Semen changes in boars after experimental infection with porcine reproductive and respiratory syndrome (PRRS) virus

Eleven boars seronegative to porcine reproductive and respiratory syndrome virus (PRRSV) were trained for semen collection: five boars were inoculated intranasally with 6 x 10(6)TCID(50)/ml of PRRSV (Group A); four boars were inoculated intranasally with 6 x 10(4)TCID(50)/ml (Group B); and two boars were used as uninfected control (Group C). Semen samples were collected at 7-d intervals from 49 d prior to experimental inoculation with PRRSV to 70 d after inoculation, and were examined for sperm volume, sperm concentration, sperm morphology, sperm motility and for the presence of PRRSV. The infection in boars was demonstrated by the reisolation of PRRSV from the serum of all inoculated boars. Rectal temperatures and general health of the boars were clinically normal throughout the trial. Differences were observed in the quality of semen collected from boars after experimental infection with PRRSV. This infection induced a significant decrease in sperm motility and in spermatozoa with normal acrosomes. Of the semen samples tested for virus isolation in swine alveolar macrophages PRRSV was only isolated in 1 boar from Group B. The virus was detected in an additional semen sample in Group A by the production of an antibody titer in a biological assay. All attempts to detect PRRSV by RT-PCR in semen samples were unsuccessful. Nevertheless, from our study it is possible to suggest that the PRRSV can occasionally be transmitted in the semen during the initial phase of the disease.     

Identification of embryo paternity using polymorphic DNA markers to assess fertilizing capacity of spermatozoa after heterospermic insemination in boars

Differences in sperm fertilizing capacity of males often remain undetected by routine semen parameters. Heterospermic insemination with equal numbers of spermatozoa from 2 males is an accurate method for assessing differences in fertility. Use of heterospermic insemination depends on a reliable, efficient assay to identify paternity of conceptuses or offspring. In this study, polymorphic DNA markers amplified by PCR were tested to determine paternity of Day 5 to 6 embryos. The fertilizing capacity of 2 boars (A and B) with similar semen parameters was compared after homospermic (n=14 gilts) and heterospermic (n=11 gilts) insemination. Single AI's were performed under suboptimal conditions using 1 x 10(9) spermatozoa at 12 to 24 h before ovulation to prompt differences in fertilization and to stimulate sperm competition. The fertilization rate and the number of accessory spermatozoa were determined in Day 5 to 6 embryos. Using 5 different polymorphic DNA markers, paternity could be determined in 95.8% of the embryos. Boar B sired significantly (P<0.05) more offspring than Boar A after insemination with pooled semen, and this was reflected by a significantly (P<0.05) higher number of accessory spermatozoa following homospermic insemination with semen from Boar B, although fertilization rates did not differ between the 2 boars after homospermic insemination. The results suggest that the viability of spermatozoa in the female reproductive tract contributes to differences in fertility rates of males with similar in vitro sperm quality parameters. The number of accessory spermatozoa is a more sensitive measure of boar fertility than the fertilization rate. Polymorphic DNA markers are suitable for verification of parentage even at a very early stage of embryonic development.     

Effectiveness of frozen boar semen under practical conditions of artificial insemination

A technique of boar semen deep-freezing and frozen semen use was tested in practice. 338 sows and 43 gilts belonging to small herds with less than 10 females each were inseminated without oestrus detection by a teaser boar. About 58 % of the inseminated females produced 9.3 piglets per litter. But there were differences between parities. The sows had the highest fertility rate, whereas the gilts showed a significantly lower farrowing rate (59.8% vs 41.9%; P < 0.05). The standing reaction of the female to the back pressure test made by the inseminator and the behaviour of the female during insemination had an effect on the farrowing rate. The best result was obtained after a standing reaction and a behaviour score of 1 (64.5% and 9.6 piglets for farrowing rate and litters size respectively). Farrowing rate for inseminators ranged from 44.3% to 62.4% among inseminators. Farrowing rate for females inseminated with frozen semen from Large-White, Landrace, Pietrain boars was not different, but there were significant differences between the boars. Results showed that insemination with deep-frozen boar semen could be used under practical conditions as an additional technique to the use of fresh semen.     

