestation. Experimental treatments were arranged in a 2 x 3 factorial, with main effects of added l-carnitine (0 or 50 ppm) and day after initial breeding (d 40, 55, or 70 of gestation). All gilts received a constant feed allowance of 1.75 kg/d and a top-dress containing 0 or 50 ppm of l-carnitine beginning on the first day of breeding through the assigned day of gestation. No dietary treatment differences were observed for gilt BW, backfat, or estimated protein or fat mass at any day of gestation. No differences were observed in circulating total and free carnitine at breeding, but concentrations increased (P < 0.01) as day of gestation increased for gilts fed diets containing l-carnitine compared with those fed the control diet. Maternal IGF-I concentration decreased (P < 0.01) from d 0 to 70 for all gilts, with no differences between treatments. Insulin-like growth factor binding protein-3 mRNA (P = 0.05) and IGFBP-5 mRNA (P = 0.01) increased in the endometrium of gilts supplemented with l-carnitine. These data demonstrate that l-carnitine supplementation and day of gestation alter the expression of the IGF axis by changing the expression of IGFBP at the fetal-maternal interface in swine. These changes in the IGF axis at the fetal maternal interface may aid in determining the reasons for the effects of l-carnitine on reproductive traits.     

Early embryonic death in heifers after inoculation with bovine herpesvirus-1 and reactivation of latent virus in reproductive tissues

Thirteen crossbred heifers seronegative for bovine herpesvirus-1 (BHV-1) were bred naturally to a seronegative bull. Eight heifers were inoculated with BHV-1, IV, on postbreeding day (PBD) 7 or 14. Viremia was detected in heifers 1 through 7, and virus also was isolated from nasal and vaginal secretions of heifers 2, 3, 4, 6, and 7. The pregnancy status of all heifers was monitored from PBD 14 to PBD 35 by determining plasma progesterone concentrations at 1- to 3-day intervals. Decreased progesterone values indicated that pregnancy was not maintained in BHV-1-inoculated heifers 2, 3, 4, 6, 7, and 8. The postbreeding interestrual period of these 6 heifers was normal or only slightly longer than would be expected in the absence of conception. All 5 noninoculated heifers were pregnant on PBD 35. Three to 4 months after acute infection, all BHV-1 inoculated heifers were treated with dexamethasone for 5 days and were euthanatized. Nasal and vaginal swab specimens were tested daily during dexamethasone treatment for excreted BHV-1, and reproductive tissues and adrenal glands were collected at necropsy for virologic tests and histopathologic examination. Virus reactivation was demonstrated in heifers 2 through 8. The BHV-1 isolations were made from adrenal glands of heifers 2, 3, 5, 6, 7, and 8, vaginal swab specimens of heifers 2, 3, 4, 6, and 7, and nasal swab specimens of heifers 2, 3, and 6. Only heifer 3 had virus in reproductive tissues; these isolations were made from ovary, infundibulum, and uterine tube, but not from endometrium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Characterization of effects of zearalenone in swine during early pregnancy

Mature gilts (n = 16) were hand mated and randomly assigned to 1 of 4 groups of 4 gilts each. Treated gilts had 108 mg of purified zearalenone added to their diet on postmating days (PMD) 2 to 6, 7 to 10, or 11 to 15. Control gilts were given the same diet without added zearalenone. On PMD 6, 10, and 15, control gilts had venous cannulas placed in the jugular vein, and blood samples were taken at 20-minute intervals for 4 hours before feeding and 4 hours after feeding. Samples were collected from treated gilts on the last day that zearalenone was consumed. Samples were analyzed for follicle stimulating hormone, luteinizing hormone (LH), and prolactin. Single blood samples were taken by venipuncture on PMD 8, 12, 16, 20, 24, and 28 and at euthanasia and were analyzed for serum concentration of progesterone and estradiol-17 beta. All gilts were euthanatized 30 to 32 days after mating, and fetal development was assessed. Three gilts that were given zearalenone on PMD 7 to 10 were not pregnant and had regressing corpora lutea on the ovaries at euthanasia. All other treated and control gilts were pregnant. Serum samples from treated gilts on PMD 10 and 15 had lower mean prolactin concentrations than did those from controls. The number of LH spikes were fewer (P less than 0.05) in gilts that were given zearalenone on PMD 15 compared with those in controls on PMD 15. Serum progesterone concentrations indicated that corpora lutea regressed between PMD 20 and 28 in nonpregnant gilts.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of vitamin A and beta-carotene on reproductive performance in gilts

