Estrus In Bitches Research Articles

Dynamics of progesterone, estradiol, cortisol, triiodothyronine and indicators of adaptive immunity concentrations in female dogs during estrus

In different periods of postnatal ontogenesis in dogs, as well as in other animals, there are critical physiological periods, the adequacy of which depends on immunoendocrine homeostasis. The estrus in bitches is a critical period because it lasts longer than in other mammals and has specific endocrine and immune changes in the body. In this study authors demonstrated the dynamics of changes in hormone content and indicators of adaptive cellular immunity in bitches during the estrus. Determination of these indicators does not require expensive laboratory equipment and is available in veterinary practice. Taking into account the fact that estrus in dogs lasts long enough, it is not clear enough what indicators and in what terms should be determined for predicting possible dysfunctions of the reproductive system and, as a result, premature impossibility of reproduction in bitches. The peak concentration of progesterone occurs on the 20th day of estrus, the reaction of the immune system, which is manifested by the maximum decrease in the phagocytic activity of neutrophils, should be noted. An increase in the concentration of estradiol on the 5th day of estrus, in contrast to progesterone, had the opposite effect on phagocytic activity of neutrophils, namely, the ability of neutrophils to phagocytosis increased. Further, we conducted clinical animals’ observations for three months after estrus for the possibility of inflammatory processes in the reproductive system development. According to the obtained indicators, no complications were found.

Changes in serum progesteron and 17beta-estradiol concentration after application of Suprelorin (4,7 deslorelin acetate) implant for estrus induction in bitches

Since bitches are monoestrous animals, their sexual cycle occurs much less often than other domestic animals, and their reproductive capacity is potentially less. That is why manipulations with the sexual cycle of bitches and their correction are gaining more and more interest. Estrus induction is essential to commercial breeding owners for several reasons. Understanding the processes that occur during each stage of the sexual cycle, it can be safely manipulated. There are many methods for stimulating estrus, but not all of them have found their practical application. The implant Suprelorin (4.7 mg Deslorelin), which is primarily registered for the pharmacological castration of dogs and cats, has also found its use for the induction of estrus in bitches, since at the beginning of its activities, it stimulates the secretion of gonadotropin (GnRH), which triggers the synthesis of follicle-stimulating and luteinizing pituitary hormones. This initial mechanism of action of Deslorelin implants is known as the flash effect and causes heat in almost 100 % of bitches. Despite numerous publications on the use of the implant, its impact is still being investigated. The article presents changes in progesterone and estradiol after using the Suprelorin implant for estrus induction and compares the course of an induced sexual cycle with a spontaneous one. The study was conducted on 13 sexually mature bitches, 7 of them received the Suprelorin implant no earlier than 150 days after the last estrus, and 6 of them were bitches with spontaneous estrus, which were included in the control group. The implant was removed at the beginning of estrus when the progesterone level increased above 3 ng/ml. In 6/7 females, this day fell on the 10th day after the implant was inserted, and in 1/7 – on the 9th. Ovulation occurred two days after the LH peak in all bitches from the experimental group, which corresponded to the 12th day in 6/7 bitches and the 11th day in 1/7 bitches from the introduction of the implant. The estradiol peak in the control group was observed faster than in the experimental group. It occurred on average on the 8th day (mediam 8 (7–9)) from the beginning of estrus, in one bitch on the 7th day, in three - on the 8th, and in two – on the 9th day, respectively. In the experimental group, the estradiol peak occurred on the 9th day after the implant (mediam 9 (8–9), in two bitches on the 8th, and five – on the 9th. But the obtained results indicate that in most bitches of the research group, the estradiol peak occurred one day before the LH peak (5/7) and only in 2/7 two days before the LH peak, which is typical for spontaneous estrus, so despite, that,, the peak of estradiol in the experimental group was observed later than in the control group, and ovulation itself occurred faster. Quantitatively, the level of sex hormones was higher in the experimental group, and the sexual cycle was more predictable.

