Heritability of subclinical endometritis in Norwegian Red cows.

Subclinical endometritis (SCE) is highly prevalent in dairy cows, causing negative effects on reproductive outcomes and the producer economy. Genetic selection for animals with better resilience against uterine disease should be prioritized due to both sustainability and animal welfare. Therefore, the aim of the present study was to estimate the heritability of SCE in the Norwegian Red (NR) population. Moreover, future perspectives of the condition as a fertility phenotype for breeding are discussed. A total of 1,642 NR cows were sampled for SCE at the time of artificial insemination, using cytotape. The percentage of polymorphonuclear cells (PMN) in each sample was established by cytology, through the counting of 300 PMN and epithelial cells. The mean percentage of PMN was 5%. Different trait definitions were examined, and SCE was defined as binary traits, based on the following cut-off levels of PMN: Cyto0 = PMN  >0, Cyto3 = PMN  >3%, Cyto5 = PMN  >5%, Cyto10 = PMN  >10%, and Cyto20 = PMN  >20%.  The mean ranged from 0.07 (Cyto20) to 0.59 (Cyto0). We also analyzed PMN as a continuous variable using percent PMN. Information on the animals and herds was obtained from the Norwegian Dairy Herd Recording System. The pedigree of cows with data included a total of 24,066 animals. A linear animal model was used to estimate the heritability. The only trait definition that had an estimated genetic variance larger than the standard error was Cyto5, with an estimated heritability of 0.04. For all other definitions, the genetic variance was not significantly different from zero. A cut-off level of 5% PMN has been established as a general threshold for the definition of SCE in earlier literature. The standard errors of the estimated variance components were relatively large, and results should be interpreted with caution. However, the current study indicates that SCE is heritable at a similar level to that of clinical endometritis and metritis, and has potential as a future fertility phenotype to be used for breeding purposes. A more feasible method to diagnose SCE is needed to establish larger data sets.

Prevalence, risk factors, and effects on fertility of cytological endometritis at the time of insemination in Norwegian Red cows.

The present study aimed to assess the occurrence of cytological endometritis (CYTO), a nonsymptomatic inflammation of the endometrium, at first artificial insemination (AI) postpartum in Norwegian Red cows. Further, risk factors for CYTO manifestation and its effect on reproductive success and late embryo loss were evaluated. In total 1,648 cows located in 116 herds were included in the study. On mainly spontaneous estrus, endometrial cytology samples were collected using a cytotape technique, and a total of 300 representative epithelial cells and polymorphonuclear neutrophils (PMN) were counted at 400× magnification. Vaginal mucus obtained by Metricheck (Simcro) and body condition score were recorded. Milk samples for progesterone analysis were collected at AI and 21 d later. Pregnancy was diagnosed by rectal palpation or analysis of pregnancy-associated glycoproteins. Based on the constructions of a receiver operator characteristics curve, the cut-off level for PMN defined as CYTO was set to 3.0%, representing the level at which the PMN occurrence affected pregnancy outcome, with the highest summation of sensitivity (32.4%) and specificity (74.9%). Three logistic models with herd included as random factor were constructed. The outcome for the first model was the likelihood for CYTO based on the endometrial samples, in the second model pregnancy to first AI, and in the third model embryo loss. The proportion of CYTO was 28.0% (461/1,648). The average interval in days to first AI was 71.7 d (standard error ± 0.7) and the overall pregnancy incidence to first AI was 59.8% (866/1,449). The likelihood for CYTO at first AI was associated with AI personnel, calving to first AI interval, vaginal mucus characteristics, amount of red blood cells in sample, season, and barn type. Pregnancy to first AI was lower in CYTO-positive cows (odds ratio = 1.51, confidence interval = 1.17-1.94). Other factors affecting pregnancy to first AI were AI personnel, test day milk yield, barn type, and obstetrical conditions or fertility treatments before first AI. The proportion of late embryo loss and abortion was 8.6% (82/948) and 2.8% (24/866), respectively. Late embryo loss was associated with treatment against fertility disorders before first AI, but not associated with CYTO. Overall, our results suggest that even if Norwegian Red cows show a fairly high prevalence of CYTO in the endometrium at first AI, it does not seem to have a major effect on the reproductive performance. The Norwegian Red breeding program has emphasized fertility and health for decades, and a genetically advantageous uterine immunology might be one of the preserved mechanisms.

