Strong artificial selection in domestic mammals did not result in an increased recombination rate

Recombination rates vary in intensity and location at the species, individual, sex and chromosome levels. Despite the fundamental biological importance of this process, the selective forces that operate to shape recombination rate and patterns are unclear. Domestication offers a unique opportunity to study the interplay between recombination and selection. In domesticates, intense selection for particular traits is imposed on small populations over many generations, resulting in organisms that differ, sometimes dramatically, in morphology and physiology from their wild ancestor. Although earlier studies suggested increased recombination rate in domesticates, a formal comparison of recombination rates between domestic mammals and their wild congeners was missing. In order to determine broad-scale recombination rate, we used immunolabeling detection of MLH1 foci as crossover markers in spermatocytes in three pairs of closely related wild and domestic species (dog and wolf, goat and ibex, and sheep and mouflon). In the three pairs, and contrary to previous suggestions, our data show that contemporary recombination rate is higher in the wild species. Subsequently, we inferred recombination breakpoints in sequence data for 16 genomic regions in dogs and wolves, each containing a locus associated with a dog phenotype potentially under selection during domestication. No difference in the number and distribution of recombination breakpoints was found between dogs and wolves. We conclude that our data indicate that strong directional selection did not result in changes in recombination in domestic mammals, and that both upper and lower bounds for crossover rates may be tightly regulated.

Single-layer centrifugation separates spermatozoa from diploid cells in epididymal samples from gray wolves, Canis lupus (L.)

Sperm samples may be used for assisted reproductive technologies (e.g., farmed or endangered species) or as a source of haploid DNA or sperm-specific RNA. When ejaculated spermatozoa are not available or are very difficult to obtain, as is the case for most wild endangered species, the epididymides of dead animals (e.g., animals that have been found dead, shot by hunters or poachers, or that that require euthanasia in zoological collections) can be used as a source of sperm. Such epididymal sperm samples are usually contaminated with cellular debris, erythrocytes, leukocytes, and sometimes also bacteria. These contaminants may be sources of reactive oxygen species that damage spermatozoa during freezing or contribute undesired genetic material from diploid cells. We used single-layer centrifugation through a colloid formulation, Androcoll-C, to successfully separate wolf epididymal spermatozoa from contaminating cells and cellular debris in epididymal samples harvested from carcasses. Such a procedure may potentially be applied to epididymal sperm samples from other species.

An investigation on the presence of Chlamydiaceae in Swedish dogs

BACKGROUND

Bacteria belonging to the family Chlamydiaceae cause a broad spectrum of diseases in a wide range of hosts, including man, other mammals, and birds. Upper respiratory and genital diseases are common clinical problems caused by Chlamydiaceae. Very little is known about chlamydial infections in dogs. Few clinical reports on natural disease in dogs describe mainly conjunctival and upper respiratory signs, and the role of Chlamydiaceae in genital disease is unclear. The present study aimed at studying the prevalence of Chlamydiaceae in healthy dogs and in dogs with genital or upper respiratory disease, including conjunctivitis.

METHODS

A real-time polymerase chain reaction (PCR) for Chlamydiaceae was used to detect any chlamydial species within this family. Swab samples from the conjunctiva and the mucosal membranes of the oropharynx, rectum and genital tract were taken from 79 dogs: 27 clinically healthy dogs, 25 dogs with clinical signs from the genital tract and 28 dogs with conjunctivitis. There were 52 female and 27 male dogs. From 7 of the male dogs, additional semen samples were analysed.

RESULTS

No Chlamydiaceae were detected from any dog.

CONCLUSIONS

Although the number of dogs that was included is limited, the results suggest that cases of Chlamydiaceae in dogs probably are related to infection from other species, and that dogs in general do not harbour Chlamydiaceae. Bacteria belonging to the family Chlamydiaceae do not seem to be of major importance for genital or ocular disease in Swedish dogs.

A survey of dystocia in the Boxer breed

BACKGROUND

Dystocia occurs more commonly in some breeds of dogs than others. The Boxer breed is one of the highrisk breeds for whelping problems. The aim of this study was to document some reproductive parameters and the frequency of dystocia in Boxers.

METHODS

Two questionnaires were sent to the breeders of Boxers in Sweden during 1994 to 1997. Data from 253 whelpings and 1671 pups was received, which constitutes 56.5% of all Boxer litters registered with the Swedish Kennel Club during these years. Data was analysed using Chi-square test, and Fischer's exact test.

RESULTS

Dystocia occurred in 32% of the individual bitches, and in 27.7% of all the whelpings. Caesarian section was performed in 22.8% of all the whelpings and in 80.1% of the cases of dystocia. Medical treatment was tried in 20 cases but was successful only in 5 (25%). The dystocia was of maternal origin in 68.6% and of fetal origin in 28.6% of cases. The most common reasons for dystocia were primary uterine inertia (60%) and malpresentation of the fetus (26%). Dystocia increased with increasing age of the bitch from four years of age. Average litter size was 6.6 (+/- 2.2) pups born, and 5.0 (+/- 2.1) pups registered. Pup mortality was 24%. Stillbirths accounted for 6.1% of the pup deaths and 1% died in the neonatal period, while 15.6% of the pups were euthanised, the majority because they had disqualifying white coat colour. Cryptorchidism was observed in 9.8% of the male pups born and in 13.4% of the male pups that were registered.