The effects of vitamin A and beta-carotene on various reproductive parameters were examined in 108 crossbred gilts. Gilts were fed a diet free of vitamin A and beta-carotene for 5 wk, then assigned to one of eight treatments. Statistical comparisons were performed on three sub-groupings of these treatments as follows: (1) DEFICIENT (received 2,100 IU of vitamin A X head-1 X d-1, (2) FED (received dietary supplementation of 0, 2,100 or 12,300 IU vitamin A and (or) 0, 32.6 or 65.2 mg beta-carotene X head-1 X d-1) or (3) INJECTED (received injection supplementation of 0 or 12,300 IU vitamin A and 32.6 mg beta-carotene X head-1 X d-1, administered once weekly). Gilts remained on treatment through weaning of litters at 21 d postpartum. Plasma vitamin A and beta-carotene levels were greatly elevated in INJECTED gilts. Concentrations of these compounds in plasma were similar between DEFICIENT and FED gilts. There was no treatment difference in number of corpora lutea/gilt. Embryonic mortality was lowest (P less than .01 to .02) in INJECTED gilts (14 +/- 3%) compared with DEFICIENT (29 +/- 5%) or FED (25 +/- 3%) gilts. Baby pig mortality averaged 6 +/- 1% and was not different among treatments. INJECTED gilts had more (P less than .05 to .01) piglets/litter at birth and at weaning (9.5 +/- .3 and 9.0 +/- .3 piglets/litter, respectively) than DEFICIENT (7.9 +/- .5 and 7.6 +/- .5 piglets/litter) or FED gilts (8.7 +/- .3 and 8.1 +/- .3 piglets/litter).(ABSTRACT TRUNCATED AT 250 WORDS)     

Transplacental infection following exposure of gilts to porcine reproductive and respiratory syndrome virus at the onset of gestation

Twenty-five gilts without measurable porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV) serum antibody titres were used for this experiment. All of them were randomly assigned to one of the treatment groups at the time of artificial insemination. Twelve gilts were exposed to PRRSV, of these, six were slaughtered on day 10 after exposure and constituted group A. The remaining six were slaughtered on day 20 after infection and constituted group C. Thirteen gilts were used as controls, six of these were slaughtered on day 10 after treatment and constituted group B. The remaining seven were slaughtered on day 20 after treatment and constituted group D. The infected gilts were inoculated with PRRSV intranasally and intravenously in the ear vein. They were observed for clinical signs of infection and the effects on conception and fertilization rates were studied, while the gilts and their embryos were tested for PRRSV and homologous antibodies. The infected animals developed signs of PRRS associated with anorexia and slight pyrexia. Infection was verified by reisolation of the virus from serum and other tissue samples and also by seroconversion. Ten out of 12 infected gilts and 10 out of 13 controls were pregnant at the time of slaughter and the ratio of embryos to corpora lutea was the same in both, infected and control groups (0.75). Therefore, infection with PRRSV at the onset of gestation did not appear to interfere with conception and fertilization rates and subsequent pregnancy. The PRRSV was not isolated from any of the embryos collected at day 10 postexposure, but was present in 20-day-old embryos of group C gilts. In this group, 60% of litters were infected prenatally, with 16% of embryos infected. The proportion of dead embryos was three times greater than in control group D (35.4% and 9.8%, respectively). The results of this report indicate that exposure of susceptible gilts to PRRSV at the onset of gestation has no significant effect on conception and fertilization rates. However, although infection does not appear to have any effect on the embryos before implantation, it can result in transplacental infection and embryo death.     

Appearance of the uterine specific proteins following induction of ovulation in prepubertal gilts.

The appearance of the uterine specific proteins following induction of ovulation in prepubertal gilts is described. 12 gilts each at 3, 4, and 5 months of age were allotted randomly to 1 of 2 treatment groups prior to induction of ovulation: 1) saline treated and 2) human chorionic gonadotropin (HCG) treated (400 IU daily from Days 12 through 16 of the induced cycle). Ovulation was induced with HCG following treatment with pregnant mare serum gonadotropin and the day of ovulation was designated as Day 1. All the gilts were laparotomized and uteri infused with phosphate-buffered saline on Day 16 to obtain uterine protein secretions. Plasma progesterone levels on Day 11 and observations made at laparotomy indicated that only 1 gilt 3 months of age failed to ovulate. The number of corpora lutea, plasma progesterone, total recoverable uterine protein, and uterine specific protein on Day 16 were markedly affected by the age of the gilt. These same characteristics, except uterine specific protein, were additionally affected by HCG treatment. Total recoverable uterine protein and uterine specific protein in saline and HCG-treated gilts at 3, 4, and 5 months of age were 6.3 and 1.5, 10.4 and 2.8; 38.8 and 15.2, 51.6 and 15.9; 20.4 and 7.7, 47.8 and 14.6 mg, respectively. Polyacrylamide slab gel electrophoresis showed that HCG-treated gilts at 3 months of age and both saline- and HCG-treated gilts at 4 and 5 months of age generally produced the purple basic protein and the complete profile of the low molecular weight acidic proteins during the induced cycle.     

