Customizing semen preservation protocols for individual dogs and individual species: sperm preservation beyond the state of the art

Sperm quality can be variable in morphometric and physiological attributes between males of different species, between males within species subtypes reared under different environmental conditions, between ejaculates of the same male or even between sperm populations within an ejaculate. Clinical semen evaluation is based on evaluation of whole ejaculates, which is not a chemically or physiologically well-defined entity, rather a collection of heterogeneous subpopulations giving different measurements and possessing different fertilizing potential. Identification of subpopulations with different motility patterns is important as well as characterizing the subtle structural changes underlying the motility differences observed. The ability to identify populations of sperm responding rapidly or failing to progress through the capacitation process may have clinical applications. Studies of lipid-phase fluidity of sperm membranes, mathematical modelling of membrane ion transport, role of modifying components and detergent-resistant microdomains are of particular interest. When customizing extenders to ejaculates from cryosensitive males or species, a thorough knowledge of species sperm membrane physiology and an assessment of the individual ejaculate's sperm populations are necessary. Structural differences have been found in sperm membranes between fox species with different cryosurvival potential of their spermatozoa. Supplementation of lipids and detergents in cryoextenders may influence membrane fluidity of the surviving spermatozoa in a species-dependent manner and influence capacitation. Immobilization of sperm prior to cryopreservation with subsequent slow release of sperm in the female genital tract may be a way to prolong the fertile life of sperm. In canids with a long oocyte maturation time, delayed capacitation may be beneficial.

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.

Sperm DNA damage is related to field fertility of semen from young Norwegian Red bulls

Flow cytometry was utilised for the first time to independently measure five sperm parameters of individual spermatozoa of bull ejaculates to differentiate between outcome successes after artificial insemination (AI). These parameters included plasma membrane and acrosome integrity, mitochondrial functionality and DNA damage measured by sperm chromatin structure assay (SCSA) and terminal deoxynucleotide transferase-mediated dUTP nick end labelling (TUNEL) assays. For each parameter, results of 142 ejaculates (30 bulls) were ranked into three groups according to their flow cytometric measures: (1) ejaculates with the 25% lowest measures; (2) the 50% middle measures; and (3) the 25% highest measures. In total, 20 272 first-service inseminations (18 × 106 spermatozoa per AI dose) were performed, where fertility was defined as non-return within 60 days after first insemination. While plasma membrane and acrosome integrity, and mitochondrial functionality were not significantly related to fertility, data from SCSA and TUNEL assays were significantly associated with fertility. Ejaculates in SCSA group 1 had higher odds of AI success (1.07, 95% CI = 1.02–1.12), whereas those in group 3 had lower odds of AI success (0.94, 95% CI = 0.89–0.99), compared with the average odds of all three groups. Ejaculates in group 2 did not have significantly higher odds of AI success compared with the average odds. For TUNEL-positive spermatozoa, the odds of AI success was higher in group 1 compared with the average odds (1.10, 95% CI = 1.02–1.13), whereas odds of AI success in groups 2 and 3 were not significant compared with the average odds. In conclusion, despite the high number of spermatozoa per AI dose from high-quality bulls, both SCSA and TUNEL assays were valuable measures in this study for evaluating sperm quality in relation to fertility after AI.

Comparative aspects of sperm membrane fatty acid composition in silver (Vulpes vulpes) and blue (Alopex lagopus) foxes, and their relationship to cell cryopreservation

Cryogenic protocols have been developed for the storage of farmed silver fox (Vulpes vulpes) spermatozoa. However, these same protocols and modifications of these protocols have failed to satisfactorily preserve spermatozoa collected from farmed blue foxes (Alopex lagopus). Because cryogenic success has been linked to membrane composition, the plasma membrane lipid composition of farmed blue fox and silver fox spermatozoa was studied. Silver fox spermatozoal membranes have significantly higher levels of docosapentaenoic acid (DPA; 22:5, n-6) compared to blue fox spermatozoa, and blue fox spermatozoal membranes have significantly higher levels of stearic acid (18:0). Silver fox spermatozoal membranes not only have a higher ratio of unsaturated/saturated membrane fatty acids, but also higher levels of membrane desmosterol and cholesterol.

