Prediction of the optimal time for insemination using frozen-thawed semen in a multi-sire insemination trial in bitches

Evidence-based practice in canine artificial insemination

A number of methods are currently used to predict the optimal date of insemination of the breeding bitch, particularly with the use of frozen-thawed canine semen which has a far shorter lifespan than fresh semen. Aside from confirming cytological oestrus, vaginal cytology is of no assistance in predicting the most fertile day(s) in a bitch; however, a neglected avenue of research suggests that vaginal cytology may be of great importance in confirming the days of optimal fertility retrospectively. Similarly, vaginoscopy provides clues as to the stage of a bitch's cycle but is inadequate as a sole determinant of her most fertile days. Nevertheless, vaginoscopy is useful to identify very late oestrus and the onset of dioestrus, as well as Stage I of labour (cervical dilatation). Due to variations in the rate at which circulating progesterone concentrations rise in individual bitches, the reliability of circulating progesterone concentrations for determining the optimal day(s) of insemination with frozen-thawed semen decreases as values rise. Moreover, progesterone assay results can vary widely due to extrinsic factors such as the time of blood sampling, sample storage conditions and the assay employed. Finally, this review investigates evidence surrounding various insemination routes and suggests that well-performed vaginal insemination, even with frozen-thawed semen, may be an acceptable approach for cases where transcervical insemination is impractical.

Assessment of Vcheck® analyzer for rapid progesterone concentration measurement including recommendations for achieving the optimal breeding time in bitches

Background and Aim

Serum progesterone concentration plays critical role in determining the optimal breeding time in bitches and diagnosing reproductive-related issues. This study aimed to conduct a comparative analysis of serum progesterone results obtained from commercial point-of-care immunological analyzers, namely, Vcheck®, with those obtained using chemiluminescent microparticle immunoassay (CMIA). Our overarching goal was to evaluate these analyzers' accuracy and establish standardized guidelines for optimal breeding timing.

Materials and Methods

Ninety-four serum samples from bitches were analyzed using the Vcheck® analyzer and compared with CMIA. Thorough documentation included the mean, standard deviation, 95% confidence interval (CI), and minimum and maximum values of serum progesterone concentrations. Furthermore, Pearson's correlation coefficient, Lin's concordance correlation coefficient, and the bias correction factor were meticulously recorded.

Results

The mean progesterone concentration measured using the Vcheck® analyzer was significantly lower than that measured using CMIA, with a mean difference of 1.26 ng/mL of serum. The Bias correction factor was 0.935, which was nearly 1.00, indicating that the line of best-fit was on the perfect line of agreement, providing insight into the measurement accuracy. Pearson's correlation coefficient, a measure of precision, was also close to 1 (0.939), confirming the reliability of the data. Furthermore, Lin's concordance correlation coefficient was 0.877, indicating a fair overall agreement between the Vcheck® and CMIA methods. These results support the validity of the Vcheck® analyzer's results. The present study was developed by aligning with established CMIA guidelines and adapting them using the range and 95% CI derived from each set of results, ensuring a standardized and rigorous approach.

Conclusion

The Vcheck® analyzer provides a rapid assessment of serum progesterone concentration in bitches, with results comparable to those measured using the CMIA technique. However, when considering the use of the Vcheck® analyzer, it is recommended that the results should be interpreted carefully and the interpretation guidelines should be followed. In conclusion, Vcheck® provides a reliable and convenient method for veterinarian practitioners to measure canine progesterone levels in a clinical/hospital setting.

Validation of a dry-slide immunoassay for progesterone analysis in canine plasma in a clinical setting

BACKGROUND

The identification of canine ovulation is critical for successful breeding. Progesterone measurements are useful for identifying ovulation. Progesterone assays are also quantitative and easily accessed, making them valuable in veterinary practice.

OBJECTIVES

We aimed to validate a dry-slide immunoassay (DSI) for use in dogs, including a method comparison with the chemiluminescence assay (CLIA) and mass spectrometry.

METHODS

Twenty-nine bitches were prospectively recruited. Accuracy, precision, interference, and stability were evaluated. Method comparison between DSI and CLIA and mass spectrometry was conducted, and bias was calculated.

