Periovulatory endocrinology and oocyte maturation in unmated mature blue fox vixens (Alopex lagopus)

Nine of 10 mature blue fox vixens (Alopex lagopus) in spontaneous oestrus ovulated approximately 2 days after the preovulatory increase in luteinizing hormone (LH). Plasma concentrations of follicle-stimulating hormone and progesterone increased simultaneously with the LH peak, whereas oestradiol-17 beta peaked 1 day previously. In the tenth vixen, an LH peak was not observed, and neither visible follicles nor corpora lutea were found in the ovaries 6 days after peak vaginal electrical resistance. Eggs were ovulated as primary oocytes, but oocyte maturation was initiated within the day of ovulation (2 days after the LH peak). Within the next 2 days (3-4 days after the LH peak) the first polar body was extruded, and the cumulus mass was completely dissociated from the zona pellucida. The interval between the preovulatory LH peak and initiation of the final oocyte maturation is thus considerably longer in the blue fox than for example in the cow (48-72 h compared with 9-12 h). This suggests that the relationship between these two events is somewhat different in the blue fox.     

Plasma Prolactin during the Luteal Phase and Pregnancy in Non-Parturient and Parturient Blue Fox Vixens

Abstract

Plasma prolactin secretion during the luteal phase and pregnancy was studied in 11 mated but non-parturient and 26 parturient blue fox vixens. Prolactin was measured in blood plasma once or twice a week using a heterologous double-antibody radioimmunoassay. Data for all females were fitted with an animal model. In both groups of females, prolactin concentrations increased slowly during the early post mating period. For the parturient vixens the prolactin values increased further until parturition, whereas there was only a slight increase in the non-parturient vixens. Statistically significant differences (p < 0.05) were observed in prolactin release between the non-parturient and parturient animals from day 36 after mating. A possible role of prolactin may exist in the luteotrophic complex maintaining pregnancy in blue fox vixens, because higher levels of plasma prolactin and progesterone appeared in the parturient vixens compared to the non-parturient during the second half of gestation.     

Cholinesterase activities in uterus of normal and fenchlorphos treated blue foxes (Alopex lagopus) during various reproductive states

The uterine acetylcholinesterase and total cholinesterase (acetylcholinesterase plus butyrylcholinesterase) activities in normal and fenchlorphos treated blue fox vixens were determined during various reproductive states.AChE and Total-ChE of non-medicated vixens in oestrus were about one half of those in anoestrus. In pregnant uteri (luteal phase) the activities were 25 % and 30% compared to anoestrus.In vixens given 100 mg/kg fenchlorphos for 3 weeks during anoestrus, the remaining activity of AChE in uterus were in average 37%. Pregnant and non-pregnant vixens in the luteal phase medicated prior to mating and during time of implantation, displayed AChE activities which were only moderabely reduced (remaining activities 83% and 72% compared to medicated animals in anoestrus: remaining activity 37%).Plasma ChE-activity increased during pregnancy in the controls while enzyme activity was strongly reduced in animals given 100 mg/kg fenchlorphos daily through the whole pregnancy.It was concluded that the previous reported embryotoxic effect of fenchlorphos in the blue fox did not seem to be directed towards the moderate inhibition of the uterine cholinesterases.     

Ultrastructural studies of blue fox spermatozoa

The fine structure of epididymal and ejaculated spermatozoa from blue fox is analyzed by electron microscopy. The result of this investigation seems to indicate that the blue fox spermatozoon is of the same type as that of the dog. The apical body appears, however, to have a rather characteristic shape and to be more well-developed than found in sperm cells from the usual domestic animals.The other structures studied in the different parts of the blue fox spermatozoon including the head, neck and flagellum displayed the same principal characteristics as those in the sperm cells of other domestic species.In a few cases double development of the middle piece could be observed.     

狐狸脑炎病毒的分离鉴定

通过ＭＤＣＫ传细胞从黑龙江某狐场疑似狐狸脑炎病狐的肝脏中分离到对本动物具有较强致病能力的强毒株,定名为ＦＥＶ－Ｈ。经系统鉴定,并与已知国内分离毒株狐狸脑炎病毒ＦＥＶ－８８０１,狐喉气管炎病毒ＦＡＶ－２比较,证实为狐狸脑炎病毒,属犬１型腺病毒（ＣＡＶ－１）。     

The persistence of rabies virus antibodies in the sera of fox cubs

The persistence of maternal antibodies transfer from rabies-immune vixens to their fox cubs was studied. Eight vixens (Vulpes vulpes) were vaccinated 1 month before pregnancy with Lysvulpen vaccine for oral vaccination of foxes. Twenty-one were foxes born at the first half of April. The geometrical mean titre of rabies neutralizing antibodies of fox cubs sampled in May was 1.31 IU/ml and has dropped successively to 0.54 IU/ml in June samples and to 0.18 IU/ml in July samples. It has been proven that the duration of rabies maternal antibodies in fox cubs was limited to 2 months after birth.     

