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The objective of this study was to determine whether different dietary vitamin E (VE) and selenium (Se) levels affect the nutrient digestibility, production performance, and antioxidant abilities of growing furring blue foxes. A 4 × 2 factorial arrangement that included 4 levels of VE (0, 100, 200, or 400 mg/kg diet from α-tocopherol acetate) and 2 levels of Se (0 or 0.2 mg/kg diet from glycine selenium) was performed from mid-September to pelting. A metabolism study was conducted for four days starting at the 30th day of the trial. Serum samples were collected at the last day of the study. The results showed that supplementation of growing furring blue fox diets with VE and Se significantly affected the average daily gain (ADG), average daily feed intake, and feed conversion ratio (F:G) (P < 0.05). Dietary Se supplementation enhanced protein and fat digestibility of male blue foxes. There were significant effects of different VE and Se levels in diets on serum antioxidant parameters and metabolic parameters of blue foxes (P < 0.05). In conclusion, this research indicated that dietary supplementation with VE improved ADG and F:G of blue foxes. Addition of VE and Se to blue fox diets increased the antioxidant capacity of blue foxes. The diet with high VE and Se supplementation reduced glucose and triglycerides concentrations in serum. The present study found that growing furring blue foxes had increased growth performance and antioxidant abilities when fed diets with 200 mg VE/kg and nearly 0.1 mg Se/kg.

The maintenance requirements of net energy and net protein were assumed to represent the most accurate and important values totally for the animal's utilization. The objective of this experiment was to determine the net energy and net protein requirements for maintenance of growing arctic foxes. The experiments was evaluated using regression models estimated from data collected by means of indirect calorimetry, nitrogen balance trials, and digestion and metabolism experiments. Thirty-six growing arctic foxes (3 487 ± 261.7 g) at the age of 85 days were randomly assigned to four groups with 9 animals in each group. Arctic foxes were fed a complete formula diet at four intake levels (100%, or 80%, 60%, and 40% of feed requirements) from 24 July 2017 to 23 September 2017. Arctic foxes in each treatment were kept individually in respiration chambers after 1-d adaptation at day 2 for a 3-d balance trial and then at day 5 followed by a 3-d fasting period. The metabolizable energy intake (MEI), heat production in the fed state (HP), and retained energy (RE) of arctic foxes significantly decreased (P < 0.01) as the feed intake level decreased. Fasting heat production (FHP) of arctic foxes was not influenced by feed intake level (P > 0.05). The metabolizable energy maintenance requirement (MEm) and net energy maintenance requirement (NEm) estimated from the linear relationship between RE and MEI were 230 and 217 kJ/kg of body weight BW0.75/d, respectively. The MEm and NEm estimated by logarithmic regression of HP on MEI were 225 and 209 kJ/kg BW0.75/d, respectively. The net N maintenance requirement (NNm) and net protein maintenance requirement (NPm) estimated from the linear relationship between retained nitrogen (RN) and daily nitrogen intake (NI) were 179.6 mg/kg BW0.75/d and 1.123 g/kg BW0.75/d, respectively. It is concluded that NEm and NPm values obtained fill the net energy and protein requirements shortage, and provide the basic data for establishing the standard of nutrition demand of breeding arctic foxes in China., (© The Author(s) 2019. Published by Oxford University Press on behalf of the American Society of Animal Science. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

To improve the accuracy and genetic progress of blue fox breeding, the relationships between genetic polymorphisms and growth and reproductive traits of the blue fox were investigated. MC4R, MC3R, INHA and INHBA were selected as candidate genes for molecular evolution and statistical analyses. Single-factor variance analyses showed that the MC4R (g.267C > T, g.423C > T, and g.731C > A) and MC3R (g.677C > T) genotypes had significant impacts on body weight, chest circumference, abdominal perimeter and body mass index (BMI) (P < 0.05) in blue fox. The MC4R and MC3R combined genotypes had significant effects on the body weight and abdominal circumference. The different genotypes of INHA g.75G > A had significant effects on female fecundity, whereas the different genotypes of INHBA g.404G > T and g.467G > T and the INHA and INHBA combined genotypes had significant effects on male fecundity. The proteins encoded by the open reading frames (ORFs) of different polymorphic loci were predicted and analysed. The aims of this study were to identify genetic markers related to growth and reproduction in the blue fox and to provide an efficient, economical and accurate theoretical approach for auxiliary fox breeding., (Copyright © 2019 Elsevier B.V. All rights reserved.)