Apoptotic-like changes in the spermatozoa of fresh and stored boar semen and the quality of embryos produced in vivo

The aim of this study was to determine the apoptotic-like changes in the spermatozoa of fresh and stored boar semen and to investigate the relationship between this phenomenon and the quality of embryos produced in vivo. The experiments were divided into two series. In the first series, ten ejaculates were collected from five boars, which were crossbreeds of the Polish Landrace and Large White breeds. The semen was stored as a liquid until Day A (the day on which sperm motility decreased to 30%). Three fluorescence methods were used to evaluate semen quality: an assay to assess the early changes in sperm membrane integrity using the fluorophore YO-PRO-1, an assay for phosphatidylserine (PS) translocation across the plasma membrane using fluorescein-labeled annexin-V and the mitochondrial-specific probe JC-1 (5,5',6,6'-tetrachloro-1,1',3,3' tetraethylbenzimidazolylcarbocyanine iodide) for measuring changes in mitochondrial membrane potential. Our results showed that liquid preservation of boar semen causes apoptotic-like changes in the sperm, and a significant increase in both: apoptotic sperm (YO-PRO-1(+)/PI(-)) and early apoptotic sperm (annexin-V(+)/PI(-)) were observed between Day 0 (fresh semen) and Day A only in semen from three of the five boars. In the second series of experiments, the semen from boar nos. 1, 2, and 3 was selected for insemination of superovulated gilts. The fertilizing capacity of fresh and stored semen with different levels of apoptotic spermatozoa was measured based on the morphology and the number of cells of embryos that were obtained after insemination with this semen. Our studies indicated no significant differences in the fertilization rate of gilts after insemination with fresh and stored semen with increased levels of apoptotic spermatozoa. After insemination with stored semen, a significantly greater number of degenerated embryos were observed, but the morphologically normal blastocysts obtained after insemination with either fresh or stored semen had a similar number of nuclei.     

Effect of time of insemination relative to ovulation on fertility with liquid and frozen boar semen

Precise data on fertility results following peri- and postovulatory insemination in spontaneously ovulating gilts is lacking. Using transcutaneous sonography every 4 h during estrus as a tool for diagnosis of ovulation, the effects of different time intervals of insemination relative to ovulation were investigated with liquid semen (Experiment 1, n=76 gilts) and frozen semen (Experiment 2, n=80 gilts). In Experiment 3 (n=24 gilts) the number of Day-28 embryos related to the various intervals between insemination and ovulation was determined after the use of liquid semen. Using liquid semen the fertilization rates based on Day-2 to Day-5 embryos and the number of accessory spermatozoa decreased significantly in gilts inseminated with 2 x 10(9) spermatozoa per dosage in intervals of more than 12 h before or more than 4 h after ovulation. In the time interval 4 to 0 h before ovulation, comparable fertilization rates were obtained using frozen semen (88.1%) and liquid semen (92.5%). Fertilization rates and numbers of accessory spermatozoa decreased significantly when gilts were inseminated with frozen semen more than 4 h before or 0 to 4 h after the detection of ovulation. The percentage of Day-28 embryos was significantly higher following preovulatory insemination compared to inseminations 0 to 4 h and 4 to 8 h after ovulation. It is concluded that the optimal time of insemination using liquid semen is 12 to 0 h before ovulation, and 4 to 0 h before ovulation using frozen semen. The results stress the importance of further research on sperm transport and ovulation stimulating mechanisms, as well as studies on the time of ovulation relative to estrus-weaning intervals and estrus duration.     