The relationship between post-thaw sperm DNA integrity and non-return rate among Norwegian cross-bred rams.

With the aim of investigating the relationship between sperm DNA integrity and non-return rate (NRR) among Norwegian cross-bred rams, semen from 15 individuals was examined by flow cytometry. Sperm Chromatin Structure Assay (SCSA) quantifies the proportion of spermatozoa with denatured DNA after in situ acid treatment, and the four parameters % DFI, % HDS, MEAN DFI and SD DFI are all different measures of DNA denaturation and maturation. Field fertility, reported as NRR 25 days after insemination was based on all inseminations from a large-scale breeding programme and supplied by the Norwegian Association of Sheep and Goat Farmers. From each ram, four straws from four different weeks of the breeding season were analysed, and the associations between 25-day NRR and the mean of the four SCSA parameters were tested using a logistic regression model. The results revealed no association between fertility and % DFI or % HDS, while SD DFI and MEAN DFI showed a significant negative association with NRR. Further, the SCSA values varied significantly between ejaculates within ram among some of the rams in the study. However, no significant association was seen between these intra-individual differences in sperm DNA integrity and NRR. In conclusion, this study suggests an association between sperm DNA integrity and NRR for rams. However, further research must be conducted to confirm these findings and determine whether sperm DNA assessments can be applied to predict ram fertility.

Ewe breed differences in cervical anatomy and cervicovaginal mucus properties: An international study.

In sheep, cervical artificial insemination (AI) involves depositing semen at the cervical opening, as it is not possible to traverse the cervix due to its complex anatomy. However, internationally this method yields low pregnancy rates when frozen-thawed semen is used. An exception to this is in Norway, in which vaginal deposition of frozen-thawed semen to a natural estrus yields pregnancy rates around 70%. As the cervix and its secretions are the principal factors influencing sperm transport to the site of fertilization the aim of this study was to characterise the differences in the cervical anatomy as well as the cervicovaginal mucus properties of six European ewe breeds across three countries known to have differences in pregnancy rates following cervical AI with frozen-thawed semen. These were Suffolk and Belclare in Ireland, Fur and Norwegian White Sheep (NWS) in Norway and Ile de France and Romanov in France (n = 28-30 ewes/breed). Cervicovaginal mucus was collected at the follicular and luteal phases of both a synchronized and natural cycle and assessed for mucus weight, viscosity and colour. The anatomical characteristics of the cervix (length of the cervix, number of cervical rings and the appearance of the external os) were assessed post-mortem. There was a type of the cycle by ewe breed interaction represented by no differences in mucus production between ewe breeds at the natural cycle for both the follicular and luteal phases of the cycle. However, there were differences between ewe breeds at the synchronized cycle (P < 0.05). Belclare had the lowest mucus production at the follicular phase while NWS had the lowest amount of mucus at the luteal phase of the synchronized cycle. Overall, across all ewe breeds, mucus production was higher at the follicular than at the luteal phase (P < 0.05). Despite reports of Suffolk and NWS having the most divergent pregnancy rates following cervical AI with frozen-thawed semen, both breeds had the lowest overall mucus viscosity at the follicular phase of both types of cycle with no differences between both ewe breeds (P > 0.05). The length of the cervix, number of cervical rings and the external os type were affected by ewe breed (P < 0.05). Suffolk ewes had longer cervices but lower number of cervical rings than NWS and Fur ewes (both with higher pregnancy rates). In conclusion, while mucus production and mucus viscosity was affected by breed, these changes are not consistent with the known differences between ewe breeds in their pregnancy rates following cervical AI with frozen-thawed semen.

Valproate affects reproductive endocrine function, testis diameter and some semen variables in non-epileptic adolescent goat bucks.