RESULTS

Repeatability was 8.0%-10.8%, and within-laboratory imprecision was 8.8%-11.1% for four concentration levels. Recovery under dilution was 61%-100%, and the method was linear to a concentration of ~50 nmol/L. Recovery after the addition of a high progesterone sample was 76%-83%. Minor changes were seen in one hemolytic and two lipemic samples. Storage at room temperature for 12-24 hours resulted in concentrations that were 57%-96% of the initial concentrations. For samples frozen at -80°C, the concentrations were reduced 17%-27%. There was a significant difference between results from the DSI and CLIA, and a proportional bias was seen when DSI was compared with mass spectrometry, where CLIA correlated better than DSI.

CONCLUSIONS

Precision and accuracy were acceptable. A proportional bias was seen between DSI and CLIA. A small amount of interference was seen with hemolysis and lipemia. Progesterone concentrations were decreased in samples stored at room temperature and -80°C. The results support the use of the DSI for ovulation timing but not for artificial insemination with frozen semen since progesterone concentrations might exceed the assay's linearity and precision limits.

Effects of age, size and season on cryotolerance of dog semen - A retrospective analysis

In a retrospective analysis of 508 ejaculates from 297 dogs, efficiency of semen cryopreservation and effects of age, season and dog size on characteristics of fresh and cryopreserved semen were evaluated. Volume of the sperm-rich ejaculate fraction increased to 10 years of age, decreased in 10 and 11-year old dogs (P < 0.001) but did not differ among seasons. Total sperm count was less in 10 and 11-year-old dogs (P < 0.001). The percentage of progressively motile, membrane-intact and morphologically normal spermatozoa before cryopreservation was least in 10 and 11-year-old dogs (P < 0.001). Cryopreservation resulted in less progressively motile spermatozoa (P < 0.001) with this being most pronounced in 10 and 11-year-old dogs (cryopreservation x age P = 0.004). The cryopreservation-induced decrease in morphologically normal spermatozoa (P < 0.001) was not affected by dog body weight. Number of cryopreserved AI doses differed among age groups (P < 0.001) and was less in 10 and 11-year-old dogs (median 1.5) compared with younger dogs (6-7 years, median 4.3). When ejaculates were grouped by a threshold of ≥ 35% progressively motile spermatozoa after freezing-thawing, 86.5% of all ejaculates were greater the threshold but this percentage decreased to 66% in 10 and 11-year-old dogs (P < 0.001). In conclusion, sperm cryotolerance is consistent for much of a dog´s lifespan but decreases after a certain age. Dog semen can be cryopreserved successfully throughout the year. Post-thaw semen characteristics were not different among cryopreserved ejaculates obtained from dogs differing in body weight.

Accuracy and precision guidelines for optimal breeding time in bitches using in-house progesterone measurement compared with chemiluminescent microparticle immunoassay

Background and Aim:

The concentration of serum progesterone is commonly used to determine the optimal mating time in bitches, and to diagnose reproductive-related abnormalities. This study aims to compare the serum progesterone results obtained by rapid fluorescence immunochromatography assay (RFICA) with those obtained by chemiluminescent microparticle immunoassay (CMIA) from the same serum samples to develop a standard guideline for optimal breeding time.

Materials and Methods:

Serum progesterone levels were measured in 124 bitches using RFICA and CMIA. Simple linear regression and correlation analyses were performed to analyze the data. The percentage difference between the maximum and minimum progesterone values in the same serum sample in the same assay was compared using Wilcoxon’s rank-sum test.

Results:

The present study showed a strong linear dependence of the results obtained by RFICA on those obtained by CMIA as R²=0.8976, with regression coefficient of 0.9474 and p<0.05, including the regression model was CMIA = (0.9483 × RFICA) − 0.761. Moreover, five critical measurement times during estrous in bitches showed statistically significant differences (p<0.05), except at the fertilizable period, which showed a non-significant difference (p>0.05).