Mapping of the bovine genes of the de novo AMP synthesis pathway

Summary The purine nucleotides adenosine monophosphate (AMP) and guanosine monophosphate (GMP) are critical for energy metabolism, cell signalling and cell reproduction. Despite their essential function, little is known about the regulation and in vivo expression pattern of the genes involved in the de novo purine synthesis pathway. The complete coding region of the bovine phosphoribosylaminoimidazole carboxylase gene (PAICS), which catalyses steps 6 and 7 of the de novo purine biosynthesis pathway, as well as bovine genomic sequences of the six other genes in the pathway producing inosine monophosphate (IMP) and AMP [phosphoribosyl pyrophosphate amidotransferase (PPAT), phosphoribosylglycinamide formyltransferase (GART), phosphoribosylformylglycinamidine synthase (PFAS), adenylosuccinate lyase (ADSL), 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase (ATIC) and adenylosuccinate synthase (ADSS)], were identified. The genes were mapped to segments of six different bovine chromosomes using a radiation hybrid (RH) cell panel. The gene PPAT, coding for the presumed rate-limiting enzyme of the purine de novo pathway was closely linked to PAICS on BTA6. These, and the other bovine locations i.e. GART at BTA1, PFAS at BTA19, ADSL at BTA5, ATIC at BTA2 and ADSS at BTA16, are in agreement with published comparative maps of cattle and man. PAICS and PPAT genes are known to be closely linked in human, rat and chicken. Previously, an expressed sequence fragment of PAICS (Bos taurus corpus luteum, BTCL9) was mapped to BTA13. By isolation and characterization of a BAC clone, we have now identified a PAICS processed pseudogene sequence (psiPAICS) on BTA13. Processed pseudogene sequences of PAICS and other genes of the purine biosynthesis pathway were identified in several mammalian species, indicating that the genes of this pathway have been susceptible to retrotransposition. The seven bovine genes are expressed at a higher level in testicular and ovary tissues compared with skeletal muscle.

Effects of in vitro storage time and semen-extender on membrane quality of boar sperm assessed by flow cytometry

The Norwegian AI company Norsvin has used the short-term semen-extender BTS to extend and store boar semen since the late 1980s. Fertility results have been consistent when extended semen has been used for AI within 3 days after collection, however, from a production and economic point of view it is preferable that semen stored for up to 5 days can be used. The aim of this study was to compare membrane quality of sperm stored in BTS for 3 days with sperm stored in the long-term semen-extenders Androstar, Mulberry III and X-cell for 5 days. Using a split-sample design, plasma membrane- and acrosome-integrity were assessed flow cytometrically by use of Yo-Pro-1 and PNA-FITC, and fluidity and phospholipid asymmetry of the membrane were assessed by use of MC540 and Annexin V-FITC. Due to observed sperm fragmentation in Androstar after Day 1, the data for Androstar were excluded from the analyses. After 5 days of storage, the membrane quality of X-cell-stored sperm was not statistically different from that of sperm stored in BTS for 3 days, while membrane quality of sperm stored in Mulberry III was statistically better on Day 5 compared to BTS on Day 3. In conclusion, Mulberry III and X-cell preserve sperm quality, as well as that of BTS on Day 3, for up to 5 days after collection.

Components of litter size in mice after 110 generations of selection

The aim of the present study was to evaluate how ovulation rate and survival rate through pregnancy had been affected by more than 110 generations of upwards selection on litter size in mice. The mean number of pups born alive was 22 in the high line (selected line) and 11 in the control line (an increase in 2.6 standard deviations). Selection on litter size increased ovulation rate by 4.6 standard deviations, and it is suggested that selection also increased embryonic mortality in late pregnancy. Embryo survival from ovulation until birth was 66% in the selected line and 69% in the control line, and the observed loss in litter size from day 16 of pregnancy until birth was possibly higher in the high line compared with the control line. Selection for higher litter size has significantly increased body weight in both males and females, as the mean weight at mating for the females was 46 g in the high line and 33 g in the control line respectively.