Dynamics of ovarian structures after aplication of Suprelorin® (4.7 mg de-slorelin acetate) implant for estrus induction in bitches

The sexual cycle and ovulation in bitches occur much less often than in other domestic animals, as they are monoestrous. In addition, dogs have spontaneous ovulation and, consequently, a spontaneous luteal phase. This physiology of the sexual cycle in bitches leads to specific difficulties with reproduction. Owners often cannot connect a bitch with a dog in time and, accordingly, get offspring due to the absence of heat or prolonged anestrus. Therefore, the stimulation of the sexual cycle in bitches is gaining more and more interest among animal owners. Understanding the physiology of the sexual cycle and its stages makes it possible to manipulate it safely and without negative consequences for the bitch's body. We recommend using the Suprelorin implant in late anestrus to induce estrus and obtain ovulation in bitches. Implant Suprelorin®, primarily registered for the pharmacological sterilization of dogs and cats, causes estrus at the beginning of its action. This mechanism of action of Deslorelin implants is known as the flare effect due to its stimulating effect on the secretion of gonadotropin (GnRH), which triggers the synthesis of follicle-stimulating and luteinizing hormones from the pituitary gland. Our results showed that the use of the Suprelorin® implant (4.7 mg Deslorelin) is safe for the induction of oestrus in bitches and does not cause side effects. The proposed induction scheme makes it possible to achieve the highest level of initiation of the sexual cycle (hypothalamus-pituitary-gonads), which is as close as possible to the natural sexual cycle regarding the mechanism of action and is safe for the bitch's body. Ultrasound diagnostics occupy an essential place in studying animals with gynecological problems. There are not many studies in bitches that would show the dynamics of ovarian follicles after using the Deslorelin implant. In our studies, ultrasonographic examination of ovarian structures revealed a faster appearance of follicles in the group of bitches treated with the Deslorelin implant (4.7 mg) compared to the control group; at the same time, their size was significantly more extensive, and the ovulated faster. The appearance of anechoic structures on the ovaries with a size of more than 3 mm (mean 3.2 ± 0.1) was detected already on the third day after the introduction of the implant in 3/6 bitches in the experimental group, while in the control group, only on the fifth day (4/6) and on the seventh (2/6) day. Follicle sizes differed statistically between groups from the 9th to the 12th day. In the experimental group, the appearance of follicles was noted earlier than in the control group (starting from the third day); they were significantly more extensive and ovulated on the 14th day, while in the control group, only on the 16th day.

Serum Anti-Müllerian Hormone Levels and Estrous Monitoring of GnRH Agonist Deslorelin-Induced Estrus in Bitches: A Pilot Study.

This study was performed to monitor estrous patterns and, more importantly, changes in anti-Müllerian hormone (AMH) concentrations during the peri-ovulatory period in deslorelin-induced estrous bitches. Healthy anestrous bitches (n = 4) were used. Estrus and ovulation were monitored after deslorelin implantation. Blood samples were collected for analysis of progesterone, estradiol-17ß and AMH concentrations before implantation (day 0) and on days 6, 8, 10, 12, 14, 16, 18, 20 and 22 after implantation. Six days following treatment, all bitches showed estrus signs. Ovulation took place between days 12 and 15. Circulating AMH concentrations varied among bitches from 0.12 to 3.08 ng/mL. However, no significant differences in AMH levels (mean ± SD) were observed between day 0 and days following post-implantation (p > 0.05). There were no significant correlations between AMH and estradiol or AMH and progesterone (p > 0.05). Ultrasonographically, the number of clearly identifiable ovarian follicles was higher before ovulation and the area of ovaries increased after ovulation (p < 0.05). Except for AMH, changes in vaginal cytology, estradiol-17ß and progesterone levels observed in our study were similar to naturally occurring estrus. Large intra- and inter-individual variation in AMH were observed suggesting that AMH is currently not suitable as a canine fertility marker to monitor ovarian response to deslorelin treatment for estrus induction.

Simultaneously administration of cabergoline and PMSG reduces the duration of estrus induction in anestrous bitches.