Conclusion:

This study demonstrated that it is presumably acceptable to use the RFICA and CMIA methods interchangeably for quality progesterone measurements in serum samples from bitches. However, when considering the use of the RFICA method, it is advisable to carefully interpret the results and follow the interpretation guidelines. Finally, RFICA in the present study provides a reliable and convenient option for veterinarian practitioners to measure canine progesterone levels in-house.

Factors influencing parentage ratio in canine dual-sired litters

Breeding a bitch with two different sires during a single estrous cycle has the potential to facilitate rapid genetic gain and improve reproductive performance within a canine breeding colony. There is limited data regarding the factors that contribute to the success of dual-sired litters in domestic dogs, and only anecdotal evidence suggesting that these litters rarely produce offspring from more than one sire. The objective of this prospective clinical study was to investigate multiple factors that likely affect the success of dual-sired litters on whelping rate, litter size and parentage ratio. These factors include: timing of artificial insemination (AI), order of sires, number of AI's per cycle, semen type, sperm quality and age of sire and bitch. Data collected over a 10 year period from twenty-nine estrous cycles (28 individual bitches of 10 different breeds) were evaluated after an initial AI with frozen semen from the 'genetically desired' sire and followed up with a second AI with either fresh (n = 9) or frozen (n = 16) semen or natural mating (n = 4) from a different, 'back up', sire. DNA parentage of each pup born was determined by using a primary panel of 288 SNPs. The whelping rate and litter size from previous single sire inseminations per estrous cycle, in the same bitches, (n = 16) over 25 estrous cycles using either fresh (n = 4) or frozen-thawed (n = 21) semen, were analyzed as controls. Of the 29 dual-sired breedings, 26 bitches whelped (89.7%), and 8 litters (30.8%) were of mixed parentage. In the litters of mixed parentage after a dual-sired breeding, a greater proportion of the offspring were from the second sire than the first sire (73.0% and 27.0% respectively; P < 0.05). Interestingly, in litters where all pups were of single sire parentage after a dual-sired breeding, 50.0% of the offspring were by the first sire and 50.0% were by the second sire. For litters of mixed or single paternity produced by dual-sired breeding there was no difference in average litter size. However, on a per estrous cycle basis for each bitch the whelping rate (89.7% v. 76.0%.) and litter size (5.5 ± 2.5 v. 4.0 ± 2.78) of all dual-sired breedings were greater (P < 0.05) compared to previous single-sired breedings (controls) respectively. This study demonstrates that offspring of mixed parentage derived from dual-sired breedings may be achieved. Furthermore, insemination with semen from two different sires may increase the whelping rate and litter size, which is an important consideration when using genetically valuable, or older individuals with potentially reduced fertility.

Comparison of progesterone assay by chemiluminescence or radioimmunoassay for clinical decision-making in canine reproduction

The Coat-A-Count® radioimmunoassay has been long and widely used to determine the concentration of progesterone in serum or plasma of bitches (progRIA), but was discontinued in 2014. The Immulite® 1000 LKPG1 chemiluminescence immunoassay has gained prominence since 2003 to determine the concentration of progesterone in serum of bitches, but the assay changed in 2012 (Immulite® 1000 LKPW1). This study assessed the feasibility of using Immulite® 1000 LKPW1 (progImm) to estimate the time of clinically relevant events during oestrus and compared progRIA and progImm 2 and 3 days after the first or only day of the luteinizing hormone surge (LH1). ProgImm first exceeded 5.1 nmol/L on the same day that progRIA first exceeded 6 nmol/L, a proxy for the occurrence of the LH surge, or the day before in 28 of 31 (90%) of oestrous periods. ProgImm first exceeded 13.6 nmol/L on the same day that progRIA first exceeded 16 nmol/L (a proxy for the day of ovulation) or the day before in 34 of 35 (97%) oestrous periods. ProgImm first exceeded 5.4 nmol/L on LH1 or the day before in 24 of 25 (95%) of oestrous periods. The median of progImm 2 days after LH1 was 1.2 nmol/L lower than the 10.7 nmol/L of progRIA (p = 0.001). The mean of progImm 3 days after LH1 was 2.2 nmol/L lower than the 19.0 nmol/L of progRIA (p < 0.001). In conclusion, the days on which progImm first exceeded 5.1 nmol/L, 13.6 nmol/L and 5.4 nmol/L effectively estimate the days on which progRIA reached 6 nmol/L or 16 nmol/L or LH1.