Valproate (VPA) is a major antiepileptic drug with a broad spectrum of antiepileptic activity. There is, however, increasing concern about the possible effects of VPA on reproductive endocrine function. This study investigated the effects of valproate, on the endocrine and reproductive system of adolescent, non-epileptic, goat bucks. Nine goat bucks were orally treated with 62.5mg/kg valproate twice daily from 2 to 10 months of age in order to sustain therapeutic plasma concentrations of between 300 and 600 micromol/l. Seven bucks served as controls. Body weights and testicular diameters were recorded. Blood samples were collected for measurement of luteinising hormone (LH), follicle stimulating hormone (FSH) and testosterone three times weekly until sacrifice at approximately 40 weeks of age. Conventional reproductive endpoints were recorded and flow cytometric (FCM) analyses of spermatogenesis, including the sperm chromatin structure were conducted. Valproate-treated bucks had on average a higher body weight, but a lower testis diameter than controls. No significant differences were found for plasma FSH in comparison to controls. Valproate-treated bucks differed significantly from the control group by showing lower plasma concentrations of LH and testosterone and a later onset of puberty. A significantly higher proportion of sperm from valproate-treated bucks showed abnormal chromatin, demonstrating a harmful effect on DNA from valproate treatment. These results demonstrate that valproate was able to induce reproductive effects in goat bucks related to the hypothalamic-pituitary-axis, as well as to the testes.

Artificial insemination with frozen semen in dogs: a retrospective study of 10 years using a non-surgical approach.

From 1994 to 2003, a total of 526 bitches of 99 different breeds were artificially inseminated in 685 estrus cycles with domestic (n = 353) or imported (n = 332) frozen-thawed semen from 368 males. The overall whelping rate was 73.1% and mean (+/- S.E.M.) litter size 5.7 +/- 0.1 pups. The whelping rate was higher after intrauterine insemination (75.0%; n = 665) than after intravaginal insemination (10.0%, n = 20; P < 0.05). Insemination at the optimal time resulted in a higher whelping rate (78%, n = 559; P < 0.01) and larger litter size (5.8 +/- 0.2; P < 0.05) than inseminations performed late or too late (55.7% and 4.5 +/- 0.5, n = 61). Two inseminations (n = 384) yielded a higher whelping rate (P < 0.05) and mean litter size (P < 0.01) than one insemination (n = 241), 78.1% and 6.0 +/- 0.2 and 70.5% and 5.1 +/- 0.2, respectively. For inseminations performed at the optimal time, however, the whelping rate was not significantly different for bitches inseminated twice (79.3%, n = 358) versus once (76.8%, n = 168), but the litter size was larger (6.0 +/- 0.2 and 5.3 +/- 0.3). Semen classified as of poor quality (progressive motility < 50% or percentage abnormal sperm > 20%) resulted in a lower whelping rate (P < 0.01) than semen classified as of good quality (progressive motility > or = 50% and percentage abnormal sperm < or = 20%), 61 and 77%, respectively. Small breeds (n = 50) had a smaller litter size (3.9 +/- 0.3; P < 0.01) than larger breeds (medium [5.7 +/- 0.3, n = 94], large [5.9 +/- 0.2, n = 295] or giant breeds [6.1 +/- 0.5, n = 62] [P < 0.01]). Bitches older than 6 years had a lower whelping rate (68.2%) than younger ones (77.0%; P < 0.05). The duration of pregnancy was longer (P < 0.01) for bitches with a litter size of < 3 pups (61.7 +/- 0. 4 days, n = 30) than for bitches with larger litters (60.5 +/- 0.1 days, n = 177). These results show the potential of transcervical intrauterine insemination for routine artificial insemination in dogs. The results with frozen semen inseminations were optimised by inseminating bitches < or = 6 years old 2 and 3 days after ovulation with semen of good quality from males < or = 8 years old.

In vitro reproductive toxicity of polychlorinated biphenyl congeners 153 and 126.