Porcine reproductive and respiratory syndrome virus infection in the boar: a review

Porcine reproductive and respiratory syndrome (PRRS) is caused by PRRS virus, which, like other members of the Arterividae family, has the ability to infect macrophages and to persist in tissues for at least several months after the acute stage of infection subsides. As a consequence, PRRS has a complex epidemiologic profile and has been especially difficult to control under the usual conditions of commercial swine production. Although vaccines are commonly used, vaccination is only one of several approaches to be considered in designing a control strategy. At least equally important are procedures developed on the basis of a thorough understanding of the epidemiology of the disease. The objective of this review is to summarize current knowledge in relation to PRRS virus (PRRSV) infection in the boar. The information available related to this topic will be summarized and discussed, and the implications for the control of the condition highlighted. The main emphasis will be on questions about the pathogenesis of infection, including duration of viremia and the origin of PRRSV found in semen; the clinical signs associated with the disease, paying special attention to the effects on seminal quality; the epidemiology of the condition, with special emphasis on the duration of PRRSV shedding in semen and the implications that this may have on venereal transmission, as well as the role that other potential routes of shedding may have on the dissemination of PRRSV.     

The initial fertilizing capacity of longerm-stored liquid boar semen following pre- and postovulatory insemination

In pigs, high variation is seen in the duration of estrus and in the time of ovulation. This is one of a wide range of factors not related to semen quality, which possibly influences the results of field insemination trials. Experiment 1 (n=81 gilts) was performed to determine the influence of the time of ovulation on the fertilizing capacity of liquid boar semen stored up to 118 h. The objective of Experiment 2 (n=102 gilts) was to study the fertilizing potential of semen stored up to 120 h in 2 different extenders, Androhep and Beltsville Thawing Solution (BTS), by means of postovulatory AI. Inseminations were performed 0 to 4 h after ovulation in order to standardize the trial conditions. Fertilization rates based on Day-2 to Day-4 embryos, and the number of accessory spermatozoa per zona pellucida did not differ between semen stored for 0 to 48 and 48 to 87 h in gilts ovulating within 12 after insemination (Experiment 1). Gilts with an interval of 12 to 24 h between AI and ovulation had lower fertility results using semen stored for more than 48 h. A further decrease was observed when semen storage exceeded 87 h in those gilts ovulating later than 24 h after insemination. The time of ovulation has to be considered as being a major factor of variation in the fertility results of AI trials. In Experiment 2, fertilization rates and numbers of accessory spermatozoa decreased between semen stored for 0 to 24 and 24 to 48 h in BTS, and between semen stored for 0 to 24 and 48 to 72 h in Androhep. Significant differences in fertility between diluents were seen only when using semen stored for more than 96 h, with semen extended with Androhep giving the higher results. The results indicate that the decrease in fertilizing capacity due to in vitro aging of spermatozoa cannot be prevented even during the first days of storage.     

Reproductive performance of gilts following vaccination and subsequent heterologous challenge with European strains of porcine reproductive and respiratory syndrome virus

The objective of this study was to evaluate the efficacy of two commercially available modified live virus vaccines for preventing the reproductive and early postnatal consequences of infecting (challenging) pregnant gilts with virulent porcine reproductive and respiratory syndrome virus (PRRSV). For this purpose 21 crossbred gilts were allocated to one or another of four groups (Groups A-D). Group A comprised four gilts neither vaccinated nor challenged; Group B comprised five gilts that were challenged but not vaccinated; Group C comprised seven gilts that were vaccinated (AmervacPRRS) and challenged; Group D comprised five gilts that were vaccinated (Pyrsvac-183) and challenged. Vaccination was 24 days before conception, and challenge was at 90 days of gestation. Both vaccine viruses and the challenge virus were European strains but differed in part from one another on the basis of their genetic (nucleotide) sequence. After challenge PRRSV was isolated from five (100%), four (57%), and two (40%) of the gilts of Groups B, C and D, respectively. Although vaccination failed to prevent a detectable viremia in all of the gilts of Groups C and D after they were challenged (or congenital infection of some of their pigs), it did provide a statistically significant level of protection in regard to the incidence of congenital infection, reproductive performance, and pig health and viability. Namely, for Groups C and D the numbers of liveborn pigs/litter and healthy pigs/litter throughout the early postnatal period were similar to those of Group A (nonvaccinated and nonchallenged) and far exceeded those of Group B (nonvaccinated and challenged).     