CONCLUSION

The Boxer suffers a high frequency of dystocia, mainly due to uterine inertia, but also fetal malpresentation. Breeders should be advised to include easy whelpings in their breeding program.

A short sperm–oocyte incubation time ZBA in the dog

The fertilising capacity of a semen sample can be predicted by evaluation of spermatozoa with in vitro tests. The zona pellucida binding assay (ZBA) accounts for several parameters and interprets the interaction between the spermatozoa and the oocyte. The present study was made in two parts. The aim of the first experiment was to evaluate whether the sperm binding capacity of oocytes varies between different oocyte pools. Each zona binding was made with oocytes from different bitches, using pooled frozen-thawed semen from the same two dogs. The sperm-oocyte complexes were incubated for 1h. There was a significant difference between the six replicates in the number of sperm bound to the zona pellucida (ZP), which indicates that the sperm binding capacity of the ZP differs between oocyte pools. The aims of the second experiment were to evaluate the effects of five different treatments of the spermatozoa on the ZBA, and to evaluate two different incubation times of the sperm-oocyte complexes. ZBAs were made with: fresh semen; semen kept chilled for 1 or 2 days prior to the ZBA; and with semen that had been frozen with or without Equex. The oocytes and spermatozoa were incubated for 1 or 4h. For fresh semen and for semen frozen without Equex, incubation for 1h resulted in a higher number of bound spermatozoa per oocyte than incubation for 4h (P<0.0001). When the effect of the different sperm treatments on the number of spermatozoa bound to the ZP was evaluated, it was found that this number was higher for fresh spermatozoa than for chilled or frozen-thawed spermatozoa both after 1 and 4h of co-incubation (P<0.0001). After 1-h incubation of the sperm-oocyte complexes, spermatozoa chilled for 1 day showed better zona binding capacity than spermatozoa chilled for 2 days, and spermatozoa frozen without Equex had a better zona binding capacity than spermatozoa frozen with Equex. Sperm motility and sperm plasma membrane integrity were higher in fresh than in chilled and frozen-thawed semen. The acrosome integrity was high in all groups of treated semen. In conclusion, 1-h incubation of the sperm-oocyte complexes seems to be sufficient for fresh and chilled semen. Further studies are required to establish the optimal incubation time for sperm-oocyte complexes when frozen-thawed semen is evaluated, as a comparison between semen frozen with Equex and semen frozen without Equex gave different results depending on whether the incubation time was 1 or 4h (in the present study), or 6h [Ström Holst B, Larsson B, Linde-Forsberg C, Rodriguez-Martinez H. Evaluating chilled and frozen-thawed dog spermatozoa using a zona pellucida binding assay.

Cervical patency during non-ovulatory and ovulatory estrus cycles in domestic cats

The cervix functions as a barrier to spermatozoa. Vaginal artificial insemination in cats is, therefore, likely to be successful only at the period of estrus when the cervix is open. This study aimed to define the period of cervical patency in cats in both non-ovulatory and ovulatory estrus cycles. A total of 15 reproductive cycles were studied in six cats during the estrous stage. Cervical patency was monitored with the cats under sedation, by infusing 2 mL of Iohexol contrast medium via a 3.5 French tomcat catheter into the cranial vagina during estrus. Day one of estrus was defined as the first day the cats showed estrous behavior. Non-ovulatory cycles were characterized by a serum progesterone concentration on days 11-15 that was below 5 nmol/L and a normal interestrus interval of 7-14 days. Ovulatory cycles were characterized by a serum progesterone concentration on days 11-15 that was above 5 nmol/L and an interestrus interval that exceeded 30 days. The cervix was considered to be open when the contrast medium was seen to enter the uterus, and to be closed when the contrast medium remained in the vagina. Blood samples were collected at each examination and were assayed for estradiol-17beta and progesterone concentrations. The cervix was open on the first day of standing estrus at a mean estradiol-17beta serum concentration of 87.4+/-21.8 pmol/L (range 14 to >or=180 pmol/L) and closed at an estradiol concentration of 47.1+/-12.4 pmol/L (range 4 to >or=180 pmol/L). In the ovulatory cycles the cervix was closed at a progesterone concentration of 9.8+/-4.4 nmol/L (range 0.6-28.4 nmol/L). There was no difference in the duration of cervical patency in non-ovulatory and ovulatory cycles (5.5+/-1.2 days and 5.2+/-0.5 days, respectively) (p>0.05). The higher overall mean concentrations of estradiol-17beta seen in the ovulatory cycles than in the non-ovulatory cycles, indicate that a high level of estradiol is necessary for induction of ovulation. Ovulation in 60% of unmated females in this study indicates that the techniques used for evaluation of cyclus stage and cervical opening have the potential to induce ovulation in the cat. This study demonstrates that cervical patency is not influenced by the occurrence of ovulation, but is due to individual variations between cats.