Normal progesterone profiles during estrus in the bitch: A prospective analysis of 1420 estrous cycles

Appropriate timing of insemination in the bitch, through monitoring of serial serum progesterone concentrations, has historically been based on the detection of important physiological reproductive events which include the LH surge and ovulation 2-3 days later. Previous hormone profile studies during the estrus period in the bitch, in which determination of these physiological reproductive events has been defined, have been based on low numbers of bitches of similar breeds and body weights. Therefore, the aim of this large-scale prospective study was to define the normal serum progesterone profile during the estrus period in a large number of bitches of various breeds and body weights. In addition, we investigated if the rate of change in progesterone concentrations during the fertile period affected the reproductive performance of bitches after insemination with either fresh or frozen-thawed semen. A total of 1300 individual bitches, representing 84 different breeds, contributed 1420 estrous cycles and 4213 serum progesterone values over the 11-year (2007-2017) study period. The mean (±SD) progesterone concentration at estimated LH0 was 2.7 ± 0.6 ng/ml and at the time of estimated ovulation it was 4.8 ± 0.9 ng/ml and 7.2 ± 1.3 ng/ml (LH+2 and LH+3 respectively). There was no difference in the shape of progesterone profiles for bitches of different body weights. Furthermore, mean progesterone concentrations on each day between LH-6 and LH+7 were not different amongst bitches of different breeds and body weights and there was no effect of mean progesterone concentrations on any day on whelping rate or litter size. However, there was a significant effect of the rate of change in progesterone concentrations on litter size when frozen semen was used. The litter sizes of bitches inseminated with frozen semen with slow progesterone curves were significantly smaller compared to bitches with fast progesterone curves (3.9 ± 1.8 vs 5.6 ± 3.1 pups per litter respectively; P < 0.001). There was no effect of bitch age on the normal progesterone curve, or its rate of change. This is the first report of the normal progesterone profile during estrus in the bitch derived from a large number of serial progesterone measurements obtained from bitches of various breeds and body weights. Importantly, the predictability and reliability of this progesterone profile regardless of breed or body weight gives clinicians the confidence to accurately determine the optimal time for insemination, which is critical to reproductive success, especially when frozen semen is used.

Comparing the values of progesterone in the blood of bitches as measured with a chemiluminescence immunoassay and a radioimmunoassay

A ¹²⁵ I radioimmunoassay (RIA) has long been used to determine the value of progesterone in serum or plasma of bitches but was discontinued in 2014. A chemiluminescence immunoassay (CLIA) gained prominence since 2003 to determine the value of progesterone in serum of bitches but the assay changed in 2012. This study assessed the agreement between progesterone values obtained with RIA in plasma (progRIA) and with the post-2012 CLIA (progCLIA) in the serum of bitches. ProgCLIA was determined in 110 serum samples from 40 bitches in pro-oestrus or early oestrus and compared to progRIA in plasma samples collected from the same bitches at the same time, where progRIA had a uniform distribution between 0.5 and 25 nmol/L. Two replicate analyses of each serum or plasma sample were simultaneously done in the same assay. For RIA and CLIA, the intra-assay CVs were 5.85% and 6.70% and the interassay CVs 8.45% and 9.16%. For RIA and CLIA the progesterone values obtained with replicate analyses differed by as much as 11%-31% in 25% of samples. On average, the value of progCLIA was 85% of that of progRIA (95% CI 58%-112%, n = 110), with 88% of progCLIAs being lower than the progRIAs. This study shows that RIA and CLIA may yield replicate values that differ by as much as 11%-30% in about a quarter of samples analysed, necessitating replicate analyses if precise values are required. The study provides an equation by which to estimate progCLIA from progRIA.