Porcine reproductive and respiratory syndrome (PRRS) virus in wild boar and Iberian pigs in south-central Spain

Porcine reproductive and respiratory syndrome (PRRS) is a swine infectious disease causing major economic problems on the intensive pig industry. This virus has been reported worldwide in domestic pigs and there is evidence of PRRS virus (PRRSV) infection in wild boar (Sus scrofa). Nonetheless, the epidemiological role of wild boar and extensively kept domestic pigs remains unclear. The aim of this study was to determine the occurrence of PRRS in wild boar and Iberian pigs in the dehesa ecosystem of the Castile-La Mancha region of Spain, which boasts one of the most important free-roaming porcine livestock and hunting industries in the country. Using geo-spatial analysis of literature data, we first explored the relationship between domestic pig density and PRRS occurrence in wild boar in Europe. Results revealed that PRRS occurrence in wild boar may be influenced, albeit not significantly, by domestic pig density. Next, we analyzed sera from 294 wild boar and 80 Iberian pigs by indirect enzyme-linked immunosorbent assay for PRRSV antibodies. The sera and 27 wild boar tissue samples were analyzed by two real-time RT-PCR assays, targeting the most conserved genes of the PRRSV genome, ORF1 and ORF7. Seven wild boar (2.4 %) and one Iberian pig (1.3 %) were seropositive, while none of the animals tested positive for PRRSV by RT-PCR. Our results confirm the limited spread of PRRSV in free-roaming Iberian pigs and wild boar living in mutual contact. Further studies would be necessary to address whether this low seroprevalence found in these animals reflects transmission from intensively kept pigs or the independent circulation of specific strains in free-roaming pigs.     

Reproduction in porcine circovirus type 2 (PCV2) seropositive gilts inseminated with PCV2b spiked semen

ABSTRACT: BACKGROUND: Since 1999, field evidence of transplacental infection by porcine circovirus type 2 (PCV2) and reproductive failure has been reported in pigs. The objective of this study was to evaluate the clinical and pathological consequences of PCV2 infection in conventional PCV2-seropositive gilts by insemination with PCV2b-spiked semen. RESULTS: Six PCV2 seropositive gilts were inseminated with PCV2b-supplemented semen (infected) and three animals with semen and cell culture medium (controls). Only three out of the six infected animals were pregnant by ultrasonography on day 29 after insemination, while two out of the three controls were pregnant. One control gilt aborted on day 23 after insemination but not due to PVC2. Viraemia was demonstrated in four out of six infected and in one control gilt that became infected with PCV2a. Anti-PCV2 antibody titres showed dynamic variations in the infected group throughout the study. Among infected gilts, the animal with the lowest anti-PCV2 titre (1/100) at the beginning of the experiment and another that reached a similar low value during the experiment showed evident seroconversion over time and had also PCV2 positive foetuses. One placenta displayed mild focal necrosis of the chorionic epithelium positively stained by immunohistochemistry for PCV2 antigen. CONCLUSIONS: PCV2-seropositive gilts can be infected with PCV2 after intrauterine exposure and low maternal antibody titre may increase the probability of a foetal infection.     

Regression analyses and motile sperm subpopulation structure study as improving tools in boar semen quality analysis