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.

Maturation and fertilization of blue fox (Alopex lagopus) oocytes in vitro

The aim of the present study was to assess the progression of meiotic maturation and fertilization of in vitro matured blue fox (Alopex lagopus) oocytes at different time intervals after in vitro maturation and insemination by the use of confocal laser scanning microscopy. A total of 242 immature oocytes from ovarian follicles 1-2 mm in diameter from seven ovulating blue fox vixens at oestrus were cultured for 48 h in TCM-199 before in vitro insemination with 5.0 x 10(5) frozen-thawed fox spermatozoa. Oocytes were transferred to 50 microliters microdroplets of modified Tyrode's medium without glucose at pH 7.7 under mineral oil, inseminated and cultured at 38 degrees C in a humidified atmosphere with 5% CO2 for 2 (n = 10), 4 (n = 22), 8 (n = 41), 20 (n = 52), 24 (n = 10), 30 (n = 48) and 48 h (n = 59). The oocytes and zygotes were stained with propidium iodide and were analysed by confocal laser scanning microscopy or epifluorescence microscopy. Only 125 of 242 oocytes (52%) could be evaluated: of these germinal vesicle breakdown (GVBD) was observed in five of nine oocytes (56%) at 2 h, eight of 18 oocytes (44%) at 4 h, eight of 18 oocytes (44%) at 8 h, 27 of 42 oocytes (64%) at 20-24 h, 14 of 19 oocytes (74%) at 30 h, and 13 of 19 oocytes (68%) at 48 h after insemination. In total, 75 of 125 oocytes (60%) underwent GVBD. All stages from the germinal vesicle to the four-cell stage embryos were observed, but the rate of cleavage was low (9%). Immature oocytes collected from small subordinate ovarian follicles of oestrous vixens after ovulation of the dominant follicles were able to mature and be fertilized, as well as undergo the first two cleavage divisions 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.

Current state in biotechnology in canine and feline reproduction

Biotechnology has proceeded much further in cats than in canines, although the pregnancy rate after in vitro maturation (IVM), IVC and embryo transfer (ET) is still relatively low. The use of AI with frozen-thawed semen as a breeding tool to overcome breeding incompatibility or to preserve male genetic material has been limited in felines in contrast to the situation in domestic dogs and foxes. In many research scenarios and endangered felid species programs, the in vitro production of feline embryos with subsequent transfer has complemented the use of AI. Improvement of IVM, in vitro fertilization (IVF) and embryo culture coupled with ovarian tissue grafting, cryobanking of follicles, oocytes, semen, or embryos, with subsequent ET into surrogate females, may render this technology feasible for use in endangered wild felids. In canines, reliable systems for in vitro production of embryos, embryo cryopreservation and transfer are yet to be developed. The refinement of invasive fertilization techniques, such as intracytoplasmic sperm injection (ICSI), may eventually provide a tool for removal of recipient oocyte nuclei and transfer of selected embryonic or somatic cell donor nuclei into domestic cat ooplasm, thereby providing a tool for genetic modification, or for preservation of valuable genetic material.

Assisted reproductive technology in canid species

Assisted reproductive technologies in dogs began as early as the 18th century. The first scientifically recorded artificial insemination (AI) was performed in Italy by Spallanzani and lead to the birth of three pups. Progress in the area was slow, and subsequent development included AI equipment and methods for short-term preservation of fresh, and later, for frozen semen which led to the world's first litter produced from frozen semen in 1969. Improvement of freezing methods and AI equipment from 1970 onwards has rendered AI useful as a breeding technique for dogs. In parallel, AI in foxes was developed in Scandinavia in the early 1980's; this resulted in the economically valuable crossbreeding of silver and blue foxes for the production of bluefrost pelts. Unfortunately, due to the particular physiology of the canine female, progress in other artificial breeding techniques has lagged behind. Only in the last few years have these techniques been successfully applied in basic research to study oocyte maturation, in vitro fertilization, embryo cryopreservation and embryo transfer in canids.