A 75-d experiment was conducted to evaluate the influence of dietary Cu concentrations on growth performance, serum lipid profiles, antioxidant defenses, and fur quality in growing-furring male blue foxes. Seventy-five male blue foxes (5.78 ± 0.09 kg BW) were selected and randomly allocated to 1 of the following 5 dietary treatments: 1) control (basal diet without supplemental Cu; 7.78 mg Cu/kg), 2) 12.22 mg/kg supplemental Cu (Cu20), 3) 32.22 mg/kg supplemental Cu, 4) 72.22 mg/kg supplemental Cu (Cu80), and 5) 152.22 mg/kg supplemental Cu (Cu160). A dry feed that consisted of animal meals, soybean meal, extruded corn, and soybean oil was used as the basal diet and Cu was supplemented as reagent grade CuSO∙5HO. The results showed that Cu supplementation increased the ADG ( < 0.05) and fat digestibility ( < 0.01) and tended to improve G:F ( = 0.09). The ADFI, however, was not affected by dietary Cu ( > 0.10). Additionally, Cu supplementation linearly increased the concentration of fecal Cu, liver Cu, serum total protein, and albumin ( < 0.01). Foxes in the Cu160 group had higher serum Cu concentration than those in the control and Cu20 groups ( < 0.05). The concentration of serum cholesterol decreased with dietary Cu supplementation ( < 0.05). Serum high-density lipoprotein, on the contrary, tended to increase with Cu supplementation ( = 0.09). Copper supplementation increased the activity of glutathione peroxidase ( < 0.05) and tended to increase the activity of serum ceruloplasmin ( = 0.07). For fur quality, skin length in the Cu80 group was greater than that in the control and Cu20 groups. In addition, hair color tended to deepen with the increasing of dietary Cu concentrations ( = 0.08). In conclusion, this study demonstrates that Cu supplementation can promote growth and increase fat digestibility and fur length. Additionally, dietary Cu supplementation can enhance antioxidant capacity and reduce serum cholesterol in growing-furring blue foxes.

Polymorphism of 30 canine-derived microsatellites was studied in a group of 200 red foxes kept on 2 Polish farms. 22 out of 30 microsatellites were selected to study association between marker genotypes and body weight (BW), body length (BL), body circumference (BC), tail length (TL), ear height (EH), length of the right front limb (FRLL), length of the right rear limb (RRLL), length of the right front foot (FRFL) and length of the right rear foot (RRFL). A total of 112 alleles and 243 genotypes were found at 22 autosomal microsatellite loci. Three monomorphic loci deemed as uninformative were excluded from the study. The association between marker genotypes and the studied traits was analysed using general linear model (GLM) procedure and least squares means (LSM). Linkage disequilibrium (LD) was estimated to assess non-random association between microsatellite loci. Out of 19 microsatellites studied four markers showed no association with the studied traits, three markers had a significant effect on one trait, and another three markers had significant effect on two traits. Among ten microsatellites with significant effect on four economically important traits (BW, BL, BC, TL) four were associated with two characters: marker FH2613 with BW and BC, marker FH2097withBL and BC, marker ZUBECA6 with BW and BC, whereas marker REN75M10 was associated with BL and TL. The strongest LD (r(2) ranged from 0.15 to 0.33) was estimated between nine loci with significant effect on economically important traits (BW, BL, BC, TL).