Blood periovulatory progesterone quantification using different techniques in the dog

Blood progesterone concentration is used in several procedures related to the reproduction in the bitch, such as ovulation monitoring, estimating time of parturition, or hypo-luteoidism management. Several techniques are available to evaluate blood progesterone concentration, such as the radioimmunoassay (RIA), the chemiluminescent immunoassay (CLIA), and the enzyme-linked immunosorbent assay (ELISA). The aim of this study was to compare the blood progesterone concentration using these three methods during the periovulatory period of 23 bitches. Vaginal cytology was used to classify cytologic estrus (CE) and cytologic diestrus (CD), and blood samples were collected once during proestrus and every other day between CE and CD. The samples were retrospectively classified in the different phases of the estrus based on CD. Pregnancy rate and gestational length were also recorded. A significant increase of the circulating progesterone during the progression of the estrus was recorded, and there were significant differences in the values when using the different methods, with lesser, intermediate, and greatest values with use of the RIA, CLIA, and ELISA, respectively. There was a high correlation (Pearson's correlation coefficient = 0.978) and substantial strength-of-agreement (Lin's concordance correlation coefficient = 0.966) between values obtained when using CLIA and RIA, while there was a high correlation (Pearson's correlation coefficient = 0.955) but poor strength-of-agreement (Lin's concordance correlation coefficient = 0.866) with use of the ELISA and RIA. The data reported in this study provide evidence that the method used for measuring the blood progesterone concentration during the periovulatory phase of the bitch significantly affected the progesterone values.

The precision of predicting the time of onset of parturition in the bitch using the level of progesterone in plasma during the preparturient period

Precise prediction of the time of onset of parturition in the bitch is of clinical importance. Many parturition management cases in clinical practice are presented in the last two weeks of pregnancy without a reliable estimate of the parturition date. The aim of this study was to assess the value of a single progesterone level in the blood plasma from a preparturient bitch to predict the time of onset of parturition. The temporal relationship between the decrease in the plasma progesterone levels and the time of cervical dilatation (TCD)-which correlates to the onset of stage 1 of parturition-was evaluated in 25 bitches in the preparturient period. Among bitches destined to reach TCD within 12 h there is a 2% probability of having a plasma progesterone level of 15.8 nmoL/L or above and a 6% probability of having a level of 8.7 nmoL/L or above. Conversely, if the level is below 8.7 nmoL/L there is a 99% probability of reaching TCD within 48 h and if the level is below 3.18 nmoL/L there is a 100% probability of reaching TCD within 24 h. These results allow the veterinary obstetrician to make prompt decisions in the management of parturition.

Estimated impact of multiple conceptuses per follicle on fecundity in the bitch

Multiple conceptuses from one follicle due to multi-ovular follicles or monozygotic twins inflate the ratio between the numbers of conceptuses and corpora lutea and possibly the effect ascribed to experimental treatment. The aim of this study was to estimate the impact of multiple conceptuses per follicle on fecundity in the bitch. The numbers of conceptuses and corpora lutea of 105 bitches originated from 7 published experimental studies and of 132 from ovariohysterectomies done in a private practice and a welfare organisation. Ninety five bitches, producing 597 conceptuses, had at least as many conceptuses as corpora lutea; 83 had as many, 10 had one more and 2 had 2 more. Bootstrap resampling on these 95 bitches let us to conclude that 12.6% of bitches are expected to produce more oocytes that are each capable of yielding a conceptus than the number of follicles that ovulate and that 2.35% of conceptuses are expected to be in excess of the number of follicles that ovulate. Applying the results of the current study to 2 earlier studies showed that multiple conceptuses from one follicle may, at maximum, have increased the effect ascribed to prostatic fluid by 0.022 and 0.024 conceptuses per corpus luteum, which is minor in relation to the magnitude of the ascribed effects of 0.34 and 0.22 conceptuses per corpus luteum. The number of conceptuses relative to the number of corpora lutea provides a valid and precise measurement of fertility in the bitch.