A precise estimation of the fertilizing ability of a boar ejaculate would be very useful to improve pig assisted reproduction results. For this purpose, we tested the mathematical combination of several parameters of the boar semen quality analysis, including the computer-assisted semen motility analysis (CASA), as a predictive fertility tool. The utilized mathematical relations among parameters were logistic and linear regressions. Two mathematical models obtained by logistic regression involving Osmotic Resistance Test (ORT Test), Hyperosmotic Resistance Test (HRT Test) and viability of fresh samples, showed a significant (P<0.05) correlation between semen characteristics and conception rate. However, none of the obtained models produced a significant correlation model between semen characteristics and prolificacy. The CASA analyses show that three separate subpopulations of spermatozoa with different motility characteristics coexist in boar ejaculates. There were significant (P<0.001) differences in the distribution of these subpopulations among boars, but no clear relationship between motile subpopulation structure and fertility was obtained. Our results support the belief that the predictive use of the results obtained in a standard boar semen quality analysis can reasonably be achieved by applying logistic correlation analyses among several function parameters of boar semen quality analysis and in vivo conception rates obtained after artificial insemination (AI).     

Effect of time of ovulation and sperm concentration on fertilization rate in gilts

In normal production practices, sows and gilts are inseminated at least twice during estrus because the timing of ovulation is variable relative to the onset of estrus. The objective of this study was to determine if a normal fertilization rate could be achieved with a single insemination of low sperm number given at a precise interval relative to ovulation. Gilts (n=59) were randomly assigned to one of three treatment groups: low dose (LD; one insemination, 0.5 x 10(9) spermatozoa), high dose (HD; one insemination, 3 x 10(9) spermatozoa) or multiple dose (MD; two inseminations, 3 x 10(9) spermatozoa per insemination). Twice daily estrus detection (06:00 and 18:00 h) was performed using fenceline boar contact and backpressure testing. Transrectal ultrasonography was performed every 6 h beginning at the detection of the onset of standing estrus and continuing until ovulation. Gilts in the LD and HD groups were inseminated 22 h after detection of estrus; MD gilts received inseminations at 10 and 22 h after detection of estrus. Inseminations were administered by using an insemination catheter and semen was deposited into the cervix. The uterus was flushed on Day 5 after the onset of estrus and the number of corpora lutea, oocytes, and embryos were counted. Time of insemination relative to ovulation was designated as 40 to >24 h, 24 to >12 h, and 12 to 0 h before ovulation and >0 h after ovulation. The LD gilts had fewer embryos (P<0.04), more unfertilized oocytes (P<0.05) and a lower fertilization rate (P<0.07) compared to MD gilts. The effects of time of insemination relative to ovulation and the treatment by time interaction were not significant. We conclude that a cervical insemination with low spermatozoa concentration may not result in acceptable fertility even when precisely timed relative to ovulation.     

The fecundity of porcine semen stored for 2 to 6 days in Androhep and X-CELL extenders

Extending the raw ejaculate prior to artificial insemination (AI) is beneficial, in part, due to the increased number of females that are bred from an ejaculate, along with prolonged shelf life of the semen. The objective of this study was to examine the affects of storage time on the fecundity of porcine semen diluted in 2 semen extenders, Androhep and X-CELL. A completely randomized design with a factorial arrangement of treatments was utilized in which 429 high quality, gel-free ejaculates from 48 boars were used in a timed, double insemination of 1,431 first-service gilts. The gilts were divided into groups and inseminated with semen stored in Androhep or X-CELL for 2 to 3 d, 3 to 4 d, 4 to 5 d, or 5 to 6 d prior to use (day of collection = Day 0). Sperm age was identical, and both extenders were used concurrently each day of the trial. Farrowing rate and litter size data were recorded. Farrowing rates did not differ between extenders through Days 4 to 5 of storage. Gilts inseminated with Androhep diluted stored semen showed a decrease (P < 0.001) in farrowing rate compared with those inseminated with semen extended in X-CELL stored for 5 to 6 d. Mean litter sizes did not differ between extenders through Days 2 to 3 of storage. Compared with the X-CELL extended semen, gilts inseminated with Androhep extended semen produced smaller litters when semen was stored for 4 to 5 d (P < 0.05). Within the Androhep treatment, smaller mean litter sizes (P < 0.05) were evident when the semen was stored for 3 to 4 and 4 to 5 d. No differences were detected in litter size or farrowing rate for gilts bred with semen stored for 2 to 6 d in the X-CELL extender (P > 0.1). The results of this study indicate that extender type influences the fertility potential of fresh porcine semen stored for 2 to 6 d. For optimal fecundity in gilts, semen extended with Androhep extender should be used for AI within 3 d. The X-CELL extended semen can be used for up to 6 d without significant decrease in litter size or farrowing rate. These recommendations are dependent upon using high quality semen that is properly handled from collection through insemination.     