Within 20 years, experimental selection of quantified "not too aggressive, not too fearful" behavior to human approach was shown in silver foxes (Vulpes vulpes) to produce a neotenic package of traits in adults: ability to seek, induce, and sustain contact (called friendly or rapport behavior); relatively short limbs and foreshortened skull/face; and light pigmentation areas. Earlier sexual maturation, prolonged receptivity, and larger litters were also noted. The increased estradiol supporting these changes was apparently also responsible for faster skeletal maturation, including earlier fusion of the basicranium causing tooth crowding, but also paedomorphic craniofacial proportions that we find attractive in our own and other species. In this paper, these important findings of the farm fox experiment are juxtaposed with insights from social psychology, physical anthropology, and neuroscience about facial beauty and reaction to it. Since many unrelated species show some or all of the neotenic package or domestication profile when they have achieved rapport past the juvenile stage, craniofacial proportions considered attractive are discussed as genetically and hormonally linked to the evolution of rapport--social contact, trust, and cooperation--whether by natural, intuitive, intentional, or mixed paths of selection.

The objective of this study was to determine whether nutrient digestibility and production performance of growing-furring blue foxes (Alopex lagopus) are affected by different dietary fat levels. Sixty-four young animals were randomly assigned to four groups (A, B, C, D) provided with diets containing approximately 12%, 26%, 40%, 54% fat in the dry matter respectively. When dietary fat level was increased, the apparent digestibility of main nutrients except for crude carbohydrates, and gross energy were improved (p < 0.0001). The amount of nitrogen excreted was reduced and the biological value of protein was enhanced (p < 0.0001). Over the experimental phase, the efficiency of metabolizable energy (ME) used for gain in group B (26% fat content) was higher than that in other groups. When diets with 12-26% fat content were fed, there was an increasing tendency in skin size. But it had negative effects on skin size and fur quality when the amount of fat content was over 40%. In conclusion, the experiment showed that dietary fat could significantly improve some nutrient utilization and significantly reduce feed/gain ratio as a main energy source. The most preferable fur quality and efficiency of ME used for gain were obtained when diet contained 26% fat level in growing-furring period., (© 2011 Blackwell Verlag GmbH.)

Background: Over the past quarter century, the incidence of tick-borne encephalitis (TBE) has increased in most European nations. However, the number of humans stricken by the disease varies from year to year. A method for predicting major increases and decreases is needed., Methods: We assembled a 25-y database (1984-2008) of the number of human TBE victims and wildlife and climate data for the Stockholm region of Sweden, and used it to create easy-to-use mathematical models that predict increases and decreases in the number of humans stricken by TBE., Results: Our best model, which uses December precipitation and mink (Neovison vison, formerly Mustela vison) bagging figures, successfully predicted every major increase or decrease in TBE during the past quarter century, with a minimum of false alarms. However, this model was not efficient in predicting small increases and decreases., Conclusions: Predictions from our models can be used to determine when preventive and adaptive programmes should be implemented. For example, in years when the frequency of TBE in humans is predicted to be high, vector control could be intensified where infested ticks have a higher probability of encountering humans, such as at playgrounds, bathing lakes, barbecue areas and camping facilities. Because our models use only wildlife and climate data, they can be used even when the human population is vaccinated. Another advantage is that because our models employ data from previously-established databases, no additional funding for surveillance is required.