Assessing the duration of persistence and shedding of porcine reproductive and respiratory syndrome virus in a large population of breeding-age gilts

Porcine reproductive and respiratory syndrome virus (PRRSV) is an RNA virus in the order Nidovirales, family Arteriviridae, genus Arterivirus. The virus induces a prolonged viremia, replicates in macrophages, and produces persistent infection. The purpose of this study was to determine if PRRSV could persist for 90 d or more in a large population of breeding-age gilts housed under environmental conditions typical of commercial swine production and to determine if experimentally infected gilts could shed virus to naïve sentinel gilts beyond 90 d postinfection. Using the intranasal route, we inoculated 120 PRRSV-naïve gilts, 4 mo of age, with 5 mL of cell culture fluid containing a total dose of 10^2.4 TCID₅₀ of a field isolate (MN-30100) of PRRSV. The index gilts were organized into 3 groups (A, B, and C), 40 gilts per group. To assess the dynamics of the experimental infection, a monitor group of 30 index gilts was blood-tested on days 0, 3, 7, 14, 30, 60, 90, 120, 150, and 180 postinfection. PRRSV viremia was detected with the polymerase chain reaction (PCR) on days 3, 7, and 14 and by virus isolation (VI) on days 7 and 14. PRRSV antibodies were detected from day 14 by enzyme-linked immunosorbent assay (ELISA). To assess shedding, 30 PRRSV-naïve sentinel gilts were commingled with the index gilts on day 90 postinfection and tested by PCR, VI, and ELISA every 15 d until 180 d postinfection; all samples were negative. To assess persistence, 40 index and 10 sentinel gilts were slaughtered at 120 (group A), 150 (group B), or 180 (group C) d postinfection. Evidence of PRRSV was not detected by PCR or VI in any tissue samples from the 120 index gilts. These results indicate that persistence and shedding of PRRSV are of short duration in breeding-age gilts.     

Long-term effects of boron supplementation on reproductive characteristics and bone mechanical properties in gilts

An experiment was conducted to determine long-term effects of dietary boron (B) on reproductive and bone characteristics in gilts. Weanling gilts (n = 50) were allotted to 10 pens based on weaning weight and litter origin. Pens were randomly assigned to receive one of two dietary treatments that consisted of a basal diet low in B (control) and the basal diet supplemented with 5 mg of B/kg diet as sodium borate. Gilts remained on their respective experimental diets throughout the nursery phase, growing-finishing phase, sexual maturity, breeding, gestation, and lactation. The day of first observed standing estrus was defined as puberty, and each pubertal gilt was bred via AI at the second observed standing estrus. Eight randomly selected gilts per treatment were slaughtered at d 35 of gestation for the assessment of embryonic and reproductive characteristics, bone characteristics, and tissue B concentrations. The remaining pregnant gilts (control, n = 11; 5 mg supplemental B/kg diet, n = 10) farrowed, and litter characteristics at farrowing and weaning were determined. Age at puberty was not affected (P = 0.72) by B, and neither were the number of corpora lutea on the ovaries (P = 0.44) or the total number of embryos (P = 0.95) at d 35 of gestation. Boron supplementation increased (P = 0.05) pig weaning weight and tended (P = 0.11) to increase pig birth weight; however, no other litter characteristics were affected (P > 0.12) by B. Extrinsic and intrinsic strength measures of bone were increased (P < 0.09) by B. Fat-free bone ash percentage and bone mineral concentrations were not affected (P > or = 0.19) by dietary B. Supplemental B increased (P < or = 0.06) the B concentrations of the muscle, liver, and reproductive tissues. Serum osteocalcin concentrations tended (P = 0.13) to be increased by dietary B, which may be related to increased bone turnover in B-supplemented gilts. Results indicate that B may have beneficial effects upon reproductive and bone characteristics.     