Effect of natural or vaccine-induced porcine circovirus type 2 (PCV2) immunity on fetal infection after artificial insemination with PCV2 spiked semen

The objectives of this study were to determine if vaccination against porcine circovirus type 2 (PCV2) or previous PCV2 infection of the dam are sufficient to prevent fetal infection when dams are artificially inseminated with PCV2-spiked semen. Nine sows (Sus domestica) were allocated into three groups of three dams each: The PCV2 naïve negative control Group 1 was artificially inseminated with extended PCV2 DNA negative semen during estrus, whereas the extended semen used in the vaccinated Group 2 (PCV2 vaccine was given 8 wk before insemination) and PCV2-exposed Group 3 (infected with PCV2 12 wk before insemination) was spiked with 5 mL of PCV2 inoculum with a titer of 10^4.2 tissue culture infectious dose (TCID₅₀) per milliliter at each breeding. The dams in the vaccinated and PCV2-exposed groups were positive for PCV2 antibody but negative for PCV2 DNA in serum at the time of insemination. Three negative control dams, two vaccinated dams, and three dams with previous PCV2 exposure became pregnant and maintained pregnancy to term. After artificial insemination, viremia was detected in one of three vaccinated dams and in two of three dams with previous PCV2 exposure. At farrowing, PCV2 infection was not detected in any piglets or fetuses expelled from the negative control dams or from dams with previous PCV2 exposure. In litters of the vaccinated dams, 15 of 24 live-born piglets were PCV2 viremic at birth, with 6 of 26 fetuses having detectable PCV2 antigen in tissues. In conclusion, vaccine-induced immunity did not prevent fetal infection in this sow model using semen spiked with PCV2.     

Intraperitoneal insemination, sperm transport and capacitation in the pig

Intraperitoneal insemination was studied in a total of 58 pigs, both to ascertain the success of this route of sperm deposition with the eventual use of frozen-thawed boar semen in mind and to estimate the timing of capacitation in the absence of uterine exposure of spermatozoa. Ovulation was controlled in mature gilts, and 5–20 ml freshly collected semen containing approximately 10⁸ spermatozoa per ml introduced through the peritoneum either by means of mid-ventral laparotomy or using a 3.5-in (ca. 9 cm) × 18-gauge hypodermic needle.Embryo development to the morula and blastocyst stage appeared chronologically and cytologically normal after intraperitoneal insemination, but the timing of semen deposition was critical: optimal levels of fertilization (60%) arose from insemination in the 12 h preceding ovulation. Fertility was never comparable to that found after natural mating due to the inefficiency of sperm transport into the oviducts and the absence of significant sperm reservoirs. The timing of sperm capacitation after intraperitoneal insemination was not reduced when compared with that found after insemination directly into the oviducts, indicating a negligible contribution of peritoneal exposure to this process. Spermatozoa were not phagocytosed in the oviducts, but rather descended to the uterus at the same time as the developing embryos or degenerating eggs, the sperm flagellum usually being separated from the head by this stage.     