This study designed a protocol that would combine pregnant mare serum gonadotrophin (PMSG) and cabergoline (CAB) to induce estrus in bitches. Twenty clinically healthy adult and anestrous female dogs were randomly assigned into four groups. The first group was treated with 5.00 μg kg-1 CAB until the onset of proestrus or for 25 days. The second group was treated with 20.00 IU kg-1 PMSG for 5 days and 500 IU human chorionic gonadotropin (hCG) on the 5th day. The third group was treated with 5.00 μg kg-1 CAB for 10 days in combination with 20.00 IU kg-1 PMSG for 5 days and 500 IU hCG on the 10th day. The control group received 1.00 mL of normal saline. Ovarian changes were evaluated ultrasonographically, and the estrus cycle phase was examined by vaginal cytology. Respectively, three, three and four bitches showed clinical signs of proestrus in each treatment group. The intervals between treatment and proestrus for each group were 30.00 ± 3.05, 7.67 ± 1.20 and 13.00 ± 1.20 days, respectively. Two weeks after estrus, the progesterone mean was 14.51 ± 6.24, 19.96 ± 17.16 and 19.12 ± 9.26 ng mL-1 for each group, respectively. In ultrasonography examination, the largest follicle was identified at 15.66 ± 1.33, 11.66 ± 2.40 and 8.75 ± 2.17 days after the onset of proestrus and the largest follicle's size was measured 6.50 ± 0.55, 4.83 ± 1.64 and 7.07 ± 1.49 mm for each group, respectively. Although the combined use of CAB and PMSG reduced the duration of treatment, alteration of the duration or PMSG dosage can be helpful to improve the results.

Melatonin efficacy in comparison with PMSG-HCG program for induction of fertile estruc in Iraqi anestrus bitches

This study was conducted to investigate the ability of melatonin as S/C implant in induction of fertile estrus in bitches, evaluation the treatment with PMSG-HCG in induction of estrus, and monitoring serum concentration of Estrogen and Progesterone before and after treatment, during November (2020) to May (2021) at the College of Veterinary Medicine, University of Baghdad, Baghdad, Iraq. Therefore, 21 local female dogs aged 2-4 years and two fertile males aged 2-5 years were used for natural insemination. Animals were divided equally into 3 groups including 1st group were treated with Melatonin implant S/C 18 mg /animals, 2nd group were treated with PMSG I.M 30 IU / animal for 7 days, in day 8 hCG I.M 100 IU / animal were injected and 3rd group were left as control (without treatment). After that, the bitches were subjected for clinical examination and behaviors investigation, vaginal smears sampling and hormonal evaluation (estrogen and progesterone). The findings of vaginal cytology reveled that parabasal and superficial cells were predominant during the estrus phase. Animal response recorded a significant increase between all groups, with high significance at 1st group comparing with 2nd and 3rd groups, in addition to high significant difference between 2nd and 3rd groups. Duration of response was significantly longer in 3rd group but lowered in 1st group. Pregnancy rate was higher in the 1st and 2nd group. The number of offspring in Iraqi bitches treated with melatonin for estrus induction G1 was 43 pups in G2 it was 29 pups and 7 pups for G3, the sex of offspring recorded 49.37% females and 50.63% males in total. In conclusion, the use of melatonin for induction of fertile estrus in anestrus Iraqi bitches was effective and safe.

Induction of oestrus by administering Inhibin antiserum along with equine chorionic gonadotropin in anoestrous bitches.

As dogs experience oestrus only once or twice a year, it is necessary to establish an effective method of oestrous induction for efficient breeding. In the present study, we evaluated inhibin antiserum (IAS) on oestrous induction in anoestrous females. Bitches were administered 0.5ml/kg IAS or a mixture of 50IU/kg equine chorionic gonadotropin (eCG) and 0.5ml/kg IAS and 500IU human chorionic gonadotropin (hCG) administered 7days after the mixture injection. As a control, bitches received 50IU/kg eCG, with 500IU hCG administered 7days after eCG injection. Blood-tinged vaginal discharge, vulvar swelling, plasma progesterone concentrations and ovarian follicular development were assessed from day 0 to day 14. IAS alone injection did not induce oestrus in bitches at the anoestrous stage. Conversely, vulvar swelling, blood-tinged vaginal discharge and an estimated luteinizing hormone (LH) surge appeared on days 3-7, days 3-6 and days 7-9 after the IAS+eCG mixture injection, respectively, in all five bitches at the anoestrous stage. The average number of developing and ovulated follicles in bitches administered IAS+eCG was 8.8 and 9.6 respectively. A single eCG injection followed by hCG induced oestrous signs, with an average of 8.3 developing follicles and 4.5 ovulated follicles. This study revealed that IAS alone did not induce oestrus, but when IAS was used in combination with eCG, it induced oestrus and promoted a considerable number of ovulations in anoestrous dogs.