This study was conducted to investigate the applicability of an in vitro technique for maturation, fertilization, cleavage, and growth to blastocysts of bovine oocytes to investigate reproductive toxicologic effects. During maturation, the oocytes were exposed to the di-ortho-substituted PCB congener 2,2',4,4',5,5'-CB (PCB 153) in the three concentrations 0.84 ng/mL, 8.4 ng/mL, and 84 ng/mL or to the non-ortho-substituted PCB congener 3,3'4,4',5-CB (PCB 126) in the three concentrations 1.006 pg/mL, 10.06 pg/mL, and 100.6 pg/mL and compared with control groups. PCB 153 had no effect on maturation but resulted in a reduced proportion of oocytes that cleaved at the highest concentration. There were no differences in blastocyst development among groups. PCB 126 resulted in a reduction in maturation percentage at the highest concentration and in blastocyst development at all concentrations. These results demonstrated adverse effects of PCB congeners on bovine oocytes and showed that this system can be used to evaluate toxic effects on oocytes and preimplantation-stage embryos.

Effects of non-steroidal anti-inflammatory drugs in the maturation and fertilization media on bovine oocytes.

In the present investigation the effects of 2 non-steroidal anti-inflammatory drugs commonly used in veterinary practice, flunixin-meglumin (FM) and phenylbutazone (PB), were studied. These drugs were added to the in vitro maturation medium of bovine oocytes. The effect of FM on in vitro fertilization was also tested. The results indicated that in vitro concentrations corresponding to maximal concentrations of FM in the plasma after therapeutic doses did not influence the in vitro maturation or fertilization rates of oocytes. However, doses higher than physiologic concentrations resulted in significant decreases in oocyte maturation and complete failure of fertilization. Concentrations of PB corresponding to concentrations commonly found in the plasma after therapeutic doses resulted in a significant decrease in the number of matured oocytes.

In vitro maturation and fertilization of oocytes from Norwegian semi-domestic reindeer (Rangifer tarandus ).

Reindeer oocytes were submitted to in vitro maturation, fertilization and culture (IVM,IVF,IVC) using the established procedures for bovine in vitro embryo production. The study was conducted outside the main breeding season. Semen was collected from epididymides immediately after slaughter, and was diluted in Tris-fructose-citric acid extender containing 6% glycerol and 20% egg-yolk and then frozen in liquid nitrogen. Following 24 h of maturation, cumulus expansion was complete, and 71% of the oocytes reached Metaphase II (MII), with extrusion of the first polar body. Of the remaining oocytes, 22% were at the germinal vesicle stage (GV), 2% at diakinesis and 5% at Metaphase I (MI). The percentages of fertilization and cleavage were 36.0 and 31.8%, respectively. Two of the fertilized oocytes developed to the morula stage after 7 d of culture.

Effect of bovine sperm separation by either swim-up or Percoll method on success of in vitro fertilization and early embryonic development.

The objectives of these experiments were to characterize separation of frozen-thawed bovine spermatozoa on a Percoll gradient and then to compare sperm separation by either a swim-up or Percoll gradient procedure for the ability of spermatozoa to fertilize oocytes in vitro. The Percoll gradient was a 45 and 90% discontinuous gradient. Initial experiments found that centrifugation of semen on the Percoll gradient for 15 min at 700 g was sufficient to obtain optimal recovery of motile spermatozoa. Most of the nonmotile spermatozoa were recovered at the interface of the 45 and 90% Percoll layers, while the motile spermatozoa were primarily in the sperm pellet at the bottom of the gradient. When frozen-thawed semen from each of 7 bulls was separated by swimup, a mean +/- SEM of 9% +/- 1 of the motile spermatozoa were recovered after the procedure. In contrast, more spermatozoa were recovered after Percoll gradient separation (P < 0.05), with 40% +/- 4 of the motile spermatozoa recovered. The effect of separation procedure on in vitro fertilization found swim-up separated spermatozoa penetrated a mean +/- SEM of 74% +/- 5 of the oocytes, while fewer oocytes were penetrated by Percoll separated spermatozoa at 52% +/- 8 (P < 0.05). There was no effect of the separation procedure on the rates of polyspermy as measured by sperm/penetrated ova, with a mean +/- SEM of 1.25 +/-.09 for swim-up separated spermatozoa and 1.14 +/-.07 for Percoll separated spermatozoa (P>0.05). A carry over of Percoll into the fertilization medium with the Percoll separated spermatozoa was found not the cause for the decreased penetration of oocytes by these spermatozoa. In 2 of 3 bulls tested, the decreased penetration of oocytes by Percoll separated spermatozoa could be overcome by increasing the sperm concentration during fertilization from 1 x 10(6) to 5 x 10(6)/ml. When development of embryos fertilized by either swim-up or Percoll separated spermatozoa was compared for the semen from 2 bulls, a difference in cleavage rate was found in favor of swim-up separated spermatozoa (P < 0.05), but there was no effect of separation procedure on development (Day 7) to the morula + blastocyst or blastocyst stage (P>0.05). The disadvantages of the Percoll procedure could easily be overcome and the procedure was faster and yielded a six-fold greater recovery of motile spermatozoa than the swim-up method.