The use of infrared thermography to detect the stages of estrus cycle and ovulation time in anatolian shepherd dogs

BACKGROUND

The aim of the study is to evaluate the effectiveness of thermographic monitoring, using the temperature changes of perianal and perivulvar areas for the determination of estrus in Anatolian Shepherd bitches. Fifteen bitches were used in the study. Blood and vaginal smear samples were collected and thermographic monitoring of perianal and perivulvar areas were carried out starting from proestrus to early diestrus. Also, external signs of estrus were investigated. Smear samples were evaluated by light microscopy after Diff-Quik staining method and superficial and keratinized superficial cells were determined as percentage (S + KS%). Progesterone and luteinizing hormone measurements were done by radioimmunoassay. The difference in temperature between perianal and perivulvar areas was evaluated through thermographic images by FLIR ResearchIR Software.

RESULTS

According to the results obtained from the study, differences between progesterone and S + KS% were statistically significant (P < 0,05). Although temperature showed increase and decrease with progesterone and S + KS%, the differences were not important statistically (P > 0,05). Serum luteinizing hormone levels did not sign any difference (P > 0,05).

CONCLUSIONS

As a result, thermographic monitoring alone is not enough for estrus detection in Anatolian Shepherd bitches. However, it can be used to assist the actual estrus detection technique in terms of providing some foreknowledge by evaluating the differences in temperature.

The precision of peri-oestrous predictors of the date of onset of parturition in the bitch

Precise prediction of the date of onset of parturition in the bitch is clinically important. The study compared the precision with which four peri-oestrous predictors predict the date of onset of parturition. The predictors evaluated in 24 bitches were: the date of the first or only day of the LH surge, the date on which the concentration of progesterone in the blood plasma first exceeded 6 nmol/L, the date on which the concentration of progesterone in the blood plasma first exceeded 16 nmol/L and the date of onset of cytological dioestrus. Among the 24 bitches, the date of onset of cytological dioestrus predicted the date of onset of parturition with greater precision than the other three predictors. Following the evaluation of another 218 intervals between the onset of cytological dioestrus and the date of onset of parturition, it was shown that the onset of cytological dioestrus predicted the date of onset parturition with a precision of ±1 d, ± 2 d and ±3 d in 88%, 99% and 100% of the 242 pregnancies. This study concludes that the first day of cytological dioestrus is a useful predictor of the date of onset of parturition.

Laboratory and Clinical Evaluation of a Feia Method for Canine Serum Progesterone Assay

The evaluation of progesterone (P4) concentration is a valuable tool in assessing physiological reproductive events and reproductive disorders in bitches. A reliable and rapid (preferable, point of care) determination of P4 is advisable in most cases. Aims of this study were to evaluate a fluorescence enzyme immunoassay (FEIA) for canine serum P4 concentration by (i) the agreement with liquid chromatography-tandem mass spectrometry (LC/MS/MS), (ii) the association with vaginal cytology and (iii) the accuracy in the prediction of the parturition date calculated from the estimated day of ovulation. Serum samples were collected from client-owned bitches presented between 2011 and 2014 for the evaluation of their oestrous cycle, pregnancy or reproductive disorders. The agreement between FEIA and LC/MS/MS, evaluated on 19 samples, was statistically significant (R(2) = 95.7%, p < 0.001), although FEIA showed significantly higher values than LC/MS/MS (p < 0.05). In the different phases of oestrous cycle, as determined by vaginal cytology, P4 concentrations (by FEIA) were statistically different (p < 0.05): anoestrus (n = 7) 0.38 ± 0.14 ng/ml, proestrus (n = 14) 1.04 ± 0.67 ng/ml and oestrus (n = 72) 6.8 ± 7.26 ng/ml. Mean pregnancy length from the estimated day of ovulation was 62.9 ± 1.8 days. In 13 of 22 (59.1%), 19 of 22 (86.3%) and 21 of 22 (95.5%) bitches pregnancy lasted 63 ± 1, 63 ± 2 and 63 ± 3 days, respectively. Three pregnancies were outside the 61-65 days range (60, 60 and 67 days). In conclusion, the FEIA method employed can be considered reliable and, in association with vaginal cytology, effective in evaluating the canine oestrous cycle.