Effects of a synthetic progestogen, altrenogest, on oestrus synchronisation and fertility in miniature pigs

Groups of six, six and eight miniature gilts, respectively, received 5, 10 or 15 mg/day of altrenogest for 18 days, and the numbers of corpora lutea and residual follicles were counted approximately 14 days after the treatment by an exploratory laparotomy. They were compared with the numbers in a control group of eight gilts which were examined six to eight days after oestrus. The interval between the last dose of altrenogest and the onset of oestrus increased with the dose of altrenogest, and was significantly longer after the treatments with 10 or 15 mg/day than after 5 mg/day (P < 0.01). Significantly more corpora lutea were observed in the gilts receiving 5 or 10 mg/day of altrenogest than in the control gilts (P < 0.1). Groups of six, seven and six miniature gilts that had respectively received 5, 10 or 15 mg/day of altrenogest were artificially inseminated; four, six and five of the gilts in these groups farrowed, and their mean (sd) litter sizes were 5.5 (2.4), 6.8 (1.2) and 5.0 (2.3), respectively. All six of a group of control gilts farrowed and their mean litter size was 5.8 (1.2).     

Consequences for body composition at farrowing and nutrient partitioning during lactation of a choice-feeding regime during rearing and pregnancy in gilts of different genotypes

The potential conflict between reproductive functions and the drive to deposit body protein may impair productive performance in modern gilts of lean genotype. To study the response of the gilt to this conflict, a choice-feeding experiment was carried out to measure the nutrient intake selected by breeding gilts and responses in reproductive and lactation performance. Using a 2 × 2 factorial design, gilts of two different genotypes (24 of NPD 402, expected higher body protein/lipid ratio (L) or 24 of Camborough 23, expected lower body protein/lipid ratio, (F)) were either choice-fed (C) by offering both a low (120 g crude protein (CP)/kg) and a high protein (218 g CP/kg) feed during rearing and pregnancy or fed conventionally (R) single feeds, ad libitum during rearing and restricted during pregnancy. Choice-fed gilts selected mainly the low protein feed (0.92 of total feed intake) regardless of genotype and had lower protein intakes than R gilts prior to puberty. However, in pregnancy, due to higher feed intakes, C gilts had higher dietary protein and energy intakes than R gilts. C gilts were heavier, and had greater back-fat and eye muscle depth at farrowing than R gilts, but had smaller litter sizes (P < 0.01). During lactation, dietary treatments were reallocated so that gilts received either a low (LE, maintenance + 45 MJ/day) or a high (HE, maintenance + 67 MJ/day) digestible energy intake. Litter size was standardised within 2 days of farrowing. LE gilts had greater decreases in weight and back-fat and eye-muscle depth during lactation than HE gilts, but dietary lactation treatment had no effect on litter performance. The choice-feeding regime which resulted in heavier gilts with greater back-fat and eye-muscle depth at farrowing did not produce any advantage in terms of partitioning of nutrients towards milk production, as indicated by litter performance, irrespective of gilt genotype. F gilts had greater piglet growth rates than L gilts and also had a higher milk protein concentration. A greater number of L than F gilts failed to complete the experiment for health reasons. Treatment effects on glucose tolerance at day 13 of lactation were not significant. Choice-feeding was therefore not found to be suitable for determining nutrient requirements of modern lean-genotype gilts which would improve reproductive performance.     

Response of gilts with delayed puberty to pregnant mare serum gonadotropin or estrogen

The effect of pregnant mare serum gonadotropin (PMSG) or estradiol cyclopentylpropionate (EC) on the induction of estrus, duration of estrus, and serum progesterone concentration after estrus was evaluated in 8 gilts with delayed puberty. Four gilts were given 500 IU of PMSG IM and 4 were given 2 mg of EC, IM. The inactive status of the ovaries at the time of treatment was verified by serum progesterone values of less than 0.5 ng/ml in serial samples collected before treatment. The 4 EC-treated gilts came into estrus at a mean of 3.5 days after treatment, but 1 of the gilts did not form corpora lutea. Three PMSG-treated gilts came into estrus at a mean of 4.0 days after treatment. The remaining PMSG-treated gilt remained anestrus and did not form corpora lutea. The mean duration of estrus in EC-treated gilts was 5.25 days compared with 2.0 days for PMSG-treated gilts (P less than 0.05). Serum progesterone concentrations were higher in PMSG-treated gilts than in EC-treated gilts at 8, 11, and 17 days after treatment (P less than 0.05).     