Long-term effect of repeated deslorelin acetate treatment in bitches for reproduction control

Long-acting gonadotropin-releasing hormone (GnRH) analogs, which are approved for male dogs and ferrets, have been used off-label to suppress estrus in bitches predisposed to the side effects of spaying. Health data from the past 12 years were evaluated from bitches without progestogen pretreatment that received deslorelin acetate (DA) to suppress estrus for the first time before the age of 4.5 years. The study population included 32 client-owned bitches repeatedly treated with either 4.7 mg or 9.4 mg DA implants for a period of 5.3 ± 3.4 years (range 0.5–11.3 years). Follow-up information concerning immediate side effects of DA occurring within five months after the first DA treatment (n = 23) as well as long-term side effects of sustained gonadal suppression occurring after five months up to three years (n = 2), three years up to five years (n = 2) or more than five years (n = 8) were assessed through a questionnaire. Treatment was considered successful if no major side effects requiring medical treatment occurred, which applied to 26 out of 32 (81 %) bitches. In the six remaining bitches, the following major side effects led to treatment discontinuation: persistent urinary incontinence (n = 1), reoccurring induced heat (n = 1), uterine disease (n = 3) and/or ovarian tumor (n = 3). The bitches recovered completely after surgical spaying and/or DA implant removal. Minor side effects that did not require therapy or affect animal welfare included body weight changes (n = 18), subtle behavioral changes (n = 13), induced heat (n = 12), coat changes (n = 11), pseudocyesis (n = 6), transient urinary incontinence (n = 4), and/or temporary thickening of the uterine wall with little anechogenic content (n = 2). To examine a possible causal relationship between adverse side effects and DA treatment, further studies should compare the frequency of pathologies between groups of GnRH-treated, intact and spayed bitches of similar breeds and ages. Nevertheless, DA application before the age of 4.5 years may be a means of postponing surgical spaying for several years in breeds at high risk for developing urinary incontinence. Before DA is used in bitches, owners should be fully informed regarding possible side effects.

Changes in luteinizing hormone pulse frequency and prolactin levels in bitches in response to estrus induction by cabergoline-its cases where it is delayed to induce estrus.

The effect of estrus induction by cabergoline on gonadotropin and steroid hormone responses was examined in anestrous bitches. Eleven beagles were used in the study; seven were included in the estrus induction group and four were included in the spontaneous estrus group. Cabergoline was orally administered to the estrus induction group at 5 µg/kg once daily for four weeks, or until hemorrhagic discharge was detected. The inter-estrus interval in the estrus induction group was significantly shorter than the previous estrus interval. Bitches that showed proestrus within four weeks of treatment showed increased luteinizing hormone (LH) pulse frequency and, subsequently, increased estradiol (E2) levels. Prolactin (PRL) levels declined promptly after treatment, except in one bitch that did not show proestrus during the cabergoline treatment period. There was a significant correlation between the time to proestrus induction and the reduction in PRL levels. A positive correlation was found between the LH levels two weeks after cabergoline administration and PRL reduction. This study demonstrates that an abrupt reduction in PRL is likely to be important for initiation of estrus in bitches. A reduction in PRL indirectly leads to an increase in LH pulse frequency, which regulates follicular development in bitches. However, if the period from the end of the previous estrus to the cabergoline treatment is short, it may take some time to show proestrus without increasing E2 levels, even if the LH level increases after cabergoline administration.

Seasonality in oestrus and litter size in an assistance dog breeding colony in the United Kingdom

Evidence of seasonality in oestrus in bitches within specialist breeding programmes, such as those for assistance dogs, may support colony management through tailoring the distribution of resources required for breeding...