Characterization of biological and antigenic properties of raccoon dog and blue fox parvoviruses: a monoclonal antibody study

Parvovirus isolates from blue foxes and raccoon dogs were characterized by studying their haemagglutination properties, host range in vitro and antigenic structure. In all 3 characters, raccoon dog parvovirus resembled canine parvovirus (CPV), while blue fox parvovirus was similar to mink enteritis virus (MEV). Monoclonal antibodies (MAbs) were prepared against both viruses. Raccoon dog parvovirus, while resembling CPV, had a unique antigenic site which could be specified by MAbs. The pattern of MAbs prepared against blue fox parvovirus indicated that it is a member of Type 2 MEV.     

Plasma Progesterone during the Luteal Phase and Pregnancy in Parturient and Barren Blue Fox Vixens

Abstract

The variation in progesterone secretion during the luteal phase and pregnancy in blue fox vixens was analyzed. Progesterone was measured in blood plasma once or twice a week using radioimmunoassay. The material was allocated into three groups; five mated, but barren, blue fox vixens, six mated vixens with implantation zonès in the uterus, but no cubs at parturition, and 26 normally parturient vixens. The progesterone profiles for the three different groups of females showed a steady increase in progesterone immediately after mating. Maximum values were observed on days 8–12 of pregnancy. Then the progesterone levels decreased gradually until delivery around day 52. The levels of progesterone were found to be significantly different (P<0.05) between non-pregnant and pregnant females from day 22 after mating. The plasma progesterone level seems to be affected by the presence of conceptuses.     

Toxic effects of food-borne fluoride in silver foxes

Chronic ingestion of excessive amounts of fluoride from commercial fox food is associated with agalactia in vixens resulting in the starvation deaths of large numbers of kits in three fox herds. Evidence of infectious disease or poor management could not be found and a causal relationship between fluoride and high kit mortality is suggested.     

Humoral immune response in adult blue foxes (Alopex lagopus) after oral infection with Encephalitozoon cuniculi spores

Encephalitozoon cuniculi causes severe diseases in blue fox puppies. When pregnant vixens are infected, parasites are transmitted over the placenta to the unborn that subsequently develop encephalitozoonosis. Adult foxes themselves do not have signs of disease, but show antibody titres to E. cuniculi. The purpose of the present study was to gain information on the immune response in adult foxes after experimental infection. Sixteen foxes were infected orally with E. cuniculi spores, eight of them twice and 28 days apart. The two groups of animals showed elevated serological values in both the carbon immunoassay and in the ELISA. Elevated serological levels were recorded up to 1 year after the infection took place. The control group (n=8) remained serologically negative throughout the trial. The results of the study showed that blue foxes could be seropositive for at least a year after oral infection with E. cuniculi.     

Ovarian and testicular function in the blue fox (Alopex lagopus) after oral administration of fenchlorphos during the breeding season

The possible effect of fenchlorphos, 0-0-dimethy1-0-(2.4.5-trichlorophenyl) phosphorothioate, upon the reproductive endocrinology in blue foxes (Alopex lagopus) was investigated. Five females were administered fenchlorphos orally at a dose of 100 mg/kg daily from 10 days before oestrus and up to the 21st day of gestation. This dose represents the therapeutic dose for the treatment of sarcoptic mange. Blood samples were collected for the analyses of progesterone, oestradiol-17β and luteinizing hormone (LH) in plasma. The vixens were ovario-hysterectomized on day 23, except 1 animal in the control group which was operated on day 17. Additionally, sperm quality and mating performance in 3 male blue foxes, which were administered 100 mg/kg fenchlorphos daily during the first 3 weeks of the mating season, were examined.Pregnancy was recorded in 2 medicated and 4 control animals. No pathological changes were observed in the uterus and the ovaries. The plasma concentrations of the hormones were similar to those obtained from the control group. No evidence of any disturbances concerning spermatogenesis in the males was observed. However, their libido appeared to be reduced. None of the males achieved a mating during and after the period of medication.     

Variation between ranch blue fox populations in cranial form

The aim of this study was to describe the differences in cranial size and shape that occur between different farmed blue fox populations within and between countries. The skulls were obtained at the pelting time from three Finnish, one Estonian, one Norwegian and seven Canadian farms. The material was subjected to a principal component (PC) analysis for each sex. The first PC-factor explained about 50% of variation. It was identified as the size factor; it discriminated Finnish blue foxes at one end and Nova Scotia foxes at the other end of the scale. The second PC-factor explained about 10% of variation in skull morphology but failed to discriminate the populations. The third factor, which was dominated by interorbital width, discriminated Nova Scotia foxes from the other populations. PC-factor 4 received its highest loading from the length of upper tooth row. This factor differentiated, although poorly, the Newfoundland fox populations, whether local or crosses between the local and the imported Finnish stock, from the others. The sexes were significantly different on most single parameters and the skulls of all farm populations were larger than those of wild Arctic foxes. However, there were also large differences in skull morphology between farms within one country. This shows that farmed blue foxes in different countries have not yet diverged into anatomically distinct populations.     

