The estrous cycle in the dog: a review

Augmenting interpretation of vaginoscopy observations in cycling bitches with deep learning model

Successful identification of estrum or other stages in a cycling bitch often requires a combination of methods, including assessment of its behavior, exfoliative vaginal cytology, vaginoscopy, and hormonal assays. Vaginoscopy is a handy and inexpensive tool for the assessment of the breeding period. The present study introduces an innovative method for identifying the stages in the estrous cycle of female canines. With a dataset of 210 vaginoscopic images covering four reproductive stages, this approach extracts deep features using the inception v3 and Residual Networks (ResNet) 152 models. Binary gray wolf optimization (BGWO) is applied for feature optimization, and classification is performed with the extreme gradient boosting (XGBoost) algorithm. Both models are compared with the support vector machine (SVM) with the Gaussian and linear kernel, k-nearest neighbor (KNN), and convolutional neural network (CNN), based on performance metrics such as accuracy, specificity, F1 score, sensitivity, precision, matthew correlation coefficient (MCC), and runtime. The outcomes demonstrate the superiority of the deep model of ResNet 152 with XGBoost classifier, achieving an average model accuracy of 90.37%. The method gave a specific accuracy of 90.91%, 96.38%, 88.37%, and 88.24% in predicting the proestrus, estrus, diestrus, and anestrus stages, respectively. When performing deep feature analysis using inception v3 with the same classifiers, the model achieved an accuracy of 89.41%, which is comparable to the results obtained with the ResNet model. The proposed model offers a reliable system for identifying the optimal mating period, providing breeders and veterinarians with an efficient tool to enhance the success of their breeding programs.

Progesterone Analysis in Canine Breeding Management

Progesterone is a worthwhile addition to the clinical assessment of cycle stage for breeding, elective cesarian delivery, and reproductive management in the bitch if reliably measured. Clinical decisions based on systemic progesterone concentrations also require the rapid return of results. Most commercially accessible analyses capable of returning results within a day still rely primarily on immunoassays of one kind or another. Point-of-care instruments utilizing similar technology have been developed more recently to enable results to be generated in-house. Repeated monitoring of progesterone on whatever platform can be useful if consistent collection and analysis protocols ensure acceptable precision, accuracy, and repeatability.

Ovarian and uterine changes during the oestrous cycle in female dogs

CONTEXT

An accurate staging of sexual cycle is essential for the optimum timing of medical interventions.

AIMS

Here, an updated insight into clinical, endocrinological and vagino-cytological parameters, and their correlation with histomorphology of ovarian and uterine tissue samples is presented.

METHODS

Samples from 39 dogs were collected at various stages of the oestrous cycle: pro-oestrus (n =8), oestrus (n =12), dioestrus (n =9) (luteal phase) and anoestrus (n =10), according to clinical observations. Final allocation of samples was done after histomorphological evaluation of all tissues. Peripheral oestradiol-17ß (E2) and progesterone (P4) concentrations were measured, P4 by both chemiluminescent immunoassay (CLIA) and radioimmunoassay (RIA).

KEY RESULTS

Differences were observed between determination of the stage of the oestrous cycle, either by clinical, endocrinological or histomorphological evaluation. Individuals considered to be in clinical and endocrinological oestrus, had entered the luteal phase according to histomorphology. P4 concentrations measured by two different assays differed, underlying the importance to understand that absolute P4 concentrations may deviate depending on the used assay. Comparison of E2 and P4 concentrations is suggested to be useful when defining the transition from early follicular phase to the time of ovulation.

CONCLUSIONS AND IMPLICATIONS

Based on parallel histomorphological observations, combined with clinical and endocrinological findings on the same individuals, the present study emphasises that an accurate classification of the stage of the cycle in female dogs based solely on clinical and endocrinological assessments can be difficult. The histomorphological findings presented herein provide new insights into the transitional phases between the different stages of the oestrous cycle in the dog.

Modelling gestational diabetes mellitus: large animals hold great promise

Gestational diabetes mellitus (GDM) characterized by hyperglycemia during pregnancy is a risk factor for various maternal and fetal complications. The key pathophysiological mechanisms underlying its development have not been elucidated, largely due to the lack of a model that accurately simulates the major clinical and pathological features of human GDM. In this review, we discuss the refined criteria for an ideal animal model of GDM, focusing on the key clinical and pathophysiological characteristics of human GDM. We provide a comprehensive overview of different models and currently used species for GDM research. In general, insulin insufficiency consequent to pancreatic β-cell death represents the current leading strategy to mimic human GDM-like hyperglycemia in animals. Nonetheless, these models have a limited capacity to mimic the natural history of GDM, the marked alteration in circulating estrogen/ progestogen, obesity and its related metabolic complications. We discuss emerging evidence of the increased susceptibility to GDM in rodents and large animals with genetic modifications in pregnancy-related hormones. An appraisal of current GDM models suggests that a combination strategy involving dietary stress, pregnancy-related hormones, insulin resistance and metabolic disorders might enable the development of better GDM models and expedite the translation of basic research findings to GDM treatment.