Directional asymmetry (DA) is a characteristic of most vertebrates, most strikingly exhibited by the placement of various organs (heart, lungs, liver, etc.) but also noted in small differences in the metrics of skeletal structures such as the pelvis of certain fish or sauropsids. We have analyzed DA in the skeleton of the fox (V. vulpes), using ∼1,000 radiographs of foxes from populations used in the genetic analysis of behavior and morphology. Careful measurements from this robust data base demonstrate that: 1) DA occurs in the limb bones, the ileum, and ischium and in the mandible; 2) regardless of the direction of the length asymmetry vector of a particular skeletal unit, the vectorial direction of length is always opposite to that of width; 3) with the exception of the humerus and radius, there is no correlation or inverse correlation between vectorial amplitudes or magnitudes of bone asymmetries. 4) Postnatal measurements on foxes demonstrate that the asymmetry increases after birth and continues to change (increasing or decreasing) during postnatal growth. 5) A behavior test for preferential use of a specific forelimb exhibited fluctuating asymmetry but not DA. None of the skeletal asymmetries were significantly correlated with a preferential use of a specific forelimb. We suggest that for the majority of fox skeletal parameters, growth on the right and left side of the fox are differentially biased resulting in fixed differences between the two sides in either the rate of growth or the length of the period during which growth occurs. Random effects around these fixed differences perturb the magnitude of the effects such that the magnitudes of length and width asymmetries are not inversely correlated at the level of individual animals., (© 2010 Wiley-Liss, Inc.)

The impact of dietary organochlorine (OC) exposure on thyroid gland pathology was studied in farmed male Arctic foxes (Vulpes lagopus). The exposed group (n=16) was fed a diet based on wild minke whale (Balaenoptera acutorostrata) blubber as a main fat source in order to mimic the exposure to OC cocktails in the Artic environment. This resulted in an exposure of approximately 17 microg Sigma OC/kg day and a Sigma OC residue adipose tissue and liver concentration of 1700 and 4470 ng/gl.w., respectively, after 16 months of exposure. Control foxes (n=13) were fed a diet with pork (Sus scrofa) fat as a main fat source containing significantly lower OC concentrations. The food composition fed to the control and exposed group was standardized for nutrient contents. Four OC-related histopathological changes were found: (1) flat-epithelial-cell true thyroid cysts (TC) characterized by neutral content; (2) remnants of simple squamous epithelial-cell embryonic ducts containing neutral debris (EDN); (3) remnants of stratified squamous epithelial-cell embryonic ducts containing acid mucins often accompanied with debris of leukocyte inflammatory nature (EDM) and (4) disseminated thyroid C-cell hyperplasia (HPC). Of these, the prevalence of TC, EDN and HPC was significantly highest in the exposed group (chi(2) test: all p<0.04). The study shows that the OC mixture in minke whale blubber may cause development of thyroid gland cysts, C-cell hyperplasia and increase the prevalence of cystic remnants of embryonic ducts. The mechanism causing these effects could include endocrine disruption of the hypothalamus-pituitary-thyroid (HPT) axis, a disturbance of the calcium homeostasis/metabolism or energy metabolism or immune suppression. Because concentrations of OCs are higher in wild Arctic foxes, it is likely that these animals could suffer from similar OC-induced thyroid gland pathological and functional changes.

The period following the withdrawal of parental care has been highlighted as a key developmental period for juveniles. One reason for this is that juveniles cannot forage as competently as adults, potentially placing them at greater risk from environmentally-induced changes in food availability. However, no study has examined this topic. Using a long-term dataset on red foxes (Vulpes vulpes), we examined (i) dietary changes that occurred in the one-month period following the attainment of nutritional independence, (ii) diet composition in relation to climatic variation, and (iii) the effect of climatic variation on subsequent full-grown mass. Diet at nutritional independence contained increased quantities of easy-to-catch food items (earthworms and insects) when compared with pre-independence. Interannual variation in the volume of rainfall at nutritional independence was positively correlated to the proportion of earthworms in cub diet. Pre-independence cub mass and rainfall immediately following nutritional independence explained a significant proportion of variance in full-grown mass, with environmental variation affecting full-grown mass of the entire cohorts. Thus, weather-mediated availability of easy-to-catch food items at a key developmental stage has lifelong implications for the development of juvenile foxes by affecting full-grown mass, which in turn appears to be an important component of individual reproductive potential.