In this issue – September 2017

In this issue – September 2017

Comparing the Vitex-castus extract and cabergoline effects on estrous induction in female dogs

Cabergoline is used to induce estrus, stop lactation, and induce abortion in small animals. The specific doses of Vitagnus extract have almost identical properties of cabergoline that reduce prolactin and increase the concentration of FSH hormone. The aim of this study was to compare the effect of Vitex agnus-castus extract and cabergoline on prolactin concentration and hormonal changes associated with the onset of estrous cycle in dogs. Twelve healthy adult cyclic female-mix breed dogs were selected and randomly aligned in treatment (6 dogs, Vitagnus extract 1.5 ml daily for 5 weeks, 80–90 mg/ml, PO) and control groups (6 dogs, cabergoline, daily for 5 weeks, 5 μg/kg, PO). Blood sampling and vaginal smears were taken weekly. Serum samples were stored at −20 °C until prolactin, estradiol, and progesterone were measured by ELISA method. Based on vaginal cytology results, four (cabergoline) and three (Vitagnus) dogs were in the estrous phase after 5 weeks of treatment. The average concentration of the prolactin was not changed during 5 weeks and between two groups. There was no significant difference in progesterone and estradiol levels between groups. The changes of estradiol concentration were significant during the 5 weeks (p < 0.01). The mean concentration of this hormone changed significantly between weeks 2 and 3 (p < 0.01), 2 and 5 (p < 0.05), and 3 and 4 (p < 0.05). In conclusion, Vitagnus extract had hormonal effects similar to those of cabergoline for induction of estrus in bitches.

Effect of feeding fermented rice punch on oestrous induction in anoestrous bitches

IntroductionAs a consequence of poor productivity caused by a long anoestrous period, considerable research effort has been given to oestrus induction in dogs to enhance the productivity of young dogs...

183 ULTRASONOGRAPHIC MONITORING OF CANINE OVARIES CLAMPED AT SUBCUTANEOUS SITE AFTER FOLLICLE-STIMULATING HORMONE TREATMENT

Follicle-stimulating hormone (FSH) alone can induce oestrus in bitches, but few reports describe oestrous induction by FSH because pregnant mare serum gonadotrophin (PMSG) has been more successful than FSH for oestrus induction. Real-time ultrasonography can show canine ovarian follicle development, but no method can determine or predict ovulation accurately. Moreover, the ovary location and size complicate imaging. Using ultrasonography, we investigated FSH treatment stimulation of canine ovary follicles, with clamping of the ovaries at a subcutaneous site. Bilateral malacotomy of four 5-year-old Beagle bitches (mean weight 10.3 ± 2.0 kg) with normal oestrous cycles was done using a ventral flank abdominal approach with routine techniques and materials. Each ovary that maintained blood circulation from the suspensory ligament was clamped at a subcutaneous site through muscles of the abdomen. After about six months of bilateral malacotomy, four bitches at the anestrous (two bitches) and diestrous (two bitches) stages of the oestrous cycle were given 0.5 Armour units of FSH twice daily for 5 days. Examinations with ovarian ultrasonography with 7.5 MHz sector transducer, vaginal cytology, and serum concentrations of progesterone and oestradiol were performed daily from the day before the start of FSH treatment through 7 days after FSH treatment. After 15 days of ovarian examination, each bitch received the same FSH treatment twice continually at 15-day intervals. No serosanguineous vaginal discharge was observed during the ovarian examination. The concentrations of progesterone (&lt;0.045–9.6 ng mL–1) and oestradiol (&lt;9.7–81.4 pg mL–1) varied through all treatments. Comparison of the concentrations of progesterone (&lt;0.045–7.6 ng mL–1) and oestradiol (&lt;9.7–30.3 pg mL–1) at the start of FSH administration in each trial revealed that elevated concentrations of both progesterone and oestradiol were observed in the first treatment in 3 bitches. Regarding the second and third treatments, no elevation of concentration was found for progesterone or oestradiol. A new follicular growth was observed in 1 animal after the third FSH treatment, but no follicular growth was found for the other animals. No correlation was found between follicular development and the profile of either progesterone or oestradiol. Ultrasonography proved that FSH stimulation alone cannot induce follicular growth by a single treatment, but it might increase the levels of progesterone and oestradiol, which are not correlated with follicular development and oestrous cycles at the start of FSH treatment.