Revisiting canine pseudocyesis

Canine (Canis familiaris) pseudocyesis, pseudopregnancy, false pregnancy or nervous lactation is a frequent syndrome observed in non-pregnant, late diestrous or early anestrous females that is characterized by different degrees of mammary gland enlargement, maternal behavior and lactation. Further education about this frequent canine physiological event is still necessary to ensure optimal diagnosis and treatment strategies. Thus, the aim of this article was to review and update the physiopathology, physical and behavioral signs, diagnosis, treatment and prevention of pseudocyesis in bitches in which it is a clinical problem.

Species Comparison of Postnatal Development of the Female Reproductive System

The postnatal development of the female reproductive system in laboratory animals and humans is reviewed. To enable a meaningful species comparison of the developing female reproductive system, common definitions of developmental processes were established with a focus made on aspects that are similar across species. A species comparison of the key endocrine, morphologic, and functional (onset of ovarian cycles and ability to reproduce) features of postnatal development of the female reproductive system is provided for human, nonhuman primate, dog, rat, and also mouse, minipig, and rabbit where possible. Species differences in the timing and control of female sexual maturation are highlighted. Additionally, a species comparison of the type and timing of female reproductive ovarian cycles was compiled. Human development provided the frame of reference, and then other common laboratory species were compared. The comparison has inherent challenges because the processes involved and sequence of events can differ greatly across species. Broad strokes were taken to assign a particular average age to an event and are to be used with caution. Methods of evaluation of postnatal female reproductive development in laboratory animals are discussed. Lastly, control rodent data from one of the author's laboratory on vaginal opening, first estrus, estrous cyclicity, and the histopathology involved with the developing female rat and mouse are presented. The information provided in this review is intended to be a resource for the design and interpretation of juvenile animal toxicity testing and ultimately, the relevance of the data to characterize potential risks for women and girls. Birth Defects Research 110:163-189, 2018. © 2017 Wiley Periodicals, Inc.

Dog cloning with in vivo matured oocytes obtaining using serum estradiol levels for predicting time of ovulation

Dog cloning using in vivo-matured oocytes has been carried out for a decade. To obtain mature oocytes, serum progesterone (P₄) levels are used to evaluate ovulation. However, the accuracy of these methods is not sufficient. Thus, the aim of the present study was to verify the feasibility of serum estradiol (E₂) on canine ovulation determination as assessed by the percentage of dogs yielding mature oocytes. In vivo-matured oocytes were utilized for canine somatic cell nuclear transfer (SCNT), and serum P₄ and E₂ levels were assessed to determine ovulation and oocyte maturation. Canine serum P₄ and E₂ concentrations during both pro-estrus and estrus were analyzed by electrochemiluminescence immunoassay. The percentage of dogs yielding mature oocytes using each of the two ovulation prediction methods were compared, and correlations between the percentage of each method and temperature were analyzed. Following evaluation, oocytes were collected surgically, and a significantly higher percentage (P < 0.05) of dogs yielding mature oocytes was observed using E₂ (56.43%) for ovulation detection as compared with that using P₄ (39.60%). The percentage of dogs yielding mature oocytes using P₄ significantly lower (P < 0.05) than E₂ in autumn (P₄, 37.50% vs. E₂, 52.00%) and winter (P₄, 29.17% vs. E₂, 59.09%). Using E₂, the percentage was maintained at about 52.00-66.67% regardless of the season and temperature. Correlation analysis showed that the dynamic of percentage of dogs yielding mature oocyte using P₄ was highly correlated with environmental temperature (R_P4 = 0.862), whereas E₂ was not affected by temperature (R_E2 = 0.199). To determine whether serum E₂ could be used for ovulation prediction for canine cloning, ovulation of 25 and 19 dogs (P < 0.05) were predicted using P₄ or E₂ methods, respectively and two puppies, one from each ovulation prediction method, were obtained after SCNT and embryo transfer. Thus, compared with the P₄ method, E₂ was an accurate and reliable method for canine cloning.