The effects of persistent organic pollutants on renal and liver morphology in farmed arctic fox (Vulpes lagopus) were studied under experimental conditions. Control animals received a diet containing pork (Sus scrofa) fat with low amounts of persistent organic pollutants, while the diet of the exposed animals contained whale blubber, 'naturally' contaminated with persistent organic pollutants. Polychlorinated biphenyls (PCB) and organochlorine pesticide (OCP) concentrations in the whale blubber were 488 and 395 ng/g wet weight, respectively. Animals were sacrificed and sampled when they were at their fattest (winter) as well as their lowest body weight (summer). The results show that PCB and OCP exposure causes renal (and probably also liver) lesions in arctic foxes. The prevalence of glomerular, tubular and interstitial lesions was significantly highest in the exposed group (chi-square: all p<0.05). The frequency of liver lesions (steatosis, intravascular granulocyte accumulations, interstitial cell infiltrations, lipid granulomas, portal fibrosis and bile duct hyperplasia) were also highest in the exposed group, although not significantly (chi-square: all p>0.05). The prevalence of lesions was not significantly different between lean (winter) and fat (summer) foxes for any of the lesions (chi-square: all p>0.05). We suggest that wild arctic foxes exposed to an environmental cocktail of persistent organic pollutants, such as PCBs and OCPs, in their natural diet are at risk for developing chronic kidney and liver damage. Whether such lesions may have an impact on age and health of the animals remains uncertain.

The completion of the life cycle of Echinococcus multilocularis needs a spatial overlap between intermediate host species (voles) and definitive host (fox) faeces. Factors influencing the importance of this overlap were investigated in north eastern France. Kilometric transects were walked to collect fox faeces and to estimate vole relative densities through surface indices. Habitat and climatic conditions were the strongest predictors of the number of faeces collected, while vole densities had no predictive power. Densities of both Microtus sp. and fox faeces were higher in medium-height vegetation edge. The consequences of such results to understand local transmission processes and human exposure are discussed.

Concentrations of copper, zinc, iron, cadmium, lead, and nickel in the semen of foxes (Vulpes vulpes, n = 10), microscopic analysis of occurrence of pathological spermatozoa, and correlations of these elements with pathological forms were studied. Samples were analyzed by using an atomic absorption spectrophotometer. For analysis of pathological spermatozoa semen samples fixed with Hancock's solution and stained with Giemsa were prepared. For each fox at least 1000 spermatozoa were evaluated. The concentrations of copper, zinc, and iron in semen of foxes were found to be 2.16+/-0.53 mg/kg, 13.09+/-5.22 mg/kg, and 33.16+/-24.36 mg/kg, respectively, on wet weight basis. Concentration of cadmium was low (0.07+/-0.05 mg/kg). The levels of lead and nickel in the semen of foxes were 0.08+/-0.06 mg/kg and 0.35+/-0.24 mg/kg, respectively. The total percentage of pathological spermatozoa was 7.76+/-1.33% with predominancy of knob twisted flagellum, separated flagellum, and broken flagellum. In relation to trace elements the analysis showed significant (p < 0.05) correlation between copper and lead (r = -0.85), copper and other forms of pathological spermatozoa (r = -0.72), zinc and broken flagellum (r = -0.69), iron and retention of cytoplasmic drop (r = 0.87), cadmium and separated flagellum (r = -0.68), and between cadmium retention of cytoplasmic drop (r = 0.87).

Background: Extensive work has been done to identify and explain multi-year cycles in animal populations. Several attempts have been made to relate these to climatic cycles. We use advanced time series analysis methods to attribute cyclicities in several North-American mammal species to abiotic vs. biotic factors., Results: We study eleven century-long time series of fur-counts and three climatic records--the North Atlantic Oscillation (NAO), the El-Niño-Southern Oscillation (ENSO), and Northern Hemisphere (NH) temperatures--that extend over the same time interval. Several complementary methods of spectral analysis are applied to these 14 times series, singly or jointly. These spectral analyses were applied to the leading principal components (PCs) of the data sets. The use of both PC analysis and spectral analysis helps distinguish external from intrinsic factors that influence the dynamics of the mammal populations., Conclusions: Our results show that all three climatic indices influence the animal-population dynamics: they explain a substantial part of the variance in the fur-counts and share characteristic periods with the fur-count data set. In addition to the climate-related periods, the fur-count time series also contain a significant 3-year period that is, in all likelihood, caused by biological interactions.