Freezing of stored, chilled dog spermatozoa

The aims of this study were to find out if dog spermatozoa can be stored chilled for 1 or 2 days prior to freezing without a deterioration in post-thaw vitality and longevity, and to compare two extenders; the Uppsala Equex-2 (UE-2) and a TRIS egg yolk extender (EYT). Pooled dog semen was frozen immediately after collection, or was extended and stored at 4 degrees C for 1 or 2 days before freezing. Sperm motility and acrosome integrity were evaluated before freezing and for 6h post thaw at 38 degrees C, while sperm plasma membrane integrity was evaluated post thaw. There were no effects of pre-freeze storage time or extender on post-thaw motility or plasma membrane integrity, but a significant effect of extender (P < 0.0153) on post-thaw acrosomal integrity was found, UE-2 being better than EYT. There was a significant (P < 0.0001) negative effect of post-thaw storage time on acrosome integrity, but this was not influenced by pre-freeze storage time or extender. In conclusion, we found that dog spermatozoa can be frozen after 1 or 2 days of cold storage without significant deterioration in post-thaw motility, acrosome integrity or sperm plasma membrane integrity compared to when frozen immediately after collection. The UE-2 extender was superior to the EYT extender for freezing of cold stored dog spermatozoa.

Hysterographic appearance and uterine histology at different stages of the reproductive cycle and after progestagen treatment in the domestic cat

The aims of this study were to characterize the hysterographic and histological features of the uteri and to perform immunohistochemistry with proliferating cell nuclear antigen (PCNA) in the cat endometrium at various stages of the reproductive cycle and after treatment with exogenous progestagen. Seventy-four female domestic cats submitted for routine ovariohysterectomy were categorized into six groups: inactive (n=20), follicular (n=9), luteal (n=18), and postpartum (n=12) stages of the reproductive cycle; cats given medroxyprogesterone acetate for estrus prevention (MPA group) (n=12); and cats with uterine pathological lesions (n=3). Hysterography was performed and the relation of the uterine and luminal shape in the hysterogram with the stage of the reproductive cycle as well as with any pathological conditions of the uterus was evaluated. The uteri and ovaries were thereafter surgically removed and sectioned for histological examination. The PCNA was used to demonstrate the expression of endometrial epithelial cell growth. The hysterographic appearance was found to differ between the six groups of cats. A straight uterine cavity was characteristic for cats in the inactive stage, whereas a wavy uterine cavity was characteristic for cats in the follicular stage. In the luteal stage, the luminal cavity of the uteri differed in shape with increasing progesterone concentration from straight to irregular wavy or coiled. The coil shaped uterine lumen seen in the MPA treated and pathological groups was considered also to be an expression of a progestagenic effect. Waviness and coiling of the uterine lumen was related to a proliferation of the endometrial glands, whereas irregular filling defects were indicative of endometrial cystic changes. This study is the first to demonstrate the expression of PCNA in the cat endometrium although no differences were found between the six groups of cats. The hysterographic appearance was found to differ according to stage of the reproductive cycle and pathological conditions. Thus, a normative hysterogram is now available for diagnosing the reproductive stage and uterine changes in cats developing endometrial hyperplasia with and without cystic changes.

Influence of glucose and fructose in the extender during long-term storage of chilled canine semen

The use of chilled, extended semen in dog breeding is becoming increasingly popular as preparation and transportation is less expensive and regulations are often less complicated than for frozen semen. Sugar is one of the main constituents in semen extenders, and glucose and fructose are metabolized in separate pathways by freshly ejaculated dog sperm. In this study, glucose, fructose or an equal mixture of both were used in an egg-yolk-tris (EYT) extender at two different concentrations (10 and 70 mM). EYT extender without sugar supplementation, providing only the glucose (3-4 mM) originating from the egg-yolk, served as a control. The longevity of the chilled semen at 5 degrees C was 23 days: the quality of physical and functional characteristics decreasing with time. Glucose and fructose had a strong influence on motility and movement patterns of chilled canine semen. The beneficial effect of 70 mM sugar concentrations compared to 10 mM and the control was pronounced, and maintained sperm motility > or = 70% for 8 days of storage, compared to for 4 days in the control extender. Fructose maintained higher sperm motility than did glucose and the mixture. VAP values were higher in sugar-supplemented extenders (P < 0.05). Neither type nor concentration of the two sugars influenced sperm plasma membrane, acrosome integrity or the acrosome reaction following ionophore challenge (ARIC). Sugar consumption by dog sperm varied between the different periods of storage and with sugar concentrations provided in the extenders. Glucose consumption by dog sperm was greater than fructose consumption when both sugars were present in equal amounts, indicating that dog sperm used glucose in preference to fructose. In conclusion, the major influence of the two sugars on chilled semen was to support motility. EYT extender supplemented with fructose at a concentration of 70 mM was found to be the best of the tested extenders for long-term preservation of chilled canine semen.