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.

Reproduction in foxes: current research and future challenges

Basic information on fox reproduction, such as endocrinology, oocyte maturation, artificial insemination, fertilisation and embryo development, ovarian and testicular function, parturition, milk production and neonatology has been gained from studies of farmed animals. Fox farming is an industry with considerable economic importance in countries such as Norway and Finland, and the use of farmed animals as models to study wild canine species has proven valuable. This paper reviews some major research accomplishments and new knowledge and identifies future challenges in research regarding both the wild and domestic variants of the fox species.

Use of semen from a bull heterozygous for the translocation in an IVF program

In cattle, a translocation of the Robertsonian type between the largest and smallest chromosome leads to a reduction in fertility. This is substantiated by reduced nonreturn rates in daughter groups of bulls carrying the 1 29 translocation and in the heterozygous bulls themselves. This reduction in fertility is thought to be due to the early death of embryos with unbalanced karyotypes. The influence of semen from a bull known to be heterozygous for the 1 29 translocation on the outcome of a bovine IVF program was investigated. There was a significant difference (P<0.005) in terms of cleavage rate (59.8 vs 71.1%) and blastocyst rate (12.0 vs 20.0%) between the carrier and control bull, respectively. There was no difference in blastocyst quality as measured by cell number. The results observed in vitro are consistent with the field fertility records of the 2 bulls in terms of nonreturn rates (59.2 vs 70.6%, for the carrier and control bull, respectively).

Fertilization and early embryonic development in the blue fox (Alopex lagopus)

A total of 15 blue fox vixens aged 1-6 years were mated, 12 once on the first day of estrus and three a second time 48 hr after the first mating, and were killed 4 hr to 8 days following mating. Ova were collected from the oviducts, evaluated by stereomicroscopy, and studied by transmission (TEM; N = 49, 12 vixens) or scanning (SEM, N = 11, three vixens) electron microscopy. At 0-3 days after ovulation, the ova had not cleaved and were at different stages of meiotic maturation. In about one-half of these ova, representing all stages of meiotic maturation, a decondensing sperm head without nuclear envelope or a small pronucleus with partial nuclear envelope was observed. No clear relationship was found between maternal meiotic stage and the stage of paternal pronucleus formation. Sperm tails were never identified in the ooplasm. Cortical granules were released after sperm penetration at early stages of meiotic maturation. Thus the block against polyspermic penetration was activated during maturation of the oocyte. The first two-cell stage appeared 4 days after ovulation (3 days after mating), the first four-cell stage the following day (day 5), and the first eight-cell stage 6 days after ovulation (5 days after mating). In a single vixen mated late (7 days postovulation) two- to four-cell stages appeared the following day (day 8). This indicates that the time required for the first cleavage division decreases with increasing interval from ovulation to mating.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship between gonadotrophins, inhibin and sex steroid secretion during the periovulatory period and the luteal phase in the blue fox (Alopex lagopus)