Embryonic development in the blue fox

Embryos from vixens at different stages of gestation were measured and photographed. Implantation was observed 16-18 days after breeding. Differentiation and the development of characteristic features were described and embryonic loss was studied in relation to number of corpora lutea.     

Risk aversion affects economic values of blue fox breeding scheme

The profit and production of an average Finnish blue fox farm was simulated using a deterministic bio‐economic farm model. Risk was included using Arrow‐Prat absolute risk aversion coefficient and profit variance. Risk‐rated economic values were calculated for pregnancy rate, litter loss, litter size, pelt size, pelt quality, pelt colour clarity, feed efficiency and eye infection. With high absolute risk aversion, economic values were lower than with low absolute risk aversion. Economic values were highest for litter loss (18.16 and 26.42 EUR), litter size (13.27 and 19.40 EUR), pregnancy (11.99 and 18.39 EUR) and eye infection (12.39 and 13.81 EUR). Sensitivity analysis showed that selection pressure for improved eye health depended strongly on proportion of culled animals among infected animals and much less on the proportion of infected animals. The economic value of feed efficiency was lower than expected (6.06 and 8.03 EUR). However, it was almost the same magnitude as pelt quality (7.30 and 7.30 EUR) and higher than the economic value of pelt size (3.37 and 5.26 EUR). Risk factors should be considered in blue fox breeding scheme because they change the relative importance of traits.     

Effect of evening primrose oil as food supplement on reproduction in the blue fox.

Addition of evening primrose oil (EPO) to a blue fox diet in the reproduction period was evaluated in an experiment with 2 groups, each of 12 male and 25 female blue foxes, regarding the effects on reproductive performance. The experiment was carried out as a field trial and the experimental period lasted from March 10 until the end of the mating season (males) or early July (females). During this period the control group was fed the standard diet of the farm and the experimental group was fed the same diet supplemented with 4.5 g EPO and 2.5 mg zinc sulphate per animal and day. An addition of 10 mg vitamin E per 500 mg EPO was made. The results were evaluated regarding male and female treatment effects. There was an increased rate of abortions in the EPO-group, but simultaneously a non-significant decrease in the frequency of barren females, resulting in a similar level of females without litters in both groups. A tendency for increased litter size in the EPO group was found, mainly as an effect of male treatment, which might indicate an effect on semen quality.     

Reproduction in farmed Silver fox vixens, Vulpes vulpes, in relation to own competition capacity and that of neighbouring vixens

SUMMARY: Reproductive performance in 34 one-year old and 5 two-year old farmed silver fox vixens was recorded and related to their competition capacity and that of neighbouring vixens. The vixens were tested for competition capacity at 5-7 months of age, and divided into high (HCC), medium (MCC) and low (LCC), according to their competition capacity score. After selection, they were placed together with neighbours as follows; HCC with LCC or HCC neighbours, MCC with MCC neighbours and LCC vixens with LCC, MCC, or HCC neighbours. The vixens had the same neighbours from October to the end of the reproductive season in June/July the following year and were separated from their neighbours by double wire netting only. Only small differences were found between the experimental groups in the number of cubs born. The HCC vixens with LCC neighbours weaned more cubs than any of the other vixens, including HCC vixens with other HCC vixens as neighbours. No LCC vixen weaned cubs unharmed if her neighbours were of higher competition capacity, but did so with other LCC vixens as neighbours. The study indicated that social factors significantly influence maternal behaviour in farmed silver foxes. ZUSAMMENFASSUNG: Fortpflanzung bei Silberfuchsf?hen, Vulpes vulpes, in Relation zu ihrem eigenen und dem Wettbewerbsrang ihrer Nachbarn Die Reproduktionsleistung von 34 ein und fünf zwei Jahre alten Silberfuchsf?hen wurde in Bezug zu ihrem eigenen und dem sozialen Rang ihrer Nachbarf?hen gesetzt. Sie wurden hierfür bei fünf bis sieben Monaten Alter geprüft und in drei Gruppen geteilt: hoch (HCC), mittel (MCC) und niedrig (LCC) in Abh?ngigkeit des sozialen Ranges. Nach Selektion wurden sie in K?figen mit Nachbarn wie folgt kombiniert: HCC mit LCC oder HCC-Nachbarn, MCC mit MCC und LCC mit LCC, MCC und HCC-Nachbarn. Die F?hen hatten dieselben Nachbarn von Oktober bis Ende der Reproduktionssaison im Juni oder Juli des folgenden Jahres und waren von ihren Nachbarn durch doppelte Drahtwand getrennt. Die Zahl der geborenen Jungen unterschied sich zwischen den Gruppen nur geringfügig, doch haben HCC-F?hen mit LCC-Nachbarn mehr Junge aufgezogen als irgendwelche andere, auch mehr als HCC mit anderen HCC-Nachbarn. Keine der LCC-F?hen konnte bei h?her rangierten Nachbarn unverletzte Junge aufziehen, wohl aber bei LCC-Nachbarn. Die Untersuchung zeigt, da? soziale Faktoren das maternale Verhalten von Silberfüchsen signifikant beeinflussen.     