Membrane alterations in bull spermatozoa after freezing and thawing and after in vitro fertilization.

Membrane alterations in bull spermatozoa after freezing and thawing and after the process of in vitro capacitation and fertilization were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Even if the majority of the spermatozoa exhibited intact membranes after freezing and thawing (90%), one could distinguish between 3 types of membrane defects depending of the different structures involved. The first type showed loss of plasmalemma over the entire acrosome. In the second category the anterior part of the outer acrosomal membrane exhibited a pronounced extension, but was covered by a partly intact plasmalemma. The last category consisted of spermatozoa with extensive vesiculation and disruption of plasmalemma and the outer acrosomal membrane. This type of defect could not easily be distinguished from a true acrosome reaction. The cumulus cells showed an active phagocytosis of both intact and acrosome reacted spermatozoa.

A serologic study of canine herpes virus-1 infection in the Norwegian adult dog population.

Canine herpes virus-1 (CHV1) causes a fatal hemorrhagic disease in neonatal puppies and is associated with reproductive problems in female dogs. This serologic study was conducted to assess the seroprevalence of CHV1 infection in Norway. Blood samples were collected from clinically healthy dogs (n = 436) one yr of age and older of both genders, supplied by four small animal clinics (A, B, C and D) in different parts of the country. The immunoperoxidase monolayer assay was used for testing of CHV1 antibodies. Serum titers were recorded as the reciprocal value of the highest dilution producing specific cell staining. Titers equal to or above 80 were considered positive for exposure to CHV1. In total, 80.0% of the dogs had titers ≥80 and were classified as positive. Mean age for seronegative dogs was 4.7 yrs (95% CI 4.1-5.4) and for seropositive dogs 5.0 yrs (95% CI 4.7-5.4). Of the dogs, 32.8% displayed a weakly positive titer of 80, whereas 41.5 and 5.7% fell into the moderately (titer 160 and 320) and strongly (titer ≥640) positive categories, respectively. No association was demonstrated when comparing CHV1 antibody titers to gender or reproductive parameters like previous matings, pregnancies, births or number of puppies born. Age, visit in foreign countries and clinic explained together 78% of the variation in antibody titer categories. The percentage of positive samples differed significantly between the four clinics (A 98%, B 58.5%, C 74.6%, D 89.5%). A reasonable explanation for this finding has not been established. No information about an ongoing outbreak of CHV1 infection was available. In conclusion, this study strongly indicates that CHV1 infection is endemic in the dog population of Norway. There are significant differences in seroprevalence between geographic regions in the country.

Artificial insemination with frozen semen in dogs: a retrospective study.