The blue fox is a monestrous seasonal breeder with a pro-oestrus and oestrus lasting several days and a prolonged luteal phase in non-pregnant as well as pregnant vixens. Ovulation occurs 2 days after the preovulatory luteinizing hormone (LH) peak at the onset of oestrus; oocytes are ovulated as primary oocytes and maturation is completed 2-3 days later. Fertilization is possible during all stages of oocyte maturation until degeneration of oocytes 5 or 6 days after the LH peak. In this study, changes in plasma concentrations of follicle-stimulating hormone (FSH) and immunoreactive inhibin (iINH) and their relationships with LH, oestradiol, androstenedione, testosterone and progesterone secretion and with the periovulatory events, were determined throughout the reproductive cycle of 14 vixens. In late anoestrus and pro-oestrus, FSH and iINH were inversely related to each other (r = -0.84, P < 0.001); whereas FSH concentrations declined to reach low values within the 5 days preceding the LH peak, iINH secretion increased, as did that of oestradiol and androgens. Thereafter, iINH and steroid concentrations with the exception of progesterone reached maximal values at the time of the LH and FSH peaks and decreased within the following 2-3 days in the early luteal phase. Progesterone started to increase simultaneously with the LH peak, and when oocyte maturation was completed (around day 4), progesterone concentrations were increasing, while those of other hormones were low. A postovulatory release of FSH was detected between days 6 and 10; it preceded the rise in iINH, which began on day 8 when concentrations of progesterone were already high and those of oestradiol and LH were low. Progesterone and iINH were positively correlated over the period day 6 to day 49 (r = 0.62, P < 0.01). These results indicate that, in the blue fox, iINH is secreted by the preovulatory follicle and the corpus luteum; that during pro-oestrus, iINH may act in synergy with oestradiol to reduce the secretion of FSH and that after the LH peak the decrease of iINH and oestradiol concentrations may be responsible for the postovulatory release of FSH, which in turn causes an increase in iINH, possibly secreted by the corpus luteum and, as a result, FSH secretion is suppressed.

The optimum time for single artificial insemination of blue fox vixens () with frozen-thawed semen from silver foxes ()

During the breeding season of 1991 a total of 608 blue fox vixens aged 1 to 6 years (2.3 +/- 0.1 years, mean +/- SEM) from 2 farms were artificially inseminated intrauterine once with frozen-thawed silver fox semen (1 ml dose containing a total of 150 million spermatozoa). The vixens were allocated to 3 different groups according to the time of insemination. Vixens in Group 1 (n = 203), Group 2 (n = 198), and Group 3 (n = 207) were inseminated on the first, second or third day after the peak value of vaginal electrical resistance, respectively. An overall conception rate of 75% (456 of 608) and 6.0 +/- 0.1 (mean +/- SEM) cubs per litter was obtained. Conception rates and mean litter sizes were significantly different between groups of vixens with respect to day of insemination (P = 0.02, Chisquare, Kruskall-Wallis Test). Vixens inseminated on the second day (Group 2) had the highest conception rate (81%) and the largest mean litter size (7.0 +/- 0.2 cubs) of the three groups, while those inseminated on the third day (Group 3) had the lowest conception rate and mean litter size (70%, 5.4 +/- 0.3 cubs).

The effect of sperm number on fertility in blue fox vixens () artificially inseminated with frozen silver fox () 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.

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.

Structural aspects of oocyte maturation in the blue fox (Alopex lagopus)

Blood samples were taken weekly from seventeen mature blue fox vixens (average age five years), from late anoestrus until pro-oestrus, and then taken daily. The vixens were sacrificed at various stages of oestrus, and oocytes were collected from ovarian follicles by aspiration, and/or from oviducts by flushing. The structural features of oocyte maturation were related to the time of the luteinizing hormone (LH) peak. On days 1-2 after the LH peak the oocyte nucleus migrated from a central to a peripheral position in the ooplasm and assumed a flattened appearance. The cumulus investment expanded simultaneously and ovulation took place around day 2. On days 2-3 the oocyte nuclear envelope broke down, the nucleoli disappeared, the metaphase of the first meiotic division was reached, the Golgi complexes decreased in size, the perivitelline space enlarged, and all junctional contact between cumulus cell projections and oocyte was disrupted. On days 3-5 the first polar body was extruded, the metaphase of the second meiotic division was reached, and the cumulus cells degenerated. On day 5 the release of cortical granule content was occasionally seen, and from day 6 the oocytes showed signs of degeneration. In a few animals deviant oocyte maturation was noticed.

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.