Degeneration and apoptosis of endometrial cells in the bitch

The relationships between changes in plasma progesterone concentrations, degeneration of the luminal epithelium, the occurrence of apoptosis of endometrial cells and endometrial leucocyte populations in the bitch were determined. Mature bitches (n = 15) were euthanized and necropsied when in diestrus (Days 7-75, n = 12) or in anestrus (Days 10, 32 and 53). Degeneration of the luminal epithelium was observed in bitches in late diestrus (Days 38-75, n = 5) when plasma progesterone concentrations were decreasing and in anestrus (Days 10 and 32, n = 2) when plasma progesterone concentrations were < 0.5 ng/mL. Endometrial leucocyte populations increased after degeneration of the luminal epithelium (around Day 42 of diestrus). Apoptosis was mainly observed in the basal glandular epithelial cells and endothelial cells of blood capillaries in all except anestrous bitches. Very few apoptotic cells were found in the superficial glandular epithelial cells and stromal cells. Higher apoptotic indices were detected in the basal glandular epithelium on Days 12-42 of diestrus than at other stages. Therefore, apoptosis of glandular basal epithelial cells occurred mainly in early diestrus, degeneration of cells of the luminal epithelium occurred from mid-diestrus to early anestrus, and the increase in leucocyte numbers may have been a consequence and not a cause of luminal epithelial degeneration.

Concentrations of progesterone, prolactin and relaxin in the luteal phase and pregnancy in normal and short-cycling German Shepherd dogs

Twenty-two nonpregnant and 19 pregnant German Shepherd dogs were assigned to either a control group or a suspected short-cycling group, based on the interestrous interval (> or = 6 month and < 5 month, respectively) and data from previous pregnancies. Blood serum concentrations of progesterone and prolactin were determined from days 5 to 60 (day 0 = ovulation) for characterization of luteal function. In pregnant bitches, placental integrity was additionally assessed by relaxin concentrations. The nonpregnant, suspected short-cycling bitches had significantly lower progesterone concentrations than the controls, indicating decreased luteal activity both in the autonomous and prolactin-dependent period. In the pregnant suspected short-cycling bitches, unavoidable progesterone supplementation prevented assessment of luteal function; it may have suppressed prolactin secretion (significantly lower prolactin concentrations from days 20 to 60, compared with the pregnant control group), but deficient prolactin secretion affecting luteal function cannot be excluded. The significantly lower relaxin concentrations, together with a high incidence of embryonic death found in the pregnant, suspected short-cycling group, may indicate loss of placental integrity and may have caused decreased prolactin concentrations.

Changes in plasma lipoprotein during the oestrous cycle of the bitch

Five bitches were kept under controlled conditions of diet and exercise for up to four months. They were monitored at regular time intervals for fasting plasma concentrations of cholesterol, triacylglycerols and apolipoproteins AI and B. Lipoprotein cholesterol and triacylglycerol concentrations were also determined in the fasting plasma. Vaginal cytology and plasma progesterone were monitored at weekly intervals to determine the oestrous state of the bitches. Lipoprotein and apolipoprotein concentrations remained steady during anoestrus but large increases and wide fluctuations were shown in the concentrations of both cholesterol and triacylglycerols during metoestrus. Metabolic studies involving the measurement of lipids in canine blood must take into account the stage of oestrus of any bitches involved.

Luteolysis in early diestrous beagle bitches

To induce luteolysis early in diestrus, 15 mated beagles were treated with 250 microg/kg prostaglandin F2alpha (PG), administered subcutaneously twice daily for 4 d, from Day 5 to Day 8 after the onset of cytological diestrus. They were divided into three groups of five bitches each: Group 1 received PG only. Group 2 received PG and 20 microg/kg/day bromocryptine orally. Group 3 received PG and 0.1 mg/kg/day dexamethasone intramuscularly. Fifteen untreated beagles served as controls. In each of the three treatment groups, four of the five bitches (80%) underwent complete luteolysis and did not whelp. The three bitches which did not undergo luteolysis whelped normally. All control bitches whelped normally. It was concluded that luteolysis is possible in bitches early in diestrus and the inclusion of bromocryptine or dexamethasone did not appear to influence luteolysis.

Heterologous radioimmunoassay of fox LH: levels during the reproductive season and the anoestrus of the red fox (Vulpes vulpes L.)

A heterologous radioimmunoassay using ovine LH as the labeled hormone, canine LH as the standard, and an antiovine LH rabbit serum was validated for the measurement of fox LH. Physiological validation of the assay was evidenced by the high concentrations of LH at oestrus and following ovariectomy or the administration of LH-RH. Throughout the year, plasma LH levels demonstrate important variations, being low during and after the luteal phase (1.4 +/- 0.3 ng/ml) (mean +/- SE) and increasing during the second part of anoestrus (5.2 +/- 1.4 ng/ml). This latter increase might be correlated with that of androgens observed at the same period. Several LH rises preceded the preovulatory LH surge.