Dynamics of Vaginal pH in the Bitch during Proestrus and Estrus

The aim of this study was to investigate the dynamics of the pH of vaginal secretions during proestrus and estrus in bitches and its association with the optimal time for insemination and the values of steroid hormones. Sixteen bitches from different breeds and age were included in this investigation. Vaginal pH of each bitch was measured once daily, starting from the first day of vulval bleeding and continuing until the first day of cytological diestrus. In each bitch vaginal smears were taken to determine the onset of estrus and diestrus and blood samples were taken to determine serum progesterone (ng/ml) and estradiol-17β (pg/ml) for detection of the onset of ovulation and their influence on values and the dynamics of vaginal pH. Vaginal pH values in the bitches at the first day of proestrus were between 7.4 and 8.7. This parameter decreased with the progress of the proestrus and the entering into the estrus. Compared to the rest of the estrus, at the time of ovulation and on the next day, a consistent decrease of mean values (6.61±0.15 and 6.63±0.15 respectively) was observed (р<0,01). Individually at the time of ovulation vaginal pH ranged between 6.5 and 6.8. In the days following ovulation a gradual increase in mean values was detected. At the first day of diestrus vaginal pH values were measured significantly higher than those in estrus (р<0,001) and were between 7.4 and 8.3 (7.74±0.26). In our study we found that the vaginal pH values in the bitch are lowest at the time of ovulation, with individual variations and exceptions.

Uterine artery blood flow characteristics assessed during oestrus and the early luteal phase of pregnant and non-pregnant bitches

The aim of this study was to measure uterine artery blood velocity daily using Doppler ultrasonography in 10 young and 10 older clinically normal bitches throughout oestrus.Typical arterial waveforms identified in young bitches were characterised by a systolic peak and subsequent flow throughout diastole, whereas in older bitches, flow was sometimes absent in diastole. For 3days immediately prior to ovulation, at the time of declining plasma oestrogen and increasing progesterone concentrations, resistance index (RI) increased, principally associated with decreased diastolic velocity; in some bitches there was absent late diastolic flow during this time. In older bitches, the waveform appearance was more variable, with absent late and early diastolic flow observed in some cases. Mean RI was higher throughout oestrus for older bitches compared with young bitches, although both groups had a similar 3-day duration increase before ovulation. Nine of the young bitches and five of the older bitches became pregnant; litter size was smaller for the older bitches. Non-pregnant bitches: (1) were significantly older; (2) had fewer waveforms with continuous diastolic flow 2days before ovulation; (3) had lower end diastolic velocity, higher RI and fewer waveforms with continuous diastolic flow 2days after ovulation, and (4) had lower plasma progesterone concentrations 5days after ovulation. These are the first detailed observations of uterine artery blood velocity and waveform appearance throughout oestrus in bitches, and this is the first description of a link between impaired diastolic flow and reduced fertility. Assessment of uterine artery velocity could be useful to promote understanding of physiological mechanisms and could also become an important tool to assess potential infertility.

Pharmacokinetics of eCG and induction of fertile estrus in bitches using eCG followed by hCG

The aim was to design a protocol combining eCG followed by hCG for estrus induction in the bitch. In Experiment 1, three ovariohysterectomized bitches received 10 000 IU of eCG iv, and 15 days later 10 000 IU of eCG im. Blood samples were taken up to 144 h after each injection to measure eCG concentrations. In Experiment 2, 25 healthy, intact late anestrous bitches were assigned to one of five doses of eCG (5, 10, 15, 20, 44, or 50 IU/kg eCG im; [TRT5-TRT50]). Sexual behavior (SB), clinical signs of estrus (CSE) and vaginal cytology (VC) samples were obtained and scored before eCG administration and every other day until onset of estrus, or for 14 days. In Experiment 3, intact late anestrous bitches were assigned to a treatment group (TRT; n = 16) and received eCG (50 IU/kg im) followed by hCG (500 IU im) 7 days later; or to a placebo group (PLA; n = 8) where they received 1 mL saline solution im. All bitches that were induced in estrus were mated or AI with fresh semen. In Experiment 1, maximum observed concentration (Cmax) eCG were similar between im and iv routes (6.1 ± 0.9 vs. 8.6 ± 0.5 IU/mL, P > 0.08), whereas time for maximum observed concentration (Tmax.) was longer for im compared to iv routes (17.5 ± 0.5 vs. 11.6 ± 0.3 h, P < 0.01). The area under the curve (AUC) was similar for im and iv routes (P > 0.48), and eCG was detectable in serum for at least 144 h for both routes. In Experiment 2, 3 days or 3 to 5 days after treatment, all bitches in TRT50 had higher scores compared to TRT5-44 animals (P < 0.01). In TRT50, the mean interval from treatment to estrus was 4.0 ± 0.4 days. In Experiment 3, the mean interval from treatment to estrus was shorter in the TRT group compared to the PLA group (4.1 ± 3.3 vs. 68.5 ± 4.4 days, P < 0.01). The previous interestrus interval was similar for TRT and PLA groups (199.6 ± 7.2 vs. 197.5 ± 10.2 days), but the new interestrus interval was shorter for the TRT compared to the PLA group (164.0 ± 7.2 vs. 212.2 ± 10.2 days; treatment by interval interaction, P < 0.007). Serum P4 concentrations increased on the first day of cytologic diestrus after treatment in bitches in TRT (0.7 ± 0.3 vs. 22.8 ± 4.2 ng/mL; P < 0.01); but did not change in PLA (P > 0.84). Ninety-four percent of animals were bred (15/16; AI, n = 7; natural mating, n = 8), and 80% (12/15) became pregnant. None of the bitches had any side effects from the eCG and hCG therapy. We concluded that 50 IU/kg of eCG combined 7 days later with 500 IU of hCG was effective to induce normal and fertile estrus in bitches at 164 days post estrus, with an 80% pregnancy rate, with no side effects, and with a reduction of 48 days of the interestrus interval.