Serum samples collected from red foxes in the city of Berlin between 1996 and 1999 were analysed for the presence of antibodies against Opisthorchis felineus and Metorchis bilis using an indirect ELISA. Out of 1,000 specimens, 30.6% and 46.5% reacted positively with specific O. felineus and M. bilis antigens, respectively. Seroprevalence in adult foxes was always higher than in juveniles. While no significant differences were observed in adult foxes throughout the period, in juvenile specimens seroprevalence declined from 1996 to 1997, then stayed at a comparable level in 1998 and increased in 1999. A varying availability of fresh cyprinid fish in different years seems to be the reason for changes in seroprevalence. By grouping the samples from juvenile foxes by season, antibodies against both Metorchis and Opisthorchis antigens started to appear between April and June, increased between July and September()and reached a level comparable to adult foxes in the October to December quarter. The lowest seroprevalence was found in Pankow, which is the district with the lowest share of the surface water.

The red fox (Vulpes vulpes) is one of the best-documented examples of a species that has successfully occupied cities and their suburbs during the last century. The city of Zurich (Switzerland) was colonized by red foxes 15 years ago and the number of recorded individuals has increased steadily since then. Here, we assessed the hypothesis that the fox population within the city of Zurich is isolated from adjacent rural fox populations against the alternative hypothesis that urban habitat acts as a constant sink for rural dispersers. We examined 11 microsatellite loci in 128 foxes from two urban areas, separated by the main river crossing the city, and three adjacent rural areas from the region of Zurich. Mean observed heterozygosity across individuals and the number of detected alleles were lower for foxes collected within the city as compared with their rural conspecifics. Genetic differentiation was significantly lower between rural than between rural and urban populations, and highest value of pairwise FST was recorded between the two urban areas. Our results indicate that the two urban areas were independently founded by a small number of individuals from adjacent rural areas resulting in genetic drift and genetic differentiation between rural and urban fox populations. Population admixture and immigration analysis revealed that urban-rural gene flow was higher than expected from FST statistics. In the five to seven generations since colonization, fox density has dramatically increased. Currently observed levels of migration between urban and rural populations will probably erode genetic differentiation over time.

Different doses of probiotics EM were added to the diets of blue fox in its growth phase to study the effects of EM additives on its growth, digestion metabolism and immune function. The results showed that with EM additives applied, the ingestion and average daily gains were increased remarkably (P < 0.05). The apparent digest rate of crude fibre, crude protein, mineral elements Ca, P and NPU could be increased (P < 0.05) and correlated with its dose, and the digest rates of the later four targets in group III were increased by 8.21%, 16.27%, 9.82%, and 12.13%, respectively. EM additives could not increase the digest rate of ether extral and N-free extract. Disease of diarrhoea and blood in stool could be prevented and cured, and immune function and the survival rate of fox in growth phase could be increased remarkably. EM, which a kind of efficient, safe and environmental protection additives, can be extended and applied in farming of fur animals.

Isozymes of lactate dehydrogenase extracted from heart, kidney, and liver of mink (Mustela vison Briss.) and Arctic fox (Alopex lagopus L.) during postnatal development were separated by agarose gel electrophoresis. Tissue-specific isozyme pattern of lactate dehydrogenase can be revealed at the age of one month, while the definitive pattern is formed at the age of four months. The isozyme patterns of lactate dehydrogenase in the studied tissues of mink and Arctic fox share the properties specific for animal species of various ecogenesis.