猪细小病毒N株的生物学和免疫学特性研究

猪细小病毒N株是从广西初产母猪所产死胎脏器分离的自然弱毒株。用这个毒株接种PPV HI抗体阴性的四月龄小猪和怀孕14～23天的后备母猪进行安全性试验,结果无任何异常临床症状、病毒血症和同居感染,母猪分娩正常,初生仔猪在吃初乳前HI抗体阴性。该毒株免疫的小猪、后备母猪和怀孕母猪,完全能抵抗猪细小病毒强毒攻击,攻毒后49天剖杀母猪,结果胎儿正常,胎儿心血HI抗体阴性,取胎儿脏器未分离出病毒,分娩母猪产仔正常,仔猪吃初乳前HI抗体阴性。而对照猪攻毒后产生病毒血症,产下不同组合异常仔,并从死胎儿脏器分离出病毒,健活仔猪吃初乳前能测出HI抗体。从而证明用N株作为弱毒苗能防止由猪细小病毒引起的繁殖障碍性疾病。     

Serum profiles of progesterone, LH, FSH and prolactin immediately preceding induced puberty in gilts

Two experiments were conducted to determine if the secretory patterns of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin (PRL) and serum concentrations of progesterone change immediately preceding induced puberty in gilts. To help predict when prepubertal gilts would attain puberty, gilts were induced into puberty by relocation from confinement housing to an outdoor lot and exposure to mature boars. In Exp. 1, 17 prepubertal gilts were bled on two successive days from 0800 to 1200 h before relocation and boar exposure and until the second day of estrus or for 8 d in gilts that failed to exhibit estrus. Blood samples were collected from indwelling cannulas at 20-min intervals for 4 h. In Exp. 2, blood samples were collected from 20 prepubertal gilts at 20-min intervals from 0800 to 1200 h and from 2000 to 2400 h until the second day of estrus or for 6 d if the gilt failed to exhibit estrus. In each experiment, 11 gilts exhibited pubertal estrus 3 to 6 d after relocation and boar exposure. When the frequency of LH spikes in each gilt was normalized to the day of her preovulatory surge of LH (d 0), a decline in the frequency of LH secretory spikes was observed as gilts approached puberty. However, neither the average magnitude of LH spikes nor mean LH concentrations were different among these days. Mean serum concentrations, frequency of spikes or average magnitude of secretory spikes of FSH or PRL did not change on the days preceding the preovulatory peak of LH.(ABSTRACT TRUNCATED AT 250 WORDS)     

饲粮菜籽粕水平对青年母猪繁殖性能的影响

48头浙江中白后备母猪按窝别、体重分成4组,在6～8月龄和配种后至第二胎分娩后20天期间,分别饲喂菜籽粕(含硫代葡萄糖苷 3.7mg/g)替代饲粮中豆饼蛋白质0、25、50和75％的4种后备母猪饲粮和繁殖母猪饲粮,以研究饲粮菜籽粕水平对青年母猪繁殖性能的影响。结果表明,饲粮菜籽粕水平对母猪采食量、初孕年龄、头胎断奶至第二胎怀孕间隔时间、一次情期受胎率、平均妊娠天数、总产仔数、产活仔数、仔猪初生重、60日龄育成数、后备母猪日增重和饲料报酬均无显著影响(P>0.05),但母猪初孕年龄和断奶再怀孕间隔时间有随饲粮菜籽粕水平增高而延长的趋势,产活仔数和育成仔数有下降趋势。后备母猪增重成绩以25％菜籽粕替代组较优。仔猪20和60日龄平均体重菜籽粕组显著低于豆饼对照组(P<0.05),60日龄平均体重,50％菜籽粕替代组显著低于25％替代组(P<0.05)。由此可见,母猪饲粮中菜籽粕用量,按补充蛋白质计,以不超过25％为宜。     

The Use of an Immunomodulator to Enhance the Reproductive Performance of Gilts Transported for Long Distances from Breeding to Commercial Units

Contents
The reproductive performance of gilts transported for long distances from three high-health breeding farms to six commercial farms was tested after the use of a Parapox-ovis-virus-based immunomodulator, Baypamun N (Bayer AG, Germany). Sixty (60) gilts were injected with Baypamun N, three times (2 days before departure, 2 h before departure and 2 days after their arrival at the commercial farms), while the remaining 60 gilts were injected with placebo at the same times. The results indicated that: (i) no adverse reactions or adverse effects were noticed related to the treatment with Baypamun N, (ii) treatment with Baypamun N improved the reproductive performance of gilts; the proportion of gilts farrowed/total gilts examined, the total number of piglets born, the number of piglets born alive and the body-weight of piglets at farrowing were significantly increased (p < 0.05), and (iii) treatment with Baypamun N reduced (p < 0.05) the cost of medication per gilt examined and per served gilt.