The effect of sperm number on fertility in blue fox vixens (Alopex lagopus ) artificially inseminated with frozen silver fox (Vulpes vulpes ) semen

During the breeding seasons of 1989 and 1990, a total of 617 blue fox vixens aged 1 to 6 years (mean +/- SEM, 2.6 +/- 0.1) were inseminated with frozen silver fox semen with either 150 million (n = 213, 1989 + 1990), 100 million (n=172, 1990), 75 million (n = 119, 1989) or 37.5 million (n = 113, 1989) spermatozoa per insemination. Two intrauterine inseminations, each with an insemination volume of 1.0 ml, were performed at 24-hour intervals on the first and second days after maximum vaginal electrical resistance was measured. Conception rates were 87% (186 of 213) with 150 million spermatozoa per insemination, 85% (146 of 172) with 100 million, 77% (91 of 119) with 75 million and 68% (77 of 113) with 37.5 million. The mean numbers of cubs per litter +/- SEM for the four groups were 7.6 +/- 0.2 (168 registered litters), 7.5 +/- 0.3 (115 litters), 6.4 +/- 0.4 (86 litters) and 6.4 +/- 0.4 (75 litters). A negative effect on both the conception rate and mean litter size at whelping was observed with decreasing sperm numbers (conception rate percentage: p = 0.0001, Chi-square, litter size: p = 0.02, Kruskal-Wallis Test). Only the two larger numbers of spermatozoa gave litter sizes comparable to those obtained by artificial insemination (AI) with fresh semen.     

A retrospective study on the preserving capacity of a commercial boar semen extender

The objective of this study was to evaluate the preserving capacity of a commercial, long-term boar semen extender beyond 4 days in terms of farrowing failure and total born per litter in sows and gilts. Data from 21 farms were subjected to logistic and linear regression analyses to assess the effect of parity (2-5, > 5 and gilts), wean-to-service interval (/= 6 days) and number of AI (1, 2, or 3) on the association between semen age (/=10 days) and fertility. As the semen age increased, the likelihood of farrowing failure increased and total born per litter decreased in sows and gilts. The effect of semen ageing on farrowing failure was more pronounced in sows than in gilts as in the latter it became significant only after 8 days. The effect of semen ageing on total born per litter was similar in both sows and gilts. A lower parity and wean-to-service interval were associated with a reduction in farrowing failure and increase in total born per litter in sows. Increasing the number of inseminations up to two was beneficial in reducing farrowing failure in sows and gilts. A third insemination increased the likelihood of farrowing failure in sows. The number of total born per litter in sows increased with number of inseminations and the effect was not significant in gilts.     

Effect of the time of artificial insemination with frozen-thawed or fresh semen on embryo viability and early pregnancy rate in gilts

The aim of the present study was to evaluate the effect of artificial insemination time (before or after ovulation) using either fresh or frozen-thawed boar semen on embryo viability and early pregnancy rate. Seventy-seven prepubertal crossbred (Landrace x Large White x Duroc) gilts were inseminated in 4 treatments. Artificial inseminations were performed 6 h either after (A) or before (B) ovulation using frozenthawed (A-frozen, n = 19; B-frozen, n = 19) or fresh semen (A-fresh, n = 21; B-fresh, n = 18). The gilts were induced to puberty by administration of 400 IU of eCG and 200 IU hCG (sc) followed by 500 IU of hCG (sc) 72 h later. Ovulation was predicted to occur 42 h after the second injection. All animals were slaughtered 96 h after AI. Embryos were collected and classified as viable (5- to 8-cells, morulae, compacted morulae and early blastocysts) and nonviable (fragmented, degenerated and 1- to 4-cell embryos). The total embryo viability rate was: 64.3% (A-frozen), 54.2% (A-fresh), 76.0% (B-frozen), 91.9% (B-fresh); (A-fresh vs B-fresh, P = 0.018; A-frozen vs B-frozen, P = 0.094). It was observed that AI before ovulation resulted in a higher percentage of total viable embryos than AI after ovulation (P = 0.041). The early pregnancy rate, defined as presence of at least one viable embryo, was 78.9, 80.9, 84.2 and 94.4% for A-frozen, A-fresh, B-frozen, B-fresh, respectively. There was no significant difference in the early pregnancy rate among groups. In conclusion, there was a detrimental effect upon total embryo viability rate when AI was performed after ovulation with either frozen-thawed or fresh semen. The total embryo viability rate and the early pregancy rate were not affected by AI with either frozen-thawed or fresh semen regardless of the time of AI.     