Milk intake of fox cubs (2-16 days of age; body weight, 96-649 g) in ten blue fox litters and ten silver fox litters were measured by the water isotope dilution (WID) technique following a single intraperitoneal injection of tritiated water (3HHO). Litter size varied from four to 14 in blue foxes and from three to eight in silver foxes. Silver fox cubs had higher birth weights than blue foxes. Inter-species body weights and growth rates were apparently dependent on litter size and the dam's constitution. In both species growth rate increased with age and body weight (7-35 g per day). In the cubs, the biological half-life of body water turnover (BWT) rose from 1.5 days at 2-3 days of age to 2.5 days at 13-16 days of age, although a considerable scatter was seen. The mean daily milk intake of the cubs varied with body weight, from 31 to 193 g per day, whereas daily milk intake per unit of body mass remained stable at 30-35 g per 100 g body weight. The ratio of milk intake to body weight gain varied considerably among cubs, averaging 4.5 g/g during the 3-week experimental period. In suckling fox cubs, the calculated daily intake of metabolically energy (ME) corresponded fairly with the estimated energy requirements for growth and maintenance of the young. Finally, the applicability and the accuracy of the WID technique was evaluated in ten 3-week-old fox cubs, by tube-feeding with a milk replacer for 48 h, which documented that the daily rates of milk intake and water turnover can be accurately measured in suckling fox cubs by the WID technique following a single injection of 3HHO.

The meiotic competence and meiosis resumption of Blue fox (Alopex lagopus) oocytes from anoestrous animals were followed. Oocyte-cumulus complexes (OCC) were cultured in modified TC 199 medium with or without FSH, recombinant bovine somatotrophin (bST) and okadaic acid (OA). The results showed that oocytes less than 100 microns in diameter did not achieve germinal vesicle breakdown (GFBD) by 72 h of culture, which indicates their meiotic incompetence. Oocytes larger than 100 microns in diameter underwent GVBD after 48 h of culture (27%) and reached metaphase II (MII) after 72 and 96 h (20% and 27%) in control medium. Both bST and OA accelerated resumption of meiosis (bST: 55% GVBD and 42% MII after 48 h; OA: 66% GVBD after 18 h). In contrast, FSH significantly reduced meiosis resumption (only 3% GVBD and MII after 72 h) and induced changes in the shape of cumulus granulosa (CG) cells and F-actin assembly typical for cumulus expansion. However, the innermost layers of CG cells (corona radiata) remained connected with the oocyte via gap junctions until the end of culture. Cumuli of oocytes cultured in control, bST-supplemented or OA-supplemented medium did not expand (changes in cell shape and F-actin redistribution did not occur). Moreover, especially in media with bST and OA an increased detachment and rapid disconnection of their gap junctions with the oocyte were observed. These results suggest that under in vitro conditions FSH stimulates expansion of the CG cells and the attached membrana granulosa cells but in contrast it secures heterologous gap junctions between cytoplasmic processes of the corona radiata cells and oolemma during 3 days of culture. Thus, in agreement with the in vivo situation in which Canidae oocytes are ovulated in the GV stage, the cumulus, mainly corona radiata cells, controls resumption of meiosis in Blue fox oocytes under in vitro conditions also.

Anthropometric, anatomical, hematological and biochemical reference values were estimated in clinically healthy male and female 9-month-old silver foxes. The coefficients of variation of anthropometric and anatomical measurements for 9-month-old silver foxes were as low as previously reported for adult foxes. However, in relation to body size, all measurements were smaller. Compared with adult silver foxes, higher values were observed in serum levels of triglyceride, phospholipid, beta-lipoprotein, blood urea nitrogen and total protein. Similarly, higher levels were obtained for serum enzymes, especially aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK). The high levels of these serum enzymes may be due to handling stress. Inorganic phosphorus and calcium concentrations in the young foxes were also high. The alkaline phosphatase (ALP) level, reflecting the level of bone growth, was higher than that of adults. Biochemical values of beta-lipoprotein glucose and calcium in male 9-month-old silver foxes were lower than those of females, whereas those of total cholesterol, total protein, fructosamine, iron, albumin and beta-globulin were higher.