Validation of a direct radioimmunoassay of melatonin in the blue fox

A direct radioimmunoassay procedure for the determination of melatonin in the blood of blue fox has been validated and applied.The assay required 50 μl of sample and standard, 100 ul of antiserum and 100 μl of (³H)melatonin. After overnight incubation at 4°C the antibody bound melatonin was separated from the free hormone with dextran-coated charcoal. Following centrifugation the antibody bound (³H)melatonin was determined in a beta scintillation counter.The antiserum bound 30–35 % of the (³H)melatonin at a final dilution of 1:36000. The non specific binding represented less than 5% of the total radioactivity in all assays. The lowest detectable amount of melatonin was 2.6 fmol/tube, corresponding to 52.5 pmol/1. The inter-assay coefficient of variation at 178 and 510 pmol/1 was 15.6 and 8.8%, respectively. The precision profile, calculated from a 10-replicate standard curve, showed that the coefficient of variation decreased from 43% at 84 pmol/1 to 15% at 336 pmol/1, and remainded at or below 10% for concentrations exceeding 670 pmol/1.Plasma was collected from 2 male blue foxes at about hourly intervals during a 24 h period in September and assayed for melatonin. Maximum (421 pmol/1) and minimum (97 pmol/1) concentrations of the hormone were inversely related to light intensity.     

A case of granulosa cell tumour with cystic endometrial hyperplasia in a blue fox vixen (Alopex lagopus)

The clinical features of a case of granulosa cell tumour in the blue fox (Alopex lagopus) are described. The associated hormonal changes are discussed in relation to present knowledge of the regulation of the oestrous and furring cycles in this species.     

Brain and spinal cord lesions in encephalitozoonosis in the blue fox

The central nervous system lesions in encephalitozoonosis were studied in 11 naturally infected blue foxes. Immunohistochemical staining was employed in the demonstration of the parasites and identification of host cells. Consistent findings in acute to subacute stages included granulomatous meningoencephalomyelitis and vasculitis, with arterial lesions similar to polyarteritis nodosa. Chronic stages were dominated by arteriosclerosis, perivascular mononuclear infiltrations and gliosis, with less prominent granulomatous reaction. Parasites were almost constantly observed in association with active lesions both in vessels and nervous tissue. Parasitophorous vacuoles (PV) occurred in endothelial cells and in the medial layer of arteries. Neurons, including even their processes, were widely parasitized, a fact that may account for the brain being an important target organ. PV also occurred in ependymal cells of the choroid plexus and occasionally in macrophages. A great number of parasites was demonstrated in phagolysosomes of macrophages, a fact that probably reflects a relative resistance to digestion, and may consequently contribute to the development of the prominent granulomatous reaction. It was concluded that the brain lesions, except in chronic stages of mild infections, seem to be pathognomonic for encephalitozoonosis in the blue fox.     

Effectiveness of Cabergoline for Termination of Pregnancy in Silver Fox (Vulpes vulpes fulva)

Red foxes ( Vulpes vulpes ) are a major pest species in Europe and Australia. Traditional methods of control such as hunting or poisoning are no longer sufficient or feasible. As with domestic dogs and cats, prolactin (PRL) in the vixen is an essential luteotropin during the second half of gestation. Hence, PRL inhibitors such as cabergoline have been used to induce abortions. Eighteen mated silver fox vixens (three groups of six foxes each) were treated orally with a placebo of paraffin oil (I), or with 15  μ g/kg cabergoline in feed once (II) or twice (III), on day 30 (I and II) or days 30 and 32 (III) post-coitum. Blood samples were taken prior to and after treatments and concentrations of PRL and progesterone (P₄) were determined. Normal parturitions were observed in five of six, five of six and two of six vixens in groups I, II and III, respectively. In group III plasma concentrations of PRL and P₄ decreased significantly but only temporarily. This drop in hormone concentrations was more pronounced in the vixens that did not carry to term. In conclusion, doses in excess of 15  μ g/kg of cabergoline are likely to prevent the development of fetuses to term in pregnant vixens.