A comparison of reproductive characteristics of boars generated by somatic cell nuclear transfer to highly related conventionally produced boars

This study compares the reproductive performance of boars produced by somatic cell nuclear transfer versus conventional breeding. Two different genotypes were selected for comparison: terminal cross line 1 (TX1) and terminal cross line 2 (TX2). The boars selected for comparison from TX1 were three cloned boars, produced by somatic cell nuclear transfer and the conventionally produced progenitor of the clones. The boars selected for comparison from TX2 were a cloned boar produced by somatic cell nuclear transfer and two conventionally produced half sibling boars that were offspring of the progenitor of the clone. Semen from each boar was collected, extended, evaluated and shipped offsite. Upon arrival, the semen was reevaluated and utilized for artificial insemination of 89 commercial gilts, at least 12 gilts per boar, producing 625 piglets. Pregnancy rates were determined at day 30 and 110 of gestation; and farrowing rate and gestation length were recorded. Differences were observed in some of the semen characteristics analyzed with the clones usually possessing superior semen quality to the control, this likely being a result of age differences amongst the clones and controls. Additionally no differences were noted between the clones and controls (progenitor) or between individual boars within genetic line for pregnancy rates, gestation length or any of the litter parameters examined between the clones and controls. These data further support previous reports with limited numbers that the reproductive capabilities of cloned boars are equal to that of conventionally produced boars.     

Impact of a novel inactivated PRRS virus vaccine on virus replication and virus-induced pathology in fetal implantation sites and fetuses upon challenge

Preventing congenital infection is important for the control of porcine reproductive and respiratory syndrome (PRRS). Recently, in our laboratory, an inactivated porcine reproductive and respiratory syndrome virus (PRRSV) vaccine has been developed. Promising results in young pigs encouraged us to test the vaccine potency to prevent congenital infection. In the present study, the performance of this experimental inactivated vaccine was investigated in pregnant gilts. An advanced protocol was used to test the PRRSV vaccine efficacy. This protocol is based on recent insights in the pathogenesis of congenital PRRSV infections. Three gilts were vaccinated with an experimental PRRSV 07V63 inactivated vaccine at 27, 55, and 83 days of gestation. Three unvaccinated gilts were included as controls. At 90 days of gestation, all animals were intranasally inoculated with 10⁵ tissue culture infectious dose 50 (TCID₅₀) of PRRSV 07V63. Twenty days postchallenge animals were euthanized and sampled. The vaccinated gilts quickly developed virus neutralizing (VN) antibodies starting from 3 to 7 days postchallenge (1.0 to 5.0 log₂). In contrast, the unvaccinated gilts remained negative for VN antibodies after challenge. The vaccinated gilts had shorter viremia than the control gilts. Gross pathology (mummification) was observed in 8% of the fetuses from vaccinated gilts and in 15% of the fetuses from unvaccinated gilts. The number of fetuses with severe microscopic lesions in the fetal implantation sites (a focal detachment of the trophoblast from the uterine epithelium; a focal, multifocal, or full degeneration of the fetal placenta) was lower in the vaccinated (19%) versus unvaccinated (45%) gilts (P < 0.05). The number of PRRS-positive cells in the fetal placentae was higher in unvaccinated versus vaccinated gilts (P < 0.05). In contrast, the number of PRRS-positive cells in the myometrium/endometrium was higher in vaccinated versus unvaccinated gilts (P < 0.05). Fifty-seven percent of the fetuses from the vaccinated gilts and 75% of the fetuses from the unvaccinated gilts were PRRSV-positive. In conclusion, implementation of the novel experimental inactivated PRRSV vaccine primed the VN antibody response and slightly reduced the duration of viremia in gilts. It also reduced the number of virus-positive fetuses and improved the fetal survival, but was not able to fully prevent congenital PRRSV infection. The reduction of fetal infection and pathology is most probably attributable to the vaccine-mediated decrease of PRRSV transfer from the endometrium to the fetal placenta.