In a retrospective study, from 1994 to 1998, of inseminations with frozen semen in dogs, a total of 312 bitches of 70 different breeds were inseminated with imported (n = 183) or domestic (n = 129) semen. The overall whelping rate was 70% and mean (+/- SEM) litter size was 5.3 +/- 0.2 pups. The whelping rate was higher after intrauterine insemination (71%; n = 305) than after intravaginal insemination (29%; n = 7; P < 0.05). Timing of insemination was crucial; timing classified as optimal resulted in a higher whelping rate and larger litter size (P < 0.05) than did timing classified as early, late or too late. In the too late category, none of the bitches (n = 5) whelped. For optimal timing, whelping rate and mean (+/- SEM) litter size were 76% (n = 252) and 5.6 +/- 0.2, for early 33% (n = 6) and 1.5 +/- 0.5, and for late 47% (n = 19) and 2.8 +/- 0.7. Two inseminations yielded a higher whelping rate (P < 0.05) and greater mean litter size (P < 0.05) than that of one insemination, 77% and 5.6 +/- 0.3, and 60% and 4.6 +/- 0.3, respectively. However, the results obtained after one insemination were poorer partly because of an over-representation of late insemination in this group. Semen classified as of poor quality (progressive motility < 50% or percentage of abnormal spermatozoa > 20%) gave a lower whelping rate (53%) than did semen of medium (progressive motility = 50%) or good quality (progressive motility > 50% and percentage of abnormal spermatozoa < 20%), which gave whelping rates of 76 and 74%, respectively (P < 0.05). The mean litter sizes were not significantly different. Eighty-two per cent of bitches (120 of 147) inseminated twice into the uterus at a time classified as optimal with frozen semen of good or medium quality whelped. The mean (+/- SEM) litter size was 5.6 +/- 0.3 pups in this group. These results show the potential of transcervical intrauterine insemination for routine artificial insemination in dogs.

Fertilization in vitro of oocytes matured in vivo in the blue fox (Alopex lagopus).

Six unmated blue fox vixens were killed 2-3 days after peak vaginal electrical resistance. Measurements of luteinizing hormone (LH) showed that this corresponded to a time period of 6-10 days after the preovulatory LH peak in these vixens. A total of 63 ova were collected from the oviducts of the vixens, and 45 of the ova were used for study of fertilization in vitro. The ova were placed in 50 microliter droplets of fertilization medium and inseminated with 15,000-45,000 frozen-thawed silver fox spermatozoa that had been separated by swim-up technique, except for nine ova that served as controls for parthenogenesis. Only two of the 36 inseminated ova, both from a vixen killed 6 days after the preovulatory LH peak and inseminated with 15,000 spermatozoa, developed past the four-cell stage. One reached the morula stage 144 h after insemination. Despite a low success rate, the present experiment shows that fox ova matured in vivo may be fertilized and undergo initial embryonic development in vitro.

Seasonal changes in spermatogenic activity and in plasma levels of FSH, LH and testosterone, and the effect of immunization against inhibin in the male silver fox (Vulpes vulpes).

The cellular composition of the silver fox testis assessed by DNA flow cytometry and histological analysis exhibited marked circannual alterations. The proportion of haploid cells increased from late October to the breeding season in February, while that of diploid cells decreased and that of tetraploid cells fluctuated during the same period. Towards the end of March these changes were reversed. The seasonal variations in testicular histology paralleled the changes in distribution of cells from the different DNA populations. In August, 69% of the tubules contained spermatogonia as the only type of germ cell, while the remaining 31% also contained a few primary spermatocytes. In late October more than 50% of the tubules contained spermatocytes, and during the period of further activation from early December-February the seminiferous epithelium included round and/or elongated spermatids as well. In February, all tubules contained complete associations of germ cells, whereas in late March tubules with spermatogonia only and spermatogonia together with a few spermatocytes reappeared. In May, only such tubules could be found indicating total regression. Plasma concentrations of FSH and LH increased from early November, both gonadotrophins reaching maximum levels in December or early January, and then both declined during the second part of January, immediately prior to the actual breeding season. LH values showed a few smaller peaks in the beginning of June, whereas FSH levels were generally low until the next period of testicular reactivation. Testosterone concentrations were also low during most of the year but rose in November and December to reach a peak in January and a second peak in June. In animals immunized against inhibin the distribution of haploid, diploid and tetraploid cells did not deviate to any great extent from that in the controls, except in March when the immunized males had a markedly lower proportion of tetraploid cells, and in May, when they had a distinctly higher proportion of haploid cells. These findings were partly reflected by the histology. In the immunized animals, plasma FSH levels started to increase at approximately the same time but peaked higher and remained elevated almost 1 month longer than in the controls, whereas both the rise and decline in LH levels generally coincided with the variations in these animals, but the values were mostly higher. The testosterone profiles were similar to those in the controls except that the maximum values were also usually higher.