Skull proportions and pattern of intracranial allometry in farm foxes of bred domesticated populations are compared. Changes in skull measurements and bivariate allometry are observed in domesticated males, which in this respect become closer to domesticated females. The changes in the allometry pattern in the domesticated population points to deep modifications of regulatory ontogenetic processes which underlie the allometric growth. However, morphological changes in domesticated foxes cannot be only accounted for by allometry.

In domesticated at the age from 30-th to 60-th days foxes an intensification of orienting-investigating behaviour takes place in unknown situation. Cortisol level is not changed. In foxes, selected for aggressive behaviour towards man, at 30 days age the orienting-investigating behaviour is also observed, and hormone concentration does not differ from that in domesticated fox-cubs. In aggressive cubs of 45 days a defensive behaviour develops and cortisol content in blood significantly increases. Participation is discussed of adrenal cortex hormones in manifestation of defensive reactions and mechanisms of restriction of sensitive period of socialization.

Studies have been made on the structure of the adrenal cortex in relatively wild and domesticated male and female silver foxes at the age of 1-7 days, 1, 2 and 8 months. It was demonstrated that during domestication, deep morphological changes in the adrenal cortex take place which indicate the decrease of functional activity in the fascicular zone and the increase of the activity in the reticular zone. Differences found in the first days of postnatal life become more evident in further ontogenesis.

The spectrum of lactate dehydrogenase (LDH) isozymes in erythrocytes of silver foxes was investigated by means of electrophoretic and immunochemical methods. By means of electrophoresis it is shown that differences in LDH isozyme spectrum between the animals homozygous for the gene Ldr-1a and those homozygous for the gene Ldr-1b are most conspisions at the age of 90-100 days of postnatal development. By means of the immunochemical method three groups of animals are distinguished differing in the LDH content in erythrocytes: the animals with a high LDH content (81.0 mcg/ml) and with a low LDH content (54.14 mcg/ml), which are homozygous for the gene Ldr-1b and Ldr-1a respectively, and the animals with intermediate LDH content (64.58 mcg/ml), which are heterozygous. The data obtained suggest that the effect of the gene Ldr-1a is associated with the decrease of the quantity of A subunits of LDH. It is assumed that the mechanism of the gene Ldr-1a action is realized either by means of the decrease of the synthesis of the A LDH subunits, or by means of the increase of the rate of their degradation.

A clearly different Sertoli cell morphology was found in the immature blue fox and in the adults in and out of season. Immature cells had small, basally, located nuclei rich in peripheral heterochromatin, and few cytoplasmic organelles. Sertoli cells from adults in season had basally located, large, convoluted nuclei with homogenous nucleoplasma and prominent nucleoli. The basal and intermediate parts of the cytoplasm contained an extensively developed ER, numerous mitochondria, free ribosomes, lipid droplets and residual bodies, while the apical cytoplasm showed few distinct structures. In Sertoli cells from adults out of season the nuclei were dislocated towards the lumen, and apart from numerous dilated cisternae of ER, there were generally fewer organelles, but more glycogen particles. A marked rise in FSH binding was found towards the breeding season.

Published techniques for fitting data to nonlinear growth curves are briefly reviewed; most techniques require knowledge of the shape of the curve. A flexible growth curve developed by Richards (1959) is discussed as an alternative when the shape is unknown. The shape of this curve is governed by a specific parameter, which can be estimated from the data. We describe in detail the fitting of a diverse set of longitudinal and cross-sectional data to Richards' growth curve for the purpose of determining the age of red fox (Vulpes vulpes) pups on the basis of right hind foot length. The fitted curve is found suitable for pups less than approximately 80 days old. The curve is extrapolated to pre-natal growth and shown to be appropriate only for about 10 days prior to birth.