Comparison of the use of cabergoline and gonadotrophin to treat primary and secondary anoestrus in bitches

To determine the efficacy and reliability of cabergoline and pregnant mare's serum gonadotrophin (PMSG) for induction of oestrus in bitches with primary or secondary anoestrus. We studied 39 healthy bitches of various breeds aged 2-6 years and in primary or secondary anoestrus: 20 bitches were administered 5 µg/kg/day cabergoline orally until day 2 after the onset of pro-oestrus or for a maximum of 42 days, and 19 bitches were administered 20 IU/kg/day PMSG intramuscularly for 5 consecutive days, followed by an additional single injection of 25 IU/kg of human chorionic gonadotrophin on the fifth day. The rates of oestrus induction in the primary and secondary anoestrous bitches treated with cabergoline and PMSG were found to be similar. Pregnancy and whelping rates in the cabergoline group were statistically different from the rates in the PMSG group (P < 0.001). Cabergoline is more effective and reliable for the induction of a fertile oestrus in bitches with primary or secondary anoestrous.

Seasonal effects on appearance of pyometra in bitches

Pyometra is one of the most frequent and very grave diseases of the reproductive system in bitches. It occurs around 30 to 60 days following the latest oestrus in bitches that are not pregnant. Bitches older than 5 years have a significantly higher predisposition for this disease than younger bitches. There are also differences between certain breeds in the age at which this disease is manifested in a bitch. The objective of this work was to establish whether the seasons of the year also affect the incidence of pyometra in bitches in the territory of Vojvodina. The occurrence of pyometra was examined in a total of 318 bitches over a course of two years and during the different seasons of the year. It was established that a statistically significantly higher number of bitches (P,05) fall ill with this disease during the seasons September-November (31%) and December-February (28%) than during the seasons March-May (19%) and June-August (22%). The obtained data can serve to secure better prevention and timely diagnoses of pyometra in bitches.

Induction of fertile oestrus in the bitch using Deslorelin, a GnRH agonist

Oestrus induction in various canine breeds was attempted in 32 bitches. A group of 8 bitches were treated 80–160 d following their previous oestrus (G1) whereas a second group of 24 bitches (G2) were implanted 200–590 d following their previous oestrus. The treatment for each bitch consisted in one Deslorelin implant (Suprelorin®4,7mg, Virbac, France), inserted subcutaneously in the post-umbilical region. Ovulation, pregnancy rate and litter size were recorded. All bitches came in heat 4.3 ± 1.4 d after implantation (2–7 d). Ovulation was reported in 62.5% in G1 and 87.5% in G2. One bitch refused mating and since no AI was performed, she was not considered for further analysis. Pregnancy was obtained in 25% in G1 versus 78.3% in G2. Mean litter size was 6.7 ± 3.5 puppies (1–14). Luteal failure was suspected in 3 bitches, two that remained non-pregnant and one which aborted 58 d post-ovulation since the owner refused progesterone supplementation. Deslorelin implants can therefore be considered as a valuable alternative to induce fertile oestrus in bitches in anoestrus. Follow-up of the luteal phase is recommended, since some bitches might encounter luteal failure.